Fluorescence-based Biosensor Research Articles

Two dimensional alkaline earth metal sensors (2D-AEMS) of fluorescent strontium sulfide nanosheets for neurotransmitter drug detection via photo induced electron transfer (PIET)

A new sensing platform has been introduced that provides a powerful solution for fluorescence-based biosensors using photoluminescent nanosheets (NS) using the novel two dimensional alkaline earth metal sensors (2D-AEMS). We have synthesized two-dimensional (2D) fluorescent strontium sulfide (SrS) NS using deep eutectic solvent (DES) as green solvent media by a hydrothermal method. The resulting product of 2D SrS NS to enhance the fluorescence intensity was achieved successfully followed by probe ultrasonication. The optical properties of SrS NS were studied by UV–visible and photoluminescence (PL) spectroscopy. The 2D SrS NS showed a blueish-green fluorescence optimized at λex320 nm/λem390 nm and a quantum yield of 38.6% was calculated. Under optimal conditions, the fluorescent SrS NS effectively detected noradrenaline (NA) by PIET-based fluorescence quenching and wavelength shifts were observed. Our proposed 2D-AEMS of 2D SrS NS fluorescence intensity was quenched in a wide linear range from 1 to 300 µM, with a limit of detection (LOD = 3*3SD/S) of 0.047 µM. The 2D-AEMS (fluorescent SrS NS) was applied to the determination of NA in human urine samples, with good recovery ranging from 98.7-100.08%. Also, the SrS NS fluorescence quenching mechanism in the detection of NA was investigated by zeta potential analysis, UV analysis, and dynamic light scattering (DLS). Our proposed 2D SrS NS fluorescence nanomaterials stand as an innovative platform for generating fluorescence sensors, with extensive potential applications in medical, biological, and life science fields, designed to replace traditional dye fluorescence in the near future.

Detection of Cadmium(II) in Aquatic Products Using a Rolling-Circle Amplification-Coupled Ratio Fluorescent Probe Based on an Aptamer-Peptide Conjugate.

The existing aptamers for cadmium (Cd2+), the common toxic heavy metal contaminant in food, cannot meet the requirements for detecting Cd2+ in rapid detection methods. In previous work, we found that coupling aptamer-peptide conjugates (APCs) with peptides and aptamers can provide a less disruptive method with a significantly improved affinity. Moreover, we found that the spatial conformation of aptamers and peptides is crucial for obtaining proper affinity in APC. Therefore, we describe a simple design strategy to obtain a series of APCs with different affinities by designing peptide orientations (N-terminal, C-terminal). The best affinity was found for APC(C1-N) with a binding constant (Ka) of 2.23 × 106 M-1, indicating that the APC(C1-N) affinity was significantly increased by 829.17% over aptamer. Finally, a rolling-circle amplification (RCA)-coupled ratio fluorescence-based biosensor for Cd2+ detection was established with a detection limit of 0.0036 nM, which has great potential for practical aquatic product detection.

Enhancing 3D DNA Walker-Induced CRISPR/Cas12a Technology for Highly Sensitive Detection of ExomicroRNA Associated with Osteoporosis.

Exosomal microRNAs (exomiRNAs) have emerged as promising biomarkers for the early clinical diagnosis of osteoporosis. However, their limited abundance and short length in peripheral blood present significant challenges for the accurate detection of exomiRNAs. Herein, we have designed and implemented an efficacious fluorescence-based biosensor for the highly sensitive detection of exomiRNA associated with osteoporosis, leveraging the enhancing 3D DNA walker-induced CRISPR/Cas12a technology. The engineered DNA walker is capable of efficiently transforming target exomiRNA into amplifying DNA strands, thereby enhancing the sensitivity of the developed biosensor. Concurrently, the liberated DNA strands serve as activators to trigger Cas12a trans-cleavage activity, culminating in a significantly amplified fluorescent signal for the highly sensitive detection of exomiRNA-214. Under optimal conditions, the devised technology demonstrated the capacity to detect target exomiRNA-214 at concentrations as low as 20.42 fM, encompassing a wide linear range extending from 50.0 fM to 10.0 nM. Moreover, the fluorescence-based biosensor could accurately differentiate between healthy individuals and osteoporosis patients via the detection of exomiRNA-214, which was in agreement with RT-qPCR results. As such, this biosensing technology offers promise as a valuable tool for the early diagnosis of osteoporosis.

