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The on-site detection of mancozeb in food samples holds immense value for food safety. A red-fluorescent europium complex (Eu-PYDC-Phen) has been prepared and employed as a fluorescence probe for mancozeb detection. The optimized probe suspension exhibits excellent detection performances, including a wide linear range (0-0.24 mM), low detection limit (65 nM), rapid response (2 mins) and high selectivity. Moreover, a portable detection platform was carefully designed, integrating the Eu-PYDC-Phen-based fluorescent test strips with smartphone color recognition software. This innovative platform enables visual and on-site detection of mancozeb in tomato, apple, and lettuce, achieving satisfactory recovery rates (90.34 to 106.50%). Furthermore, the integration of machine learning techniques based on hierarchical clustering algorithm has the potential to further improve the prediction and decision-making efficiency in mancozeb detection. This work provides an economical, convenient, and reliable strategy for on-site detection of pesticide in agricultural products, thereby making a meaningful contribution to food safety., 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 Ltd. All rights reserved.)

Enrofloxacin (ENR) residues in animal-derived food and water threaten human health. Simple, low-cost and on-site detection methods are urgently needed. Blue emitting carbon quantum dots (CQDs) and orange rhodamine B (RhB) were used as recognition and reference signals, respectively, to construct a ratiometric fluorescence sensor. After the addition of ENR, the color of the sensor changed from orange to blue because hydrogen bonding induced a considerable increase in CQDs fluorescence. Based on this mechanism, a simple and low cost on-site portable sensing platform was constructed, which integrated a stable UV light strip and a smartphone with voice-controlled phototaking function and an RGB app. The t-test results of spiked ENR recoveries for diluted milk, honey and drinking water revealed no significant differences between the ratiometric fluorescent sensor and portable sensing platform. Thus, this portable sensing platform provides a novel strategy for on-site quantification of quinolone antibiotics in foodstuffs and environmental water., Competing Interests: Declaration of competing interest The authors declared that we have no conflicts of interest to this work. We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Arsenite (As 3+ ), a highly carcinogenic heavy metal ion and widely distributed in nature, can have serious health implications even with minimal exposure. Herein, a portable smartphone device-based ratiometric fluorescence platform was established for sensitive detection of As 3+ . The work relied on the use of metal-organic framework-tagged cDNA (PCN-224-cDNA), with high adsorption capability and fluorescence properties, as an internal reference to quench the fluorescence of FAM-anchored aptamer (FAM-Apt) via hybridization. In the presence of As 3+ , FAM-Apt specifically bound to As 3+ leading to conformational changes, which detached from the PCN-224-cDNA surface. Interestingly, a smartphone-based readout equipment engineered using a 3D-printed hardware device administered the portable detection of As 3+ . The limit of detection (LOD) for the proposed ratiometric biosensor was calculated to be 0.021 ng/mL, significantly below WHO's safety threshold. Hence, it demonstrates significant potential for large-scale screening of As 3+ residues in food and the environment., 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 Ltd. All rights reserved.)

Precise on-site monitoring of alkylresorcinols, a vital biomarker, is crucial for verifying whole wheat foods and accurately quantifying the whole wheat content in various consumer and industrial products. Herein, for the first time, we introduce a novel ratiometric fluorescence sensor (CDs@ZIF-8/CdTe@MIP) for ultrasensitive and selective detection of alkylresorcinols. 5-Heneicosylresorcinol (C21:0 AR), the primary alkylresorcinol homologue in whole wheat grains, was selected as the target analyte. This analyte was specifically and selectively recognized by the incorporation of a molecularly imprinted polymer (MIP) layer. Within this nanoreactor, blue-emitting carbon dots embedded in zeolitic imidazolate framework-8 (CDs@ZIF-8) and orange-emitting CdTe quantum dots served as the self-calibration signal and response signal, respectively. Exploiting a photoinduced electron transfer effect between CdTe and C21:0 AR, the established fluorescence sensor exhibited remarkable sensing performance, offering wide linear responses in 0.005-1 μg·mL -1 and 1-80 μg·mL -1 concentration ranges, and achieving a low detection limit of 1.14 ng·mL -1 . The proposed assay effectively detected C21:0 AR in real samples, including 8 whole wheat foods and 19 whole wheat grains, demonstrating good recoveries and relative standard deviation. Furthermore, an intelligent sensing platform was established by integrating CDs@ZIF-8/CdTe@MIP with a smartphone-assisted device, thus validating the feasibility of visual and on-site monitoring of C21:0 AR. Because of its rapid response, portability, cost-effectiveness, superior sensitivity, and high selectivity, the proposed sensor serves as a reliable method for the analysis of C21:0 AR, thus having substantial potential for on-site monitoring of whole wheat foods.

Dipicolinic acid (DPA), as a biomarker for Bacillus anthracis, is highly toxic at trace levels. Rapid and on-site quantitative detection of DPA is essential for maintaining food safety and public health. This work develops a dual-channel self-calibrated fluorescence sensor constructed by the YVO 4 :Eu and Tb-β-diketone complex for rapid visual detection of DPA. This sensor exhibits high selectivity, fast response time, excellent detection sensitivity, and the detection limit is as low as 4.5 nM in the linear range of 0-16 μM. A smartphone APP and portable ultraviolet lamp can assemble a mobile fluorescence sensor for on-site analysis. Interestingly, adding Cu 2+ ions can quench the fluorescence intensity of Tb 3+ . In contrast, the addition of cysteine can restore the fluorescence, allowing the accurate detection of Cu 2+ ions and cysteine in environmental water and food samples. This work provides a portable sensor that facilitates real-time analysis of multiple targets in food and the environment., Competing Interests: Declaration of competing interest The authors state that they have no known competing financial interests or personal relationships, which may affect the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The misuse of tetracyclines in livestock production poses significant health risks. Thus, establishing convenient detection methods to replace complex laboratory tests for food safety is crucial. In this study, a heterostructure Zn-BTC/IRMOF-3 (denoted as ZBI) asynchronous response fluorescence sensor was developed for the qualitative and quantitative detection of tetracyclines in foods. The ZBI solution exhibited blue fluorescence under UV excitation; upon the introduction of tetracyclines, ZBI selectively recognized the tetracycline molecules through electron transfer, π-π stacking, and chelation, resulting in blue fluorescence quenching and green fluorescence enhancement. The ZBI sensor for tetracycline detection achieved recovery rates ranging from 93.91 to 111.91% in food samples, with a detection limit of as low as 0.086 μmol/L. Lastly, a portable sensing device using support vector classifier was constructed for detecting tetracyclines in real-life scenarios. Our findings introduce a new approach for fabricating fluorescence sensors and offer a novel method for detecting tetracyclines., 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 Ltd. All rights reserved.)

