Bioinspired Copolymers Based Nose/Tongue-Mimic Chemosensor for Label-Free Fluorescent Pattern Discrimination of Metal Ions in Biofluids

Room temperature cost-effective synthesis of carbon quantum dots for fluorescence pattern recognition of metal ions

Herein, a type of low-consuming carbon quantum dot (CD) has been synthesized at room temperature in just 45 minutes via Schiff base reaction between o-phthalaldehyde (OPA) and polyethyleneimine (PEI). These CDs are pH-dependent, so a novel label-free florescent sensor array can be constructed by utilizing buffers with various pH levels, which leads to distinctive fluorescence response patterns upon being challenged with metal ions for their pattern recognition. The results demonstrate that large-scale detection of metal ions can be achieved with as little as 3 types of sensors. Additionally, the sensors are able to discriminate between various metal ion concentrations and mixtures of different metal ions. The technique demonstrates potential uses in water quality monitoring by promising straightforward, quick, sensitive, and potent discrimination of metal ions.

Integrated Smart Gas Tracking Device with Artificially Tailored Selectivity for Real-Time Monitoring Food Freshness

The real-time monitoring of food freshness in refrigerators is of significant importance in detecting potential food spoiling and preventing serious health issues. One method that is commonly reported and has received substantial attention is the discrimination of food freshness via the tracking of volatile molecules. Nevertheless, the ambient environment of low temperature (normally below 4 °C) and high humidity (90% R.H.), as well as poor selectivity in sensing gas species remain the challenge. In this research, an integrated smart gas-tracking device is designed and fabricated. By applying pump voltage on the yttria-stabilized zirconia (YSZ) membrane, the oxygen concentration in the testing chamber can be manually tailored. Due to the working principle of the sensor following the mixed potential behavior, distinct differences in sensitivity and selectivity are observed for the sensor that operated at different oxygen concentrations. Typically, the sensor gives satisfactory selectivity to H2S, NH3, and C2H5OH at the oxygen concentrations of 10%, 30%, and 40%, respectively. In addition, an acceptable response/recovery rate (within 24 s) is also confirmed. Finally, a refrigerator prototype that includes the smart gas sensor is built, and satisfactory performance in discriminating food freshness status of fresh or semi-fresh is verified for the proposed refrigerator prototype. In conclusion, these aforementioned promising results suggest that the proposed integrated smart gas sensor could be a potential candidate for alarming food spoilage.

Perylene diimide-based sensors for multiple analyte sensing (Fe2+/H2S/ dopamine and Hg2+/Fe2+): cell imaging and INH, XOR, and encoder logic

In this report, we present our results on the recognition of multiple analytes using trisubstituted PDI-based chemosensors DNP and DNB in 50% HEPES buffered-CH₃CN solution. Upon the addition of Hg²⁺, DNB showed a decrease and increase in absorbance intensity at 560 and 590 nm, respectively, with a detection limit of 7.17 μM and bleaching of the violet color (de-butynoxy). Similarly, the addition of Fe²⁺ or H₂S to the solution of DNP or DNB resulted in ratiometric changes (A_688nm/A_560nm) with respective detection limits of 185 nM and 27.6 nM for Fe²⁺, respectively, and a color change from violet to green. However, the addition of >37 μM H₂S caused a decrease in absorbance at 688 nm with a concomitant blue shift to 634 nm. Upon the addition of dopamine, the DNP + Fe²⁺ assay showed ratiometric (A_560nm/A_688nm) changes within 10 s along with a color change from green to violet. Moreover, DNP has been successfully used for the exogenous detection of Fe²⁺ in A549 cells. Further, the multiple outputs observed with DNP in the presence of H₂S have been used to construct NOR, XOR, INH and 4-to-2 encoder logic gates and circuits.

