Thermal self-regulatory intelligent biosensor based on carbon-nanotubes-decorated phase-change microcapsules for enhancement of glucose detection

Atomic Force Microscopy Study of the Long-Term Effect of the Glycerol Flow, Stopped in a Coiled Heat Exchanger, on Horseradish Peroxidase

Glycerol is employed as a functional component of heat-transfer fluids, which are of use in both bioreactors and various biosensor devices. At the same time, flowing glycerol was reported to cause considerable triboelectric effects. Herein, by using atomic force microscopy (AFM), we have revealed the long-term effect of glycerol flow, stopped in a ground-shielded coiled heat exchanger, on horseradish peroxidase (HRP) adsorption on mica. Namely, the solution of HRP was incubated in the vicinity of the side of the cylindrical coil with stopped glycerol flow, and then HRP was adsorbed from this solution onto a mica substrate. This incubation has been found to markedly increase the content of aggregated enzyme on mica-as compared with the control enzyme sample. We explain the phenomenon observed by the influence of triboelectrically induced electromagnetic fields of non-trivial topology. The results reported should be further considered in the development of flow-based heat exchangers of biosensors and bioreactors intended for operation with enzymes.

Nanoparticle-Empowered Core-Shell Microcapsules: From Architecture Design to Fabrication and Functions

Compartmentalization is a powerful concept to integrate multiscale components with diverse functionalities into miniature architectures. Inspired by evolution-optimized cell compartments, synthetic core-shell capsules enable storage of actives and on-demand delivery of programmed functions, driving scientific progress across various fields including adaptive materials, sustainable electronics, soft robotics, and precision medicine. To simultaneously maximize structural stability and environmental sensitivity, which are the two most critical characteristics dictating performance, diverse nanoparticles are incorporated into microcapsules with a dense shell and a liquid core. Recent studies have revealed that these nano-additives not only enhance the intrinsic properties of capsules including mechanical robustness, optical behaviors, and thermal conductivity, but also empower dynamic features such as triggered release, deformable structures, and fueled mobility. In this review, the physicochemical principles that govern nanoparticle assembly during microencapsulation are examined in detail and the architecture-controlled functionalities are outlined. Through the analysis of how each primary method implants nanoparticles into microcapsules, their distinct spatial organizations within the core-shell structures are highlighted. Following a detailed discussion of the specialized functions enabled by specific nanoparticles, the vision of the required fundamental insights and experimental studies for this class of microcarriers to fulfill its potential are sketched.

Fully integrated wearable microneedle biosensing platform for wide-range and real-time continuous glucose monitoring

Wearable microneedle sensors for continuous glucose monitoring (CGM) have great potential for clinical impact by allowing access to large data sets to provide individualized treatment plans. To date, their development has been challenged by the accurate wide linear range tracking of interstitial fluid (ISF) glucose (Glu) levels. Here, we present a CGM platform consisting of a three-electrode microneedle electrochemical biosensor and a fully integrated radio-chemical analysis system. The long-term performance of the robust CGM on diabetic rats was achieved by electrodepositing Prussian blue (PB), and crosslinking glucose oxidase (GOx) and chitosan to form a 3D network using glutaraldehyde (GA). After redox by GOx, PB rapidly decomposes hydrogen peroxide and mediates charge transfer, while the 3D network and graphite powder provide enrichment and release sites for Glu and catalytic products, enabling a sensing range of 0.25-35 mM. Microneedle CGM has high sensitivity, good stability, and anti-interference ability. In diabetic rats, CGM can accurately monitor Glu levels in the ISF in real-time, which are highly consistent with levels measured by commercial Glu meters. These results indicate the feasibility and application prospects of the PB-based CGM for the clinical management of diabetes. STATEMENT OF SIGNIFICANCE: This study addresses the challenge of continuous glucose monitoring system design where the narrow linear range of sensing due to the miniaturization of sensors fails to meet the monitoring needs of clinical diabetic patients. This was achieved by utilizing a three-dimensional network of glutaraldehyde cross-linked glucose oxidase and chitosan. The unique topology of the 3D network provides a large number of sites for glucose enrichment and anchors the enzyme to the sensing medium and the conductive substrate through covalent bonding, successfully blocking the escape of the enzyme and the sensing medium and shortening the electron transfer and transmission path.

