Search

Electronic cigarettes are a popular nicotine consumption product that have risen in popularity as an alternative to cigarettes. However, their recent meteoric rise in market size and various controversies have resulted in the analyses of e-liquid ingredients to be focused on powerful laboratory-based slow methods such as chromatography and mass spectrometry. Here we present a complementary technology based on Raman spectroscopy combined with chemometrics as a fast, inexpensive, and highly portable screening tool to detect and quantify the propylene glycol : glycerol (PG : VG) ratio and nicotine content of e-cigarette liquids. Through this, the PG : VG ratio of 20 out of 23 commercial samples was quantified to within 3% of their stated value, while nicotine was successfully quantified to within 1 mg g−1 for 16 out of 23 samples without the need for accurate knowledge of flavonoid composition. High linearity was also achieved when flavours were kept constant. Finally, the limitations of Raman spectroscopy are discussed, and potential solutions are suggested. [ABSTRACT FROM AUTHOR]

Lab-on-a-paper-based devices are promising alternatives to the existing arduous techniques for point-of-need monitoring. The present work reports an instant and facile method to produce a microfluidic paper-based analytical device (μPAD). The fabricated μPAD has been used to detect hypochlorite (OCl−) by incorporating newly synthesized chromo-fluorogenic ratiometric probes 1 and 2 into the sample reception zone. The probes showed high selectivity and fast response (<10 s) toward OCl− with an excellent linear relationship in the concentration range of 0–100 μM. The concentration-dependent fluorometric change driven by the reaction of 1@μPAD with OCl− has been monitored using gel-doc imaging systems, which is unprecedented. Digitizing the intensity of the colour solution with different mathematical models of colour has developed a straightforward method for monitoring OCl− without any interference from its competitors. 1@μPAD can detect OCl− at ∼10 times lower than the WHO recommended limit. The detection limit of 1@μPAD via a digital camera-based fluorescence technique was found to be better over digital camera-based cuvette assays. Therefore, 1@μPAD has been successfully utilized to monitor OCl− in actual environmental water samples with portability, ease of use, and sensitivity. The analytical RSD was found to be ≤3% based on fluorimetric detection using 1@μPAD. The chemodosimetric reaction between OCl− and the probe was evidenced by UV-vis and fluorescence spectroscopy, 1H NMR, and ESI-MS. The rapid response time, biocompatibility, low cytotoxicity, 100% aqueous solubility, ratiometric feature, and exclusive OCl− selectivity over other competitive ROS/RNS successfully lead to the application of the probes for bioimaging of exogenous as well as endogenous OCl− in normal cells (HEK293) and cancerous cells (HeLa). [ABSTRACT FROM AUTHOR]

Quinolone antibiotics (norfloxacin) pose a serious threat to animal and human health due to their misuse and difficulty in being broken down in surface water and food. Rapid and effective detection of norfloxacin (NOR) is essential for environmental testing and ecosystems. In this study, yttrium was coordinated with mercaptopropionic acid (MPA)-modified CdTe quantum dots (QDs) to obtain a novel fluorescence sensor Y3+@CdTe QDs for the sensitive detection of NOR. NOR can bind to Y3+ to form a complex (NOR–Y3+). This complex enhances the luminescence of NOR and blue-shifts to 423 nm. The fluorescence intensity of NOR–Y3+ at 423 nm (I423) gradually increased with increasing NOR concentration; meanwhile, the fluorescence intensity of CdTe QDs at 634 nm (I634) gradually decreased due to aggregation induction. The ratio of I423 to I634 was used for the quantitative determination of NOR. The linear range of the constructed fluorescent probes was from 1.0 to 150.0 μM, with a detection limit of 31.8 nM. CdTe QDs act as a red fluorescent background, and with the addition of NOR, the color of the system transitions from red to purple and finally blue. This method was rapid (immediate) and visual, providing a simple analysis of various actual samples (tap water, lake water, honey, milk and human serum) for NOR. [ABSTRACT FROM AUTHOR]

Besides being a luminescent material, cytidine 5′-monophosphate-capped gold nanoclusters (AuNCs@CMP) also show superior peroxidase-like activity which can promote TMB oxidation in the presence of H2O2, causing the solution to turn efficiently from pale to blue. However, the presence of perfluorooctane sulfonate (PFOS) in the above system inhibited TMB oxidation and bluing of the solution, consequently establishing a colorimetric platform of AuNCs/H2O2/TMB for PFOS determination. The results showed that it responded to PFOS over a wide range of 2.0–50 μM, with a limit of detection (LOD) as low as 150 nM. Furthermore, in-depth mechanism investigation revealed that, rather than the active site of the catalyst being occupied by PFOS, such a hypochromatic effect originated from depletion of the reactive oxygen species (ROS) by PFOS degradation, thereby also offering a unique strategy to scavenge the lethal toxicity of PFOS. In addition, the colorimetric response of AuNCs/H2O2/TMB to PFOS was extended to smartphone determination conveniently based on RGB values. Finally, the established platform was applied to PFOS determination both in soil extracts and in tap water with good recovery, which supplies a novel colorimetric platform for visual determination of PFOS in practice. The method has the advantages of being rapid, sensitive and highly selective, which highlight the design and construction of more systems for determination and elimination of lethal pollutants in environmental water. [ABSTRACT FROM AUTHOR]