Printed colorimetric chemosensor array on a 96-microwell paper substrate for metal ions in river water

Here, we propose a printed 96-well microtiter paper-based chemosensor array device (PCSAD) to simultaneously detect metal ions for river water assessment. Colorimetric chemosensors for metal ions have been designed based on molecular self-assembly using off-the-shelf catechol dyes and a phenylboronic acid (PBA) derivative. The colorimetric self-assembled chemosensors consisting of catechol dyes and a PBA derivative on a 96-well microtiter paper substrate demonstrated various color changes according to the disassembly of the ensembles by the addition of nine types of metal ions. An in-house-made algorithm was used to automate imaging analysis and extract color intensities at seven types of color channels from a captured digital image, allowing for rapid data processing. The obtained information-rich inset data showed fingerprint-like colorimetric responses and was applied to the qualitative and quantitative pattern recognition of metal ions using chemometric techniques. The feasibility of the 96-well microtiter PCSAD for environmental assessment has been revealed by the demonstration of a spike-and-recovery test against metal ions in a river water sample.

PDA-PEI-Copolymerized Nanodots with Tailorable Fluorescence Emission and Quenching Properties for the Sensitive Ratiometric Fluorescence Sensing of miRNA in Serum

Dopamine and polyethyleneimine (PEI) copolymerized nanodots (PDA-PEI nanodots) with both fluorescence emission and quenching features were synthesized by a simple one-step reaction at room temperature. By adjusting the dopamine and PEI ratio as well as the chain length of PEI, the fluorescence emission and quenching properties of PDA-PEI nanodots can be controlled well. Under optimal conditions, the nanodots showed strong green fluorescence emission with an absolute quantum yield of 1-2% and a quenching efficiency of more than 99% to several fluorophores with emission wavelengths ranging from blue to red light regions. The nanodots with a large number of functional groups also showed strong affinity to nucleic acid strands, excellent solubility in aqueous solution, long-term stability, and uniform size distribution. Integrating these attractive features with the specific enzymatic digestion reaction of the DSN enzyme, a highly sensitive ratiometric fluorescence nanoprobe for miRNA analysis was developed. Aminomethylcoumarin acetate (AMCA), which possesses the same excitation wavelength but a well-resolved blue fluorescence emission with PDA-PEI nanodots, was selected as the signal-reporting unit for capture probe labeling, while the inherent green fluorescence of PDA-PEI nanodots served as the reference. According to the ratiometric fluorescence signal, the ratiometric fluorescence nanoprobes showed high sensitivity and good accuracy for the miRNA assay. Because of the high and universal quenching efficiency, stable fluorescence emission, easily assembled interface, and uniform morphology, the nanodots may have great application prospects to serve as a universal nanoplatform for the fabrication of ratiometric fluorescence nanoprobes.

2D nanomaterial sensing array using machine learning for differential profiling of pathogenic microbial taxonomic identification

An integrated custom cross-response sensing array has been developed combining the algorithm module’s visible machine learning approach for rapid and accurate pathogenic microbial taxonomic identification. The diversified cross-response sensing array consists of two-dimensional nanomaterial (2D-n) with fluorescently labeled single-stranded DNA (ssDNA) as sensing elements to extract a set of differential response profiles for each pathogenic microorganism. By altering the 2D-n and different ssDNA with different sequences, we can form multiple sensing elements. While interacting with microorganisms, the competition between ssDNA and 2D-n leads to the release of ssDNA from 2D-n. The signals are generated from binding force driven by the exfoliation of either ssDNA or 2D-n from the microorganisms. Thus, the signal is distinguished from different ssDNA and 2D-n combinations, differentiating the extracted information and visualizing the recognition process. Fluorescent signals collected from each sensing element at the wavelength around 520 nm are applied to generate a fingerprint. As a proof of concept, we demonstrate that a six-sensing array enables rapid and accurate pathogenic microbial taxonomic identification, including the drug-resistant microorganisms, under a data size of n = 288. We precisely identify microbial with an overall accuracy of 97.9%, which overcomes the big data dependence for identifying recurrent patterns in conventional methods. For each microorganism, the detection concentration is 10⁵ ~ 10⁸ CFU/mL for Escherichia coli, 10² ~ 10⁷ CFU/mL for E. coli-β, 10³ ~ 10⁸ CFU/mL for Staphylococcus aureus, 10³ ~ 10⁷ CFU/mL for MRSA, 10² ~ 10⁸ CFU/mL for Pseudomonas aeruginosa, 10³ ~ 10⁸ CFU/mL for Enterococcus faecalis, 10² ~ 10⁸ CFU/mL for Klebsiella pneumoniae, and 10³ ~ 10⁸ CFU/mL for Candida albicans. Combining the visible machine learning approach, this sensing array provides strategies for precision pathogenic microbial taxonomic identification.