We describe an optical system that detects the presence of E. coli bacteria, making use of the bacteria's natural fluorescence properties. The system provides an excitation signal at 365 nm and detects the emission signal, from the bacteria, at approximately 445 nm. The system also allows the intensity of the emitted signal to be compared with a user-programmable threshold. This allows rapid testing of many samples in a laboratory setting. Complete setup and performance details are provided, enabling the experimentalist to tailor the system parameters to other species of microorganisms, which may have fluorescence properties at other wavelengths.

Chlorophyll fluorescence is a ubiquitous tool in basic and applied plant science research. Various standard commercial instruments are available for characterization of photosynthetic material like leaves or microalgae, most of which integrate the overall fluorescence signals above a certain cut-off wavelength. However, wavelength-resolved (fluorescence signals appearing at different wavelengths having different time dependent decay) signals contain vast information required to decompose complex signals and processes into their underlying components that can untangle the photo-physiological process of photosynthesis. Hence, to address this we describe an advanced chlorophyll fluorescence spectrometer - ChloroSpec - allowing three-dimensional simultaneous detection of fluorescence intensities at different wavelengths in a time-resolved manner. We demonstrate for a variety of typical examples that most of the generally used fluorescence parameters are strongly wavelength dependent. This indicates a pronounced heterogeneity and a highly dynamic nature of the thylakoid and the photosynthetic apparatus under actinic illumination. Furthermore, we provide examples of advanced global analysis procedures integrating this three-dimensional signal and relevant information extracted from them that relate to the physiological properties of the organism. This conveniently obtained broad range of data can make ChloroSpec a new standard tool in photosynthesis research., (© 2024 The Authors. Physiologia Plantarum published by John Wiley & Sons Ltd on behalf of Scandinavian Plant Physiology Society.)

Gemigliptin-Rosuvastatin single-pill combination is a promising therapeutic tool in the effective control of hyperglycemia and hypercholesterolemia. Organic sensors with high quantum yields have profoundly significant applications in the pharmaceutical industry, such as routine quality control of marketed formulations. Herein, the fluorescence sensor, 2-Morpholino-4,6-dimethyl nicotinonitrile 3, (λex; 226 nm, λem; 406 nm), was synthesized with a fluorescence quantum yield of 56.86% and fully characterized in our laboratory. This sensor showed high efficiency for the determination of Gemigliptin (GEM) and Rosuvastatin (RSV) traces through their stoichiometric interactions and simultaneously fractionated by selective solvation. The interaction between the stated analytes and sensor 3 was a quenching effect. Various experimental parameters and the turn-off mechanism were addressed. The adopted approach fulfilled the ICH validation criteria and showed linear satisfactory ranges, 0.2-2 and 0.1-1 μg/mL for GEM and RSV, respectively with nano-limits of detection less than 30 ng/mL for both analytes. The synthesized sensor has been successfully applied for GEM and RSV co-assessment in their synthetic polypill with excellent % recoveries of 98.83 ± 0.86 and 100.19 ± 0.64, respectively. No statistically significant difference between the results of the proposed and reported spectrophotometric methods in terms of the F- and t-tests. Ecological and whiteness appraisals of the proposed study were conducted via three novel approaches: the Greenness Index via Spider Diagram, the Analytical Greenness Metric, and the Red-Green-Blue 12 model. The aforementioned metrics proved the superiority of the adopted approach over the previously published one regarding eco-friendliness and sustainability. Our devised fluorimetric turn-off sensing method showed high sensitivity, selectivity, feasibility, and rapidity with minimal cost and environmental burden over other sophisticated techniques, making it reliable in quality control labs., (© 2024. The Author(s).)

In this work, a flow-based spectrofluorimetric method for iodine determination was developed. The system consisted of a miniaturized chip-based flow manifold for solutions handling and with integrated spectrofluorimetric detection. A multi-syringe module was used as a liquid driver. Iodide was quantified from its catalytic effect on the redox reaction between Ce(IV) and As(III), based on the Sandell-Kolthoff reaction. The method was applied for the determination of iodine in salt, pharmaceuticals, supplement pills, and seaweed samples without off-line pre-treatment. An in-line oxidation process, aided by UV radiation, was implemented to analyse some samples (supplement pills and seaweed samples) to eliminate interferences and release iodine from organo-iodine compounds. This feature, combined with the fluorometric reaction, makes this method simpler, faster, and more sensitive than the classic approach of the Sandell-Kolthoff reaction. The method allowed iodine to be determined within a range of 0.20-4.0 µmol L -1 , with or without the in-line UV digestion, with a limit of detection of 0.028 µmol L -1 and 0.025 µmol L -1 , respectively.

In this study, the pros and cons of the most relevant L-format devices reported in the literature for measuring steady-state fluorescence polarization/anisotropy are identified. Combining all this information, and with the use of modern elements for the acquisition, treatment, and recording of signals, a modern, simple, and economical L-format accessory is implemented to rapidly and continuously record steady-state fluorescence anisotropy. This device can be adapted to the majority of the commercial spectrofluorometers (or fluorometers). During the measurement, the emission polarizer is in permanent rotation by means of a Gimbal brushless DC motor, and as a result the recorded fluorescence signal is sinusoidal. The maximums and minimums of this signal, which are obtained with the help of LabVIEW tools, allow recording the fluorescence anisotropy. The LabVIEW applications developed for this investigation are freely available, so it is not necessary to have LabVIEW software., (Copyright © 2021 Elsevier Inc. All rights reserved.)

A sensing platform with both ratiometric fluorescence and colorimetric responses towards copper(II) ions (Cu 2+ ) and D-penicillamine (D-pen) was constructed based on carbon dots (CDs). o-Phenylenediamine (OPD) was employed as a chromogenic development reagent for reaction with Cu 2+  to generate the oxidation product 2,3-diaminophenazine (oxOPD), which not only emits green fluorescence at 555 nm, but also quenches the blue fluorescence of CDs at 443 nm via the inner filter effect (IFE) and Förster resonance energy transfer (FRET). Additionally, oxOPD exhibits obvious absorption at 420 nm. Since the intense chelation affinity of D-pen to Cu 2+ greatly inhibits the oxidation of OPD, the intensity ratio of fluorescence at 443 nm to that at 555 nm (F 443 /F 555 ) and the absorbance at 420 nm (A 420 ) were conveniently employed as spectral response signals to represent the amount of D-pen introduced into the testing system. This dual-signal sensing platform exhibits excellent selectivity and sensitivity towards both Cu 2+ and D-pen, with low detection limits of 0.019 μM and 0.092 μM, respectively. In addition, the low cytotoxicity of the testing reagents involved in the proposed sensing platform facilitates its application for live cell imaging., (© 2021. Springer-Verlag GmbH Germany, part of Springer Nature.)

