Zein film as a novel natural biopolymer membrane in electrochemical detections

Laser-induced graphene electrode modified by platinum nanoparticle/zein/gelatin/glucose oxidase for non-invasive glucose sensor in multiple biofluids

BACKGROUND

A non-invasive glucose biosensor for multiple biofluids based on platinum nanoparticle (Pt-NP)-modified laser-induced graphene (LIG) electrodes coated with a zein/gelatin/glucose oxidase (GOx) for amperometric detection of glucose is created. The biosensor fabrication is cost-effective and scalable, as it combines simple LIG electrode fabrication with direct Pt-NP electrodeposition and a sequence of drop-and-dry steps for zein and gelatin layer then GOx enzyme. The Pt-NP modification on the LIG electrode functions as an electrocatalyst to enhance the anodic H2O2 signal, which is directly proportional to glucose concentration. The zein layer acts as a diffusion barrier to mitigate potential interferences, while the gelatin film provides amine groups for the glutaraldehyde-mediated immobilization of the GOx enzyme.

RESULTS

The key parameters of LIG were optimized, such as power laser, number of Pt-NP cycles, and zein concentration. In addition, LIG was characterized by Raman spectroscopy, SEM, and cyclic voltammetry (CV) to ensure graphitization and electron transfer performance. The as prepared LIG/Pt-NP/Zein/Gel-GOx glucose biosensor was in anodic H2O2 detection mode and tested for glucose measurements in multiple biofluids including sweat, saliva, and urine. At H2O2 detection potential of +0.4 V, a linear detection range from 0 up to 2 mM glucose was obtained with a limit of detection (LOD) of 0.01 mM, making it feasible for glucose determination in various clinically relevant biofluids. By comparing with the commercial SPE, this LIG-based sensor offered much higher detection sensitivity towards both H2O2 and glucose, making it a superior choice for electrochemical analysis.

SIGNIFICANCE

This LIG/Pt-NPs/Zein/Gel-GOx offers a practical and high sensitivity approach to glucose measurement with a wide linearity for multiple biofluids. Given the straightforward and easily scalable process, this high-performance, LIG-based glucose biosensor presents a compelling alternative over commercial screen-printed electrode. Highlighted the novelty using zein as a protective layer to reduce interferences. Owing to the simplicity of fabrication with high potential for up-scaling, this high analytical performance biosensor might be an alternative tool for multiplex glucose biosensors in point-of-care applications.

Smartphone-based electrochemical sensor for cost-effective, rapid and on site detection of chlorogenic acid in herbs using biomass-derived hierarchically porous carbon synthesized by a soft-hard dual template method

To achieve excellent germplasm resource screening and ensure the quality control of herbal tea raw material, it is important to establish a cost-effective, rapid, and on site quantitative detection method for their bioactive constituents. We developed a smartphone-operated sensor for electrochemical detection of chlorogenic acid (CGA) using hierarchically porous carbon (DSiFPC), synthesized through a soft-hard dual template strategy with tannin acid as a carbon source, silica colloid as a hard template, and Pluronic F127 as a soft template. The DSiFPC modified glassy carbon electrode sensor showed excellent electrocatalytic ability towards CGA, with a wide linear range of 0.03-1 μM and a low limit of detection of 6.2 nM. It was successfully applied for detecting CGA in dried flowers of Lonicera japonica. Furthermore, a portable sensor utilizing a DSiFPC modified screen-printed electrode was employed for on site detection of CGA in fresh Eucommia ulmoides leaves, yielding satisfactory recoveries.

Performance and Structure Evaluation of Gln-Lys Isopeptide Bond Crosslinked USYK-SPI Bioplastic Film Derived from Discarded Yak Hair

To reduce the waste from yak hair and introduce resource recycling into the yak-related industry, an eco-friendly yak keratin-based bioplastic film was developed. We employed yak keratin (USYK) from yak hair, soy protein isolate (SPI) from soybean meal as a film-forming agent, transglutaminase (EC 2.3.2.13, TGase) as a catalytic crosslinker, and glycerol as a plasticizer for USYK-SPI bioplastic film production. The structures of the USYK-SPI bioplastic film were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-Ray diffraction (XRD). The mechanical properties, the thermal behavior, light transmittance performance, and water vapor permeability (WVP) were measured. The results revealed that the added SPI possibly acted as a reinforcement. The formation of Gln-Lys isopeptide bonds and hydrophobic interactions led to a stable crosslinking structure of USYK-SPI bioplastic film. The thermal and the mechanical behaviors of the USYK-SPI bioplastic film were improved. The enhanced dispersion and formation of co-continuous protein matrices possibly produced denser networks that limited the diffusion of water vapor and volatile compounds in the USYK-SPI bioplastic films. Moreover, the introduction of SPI prompted the relocation of hydrophobic groups on USYK molecules, which gave the USYK-SPI bioplastic film stronger surface hydrophobicity. The SPI and USYK molecules possess aromatic amino residuals (tyrosine, phenylalanine, tryptophan), which can absorb ultraviolet radiation. Thus, the USYK-SPI bioplastic films were shown to have an excellent UV barrier. The synergy effect between USYK and SPI is not only able to improve rigidity and the application performance of keratin-based composite film but can also reduce the cost of the keratin-based composite film through the low-cost of the SPI alternative which partially replaces the high-cost of keratin. The data obtained from this research can provide basic information for further research and practical applications of USYK-SPI bioplastic films. There is an increasing demand for the novel USYK-SPI bioplastic film in exploit packaging material, biomedical materials, eco-friendly wearable electronics, and humidity sensors.