Recent advances in glucose-oxidase-based nanocomposites for diabetes diagnosis and treatment

Glucose oxidase (GOx) has attracted a lot of attention in the field of diabetes diagnosis and treatment in recent years owing to its inherent biocompatibility and glucose-specific catalysis. GOx can effectively catalyze the oxidation of glucose in the blood to hydrogen peroxide (H2O2) and glucuronic acid and can be used as a sensitive element in biosensors to detect blood glucose concentrations. Nanomaterials based on the immobilization of GOx can significantly improve the performance of glucose sensors through, for example, reduced electron tunneling distance. Moreover, various insulin-loaded nanomaterials (e.g., metal-organic backbones, and mesoporous silica nanoparticles) have been developed for the control of blood glucose concentrations based on GOx catalytic chemistry. These nano-delivery carriers are capable of releasing insulin in response to GOx-mediated changes in the microenvironment, allowing for a rapid return of the blood microenvironment to a normal state. Therefore, glucose biosensors and insulin delivery vehicles immobilized with GOx are important tools for the diagnosis and treatment of diabetes. This paper reviews the characteristics of various GOx-based nanomaterials developed for glucose biosensing and insulin-responsive release as well as research progress, and also highlights the current challenges and opportunities facing this field.

Size-dependent fluorescence of conjugated polymer dots and correlation with the fluorescence in solution and in the solid phase of the polymer

Three conjugated polymers (CPs) were synthesized to obtain CPs with the same backbone but with different compositions of repeat units (phenylene and benzoselenadiazole (BSD)). The dominant composition of phenylene units and a smaller amount of BSD in the CP backbone enabled the CPs to emit different fluorescence colors according to their condition (solution or solid), which was caused by the difference in intermolecular electron transfer between CP backbones. Inspired by this, we fabricated polymer dots (Pdots) with various sizes using the CPs to control the number of CP chains within a spherical Pdot. This implied that smaller Pdots, where the chance of intermolecular electron transfer would be at a minimum, would accommodate fewer polymer chains than larger ones. The minimum chance for intermolecular electron transfer resulted in a short-wavelength emission, which was the identical emission color encountered in liquid CP solution. A more frequent intermolecular electron transfer was expected in larger Pdots, exhibiting long-wavelength emission, which was the same as observed in solid CPs. White-light-emitting Pdots that showed Commission Internationale de 1'Eclairage (CIE) coordinates of (0.34, 0.31) were fabricated simply by controlling the Pdot size.

Electrophoresis Titration Model of a Moving Redox Boundary Chip for a Point-of-Care Test of an Enzyme-Linked Immunosorbent Assay

Enzyme-linked immunosorbent assays (ELISAs) have been widely used in clinical examination, food safety, and environmental analyses. However, they still face a great challenge in designing a device for a point-of-care test (POCT) due to its bulk optical detector and complexity. Herein an electrophoresis titration (ET) model of a moving redox boundary (MRB) was proposed for constructing an ET-ELISA chip of a POCT just with sextuplet electrode pairs and laminated cells. The chip had an anodic well, middle well, and cathode well which were connected by microchannels. The ELISA process was conducted in the bottom of the middle well, where horseradish peroxidase (HRP) catalyzed 3,3',5,5'-tetra-methyl benzidine (TMB) as a blue TMB dimer with two positive charges. Under an electrical field of 29 V, the TMB dimer migrated into the titration channel and reacted with the ascorbic acid, creating an MRB. The MRB motion was a function of antigen content, indicating a visual distance-based assay. As a proof of concept, a C-reactive protein was chosen as a model antigen. The experiments systemically validated the ET-ELISA model and method. Particularly, the chip was smartphone-detected, traditional power supply free, and did not use sulfuric acid used in typical ELISA, making the ET-ELISA method extremely simple, portable, and safe. The ET-ELISA has great potential to visual and portable ELISA in clinical medicine, the environment, and food safety immunoassay.

Recent Progress in Chemosensors Using Aldehyde-bearing Fluorophores for the Detection of Specific Analytes and their Bioimaging

In recent years, aldehyde-appended fluorescence probes have attracted increasing attention. Fluorescent biological imaging includes many modern applications for cell and tissue imaging in biomedical research. Meanwhile, the nucleophilic mechanism is a very simple and convenient procedure for the preparation of aldehyde-sensing probes. This tutorial review focuses on aldehyde-bearing chemosensors based on nucleophilic addition mechanism with biological applications.

