Sensing Glucose in Urine and Serum and Hydrogen Peroxide in Living Cells by Use of a Novel Boronate Nanoprobe Based on Surface-Enhanced Raman Spectroscopy

Multidomain-Based Responsive Materials with Dual-Mode Optical Readouts

Responsive materials designed to generate signals for both surface-enhanced Raman spectroscopy (SERS) and phosphorescence lifetime-"dual-mode"-measurements are described. To demonstrate this concept, we incorporated pH-sensitive and oxygen-sensitive microdomains into a single hydrogel that could be interrogated via SERS and phosphorescence lifetime, respectively. Microdomains consisted two populations of discrete microcapsules containing either (1) gold nanoparticles capped with pH-sensitive Raman molecules or (2) oxygen-sensitive benzoporphyrin phosphors. While the microdomain-embedded hydrogels presented an expected background luminescence, the pH-sensitive SERS signal was distinguishable for all tested conditions. Response characteristics of the dual sensor showed no significant difference when compared to standalone single-mode pH and oxygen sensors. In addition, the feasibility of redundant multimode sensing was proven by observing the reaction produced by glucose oxidase chemically cross-linked within the corresponding alginate matrix. Each optical mode showed a signal change proportional to glucose concentration with an opposite signal directionality. These results support the promise of micro-/nanocomposite materials to improve measurement accuracy using intrinsic multimode responses and built-in redundancy, concepts that have broad appeal in the chemical sensing and biosensing fields.

Microscopy and Cell Biology: New Methods and New Questions

Understanding the cellular basis of human health and disease requires the spatial resolution of microscopy and the molecular-level details provided by spectroscopy. This review highlights imaging methods at the intersection of microscopy and spectroscopy with applications in cell biology. Imaging methods are divided into three broad categories: fluorescence microscopy, label-free approaches, and imaging tools that can be applied to multiple imaging modalities. Just as these imaging methods allow researchers to address new biological questions, progress in biological sciences will drive the development of new imaging methods. We highlight four topics in cell biology that illustrate the need for new imaging tools: nanoparticle-cell interactions, intracellular redox chemistry, neuroscience, and the increasing use of spheroids and organoids. Overall, our goal is to provide a brief overview of individual imaging methods and highlight recent advances in the use of microscopy for cell biology.

Etchable SERS nanosensor for accurate pH and hydrogen peroxide sensing in living cells

“Turning off” extracellular SERS signals for accurate pH and hydrogen peroxide sensing in living cells.

Phenylboronic acid derivative-modified (6,5) single-wall carbon nanotube probes for detecting glucose and hydrogen peroxide

In this paper, we presented a new method for constructing near-infrared fluorescence probes and their applications in detecting glucose and hydrogen peroxide (H₂O₂).

Facile detection of glucose in human serum employing silver-ion-guided surface-enhanced Raman spectroscopy signal amplification

A facile surface-enhanced Raman scattering (SERS) sensor based on a silver-ion-mediated amplification effect was designed for the determination of glucose concentration. In this approach, 4-aminothiophenol (4-ATP) molecules assembled on the surface of a gold wafer (Au wafer@4-ATP) act not only as Raman tags but also as linkage agents. Silver nanoparticles marked with cysteamine (AgNP@cys) were used as the SERS enhancement components because they could be bound to the Au wafer@4-ATP in the presence of silver ions through the formation of N → Ag⁺ ← N coordination compounds. Here, the Ag⁺ ions were obtained by using glucose oxidase to catalyze the oxidation of glucose, producing hydrogen peroxide (H₂O₂) to etch the AgNPs. Therefore, we recorded the SERS intensity of 4-ATP to determine the concentration of glucose in a phosphate buffer as low as 0.1 mM and further achieved a lowest detection of 0.5 mM glucose in human serum. These results show that the proposed approach has strong potential for practical applications.

para-Aminothiophenol Radical Reaction-Functionalized Gold Nanoprobe for One-to-All Detection of Five Reactive Oxygen Species In Vivo

