Molecularly Imprinted Photonic Polymers as Sensing Elements for the Creation of Cross‐Reactive Sensor Arrays

By combining molecular imprinting and colloidal crystal templating, molecularly imprinted inverse‐opal photonic polymers (MIPPs) acting as sensing elements have been exploited to create sensor arrays for the first time. With this new strategy, abundant sensing elements with differential sensing abilities were easily accessible. Because of the unique hierarchical porous structure integrated in each sensing element, high sensitivity and selectivity, fast response and self‐reporting (label‐free) detection could be simultaneously achieved. All these fascinating features indicate that MIPPs are ideal sensing elements for creating sensor arrays. By integrating the individual sensing elements on a substrate, the formed array chip delivers better portability and high‐throughput capability. As a demonstration, six kinds of contaminants were selected as analytes. The detection and discrimination of these analytes and even their mixtures in a wide range of concentrations, particularly trace amounts of analyte against a high background of other components, could be achieved, indicating the powerful capability of MIPPs‐based sensor array for sensing. These results suggest that the described strategy opens a new route for sensor array creation and should find important applications in a wide range of areas.     

A Rapid and Efficient Way to Dynamic Creation of Cross‐Reactive Sensor Arrays Based on Ionic Liquids

Based on the simple counterion exchange of ionic liquids, a rapid, facile, and efficient strategy to create a cross‐reactive sensor array with a dynamic tunable feature was developed, and exemplified by the construction of a sensor array for the identification and classification of nitroaromatics and explosives mimics. To achieve a good sensing system with fast response, good sensitivity, and low detection limit, the synthesized ionic liquid receptors were tethered onto a silica matrix with a macro‐mesoporous hierarchical structure. Through the facile anion exchange approach, abundant ionic‐liquid‐based individual receptors with diversiform properties, such as different micro‐environments, diverse molecular interactions, and distinctive physico‐chemical properties, were easily and quickly synthesized to generate a distinct fingerprint of explosives for pattern recognition. The reversible anion exchange ability further endowed the sensor array with a dynamic tunable feature as well as good controllability and practicality for real‐world application. With the assistance of statistical analysis, such as principal component analysis (PCA) and linear discrimination analysis (LDA), an optimized‐size array with a good resolution was rationally established from a large number of IL‐based receptors. The performed experiments suggested that the ionic‐liquid‐based sensing protocol is a general and powerful strategy for creating a cross‐reactive sensor array that could find a wide range of applications for sensing various analytes or complex mixtures.     

Boronic acid based peptidic receptors for pattern-based saccharide sensing in neutral aqueous media, an application in real-life samples

The advent of the alternative sweeteners market has signaled a demand for chemosensors which target multiple saccharides and saccharide derivatives, in aqueous media at physiological pH. This demand has largely been unmet as existing molecular receptors for saccharides have generally not shown sufficient degrees of affinity and selectivity in aqueous media. A chemosensor array for saccharides and saccharide derivatives, fully operational in aqueous media at physiological pH, has been developed and is reported herein. Boronic acid based peptidic receptors, derived from a combinatorial library, served as the cross-reactive sensor elements in this array. The binding of saccharides to these receptors was assessed colorimetrically using an indicator uptake protocol in the taste-chip platform. The differential indicator uptake rates of these receptors in the presence of saccharides were exploited in order to identify patterns within the data set using linear discriminant analysis. This chemosensor array is capable of classifying disaccharides and monosaccharides as well as discriminating compounds within each saccharide group. Disaccharides have also been distinguished from closely related reduced-calorie counterparts. This linear discriminant analysis set was then employed as a training set for identifying a specific saccharide in a real-world beverage sample. The methodology developed here augurs well for use in other real-world samples involving saccharides as well as for sensing other desired analytes.     