Trace identification of cysteine enantiomers based on an electrochemical sensor assembled from CuxS@SOD zeolite

The nonchiral sensor concept based on a sodalite (SOD) zeolite loaded CuxS (CuxS@SOD) catalyst is proposed as a sensing platform for chiral cysteine (Cys) determination. Chiral Cys is analyzed by the difference of binding capacity between CuxS catalysts. The observed current in amperometric i-t curve (A i-t C) is always positive for the L-cysteine (L-Cys), while it is negative for the D-cysteine (D-Cys). Under differential pulse voltammetry (DPV) method, the characteristic current peak for the CuxS@SOD moves to right (positive potential position) with the addition of L-Cys while it moves to left (negative potential direction) with the addition of D-Cys, respectively. Cyclic voltammetry (CV) is consistent with DPV and discusses the diffusion control mechanism. In this work, the ultra-trace determination of cysteine enantiomers reaches the limit of detection (LOD) of 0.70 fM and 0.60 fM by the highly efficient CuxS catalyst restrained in the nanosized SOD zeolite cages of the opening window pores, respectively. The sensor opens up a novel potential prospect for achiral composite in the field of chiral recognition through electrochemical methods with extra-low concentration.

Gold Nanoparticle-Based Colorimetric Sensors: Properties and Application in Detection of Heavy Metals and Biological Molecules

During the last decade, advances have been made in nanotechnology using nanomaterials, leading to improvements in their performance. Gold nanoparticles (AuNPs) have been widely used in the field of sensor analysis and are also combined with certain materials to obtain the desired characteristics. AuNPs are commonly used as colorimetric sensors in detection methods. In developing an ideal sensor, there are certain characteristics that must be met such as selectivity, sensitivity, accuracy, precision, and linearity, among others. Various methods for the synthesis of AuNPs and conjugation with other components have been carried out in order to obtain good characteristics for their application. AuNPs can be applied in the detection of both heavy metals and biological molecules. This review aimed at observing the role of AuNPs in its application. The synthesis of AuNPs for sensors will also be revealed, along with their characteristics suitable for this role. In the application method, the size and shape of the particles must be considered. AuNPs used in heavy metal detection have a particle size of around 15-50 nm; in the detection of biological molecules, the particle size of AuNPs used is 6-35 nm whereas in pharmaceutical compounds for cancer treatment and the detection of other drugs, the particle size used is 12-30 nm. The particle sizes did not correlate with the type of molecules regardless of whether it was a heavy metal, biological molecule, or pharmaceutical compound but depended on the properties of the molecule itself. In general, the best morphology for application in the detection process is a spherical shape to obtain good sensitivity and selectivity based on previous studies. Functionalization of AuNPs with conjugates/receptors can be carried out to increase the stability, sensitivity, selectivity, solubility, and plays a role in detecting biological compounds through conjugating AuNPs with biological molecules.

The Use of Crystalline Carbon-Based Nanomaterials (CBNs) in Various Biomedical Applications

This review study aims to present, in a condensed manner, the significance of the use of crystalline carbon-based nanomaterials in biomedical applications. Crystalline carbon-based nanomaterials, encompassing graphene, graphene oxide, reduced graphene oxide, carbon nanotubes, and graphene quantum dots, have emerged as promising materials for the development of medical devices in various biomedical applications. These materials possess inorganic semiconducting attributes combined with organic π-π stacking features, allowing them to efficiently interact with biomolecules and present enhanced light responses. By harnessing these unique properties, carbon-based nanomaterials offer promising opportunities for future advancements in biomedicine. Recent studies have focused on the development of these nanomaterials for targeted drug delivery, cancer treatment, and biosensors. The conjugation and modification of carbon-based nanomaterials have led to significant advancements in a plethora of therapies and have addressed limitations in preclinical biomedical applications. Furthermore, the wide-ranging therapeutic advantages of carbon nanotubes have been thoroughly examined in the context of biomedical applications.

Impact of nanotechnology on conventional and artificial intelligence-based biosensing strategies for the detection of viruses

Recent years have witnessed the emergence of several viruses and other pathogens. Some of these infectious diseases have spread globally, resulting in pandemics. Although biosensors of various types have been utilized for virus detection, their limited sensitivity remains an issue. Therefore, the development of better diagnostic tools that facilitate the more efficient detection of viruses and other pathogens has become important. Nanotechnology has been recognized as a powerful tool for the detection of viruses, and it is expected to change the landscape of virus detection and analysis. Recently, nanomaterials have gained enormous attention for their value in improving biosensor performance owing to their high surface-to-volume ratio and quantum size effects. This article reviews the impact of nanotechnology on the design, development, and performance of sensors for the detection of viruses. Special attention has been paid to nanoscale materials, various types of nanobiosensors, the internet of medical things, and artificial intelligence-based viral diagnostic techniques.