Enhancement of Photoluminescence Properties via Polymer Infiltration in a Colloidal Photonic Glass

Photonic glasses (PGs) based on the self-assembly of monosized nanoparticles can be an effective tool for realizing disordered structures capable of tailoring light diffusion due to the establishment of Mie resonances. In particular, the wavelength position of these resonances depends mainly on the morphology (dimension) and optical properties (refractive index) of the building blocks. In this study, we report the fabrication and optical characterization of photonic glasses obtained via a self-assembling technique. Furthermore, we have demonstrated that the infiltration of these systems with a green-emitting polymer enhances the properties of the polymer, resulting in a large increase in its photoluminescence quantum yield and a 3 ps growing time of the photoluminescence time decay Finally, the development of the aforementioned system can serve as a suitable low-cost platform for the realization of lasers and fluorescence-based bio-sensors.

Fluorescent-Based Neurotransmitter Sensors: Present and Future Perspectives.

Neurotransmitters (NTs) are endogenous low-molecular-weight chemical compounds that transmit synaptic signals in the central nervous system. These NTs play a crucial role in facilitating signal communication, motor control, and processes related to memory and learning. Abnormalities in the levels of NTs lead to chronic mental health disorders and heart diseases. Therefore, detecting imbalances in the levels of NTs is important for diagnosing early stages of diseases associated with NTs. Sensing technologies detect NTs rapidly, specifically, and selectively, overcoming the limitations of conventional diagnostic methods. In this review, we focus on the fluorescence-based biosensors that use nanomaterials such as metal clusters, carbon dots, and quantum dots. Additionally, we review biomaterial-based, including aptamer- and enzyme-based, and genetically encoded biosensors. Furthermore, we elaborate on the fluorescence mechanisms, including fluorescence resonance energy transfer, photon-induced electron transfer, intramolecular charge transfer, and excited-state intramolecular proton transfer, in the context of their applications for the detection of NTs. We also discuss the significance of NTs in human physiological functions, address the current challenges in designing fluorescence-based biosensors for the detection of NTs, and explore their future development.

Carbon Quantum Dots Coupled Au Nanoparticle as Fluorescence-Based DNA Biosensors for Dengue Virus Detection

This study introduces a novel DNA biosensor probe comprising carbon quantum dots (CQDs) derived from palm kernel shell biomass and gold nanoparticles (AuNPs) synthesized via the citrate reduction method. The CQDs were doped with ethylenediamine using a hydrothermal process employing a one-pot synthesis method in an autoclave batch reactor. The resulting CQDs exhibited exceptional photoluminescent (PL) properties, with an excitation wavelength of 360 nm and an emission wavelength of 430 nm. Transmission electron microscope (TEM) images showed the average particle sizes of the CQDs and AuNPs to be 2 nm and 15 nm, respectively. Carboxylic acid-modified CQDs were coupled to amine-modified ssDNA (PA) to construct the biosensor through the amine coupling technique. The AuNPs were modified through thiol coupling with Rhodamine B, L-cysteine, and thiol-modified ssDNA (PT). Both PA and PT probes were designed to complement the DEN-3 virus oligonucleotide. CQDs acted as fluorophores and energy donors in the biosensor, while the AuNPs functioned as nanoquenchers of fluorophores and energy acceptors. The resulting probe pair, CQDs-PA, and AuNPs-PT demonstrated remarkable Förster resonance energy transfer (FRET) and exhibited fluorescence turn-on upon titration with DEN-3. The biosensor displayed excellent sensitivity with a logarithmic calibration equation of 5.22LogC + 20.79 (R2 = 0.979), covering a linear range of 0.001 nM to 100 nM. The limit of detection (LOD) was determined to be 1.57 ± 0.71 nM. This innovative DNA biosensor, incorporating CQDs and AuNPs, holds promising potential for sensitive and specific detection of the DEN-3 virus.