A novel capillary-based fluorescence microsensor for artemisinin was developed with functional polyoxometalates (POMs) as nanozyme by a layer-by-layer self-assembly strategy. Vanadomolybdophosphoric heteropoly acid (H 5 PMo 10 V 2 O 40 , PMoV 2 ) and tungstophosphoric heteropoly acid (Na 5 PW 11 O 39 Cu, PW 11 Cu) with high peroxidase-like activity were synthesized and immobilized on capillary to catalyze artemisinin/thiamine reaction and generate the amplified fluorescence signal. The wide linear range up to 13.0 μM with the low limit of detection of 0.03 μM (S/N = 3) was achieved for the determination of artemisinin by using the proposed POMs-microsensor. The method has been successfully used to detect artemisinin in human plasma and antimalarial drugs with satisfactory accuracy. This work developed a novel capillary fluorescence microsensor with functional POMs as nanozyme, which can serve as a promising candidate in fluorescence microanalysis., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

The Ti 3 C 2 MXene quantum dots (Ti 3 C 2 MQDs) derived from Ti 3 C 2 MXene have received much attention because of their remarkable advantages in biosensing. Nevertheless, the functionalization of Ti 3 C 2 MQDs to improve their properties is just in its infant stage. Herein, we firstly synthesized nitrogen and boron co-doped Ti 3 C 2 MQDs (N, B-Ti 3 C 2 MQDs) with good water solubility, strong stability, and high optical characteristics. The N, B-Ti 3 C 2 MQDs exhibit excitation wavelength-dependent blue photoluminescence with optimal excitation/emission peaks at 335/439 nm. Nowadays, the development of fast and real-time detection of tetracycline (TC) in animal derived food is very essential. In this work, a novel point-of-care testing (POCT) platform was established based on ratiometric fluorescence method using N, B-Ti 3 C 2 MQDs coupled with Eu 3+ . Upon addition of TC in the Eu 3+ /N, B-MQDs system, blue fluorescence emission of N, B-Ti 3 C 2 MQDs was quenched and red fluorescence emission of Eu 3+ was enhanced gradually, which was ascribed to the synergistic inner filter effect and antenna effect. Moreover, we prepared test papers with N, B-Ti 3 C 2 MQDs and Eu 3+ for TC detection based on the change of fluorescence color, which could be recognized by color recognizer app installed in the smartphone. Therefore, great promise for POCT of TC is given with the merits of simplicity and visible detection possibility. The proposed method demonstrated a low detection limit of 20 nM. Application of the platform for TC quantification in milk samples opened a novel means for the potential use of N, B-Ti 3 C 2 MQDs in food safety., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

A novel spectrofluorimetric sensing platform was designed for Ractopamine measurement in aqueous and plasma samples. d-penicillamine functionalized graphene quantum dots (DPA-GQDs) was utilized as a fluorescence probe, which was synthesized through the pyrolysis of citric acid in the presence of DPA. This one-pot down-top strategy causes to high-yield controllable synthesis method. The reaction time and probe concentration were optimized. Then, the fluorescence intensity of aqueous samples containing different Ractopamine concentrations and 500 ppm DPA-GQDs were measured at 25°C with an excitation wavelength of 274 nm. The sensing platform was also applied to detect Ractopamine in untreated plasma samples. The fluorescence spectroscopy technique responses indicated a linear relationship between the peak fluorescence intensity and ractopamine concentration in the range of 0.25-15 ppm with low limit of quantification of 0.25 ppm was for aqueous and plasma samples, respectively., (© 2021 John Wiley & Sons Ltd.)

N, Cl-doped carbon dots (N, Cl-CDs) were prepared by hydrothermal method from rhodamine B (RhB) and ethylenediamine (EDA). The resulting N, Cl-CDs exhibited fascinating solvent dependence and strict excitation independence. As the polarity of the solvent increased (from tetrahydrofuran (THF) to water), the emission spectrum of N, Cl-CDs was redshifted and the fluorescence efficiency decreased, which were attributed to hydrogen bond-induced aggregation. Taking advantage of these attributes, the N, Cl-CDs were used as suitable probes for fluorescence and colorimetric dual-mode detection of water in THF. The linear relationship was 0.5-100% water with the detection limit down to 0.093%. Moreover, the sensing platform was converted into a paper-based sensor for handy, real-time, and visible humidity sensing. N, Cl-CDs/PVA films were fabricated and realized continuously tunable solid-state fluorescence, further expanding their practical application., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

A portable smartphone device is reported that uses 3D printing technology for the primary diagnosis of diseases by detecting acetone. The key part of the device consists of red carbon dots (RCDs), which are used as internal standards, and a sensing reagent (3-N,N-(diacethydrazide)-9-ethylcarbazole (2-HCA)) for acetone. With an excitation wavelength of 360 nm, the emission wavelengths of 2-HCA and RCDs are 443 nm and 619 nm, respectively. 2-HCA effectively captures acetone to form a nonfluorescent acylhydrazone via a condensation reaction occurring in aqueous solution, resulting in obvious color changes from blue-violet to dark red. The detection limit for acetone is 2.62 μM (~ 0.24 ppm). This is far lower than the ketone content in normal human blood (≤ 0.50 mM) and the acetone content in human respiratory gas (≤ 1.80 ppm). The device has good recovery rates for acetone detection in blood and exhaled breath, which are 90.56-109.98% (RSD ≤ 5.48) and 92.80-108.00% (RSD ≤ 5.07), respectively. The method designed here provides a reliable way to provide health warnings by visually detecting markers of ketosis/diabetes in blood or exhaled breath. The portable smart phone device visually detects ketosis/diabetes markers in the blood or exhaled breath through the nucleophilic addition reaction, which effectively captures acetone to form nonfluorescent acyl groups. This will be a reliable tool to warn human health., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

A colorimetric and fluorescent dual-channel detection method for acid phosphatase (ACP) activity has been constructed, based on the internal filtering effect between oxidized 3,3',5,5'-tetramethylbenzidine (oxTMB) and rhodamine B (RB). Au 3+ , which in situ form gold nanoparticles (AuNPs), can oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) to oxTMB (blue color). The fluorescence of RB can be quenched by oxTMB due to the spectral overlap of emission of RB and absorption of oxTMB. By means of the above process, ACP can be determined because ACP promotes the hydrolysis of 2-phospho-L-ascorbic acid trisodium salt (AAP) to generate ascorbic acid (AA), which can inhibit the internal filtering effect between RB and oxTMB. No material preparation was needed for the determination of ACP. The colorimetric and fluorimetric methods can quantify ACP in the range 0.06-5.0 mU/mL and 0.03-5.0 mU/mL, respectively. Furthermore, a smartphone-assisted sensing platform has been constructed for on-site monitoring of ACP in the range 0.75-50 mU/mL, and the detection limit is 0.3 mU/mL. The methods developed can measure ACP in human serum successfully., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

The dynamics of peptide-protein binding and unbinding of a variant of the RNase S system has been investigated. To initiate the process, a photoswitchable azobenzene moiety has been covalently linked to the S-peptide, thereby switching its binding affinity to the S-protein. Transient fluorescence quenching was measured with the help of a time-resolved fluorometer, which has been specifically designed for these experiments and is based on inexpensive light-emitting diodes and laser diodes only. One mutant shows on-off behavior with no specific binding detectable in one of the states of the photoswitch. Unbinding is faster by at least 2 orders of magnitude, compared to that of other variants of the RNase S system. We conclude that unbinding is essentially barrier-less in that case, revealing the intrinsic dynamics of the unbinding event, which occurs on a time scale of a few hundred microseconds in a strongly stretched-exponential manner.

