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A highly sensitive and selective fluorescent probe utilizing B and S co-doped graphene quantum dots (BS-GQDs) has been created for detecting ibuprofen. The co-doping strategy effectively modulated the electronic structure and surface properties of GQDs, resulting in enhanced fluorescence quantum yield and sensing performance. The BS-GQDs exhibited strong fluorescence quenching upon interaction with ibuprofen, which was attributed to the formation of a ground-state complex and electron transfer from BS-GQDs to ibuprofen. Under optimal conditions, the sensor exhibited a broad linear range, a low detection limit, and outstanding selectivity for ibuprofen compared to other common medications and interferents. The practical utility of the sensor was validated through the successful identification of ibuprofen in spiked urine and serum samples, achieving high recovery rates and accuracy. The BS-GQDs-based fluorescent sensor provides a promising platform for sensitive, rapid, and reliable monitoring of ibuprofen in pharmaceutical and biomedical fields.

Akyl urea derivatives, either symmetrical or unsymmetrical in nature possessing a free N-H or N-alkyl moieties in the molecular framework of urea governs the excited state properties of acridinedione dye (ADR1) which is a resorcinol-based derivative. Fluorescence enhancement (FE) of ADR1 dye is observed on the addition of unsymmetrical urea derivatives, whereas a decrease in the fluorescence intensity resulted upon the addition of symmetrical urea derivatives. The nature of the urea derivatives controls the suppression of photoinduced electron transfer (PET) via space, which is the cause of the FE. FQ results from the donor and acceptor moieties of ADR1 dye promoting the PET process. Urea (U), symmetrical and unsymmetrical urea derivatives (except Tetramethyl urea (TMU)) results no significant shift of the localized excited (LE) state emission of ADR1 dye. Studies of the ADR1 dye’s fluorescence lifetime in the presence of urea compounds show a significant increase in lifetime. This phenomenon is explained by a significant difference in the hydrogen-bonding (HB) pattern, which causes variation in the microenvironment created by the solute molecules in the aqueous phase. Both the hydrophobic effects of the alkyl group substituents in the urea molecular framework and the HB interactions between the solute and solvent influence the excited state features of ADR1 dye. Further, the role of urea derivatives and ADR1 dye (both are considered as competitive guest molecules) energetics and molecular interactions were studied in the presence of host molecule, Human Serum Albumin (HSA). The binding energy (BE) and several bimolecular interactions driven by urea derivatives in the presence of ADR1-HSA complex in comparison with that of urea derivatives-HSA complex were investigated by molecular docking (Mol.Doc) methodology. Incorporating theoretical research along with steady state and time-resolved fluorescence investigations proved to be an effective method to evaluate the interactions of competing solutes comprising both hydrophobic and HB functional groups.

Four copper (II) complexes [Cu(L1)2] (1), [Cu(L2)2] (2), [Cu(L3)2] (3) and [Cu(L4)2] (4) with azo linked O,O donar ligands viz 2-hydroxy-5 (phenyldiazenyl)benzaldehyde (HL1), 1-(2-hydroxy-5-(phenyldiazenyl)phenyl)ethanone (HL2), 2-Hydroxy-5-p-tolylazo-benzaldehyde (HL3), 1-(2-Hydroxy-5-p-tolylazo-phenyl)-ethanone (HL4) have been prepared and characterized by different spectroscopy methods and published earlier by our research group. We investigated the interaction of Human Serum Albumin (HSA) with complexes 1–4 under physiological condition in phosphate buffer solution at pH 7.4 using various spectroscopic techniques. The fluorescence titration spectrum disclosed that the complex 1–4 quench the intrinsic fluorescence of HSA robustly through a static quenching mechanism. Binding constants (Kb) and the number of binding sites (n ≈ 1) were evaluated using modified Stern–Volmer equations. Binding constants were found to be 1.9, 6.6, 0.99 and 1.2x 105 (M−1) for complex 1, 2, 3 and 4 respectively. The CD spectra of free HSA and HSA with complexes 1–4 showed that the complexes have negligibleimpact on the secondary structure of HSA as theyremain helical even after the addition of complexes. Molecular docking study was performed to analyse the binding mode of complexes 1-4with HSA. Docking study revealed that hydrophobic and Vander waals interactions were considered to be the main interaction forces involved in the binding of HSA with complexes 1–4.

A straightforward, reliable, and cost-effective spectrofluorimetric approach has been established for the analysis of baloxavir marboxil (BXM) in raw material, tablets, as well as spiked human plasma. The approach relies on BXM's quenching impact on acetoxymercuric fluorescein (AMF) fluorescence intensity. To improve the reaction, factors such as AMF's concentration, solution's pH, diluting solvents, and reaction time were examined and optimized. Linearity, range, accuracy, precision, LOD, and LOQ were all verified in compliance with ICH criteria. The concentration range was shown to be linear between 0.2 and 2 μg/mL. The technique was effectively utilized for BXM analysis in both its tablet as well as spiked human plasma, with mean % recoveries of 101 ± 0.36 and 98.77 ± 0.65, respectively. Two assessment models (AGREE and RGB-12) were used to compare the proposed process's greenness and sustainability to four previously published chromatographic techniques. Higher green and sustainability qualities were declared by the suggested approach than by earlier ones.

The mini review focuses on the work carried out in our laboratory over the last two and a half decades to unravel various facets of photoinduced processes, viz. photoinduced electron transfer (PET), excited state proton transfer, energy transfer etc., using fluorescence spectroscopy and imaging. We have demonstrated that PET is manifested by formation of exciplex and that its parent spin state is authenticated by observing steady-state fluorescence in presence of magnetic field, which is quite a non-conventional set-up. It is observed that dielectric constant of the medium governs the magnetic field effect. We have synthesized and explored fluorophores which act as sensors for hydrogen bonds and protic media. Our group has studied the protonation equilibrium of Acridine, which is a good fluorophore in various confined media and observed the perturbation of this equilibrium in presence of DNA bases using steady-state and time-resolved fluorescence techniques. Excimer formation of 9-Aminoacridine Hydrochloride Hydrate (9AA), another strong fluorophore, has been investigated in several solvent matrices and photoinduced interactions of 9AA with amines and viologens are studied. Further, we have utilized fluorescence upconversion technique to segregate direct and diffusion-controlled electron transfer within picosecond-femtosecond time domain. Then attempts have been made to study DNA-ligand and protein-ligand interactions comprehensively, utilizing different techniques of fluorescence spectroscopy. Furthermore, we have synthesized fluorescent carbon dots and have made an endeavor to find their fruitful biological significance. We have also synthesized riboflavin (Rf)-gold nano-assemblies (RfS@AuNPs) by covalently attaching thiolated Rf to gold nanoparticles (AuNPs) and have observed that these RfS@AuNPs accumulate in the nucleus of cancer cells, leading to plasma membrane blebbing and binucleated apoptotic bodies, consistent with activation of apoptosis. Finally, some very recent examples as well as the future prospect of fluorescence spectroscopy have been discussed.

Doxorubicin (DOX) interaction with 2D boron nitride (BN) nanoparticles was studied experimentally and theoretically. The BN nanoparticles, namely nanoflakes, were obtained by direct liquid-phase exfoliation via preliminary stratification in a planetary ball mill from massive hexagonal BN. 2D BN nanoparticles and DOX/BN composites were characterized using visible steady-state, time-resolved fluorescence, FTIR and Raman spectroscopy, Coherent Anti-Stokes Raman Scattering (CARS) microscopy and density functional theory (DFT). The BN nanoflakes from 2 to 3 layers up to hundred nm in lateral direction possessed crystalline properties that formed the DOX/BN composites with fluorescence in the range of 520–750 nm that can be used in DOX detecting. The calculations revealed a notable electron transfer between the BN monolayer and the DOX molecule, which, however, is partly offset by the redistribution of charge within the monolayer. The energy of interaction of the BN with DOX was estimated as 1.96 eV, indicating that the DOX/BN composite formation is an exothermic process. The Fluorescence quenching of DOX/BN occurs with increased BN nanoparticle concentration. The optimal concentration for composite formation was chosen. In CARS imaging of the Lewis lung carcinoma cells after treatment with DOX/BN, brightly luminous points are observed inside the cells, indicating the accumulation of DOX/BN composites that can be used in bioimaging and theranostics.