Among various exosomal proteins, matrix metalloproteinases (MMPs) are a family of membrane associated endopeptidases and have been considered as potential biomarkers in liquid biopsy owing to their multiple roles in pathological processes. However, the potential of MMP14 expression (MMP14-E) and MMP14 proteolytic activity (MMP14-A) in clinical diagnosis is still not clear due to the lack of sensitive and simultaneous detection techniques. Herein, we propose a fluorescent nanosensor for the simultaneous detection of MMP14-E and MMP14-A using a spherical aptamer/peptide dual-probe strategy. The aptamer and peptide probes were sequentially immobilized on Fe3O4 magnetic nanoparticles coated with gold nanoparticles (m-AuNPs) using a disulfide linker. MMP14 can be specifically recognized by the aptamer, while the proteolytic-active MMP14 can cleave the peptide probe. While achieving simultaneous detection, the proposed sensor provides better analytical performances than traditional MMP14 sensors owing to the m-AuNP-based spherical dual-probe strategy. This sensor has been successfully applied for the detection of exosomal MMP14 from cell culture media and real serum samples. Levels of both MMP14-E and MMP14-A increase in serum from cancer patients, indicating their potential applications as biomarkers in liquid biopsy for disease diagnosis and real-time surveillance. [ABSTRACT FROM AUTHOR]

The plasmonic colorimetric biosensors are very favorable for the on-site testing and naked-eye screening of analytes from real samples, but how to realize their highly sensitive assays with simple manipulations is still a great challenge. Herein we designed a target-triggered dual cascade nucleic acid recycling strategy to amplify the assembly of a hyperbranched DNA nanostructure and thus developed a novel kanamycin colorimetric biosensing method. The first cycle arising from the aptamer recognition-triggered strand displacement reaction and its cascade cycle constructed on the catalytic reaction of two nucleases could release an output DNA to trigger the assembly of the DNA nanostructure. Based on the high capture of alkaline phosphatase at this DNA nanostructure to induce the localized surface plasmon resonance change of gold nanobipyramids (Au NBPs), an ultrasensitive colorimetric signal transduction strategy was constructed. Through the measurement of the shift of the characteristic absorption wavelength of Au NBPs, a very wide linear range from 10 fg mL−1 to 1 ng mL−1 and a very low detection limit of 1.4 fg mL−1 were obtained. Meanwhile, the obvious multicolor change of Au NBPs could be used for the visual semi-quantitative analysis of Kana residues. The whole homogeneous assay process well simplified the manipulation and also ensured the excellent repeatability. These excellent performances determine the great potential of the method for future applications. [ABSTRACT FROM AUTHOR]

The routine use of SERS as an analytical technique has been hindered by practical considerations among which the irreproducibility of its signals and the lack of robustness of its calibration. In the present work, we examine a strategy to perform quantitative SERS without the need for calibration. The method reinvests a colorimetric volumetric titration procedure to determine water hardness but involves monitoring the progression of the titration through the SERS signal of a complexometric indicator. Upon reaching the equivalence between the chelating titrant and the metal analytes, the SERS signal abruptly jumps, which conveniently serves as an end-point marker. Three mineral waters spanning divalent metal concentrations varying by a factor of 25 were successfully titrated in this way, with satisfactory accuracy. Remarkably, the developed procedure can be run in less than an hour, without laboratory-grade carrying capacity and would be relevant for field measurements. [ABSTRACT FROM AUTHOR]

Rapid on-site detection of copper(II) ions (Cu2+) with high sensitivity and selectivity is of great significance in the safety monitoring of drinking water and food. Colorimetric detection is a robust fast determination method with the main drawback of low sensitivity. Herein, we developed a colorimetric chemosensor based on a colored polymer product. Via a Cu–Fenton mechanism, 1-naphthylamine (α-NA) was oxidized by H2O2 and brownish-red poly(1-naphthylamine) (PNA) was produced. The obtained Cu2+ sensor showed a linear response from 0.05 μM to 7 μM, with a detection limit of 62 nM. Our findings expanded chromogenic reaction types for colorimetric detection. [ABSTRACT FROM AUTHOR]

Investigating effective fluorescence strategies for real-time monitoring of dipicolinic acid (DPA) is of paramount importance in safeguarding human health. Herein, we present the design of a desirable red-emissive carbon nanostructure anchoring a molecularly imprinted Er-BTC MOF as a fluorescence biosensor for the visual determination of DPA. DPA is a biomarker of Bacillus anthracis, a subcategory of serious infectious diseases and bioweapons. We introduce a paper test strip sensitized with the aforementioned nanostructure, which is integrated with online UV excitation and smartphone digital imaging, resulting in a DPA signal-off sensing platform. The proposed fluorometric visual paper-based biosensor demonstrates wide linear ranges for DPA (10–125 μM) with a LOQ and LOD of 4.32 and 1.28 μM, respectively. The designed platform exhibits impressive emission properties and adaptable surface functional groups, which confirm its desirable selective sensing capabilities against other biological molecules and DPA isomers. As a proof of concept, DPA monitoring is successfully applied to real samples of tap water and urine. This integrated selective paper-based nano-biosensor, coupled with smartphone signal recording, holds great promise for state-of-the-art practical applications including fluorometric/colorimetric detection in healthcare and environmental monitoring, food safety analysis, and point-of-care testing. [ABSTRACT FROM AUTHOR]