A smartphone-based dual-wavelength digital imaging platform containing red (539-695 nm) and blue (389-511 nm) band-pass filters was developed for point-of-care (POC) testing of alkaline phosphatase (ALP) activity. The platform was based on dual-emitting fluorescent nanohybrids (AuNC@NAN), the ratiometric probe, which had a fluorescence "on-off-on-off" response. The probe comprised red-emitting gold nanoclusters (AuNCs) acting as the signal report units and blue-emitting N-(2-aminoethyl-1,8-naphthalimide) (NAN) acting as an internal reference. The different responses of the ratiometric probes resulted in a continuous color-multiplexing change from pink-red to dark-purple upon exposure to ALP. The dual-wavelength digital imaging platform was employed to acquire images of AuNC or NAN fluorescence signals without the influence of background light. Unlike the classical one-time digital imaging mode, the accurate red (R) and blue (B) channel values of the generated images can help to directly judge or eliminate the disturbance from unavoidable interfering factors. The R/B values were successfully employed for determining the ALP activity at a range 2.0 to 35.0 mU·mL -1 with the detection limit of 1.04 mU·mL -1 . Such sensing imaging platform is also successful in determining ALP activity in human serum with 94.9-105% recoveries and relative standard deviation in the range 4.2-5.6%. A novel dual-wavelength smartphone-based digital imaging platform was proposed for simultaneous readout of the reporting and internal reference signals from dual-emitting ratiometric fluorescence probes, which allowed us to the accurate, reliable, and highly sensitive assay of ALP activity in complex samples.

We developed a facile detection method of spermine based on the fluorescence (FL) quenching of the ciprofloxacin-Tb3+ complex, which shows astrong green emission. Ciprofloxacin (CP) makes efficient bondings to Tb3+ ion as a linker molecule through carboxylic and ketone groups to form a kind of lanthanide coordination polymer. The addition of spermine that competes with Tb3+ ions for the interaction with CP due to its positive charge brings about weakened coordination linkage of CP and Tb3+. The probe exhibited high sensitivity, selectivity, and good linearity in the range of 2-180 μM with a low limit of detection of 0.17 μM. Moreover, we applied this method on the paper strip test (PST), along with the integration of a smartphone and Arduino-based device. The practical reliability of the developed probe was evaluated on human serum samples with acceptable analytical results., Competing Interests: The authors have declared that no competing interests exist.

Herein, we developed a turn-on red-emitting fluorescent probe for the sensitive and selective detection of copper ions (Cu 2+ ) in food samples and living zebrafish. The probe employs a hemicyanine scaffold as the fluorophore and a 2-pyridinecarbonyl group as the recognition receptor and quenching moiety. The 2-pyridinecarbonyl moiety can be specifically cleaved by Cu 2+ and results in an approximately 18-fold fluorescence enhancement of the probe, thereby providing a fluorescence turn-on assay for Cu 2+ . Additionally, the probe exhibited excellent selectivity, high sensitivity, a broad linear relationship (0.020 to 8.0 μM), and a low limit of detection (4.0 nM, S/N = 3) for Cu 2+ . Concomitantly, the probe exhibited satisfactory analytical performance when used with actual food samples. Moreover, the probe could be used for in situ determination of Cu 2+ in both living plant tissues and in living zebrafish., (Copyright © 2020. Published by Elsevier Ltd.)

Background: Finding and preserving normal parathyroid glands or localizing and removing diseased parathyroid glands are crucial steps to successful thyroid and parathyroid operations. Using near-infrared fluorescence detection to identify parathyroid glands during thyroid and parathyroid operations has lately gained widespread recognition, with 2 Food and Drug Administration-cleared devices currently in the market. We aim to update the endocrine surgery community on how near-infrared fluorescence detection can be most optimally used for rapid intraoperative parathyroid gland identification or preservation., Methods: A literature review was performed using the key terms: "parathyroid," "near infrared," and "fluorescence" in relevant search engines. Based on the reviewed literature and expert surgeons' opinions, recommendations were formulated for applying near-infrared fluorescence detection to identify or preserve parathyroid glands during cervical endocrine surgery., Results: The scope of near-infrared fluorescence detection can be broadly categorized into (1) using near-infrared auto-fluorescence to identify or locate both healthy and diseased parathyroid glands, and (2) using contrast-enhanced near-infrared fluorescence to evaluate parathyroid gland perfusion. The benefits and pitfalls for both near-infrared-based approaches are described herein., Conclusion: Near-infrared fluorescence detection appears helpful for identification and likely preservation of parathyroid glands. We hope these recommendations will be valuable to the practicing endocrine surgeon as they consider incorporating these intraoperative adjuncts in their surgical practice., (Copyright © 2020 Elsevier Inc. All rights reserved.)