Emission Tuning with Size-Controllable Polymer Dots from a Single Conjugated Polymer

Two conjugated polymers (CPs) with various compositions of phenylene and benzoselenadiazoben (BSD) are synthesized to have a special emitting property; different fluorescence colors in solution and in the solid states, allowing the resulting conjugated polymer dots (Pdots) to emit different fluorescence colors upon their size variation. The photophysical property of such different-sized Pdots is investigated using fluorescence spectra and fluorescence lifetimes. A decrease in the fluorescence lifetime of Pdots is observed with an increase in the size of Pdots, caused by quantitative change in energy transfer from phenylene (energy donor) to the BSD unit (energy acceptor). The results provide that any CP can be used for the fabrication of Pdots with size-tunable emission, as long as the CP shows different emissions according to its phases. Such emission of Pdots can even be observed when in the solid solution in polymer matrix, which emits different fluorescence colors depending on the size of embedded Pdots in the polymer matrix.

A rainbow ratiometric fluorescent sensor array on bacterial nanocellulose for visual discrimination of biothiols

The crucial role of biothiols in many biological processes, which turns them into important biomarkers for the early diagnosis of various diseases, the development of an affordable, sensitive and portable probe for the detection and discrimination of these compounds is of great importance.

Photoswitchable chromic behavior of conjugated polymer films for reversible patterning and construction of a logic gate

Photoswitchable fluorescent films were constructed using a conjugated polymer as a fluorescence-color changeable unit and a photochromic molecule as a phototriggered, selectively energy-accepting component.

Synthesis of poly(p-phenylene) containing a rhodamine 6G derivative for the detection of Fe(iii) in organic and aqueous media

A poly(p-phenylene) (PPP) containing rhodamine 6G (R6G) was synthesized by the Suzuki-coupling reaction, in which PPP acted as a blue-emitting energy donor and R6G acted as a ligand for Fe(iii) as well as the energy acceptor for Förster resonance energy transfer.

A Review on Microfluidic Paper-Based Analytical Devices for Glucose Detection

Glucose, as an essential substance directly involved in metabolic processes, is closely related to the occurrence of various diseases such as glucose metabolism disorders and islet cell carcinoma. Therefore, it is crucial to develop sensitive, accurate, rapid, and cost effective methods for frequent and convenient detections of glucose. Microfluidic Paper-based Analytical Devices (μPADs) not only satisfying the above requirements but also occupying the advantages of portability and minimal sample consumption, have exhibited great potential in the field of glucose detection. This article reviews and summarizes the most recent improvements in glucose detection in two aspects of colorimetric and electrochemical μPADs. The progressive techniques for fabricating channels on μPADs are also emphasized in this article. With the growth of diabetes and other glucose indication diseases in the underdeveloped and developing countries, low-cost and reliably commercial μPADs for glucose detection will be in unprecedentedly demand.

Fluorescence sensing of glucose using glucose oxidase incorporated into a fluorophore-containing PNIPAM hydrogel

We present a new composite material composed of pH sensitive fluorescent dyes in a poly(N-isopropylacrylamide)-based hydrogel and incorporating glucose oxidase (GOx), which provides a platform for fluorescence sensing of glucose.

Designing interchain and intrachain properties of conjugated polymers for latent optical information encoding

Based on systematic conjugated polymers design, we demonstrate latent information encoding which reveals and conceals hidden information upon polymers' aggregation/deaggregation.

Building molecular-design insights for controlling both the intrachain and the interchain properties of conjugated polymers (CPs) is essential to determine their characteristics and to optimize their performance in applications. However, most CP designs have focused on the conjugated main chain to control the intrachain properties, while the design of side chains is usually used to render CPs soluble, even though the side chains critically affect the interchain packing. Here, we present a straightforward and effective design strategy for modifying the optical and electrochemical properties of diketopyrrolopyrrole-based CPs by controlling both the intrachain and interchain properties in a single system. The synthesized polymers, P1, P2 and P3, show almost identical optical absorption spectra in solution, manifesting essentially the same intrachain properties of the three CPs having restricted effective conjugation along the main chain. However, the absorption spectra of CP films are gradually tuned by controlling the interchain packing through the side-chain design. Based on the tailored optical properties, we demonstrate the encoding of latent optical information utilizing the CPs as security inks on a silica substrate, which reveals and conceals hidden information upon the reversible aggregation/deaggregation of CPs.