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which emerged as a novel pathogen in 2019. The virus is responsible for a severe acute respiratory syndrome outbreak, affecting the respiratory system of infected individuals. COVID-19 is a super amplifier of basic diseases, and the disease with basic diseases is often more serious. Controlling the spread of the COVID-19 pandemic relies heavily on the timely and accurate detection of the virus. To resolve the problem, a polyaniline functionalized NiFeP nanosheet array-based electrochemical immunosensor using Au/Cu2O nanocubes as a signal amplifier is fabricated for the detection of SARS-CoV-2 nucleocapsid protein (SARS-CoV-2 NP). Polyaniline (PANI) functionalized NiFeP nanosheet arrays are synthesized as an ideal sensing platform for the first time. PANI is coated on the surface of NiFeP by electropolymerization to enhance biocompatibility, beneficial for the efficient loading of the capture antibody (Ab1). Significantly, Au/Cu2O nanocubes possess excellent peroxidase-like activity and exhibit outstanding catalytic activity for the reduction of H2O2. Therefore, Au/Cu2O nanocubes combine with a labeled antibody (Ab2) through the Au–N bond to form labeled probes, which can effectively amplify current signals. Under optimal conditions, the immunosensor for the detection of SARS-CoV-2 NP shows a wide linear range of 10 fg mL−1–20 ng mL−1 and a low detection limit of 1.12 fg mL−1 (S/N = 3). It also exhibits desirable selectivity, repeatability, and stability. Meanwhile, the excellent analytical performance in human serum samples confirms the practicality of the PANI functionalized NiFeP nanosheet array-based immunosensor. The electrochemical immunosensor based on the Au/Cu2O nanocubes as a signal amplifier demonstrates great potential for application in the personalized point-of-care (POC) clinical diagnosis. [ABSTRACT FROM AUTHOR]

The gel-to-liquid phase transition property of a hybrid niosome, which is made with a non-ionic surfactant, span 60 (S60), and triblock copolymer L64, is effectively utilized to design a nanothermometer for temperature sensing in the physiological range (20 °C to 50 °C). The fluorescence signal of a polarity-sensitive probe, Coumarin 153, loaded into the niosome, is used as an indicator for temperature sensing. Due to its excellent temperature sensitivity and resolution, the sensor is capable of sensing temperature inside FaDu cells. [ABSTRACT FROM AUTHOR]

Highly sensitive protein biomarker detection is critical for the diagnosis of gastric cancer (GC), however the accurate and sensitive detection of low-abundance proteins in early-stage GC is still a challenge. Herein, a surface-enhanced Raman scattering frequency shift assay was performed on a developed microfluidic chip for the detection of GC protein biomarkers carcinoembryonic antigen (CEA) and vascular endothelial growth factor (VEGF). The chip is made up of three groups of parallel channels and each parallel channel consists of two reaction regions, enabling the simultaneous analysis of multiple biomarkers in multiple samples. The presence of CEA and VEGF in the sample can be captured by the 4-mercaptobenzoic acid (4-MBA)-conjugated antibody functionalized gold nano-sheet (GNS-) substrate, resulting in the Raman frequency shift. As a result, a typical Raman frequency shift of 4-MBA presented a linear relationship with the concentration of CEA and VEGF. The limit of detection (LOD) of the proposed SERS microfluidic chip reaches as low as 0.38 pg mL−1 for CEA and 0.82 pg mL−1 for VEGF. During the detection process, only one step of sample addition is involved, which eliminates the multiple reaction step-induced nonspecific adsorption and significantly increases the convenience and specificity. In addition, serum samples from GC patients and healthy subjects were tested and the results were in good agreement with the current gold-standard method ELISA, suggesting the potential application of the SERS microfluidic chip in clinical settings for early diagnosis and prognosis of GC. [ABSTRACT FROM AUTHOR]

The THermally Evaporated Spray for Engineered Uniform particulateS (THESEUS) production platform was developed to generate highly uniform mixed actinide oxide particles. The particulate synthesis platform builds on previous efforts and utilizes an aerosol-based technology to generate, calcine, characterize, and aggregate a monodisperse oxide phase particle product. In this study, particles comprised of uranium oxide, incorporated with varying compositions of thorium, were produced. Th/U test materials with 232Th concentrations between 1 ppm and 10%, ratioed to 238U, were successfully generated with in situ calcination at 600 °C and characterized by in situ aerodynamic particle size spectrometry and ex situ microanalytical methods. Populations of monodisperse particulates (geometric standard deviation – GSD < 1.15) with an average diameter near 1 μm were generatated and micro-Raman spectroscopy of individual particles identified U3O8 as the primary material phase for the range of Th/U samples analyzed. Single particle measurements and automated particle analyses by secondary ion mass spectrometry (SIMS) were performed. Uniform inter-particle elemental and isotopic homogeneity for uranium and thorium isotopes was characterized by SIMS, and a 232Th/238U relative sensitivity factor of 0.53 was determined. SIMS results demonstrated differences in the 232Th/238U profiling behavior for Th/U particulates with increased Th content (>1%). Despite the observed profiling behavior, single particle measurements of the 10% Th sample indicate inter-particle homogeneity. This work represents the first systematic study of Th/U microparticulate reference materials generated and intended for nuclear safeguards applications and serves as a demonstration of THESEUS to support a sustained capability for the production mixed-element particulate reference materials. [ABSTRACT FROM AUTHOR]