Biosensor Guided Polyketide Synthases Engineering for Optimization of Domain Exchange Boundaries

Type I modular polyketide synthases (PKSs) are multi-domain enzymes functioning like assembly lines. Many engineering attempts have been made for the last three decades to replace, delete and insert new functional domains into PKSs to produce novel molecules. However, inserting heterologous domains often destabilize PKSs, causing loss of activity and protein misfolding. To address this challenge, here we develop a fluorescence-based solubility biosensor that can quickly identify engineered PKSs variants with minimal structural disruptions. Using this biosensor, we screen a library of acyltransferase (AT)-exchanged PKS hybrids with randomly assigned domain boundaries, and we identify variants that maintain wild type production levels. We then probe each position in the AT linker region to determine how domain boundaries influence structural integrity and identify a set of optimized domain boundaries. Overall, we have successfully developed an experimentally validated, high-throughput method for making hybrid PKSs that produce novel molecules.

Within-Mice Comparison of Microdialysis and Fiber Photometry-Recorded Dopamine Biosensor during Amphetamine Response.

A fundamental concept in neuroscience is the transmission of information between neurons via neurotransmitters, -modulators, and -peptides. For the past decades, the gold standard for measuring neurochemicals in awake animals has been microdialysis (MD). The emergence of genetically encoded fluorescence-based biosensors, as well as in vivo optical techniques such as fiber photometry (FP), has introduced technologically distinct means of measuring neurotransmission. To directly compare MD and FP, we performed concurrent within-animal recordings of extracellular dopamine (DA) in the dorsal striatum (DS) before and after administration of amphetamine in awake, freely behaving mice expressing the dopamine sensor dLight1.3b. We show that despite temporal differences, MD- and FP-based readouts of DA correlate well within mice. Down-sampling of FP data showed temporal correlation to MD data, with less variance observed using FP. We also present evidence that DA fluctuations periodically reach low levels, and naïve animals have rapid, predrug DA dynamics measured with FP that correlate to the subsequent pharmacodynamics of amphetamine as measured with MD and FP.

Computational study of 2D photonic crystal based biosensor for SARS-COV-2 detection

A computational study to design a 2D-photonic crystal (PC) structure with a fluorescence-based biosensor has been demonstrated for the detection of the severe acute respiratory syndrome corona virus 2 (SARS-COV-2) virus in the lungs. The proposed sensor can detect the different concentrations of the virus without any pretreatment of the sample. The virus detection is performed by measuring the mid-gap wavelength from the dispersion diagram and a redshift in the mid-gap wavelength has been observed as the concentration of virus increases in the lung tissue. The plane wave expansion method is used to determine the dispersion diagram of the proposed PC. The interaction of incident light with the proposed PC-based biosensor has been analyzed to evaluate the shift in the mid-gap wavelength. A maximum sensitivity of about 1459.3 nm/RIU is obtained for r/a = 0.45 with a mid-gap wavelength shift of 145.93 nm at = 1.49 concentration of SARS-COV-2. Moreover, a very small detection time has been observed with the proposed device as compared to conventional methods. This study provides a simple process to detect the presence of a virus within a short period and could be helpful in the development of a direct and easy-to-use portable detection kit in the future.

Photonic Crystal Enhanced Fluorescence: A Review on Design Strategies and Applications.