Portable reduced graphene oxide biosensor for detection of rabies virus in bats using nasopharyngeal swab samples

Rabies is a lethal zoonotic disease caused by rabies virus (RABV) that affects human health and the economy. RABV is transmitted mainly by bats in Brazil, and surveillance in remote areas is hampered by the difficulty of properly collecting samples during fieldwork and the diagnosis is performed in laboratory conditions. Here, we report a portable electrochemical biosensor based on nucleic acid interactions for RABV detection in nasopharyngeal swab samples. The working electrode of the biosensor is composed of reduced graphene oxide (rGO) thin-film immobilized with cDNA through pi-pi stacking to enhance virus detection and specificity. Sensor performance was determined using RNA, and swab samples from bats. RNA detection shows good selectivity, and quantification presents a highly linear calibration curve (R² = 0.990) using a concentration range of 0.145-25.39 ng/μL. A LOD of 0.104 ng/μL was reached with a sensitivity of 0.321 μA (ng/μL)^-1. RABV detection in nasopharyngeal swab samples showed a good difference of positive sample from negative with a response time in seconds, ultra-fast detection compared to known techniques. Three biosensor groups were identified and named after physic-chemical surface characterization as: GO-1, GO-2, and rGO; with best performance for rGO group due to its sp² hybridized network. Thus, we have successfully fabricated a promising electrochemical biosensor for fast in-situ detection of the RABV in swab samples, which can be expanded to other enveloped viruses that have RNA.

Carbon Nanotube and Its Derived Nanomaterials Based High Performance Biosensing Platform

After the COVID-19 pandemic, the development of an accurate diagnosis and monitoring of diseases became a more important issue. In order to fabricate high-performance and sensitive biosensors, many researchers and scientists have used many kinds of nanomaterials such as metal nanoparticles (NPs), metal oxide NPs, quantum dots (QDs), and carbon nanomaterials including graphene and carbon nanotubes (CNTs). Among them, CNTs have been considered important biosensing channel candidates due to their excellent physical properties such as high electrical conductivity, strong mechanical properties, plasmonic properties, and so on. Thus, in this review, CNT-based biosensing systems are introduced and various sensing approaches such as electrochemical, optical, and electrical methods are reported. Moreover, such biosensing platforms showed excellent sensitivity and high selectivity against not only viruses but also virus DNA structures. So, based on the amazing potential of CNTs-based biosensing systems, healthcare and public health can be significantly improved.

Immobilizing diamine oxidase on electroactive phase-change microcapsules to construct thermoregulatory smart biosensor for enhancing detection of histamine in foods

Aiming at enhancing the biosensing detection of histamine in foods at high temperature, we developed a thermoregulatory biosensor based on diamine oxidase-immobilized phase-change microcapsules consisting of an n-docosane core, a TiO₂ shell, and an electroactive polyaniline/ZnO composite coating layer. The microcapsules exhibit a satisfactory latent heat capacity of over 112 J/g for thermo-temperature regulation. Through an innovative integration of electroactive phase-change microcapsules and biological enzyme in the working electrode, the biosensor obtained a thermoregulatory function through reversible phase transitions by the n-docosane core under high-temperature environments. This enables the biosensor to achieve a higher response sensitivity of 28.57 µA⋅mM^-1⋅cm^-2 and a lower detection limit of 0.473 µmol/L at the high assay temperatures compared to conventional histamine biosensors. With enhanced electrochemical biosensing performance through in-situ thermo-temperature regulation, the smart biosensor developed in this study has found practical applications for high-sensitive detection and high-accurate quantitive determination of histamine in foods across a broad temperature range.

Preparation of boronic acid-modified polymer dots under mild conditions and their applications in pH and glucose detection

For the first time, boronic acid-modified polymer dots (B-PDs) were fabricated by a "synthesis-modification integration" route using polyethylenimine (PEI) and phenylboronic acid as precursors. Under optimized preparation conditions, the B-PDs exhibited an average size of 2.2 nm, good water solubility, and high fluorescence quantum yield of 8.69%. The B-PDs showed reversible fluorescence response in acid solutions (blue emissions) and alkaline solutions (green emissions). The fluorescence emissions of B-PDs demonstrated an obvious red shift with varying the pH value from 1 - 13. Moreover, glucose could assemble on the surface of B-PDs due to the reversible reaction between boronic acid and cis-diols, which resulted in a blue shift of emission wavelength and an obvious increase of FL intensity at λ_ex = 380 nm based on the aggregation-induced enhancement effect. The glucose sensing method was thus developed in the range 0.0001 - 1.0 mol L^-1. Applications to real human blood and glucose injection samples demonstrated satisfactory results. The B-PDs based on the analytical method display good selectivity, wide detection range, and simplicity in preparation and detection, implying promising applications as a practical platform for biosensing.