A simple, sensitive and rapid fluorometric system has been developed for the detection of aldicarb (ALD) based on inner filter effect (IFE) of gold nanoparticles (AuNPs) on fluorescence (FL) intensity of carbon quantum dots (CQDs). Addition of CQDs into AuNPs, gets them aggregated due to electrostatic interaction resulting in quenching the FL intensity of CQDs. With addition of ALD into AuNPs, an intercalated layer was formed between them through Au-N and Au-S bond which reduced IFE of AuNPs. Hence, CQDs FL intensity recovered along with ALD concentration varying between 3.8 and 76 µg L -1 with lower detection limit of 3.02 µg L -1 . The spiked real samples study in fruits, vegetables and soft drinks revealed that this sensing platform was repeatable and effective for real samples. The validation of proposed method indicates that the ALD sensor is promising and adaptable for everyday on spot environment and food safety monitoring., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Thrombin is an important enzyme that plays a pivotal role in the blood clotting pathways. An imbalance in the activity of this enzyme is clinically known to be associated with various diseases, such as thrombosis, inflammation, atherosclerosis, and haemophilia, suggesting the need to devise sensors for Thrombin detection. However, the majority of the fluorescence-based Thrombin assays rely on fluorescence labelling assays or Thrombin specific recognition biomolecules, such as, aptamers or antibody which requires sophisticated techniques and makes it very expensive. Herein, we report a simple, selective, sensitive and label-free fluorescence detection scheme for Thrombin which is based on the interaction between Thrombin and a fluorescent complex of Heparin with a molecular rotor dye, Thioflavin-T. The detection scheme exploits selective interaction between cationic Thrombin and anionic Heparin to modulate the monomer-aggregate equilibrium of the Thioflavin-T-Heparin system. Importantly, the present system offers a ratiometric response that has the ability for robust quantification of Thrombin concentration even in complex medium. The involvement of all commercially available components is a crucial advantage of this detection scheme. Further, the detection scheme also shows reasonable response in diluted serum matrix., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Noninvasive fluorescent imaging requires far-red and near-infrared fluorescent proteins for deeper imaging. Near-infrared light penetrates biological tissue with blood vessels due to low absorbance, scattering, and reflection of light and has a greater signal-to-noise due to less autofluorescence. Far-red and near-infrared fluorescent proteins absorb light >600 nm to expand the color palette for imaging multiple biosensors and noninvasive in vivo imaging. The ideal fluorescent proteins are bright, photobleach minimally, express well in the desired cells, do not oligomerize, and generate or incorporate exogenous fluorophores efficiently. Coral-derived red fluorescent proteins require oxygen for fluorophore formation and release two hydrogen peroxide molecules. New fluorescent proteins based on phytochrome and phycobiliproteins use biliverdin IXα as fluorophores, do not require oxygen for maturation to image anaerobic organisms and tumor core, and do not generate hydrogen peroxide. The small Ultra-Red Fluorescent Protein (smURFP) was evolved from a cyanobacterial phycobiliprotein to covalently attach biliverdin as an exogenous fluorophore. The small Ultra-Red Fluorescent Protein is biophysically as bright as the enhanced green fluorescent protein, is exceptionally photostable, used for biosensor development, and visible in living mice. Novel applications of smURFP include in vitro protein diagnostics with attomolar (10-18 M) sensitivity, encapsulation in viral particles, and fluorescent protein nanoparticles. However, the availability of biliverdin limits the fluorescence of biliverdin-attaching fluorescent proteins; hence, extra biliverdin is needed to enhance brightness. New methods for improved biliverdin bioavailability are necessary to develop improved bright far-red and near-infrared fluorescent proteins for noninvasive imaging in vivo., (© 2020 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.)

A sensor system was designed for the detection of Enoxaparin (Enox), a low molecular weight heparin (LMWH) that was run over the fluorescence quenching mechanism of fluorescein (FL) dye. At nanomolar concentrations, FL probe was subjected to fluorescence quenching by Fe(III). Fluorescence quenching mechanism of FL by Fe(III) was examined using various analytical techniques such as UV-vis absorption, fluorescence, and Fourier transform Infrared spectroscopy techniques, as well as with scanning electron microscope. The results indicated that photoinduced electron transfer process occurred between FL and Fe and that FL was quenched both statically and dynamically. Thermodynamic parameters showed that the interactions between them were predominantly hydrophobic interactions. Enox caused FL to recover its lost fluorescence properties and an increase was observed in the intensity of the fluorescence. Enox was detected successfully with the turn on fluorescence sensor. The developed Enox biosensor exhibited linearity in the range of 0-1.1 μg/ml. For Enox detection, the limit of detection was measured as 255 ng/mL. Enox biosensor was presented as a practical, simple, and applicable sensor system with high sensitivity and good selectivity. Enox is a medication usually monitored indirectly over anticoagulation. This study was presented as an alternative method for monitoring Enox directly. HIGHLIGHTS: Fluorescence quenching of Fluorescein dye by Fe(III) was studied in detail. The presence of enoxaparin enhanced the fluorescence properties of the fluorescein dye. A sensitive, simple and effective sensor system for determination of Enoxaparin, a low molecular weight heparin was shaped in the aqueous media. It was presented as a new method for Enoxaparin to be followed directly.

A thiourea-based fluorescent chemosensor NADA, (E)-2-(4-(diethylamino)-2-hydroxybenzylidene)-N-(naphthalen-1-yl)hydrazine-1-carbothioamide, has been designed and synthesized. NADA could detect Ga 3+ through a fluorescent turn-on with a low detection limit (0.29 μM). Importantly, NADA could effectively discriminate Ga 3+ from Al 3+ and In 3+ . The binding mechanism of NADA with Ga 3+ was identified by ESI-mass, NMR titration, and DFT calculations.

Virus severely endangers human life and health, and the detection of viruses is essential for the prevention and treatment of associated diseases. Metal-organic framework (MOF), a novel hybrid porous material which is bridged by the metal clusters and organic linkers, has become a promising biosensor platform for virus detection due to its outstanding properties including high surface area, adjustable pore size, easy modification, etc. However, the MOF-based sensing platforms for virus detection are rarely summarized. This review systematically divided the detection platforms into nucleic acid and immunological (antigen and antibody) detection, and the underlying sensing mechanisms were interpreted. The nucleic acid sensing was discussed based on the properties of MOF (such as metal ion, functional group, geometry structure, size, porosity, stability, etc.), revealing the relationship between the sensing performance and properties of MOF. Moreover, antibodies sensing based on the fluorescence detection and antigens sensing based on molecular imprinting or electrochemical immunoassay were highlighted. Furthermore, the remaining challenges and future development of MOF for virus detection were further discussed and proposed. This review will provide valuable references for the construction of sophisticated sensing platform for the detection of viruses, especially the 2019 coronavirus., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Methanol is highly toxic for human, so methanol detection is valuable especially in water and ethanol medium without complicated and time consuming procedure. In this work, we present a new fluorescence probe for direct detection of methanol in aqueous and ethanol medium based on the ZnS:Mn 2+ quantum dot (QDs) and soluble N-methylpolypyrrole (NMPPy) hybrid. Moreover, the number of spectroscopic techniques were used to study the chemical composition and optical properties of the resultant QDs as well as investigation on the sensing mechanism toward methanol. Also, methanol can be determined by using ZnS:Mn 2+ QDs/NMPPy hybrid based switchable fluorescence sensing system, with high sensitivity, high selectivity and a very good detection limit of 1 mM with linearity in the concentration range of 25-230 mM (~0.1-0.9% v/v) in aqueous solution. Finally, the ZnS:Mn 2+ QDs/NMPPy hybrid as optical sensor was successfully utilized to determine the amount of methanol in real alcoholic beverage 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 © 2020 Elsevier Ltd. All rights reserved.)