Nanoscale fluorescence emitters are efficient for measuring biomolecular interactions, but their utility for applications requiring single-unit observations is constrained by the need for large numerical aperture objectives, fluorescence intermittency, and poor photon collection efficiency resulting from omnidirectional emission. Photonic crystal (PC) structures hold promise to address the aforementioned challenges in fluorescence enhancement. In this review, we provide a broad overview of PCs by explaining their structures, design strategies, fabrication techniques, and sensing principles. Furthermore, we discuss recent applications of PC-enhanced fluorescence-based biosensors incorporated with emerging technologies, including nucleic acids sensing, protein detection, and steroid monitoring. Finally, we discuss current challenges associated with PC-enhanced fluorescence and provide an outlook for fluorescence enhancement with photonic-plasmonics coupling and their promise for point-of-care biosensing as well monitoring analytes of biological and environmental relevance. The review presents the transdisciplinary applications of PCs in the broad arena of fluorescence spectroscopy with broad applications in photo-plasmonics, life science research, materials chemistry, cancer diagnostics, and internet of things.

Optical Biosensors and Their Applications for the Detection of Water Pollutants

The correct detection and quantification of pollutants in water is key to regulating their presence in the environment. Biosensors offer several advantages, such as minimal sample preparation, short measurement times, high specificity and sensibility and low detection limits. The purpose of this review is to explore the different types of optical biosensors, focusing on their biological elements and their principle of operation, as well as recent applications in the detection of pollutants in water. According to our literature review, 33% of the publications used fluorescence-based biosensors, followed by surface plasmon resonance (SPR) with 28%. So far, SPR biosensors have achieved the best results in terms of detection limits. Although less common (22%), interferometers and resonators (4%) are also highly promising due to the low detection limits that can be reached using these techniques. In terms of biological recognition elements, 43% of the published works focused on antibodies due to their high affinity and stability, although they could be replaced with molecularly imprinted polymers. This review offers a unique compilation of the most recent work in the specific area of optical biosensing for water monitoring, focusing on both the biological element and the transducer used, as well as the type of target contaminant. Recent technological advances are discussed.

Carbon-Based Fluorescent Nano-Biosensors for the Detection of Cell-Free Circulating MicroRNAs.

Currently, non-communicable diseases (NCDs) have emerged as potential risks for humans due to adopting a sedentary lifestyle and inaccurate diagnoses. The early detection of NCDs using point-of-care technologies significantly decreases the burden and will be poised to transform clinical intervention and healthcare provision. An imbalance in the levels of circulating cell-free microRNAs (ccf-miRNA) has manifested in NCDs, which are passively released into the bloodstream or actively produced from cells, improving the efficacy of disease screening and providing enormous sensing potential. The effective sensing of ccf-miRNA continues to be a significant technical challenge, even though sophisticated equipment is needed to analyze readouts and expression patterns. Nanomaterials have come to light as a potential solution as they provide significant advantages over other widely used diagnostic techniques to measure miRNAs. Particularly, CNDs-based fluorescence nano-biosensors are of great interest. Owing to the excellent fluorescence characteristics of CNDs, developing such sensors for ccf-microRNAs has been much more accessible. Here, we have critically examined recent advancements in fluorescence-based CNDs biosensors, including tools and techniques used for manufacturing these biosensors. Green synthesis methods for scaling up high-quality, fluorescent CNDs from a natural source are discussed. The various surface modifications that help attach biomolecules to CNDs utilizing covalent conjugation techniques for multiple applications, including self-assembly, sensing, and imaging, are analyzed. The current review will be of particular interest to researchers interested in fluorescence-based biosensors, materials chemistry, nanomedicine, and related fields, as we focus on CNDs-based nano-biosensors for ccf-miRNAs detection applications in the medical field.