Recent Advances in Intrinsically Fluorescent Polydopamine Materials

Fluorescence nanoparticles have gained much attention due to their unique properties in the sensing and imaging fields. Among the very successful candidates are fluorescent polydopamine (FPDA) nanoparticles, attributed to their simplicity in tracing and excellent biocompatibility. This article aims to highlight the recent achievements in FPDA materials, especially on the part of luminescence mechanisms. We focus on the intrinsic fluorescence of PDA and will not discuss fluorescent reaction with a fluorometric reagent or coupling reaction with a fluorophore, which may cause more in vivo interferences. We believe that intrinsic FPDA presents great potential in bioapplications.

Identification of Water-Soluble Polymers through Discrimination of Multiple Optical Signals from a Single Peptide Sensor

The pollution of water environments is a worldwide concern. Not only marine pollution by plastic litter, including microplastics, but also the spillage of water-soluble synthetic polymers in wastewater have recently gained increasing attention due to their potential risks to soil and water environments. However, conventional methods to identify polymers dissolved in water are laborious and time-consuming. Here, we propose a simple approach to identify synthetic polymers dissolved in water using a peptide-based molecular sensor with a fluorophore unit. Supervised machine learning of multiple fluorescence signals from the sensor, which specifically or nonspecifically interacted with the polymers, was applied for polymer classification as a proof of principle demonstration. Aqueous solutions containing different polymers or multiple polymer species with different mixture ratios were identified successfully. We found that fluorophore-introduced biomolecular sensors have great potential to provide discriminative information regarding water-soluble polymers. Our approach based on the discrimination of multiple optical signals of water-soluble polymers from peptide-based molecular sensors through machine learning will be applicable to next-generation sensing systems for polymers in wastewater or natural environments.

Rotating the C-N Bond in a Coumarin-Pyridine-Based Sensor for Pattern Recognition of Versatile Metal Ions

A cross-reactive sensor array is powerful for high-throughput discrimination of various kinds of metal ions. However, the construction of a multicomponent sensor array is always time-consuming and cost-ineffective. Herein, a practical four-component X1-based sensor array (X1SA) was obtained by simply dissolving a single dye molecule X1 in respective solvents such as methanol, ethanol, dimethyl sulfoxide, and acetonitrile. In this design, X1 exhibits strong solvatochromic fluorescence properties via an excited-state intramolecular proton transfer and intramolecular charge transfer combined mechanism. Moreover, rotation of the C-N bond between the pyridine and coumarin units in X1 enabled it to coordinate with metal ions through different binding modes, which acted as an additional dimension of the sensor array. Inspired by this C-N bond rotation strategy, X1SA was determined to be powerful in discriminating 20 kinds of metal ions in both phosphate-buffered saline and 5% serum media in a range of 0.1-100 μM. In addition, the sensor array was also successfully applied in differentiating similar and mixed metal ions such as Fe³⁺/Fe²⁺, Cd²⁺/Hg²⁺, and Sn²⁺/Pb²⁺ in serum samples, which is meaningful for investigating the biological roles of iron and early diagnosis of related metal poisoning accidents.