In this investigation, we employed an oxidation–reduction method to synthesize selenium nanoparticles (SeNPs) and applied a coating of sweet corn polysaccharides (SCP) to confer stability upon the SeNPs. We characterized the SCP-coated SeNPs using dynamic light scattering, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffractometry, Ultraviolet–visible spectrum, and Fourier transform infrared spectroscopy. Our findings revealed that the resulting SCP-coated SeNPs possessed an average particle size of 127.82 nm and exhibited superior inhibitory effects on α-amylase and α-glucosidase when compared to SCP in vitro experiments. The inhibition kinetics and fluorescence quenching mechanism demonstrated that the inhibitory action of SCP-coated SeNPs on both enzymes was of a competitive nature, predominantly mediated by hydrophobic interactions and hydrogen bonding. In in vivo experiments, SCP-coated SeNPs demonstrated promising hypoglycemic, hypolipidemic, and antioxidant properties in type 2 diabetes (T2DM) mice. Collectively, our study underscores the remarkable potential of SCP-coated SeNPs in ameliorating T2DM.

The binding of ligands to G-quadruplex (G4) structures at the ends of human telomeric DNA induces thermal stabilization, which interferes with telomere maintenance by disrupting the association of telomeres with the telomerase enzyme—an important marker for cancer. Understanding the binding mode of the ligand-G quadruplex DNA complex is imperative for evaluating the relative efficacy and specificity of their interaction. We focused on the interaction of 1,5-Bis(3-piperidino propionamido) anthracene-9,10-dione with human telomeric DNA sequences using surface plasmon resonance, absorbance, fluorescence (steady-state and lifetime), and circular dichroism spectroscopy techniques. The ligand binding with HTel22 (Kb = 8.4 × 105 M−1) induced cell toxicity with an IC50 value of ∼ 8.64 µM in MCF-7 cancer cell lines. Significant hypochromism (59 %), fluorescence quenching (97 %), no change in fluorescence lifetime and absence of induced Circular Dichroism (CD) band upon addition of G4 DNA to ligand, suggest a groove/external binding mode. CD spectral changes reflect rearrangement in parallel and antiparallel strands to accommodate the ligand. Docking results reveal specific short contacts of the ligand's side chain, including 9CO, 13N, 14NH, and 11CO, with the grooves of the G4 DNA, without making any contact with the loops, favoring an energetically more favorable conformation. Thermal denaturation profiles, obtained by Differential Scanning Calorimetry and CD, show the stabilization of wHTel26 and HTel22 G4 DNA in K+ and Na+ rich solutions by 21.2 and 17.6 °C, respectively, which may restrict the access of telomerase to telomeres. The findings indicate the potential of modifying anthraquinone substituent groups for therapeutic applications.

We reported the fluorescence sensor of carbon dots (CDs) synthesized for the highly sensitive and selective detection of bilirubin in human urine. High-resolution transmission electron microscopy (HRTEM) images showed that the CDs have a spherical shape with a mean particle size of 2.6 nm. The CDs showed the fluorescent emission, which peaked at the wavelength of 511 nm under the excitation wavelength of 435 nm. The CDs’ emission intensity reduced with increasing the bilirubin concentration, which was ascribed to the strong inner filter effect (IFE). The excellent spectral match between the bilirubin absorbance and the CDs excitation allowed the fluorescence sensor to be markedly specific only to the presence of bilirubin, permitting the identification of bilirubin even in the presence of other potentially interfering elements. The fluorescence sensor displayed a good linear response to the bilirubin concentration in the wide range of 3.5–45.5 μM with a limit of detection (LOD) of 34 nM, being the remarkably low level even though CDs were synthesized in a facile way without doping. Moreover, this sensing strategy permitted us to quantify bilirubin in the clinical (real) specimen with a good recovery of 95.3–96.8%, indicating a great potential candidate for a cost-effective bilirubin sensing platform in a biomedical application.

A novel nanoprobe based on S,O-doped carbon nitride quantum dots (S,O-CNQDs) was designed and synthesized. The as-prepared S,O-CNQDs exhibits good biocompatibility and strong fluorescence at excitation 360 nm. It is found that folic acid (FA) could efficiently quench the fluorescence of S,O-CNQDs. The obtained S,O-CNQDs is capable of acting as a sensitive and selective probe for FA detection in the range 5.0–83.3 μM with a detection limit of 90 nM. The as-prepared probe has been successfully utilized for the detection of FA in various real samples with satisfactory recoveries (98.8–107 %) and small relative standard deviation (

ABSTRACT: Escherichia coli O157:H7 is a type of hazardous bacteria in the field of food safety. A sensitive and effective method is urgently needed to detect it, avoiding enormous harm for the human health. In this study, we synthesized stable Ag+-doped gold nanoclusters (Ag-AuNC) with a fluorescence intensity 4.8 times stronger than that of AuNC. It was further demonstrated that Ag0 existing in the AuNC core and a fraction of Ag+ anchored on the AuNC shell eliminated the surface defects and improved the luminescent properties of AuNC. A combination of I2 and I− was used to quench fluorescence-enhanced Ag-AuNC, which was first applied in ELISA for detecting E. coli O157:H7 to improve the sensitivity. In the presence of E. coli O157:H7, the biotinylated anti-E. coli O157:H7 mAb and streptavidin-alkaline phosphatase would be immobilized and catalyze l-ascorbic acid 2-phosphate sesquimagnesium salt hydrate to produce ascorbic acid. After addition of KIO3, I2/I− were generated. The I2 could trigger oxidative etching of Ag-AuNC and I− could combine with Ag+ to decrease the Ag+ concentration of Ag-AuNC, which resulted in fluorescence quenching of Ag-AuNC. Under optimal conditions, the linear range of I2/I−-mediated fluorescence quenching of Ag-AuNC-based immunoassay for detecting E. coli O157:H7 was 3.3 × 103 to 106 cfu/mL, with a detection limit of 9.2 × 102 cfu/mL, 10.7-fold lower than that of the traditional ELISA. The proposed immunoassay exhibits excellent sensitivity, specificity, recovery, and accuracy, which is useful for quantitative detection of E. coli O157:H7 in food safety.

Xanthine oxidase (XO) has been well-recognized as a key enzyme in the pathogenesis of hyperuricemia. In this study, Chuanxiong Rhizome, a tonic food widely consumed in China, was found to inhibit XO activity. The potential XO inhibitory ingredients were screened by UPLC-ZenoTOF system and bioactivity assays. Coniferyl ferulate (CF), a main constitute of Chuanxiong Rhizome, was identified as a potent XO inhibitor with an IC50 value (1.97 ± 0.11 μM) lower than that of allopurinol (2.49 ± 0.07 μM). Enzyme-kinetic assays showed that CF reversibly inhibited XO in an uncompetitive manner. And hydrogen bonds played crucial roles on the binding interaction according to the fluorescence titration and molecular docking. Moreover, the combination of CF with allopurinol exhibited a synergistic inhibitory effect on XO. Our results revealed for the first time the XO inhibitory effect of CF from Chuanxiong Rhizome, which shed light on its potential application for developing anti-hyperuricemia agents.