Carbon quantum dots@metal–organic framework based catalytic nucleic acid fluorescent system for highly sensitive and selective detection of Pb2+ in aqueous solutions

Accumulation of heavy metal ions in the ecosystem has become a major concern due to their adverse impacts on animals, humans, and aquatic habitats. The development of a rapid and portable sensing system is important for the prompt detection and proper management of such pollutants. Herein, we have designed a fluorescence-based biosensor for the selective and sensitive detection of Pb2+ ions using a DNAzyme system that is active only in the presence of lead (II) ions (Pb2+). The developed nanoprobe relies on two major components: (i) boron and nitrogen carbon dots (BNCDs)-doped carboxyl functionalized-terbium metal-organic framework (COOH-Tb MOF) as a fluorescent tag and (ii) quencher-modified catalytic NH3-GR5 DNAzyme as a bioreceptor molecule. The fluorescent tag (BNCDs/MOF) exhibits dual fluorescence with emission peaks located in the regions of blue and green. In the absence of Pb2+ ions, this hybridization undergoes reduced emission intensity because of the overlap in fluorescence emission between BNCDs@Tb-MOF and quenchers. However, as the catalytic core of the DNAzyme strand is activated in the presence of Pb2+ ions, the fluorescent emission of BNCDs/Tb-MOF resumes with the cleavage of quencher-tagged substrate strand. Here, the release of a shorter oligo sequence effectively increases the intensity of the proposed novel biosensor to realize low level detection of Pb2+ (e.g., to 0.96 ppb in a wide detection range from 2 to 1000 nM). The establishment of this novel biosensing approach is expected to offer new insights into rapid, selective, and sensitive detection of major pollutants for food and environmental safety.

Upconversion nanoparticle-based aptasensor for rapid and ultrasensitive detection of Staphylococcus aureus by low-speed centrifugation.

Opportunistic foodborne pathogens such as Staphylococcus aureus (S. aureus) can cause a wide variety of threats to public health. There is an urgent clinical need for a fast, simple, low-cost, and sensitive method. Here, we designed a fluorescence-based aptamer biosensor (aptasensor) for S. aureus detection using core-shell structured upconversion nanoparticles (CS-UCNPs) as a beacon. A S. aureus-specific aptamer was modified on the surface of CS-UCNPs for binding pathogens. The S. aureus bound to CS-UCNPs can then be isolated from the detection system by simple low-speed centrifugation. Thus, an aptasensor was successfully established for the detection of S. aureus. The fluorescence intensity of CS-UCNPs correlated with the concentration of S. aureus within the range of 6.36 × 102 to 6.36 × 108 CFU mL-1, resulting in the detected limit of S. aureus being 60 CFU mL-1. The aptasensor performed well in real food samples (milk) with a detection limit of 146 CFU mL-1 for S. aureus. Furthermore, we applied our aptasensor in chicken muscles for S. aureus detection, and compared it with the plate count gold standard method. There was no significant difference between our aptasensor and the plate count method within the detected limit, while the time for the aptasensor (0.58 h) was shorter than that of the plate count method (3-4 d). Therefore, we succeeded in the design of a simple, sensitive and fast CS-UCNPs aptasensor for S. aureus detection. This aptasensor system would have the potential for the detection of a wide range of bacterial species by switching the corresponding aptamer.

Use of biosensors for rapid and sensitive detection of pesticides in food samples for food safety chemical risk assessment.