Fluorescent pattern recognition of metal ions by nanoparticles of bovine serum albumin as a chemical nose/tongue

A sensor array mimicking a chemical nose/tongue based on bovine serum albumin nanoparticles (BSANsn) has been developed for the fluorescence pattern recognition of metal ions in biofluids. Three types of BSANsn (BSANs10, BSANs20, and BSANs40) show the same excitation/emission peak at 478/526 nm. According to the differential fluorescence variation, the sensor array shows particular fluorescence response patterns depending upon metal ions. Upon principal component analysis (PCA), it was found that the sensor array can distinguish 18 metal ions clearly at a concentration of as low as 10 μM. Moreover, different concentrations of metal ions and mixed metal ions of diverse kinds or valence states can be differentiated by the sensor in biofluids. In addition, the results were well consistent with those obtained with the traditional ICP-AES method.

Programmable Engineering of DNA-AuNP Encoders Integrated Multimodal Coupled Analysis for Precision Discrimination of Multiple Metal Ions

A cross-responsive strategy (CRS) based on gold nanoparticles (AuNPs) through attaching various recognition receptors on the surface of AuNPs for identifying multiple analytes is presented, and the detection throughput and overall identification accuracy are improved. However, the CRS's recognition receptor cannot get comprehensive information from the target analytes limited in number and type, which determines the overall identification accuracy. Therefore, the practicability of the CRS runs into a bottleneck. Herein, we report a programmable DNA-AuNP encoder combined with a multimodal coupled analysis algorithm for high-throughput detection and accurate analysis of multiple metal ions. The programmable DNA-AuNP encoder breaks through the limitation of the recognition receptor's quantity. Furthermore, the multimodal signals from target metal ion-induced DNA-AuNP aggregation are related to and observed in the ultraviolet absorbance spectrum, surface potential, and particle diameter. The multimodal coupled analysis algorithm can reflect comprehensive information on the target analyte more completely. Finally, this study provides a highly generic tool for the cross-responsive strategy.

Fluorescence copolymer-based dual-signal monitoring tyrosinase activity and its inhibitor screening via blue-green emission transformation

Tyrosinase (TYR) is a crucial enzyme in melanin metabolism and catecholamine production, its abnormal overexpression is closely associated with many human diseases involving melanoma cancer, vitiligo, Parkinson's disease and so on. Herein, a dual-signal fluorescence sensing system for monitoring TYR activity is constructed depending on the transformation of blue-green fluorescence emission of copolymer. The developed sensing system is based on TYR catalyzing the hydroxylation of mono-phenol to o-diphenol and the conversion of fluorescence copolymer (FCP) blue emission (430 nm) and green emission (535 nm) in the presence of PEI. In the system, both blue and green emission exhibit a high selectivity and sensitivity (S/B up to 300 and 30 for blue and green emission, respectively) toward TYR in the range from 0.5 to 2.5 U/mL with the detection limit of 0.002 U/mL and 0.06 U/mL, respectively. Additionally, this assay is used to detect TYR in human serum with excellent recovery even at 30% human serum concentrations. Furthermore, it still has been successfully applied to TYR inhibitor screening by taking kojic acid as a model. We believe that our developed sensor has great potential application in TYR-associated disease diagnosis and treatment and drug discovery.

Visual detection of different metal ions based on the tug of war between triangular Au nanoparticles and metal ions against mercaptans

Herein, a new colorimetric sensor array was developed for the first time, which can rapidly recognize 9 types of metal ions (e.g., Ni2+, Zn2+, Cd2+, Cu2+, Cr3+, Fe2+, Se2+, Mn2+, and Mg2+). The colorimetric characteristics of the sensor array were closely related to the oxidation etching of the triangular gold nanoplates (AuNPLs) by hydrogen peroxide (H2O2), catalyzed by horseradish peroxidase (HRP). In the design, two types of thiols (glutathione (GSH) and cysteine (Cys)) as recognition elements were employed to construct the sensor units (AuNPLs/GSH and AuNPLs/Cys) and adjust the etching degrees of AuNPLs in the presence of various metal ions. The differential binding affinities between metal ions and thiols will lead to different degrees of oxidation etching of AuNPLs with hydrogen peroxide, exhibiting characteristic colors, which can be visually distinguished by the naked eye. Thus, the colorimetric sensor array provides a new way for the discrimination of various metal ions, thereby simplifying the water quality analysis.