The digestive enzyme of plant are generally α-amylase. They functions enzyme that breakdown starch into maltose and sugars. This happens in the endosperm of the seed. Due to pollutants, this process get happened one of emergent xenobiotics are micro and nano plastics. This study involves the interaction 100 nm size of polystyrene nano plastic (PSNPs) on α-amylase. The hyperchromism of α-amylase – PSNPs conjugate’s revealed that ground-state complex in a microenvironment. Fluorescence quenching happened when the concentration of PSNPs was increased. The Stern Volmer plot revealed binding constant (Ka) was 1.904 × 1019 M-1. S-1 while the quenching constant (Kq) was 1.036 × 1011 M-1, the blue shift of the peak showed static quenching. The binding constant was KA = 4.2 × 1012, the number of binding site on PSNPs for α-amylase was n = 1.12. The synchronous result showed a gradual reduction in the intensity of Trp residues because when the α-amylase interacts with PSNPs short-range π-π interaction happens around the Trp163 residues. The enzyme activity of α-amylase by 44 % and its IC50 value was found to be 100 µg/mL. The enzyme kinetics (Vmax) analysis showed the type of inhibition with and without PSNPs Vmax 769 and Vmax 303 µg/mL/min, uncompetitive inhibition respectively. The effect of PSNPs on the enzymatic activity of α-amylase showed structural alterations of the protein. Therefore the in vitro and in silico studies were shown evidence of interaction between α-amylase and PSNPs leads to conformational structural changes in α-amylase.

The present study explores the kitchen waste okra peels derived synthesis of nitrogen doped carbon dots (N-CDs) via simple carbonization followed by reflux method. The synthesized N-CDs was characterized using, TEM, XPS, FTIR, XRD, Raman, UV-Visible and Fluorescence Spectroscopy. The N-CDs emits bright blue emission at 420 nm with 12 % of quantum yield as well as it follows excitation dependent emission. Further, the N-CDs were employed as a fluorescence sensor for detection of hazardous metal ions and nitro compounds. Among various metal ions and nitro compounds, the N-CDs shows fluorescence quenching response towards Cr 6+ , and Mn 7+ metal ions as well as 4-nitroaniline (4-NA) and picric acid (PA) with significant hypsochromic and bathochromic shift for Mn 7+ , 4-NA and PA respectively. The developed fluorescent probe shows relatively low limit of detection (LOD) of 1.46 µg/mL, 1.05 µg/mL, 2.1 µg/mL and 2.2 µg/mL for the above analytes respectively. The N-CDs did not show any significant interference with coexisting ions and successfully applied for real water sample analysis. In addition, circular economy approach was employed for adsorption of dyes by reactivating leftover waste carbon residue which was obtained after reflux. Thus, the kitchen waste valorization and circular economy approach based N-CDs have potential applications in the field of detection of emerging pollutants, and environmental remediation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Changes in the neurotransmitters are indications for several diseases. Several sensors were reported for monitoring dopamine (DA), but the simple and accurate DA detection in biological samples still faces many challenges. The research proposal aims to develop an optical sensor for detecting neurotransmitters based on luminescence emission spectra in different biological samples. Carbon dots (CDs) were fabricated based on a green synthesis route. Then the prepared CDs were decorated with varying concentrations of gold nanoparticles (Au NPs). The synthesis process was optimized, and the obtained CDs/Au NPs nanocomposites were applied as neurotransmitters' optical nanosensors. The optical nanosensor approach provides easy and sensitive multiplex analysis. A wide range of neurotransmitters was monitored. The developed sensor's sensitivity, selectivity, and reproducibility were investigated. Au NPs act as CDs' stabilizers, enhancing the emission effect, and scaffolds for binding DA with CDs' surface. DA moieties bind to CDs through the interaction between the DA-NH 2 groups and Au NPS. Due to electron transfer, the bonding of DA molecules leads to fluorescence quenching of AuNPs/CDs. The Au-CDs-based DA fluorescence showed high sensitivity with adetection limit, and limit quantification of 2.04 nM and 6.18 nM, respectively. Furthermore, the selectivity of the sensor was investigated in the presence of glucose, uric acid (UA), and ascorbic acid (AA), which showed no interference effect at 10 times higher concentrations. Moreover, the proposed sensor has been successfully utilized for DA detection in human serum samples with a high recovery efficiency between 98.83 % and 103.5 %., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Vilazodone is a recently approved antidepressant medicine used for treating major depressive disorder. A simple, extremely sensitive, accurate and green spectrofluorimetric method was constructed for its determination through formation of ion-pair complex with erythrosine B. The formation of ion-pair complex lowers the dye's native fluorescence emission measured at 552 nm (λ ex = 530 nm). In terms of analysis, the system's parameters for producing the vilazodone-erythrosine B complex have been optimized. The reaction was carried out in Teorell-Stenhagen buffering solution (pH 4.6). The fluorescence emission intensity of the dye decreased linearly in the range of 20 - 600 ng mL -1 and the correlation coefficient was 0.9999. The quantitation and detection limit values were 18.5 and 6.1 ng mL -1 , respectively. The proposed strategy has been validated according to the ICH criteria. The proposed technique was thoroughly employed for evaluating vilazodone in raw material and pharmaceutical tablet dosage form. Furthermore, it was also successfully used for content uniformity testing. Lastly, using four advanced tools namely the Eco-Scale, the National Environmental Method Index (NEMI), the Green Analytical Procedure Index (GAPI), and the Analytical Greenness metric approach (AGREE), the greenness of the established technique was evaluated., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Halophenols are toxic and persistent pollutants in water environments which poses harm to various organisms. Due to their high stability and long residence time, ultraviolet radiation, heavy metals and oxidizing agents have been largely adopted on treating these compounds. However, these treatment methods could pose toxicity or hazardous risks to the marine environment and plant operators. In this study, a water-soluble porphyrin photocatalyst was synthesized and introduced for halophenol treatment using UV-free LED white light. The porphyrin catalyst is a macrocyclic ring consisting of pyrroles linked with methine bridges, the highly conjugated ring provided the superior functionality of visible light absorption. Surprisingly, over 99 % degradation of halophenols and over 90 % dehalogenation have been achieved without metal chelation, even higher than those of transition metal porphyrins with inclusion of Fe 3+ , Zn 2+ , Cu 2+ , Co 2+ , Ni 2+ , and Mn 2+ . Ring-opening reactions were confirmed with the formation of carboxylic acids; dicarboxylic acids like acrylic acid, and malonic acid; while fumaric acid was the main product. Total organic carbon results indicated no CO 2 produced during the reaction. Triplet absorbance and scavenger studies also indicated that singlet oxygen and conduction band electrons are the main radical species for halophenol degradation. The 100-fold singlet emission quenching over triplet absorption quenching indicated that the excited electrons tend to be transferred via singlet state. This concept brings along new approaches detoxifying halophenol-related wastewater without UV, metals and other additives, which is more environmentally-friendly and sheds light to the conversion of toxic materials into useful chemical precursors., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The interaction of biomacromolecules with each other or with the ligands is essential for biological activity. In this context, the molecular recognition of bovine serum albumin (BSA) with 4-(Benzo[1,3]dioxol-5-yloxymethyl)-7-hydroxy-chromen-2-one (4BHC) is explored using multispectroscopic and computational techniques. UV-Vis spectroscopy helped in predicting the conformational variations in BSA. Using fluorescence spectroscopy, the quenching behaviour of the fluorophore upon interaction with the ligand is examined, which is found to be a static type of quenching; fluorescence lifetime studies further verify this. The binding constant is discovered to be in the range of 10 4 M -1 , which indicates the moderate type of association that results in reversible binding, where the transport and release of ligands in the target tissue takes place. Fourier-transform infrared spectroscopy (FT-IR) measurements validate the secondary structure conformational changes of BSA after complexing with 4BHC. The thermodynamic factors obtained through temperature-dependent fluorescence studies suggest that the dominant kind of interaction force is hydrophobic in nature, and the interaction process is spontaneous. The alterations in the surrounding microenvironment of the binding site and conformational shifts in the structure of the protein are studied through 3D fluorescence and synchronous fluorescence studies. Molecular docking and molecular dynamics (MD) simulations agree with experimental results and explain the structural stability throughout the discussion. The outcomes might have possible applications in the field of pharmacodynamics and pharmacokinetics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This study employs an optimized and environmentally friendly method to extract and purify chondroitin sulfate (CS) from bovine nasal cartilage using enzymatic hydrolysis, ethanol precipitation, and DEAE Sepharose Fast Flow column chromatography. The extracted CS, representing 44.67 % ± 0.0016 of the cartilage, has a molecular weight of 7.62 kDa. Characterization through UV, FT-IR, NMR spectroscopy, and 2-aminoacridone derivatization HPLC revealed a high content of sulfated disaccharides, particularly ΔDi4S (73.59 %) and ΔDi6S (20.61 %). Interaction studies with bovine serum albumin (BSA) using fluorescence spectroscopy and molecular docking confirmed a high-affinity, static quenching interaction with a single binding site, primarily mediated by van der Waals forces and hydrogen bonding. The interaction did not significantly alter the polarity or hydrophobicity of BSA aromatic amino acids. These findings provide a strong foundation for exploring the application of CS in tissue engineering and drug delivery systems, leveraging its unique interaction with BSA for targeted delivery and enhanced efficacy., Competing Interests: Declaration of competing interest The materials discussed herein have not been published elsewhere before, and the manuscript has not been submitted to any other journals., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Perovskite materials consisting of dual-phase CsPbBr3–CsPb2Br5 coated with (3-Aminopropyl) tiethoxysilane (APTES) were synthesized using the ligand-assisted reprecipitation method at 0 °C. The photoluminescence intensity of CsPbBr3–CsPb2Br5 coated with APTES was 1.2 times higher than that of uncoated CsPbBr3–CsPb2Br5. Furthermore, the photoluminescence intensity of the synthesized perovskite materials remained at 95% of the initial emission intensity after 10 days in ethanol. Fe3+ ions were found to exert strong fluorescence quenching on the prepared CsPbBr3–CsPb2Br5 coated with APTES, and that effect originated from the decomposition of CsPbBr3 to CsPb2Br5. The quenching behavior was related to the adsorption between Fe3+ ions and APTES. The response time for detecting Fe3+ was only 8 s at 40 °C, indicating a high detection speed. Effective detection ranges for Fe3+ ions were achieved at concentrations between 10−2 and 10−5 M, and the detection limit was reached at 10−5 M with 89.6% of the initial emission intensity. These results revealed that the detection of Fe3+ ions using CsPbBr3–CsPb2Br5 coated with APTES exhibited high sensitivity as well as a short response time in a wide detecting range.