A conventional molecular assay-based point-of-care (POC) diagnostic test involves three major stages: deoxyribonucleic acid (DNA) extraction, amplification, and amplicon detection. Among these steps, DNA extraction is costly and time-consuming. Nevertheless, it is a crucial step for the identification of sensitive and specific diseases. This review summarizes the advantages and disadvantages of DNA extraction methods over the past 10 years to effectively implement POC pathogen testing in the future. The first section briefly explains the necessity of DNA extraction and molecular assays for food pathogen detection. The second section extensively discusses DNA extraction based on liquid–liquid extraction, solid-phase extraction, and electrophoretic techniques. Molecular assay-based methods and a few commercially available POC devices for the detection of foodborne pathogens are detailed in the third and fourth sections. Finally, present challenges and future perspectives for the fabrication of integrated POC devices are highlighted. [ABSTRACT FROM AUTHOR]

While there are numerous publications on laser-assisted fabrication and characterization of Pt nanoelectrodes, the exact replication of those procedures is not as straightforward as following a single recipe across laboratories. Often, the working procedures vary by day, by laser puller, or by person. Only a handful of nanoelectrode fabrication papers record their parameters, and even fewer offer troubleshooting advice. Here, we provide a step-by-step guide for laser-assisted Pt nanoelectrode fabrication using low-cost equipment including a laser puller, voltammetry, and simple microscope images captured via cell phone. We also offer solutions for common failures experienced throughout the process to guide beginners as they troubleshoot their own fabrication procedures. [ABSTRACT FROM AUTHOR]

The structure-specific endonuclease flap endonuclease 1 (FEN1) is an essential functional protein in DNA replication and genome stability, and it has been identified as a promising biomarker and drug target for multiple cancers. Herein, we develop a target-activated T7 transcription circuit-mediated multiple cycling signal amplification platform for monitoring FEN1 activity in cancer cells. In the presence of FEN1, the flapped dumbbell probe is cleaved to generate a free 5′ flap single-stranded DNA (ssDNA) with the 3′-OH terminus. The ssDNA can hybridize with the T7 promoter-bearing template probe to trigger the extension with the aid of Klenow fragment (KF) DNA polymerase. Upon the addition of T7 RNA polymerase, an efficient T7 transcription amplification reaction is initiated to produce abundant single-stranded RNAs (ssRNAs). The ssRNA can hybridize with a molecular beacon to form an RNA/DNA heteroduplex that can be selectively digested by DSN to generate an enhanced fluorescence signal. This method exhibits good specificity and high sensitivity with a limit of detection (LOD) of 1.75 × 10−6 U μL−1. Moreover, it can be applied for the screening of FEN1 inhibitors and the monitoring of FEN1 activity in human cells, holding great potential in drug discovery and clinical diagnosis. [ABSTRACT FROM AUTHOR]

Developing hollow-structure quantum dot carriers to increase quantum luminous efficiency is a creative idea for designing a novel sensor. A ratiometric hollow CdTe@H-ZIF-8/CDs@MIPs sensor was developed for the sensitive and selective detection of dopamine (DA). CdTe QDs and CDs were used as the reference signal and recognition signal, respectively, and thus showed a visual effect. MIPs provided high selectivity toward DA. The TEM image demonstrated that the sensor was a hollow structure, which could have ample opportunity to excite quantum dots to emit light through multiple light scattering through holes. In the presence of DA, the fluorescence intensity of the optimum CdTe@H-ZIF-8/CDs@MIPs was remarkably quenched by DA, achieving a linear range of 0–600 nM and a limit of detection of 12.35 nM. The developed ratiometric fluorescence sensor showed an obvious and meaningful color change with a gradual increase in DA concentration under a UV lamp. Moreover, the optimum CdTe@H-ZIF-8/CDs@MIPs was remarkably sensitive and selective in detecting DA among various analogs and showed good anti-interference ability. The HPLC method also further confirmed that CdTe@H-ZIF-8/CDs@MIPs shows good practical application prospects. [ABSTRACT FROM AUTHOR]

This paper introduces an enclosed microfluidic chip that integrates sample preparation and the chamber-based digital polymerase chain reaction (cdPCR). The sample preparation of the chip includes nucleic acid extraction and purification based on magnetic beads, which adsorb nucleic acids by moving around the reaction chambers to complete the reactions including lysis, washing, and elution. The cdPCR area of the chip consists of tens of thousands of regularly arranged microchambers. After the sample preparation processes are completed, the purified nucleic acid can be directly introduced into the microchambers for amplification and detection on the chip. The nucleic acid extraction performance and digital quantification performance of the system were examined using synthetic SARS-CoV-2 plasmid templates at concentrations ranging from 101–105 copies per μL. Further on, a simulated clinical sample was used to test the system, and the integrated chip was able to accurately detect SARS-CoV-2 virus particle samples doped with interference (saliva) with a detection limit of 10 copies per μL. This integrated system could provide a promising tool for point-of-care testing of pathogenic infections. [ABSTRACT FROM AUTHOR]

Aptamers associated with cancer targeting therapy are commonly focused on cell membrane proteins; however, the study of intracellular, particularly, nuclear proteins is limited. The nuclear phosphatase PAC1 has been reported to be a potential T cell-related immunotherapeutic target. Here, we identified an aptamer, designated as PA5, with high affinity and specificity for PAC1 through the systematic evolution of ligands by exponential enrichment (SELEX) procedure. We then developed a dual-module aptamer PAC1-AS consisting of a cell-internalizing module and a targeting module, which can recognize PAC1 in the nucleus under physiological conditions. This modularized aptamer raises the possibility of manipulating endosomes and provides insights into the exploration and development of an efficient cancer immunotherapy approach. [ABSTRACT FROM AUTHOR]