Five major reactive oxygen species (ROS) are generated in diseases including H₂O₂, ^•OH, O₂^•-, ROO^•, and ¹O₂. Simultaneous detection of the five ROS with a single probe is crucial for a comprehensive understanding of the development and progression of many diseases, such as cancer and inflammatory diseases. However, currently reported detection systems are limited by targeting one ROS with one probe. This one-to-one detection mode may fail to sufficiently unveil the diseased state. In this study, we achieved simultaneous detection of all the five ROS with one probe (i.e., one-to-all detection), by designing a novel para-aminothiophenol (PATP) and hemin-decorated gold (Au/PATP/Hemin) nanoprobe. The design is principled by our discovery that PATP can react with ^•OH, O₂^•-, ROO^•, and ¹O₂ by a radical oxidative coupling mechanism to form 4,4'-dimercaptoazobenzene (DMAB). The DMAB then elicited strong characteristic surface-enhanced Raman scattering (SERS) peaks at 1142, 1386, and 1432 cm^-1; which in turn enables direct detection of ^•OH, O₂^•-, ROO^•, and ¹O₂ and indirect detection of H₂O₂ by hemin-catalyzed fenton reaction to convert H₂O₂ into ^•OH. In two representative ROS-elevated mice models of tumors and allergic dermatitis, the Au/PATP/Hemin nanoprobe demonstrated its robust performance of monitoring tumor development and inflammation progression in a highly sensitive and quantitative manner.

Applications of SERS in the Detection of Stress-Related Substances

A wide variety of biotic and abiotic stresses continually attack plants and animals, which adversely affect their growth, development, reproduction, and yield realization. To survive under stress conditions, highly sophisticated and efficient tolerance mechanisms have been evolved to adapt to stresses, which consist of the variation of effector molecules playing vital roles in physiological regulation. The development of a sensitive, facile, and rapid analytical methods for stress factors and effector molecules detection is significant for gaining deeper insight into the tolerance mechanisms. As a nondestructive analysis technique, surface-enhanced Raman spectroscopy (SERS) has unique advantages regarding its biosensing applications. It not only provides specific fingerprint spectra of the target molecules, conformation, and structure, but also has universal capacity for simultaneous detection and imaging of targets owing to the narrow width of the Raman vibrational bands. Herein, recent progress on biotic and abiotic stresses, tolerance mechanisms and effector molecules is summarized. Moreover, the development and promising future trends of SERS detection for stress-related substances combined with nanomaterials as substrates and SERS tags are discussed. This comprehensive and critical review might shed light on a new perspective for SERS applications.

On-demand quantitative SERS bioassays facilitated by surface-tethered ratiometric probes

A robust chip-based SERS concept for quantitative on-demand metabolite screening is established.

Reliable and user-friendly sensing of target analytes in complex biofluids is of fundamental importance to biological science and medicine. Surface-enhanced Raman spectroscopy (SERS) has proven to be capable of detecting molecules with high sensitivity, but achieving robust quantitative detection remains a challenge mainly because of the severe signal fluctuation at electromagnetic hot spots. Here, we describe an on-demand and quantitative SERS strategy for metabolite profiling based on a chip-based sensing device that adopts stable and surface-tethered small-molecule probes as Raman reporters. These probes with a ratiometric response allow for sensitive and reproducible SERS detection by offering an internal calibration to correct the signal fluctuation caused by the spatiotemporal variation of assay conditions. Meanwhile, the chip-based sensing scheme makes time-separated on-demand detection possible. Ultimately, due to the flexibility in choosing diverse ratiometric Raman probes, we expect the proposed quantitative SERS sensing concept to be useful for studies in the fields of cell biology and clinical diagnosis.

Utilizing Molecular Hyperpolarizability for Trace Analysis: A Surface-Enhanced Hyper-Raman Scattering Study of Uranyl Ion

Surface-enhanced hyper-Raman scattering (SEHRS), the nonlinear analog of surface-enhanced Raman scattering (SERS), provides unique spectral signatures arising from the molecular hyperpolarizability. In this work, we explore the differences between SERS and SEHRS spectra obtained from surface-bound uranyl ion. Exploiting the distinctive SEHRS bands for trace detection of the uranyl ion, we obtain excellent sensitivity (limit of detection = 90 ppb) despite the extreme weakness of the hyper-Raman effect. We observe that binding the uranyl ion to the carboxylate group of 4-mercaptobenzoic acid (4-MBA) leads to significant changes in the SEHRS spectrum, whereas the surface-enhanced Raman scattering (SERS) spectrum of the same complex is little changed. The SERS and SEHRS spectra are also examined as a function of both substituent position, using 2-MBA, 3-MBA, and 4-MBA, and the carbon chain length, using 4-mercaptophenylacetic acid and 4-mercaptophenylpropionic acid. These results illustrate that the unique features of SEHRS can yield more information than SERS in certain cases and represent the first application of SEHRS for trace analysis of nonresonant molecules.