Highly stable zinc-based luminescent metal-organic framework (LMOF) [(Zn2-(NDC)2(bpy)·Gx) where NDC-2,6-naphthalene dicarboxylic acid, bpy - 4,4' bipyridine, and G - guest solvent molecules] is synthesized via solvothermal method at different synthesizing temperatures (120, 150 and 180∘C) for the detection of nitro-aromatics. Sample structure and presence of ligands is confirmed by X-ray diffraction and FTIR measurements, respectively. The photoluminescence properties of synthesized LMOF samples show the strong emission intensity in ethanol at 376 nm when it is excited at 240 nm. The detection limit is calculated using fluorescence quenching for the various nitro-analytes (2,4-DNP, 2-Nitrotoulene, 4-Nitrophenol, and Nitrobenzene) revealed that it is least for the sample synthesized at 150∘C with the maximum percentage in fluorescence decay. The thermal stability of as-synthesized samples is analysed using thermogravimetry analysis (TGA) which reveals that sample synthesized at 150∘C is the most stable sample. The TGA analysis also shows that on further heating from 526∘C to 980∘C decomposition of zinc metal and formation of zinc oxide takes place. FE-SEM confirms the cuboidal morphology with an average particle size of 12.62 nm, corroborated by the TEM analysis. The fluorescence quenching mechanism is explained on the basis of dipole-dipole and π-stacked interactions between the MOF and nitro-aromatics that play a prominent role in the sensing of nitro-analytes. Synthesized MOF samples show excellent recyclability in fluorescence quenching even after the fourth cycle, i.e. more than 95% and is sensitive to detect nitro-aromatics even upto 0.284 µM, and the results can generalize the explosive sensor technology and sensing various nitro-based pollutants.

4-Hydroxybenzoic acids (4-HBA) and 4-hydroxy-3-methoxybenzoic acid (Vanillic acid, VA) have exhibited several pharmacological activities. Generally, the biological activities of compounds are highly involved in the interaction between protein and compounds in blood plasma. The objective was to investigate the interaction of 4-HBA or VA with human serum albumin (HSA) and their anti-proliferation properties on doxorubicin-sensitive K562 and doxorubicin-resistant K562/Dox leukemia cells. The protein binding of 4-HBA or VA to HSA was investigated using fluorescence quenching at temperatures of 298 and 310 Kelvin (K) under the pH of 6.0, 7.4, and 8.0 conditions. The effect of 4-HBA and VA on anti-proliferation was also studied on doxorubicin-sensitive K562 and doxorubicin-resistant K562/Dox leukemia cells using resazurin assay. The results showed that 4-HBA and VA could interact with HSA. The fluorescence quenching process in HSA-4-HBA system might be attributed to static quenching mechanism. In contrast, a dynamic quenching mechanism might be mainly involved in the fluorescence quenching process in the HSA-VA system. Thermodynamic data suggested that the spontaneous interaction between HSA and 4-HBA or VA had occurred in the system and it also indicated that hydrogen bonds and Van der Waals forces contributed to the binding of HSA to 4-HBA or VA. In addition, 4-HBA and VA decreased K562 and K562/Dox cells viability in a dose- and time-dependence manner. In conclusions, the 4-HBA and VA could interact with HSA. In addition, the 4-HBA and VA decreased in cell viability for both doxorubicin-sensitive K562 and doxorubicin-resistant K562/Dox leukemia cells in a dose- and time-dependence manner. Therefore, these current studies could provide useful information about the nature of 4-HBA or VA binding to protein HSA and their anticancer activities in both of these types of leukemia cells. The cell death mechanisms should be investigated through future study.