Photocatalytically Powered Matchlike Nanomotor for Light‐Guided Active SERS Sensing

Surface enhanced Raman spectroscopy (SERS) is a powerful optical sensing technique that can detect analytes of extremely low concentrations. However, the presence of enough SERS probes in the detection area and a close contact between analytes and SERS probes are critical for efficient acquisition of a SERS signal. Presented here is a light‐powered micro/nanomotor (MNM) that can serve as an active SERS probe. The matchlike AgNW@SiO₂ core–shell structure of the nanomotors work as SERS probes based on the shell‐isolated enhanced Raman mechanism. The AgCl tail serves as photocatalytic nanoengine, providing a self‐propulsion force by light‐induced self‐diffusiophoresis. The phototactic behavior was utilized to achieve enrichment of the nanomotor‐based SERS probes for on‐demand biochemical sensing. The results demonstrate the possibility of using photocatalytic nanomotors as active SERS probes for remote, light‐controlled, and smart biochemical sensing on the micro/nanoscale.     

Electrochemical Detection of Pathogenic Bacteria—Recent Strategies,Advances and Challenges

Bacterial infections represent one of the leading causes of mortality worldwide, nevertheless the design and development of rapid, cost‐efficient and reliable detection methods for pathogens remains challenging. In recent years, electrochemical sensing methods have gained increasing attention for the detection of pathogenic bacteria, due to their increasingly competitive sensitivity. However, combining sensitivity with cost efficiency, high selectivity and a facile working procedure in a portable device is difficult. The presented review provides a summary of biosensing strategies for bacteria, published since 2015, by covering significant achievements towards custom‐designed portable point‐of‐care devices. Herein, the direct chemical recognition of bacteria via enzyme activity or secretion products, as well as their detection at various electrode surfaces and materials, such as nanomaterials, indium tin oxide or paper‐based immunosensors, is discussed. Furthermore, newly established hyphenated sensing principles, incorporated into lab‐on‐a‐chip and microfluidic devices, are presented and remaining technical challenges and limitations are considered.     

Enzymatic/Immunoassay Dual‐Biomarker Sensing Chip: Towards Decentralized Insulin/Glucose Detection

Performing bioassay formats based on enzyme and antibody recognition reactions with a single detection chip remains an unmet challenge owing to the different requirements of such bioassays. Herein, we describe a dual‐marker biosensor chip, integrating enzyme and antibody‐based assays for simultaneous electrochemical measurements of insulin (I) and glucose (G). Simultaneous G/I sensing has been realized by addressing key fabrication and operational challenges associated with the different assay requirements and surface chemistry. The I immunosensor relies on a peroxidase‐labeled sandwich immunoassay, while G is monitored through reaction with glucose oxidase. The dual diabetes biomarker chip offers selective and reproducible detection of picomolar I and millimolar G concentrations in a single microliter sample droplet within less than 30 min, including direct measurements in whole blood and saliva samples. The resulting integrated enzymatic‐immunoassay biosensor chip opens a new realm in point‐of‐care multiplexed biomarker detection.     

Preparation of cotton fabric based non-invasive colorimetric sensor for instant detection of ketones

Cotton based colorimetric sensing offers great potential for the detection of desired analytes due to their easy naked-eye sensing, ease in fabrication, cost effectiveness, rapid recognition, high sensitivity and selectivity. Poly (2-(dimethylamino ethyl) methacrylate) (pDMAEMA) and sodium nitroprusside (SNP) were deposited alternatively on a treated cotton fabric for non invasive calorimetric sensing of ketones. Physical and chemical characterizations such as FESEM, EDS, XRD, UV–vis, FTIR and XPS of the treated cotton based sensor were carried out. Standard colour chart of the targeted ketones is prepared by dissolving appropriate amount of them with distilled water to get down to the final concentration as 80 mM and 10 µL of each solution of analyte was dropped on the surface of treated cotton fabric. The fabricated sensor is also tested for its practicability by analyzing the targeted ketones in human urine and the results obtained were compared with the standard colour chart. The results shows consistency in colours thereby making it a quick, efficient, eco-friendly and reliable monitoring tool to detect various ketones.     

