A biocatalytic cascade in enzyme/metal continuous-microflow microgel with stable intermediate channel for point-of-care biosensing.

A fast and accurate method for ultrasensitive monitoring of substrate is significant for cascade molecular detection. Here, we synthesize a glucose oxidase (GOx) microgel with iron coordination (Fe/GOx microgel). The microgel is cross-linked by chitosan and iron ion coordination which construct a tubular structure. Powder X-ray diffraction and Brunauer-Emmett-Teller results confirm the tubular crystal structure with a high specific surface area is formed in the microgel. The tubular structure offers a stable channel for intermediate transport which ensures the stabilization for the intermediate transport, and high specific surface area enhances the interaction between substrates and catalysts. As a result, the sensitivity of the Fe/GOx microgel is 175.5 µA mM-1 cm-2 and the lowest detection limit is 4.42 µM. In addition, the nanoscale Fe/GOx microgel also has the characteristics of reusability and maintains its activity after five times of catalysis. The generation of free radicals during the catalytic process can be detected by light detection and electrochemical signal detection within different detection limits. Therefore, Fe/GOx microgel provides a new platform and catalyst for the precise detection of cascade catalysis.

Highly stable glucose oxidase polynanogel@MXene/chitosan electrochemical biosensor based on a multi-stable interface structure for glucose detection.

It is a challenging and meaningful task to design an enzyme electrochemical biosensor that can maintain high sensitivity while improving stability. In this study, we constructed an enzyme electrochemical biosensor by preparing nanocomposites with multi-stable interface structures. Specifically, the nanocomposite (PGOx@MXene/CS) was prepared by efficient electrostatic assembly of GOx polynanogel (PGOx) onto MXene nanosheets. PGOx could enhance enzyme stability, while the extensive the large specific surface area of MXene could realize the efficient loading of nanocapsules (PGOx) and catalyze the decomposition of toxic intermediate H2O2, thereby reducing its influence on the stability of enzyme. The linear range of the constructed glucose sensor was 0.03-16.5 mM, the sensitivity was 48.98 µA mM-1·cm-2, and the detection limit was 3.1 µM. After 200 cycles, the current still remained at 85.83% of the initial current value. The high sensitivity, excellent selectivity and great reproducibility verified the effectiveness of the system we constructed. The multi-stable enzyme electrochemical biosensor had a wide application prospect in stable and continuous blood glucose detection.

Construction of molecular enrichment accelerators via assembly of enzyme surface grafted polymer and cyclodextrin achieving rapid and stable ester catalysis for biodiesel synthesis.

Efficient and stable catalysis has always been the core concept of enzyme catalysis in industrial processes for manufacturing. Here, we constructed molecular enrichment accelerators to synergistically enhance enzyme activity and stability by assembling enzyme surface grafted polymer and cyclodextrin. At 40 °C, the enzyme activity of CalB-PNIPAM212/ß-CD was 2.9 times that of CalB-PNIPAM212. The enzyme activity of CalB-PNIPAM428/γ-CD had reached 1.61 times that of CalB. At the same time, the stability of CalB-PNIPAM212/ß-CD and CalB-PNIPAM428/γ-CD are slightly better than that of CalB under high temperature, organic solution and extreme pH conditions. The synergistic increase in activity and stability of the lipase-polymer assembly was achieved due to the structure of assembly, in which the role of cyclodextrin could enrich substrate affecting molecular diffusion. In addition, the lipase-polymer assembly proved to be an efficient catalyst for biodiesel synthesis, with a biodiesel conversion 1.4 times that of CalB at 60 °C. Therefore, this simple and low-cost lipase-polymer assembly provides new possibilities for the construction of high-efficiency industrial biocatalytic catalysts.