Selective response is the key index to evaluate the performance of polymeric carbon nitride (PCN)-based heavy metal ion fluorescence sensors. Herein, to explore the role of cyano groups on selectivity, four kinds of PCN, including PCN-Cl, PCN-Ac, PCN-B and PCN-K were prepared by the molten salt method of sodium chloride and sodium acetate, the reduction method of sodium borohydride and the etching method of potassium hydroxide, respectively. These PCNs exhibited different surface cyano characteristics, but all of them had significant blue emission under ultraviolet excitation. It is proved that the assistant of sodium chloride or potassium hydroxide is an effective method to prepare PCNs with abundant surface cyano group. A series of fluorescence quenching experiments of metal ions showed that the cyano-rich degree of PCN is closely related to its selective response to mercury (II) ions. PCN-Cl and PCN-K emerged good selective quenching of mercury (II) ions, which may be related to the soft acid-soft base strong interaction between mercury (II) ions and cyano groups. Both PCN-Cl and PCN-K fluorescent probes for mercury (II) ions had a linear range of 5 ∼ 50 μmol L -1 , and PCN-Cl exhibited a lower detection limit of 0.38 μmol L -1 . This work confirmed the selective fluorescence response of cyano-rich PCN to mercury (II) ions, proposed the mechanism of selective fluorescence quenching response of mercury (II) ions, and provided a new idea for the design of efficient and accurate PCN-based fluorescence probes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This contribution aims to design and validate a new green, cheap, and fast approach for determining the anti-GERD drug pantoprazole in different matrices. New S and N-doped carbon nanomaterials (S,N-CNMs) have been prepared via microwave irradiation of a mixture of widely available household sources. Remarkably, the utilization of a blend of carbamide and thiocarbamide with table sugar yields S,N-CNMs exhibiting the utmost quantum yield (54 %), hydrophilicity, as well as stable, homogeneous, and diminutive particle size distribution. Fourier transform infrared spectroscopy, transmission electron microscopy, spectrophotometry, and fluorescence spectroscopy were applied to characterize the S,N-CNMs. The S,N-CNMs have been used as a turn-off fluorescence probe to determine pantoprazole via a synergism of the inner filter effect and static quenching mechanisms. The fluorescence quenching is linearly correlated to pantoprazole concentration over the range of 1.0-25.0 µg/mL with a detection limit of 0.16 µg/mL. The developed probe exhibited good selectivity for pantoprazole in the presence of variability of substances. Therefore, it was applied for quality control of pantoprazole in pharmaceutical tablets and vials with an average recovery % of 100.10 ± 0.77 % and 100.33 ± 0.92 %, respectively. Moreover, it was successfully implemented to examine the content uniformity of pantoprazole in tablets. Furthermore, the prepared S,N-CNMs have been successfully used for the analysis of pantoprazole in human plasma after a simple protein precipitation step with a recovery % of 97.88 ± 5.72 %. The greenness and blueness of the developed method have been positively assessed by recent tools showing the eco-friendliness and applicability of the developed method., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Two coordination polymers (CPs), [Zn 5 (L) 2 (phen) 5 ](1) and [Cd 2 (HL)(2,2-bpy)(H 2 O) 3 ](2), were synthesized by using 2',3,3',5,5'-Diphenyl ether pentacarboxylic acid (H 5 L), phenanthroline (phen), and 2,2'-bipyridine (2,2'-bpy) under hydrothermal conditions. The L 5- ligand adopts the μ 6 -к 2 : к 2 : к 1 : к 1 : к 1 : к 1 mode in 1 and the μ 5 -к 2 : к 2 : к 2 : к 2 : к 1 mode in 2. Sensing experiments show that 1 and 2 are fluorescence probes with high sensitivity and rapid detection of nitro explosives, antibiotics, and pesticides. In order to verify the ability of 2 to detect FLU in actual samples, we performed a spiked recovery experiment in green pepper water. The spiked recoveries were 97.77-101.18 %. Interestingly, because H 5 L is not completely deprotonated in 2, there is abundant hydrogen bonding, which makes the fluorescence quenching rate higher and the detection limit lower. The possible fluorescence quenching mechanism of 1 and 2 can be explained by their UV-VIS absorption spectra and orbital energy levels., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: The Yang Hua Report was funded by the Science and Technology project of Shaanxi Province, key scientific research project of Shaanxi Provincial Education Department, the Key industrial chain project of Yan 'an and project of Yan ’an University., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Analyte-triggered semiconductor quantum dots (QDs) modulation in the presence of non-consistently responsive fluorescent species represents a challenging analytical issue in concrete multi-way data handling. QDs with heterogeneous sizes and/or uneven distribution of functional moieties on their surfaces exhibit significant fluctuations in the fluorescent response components, known as chemical rank, across different excitation/emission modes. This phenomenon may lead to a substantial deviation from the proportionality prescribed by Beer-Lambert law. Nonetheless, even in the presence of such deviation, a multi-way model may be successfully selected after determining a proper chemical rank in a QDs system., Results: We show that in a valid PARAllel FACtor (PARAFAC) model under properly determined chemical rank, meaningfully resolved pure spectral profiles can be reached for each fluorescent responsive constituent in the original excitation-emission fluorescence matrix (EEFM) measurements. This was thoroughly illustrated by applying PARAFAC trilinear decomposition of a three-way data array of two distinct datasets acquired from semiconductor QDs sensing systems with low-rank trilinear assumption. The first dataset, presented here for the first time, comprises EEFM measurements of the ligand-driven quenching of thiomalic acid (TMA)-capped AgInS 2 (AIS) QDs by vomitoxin. The second dataset, employed for illustrative purposes, comprises EEFM measurements of the quenching, via cation bridging, of glutathione (GSH)-capped CdTe QDs by Pb(II). The results of this study enabled the determination of vomitoxin at a ppb level in real samples of fish feeds, showcasing the efficacy of the PARAFAC model in resolving spectral signatures (loadings) and pure concentration profiles (scores)., Significance: PARAFAC under a properly examined chemical rank can be easily adapted for retrieval the underlying Beer-Lambert law of the original EEFM measurements with a low-rank trilinear structure through the chemically meaningful information either when (i) no deviation of Beer-Lambert law was observed as deeply discussed in connection with the dataset acquired from vomitoxin-driven molecular sensing through TMA-capped AIS QDs, or when (ii) substantial deviations of the Beer-Lambert law are evident, as discussed in connection with the dataset collected from sensing ionic species through Pb(II) bridging of GSH-capped CdTe QDs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

In this work, the xanthene dye, erythrosine B, was employed as a probe for the determination of olanzapine using two fast and highly simple analytical approaches. The assay was based on the formation of a binary complex between the drug and erythrosine B in a slightly acidic aqueous buffered solution. In the first method, the absorbance of the formed product was monitored at 558 nm. The reaction stoichiometry was investigated, and the stability constant of the formed complex was estimated. The linear range of the method that obeyed Beer's law was in the concentration range of 0.6-8.0 µg/ml. The calculated detection and quantitation limits were 0.2 and 0.6 µg/mL. Upon adding the drug solution to erythrosine B, the native fluorescence of the dye was quenched and monitored at 550 nm after excitation at 528 nm. Thus, the fluorescence quenching was utilized as the quantitative signal in the spectrofluorimetric approach. The extent of quenching in the fluorescence intensity was rectilinear with the drug concentration in a range of 0.1-2.5 µg/ml with a detection limit of 0.032 µg/ml. Both approaches were analytically validated based on the guiding rules of the ICH with acceptable results, and were utilized efficiently in the analysis of olanzapine in commercial tablets containing the cited drug. In addition, owing to its high sensitivity and selectivity, the spectrofluorimetric method was applied for drug analysis in spiked human plasma with satisfactory % recoveries. Finally, the greenness of the methods was confirmed using eco-score scale and Analytical Green Evaluation metrics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