On‐Chip Tailorability of Capacitive Gas Sensors Integrated with Metal–Organic Framework Films

Gas sensing technologies for smart cities require miniaturization, cost‐effectiveness, low power consumption, and outstanding sensitivity and selectivity. On‐chip, tailorable capacitive sensors integrated with metal–organic framework (MOF) films are presented, in which abundant coordinatively unsaturated metal sites are available for gas detection. The in situ growth of homogeneous Mg‐MOF‐74 films is realized with an appropriate metal‐to‐ligand ratio. The resultant sensors exhibit selective detection for benzene vapor and carbon dioxide (CO₂) at room temperature. Postsynthetic modification of Mg‐MOF‐74 films with ethylenediamine decreases sensitivity toward benzene but increases selectivity to CO₂. The reduced porosity and blocked open metal sites caused by amine coordination account for a deterioration in the sensing performance for benzene (by ca. 60 %). The enhanced sensitivity for CO₂ (by ca. 25 %) stems from a tailored amine–CO₂ interaction. This study demonstrates the feasibility of tuning gas sensing properties by adjusting MOF–analyte interactions, thereby offering new perspectives for the development of MOF‐based sensors.     

Colorimetric sensor array–smartphone–remote server coupling system for rapid detection of saccharides in beverages

A kind of “colorimetric sensor array–smartphone–remote server” coupling system was constructed for rapid on-site testing of saccharides. First, the binding capacity between saccharides and boric acid compounds (boric acid, phenylboronic acid and 3-nitrophenylboronic acid) was studied. The binding capacity of 3-nitrophenylboronic acid was found to be the highest, followed by phenylboronic acid and boric acid. Then a small-scale colorimetric sensor array (2 × 2) of pH indicator based on affinity interaction between 3-nitrophenylboronic acid and saccharides was developed to detect 19 kinds of saccharides. A camera phone was used to acquire the array images before and after reaction, then the self-developed color discrimination software in smartphone was applied to process pictures in order to obtain the color difference image and data of analytes. The color difference data were analyzed by several methods, including principal component analysis, hierarchical cluster analysis and linear discriminant analysis. The analysis results showed that the sensor array (2 × 2) established in this paper has great discriminative capability for 19 kinds of saccharides, and the classification accuracy is as high as 100%. Nineteen different quantitative models of saccharides that showed high accuracy and precision were established based on partial least-square method. Finally, the smartphone was connected to a remote server on which the qualitative analysis and quantitative analysis models for analytes had been established. The color difference data obtained by the smartphone were uploaded to the remote server for the qualitative analysis and quantitative analysis of saccharides. The effectiveness of the “colorimetric sensor array–smartphone–remote server” coupling system in rapid on-site detection of saccharides was further verified by the spike and recovery experiments. The qualitative analysis results showed that this coupling system could distinguish all of the analytes without a mistake, and the quantitative analysis results showed that the predicted values for saccharides were close to the real values.     

Label‐Free Detection of Glycan–Protein Interactions for Array Development by Surface‐Enhanced Raman Spectroscopy (SERS)

A glyco‐array platform has been developed, in which glycans are attached to plasmonic nanoparticles through strain‐promoted azide‐alkyne cycloaddition. Glycan–protein binding events can then be detected in a label‐free manner employing surface‐enhanced Raman spectroscopy (SERS). As proof of concept, we have analyzed the binding of Gal1, Gal3, and influenza hemagglutinins (HAs) to various glycans and demonstrated that binding partners can be identified with high confidence. The attraction of SERS for optical sensing is that it can provide unique spectral signatures for glycan–protein complexes, confirm identity through statistical validation, and minimizes false positive results common to indirect methods. Furthermore, SERS is very sensitive and has multiplexing capabilities thereby allowing the simultaneous detection of multiple analytes.     

Boronic acid building blocks: tools for sensing and separation

In this feature article the use of boronic acids to monitor, identify and isolate analytes within physiological, environmental and industrial scenarios is discussed. Boronic acids recognise diol motifs through boronic ester formation and interact with anions generating boronates, as such they have been exploited in sensing and separation protocols for diol appended molecules such as saccharides and anions alike. Therefore robust molecular sensors with the capacity to detect chosen molecules selectively and signal their presence continues to attract substantial attention, and boronic acids have been exploited with some success to monitor the presence of various analytes. Reversible boronic acid-diol interactions have also been exploited in boron affinity chromatography realising new separation domains through the same binding events. Boronic acid diol and anion interactions pertaining to sensing and separation are surveyed.     