The utility of pesticides in the agricultural field is unquestionable, but at the same time pesticide use presents serious hazards to the environment and the human health. For that reason, detection of pesticides and their biotransformation products in food is of utmost importance. According to previous studies, esterase-based biosensors have been proposed as a viable and efficient solution for the detection of organophosphate pesticides. In this project, a double mutant of the thermostable esterase-2 (EST2) from Alicyclobacillus acidocaldarius was studied as a potential biosensor, for its ability to detect residual amounts of pesticides. Initial characterisation of the enzyme was performed, that included determination of optimal pH, thermophilicity, as well as kinetic analysis. Subsequently, the enzyme was studied by enzymatic activity assays with and without the presence of various organophosphate compounds. The effect of the organophosphates on the enzymatic activity was measured and complete inhibition of the enzyme was observed after incubation with paraoxon. These experiments were followed by an additional method involving labelling of the enzyme with a fluorescent probe. In this case, the effect of different pesticides on the EST2 enzyme was monitored by measuring the fluorescence quenching upon addition to the enzyme. Fourteen compounds were screened with this method and significant fluorescence quenching was observed in the presence of paraoxon and methyl-paraoxon when used in equimolar amounts with the enzyme in the range of nanomolar. This biosensor has been also used to test the presence of pesticides in real food samples, like fruits and juices. This research represents a starting point to develop effective fluorescence-based biosensors aiming at the screening of mutants with different pesticide selectivity profiles. The use of this enzyme-based biosensor can have applications in the field of food traceability as well as environmental monitoring, to control the presence of toxic chemicals, in particular organophosphate pesticides.

Amplification-free nucleic acid detection with a fluorescence-based waveguide biosensor

Early detection of pathogens using nucleic acids in clinical samples often requires sensitivity at the single-copy level, which currently necessitates time-consuming and expensive nucleic acid amplification. Here, we describe 1) a redesigned flow cell in the shape of a trapezoid-subtracted geometric stadium, and 2) modified experimental procedures that allow for the measurement of sub-attomolar analytes in microliter quantities on a fluorescence-based waveguide biosensor. We verified our instrumental sensitivity with a 200-μL sample of a fluorescent streptavidin conjugate at 100 zM (100 zeptomolar, or 100·10−21 mol L−1) and theoretically explored the applicability of this modified sensing platform in a sandwich immunoassay format using a Langmuir adsorption model. We present assays that demonstrate specific detection of synthetic influenza A DNA (in buffer) and RNA (in saliva) oligonucleotides at the single-copy level (200 μL at 10 zM) using a fluorescent molecular beacon. Lastly, we demonstrate detection of isolated genomic influenza A RNA at a clinically relevant concentration. This work constitutes a sensitivity improvement of over twelve orders of magnitude compared to our previous nucleic acid detection work, illustrating the significant enhancements that can be gained with optimized experimental design.

The Utilization of Tunable Transducer Elements Formed by the Manipulation of Magnetic Beads with Different Sizes via Optically Induced Dielectrophoresis (ODEP) for High Signal-to-Noise Ratios (SNRs) and Multiplex Fluorescence-Based Biosensing Applications.

Magnetic beads improve biosensing performance by means of their small volume and controllability by magnetic force. In this study, a new technique composed of optically induced dielectrodphoresis (ODEP) manipulation and image processing was used to enhance the signal-to-noise ratio of the fluorescence for stained magnetic beads. According to natural advantages of size-dependent particle isolation by ODEP manipulation, biomarkers in clinical samples can be easily separated by different sizes of magnetic beads with corresponding captured antibodies, and rapidly distinguished by separated location of immunofluorescence. To verify the feasibility of the concept, magnetic beads with three different diameters, including 21.8, 8.7, and 4.2 μm, were easily separated and collected into specific patterns in the defined target zone treated as three dynamic transducer elements to evaluate fluorescence results. In magnetic beads with diameter of 4.2 μm, the lowest signal-to-noise ratio between stained and nonstained magnetic beads was 3.5. With the help of ODEP accumulation and detection threshold setting of 32, the signal-to-noise ratio was increased to 77.4, which makes this method more reliable. With the further optimization of specific antibodies immobilized on different-size magnetic beads in the future, this platform can be a potential candidate for a high-efficiency sensor array in clinical applications.

Recent advances in nanotechnology-enabled biosensors for detection of exosomes as new cancer liquid biopsy.