SERS Sensors: Recent Developments and a Generalized Classification Scheme Based on the Signal Origin

Owing to its extreme sensitivity and easy execution, surface-enhanced Raman spectroscopy (SERS) now finds application for a wide variety of problems requiring sensitive and targeted analyte detection. This widespread application has prompted a proliferation of different SERS-based sensors, suggesting the need for a framework to classify existing methods and guide the development of new techniques. After a brief discussion of the general SERS modalities, we classify SERS-based sensors according the origin of the signal. Three major categories emerge from this analysis: surface-affinity strategy, SERS-tag strategy, and probe-mediated strategy. For each case, we describe the mechanism of action, give selected examples, and point out general misconceptions to aid the construction of new devices. We hope this review serves as a useful tutorial guide and helps readers to better classify and design practical and effective SERS-based sensors.

In Vitro and In Vivo SERS Biosensing for Disease Diagnosis

For many disease states, positive outcomes are directly linked to early diagnosis, where therapeutic intervention would be most effective. Recently, trends in disease diagnosis have focused on the development of label-free sensing techniques that are sensitive to low analyte concentrations found in the physiological environment. Surface-enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy that allows for label-free, highly sensitive, and selective detection of analytes through the amplification of localized electric fields on the surface of a plasmonic material when excited with monochromatic light. This results in enhancement of the Raman scattering signal, which allows for the detection of low concentration analytes, giving rise to the use of SERS as a diagnostic tool for disease. Here, we present a review of recent developments in the field of in vivo and in vitro SERS biosensing for a range of disease states including neurological disease, diabetes, cardiovascular disease, cancer, and viral disease.

Quantitative SERS Detection of Dopamine in Cerebrospinal Fluid by Dual-Recognition-Induced Hot Spot Generation

Reliable profiling of the extracellular dopamine (DA) concentration in the central nervous system is essential for a deep understanding of its biological and pathological functions. However, quantitative determination of this neurotransmitter remains a challenge because of the extremely low concentration of DA in the cerebrospinal fluid (CSF) of patients. Herein, on the basis of the specific recognition of boronate toward diol and N-hydroxysuccinimide ester toward the amine group, a simple and highly sensitive strategy was presented for DA detection by using surface-enhanced Raman scattering (SERS) spectroscopy as a signal readout. This was realized by first immobilizing 3,3'-dithiodipropionic acid di( N-hydroxysuccinimide ester) on gold thin film surfaces to capture DA, followed by introducing 3-mercaptophenylboronic acid (3-MPBA)-functionalized silver nanoparticles to generate numerous plasmonic "hot spots" with the nanoparticle-on-mirror geometry. Such a dual-recognition mechanism not only avoids complicated bioelement-based manipulations but also efficiently decreases the background signal. With the direct use of the recognition probe 3-MPBA as a Raman reporter, the "signal-on" SERS method was employed to quantify the concentration of DA from 1 pM to 1 μM with a detection limit of 0.3 pM. Moreover, our dual-recognition-directed SERS assay exhibited a high resistance to cerebral interference and was successfully applied to monitoring of DA in CSF samples of patients.