Polymerase Chain Reaction (PCR) is a critical tool for biological research investigators but recently it also has been making a significant impact in clinical, veterinary and agricultural applications. Plasmonic PCR, which employs the very efficient heat transfer of optically irradiated metallic nanoparticles, is a simple and powerful methodology to drive PCR reactions. The scalability of next generation plasmonic PCR technology will introduce various forms of PCR applications ranging from small footprint portable point of care diagnostic devices to large footprint central laboratory multiplexing devices. In a significant advance, we have introduced a real time plasmonic PCR and explored the ability of ultra-fast cycling compatible with both label-free and fluorescence-based monitoring of amplicon production. Furthermore, plasmonic PCR has been substantially optimized to now deliver a 30 cycle PCR in 54 seconds, with a detectable product. The advances described here will have an immediate impact on the further development of the use of plasmonic PCR playing a critical role in rapid point of care diagnostics. [ABSTRACT FROM AUTHOR]

Tetrahydrofuran is a relevant auxiliary molecule when storing carbon dioxide or hydrocarbons as gas hydrates. The present study demonstrates the application of in situ mid-infrared fiber-optic evanescent field absorption spectroscopy for studying the formation and dissociation of THF hydrates. Thereby, the utility of this analytical technique for providing unique molecular-level insight even under harsh environmental conditions is evidenced. [ABSTRACT FROM AUTHOR]

The fundamental ion mobility equation computes the energy-averaged collision cross section as a function of measured drift velocity, electric field strength, ion and neutral masses, and drift gas state parameters. As field strength approaches zero, in particular when the drift velocity drops below about 4% of the average ion-neutral thermal speed, the fundamental equation takes on an especially simple form because the collision frequency and average momentum transfer become indistinguishable from their thermal values. However, in modern high-performance IMS-MS instruments, ion drift velocities may be 10–50% or more of thermal speed, and analysis using the zero-field equation gives rise to erroneously large cross sections. We address this problem by developing correction factors for the zero-field equation from an improved momentum-transfer (MT) theory for ion mobility, corrected and completed herein, and from the well-known two-temperature (2T) theory. The corrected and uncorrected equations are compared by their ability to recover known hard-sphere cross sections from accurately-computed mobility data. Both MT and 2T expressions adjust for the field-driven increase in collision frequency and are noticeably superior to zero-field expression whenever the ion drift velocity is greater than ∼4% of thermal speed. The MT expression also adjusts for the mass and field dependent change in average momentum transfer, and is more accurate than the 2T first approximation whenever the mass of the ionic species is greater than about four times that of drift gas molecules, as is the case in most analytical applications of IMS coupled to MS. [ABSTRACT FROM AUTHOR]

Infrared photothermal microscopy is an infrared (IR) imaging technique that enables non-invasive, non-destructive, and label-free investigations at the sub-micrometer scale. It has been applied in various research areas targeting pharmaceutical and photovoltaic materials as well as biomolecules in living systems. Despite its potency in observing biomolecules in living organisms, its practical application for cytological research has been restricted by the deficiency of molecular information from the IR photothermal signal, due to the narrow spectral width of a quantum cascade laser that is one of the most preferred IR excitation light sources for current IR photothermal imaging (IPI) techniques. Here, we address this issue by bringing modulation-frequency multiplexing into IR photothermal microscopy for developing a two-color IR photothermal microscopy technique. We demonstrate that the two-color IPI technique can be used to obtain the IR microscopic images of two discrete IR absorption bands and to distinguish two different chemical species in live cells with a sub-micrometer spatial resolution. We anticipate that the more general multi-color IPI technique and its use for metabolic studies of live cells could be realized by extending the present modulation-frequency multiplexing method. [ABSTRACT FROM AUTHOR]

In this study, we have shown how to prepare a ternary nanocomposite (Ag2S–NiMoO4–g-C3N4) consisting of graphitic carbon nitride (g-C3N4) nanosheets, silver sulfide (Ag2S) nanocrystals, and nickel molybdate (NiMoO4) nanorods and its sensing ability to detect quercetin, a flavonoid found in many fruits and vegetables. An Ag2S–NiMoO4–g-C3N4 nanocomposite-modified screen-printed electrode (SPE) exhibited remarkable sensing performance in a quercetin (Que) concentration range of 0.005 μM–20 μM with a low detection limit of 2.7 nM. Moreover, we have aimed at improving the selectivity and sensitivity of a sensor for detecting Que by optimizing the composition of Ag2S–NiMoO4–g-C3N4, the film thickness, and the electrolyte pH. The sensor's selectivity for Que was tested in the presence of potential interferents such as ascorbic acid, citric acid, fructose, glucose, lactose, maltose, mannose, sucrose, and tyrosine. The performance of the sensor was tested on a variety of food samples, including green apple, green tea, honey, and red onion skin. [ABSTRACT FROM AUTHOR]

A dual-emitting electrochemiluminescence (ECL) immunosensor based on manganese dioxide nanoflowers (MnO2NFs) and zinc sulfide quantum dots (ZnSQDs) was constructed for the first time to sensitively detect procalcitonin (PCT) in human serum. rGO@Ag functioned not only to adsorb primary antibodies (Ab1) but also to improve the electrical conductivity of the immunosensor. The MnO2NFs and ZnSQDs in the nanocomposite, synergistically with silver nanoparticles, simultaneously functioned as cathodic ECL emitters to enhance the detection sensitivity of PCT by shortening the electron-transfer path, thereby reducing energy loss. Under the optimized experimental conditions, the ECL immunosensor was capable of quantitatively detecting PCT in the linear range of 0.1 pg mL−1 to 100 ng mL−1 and over the scanning potential range of −2.0–0 V, with a detection limit of 0.033 pg mL−1. Furthermore, the ECL immunosensor demonstrated high specificity for PCT in the presence of other competing antigens, excellent stability over 10 cycles, and excellent reproducibility, corroborating its potential for measuring PCT concentrations in clinical samples. [ABSTRACT FROM AUTHOR]