Discrimination of copper and silver ions based on the label-free quantum dots

A simple and fast method for copper ions (Cu²⁺) and silver ions (Ag⁺) detection was established with cadmium telluride quantum dots (CdTe QDs) as fluorescent probes. In the presence of Cu²⁺ or Ag⁺, the fluorescence intensity of TGA-CdTe QD can be significantly quenched, which fitted a linear relationship between the fluorescence quenching degree (F₀-F)/F₀ and the concentration of metal ions. In this work, the lowest detected concentration for Cu²⁺ and Ag⁺ was 35.0 nM and 25.3 nM, respectively. In addition, the differentiation of Cu²⁺ and Ag⁺ at different concentrations was realized with the principal component analysis (PCA). Furthermore, Cu²⁺ was successfully detected in body fluids. This method provides a good potential for copper ions and silver ions detection with simplicity, rapidity, and excellent selectivity.

Protein discrimination based on DNA induced perylene probe self-assembly

The development of a simple and effective method for the highly sensitive and selective discrimination of proteins is a subject of enormous interest. Herein, we report the construction of a novel fluorescence detection method based on a perylene probe for the highly efficient discrimination of multiple proteins. Single-stranded DNA (ssDNA) could induce aggregation of the perylene probe which caused quenching of probe fluorescence. After the addition of a protein, the protein could interact with the ssDNA-probe assembly complex with "turn-on" or further "turn-off" fluorescence response. A sensor array was designed based on the above phenomena which could realize the successful discrimination of proteins with 100% accuracy of cross validation. Nine representative proteins were successfully recognized. Moreover, it was observed that a protein could induce characteristic effect on the DNA-probe assembly with varying pH of assay buffer. Thus, different proteins showed unique fluorescence response towards assay buffers having different pH values. The assay buffer pH was then utilized as a sensing channel. Based on Linear Discriminant Analysis (LDA) nine proteins were successfully discriminated at the nanomolar concentration with 100% accuracy of cross validation. Furthermore, the sensor array also demonstrated differentiation of the nine proteins regardless of their concentration. The developed sensor array could also detect the proteins with great precision in human urine sample at a quite low concentration, which suggests its practical applicability for analysis of biological fluids.

Photothermal and fluorescent dual-mode assay based on the formation of polydopamine nanoparticles for accurate determination of organophosphate pesticides

A photothermal and fluorescent dual-mode assay for sensitive organophosphate pesticides (Ops) determination is reported based on alkaline phosphatase (ALP)-inhibition-induced formation of polydopamine (PDA) nanoparticles. In the presence of ALP, ascorbic acid 2-phosphate (AAP) can be catalyzed to produce ascorbic acid (AA). AA can reduce MnO₂ nanosheets, further inhibiting the oxidation of dopamine (DA). Ops as an inhibitor for ALP activity prevents the formation of AA and the reduction of MnO₂ nanosheets. Eventually, the formation of PDA nanoparticles is promoted. The inhibitory effect of Ops on ALP activity causes obvious changes of photothermal signals and fluorescence signal at 495 nm. The detection limit (LOD) of dimethoate is 0.1 μM. The method displays excellent sensing capability for the dimethoate assay in real water with good recoveries of 99.4-107.6%. Graphical abstract A photothermal and fluorescent dual-mode biosensor for sensitive Ops detection was reported based on alkaline phosphatase (ALP)-inhibition-induced formation of polydopamine (PDA) nanoparticles. The dual-mode method significantly improved the accuracy and reliability of the results.