On-site, robust, and quantitative detection of diclofenac (DCF) is highly significant in bioanalysis and quality control. Fluorescence-based metal-organic frameworks (MOFs) play a pivotal role in biochemical sensing, offering a versatile platform for detecting various biomolecules. However, conventional fluorescent MOF sensors often rely on lanthanide metals, which can pose challenges in terms of cost, accessibility, and environmental impact. Herein, an intrinsic blue fluorescent zinc-based metal-organic framework (FMOF-5) was prepared free from lanthanide metals. Coordination-induced emission as an effective strategy was followed wherein a non-fluorescent ligand is converted to a fluorescent one after insertion in a framework. Conventional fluorometry and smartphone-assisted visual methods were employed for the detection of DCF. The fluorescence emission of the FMOF-5 was effectively quenched upon the addition of the DCF, endowing it an "off" condition, which permits the construction of a calibration curve with a wide linear range of 30-670 µM and a detection limit of about 4.1 µM. Other analytical figures of merit, such as linearity, sensitivity, selectivity, accuracy, and precision were studied and calculated. Furthermore, the proposed sensor was successfully applied to quantify DCF in pharmaceutical tablets with reliable recovery and precision. Importantly, the elimination of lanthanide metals from the fluorescence detection system enhances its practicality and sustainability, making it a promising alternative for DCF detection in pharmaceutical analysis applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Two novel fluorescent probes for Cu 2+ detection have been developed based on thiazoline-quinoline conjugates bearing a 4-ethynyl-N,N-dimethylaniline unit (QT1 and QT2). QT2 exhibits instantaneous fluorescence quenching of Cu 2+ with an emissive change from bright orange to arctic blue under UV light irradiation (365 nm). The plots of I 0 /I against Cu 2+ concentrations show a good linear relationship that ranges from 0 to 50 µM with a coefficient of determination (R 2 ) = 0.9906 and a limit of detection (LOD) of 76 nM, which is considered low (4.84 ppb). A 1:1 complexation between QT2 and Cu 2+ was confirmed by UV-Vis titration, ESI-MS, and SC-XRD. The QT2·Cu 2+ complex was dissociated by the addition of EDTA. The fluorescence quenching mechanism involves the ligand-to-metal charge transfer (LMCT) of a paramagnetic Cu 2+ complex. The QT2 probe on a paper-based strip was used to determine the amount of Cu 2+ in water and food samples (shiitake mushrooms and oysters)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Vanillin is a phenolic aldehyde widely used as a flavouring agent in the food industry. Vanillin has many health benefits and has gained attention in pharmacological industries also, due to its antioxidant properties and non-toxic nature. The interaction of vanillin with human hemoglobin (hHb), an abundant tetrameric heme protein, was investigated by several spectroscopic techniques and molecular modeling methods. UV-visible spectra showed that the binding of vanillin to hHb induces structural changes due to alterations in the micro-environment of hHb. Vanillin quenches the intrinsic fluorescence of hHb by the dynamic mechanism, which was confirmed by both temperature dependent and time resolved fluorescence studies. Vanillin binds spontaneously to hHb at a single site and the binding is stabilized by hydrogen bonds and hydrophobic interactions. The circular dichroism spectra showed that the binding of vanillin altered the secondary structure of hHb due to change in its alpha-helical content. Molecular docking identified the amino acids of hHb involved in binding to vanillin and also that the free energy change of the binding reaction is -5.5 kcal/mol. Thus, our results indicate that vanillin binds spontaneously to hHb at a single site and alters its secondary structure. This will help in understanding the potential use of vanillin and related antioxidants as therapeutic agents in various hematological disorders., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The selective binding of ligand molecules towards the 5' and 3' ends of G-quadruplex (G4) may differentially affect the physiological function of G4s. However, there is still a lack of sensitive and low-cost approaches to accurately measure the binding preference of ligands on G4s, although multiple ways have been developed to evaluate the interaction between ligands and G4s. Here, we propose a new protocol named G4-AFQ to test the selectivity of ligands towards the two terminal G-tetrads of G4s. In this protocol, the fluorophore AMCA is respectively modified at the 5' or 3' end of G4, and which end of AMCA fluorescence is quenched means that the ligand binds to the G-tetrad at that end. Through G4-AFQ, the affinity constant of ligands towards the binding site can also be obtained. Compared with the commonly used nuclear magnetic resonance (NMR) method, G4-AFQ is more convenient, sensitive, cost-effective, and suitable for the measurement of the vast majority of G4 ligands, with a great potential for widespread application., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Ascorbic acid (Vitamin C) is crucial for bodily functions, including collagen synthesis, immune system support and antioxidant defense. Despite autism spectrum disorder's multifactorial nature involving genetic, environmental and neurological factors, robust evidence exploring the association between ascorbic acid and this disorder is notably lacking. This study introduces an innovative spectrofluorometric method to quantify ascorbic acid in the plasma of healthy children and those with autism spectrum disorder. The method relies on the interaction of ascorbic acid with the fluorescent dye propidium iodide. In acidic conditions, propidium iodide undergoes protonation and selectively binds to the negatively charged ascorbic acid forming an ion-pair complex. This complex alters the molecular structure of propidium iodide inducing chemical fluorescence quenching, that can be utilized for ascorbic acid quantification. The developed method undergoes rigorous validation following ICH guidelines, demonstrating a linear relationship within a concentration range of 4-40 μg/mL, with high precision and accuracy metrics. Analysis of real plasma samples from autistic and healthy children reveals clinically and statistically elevated levels of ascorbic acid in those with autism spectrum disorder., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relations that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Herein, we report a novel sensor to detect trypsin using a purpose-designed fluorescein-labelled peptide with negatively charged carbon nanoparticles (CNPs) modified by acid oxidation. The fluorescence of the fluorescein-labelled peptide was quenched by CNPs. The sensor reacted with trypsin to cleave the peptide, resulting in the release of the dye moiety and a substantial increase in fluorescence intensity, which was dose- and time-dependent, and trypsin could be quantified accordingly. Correspondingly, the biosensor has led to the development of a convenient and efficient fluorescent method to measure trypsin activity, with a detection limit of 0.7 μg/mL. The method allows rapid determination of trypsin activity in the normal and acute pancreatitis range, suitable for point-of-care testing. Furthermore, the applicability of the method has been demonstrated by detecting trypsin in spiked urine samples.

Photophysical studies in association with molecular docking (MD) methods were employed in the determination of various molecular interactions existing between d-Fructose in the presence of a photoinduced electron transfer (PET) and non-PET based acridinedione (AD) dyes in water. Addition of fructose to AD dyes resulted in a decrease in the absorbance at the longest wavelength absorption maxima accompanied with the formation of an isosbestic point signifying a ground state complex formation. The ground state interaction between fructose and dye is presumably attributed to hydrogen-bonding (HB) and was authenticated by MD studies. Interestingly, the excited state characteristics of PET dye (ADR1) is found to be entirely different from that of non-PET dye (ADR2) on the introduction of fructose. A fluorescence quenching phenomenon is observed in PET dye, whereas an enhancement results in that of a non-PET dye. Fructose promotes electron transfer (ET) through space resulting in a decrease in the fluorescence intensity of ADR1 dye. On the contrary, it suppresses the PET process in ADR2 dye resulting in an increase in the quantum yield. Fluorescence lifetime studies of fructose with AD dyes results in a multi exponential lifetime with varying proportions. The presence of biexponential lifetime components justifies the existence of more than one distinguishable micro heterogenous environment in the aqueous phase containing unequal proportion of distribution of fructose and water molecules around the close vicinity of AD dyes. The local excited (LE) state of the fluorophore experiences a large variation in the excited state such that the emission intensity and fluorescence lifetime are governed by solute induced and solvent mediated HB interactions. MD studies further establish the existence of HB interaction of dye-fructose, wherein the dye acts as the HB donor and sugar as the acceptor. Docking techniques establishes clear and authentic information on the HB donor and acceptor sites in dye and sugar molecule resulting in a most stable conformer. The nature of interaction of a simple sugar molecule with water soluble fluorophores are explored in depth by fluorescence techniques in coordination with MD methods is imparted in the present study.

Nitrogen-doped fluorescent carbon dots (N-CDs) were prepared via hydrothermal synthesis method using citric acid and ethylenediamine as raw materials. The synthesized N-CDs were characterized by transmission electron microscopy (TEM) and multi-spectroscopic techniques. A fluorescent sensor based on the inner filter effect (IFE) was successfully established using synthesized carbon dots to detect the content of Baicalin in Baicalin capsule and the quality of Scutellariae Radix. The Baicalin linear range of the method is 1.6–72 μg·mL−1 (r = 0.9992), the detection limit is 1.0 μg·mL−1 (3-foldσ), and the precision was 0.2%. Furthermore, the N-CDs probe was used to evaluate quality of Scutellariae Radix.