Single-benzene fluorophores are bright and the smallest fluorochromes known so far. In single-benzene fluorophores, the fluorescence is mediated by the push/pull effect of substituting groups. Despite a plethora of advantageous properties, this group of molecules has not been extensively studied for design of high-performance fluorescent sensors of catalytic or enzymatic activities. Thus, herein, new fluorescent probes based on the Tsuji–Trost reaction were developed for the selective detection of palladium and other transition metals (platinum and gold) in an aqueous/organic mixed solvent with the sensitivity down to 2.5 nM (for palladium). The relative flexibility in the synthesis of these probes allows for facile color tuning of the emitted fluorescence. In this study, we have successfully utilized a yellow emission variant for sensitive detection of palladium under cell-free conditions and in living cells, validating its possible applicability for high-throughput optical sensing of catalysts for bioorthogonal chemistry under physiological conditions. [ABSTRACT FROM AUTHOR]

Temperature governs the reactivity of a wide range of biomolecules in the cellular environment dynamically. The complex cellular pathways and molecules in solid tumors substantially produce temperature gradients in the tumor microenvironment (TME). Hence, visualization of these temperature gradients at the cellular level would give physiologically relevant spatio-temporal information about solid tumors. This study used fluorescent polymeric nano-thermometers (FPNTs) to measure the intratumor temperature in co-cultured 3D tumor spheroids. A temperature-sensitive rhodamine-B dye and Pluronic F-127 were conjugated through hydrophobic and hydrophobic interactions and then cross-linked with urea–paraformaldehyde resins to form the FPNTs. The characterization results exhibit monodisperse nanoparticles (166 ± 10 nm) with persistent fluorescence. The FPNTs exhibit a linear response with a wide temperature sensing range (25–100 °C) and are stable toward pH, ionic strength, and oxidative stress. FPNTs were utilized to monitor the temperature gradient in co-cultured 3D tumor spheroids and the temperature difference between the core (34.9 °C) and the periphery (37.8 °C) was 2.9 °C. This investigation demonstrates that the FPNTs have great stability, biocompatibility, and high intensity in a biological medium. The usage of FPNTs as a multifunctional adjuvant may demonstrate the dynamics of the TME and they may be suitable candidates to examine thermoregulation in tumor spheroids. [ABSTRACT FROM AUTHOR]

Raman spectroscopy imaging is a technique that can be adapted for intraoperative tissue characterization to be used for surgical guidance. Here we present a macroscopic line scanning Raman imaging system that has been modified to ensure suitability for intraoperative use. The imaging system has a field of view of 1 × 1 cm2 and acquires Raman fingerprint images of 40 × 42 pixels, typically in less than 5 minutes. The system is mounted on a mobile cart, it is equiped with a passive support arm and possesses a removable and sterilizable probe muzzle. The results of a proof of concept study are presented in porcine adipose and muscle tissue. Supervised machine learning models (support vector machines and random forests) were trained and they were tested on a holdout dataset consisting of 7 Raman images (10 080 spectra) acquired in different animal tissues. This led to a detection accuracy >96% and prediction confidence maps providing a quantitative detection assessment for tissue border visualization. Further testing was accomplished on a dataset acquired with the imaging probe's contact muzzle and tailored classification models showed robust classifications capabilities with specificity, sensitivity and accuracy all surpassing 95% with a support vector machine classifier. Finally, laser safety, biosafety and sterilization of the system was assest. The safety assessment showed that the system's laser can be operated safetly according to the American National Standards Institute's standard for maximum permissible exposures for eyes and skin. It was further shown that during tissue interrogation, the temperature-history in cumulative equivalent minutes at 43 °C (CEM43 °C) never exceeded a safe threshold of 5 min. [ABSTRACT FROM AUTHOR]

Dopamine (DA) plays an essential role in dopaminergic neuronal behavior and disease. However, current detection methods for discriminating the secretion of DA are hampered by the limitations of the requirement for bulky instrumentation and non-intuitive signals. Herein, we have controllably and proportionately integrated molybdenum disulfide (MoS2) with titanium dioxide (TiO2) to prepare MoS2@TiO2 nanocomposites (MoS2@TiO2 NCs) via a facile synthesis method. MoS2@TiO2 NCs with a certain reactant mass ratio have shown a significant enhancement in peroxidase-like activity with superiority of the nanocomposite structure compared to single MoS2 or natural enzyme. The method for catalyzing the decomposition of H2O2 by MoS2@TiO2 NCs and competition for hydroxyl radicals (˙OH) between the chromogenic agent and DA enable a sensitive, specific, and colorimetric DA analysis with a low detection limit of 0.194 μM and a wide linear detection range (0.8 to 100 μM). Because of the favorable detection performance, we were encouraged to explore and finally realize the visual detection of cellular DA secretion that is stimulated in a High-K+ neurocyte environment. Collectively, this method will provide a promising strategy for basic research in neuroscience with its portable, sensitive, and naked-eye detectable performance. [ABSTRACT FROM AUTHOR]