Facile Approach to Fabricate a Chemical Sensor Array Based on Nanocurcumin-Metal Ions Aggregates: Detection and Identification of DNA Nucleobases

Here, a three-channel absorbance sensor array based on the nanocurcumin-metal ion (NCur-MI) aggregates is designed for the detection and identification of deoxyribonucleic acid nucleobases (DNA NBs) for the first time. For this purpose, the binding affinities of some of MIs (i.e., Co2+, Cr3+, Cu2+, Fe2+, Fe3+, Hg2+, Mn2+, Ni2+, V3+, and Zn2+) to the NCur to induce the aggregation were evaluated under various experimental conditions. Further studies reveal that in the presence of DNA NBs, the aggregates of NCur-Co2+, NCur-Ni2+, and NCur-Zn2+ show the diverse absorbance responses to the deaggregation of NCur depending on the binding affinity of each of DNA NBs to the metal ions Co2+, Ni2+, and Zn2+. These responses are distinguishable from one another. Thus, clear differentiation among the DNA NBs is achieved by linear discriminant analysis and hierarchical clustering analysis to generate clustering maps. The discriminatory capacity of the sensor array for the identification of the DNA NBs is tested in the ranges of 2.4-16 and 5.6-10.4 μM. Furthermore, a mixed set of the DNA NBs was prepared for multivariate multicomponent analysis. Finally, the practicability of the sensor array is confirmed by the discrimination of the DNA NBs in an animal DNA sample. It should be noted that the proposed array is the first example to fabricate an NCur-based sensor array for the simultaneous detection of DNA NBs.

The Marriage of Protein and Lanthanide: Unveiling a Time-Resolved Fluorescence Sensor Array Regulated by pH toward High-Throughput Assay of Metal Ions in Biofluids

A protein/lanthanide complex (BSA/Tb³⁺)-based sensor array in two different pH buffers has been designed for high-throughput recognition and time-resolved fluorescence (TRF) detection of metal ions in biofluids. BSA, which acted as an antenna ligand, can sensitize the fluorescence of Tb³⁺ (i.e., antenna effect), while the presence of metal ions would lead to the corresponding conformational change of BSA for altering the antenna effect accompanied by a substantial TRF performance of Tb³⁺. This principle has also been fully proved by both experimental characterizations and coarse-grained molecular dynamics (CG-MD) studies. By using Tris-HCl buffer with different pHs (at 7.4 and 8.5), 17 metal ions have been well-distinguished by using our proposed BSA/Tb³⁺ sensor array. Moreover, the sensor array has the potential to discriminate different concentrations of the same metal ions and a mixture of metal ions. Remarkably, the detection of metal ions in biofluids can be realized by utilizing the presented sensor array, verifying its practical applications. The platform avoids the synthesis of multiplex sensing receptors, providing a new method for the construction of convenient and feasible lanthanide complex-based TRF sensing arrays.

Coordination polymers of Tb3+/Nucleotide as smart chemical nose/tongue toward pattern-recognition-based and time-resolved fluorescence sensing

The abundant functional groups on guanosine monophosphate (GMP) make it possible to interact with various metal ions. The subtle difference in the structure of GMP and deoxy-guanosine monophosphate (dGMP) coupled with Tb3+ can be readily exploited to form two coordination polymers, which have been unveiled as two time-resolved fluorescence (TRF) sensing reporters (Tb-GMP and Tb-dGMP) in our study. Based on this finding, herein, we have proposed a novel TRF orthogonal sensing array (Tb-GMP/dGMP) for pattern-recognition-based sensing of various metal ions. In addition, upon integration of some thiol-affinity metal ions, Tb-GMP/dGMP can be further extended to construct two metal ion-involved pattern-recognition-based sensor arrays (Tb-GMP/dGMP-Cu, Tb-GMP/dGMP-Ag) for the TRF sensing different levels of disease-relevant biothiols in biofluids, illustrating the powerful and multifunctional capabilities of the Tb-GMP/dGMP system and would inspire simpler and more widespread designs of chemical nose/tongue-based applications.