A ratiometric fluorescent probe (Probe 1) was developed for the sensitive detection of β-galactosidase (β-gal) activity. Probe 1 detected β-gal activity in the range 0-1.0 U/mL, with a limit of detection of 0.025 U/mL. In addition, as different activities of β-gal added, the luminescent intensity of Probe 1 gradually increased, as observed under a 365 nm ultraviolet lamp. Moreover, this method is low-volume, 20 μL, and time-efficient, 45 min per measurement. Probe 1 was successfully used to measure the β-gal activity in real fruit samples in a qualitative manner, by the naked eye, fast semi-quantitative manner, by smartphone, or quantitative manner, by fluorescence spectrometer., 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 © 2020 Elsevier Ltd. All rights reserved.)

Capillary electrophoresis (CE) is a highly efficient separation method capable of handling small sample volumes (∼pL) and low (∼yoctomole) detection limits and, as such, is ideal for applications that require high sensitivity, such as single-cell analysis (Chen et al. Anal. Chem. 1996 , 68 (4), 690-696; Cohen et al. Annu. Rev. Anal. Chem. 2008 , 1 (1), 165-190; Vickerman et al. ACS Chem. Biol. 2018 , 13 (7), 1741-1751). Low-cost CE instrumentation is quickly expanding, but low-cost, open-source fluorescence detectors with ultrasensitive detection limits are lacking (Vickerman et al. ACS Chem. Biol. 2018 , 13 (7), 1741-1751; Fang et al. Electrophoresis 2016 , 37 (17-18), 2376-2383; Casto et al. Anal. Chem. 2019 , 40 (1), 65-78). Silicon photomultipliers (SiPM) are inexpensive, low-footprint detectors with the potential to fill the role as a detector when cost, size, and customization are important. In this work, we demonstrate the use of a SiPM in CE with zeptomolar detection limits and a dynamic range spanning 5 orders of magnitude, comparable to photomultiplier detectors. The performance of these detectors was measured using a continuous wave excitation laser in an epifluorescence detection configuration. We characterize the performance of the SiPM as a highly sensitive detector by measuring enzyme activity in single cells. This simple, small footprint, and low-cost (<$130) light detection circuit will be beneficial for open-source, portable, and budget-friendly instrumentation requiring high sensitivity.

A novel molecularly imprinted ratiometric fluorescent probe was fabricated by simple sol-gel polymerization for selective and sensitive assay of C-type natriuretic peptide (CNP) in biosamples. Both the nitrobenzoxadiazole (NBD) and carbon dots (CDs) were located on the surface of silica, used as the detection signal and reference signal, respectively. For the turn-on-based probe, the fluorescence intensity of NBD could be quantitatively enhanced by CNP based on the strategy of photo-induced electron transfer (PET), while the fluorescence of CDs remained unchanged. The obtained probe exhibited excellent recognition selectivity and fast kinetics to CNP templates, and also showed good stability. The linear range of CNP determination was 5-80 pg mL -1 with a low detection limit of 2.87 pg mL -1 . Finally, the probe was successfully applied to determine CNP in human serum samples and attained high recoveries between 97.3 and 104% with precisions below 4.7%. The result indicates that the proposed method has promising potential for the assay of trace peptides in complex matrices. Schematic illustration for the formation and determination mechanism of the probe.

In this paper, a novel and facile synthetic method of 3-mercaptopropionic acid functionalized copper nanoclusters with aggregation-induced emission (AIE) induced by Cu 2+ (Cu 2+ @MPA-Cu NCs) was developed by a one-pot reaction as a fluorescent probe for the detection of sulfide ion (S 2- ). The prepared Cu 2+ @MPA-Cu NCs behaved as aggregated clusters and had strong pink fluorescence under 365 nm UV light with excellent fluorescence emission at 610 nm. The quantum yield increased from 0.56% to 4.8% before and after Cu 2+ added. The presence of S 2- would strongly bind to Cu 2+ , which caused the structure of the aggregated Cu 2+ @MPA-Cu NCs to be destroyed and then the fluorescence quenched. On the basis of this principle, a fluorescent probe was constructed for the detection of S 2- with a very good linearity in the range 0-600 μM ( R 2 = 0.9843) and a detection limit of 26.3 nM. Finally, the nanohybrids were successfully demonstrated for the application in the selective detection of S 2- in food additives. This study essentially paved a new avenue for effectively developing an easy sensor platform for S 2- measurements in food additives.

Carbon dots (CDs) have been a new class of fascinating carbon-based fluorescent nanomaterials. In the present work, new N-doped CDs with highly crystalline graphite structures are prepared from renewable precursors, chitosan and tartaric acid, and are well characterized. The prepared CDs are applied as a biocompatible fluorescent sensor for the sequential detection of Fe 3+ and AA. Among various transition metal ions, Fe 3+ can selectively quench the fluorescence of CDs. Upon the further addition of AA, the quenched fluorescence of CDs is then restored as Fe 3+ is reduced to Fe 2+ by AA, which can be utilized for the fluorescent determination of AA. A good linear relationship in the range of 0-150 μM of AA concentration is established with a low detection limit of 0.02 µM. Moreover, the practical applications of this fluorescent sensing method in measurement of AA in food samples are successfully realized with satisfactory results., 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 © 2020 Elsevier Ltd. All rights reserved.)

A reaction-based luminescence chemosensor was synthesized for sulfite detection based on a fluorescein derivative with thermally activated delayed fluorescence (TADF). The chemosensor exhibited a fluorescence turn-on effect on sulfite with good sensitivity and selectivity. Importantly, utilizing the long luminescence lifetime of the TADF compound, the chemosensor realized photoluminescence lifetime imaging for sulfite in living cells with the luminescence lifetime distribution mainly around 14 μs.

The glucose oxidase-peroxidase (GOD-POD) method used to measure serum unbound bilirubin (UB) suffers from direct bilirubin (DB) interference. Using a bilirubin-inducible fluorescent protein from eel muscle (UnaG), a novel GOD-POD-UnaG method for measuring UB was developed. Newborn sera with an indirect bilirubin/albumin (iDB/A) molar ratio of <0.5 were classified into four groups of DB/total serum bilirubin (TB) ratios (<5%, 5-10%, 10-20%, and ≥20%), and the correlation between the UB levels and iDB/A ratio was examined. Linear regression analysis was performed to compare UB values from both methods with the iDB/A ratio from 38 sera samples with DB/TB ratio <5% and 11 samples with DB/TB ratio ≥5%. The correlation coefficient ( r ) between UB values and the iDB/A ratio for the GOD-POD method was 0.8096 (DB/TB ratio <5%, n = 239), 0.7265 (5-10%, n = 29), 0.7165 (10-20%, n = 17), and 0.4816 (≥20%, n = 16). UB values using the GOD-POD-UnaG method highly correlated with the iDB/A ratio in both <5% and ≥5% DB/TB ratio sera ( r = 0.887 and 0.806, respectively), whereas a low correlation ( r = 0.428) occurred for ≥5% DB/TB ratio sera using the GOD-POD method. Our GOD-POD-UnaG method can measure UB levels regardless of the presence of DB.