Background: Nitroaromatic compounds are inherently hazardous and explosive, so convenient and rapid detection strategies are needed for the sake of human health and the environment. There is an urgent demand for chemical sensing materials that offer high sensitivity, operational simplicity, and recognizability to effectively monitor nitroaromatic residues in industrial wastewater. Despite its importance, the mechanisms underlying fluorescence quenching or enhancement in fluorescent sensing materials have not been extensively researched. The design and synthesis of multiresponsive fluorescent sensing materials have been a great challenge until now., Results: In this study, a one-dimensional Cd-based fluorescent porous coordination polymer (Cd-CIP-1) was synthesized using 5-(4-cyanobenzyl)isophthalic acid (5-H 2 CIP) and 4,4'-bis(1-imidazolyl)biphenyl (4,4'-bimp) and used for the selective detection of nitrobenzene in aqueous solution by fluorescence quenching, with a limit of detection of 1.38 × 10 -8  mol L -1 . The presence of aniline in the Cd-CIP-1 solution leads to the enhancement of fluorescence property. Density functional theory and time-dependent density functional theory calculations were carried out to elucidate the mechanisms of the fluorescence changes. This study revealed that the specific pore size of Cd-CIP-1 facilitates analyte screening and enhances host-guest electron coupling. Furthermore, π-π interactions and hydrogen bond between Cd-CIP-1 and the analytes result in intermolecular orbital overlap and thereby boosting electron transfer efficiency. The different electron flow directions in NB@Cd-CIP-1 and ANI@Cd-CIP-1 lead to fluorescence quenching and enhancement., Significance and Novelty: The multiresponsive coordination polymer (Cd-CIP-1) can selectively detect nitrobenzene and recognize aniline in aqueous solutions. The mechanism of fluorescence quenching and enhancement has been thoroughly elucidated through a combination of density functional theory and experimental approaches. This study presents a promising strategy for the practical implementation of a multiresponsive fluorescent chemical sensor., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Antibiotics, one of the significant emerging contaminants, are intensifying their continual spread out into the environment and affecting human health and the ecosystem in the developing country Bangladesh. This study characterizes widely used fluoroquinolone (FQ) antibiotics, formulates the method to spectrally distinguish them from ubiquitous, and important reactive, adsorbent, and altering catalytic macromolecule humic substances (HS), and further quantifies them using fluorescence spectroscopy. The presence of identical fluorophore at Excitation/Emission = 225-230/285-295 nm wavelength, possession of fluorescence spectra at short emission wavelength (<350 nm) during 275 nm excitation, different emission maxima, and various fluorescing components in antibiotics identified through three-dimensional excitation-emission matrix (EEM) and parallel factor analysis (PARAFAC) models distinguished them from the humic substance as well as from each other. Stern-Volmer equation and its modified version were applied to identify quenching and binding capability, and fluorescence intensity quenching rate of antibiotics and humic in their mixture. Unlike poor and inconsistent quenching mechanisms of humic, FQ antibiotics reduced HS intensity throughout the entire photo-irradiation experiment affirming the functioning of the stable quenching methods. Static quenching of fluorophores was identified from the redshift of excited wavelength on the electronic ground state. Temperature differences during daylight and dark conditions played contrasting roles during the fluorescence quenching of FQ. Unique spectral response at emission wavelength < 350 nm during 275 nm excitation in FQ was considered as its least intensity in the antibiotic-humic mixture and was also used to formulate distinct spectral pattern of each FQ antibiotic. The study also identified the traces of FQ antibiotics with various intensities at different lakes in Bangladesh., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Three dye-loaded tunable dual-emission colorimetric fluorescent probes RhB@UiO-66-Ph (R@U-P) were prepared by in-situ encapsulation method under solvothermal conditions. The resonance energy transfer between UiO-66-Ph and RhB made the dual emission of R@U-P easily tunable with the embedded dye content changing. The R@U-P composites achieved emission from purple light to red light, and served as probes to realize comparative detection of Fe 3+ , Fe 2+ and Cr 2 O 7 2- in water through colorimetric or quenching detection mode. Mechanism study indicates that the resonance energy transfer or electron transfer interactions between R@U-P composites and inorganic ions resulted in the relative changes of the two emission peaks and realized the selective detection of analytes. The preparation and application of R@U-P probes provide a promising strategy for the in-situ encapsulation dye to obtain two dual-emission composites for the comparative detection of Fe 3+ , Fe 2+ and Cr 2 O 7 2- in water samples., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: The accurate and rapid detection of blood lead concentration is of paramount importance for assessing human lead exposure levels. Fluorescent protein-based probes, known for their high detection capabilities and low toxicity, are extensively used in analytical sciences. However, there is currently a shortage of such probes designed for ultrasensitive detection of Pb 2+ , and no reported probes exist for the quantitative detection of Pb 2+ in blood samples. This study aims to fill this critical void by developing and evaluating a novel fluorescent protein-based probe that promises accurate and rapid lead quantification in blood., Results: A simple and small-molecule fluorescent protein-based probe was successfully constructed herein using a peptide PbrBD designed for Pb 2+ recognition coupled to a single fluorescent protein, sfGFP. The probe retains a three-coordinate configuration to identify Pb 2+ and has a high affinity for it with a K d ' of 1.48 ± 0.05 × 10 -17  M. It effectively transfers the conformational changes of the peptide to the chromophore upon Pb 2+ binding, leading to fast fluorescence quenching and a sensitive response to Pb 2+ . The probe offers a broad dynamic response range of approximately 37-fold and a linear detection range from 0.25 nM to 3500 nM. More importantly, the probe can resist interference of metal ions in living organisms, enabling quantitative analysis of Pb 2+ in the picomolar to millimolar range in serum samples with a recovery percentage of 96.64%-108.74 %., Significance: This innovative probe, the first to employ a single fluorescent protein-based probe for ultrasensitive and precise analysis of Pb 2+ in animal and human serum, heralds a significant advancement in environmental monitoring and public health surveillance. Furthermore, as a genetically encoded fluorescent probe, this probe also holds potential for the in vivo localization and concentration monitoring of Pb 2+ ., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Metal-Organic Frameworks (MOFs) with luminescent properties hold significant promise for environmental remediation. This review critically examines recent research on these materials design, synthesis, and applications, mainly focusing on their role in combating environmental pollutants. Through a comprehensive analysis of metal ions, ligands, and framework compositions, the review discusses the importance of tailored design and synthesis approaches in achieving desired luminescent characteristics. Key findings highlight the effectiveness of luminous MOFs as fluorescent sensors for a wide range of contaminants, including heavy metals, reactive species, antibiotics, and explosives. Considering all this, the review discusses future research needs and opportunities in the field of luminous MOFs. It emphasizes the importance of developing multifunctional materials, refining design methodologies, exploring sensing mechanisms, and ensuring environmental compatibility, scalability, and affordability. By providing insights into the current state of research and outlining future directions, this review is a valuable resource for researchers seeking to address environmental challenges using MOF-based solutions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Functional nucleic acids (FNAs) have attracted a lot of attention for the rapid detection of metal ions. Cr 3+ is one of the major heavy metal ions in natural waters. Due to the slow ligand exchange rate of Cr 3+ , the FNA-based Cr 3+ sensors require long assay times, limiting the on-site applications. In this study, we report that the good's buffers containing amino and polyhydroxy groups greatly increase the ligand exchange rate of Cr 3+ . Using EDTA as a model coordinate ligand, the Tris buffer (100 mM, pH 7.0) showed the best acceleration effect among the eight buffers. It improved the rate constant ∼20-fold, shorten the half-time 19-fold, and lowered the activation energy ∼70% at 40 °C. The Tris buffer was then applied for sensor based on the Cr 3+ -binding induced fluorescence quenching of fluorescein (FAM)-labeled and single-stranded DNA (ssDNA), which shortened the assay time from 1 h to 1 min. The Tris buffer also ∼100% enhanced the fluorescence intensity of FAM, achieving the 11.4-fold lower limit of detection (LOD = 6.97 nM, S/N = 3). By the combination use of the Tris buffer and ascorbic acid, the strong interference from Cu 2+ , Pb 2+ , and Fe 3+ suffered in many previous reported Cr 3+ sensors was avoided. The practical application of the sensor for the detection of Cr 3+ spiked in the real water samples were demonstrated with high recovery percentages. The Tris buffer could be applied for other metal ions with slow ligand exchange rate (such as V 2+ , Co 3+ and Fe 2+ ) to solve diverse issues such as long assay time and low synthesis yield of metal complexes, without the need of heating treatment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Bacteria thrive in biofilms embedding in the three-dimensional extracellular polymeric substances (EPS). Functional Amyloid in Pseudomonas (Fap), a protein in EPS, efficiently sequesters polycyclic aromatic hydrocarbons (PAHs). Present study reports the characterization of Fap fibrils from Pseudomonas aeruginosa PFL-P1 and describes the interaction with pyrene to assess the impact on pyrene degradation. Overexpression of fap in E. coli BL21(DE3) cells significantly enhances biofilm formation (p < 0.0001) and amyloid production (p = 0.0002), particularly with pyrene. Defibrillated Fap analysis reveals FapC monomers and increased fibrillation with pyrene. Circular Dichroism (CD), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) unveil characteristic amyloid peaks and structural changes in Fap fibrils upon pyrene exposure. 3D-EEM analysis identifies a protein-like fluorophore in Fap fibrils, exhibiting pyrene-induced fluorescence quenching. Binding constants range from 5.23 to 7.78 M -1 , with ΔG of -5.10 kJ mol -1 at 298 K, indicating spontaneous and exothermic interaction driven by hydrophobic forces. Exogenous Fap fibrils substantially increased the biofilm growth and pyrene degradation by P. aeruginosa PFL-P1 from 46 % to 64 % within 7 days (p = 0.0236). GC-MS identifies diverse metabolites, implying phthalic acid pathway in pyrene degradation. This study deepens insights into structural dynamics of Fap fibrils when exposed to pyrene, offering potential application in environmental bioremediation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Development of biomolecules coordinated iron ions-based Fenton agents is highly desirable for chemodynamic therapy in term of demanded biocompatibility and enhanced Fenton activity at tumor microenvironmental pH of 6.5. Herein, phycocyanin (PC), the only FDA-approved natural coloring agent, was selected to coordinate with iron ions. The spectroscopic investigations disclosed that PC displayed pH-dependent spectral and conformational responses upon addition of Fe ions. As a result, the effective formation of Fe-PC coordination merely occurred at pH 7 due to a less folded polypeptide matrix of PC. The formed Fe-PC coordination exerted an enhanced Fenton activity at pH 6.5 as attested by 3, 3', 5, 5'-tetramethlbenzidine assay and steady-state kinetic analysis. These findings not only provide fundamental insights of Fe-PC coordination but also highlight the potential biomedical significance of Fe-PC for severing as an effective Fenton agent in chemodynamic therapy., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A highly sensitive detection platform for heparin was constructed via the utilization of a commercially available cationic fluorescent dye (cresyl violet acetate, CV) as a fluorescence probe. The electrostatic binding between CV and heparin quenched the fluorescence in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic (HEPES) buffer solution (10 mM, pH 7.1). CV was highly selective towards heparin over other potential inferring substances. The detection limit of heparin detection was 5.19 ng/mL, and the linear working range was 0 ∼ 1 μg/mL in HEPES solution. In 1 % serum, the detection platform based on the fluorescence "turn-off" behavior of CV was also successfully constructed with a detection limit of 5.86 ng/mL in the linear range of 0 ∼ 0.8 μg/mL. Moreover, the CV-heparin complex was considered a potential sensor platform for the detection of protamine because of its stronger affinity for heparin and protamine., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Chondroitin sulfate (CS) was extracted and purified from shark cartilage, and its interaction with bovine serum albumin (BSA) were studied. The content of chondroitin sulfate in shark cartilage was 29.97 % using the 1,9-dimethyl-methylene blue method. The molecular weight of CS was determined to be 62.464 kDa by high-performance gel permeation chromatography. UV and FT-IR spectroscopy identified the characteristics of CS and its functional group information. NMR spectroscopy and disaccharide derivatization revealed that CS was predominantly composed of disulfated disaccharides, specifically ΔDi4,6S. Fluorescence quenching experiments indicated that the interaction between CS and BSA exhibited static quenching, with a binding site number of 1. The binding process was primarily mediated by van der Waals forces and hydrogen bonds. Furthermore, synchronous and 3D fluorescence spectroscopy demonstrated that CS had minimal impact on the polarity and hydrophobicity of the microenvironment surrounding Tyr and Trp residues. UV-vis absorption and circular dichroism (CD) spectroscopy demonstrated the altered structure of BSA. The molecular docking analysis revealed that CS formed hydrogen bonds and salt bridges with BSA, predominantly binding to the IIA substructure domain of BSA. Investigating the interaction between CS and BSA holds the potential for enhancing its applications in drug delivery and tissue engineering endeavors., Competing Interests: Declaration of competing interest The materials discussed herein have not been published elsewhere before, and the manuscript has not been submitted to any other journals., (Copyright © 2024. Published by Elsevier B.V.)