Electronic-Tongue Colorimetric-Sensor Array for Discrimination and Quantitation of Metal Ions Based on Gold-Nanoparticle Aggregation

Sensor arrays, called "electronic tongues", provide an alternative to time-consuming detection approaches. In this work, a colorimetric-sensor array composed of three recognition receptors (cysteine, l-glutathione, and melamine) was developed for fast discrimination of toxic metal ions. Different recognition receptors exhibited different binding affinities toward metal ions, causing diverse gold-nanoparticle (AuNP)-aggregation behaviors and generating distinct colorimetric response patterns. As "fingerprints", these response patterns can be quantitatively analyzed by linear-discriminant analysis (LDA). The sensor array achieved good discrimination of six kinds of metal ions (Ti⁴⁺, Cr³⁺, Mn²⁺, Fe³⁺, Pb²⁺, and Sn⁴⁺) in deionized water and real samples. It possessed good reproducibility and exhibited a linear range of 100-900 nM ( R² = 0.97) for Ti⁴⁺, 100-900 nM ( R² = 0.97) for Cr³⁺, 100-900 nM ( R² = 0.98) for Mn²⁺, 100-1000 nM ( R² = 0.92) for Sn⁴⁺, 100-800 nM ( R² = 0.94) for Fe³⁺, and 100-900 nM ( R² = 0.97) for Pb²⁺. The sensor array shows feasible potential in environmental monitoring and simplification of water-quality analysis.

Visual artificial tongue for identification of various metal ions in mixtures and real water samples: a colorimetric sensor array using off-the-shelf dyes

A colorimetric sensor array was constructed to detect metal ions by pattern recognition based on image analysis and absorption spectra.

Label-free non-invasive fluorescent pattern discrimination of thiols and chiral recognition of cysteine enantiomers in biofluids using a bioinspired copolymer-Cu2+ hybrid sensor array regulated by pH

Thiols play a crucial role in various biological processes, and the discrimination of thiols in biofluids is a significant but difficult issue. Herein, a facile label-free non-invasive fluorescent sensor array has been presented based on PDA/PEI_n-Cu²⁺ in three different pH buffer solutions for pattern discrimination of thiols and chiral recognition of cysteine (Cys) enantiomers in biofluids toward health monitoring. The proposed sensor array was fabricated based on the fact that Cu²⁺ has a strong affinity toward thiols, which prevents Cu²⁺ from binding PDA/PEI_n, and the fluorescence properties of PDA/PEI_n were recovered to a certain degree. Different thiols exhibited different affinities toward Cu²⁺, generating distinct fluorescence response patterns. These response patterns are characteristic for each thiol and can be discriminated by principal component analysis (PCA). In this work, three types of PDA/PEI₄₈-Cu²⁺ sensors (PDA/PEI₄₈-Cu₄ ²⁺, PDA/PEI₄₈-Cu_4.5 ²⁺ and PDA/PEI₄₈-Cu₅ ²⁺) were prepared by using acetate buffer with different pHs (at 4, 4.5, and 5) to form our proposed sensor array, which could realize the pattern discrimination of 8 thiols. Moreover, we successfully realized the sensitivity and selectivity assays to these thiols. Furthermore, the proposed sensor array could discriminate mixtures of thiols as well as the chiral recognition of mixtures of Cys enantiomers, promising its potential practical usage. Significantly, the resultant practical application in real samples showed that it could be a fascinating assay for the development of non-invasive diagnosis. This method promises the facile, sensitive and powerful discrimination of thiols in biofluids and would sprout more relevant strategies toward a broad range of applications.