Ratiometric optical nanoprobes enable accurate molecular detection and imaging

Exploring and understanding biological and pathological changes are of great significance for early diagnosis and therapy of diseases. Optical sensing and imaging approaches have experienced major progress in this field. Particularly, an emergence of various functional optical nanoprobes has provided enhanced sensitivity, specificity, targeting ability, as well as multiplexing and multimodal capabilities due to improvements in their intrinsic physicochemical and optical properties. However, one of the biggest challenges of conventional optical nanoprobes is their absolute intensity-dependent signal readout, which causes inaccurate sensing and imaging results due to the presence of various analyte-independent factors that can cause fluctuations in their absolute signal intensity. Ratiometric measurements provide built-in self-calibration for signal correction, enabling more sensitive and reliable detection. Optimizing nanoprobe designs with ratiometric strategies can surmount many of the limitations encountered by traditional optical nanoprobes. This review first elaborates upon existing optical nanoprobes that exploit ratiometric measurements for improved sensing and imaging, including fluorescence, surface enhanced Raman scattering (SERS), and photoacoustic nanoprobes. Next, a thorough discussion is provided on design strategies for these nanoprobes, and their potential biomedical applications for targeting specific biomolecule populations (e.g. cancer biomarkers and small molecules with physiological relevance), for imaging the tumor microenvironment (e.g. pH, reactive oxygen species, hypoxia, enzyme and metal ions), as well as for intraoperative image guidance of tumor-resection procedures.

Surface-Enhanced Raman Spectroscopy for Bioanalysis: Reliability and Challenges

Surface-enhanced Raman spectroscopy (SERS) inherits the rich chemical fingerprint information on Raman spectroscopy and gains sensitivity by plasmon-enhanced excitation and scattering. In particular, most Raman peaks have a narrow width suitable for multiplex analysis, and the measurements can be conveniently made under ambient and aqueous conditions. These merits make SERS a very promising technique for studying complex biological systems, and SERS has attracted increasing interest in biorelated analysis. However, there are still great challenges that need to be addressed until it can be widely accepted by the biorelated communities, answer interesting biological questions, and solve fatal clinical problems. SERS applications in bioanalysis involve the complex interactions of plasmonic nanomaterials with biological systems and their environments. The reliability becomes the key issue of bioanalytical SERS in order to extract meaningful information from SERS data. This review provides a comprehensive overview of bioanalytical SERS with the main focus on the reliability issue. We first introduce the mechanism of SERS to guide the design of reliable SERS experiments with high detection sensitivity. We then introduce the current understanding of the interaction of nanomaterials with biological systems, mainly living cells, to guide the design of functionalized SERS nanoparticles for target detection. We further introduce the current status of label-free (direct) and labeled (indirect) SERS detections, for systems from biomolecules, to pathogens, to living cells, and we discuss the potential interferences from experimental design, measurement conditions, and data analysis. In the end, we give an outlook of the key challenges in bioanalytical SERS, including reproducibility, sensitivity, and spatial and time resolution.

A single nanoparticle-based real-time monitoring of biocatalytic progress and detection of hydrogen peroxide

This paper reported a new method to observe the catalytic progress of the natural horseradish peroxidase (HRP) in-situ on single gold nanoparticles (GNPs) by the combination of dark field imaging and plasmonic resonance scattering spectra. The produced single HRP-GNP exhibited localized catalytic property toward H₂O₂-Diaminobenzidine (DAB), which could be used to detect the concentration of H₂O₂ in micro/nanospace. The linear range for H₂O₂ sensing was from 0.01 μM to 5 μM with a detection limit of 10 nM. The new design strategy could be applied for a broader bioanalysis situation by substituting the HRP with other specified biocatalyst.

Nanoparticle-Assisted Metabolomics

Understanding and harnessing the interactions between nanoparticles and biological molecules is at the forefront of applications of nanotechnology to modern biology. Metabolomics has emerged as a prominent player in systems biology as a complement to genomics, transcriptomics and proteomics. Its focus is the systematic study of metabolite identities and concentration changes in living systems. Despite significant progress over the recent past, important challenges in metabolomics remain, such as the deconvolution of the spectra of complex mixtures with strong overlaps, the sensitive detection of metabolites at low abundance, unambiguous identification of known metabolites, structure determination of unknown metabolites and standardized sample preparation for quantitative comparisons. Recent research has demonstrated that some of these challenges can be substantially alleviated with the help of nanoscience. Nanoparticles in particular have found applications in various areas of bioanalytical chemistry and metabolomics. Their chemical surface properties and increased surface-to-volume ratio endows them with a broad range of binding affinities to biomacromolecules and metabolites. The specific interactions of nanoparticles with metabolites or biomacromolecules help, for example, simplify metabolomics spectra, improve the ionization efficiency for mass spectrometry or reveal relationships between spectral signals that belong to the same molecule. Lessons learned from nanoparticle-assisted metabolomics may also benefit other emerging areas, such as nanotoxicity and nanopharmaceutics.