Evaluation of doped and undoped poly (o‐anisidine) as sensing materials for a sensor array for volatile organic compounds

Poly (o‐anisidine) (PoANI) and PoANI doped with nickel oxide and zinc oxide were evaluated as sensing materials for four gas analytes (methanol, ethanol, acetone, and benzene). The sensing materials had high sensitivity (showing an affinity towards the target analytes even at low concentrations, in the range of 1‐5 ppm), but rather poor selectivity, especially when the gas analytes were in a mixture. To exploit the poor selectivity, the three sensing materials were combined into a sensor array using principal component analysis (PCA) as a sensing algorithm. It was found that using a sensor array, the four individual gases could be separated. However, when all four gases were present (in analyte mixtures), there was too much overlap in the responses to distinguish between individual gas analytes and their related mixtures.     

Selective recognition of a saccharide-type tumor marker with natural and synthetic ligands: a new trend in cancer diagnosis

It is well known that saccharides and their glycoconjugates can have an important influence on various serious pathologic stages such as cancer. They can regulate tumor proliferation, invasion, hematogenous metastasis, and angiogenesis. These facts clearly show the importance of cancer saccharide recognition. In medicine, sensor analysis is one of the best methods for recognition and determination of biologically important analytes. The development and study of sensors for saccharide tumor markers can open a new way for their detection. Therefore, this review is focused on recognition of saccharide-based cancer markers by natural or synthetic selective ligands working as bio- and chemosensors. The design and application of these ligands for cancer diagnosis is a useful direction of research. Moreover, it also opens the possibility of using these agents for the targeted drug transport required for advanced anticancer therapy.     

Phenylboronic acid-functionalized TTFAQ: modular synthesis and electrochemical recognition for saccharides

A phenylboronic acid-functionalized π-extended tetrathiafulvalene (TTFAQ) derivative was prepared through an efficient Cu-catalyzed alkyne-azide [3+2] cycloaddition reaction (click reaction). This boronic acid-TTFAQ hybrid system shows different electrochemical redox behavior upon titration with various saccharides in DMSO/H₂O at pH 8.75, suggesting potential use in saccharide sensing and recognition.     

薄膜基荧光气体传感器中的涂层化学

近年来,高性能薄膜基气体传感器的研制备受关注,所涉及的涂层化学已经成为物理化学学科发展的一个热点。传感因分析物与敏感层(涂层)物质相互作用引起薄膜特定静态及动态物理量变化而实现,因此,薄膜传感性能势必受到敏感层物质种类和敏感层微纳结构等因素影响。就薄膜基荧光传感而言,荧光敏感物质的结构和性质对薄膜传感性能起着至关重要的作用。同时,因毛细凝结、色谱效应、尺寸效应、分子间相互作用等因素的存在,敏感层微观结构也极大地影响着薄膜的传感性能。本文结合课题组近期研究工作,简要讨论薄膜基荧光气体传感器研究中的涂层化学基本问题,以及相关薄膜基荧光传感器在隐藏爆炸物、毒品、挥发性有机污染物检测/监测等方面的应用探索。最后,文章展望了薄膜基荧光气体传感器的发展前景和所面临的主要挑战。     

Generating Selective Saccharide Binding Affinity of Phenyl Boronic Acids by using Single‐Walled Carbon Nanotube Corona Phases

Saccharides recognition is challenging due to their low affinity for substrates, yet this recognition is critical for human immunity and glycobiology. Herein, we demonstrate that a polymer or surfactant corona phase surrounding a single‐walled carbon nanotube can substantially modify the selectivity of pre‐adsorbed phenyl‐boronic acids (PBA) for mono‐, di‐, and poly‐saccharides. A library of 17 PBAs including carboxy, nitro, and amino PBA with ortho‐, meta‐, or para‐ substitutions are used to generate 144 distinct corona phases. Six in particular demonstrate significantly increased selectivity to specific saccharides including ribose (0.42 mol per total mol), arabinose (0.36), and glucose (0.25), but unusually diminished binding to fructose (0.02). Recognition proceeds by saccharide adsorption into the corona, followed by PBA reaction in a consecutive second order reaction. The results extend to larger saccharides, such as glycosaminoglycans, suggesting promise for protein glycosylation.     