Inorganic-Organic Hybrid Tongue-Mimic for Time-Resolved Luminescent Noninvasive Pattern and Chiral Recognition of Thiols in Biofluids toward Healthcare Monitoring

In this work, manganese(II)-doped zinc/germanium oxide nanoparticles (Mn@ZGNPs) have been hydrothermally synthesized to equip with appealing time-resolved luminescence (TRL). Interestingly, we reveal that they can be readily quenched ("turn off") via a facile surface coating with bioinspired polydopamine (PDA) polymerized from dopamine (DA), resulting from PDA-triggered TRL resonance energy transfer (TRL-RET). By integrated with the thiol-induced inhibition of PDA formation, an ingenious inorganic-organic hybrid tongue-mimic sensor array is thus unveiled for noninvasive pattern recognition of thiols in biofluids in a TRL-RET-reversed "turn on" format toward healthcare monitoring. The sensing principle is based on the new finding that there are differential inhibitions from thiols against the polymerization of DA with various concentrations. Furthermore, density function theory (DFT) studies excellently prove our sensing principle and experimental results, reinforcing the power of the presented system. More importantly, chiral recognition of varied concentrations and mixtures of cysteine enantiomers using our platform are also been demonstrated, promising its practical usage. This is a novel concept of inorganic-organic hybrid-based pattern and chiral recognition platform for TRL background-free sensing and would sprout more novel relevant strategies toward broader applications.

pH-Regulated Optical Performances in Organic/Inorganic Hybrid: A Dual-Mode Sensor Array for Pattern-Recognition-Based Biosensing

Dual-mode optical assays are becoming more popular and attractive because they would provide robust detailed information in biochemical analysis. We herein unveil a novel dual-mode optical (i.e., UV-vis absorption and fluorescence) method for multifunctional sensing of phosphate compounds (PCs) (e.g., nucleotides and pyrophosphate) based on pattern recognition, which innovatively employs only one kind of porphyrin/lanthanide-doped upconversion nanoparticles (Ln-UCNPs) hybrid integrated with a facile pH-regulated strategy as the sensor array. An easy-to-obtain porphyrin hydrate (tetraphenylporphyrin tetrasulfonic acid hydrate, TPPS) can assemble onto the ligand-free Ln-UCNPs to construct the organic/inorganic hybrid (TPPS/Ln-UCNPs), leading to a new absorption band to quench the upconversion fluorescence of Ln-UCNPs due to fluorescence resonance energy transfer (FRET). The dual-mode optical performances of TPPS/Ln-UCNPs are characteristically correlated with the pH in aqueous solution. Thus, as a proof-of-concept design, three types of TPPS/Ln-UCNPs (TPPS/Ln-UCNPs₄, TPPS/Ln-UCNPs_4.5, and TPPS/Ln-UCNPs₅) were prepared by using buffers with different pH (at 4, 4.5, and 5) to form our proposed sensor array, which would result in individual dual-mode optical response patterns upon being challenged with PCs for their pattern recognition through a competitive mechanism between TPPS and PCs. The results show that three TPPS/Ln-UCNPs _n sensors can successfully permit the sensitive detection of 14 PCs and differentiate them between different concentrations, as well as a mixture of them. The pH-dependent TPPS/Ln-UCNPs promises the simple, yet powerful discrimination of PCs via pattern recognition, would prospectively stimulate and expand the use of organic/inorganic hybrid toward more biosensing applications.

Facile Preparation of Highly Luminescent Nitrogen-Doped Carbonaceous Nanospheres and Potential Application in Intracellular Imaging of Quercetin

Highly luminescent nitrogen-doped carbonaceous nanospheres (LNCNs) were synthesized by a one-pot hydrothermal reaction of β-cyclodextrin (β-CD) and branched polyethylenimine (BPEI). Both the N-doping and amino-functionalisation of LNCNs were achieved simultaneously. The prepared LNCNs display excellent properties such as high physical and chemical stability, excitation wavelength-independent emission, and high photoluminescence quantum yields. Importantly, the LNCNs exhibit a quenching of photoluminescence in the presence of quercetin (Qc) based on the simple static quenching mechanism, making it possible to quantify concentrations from 0.5 to 80 μg mL−1 with a detection limit of 0.21 μg mL−1. Furthermore, the LNCNs probe was further used for imaging Qc in living cells.