Recent progress in surface-enhanced Raman spectroscopy for biological and biomedical applications: from cells to clinics

The application of surface-enhanced Raman spectroscopy (SERS) in biological and biomedical detection schemes is feasible due to its excellent molecular specificity and high sensitivity as well as the capability of SERS to be performed in complex biological compositions. SERS-based investigation of cells, which are the basic structure and functional unit of organisms, represents the starting point of this review. It is demonstrated that SERS provides a deep understanding of living cells as well as their microenvironment which is needed to assess the development of diseases. The clinical relevance of SERS is proved by its application for the detection of cancer cells and tumour margins under in vivo conditions and examples for theranostic approaches are discussed. This review article provides a comprehensive overview of the recent progress within the last 3 years.

Nanoparticle-Cell Interactions: Relevance for Public Health

Nanoparticles, especially metal oxide nanoparticles, are used in a wide range of commercial and industrial applications that result in direct human contact, such as titanium dioxide nanoparticles in paints, food colorings, and cosmetics, or indirectly through release of nanoparticle-containing materials into the environment. Workers who process nanoparticles for downstream applications are exposed to especially high concentrations of nanoparticles. For physical chemists, nanoparticles present an interesting area of study as the small size of nanoparticles changes the properties from that of the bulk material, leading to novel properties and reactivity. For the public health community, this reduction in particle size means that exposure limits and outcomes that were determined from bulk material properties are not necessarily valid. Informed determination of exposure limits requires a fundamental understanding of how nanoparticles interact with cells. This Feature Article highlights the areas of intersection between physical chemistry and public health in understanding nanoparticle-cell interactions, with a focus on titanium dioxide nanoparticles. It provides an overview of recent research examining the interaction of titanium dioxide nanoparticles with cells in the absence of UV light and provides recommendations for additional nanoparticle-cell research in which physical chemistry expertise could help to inform the public health community.

Myoglobin and Polydopamine-Engineered Raman Nanoprobes for Detecting, Imaging, and Monitoring Reactive Oxygen Species in Biological Samples and Living Cells

Highly reliable detection, imaging, and monitoring of reactive oxygen species (ROS) are critical for understanding and studying the biological roles and pathogenesis of ROS. This study describes the design and synthesis of myoglobin and polydopamine-engineered surface-enhanced Raman scattering (MP-SERS) nanoprobes with strong, tunable SERS signals that allow for specifically detecting and imaging ROS sensitively and quantitatively. The study shows that a polydopamine nanolayer can facilitate the modification of Raman-active myoglobins and satellite Au nanoparticles (s-AuNPs) to a plasmonic core AuNP (c-AuNP) in a controllable manner and the generation of plasmonically coupled hot spots between a c-AuNP and s-AuNPs that can induce strong SERS signals. The six-coordinated Fe(III)-OH₂ of myoglobins in plasmonic hotspots is reacted with ROS (H₂ O₂ , •OH, and O₂^- ) to form Fe(IV)O. The characteristic Raman peaks of Fe(IV)O from the Fe-porphyrin is used to analyze and quantify ROS. This chemistry allows for these probes to detect ROS in solution and image ROS in cells in a highly designable, specific, and sensitive manner. This work shows that these MP-SERS probes allow for detecting and imaging ROS to differentiate cancerous cells from noncancerous cells. Importantly, for the first time, SERS-based monitoring of the autophagy process in living cells under starvation conditions is validated.

Utilizing light-triggered plasmon-driven catalysis reactions as a template for molecular delivery and release

Due to the facile manipulation and non-invasive nature of light-triggered release, it is one of the most potent ways to selectively and remotely deliver a molecular target. Among the various carrier platforms, plasmonic nanoparticles possess advantages such as enhanced cellular uptake and easy loading of "cargo" molecules. Two general strategies are currently utilized to achieve light-induced molecule release from plasmonic nanoparticles. The first uses femtosecond laser pulses to directly break the bond between the nanoparticle and the loaded target. The other requires significant photo-thermal effects to weaken the interaction between the cargo molecules and nanoparticle-attached host molecules. Different from above mechanisms, herein, we introduce a new light-controlled molecular-release method by taking advantage of a plasmon-driven catalytic reaction at the particle surface. In this strategy, we link the target to a plasmon responsive molecule, 4-aminobenzenethiol (4-ABT), through the robust and simple EDC coupling reaction and subsequently load the complex onto the particles via the strong Au-thiol interaction. Upon continuous-wave (CW) laser illumination, the excited surface plasmon catalyzes the formation of 4,4'-dimercaptoazobenzenethiol (DMAB) and simultaneously releases the loaded molecules with high efficiency. This method does not require the use of high-power pulsed lasers, nor does it rely on photo-thermal effects. We believe that plasmon-driven release strategies open a new direction for the designing of next-generation light-triggered release processes.