The spatiotemporal visualization of intracellular microRNA (miRNA) plays a critical role in the diagnosis and treatment of malignant disease. Although DNAzyme-based biosensing has been regarded as the most promising candidate, inefficient analytical resolution is frequently encountered. Here, we propose a bioorthogonal approach toward high-fidelity imaging of intracellular miRNA by designing a multifunctional nanoprobe that integrates MnO2 nanosheet-mediated intracellular delivery and activation by a fat mass and obesity-associated protein (FTO)-switched positive feedback. MnO2 nanosheets facilitate nanoprobe delivery and intracellular DNAzyme cofactors are released upon glutathione-triggered reduction. Meanwhile, an m6A-caged DNAzyme probe could be bioorthogonally activated by intracellular FTO to eliminate potential off-target activation. Therefore, the activated DNAzyme probe and substrate probe could recognize miRNA to perform cascade signal amplification in the initiation of the release of Mn2+ from MnO2 nanosheets. This strategy realized high-fidelity imaging of intracellular aberrant miRNA within tumor cells with a satisfactory detection limit of 9.7 pM, paving the way to facilitate clinical tumor diagnosis and prognosis monitoring. [ABSTRACT FROM AUTHOR]

A multifunctional dehydroabietic acid-based fluorescent probe (CPS) was designed and synthesized by introducing the 2,6-bis(1H-benzo[d]imidazol-2-yl)phenol fluorophore. The probe CPS could selectively recognize Cu2+, Zn2+ and ClO− ions from other analytes, and it showed fluorescence quenching behavior toward Cu2+ and a ratiometric response to Zn2+ and ClO− by changing from green fluorescence to blue and cyan, respectively. The detection limits toward Cu2+, Zn2+ and ClO− ions were 3.8 nM, 0.253 μM and 0.452 μM, respectively. In addition, CPS presented many fascinating merits, such as high selectivity, a short response time (15–20 s), a wide pH range (3–10) and high photostability. The sensing mechanisms of CPS were verified by 1H-NMR, ESI-MS, FT-IR and Job's plot methods. Meanwhile, CPS exhibited satisfactory detection performance in water samples. More importantly, the probe could be applied as a promising tool for visual bioimaging of three ions in living cells and zebrafishes. [ABSTRACT FROM AUTHOR]

The concept of digital microfluidics (DMF) enables highly flexible and precise droplet manipulation at a picoliter scale, making DMF a promising approach to realize integrated, miniaturized "lab-on-a-chip" (LOC) systems for research and clinical purposes. Owing to its simplicity and effectiveness, electrowetting-on-dielectric (EWOD) is one of the most commonly studied and applied effects to implement DMF. However, complex biomedical assays usually require more sophisticated sample handling and detection capabilities than basic EWOD manipulation. Alternatively, combined systems integrating EWOD actuators and other fluidic handling techniques are essential for bringing DMF into practical use. In this paper, we briefly review the main approaches for the integration/combination of EWOD with other microfluidic manipulation methods or additional external fields for specified biomedical applications. The form of integration ranges from independently operating sub-systems to fully coupled hybrid actuators. The corresponding biomedical applications of these works are also summarized to illustrate the significance of these innovative combination attempts. [ABSTRACT FROM AUTHOR]

Mass spectrometry (MS)-based proteomics workflows of intact protein ions have increasingly been utilized to study biological systems. These workflows, however, frequently result in convoluted and difficult to analyze mass spectra. Ion mobility spectrometry (IMS) is a promising tool to overcome these limitations by separating ions by their mass- and size-to-charge ratios. In this work, we further characterize a newly developed method to collisionally dissociate intact protein ions in a trapped ion mobility spectrometry (TIMS) device. Dissociation occurs prior to ion mobility separation and thus, all product ions are distributed throughout the mobility dimension, enabling facile assignment of near isobaric product ions. We demonstrate that collisional activation within a TIMS device is capable of dissociating protein ions up to 66 kDa. We also demonstrate that the ion population size within the TIMS device significantly influences the efficiency of fragmentation. Lastly, we compare CIDtims to the other modes of collisional activation available on the Bruker timsTOF and demonstrate that the mobility resolution in CIDtims enables the annotation of overlapping fragment ions and improves sequence coverage. [ABSTRACT FROM AUTHOR]

Exploring new highly efficient electrochemiluminescence (ECL) luminophores is a necessary condition for developing ultrasensitive ECL biosensors. Therefore, a luminescent carbon dot-based covalent organic framework (CD-COF) was prepared using aldehyde-based carbon dots (CDs) and 1,3,5-tris (4-aminophenyl) benzene (TPB). Because the CD-COF made the regular arrangement of CDs conducive to improving the ECL response, CD-COF had a higher ECL intensity and efficiency than CDs. What's more, the ECL intensity of the CD-COF/S2O82−/Bu4N+ system was about 2.98, 7.50, and 28.08 times higher than those of the CD-COF/S2O82−, CDs/S2O82− and S2O82− systems, respectively. Considering the remarkable ECL performance, the CD-COF/S2O82−/Bu4N+ system was employed combined with the CRISPR/Cas12a trans-cutting strategy to construct an "off–on" ECL biosensor for BPA detection. The proposed ECL biosensor exhibited excellent performance with a wide linear range from 1.0 × 10−14 mol L−1 to 1.0 × 10−5 mol L−1 with a low detection limit of 2.21 fM (S/N = 3) under the optimized conditions. The biosensor demonstrated that CD-COF can be used as an efficient ECL emitter, thus expanding the application field of COFs. In addition, the good stability and specificity of the biosensor enabled the rapid detection of BPA, which will provide valuable insights into promising ultrasensitive ECL biosensors. [ABSTRACT FROM AUTHOR]