A Glimpse of Our Journey into the Design of Optical Probes in Self‐assembled Surfactant Aggregates

Dynamic self‐assembling amphiphilic surfactant molecules, popularly known as “micelles”, have received widespread attention, due to their ability to modulate the photophysical properties of various organic dyes upon encapsulation. Along with their well‐known use as cleaning agents, catalysts in organic reactions, and even for drug delivery purposes, these surfactant assemblies also show promising pertinence in the recognition of both ionic and nonionic targeted analytes. Low micropolarity and relatively hydrophobic environments promote their interaction with ionic analytes, whereas neutral species mostly affect the aggregation pattern of the probe molecules upon partitioning inside the micellar hydrophobic milieu. The environment‐sensitive nature of micelle‐based self‐assembled probes also prompts us to devise new sensor arrays for the recognition of multiple analytes. While this account will largely focus on our own work in developing surfactant‐triggered self‐assembled sensors, our findings have been placed in the context of the relevant contributions from others during their strategic evolution.     

Highly Efficient Solid‐Phase Labeling of Saccharides within Boronic Acid Functionalized Mesoporous Silica Nanoparticles

Labeling is critical for the detection, quantitation, and structural identification of saccharides. However, conventional liquid‐phase labeling suffers from apparent disadvantages, such as time‐consuming, the presence of excessive labeling reagent, and high applicable saccharide concentration. A solid‐phase approach is presented for highly efficient labeling of saccharides, using boronic acid functionalized mesoporous silica nanoparticles (MSNs) as a selective extraction sorbent and nanoscale reactor. The solid‐phase labeling approach exhibited several significant advantages, including: much faster reaction speed (taking only 2 min), high product purity, and much lower applicable saccharide concentration (four orders of magnitude lower than that of liquid‐phase labeling). Thus, this labeling approach opens up new avenues to the facile and efficient labeling of saccharides.     

A Highly Fluorescent Metallosalalen‐Based Chiral Cage for Enantioselective Recognition and Sensing

A highly fluorescent coordination cage [Zn₈L₄I₈] has been constructed by treating enantiopure pyridyl‐functionalized metallosalalen units (L) with zinc(II) iodide and characterized by a variety of techniques including microanalysis, thermogravimetric analysis (TGA), circular dichroism (CD) spectroscopy, and single‐crystal and powder X‐ray diffraction. Strong intermolecular π–π, CH???π, and CH???I interactions direct packing of the cage molecules to generate a 3D polycage network interconnected by pentahedral cages formed by adjacent pentamers. The cage has an amphiphilic helical cavity decorated with chiral NH functionalities capable of interactions with guest species such as saccharides. The fluorescence of the cage was greatly enhanced by five enantiomeric saccharides in solution, with enantioselectivity factors of 2.480–4.943, and by five enantiomeric amines in the solid state, with enantioselective fluorescence enhancement ratios of 1.30–3.60. This remarkable chiral sensing of both saccharides and amines with impressive enantioselectivity may result from the steric confinement of the cavity as well as its conformational rigidity. It holds great promise for the development of novel chiral cage materials for sensing applications.     

Development and optimization of an integrated PDMS based‐microdialysis microchip electrophoresis device with on‐chip derivatization for continuous monitoring of primary amines

An all‐PDMS on‐line microdialysis‐microchip electrophoresis with on‐chip derivatization and electrophoretic separation for near real‐time monitoring of primary amine‐containing analytes is described. Each part of the chip was optimized separately, and the effect of each of the components on temporal resolution, lag time, and separation efficiency of the device was determined. Aspartate and glutamate were employed as test analytes. Derivatization was accomplished with naphthalene‐2,3,‐dicarboxyaldehyde/cyanide (NDA/CN^?), and the separation was performed using a 15‐cm serpentine channel. The analytes were detected using LIF detection.