The estimation of yeast viability with B- and N-doped carbon dots (BN-CDs) was investigated in this paper. BN-CDs with a fluorescent quantum yield of 65.47% were prepared by a one-step hydrothermal method. The size distribution of BN-CDs was relatively narrow, with the majority falling within 7.5-8.5 nm, and they were mainly composed of carbon, oxygen, nitrogen, and boron. BN-CDs were shown to have strong and stable fluorescence. They exhibited excitation-independent photoluminescence property, which could avoid the autofluorescence and limitation of the excitation source. Dead and live yeast cells were distinguished well by BN-CD staining in a short time, and there was no strict requirement for light protection. The application of BN-CDs in beer brewing can solve the problem of estimation of yeast viability.

Fluorescence imaging technology has been extensively applied in chemical and biological research profiting from its high sensitivity and specificity. Much attention has been devoted to breaking the light diffraction-limited spatial resolution. However, it remains a great challenge to improve the axial resolution in a way that is accessible in general laboratories. Surface plasmon-coupled emission (SPCE), generated by the interactions between surface plasmons and excited fluorophores in close vicinity of the thin metal film, offers an opportunity for optical imaging with potential application in analysis of molecular and biological systems. Benefiting from the highly directional and distance-dependent properties, SPCE imaging (SPCEi) has displayed excellent performance in bioimaging with improved sensitivity and axial confinement. Herein, we give a brief overview of the development of SPCEi. We describe the unique optical characteristics and constructions of SPCEi systems and highlight recent advances in the use of SPCEi for biological applications. We hope this review provides readers with both the insights and future prospects of SPCEi as a new promising imaging platform for potentially widespread applications in biological research and medical diagnostics. Graphical abstract.

A core-shell molecular imprinting fluorescence nanosensor was developed for the ratiometric fluorescence and visual detection of folic acid (FA). The nanosensor was prepared by anchoring imprinting shell on the silica nanoparticles, and embedding the CdTe quantum dots in imprinted shell to provide FA-dependent fluorescence signals. Under the optimum conditions, a favorable linearity relationship between the fluorescence intensities ratio (I 449 /I 619 ) and the FA concentration over 0.23-113 μM was offered with a detection limit (LOD) of 48 nM. The visual detection for FA was realized by evaluating profuse fluorescence color change from red to pink to purple to final blue. The proposed sensor possessed excellent sensing performances of rapid response, high precision, super sensitivity and selective recognition. Furthermore, endogenous FA was detected in real samples ranging from 37.4 to 265.8 μg/100 g; satisfactory spiked recoveries were obtained within 94.8-104.2%, which conformed to the measurement results by HPLC-UV., 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 © 2020 Elsevier Ltd. All rights reserved.)

Given their photoluminescent character, portable quantum dot readers are often sophisticated and relatively expensive. In response, we engineered a "do it yourself" fluorescence reader employing paper materials and a mid-range smartphone camera. Black paperboard facilitated a versatile, lightweight and foldable case; whereas cellophane paper was observed to behave as a simple, yet effective, optical bandpass filter leading to an advantageous device for the quantitative interrogation of quantum dot nanocrystals concentrations (from 2.5 to 20 nM), which are suitable for optical point-of-care biosensing. The streptavidin-coated nanocrystals employed are commercially available and the developed reader was benchmarked with a standard portable quantum dot reader, thereby demonstrating advantages in terms of cost and linear analytical range.

Biotic and abiotic stress both cause a considerable decrease in the chlorophyll content in plant leaves, which provides a means for the early diagnosis of diseases in plants. The emergence of diseases affects the fluorescence of phenolic compounds and chlorophyll, which have emissions located at 530, 686 and 735 nm. Herein, it was found that the intensity of the emission band of phenolic compounds at 530 nm increased and that of chlorophyll at 735 nm decreased with the onset of diseases. Statistical analysis through principal component analysis (PCA) and partial least squares regression (PLSR) was performed, which differentiated between apparently healthy leaf sites and diseased leaves, providing a basis for the detection of diseases in the early stages. The PLSR model was validated through the coefficient of determination (R 2 ), standard error of prediction (SEP) and standard error of calibration (SEC) with the values of 0.99, 0.394 and 0.0.401, respectively, which authenticated the model. The prediction accuracy of the model was evaluated through root mean square error in prediction (RMSEP), with a value of 0.14, by predicting 22 unknown emission spectra of different leaf sites. Both the PCA and PLSR models produced similar results, proving that fluorescence spectroscopy is an excellent tool for early disease detection in plants.

We report on the combined label-free/fluorescence use of one-dimensional photonic crystals to optimize cancer biomarker detection in complex biological media. The optimization of the assay working parameters permits us to maximize the final response of the biosensor. The detection approach utilizes a sandwich assay, in which one-dimensional photonic crystals sustaining Bloch surface waves are modified with monoclonal antibodies in order to guarantee high specificity during biological recognition. The multiple outcomes generated by such optimization experiments permitted us to determine the effective capture efficiency and the repeatability of the immobilization process, which was estimated to be close to 5%. By exploiting the resolution of the fluorescence operation mode, we studied non-specific interactions in different blocking agents, different analyte diluting buffers, and diverse concentrations of the detection antibody. As a clinically relevant biomarker, we selected the trans-membrane receptor tyrosine kinase HER2. HER2 regulates a variety of cell proliferation, growth, and differentiation pathways and its over-expression occurs in approximately 20-30% of breast cancer worldwide. As a final application, we transferred all the optimized working parameters to HER2 cancer biomarker assays in a complex biological environment. The label-free and fluorescence results obtained by analyzing MCF-7 (HER2 low positive) and 32D (HER2 negative) cell lysates demonstrate that we can successfully discriminate the two lysates.

Cocultures bear great potential in the conversion of complex substrates and process intensification, as well as, in the formation of unique components only available due to inter-species interactions. Dynamic data of coculture composition is necessary for understanding and optimizing coculture systems. However, most standard online determined parameters measure the sum of all species in the reactor system. The kinetic behavior of the individual species remains unknown. Up to now, different offline methods are available to determine the culture composition, as well as the online measurement of fluorescence of genetically modified organisms. To avoid any genetic modification, a noninvasive online monitoring tool based on the scattered light spectrum was developed for microtiter plate cultivations. To demonstrate the potential, a coculture consisting of the bacterium Lactococcus lactis and the yeast Kluyveromyces marxianus was cultivated. Via partial least squares regression of scattered light spectra, the online determination of the individual biomass concentrations without further sampling and analyses is possible. The results were successfully validated by a Coulter counter-analysis, taking advantage of the different cell sizes of both organisms. The findings prove the applicability of the new method to follow in detail the dynamics of a coculture., (© 2019 The Authors. Biotechnology and Bioengineering published by Wiley Periodicals, Inc.)