Jacalin, the jackfruit seed lectin, exhibits high specificity for the tumor-specific T-antigen and is used in various biomedical and biotechnological applications. Here, we report biophysical studies on the thermal unfolding of jacalin and the effect of pH and temperature on its secondary structure. Differential scanning calorimetric (DSC) studies revealed that native jacalin unfolds at ∼60 °C and that carbohydrate binding stabilizes the protein structure. Circular dichroism spectroscopic studies indicated that the secondary structure of jacalin remains mostly unaffected over pH 2.0-9.0, whereas considerable changes were observed in the tertiary structure. DSC experiments demonstrated that jacalin exhibits two overlapping transitions between pH 2 and 5, which could be attributed to dissociation of the tetrameric protein into subunits and their unfolding. Interestingly, only one transition between pH 6 and 9 was observed, suggesting that the subunit dissociation and unfolding occur simultaneously. While quenching of the protein intrinsic fluorescence by acrylamide increased significantly upon carbohydrate binding, quenching by succinimide is essentially unaffected. We attribute this difference to increased exposure of Trp-123 in the α-chain as it is involved in carbohydrate binding. Both acrylamide and succinimide gave biphasic Stern-Volmer plots, consistent with differential accessibility of the two tryptophan residues of jacalin to them., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Musti J. Swamy reports financial support was provided by India Ministry of Science & Technology Department of Science and Technology. Musti J. Swamy reports financial support was provided by University of Hyderabad., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A simple and sensitive graphene oxide-mediated fluorescence quenching aptasensor is developed to quantify albuminuria in urine samples. The developed aptasensor used the specific target binding property of aptamer and fluorescence quenching property of graphene oxide to determine the concentration of human serum albumin in urine. The limit of detection of the developed platform is 0.05 µg.mL−1 and the detection range is 0.1–600 µg.mL−1, which covers the albuminuria concentration range present in normal human urine and the urine of the patient with chronic kidney disease. This approach can be modified to measure albuminuria using a high-throughput quantification platform and portable point of care testing. In addition, the production cost for one reaction is cheaper than those for the standard automated method. Therefore, this aptasensor has significant potential for commercialization and public use. • Our protocol is customized by using the fluorescence quenching property of graphene oxide and specific binding property of human serum albumin aptamer to detect human serum albumin in urine sample • The limit of detection of our developed platform is 0.05 µg.mL−1 • The detection range of our aptasensor is 0.1–600 µg.mL−1

A simple methodology was developed to quantify penicillamine (PA) in pharmaceutical samples, using the selective interaction of the drug with Cu-modified graphene quantum dots (Cu-GQDs). The proposed strategy combines the advantages of carbon dots (over other nanoparticles) with the high affinity of PA for the proposed Cu-GQDs, resulting in a significant and selective quenching effect. Under the optimum conditions for the interaction, a linear response (in the 0.10–7.50 µmol/L PA concentration range) was observed. The highly fluorescent GQDs used were synthesized using uric acid as single precursor and then characterized by high resolution transmission electron microscopy, Raman spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, fluorescence, and absorption spectroscopy. The proposed methodology could also be extended to other compounds, further expanding the applicability of GQDs.