Photoelectrochemical Bioanalysis Platform for Cells Monitoring Based on Dual Signal Amplification Using in Situ Generation of Electron Acceptor Coupled with Heterojunction

By using in situ generation of electron acceptor coupled with heterojunction as dual signal amplification, a simple photoelectrochemical (PEC) bioanalysis platform was designed. The synergic effect between the photoelectrochemical (PEC) activities of carbon nitride (C₃N₄) nanosheets and PbS quantum dots (QDs) achieved almost nine-fold photocurrent intensity increment compared with the C₃N₄ alone. After the G-quadruplex/hemin/Pt nanoparticles (NPs) with catalase-like activity toward H₂O₂ were introduced, oxygen was in situ generated and acted as electron donor by improving charge separation efficiency and further enhancing photocurrent response. The dually amplified signal made enough sensitivity for monitoring H₂O₂ released from live cells. The photocathode was prepared by the stepwise assembly of C₃N₄ nanosheets and PbS QDs on indium tin oxide (ITO) electrode, which was characterized by scanning electron microscope. A signal-on protocol was achieved for H₂O₂ detection in vitro due to the relevance of photocurrent on the concentration of H₂O₂. Under the optimized condition, the fabricated PEC bioanalysis platform exhibited a linear range of 10-7000 μM with a detection limit of 1.05 μM at S/N of 3. Besides, the bioanalysis platform displayed good selectivity against other reductive biological species. By using HepG2 cells as a model, a dual signal amplifying PEC bioanalysis platform for monitoring cells was developed. The bioanalysis platform was successfully applied to the detection of H₂O₂ release from live cells, which provided a novel method for cells monitoring and would have prospect in clinical assay.

Small and Sharp Triangular Silver Nanoplates Synthesized Utilizing Tiny Triangular Nuclei and Their Excellent SERS Activity for Selective Detection of Thiram Residue in Soil

The great harm of thiram residue in soil to environment and human health is usually ignored. Due to the complexity of soil compositions, the detection of thiram residue in soil faces considerable difficulties. In this work, a highly sensitive and selective surface-enhanced Raman scattering (SERS) substrate based on the triangular silver nanoplates (TSNPs) with small size and sharp corners is developed and used for the detection of thiram residue in soil for the first time. These TSNPs are synthesized by replacing the conventional seeds in the seed-mediated chemical reduction route with the tiny and uniform triangular silver nuclei (TSN) which can provide more growing space for generating sharp corners during the growth of TSNPs. It is interesting that the TSNPs with the smaller size have the better SERS performance. The possible mechanism behind this phenomenon is explained by the electromagnetic enhancement theory. On the basis of the Raman activity of the smallest TSNPs, a SERS-active substrate is prepared for detecting the thiram residue in soil. The thiram solution detection shows that the limit of detection (LOD) of these smallest TSNPs is lower than other nanoparticles, such as nanospheres, nanocubes, etc. For sensing the thiram residue in soil, the addition of poly(sodium 4-styrenesulfonate) realizes the specific adsorption of thiram by TSNPs. This method exhibits a good linear response from 0.12 to 4.8 μg/g with a low LOD of 90 ng/g, which is better than conventional methods. This work shows the great potential of the small TSNPs as a novel SERS substrate and its broader applications in pesticides detection.