Fluorescence capillary analysis (FCA) realizes trace-level analysis of micro-volume samples; it is easy to operate, extremely low in analytical cost and can significantly lessen environmental pollution from analytical chemistry waste. FCA has the characteristics of green analytical chemistry and has been applied in clinical, biochemical, pharmaceutical, food safety and other fields. FCA basically involves a micro-volume glass capillary, a capillary holder and an ordinary fluorescence detector. The capillary is not only a container for chemical reaction and detection but also functions as a carrier to immobilize enzymes, gene probes or reagents; it can be used repeatedly or can be disposable. In analysis, the capillary which is modified with functional reagents sucks in a measured liquid for the reaction and is then inserted into the holder within the fluorescent detector for measurement. The immobilized FCA method has been successfully used in the determination of reduced coenzyme I, ethanol in liqueur, lactic acid in dairy products, pyruvic acid and glucose in serum, trace-level sulfated bile acid in urine, the ratio of pyruvic/lactic acid in serum, and pyruvic acid in cells as well as in DNA end-labeling and dyeing methods. Further, FCA can also be extended to capillary arrays to complete multipurpose simultaneous determinations and can be combined with mobile phones as fluorescence detectors for use in mobile health analytical technology. FCA will produce considerable social benefits in medicine, pharmacy, fermentation of food, environmental protection and other fields. Therefore, the relevant contents are presented in this tutorial review.

A novel quinazolinone based turn-on fluorescence probe for sensitive monitoring hypochlorite was prepared using the mild condensation reaction between 2-(2'-hydroxyphenyl)-4(3H)-quinazolinone derivative and 4-methylbenzenesulfonyl hydrazide. The probe exhibited specific selectivity to ClO - with obvious optical signal changes from weak fluorescence at 560 nm to a strong fluorescence emission at 520 nm and color changes from colorless to yellow, which could be noticed by the naked eye. The detection limit toward hypochlorite is as low as 11.4 nM. Moreover, the probe could sensitively response to ClO - in living cells with satisfying imaging effect and has been successfully applied to the determination of ClO - in practical water samples, which indicated that the probe has certain application potential for hypochlorite monitoring., 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 © 2019 Elsevier B.V. All rights reserved.)

A highly accurate, simple and sensitive spectrofluorimetric analytical method for dapagliflozin (DGF) quantitation was developed. The proposed method was successively applied to DGF analysis in both its pure and pharmaceutical dosage forms. This method was developed to investigate DGF stability in its degradation products, as laid out in International Council for Harmonisation (ICH) rules. Kinetics of alkaline degradation of DGF was also calculated. The half-life time (t 1/2 ) of the reaction was 75.32 min. An alkaline degradation pathway was described. The present study involved measurement of the second-derivative synchronous fluorescence intensity of DGF at Δλ = 30 nm. Peak amplitude was measured at 322 nm. Linear range of the calibration curve was 0.1-1.0 μg ml -1 . Lower detection and quantitation limits were 0.023 and 0.071 μg ml -1 , respectively, and indicated good sensitivity of the proposed method. Mean per cent recovery was 99.78 ± 1.78%. The proposed analytical approach was successfully applied to DGF in the quality control laboratory and would be suitable as a stability-indicating assay., (© 2019 John Wiley & Sons, Ltd.)

The direct determination of alogliptin benzoate (ALO) using fluorescence has not yet been accomplished because ALO cannot fluoresce naturally. Accordingly, it should be derivatized first with a fluorogenic reagent to enhance the sensitivity required for its bioanalysis. This method is the first spectrofluorimetric assay for ALO quantification exploiting the nucleophilic nature of its amino group to react with 4-chloro-7-nitrobenzofurazan (NBD-Cl) in borate buffer at pH 8.5 to produce a strong fluorescent compound that is excited at and emits at wavelengths 470 and 527 nm, respectively. Experimental variables concerning the conditions of reaction and fluorogenic intensity were carefully investigated and optimized. Linearity was from 1-250 ng ml -1 with a lower detection limit of 0.29 ng ml -1 and a lower quantification limit of 0.88 ng ml -1 . Validation of the current study was accomplished with mean per cent recovery of 100.62 ± 1.59 in tablets and 99.86 ± 0.82 in human plasma. Furthermore, the current method has been utilized in the bioanalysis of ALO in real rat plasma after oral administration with a simple specimen preparation. The developed method has proven to be a promising alternative method for ALO analysis in bioequivalence studies., (© 2019 John Wiley & Sons, Ltd.)

Rifampicin is a common antibiotic used in human and veterinary medicine to treat tuberculosis and other diseases caused by numerous pathogenic bacteria. However, the excessive or improper use of rifampicin usually leads to a series of problems, including bacterial resistance, excessive drug-resistance and water pollution. Thus, it is of great importance to develop selective and sensitive assays for monitoring rifampicin in biological systems. In this study, we designed a fluorescence "turn-off" strategy for the trace detection of rifampicin based on a glutathione-stabilized copper nanoclusters (GSH-Cu NC) sensor. In an aqueous solution, the fluorescence of the GSH-Cu NCs at 632 nm can be quenched effectively and selectively by rifampicin due to the inner-filter effect (IFE) of fluorescence mechanism. Distinctively, this GSH-Cu NC sensor exhibited excellent fluorescence sensing capability for the trace detection of rifampicin with a very low limit of detection (LOD) of 16 pM in a wide linear range from 50 to 10 000 pM. It is not only more sensitive than the other methods previously reported for the detection of rifampicin, but also has an outstanding selectivity and strong anti-interference in complex samples. Furthermore, the as-developed GSH-Cu NCs were also successfully applied to determine rifampicin in different real samples with quantitative spike recoveries ranging from 97% to 105%.

An optical fiber nanoprobe is presented for fluorometric determination of copper(II). The method based on the use of water-dispersible AgInZnS quantum dots (QDs) deposited at the end of an optical fiber in a poly(vinyl alcohol) matrix. The fluorescnece of the QDs, best measured at excitation/emisssion wavelengths of 365/570 nm, is quenched by Cu(II) due to both static and electron transfer from the QDs to Cu(II). This is experimentally confirmed by photoluminescence and UV-vis absorption spectra, and measurement of luminescence lifetimes. The probe is highly selective and possesses a linear detection range that extends from 2.5 to 800 nM. Graphical abstractSchematic representation of an optical fiber nanoprobe based on hydrophilic AgInZnS quantum dots for fluorometric determination of copper(II). The fluorescence is quenched by Cu(II) due to static quenching and dynamic quenching. It has a detection range of 2.5-800 nM.