The currently established DNA nanoprobes for the detection of mycotoxin from beverages have been limited by complicated sample pretreatment and uncontrollable nanoparticle flocculation in complex systems. We develop a rapid colorimetric approach for ochratoxin A (OTA) detection in Baijiu in a sample-in/"yes" or "no" answer-out fashion through target-modulated base pair stacking assembly of DNA-functionalized gold nanoparticles (DNA–AuNPs). The colorimetric signification of OTA relies on the competition of OTA with the AuNP surface-grafted DNA in binding with an OTA-targeted aptamer. The specific recognition of OTA by the aptamer prevents DNA duplex formation on the AuNP surface, thereby inhibiting the base pair stacking assembly of the DNA–AuNPs and giving rise to a "turn-on" color. By further suppressing DNA hybridization using a bulged loop design and an alcohol solution, the DNA–AuNPs exhibit an improved reproducibility for OTA sensing while maintaining excellent susceptivity to OTA. A detection limit of 88 nM was achieved along with high specificity towards OTA, which is lower than the maximum tolerated level of OTA in foodstuffs defined by countries worldwide. The entire reaction time, avoiding sample pretreatment, is less than 17 min. The DNA–AuNPs with anti-interference features and sensitive "turn-on" performance promise convenient on-site detection of mycotoxin from daily beverages. [ABSTRACT FROM AUTHOR]

In 2022, the outbreak of the monkeypox virus occurred in many non-endemic countries, and the World Health Organization (WHO) assessed that this outbreak was "atypical". The establishment of a rapid and effective assay that can be used for the early diagnosis of monkeypox virus infection is crucial for outbreak prevention and control. In this study, the monkeypox virus A29 protein and the homologous vaccinia virus A27 protein and cowpox virus 162 protein were expressed in Escherichia coli BL21 for screening. We synthesized the monkeypox virus A2917–49 peptide as the immunogen and obtained 25 monoclonal antibodies (mAbs) against the A29 protein using mouse hybridoma techniques. Then an immunochromatographic test strip method for detecting A29 was established. The strips utilizing mAb-7C5 and 5D8 showed the best sensitivity and lowest limit of detection: 50 pg mL−1 for purified A29 and specificity tests showed that the strips did not cross-react with other orthopox viruses (vaccinia virus or cowpox virus) as well as common respiratory pathogens (SARS-CoV-2, influenza A and influenza B). Therefore, this method can be used for early and rapid diagnosis of monkeypox virus infection by antigen detection. [ABSTRACT FROM AUTHOR]

In many applications, the main limitation of X-ray absorption methods is that the signals measured are a function of the attenuation coefficient, which tells us almost nothing about the chemical or crystallographic nature of objects under inspection. To calculate fundamental crystallographic parameters requires the measurement of diffracted photons from a sample. Standard laboratory diffraction methods have been refined for well over a century and provide 'gold standard' structural models for well-prepared samples and single crystals but have little applicability for thick heterogeneous samples as demanded by many screening applications. We present a new high-energy X-ray diffraction probe, which in comparison with previous depth-resolving hollow beam techniques, requires a single beam, point detector and a simple swept aperture to resolve sample signatures at unknown locations within an inspection space. We perform Monte Carlo simulations to support experiments on both single- and multiple-material localisation and identification. The new probe is configured and tested using low-cost commercial components to provide a rapid and cost-effective solution for applications including explosives detection, process control and diagnostics. [ABSTRACT FROM AUTHOR]

DNA damage, such as DNA lesions and strand breaks, impairs normal cell functions and failure in the DNA repair process could lead to gene mutation, cell apoptosis and disease occurrence. p53 is a tumor suppressor and DNA-binding protein, and DNA damage might affect their interaction and the subsequent p53 function. Herein, real-time monitoring of DNA damage and repair processes through DNA–p53 protein interaction was performed by surface plasmon resonance (SPR). The target DNA with consecutive pyrimidine nucleobases was first damaged upon UVC (254 nm) irradiation and then photoenzymatically repaired under UVA (365 nm) irradiation. The as-formed double-stranded (ds) DNA between probe DNA and normal, damaged or repaired target DNA was immobilized on the sensor chips, followed by the injection of p53 protein. By measuring the SPR signals under different cases, the DNA damage and repair processes could be conveniently monitored. The SPR signals were inversely proportional to the UVC doses ranging from 0.021 to 1.26 kJ m−2, providing a viable means for the quantification of the DNA damage level. The binding affinity between p53 and the dsDNA formed upon the hybridization of probe DNA and normal, damaged, or photoenzymatically repaired target DNA was estimated. This is the first report on measuring the equilibrium dissociation constant (KD) between the p53 protein and the dsDNA with photodamaged or repaired target sequences. The sensing strategy by SPR thus opens a new avenue for real-time measurement of the DNA damage and the repair processes. [ABSTRACT FROM AUTHOR]

DNA-based electrochemical sensors use redox reporters to transduce affinity events into electrical currents. Ideally, such reporters must be electrochemically reversible, chemically stable for thousands of redox cycles, and tolerant to changing chemical environments. Here we report the first use of an Os(II / III) complex in DNA-based sensors, which undergoes pH-insensitive electron transfer with 35% better operational stability relative to the benchmark methylene blue, making it a promising reporter for continuous molecular monitoring applications where pH fluctuates with time. [ABSTRACT FROM AUTHOR]