A Gelated Colloidal Crystal Attached Lens for Noninvasive Continuous Monitoring of Tear Glucose

Patients of diabetes mellitus urgently need noninvasive and continuous glucose monitoring in daily point-of-care. As the tear glucose concentration has a positive correlation with that in blood, the hydrogel colloidal crystal integrated into contact lens possesses promising potential for noninvasive monitoring of glucose in tears. This paper presents a new glucose-responsive sensor, which consists a crystalline colloidal array (CCA) embedded in hydrogel matrix, attached onto a rigid gas permeable (RGP) contact lens. This novel sensing lens is able to selectively diffract visible light, whose wavelength shifts between 567 and 468 nm according to the alternation of the glucose concentration between 0 and 50 mM and its visible color change between reddish yellow, green, and blue. The detection limit of responsive glucose concentration can be reduced to 0.05 mM. Its combination with a contact lens endows it with excellent biocompatibility and portability, which shows great possibility for it to push the development of glucose-detecting devices into new era.

Electrochemical Detection of Hydrogen Peroxide by Inhibiting the p-Benzenediboronic Acid-Triggered Assembly of Citrate-Capped Au/Ag Nanoparticles on Electrode Surface

Metal nanoparticles (NPs) possess unique physicochemical attributes for creating effective recognition and transduction processes in chem/bio-sensing. In this work, we suggested that citrate-capped Au/Ag NPs could be used as the reporters for the design of hydrogen peroxide (H₂O₂) sensors with a simple manipulation principle and an easy detection procedure. Specifically, p-benzenediboronic acid (BDBA) induced the aggregation of citrate-capped Au NPs through the cross-linking reaction between citrate and boronic acid of BDBA in solution. By modifying the electrode with a boronic acid derivative, the BDBA-induced assembly of Au NPs was achieved on the electrode surface. This led to a significant decrease in the electron transfer resistance due to the unique conductive ability of Au NPs. However, when the boronate group on the electrode surface was oxidized into its phenol format, the assembly of Au NPs on the electrode surface was not achieved. As a result, a higher electron transfer resistance was observed. The process could be monitored by electrochemical impedance technique. Furthermore, when Ag NPs were used instead of Au NPs in this design, the H₂O₂ concentration could be determined by measuring the linear-sweep voltammetry (LSV) current through the solid-state Ag/AgCl reaction of Ag NPs. The results indicated that NP-based colorimetric assays could be developed into more sensitive electrochemical analysis.

Gold–platinum bimetallic nanoclusters with enhanced peroxidase-like activity and their integrated agarose hydrogel-based sensing platform for the colorimetric analysis of glucose levels in serum

Bimetallic Au–PtNCs with enhanced peroxidase-like activity were integrated into agarose hydrogels for direct visualization of glucose in human serum.

Acylboranes: synthetic strategies and applications

Acylboranes are an attractive class of compounds, of which the synthesis has very recently been documented as summarised in this review. Access to these compounds provides a path to study their properties and reactivity.

Electrochemical Synthesis of Polypyrrole, Reduced Graphene Oxide, and Gold Nanoparticles Composite and Its Application to Hydrogen Peroxide Biosensor

Here we report a facile eco-friendly one-step electrochemical approach for the fabrication of a polypyrrole (PPy), reduced graphene oxide (RGO), and gold nanoparticles (nanoAu) biocomposite on a glassy carbon electrode (GCE). The electrochemical behaviors of PPy–RGO–nanoAu and its application to electrochemical detection of hydrogen peroxide were investigated by cyclic voltammetry. Graphene oxide and pyrrole monomer were first mixed and casted on the surface of a cleaned GCE. After an electrochemical processing consisting of the electrooxidation of pyrrole monomer and simultaneous electroreduction of graphene oxide and auric ions (Au³⁺) in aqueous solution, a PPy–RGO–nanoAu biocomposite was synthesized on GCE. Each component of PPy–RGO–nanoAu is electroactive without non-electroactive substance. The obtained PPy–RGO–nanoAu/GCE exhibited high electrocatalytic activity toward hydrogen peroxide, which allows the detection of hydrogen peroxide at a negative potential of about −0.62 V vs. SCE. The amperometric responses of the biosensor displayed a sensitivity of 40 µA/mM, a linear range of 32 µM–2 mM, and a detection limit of 2.7 µM (signal-to-noise ratio = 3) with good stability and acceptable reproducibility and selectivity. The results clearly demonstrate the potential of the as-prepared PPy–RGO–nanoAu biocomposite for use as a highly electroactive matrix for an amperometric biosensor.