Cancer liquid biopsy detects circulating biomarkers in body fluids, provides information that complements medical imaging and tissue biopsy, allows sequential monitoring of cancer development, and, therefore, has shown great promise in cancer screening, diagnosis, and prognosis. Exosomes (also known as small extracellular vesicles) are cell-secreted, nanosized vesicles that transport biomolecules such as proteins and RNAs for intercellular communication. Exosomes are actively involved in cancer development and progression and have become promising circulating biomarkers for cancer liquid biopsy. Conventional exosome characterization methods such as quantitative reverse transcription polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA) are limited by low sensitivity, tedious process, large sample volume, and high cost. To overcome these challenges, new biosensors have been developed to offer sensitive, simple, fast, high throughput, low sample consumption, and cost-effective detection of exosomal biomarkers. In this review, we summarized recent advances in nanotechnology-enabled biosensors that detect exosomal RNAs (both microRNAs and mRNAs) and proteins for cancer screening, diagnosis, and prognosis. The biosensors were grouped based on their sensing mechanisms, including fluorescence-based biosensors, colorimetric biosensors, electrical/electrochemical biosensors, plasmonics-based biosensors, surface-enhanced Raman spectroscopy (SERS)-based biosensors, and inductively coupled plasma mass spectrometry (ICP-MS) and photothermal biosensors. The future directions for the development of exosome-based biosensors were discussed.

Development of a fluorescence-based DNAzyme biosensor to detect Pb2+ in tobacco leaf extracts for cleaner crop production

Lead ions (Pb2+) are widespread contaminants that threaten human health and enter the human body mainly through the consumption of crop plants grown on Pb2+-contaminated soil. The traditional methods used to monitor the Pb2+ content of plants are sensitive and accurate; however, there is still an urgent need to develop screening methods with high sensitivity and reliability to rapidly monitor Pb2+ from plant samples with a higher throughput by adapting simple extraction methods. Here, we developed a series of fluorescence-based Pb2+ biosensors by fusing DNAzymes with tetrahedral DNA nanostructures and demonstrated the ability of these biosensors to detect Pb2+ in plant extracts. We first fused one DNAzyme with the A-probe of the tetrahedral DNA nanostructure. The substrate strand of the DNAzyme, which contains a ribonucleotide at its center, is cleaved upon Pb2+ binding, resulting in the release of the FAM fluorophore and the production of a fluorescence signal. The biosensors showed great sensitivity and selectivity. The sensitivity of the biosensor was further improved by fusing four DNAzymes to the tetrahedral DNA nanostructure and using Alexa488 as the fluorophore, which has greater quantum yield than FAM. Remarkably, the improved biosensors were able to detect Pb2+ in plant extracts. Thus, the Pb2+ biosensors developed in this study exhibit great potential for the identification and tracking of polluted regions by rapidly monitoring Pb2+ levels in plants grown therein and facilitating cleaner crop production.

Deep Learning-Based Sensor Array: 3D Fluorescence Spectra of Gold Nanoclusters for Qualitative and Quantitative Analysis of Vitamin B6 Derivatives.

Vitamin B6 derivatives (VB6Ds) are of great importance for all living organisms to complete their physiological processes. However, their excess in the body can cause serious problems. What is more, the qualitative and quantitative analysis of different VB6Ds may present significant challenges due to the high similarity of their chemical structures. Also, the transfer of deep learning model from one task to a similar task needs to be present more in the fluorescence-based biosensor. Therefore, to address these problems, two deep learning models based on the intrinsic fingerprint of 3D fluorescence spectra have been developed to identify five VB6Ds. The accuracy ranges of a deep neural network (DNN) and a convolutional neural network (CNN) were 94.44-97.77% and 97.77-100%, respectively. After that, the developed models were transferred for quantitative analysis of the selected VB6Ds at a broad concentration range (1-100 μM). The determination coefficient (R2) values of the test set for DNN and CNN were 93.28 and 97.01%, respectively, which also represents the outperformance of CNN over DNN. Therefore, our approach opens new avenues for qualitative and quantitative sensing of small molecules, which will enrich fields related to deep learning, analytical chemistry, and especially sensor array chemistry.