Combination of physico-chemical entrapment and crosslinking of low activity laccase-based biocathode on carboxylated carbon nanotube for increasing biofuel cell performance

Clay-polymer hybrid hydrogels in the vanguard of technological innovations for bioremediation, metal biorecovery, and diverse applications

Polymeric hydrogels are among the most studied materials due to their exceptional properties for many applications. In addition to organic and inorganic-based hydrogels, "hybrid hydrogels" have been gaining significant relevance in recent years due to their enhanced mechanical properties and a broader range of functionalities while maintaining good biocompatibility. In this sense, the addition of micro- and nanoscale clay particles seems promising for improving the physical, chemical, and biological properties of hydrogels. Nanoclays can contribute to the physical cross-linking of polymers, enhancing their mechanical strength and their swelling and biocompatibility properties. Nowadays, they are being investigated for their potential use in a wide range of applications, including medicine, industry, and environmental decontamination. The use of microorganisms for the decontamination of environments impacted by toxic compounds, known as bioremediation, represents one of the most promising approaches to address global pollution. The immobilization of microorganisms in polymeric hydrogel matrices is an attractive procedure that can offer several advantages, such as improving the preservation of cellular integrity, and facilitating cell separation, recovery, and transport. Cell immobilization also facilitates the biorecovery of critical materials from wastes within the framework of the circular economy. The present work aims to present an up-to-date overview on the different "hybrid hydrogels" used to date for bioremediation of toxic metals and recovery of critical materials, among other applications, highlighting possible drawbacks and gaps in research. This will provide the latest trends and advancements in the field and contribute to search for effective bioremediation strategies and critical materials recovery technologies.

Advances in laccase-triggered anabolism for biotechnology applications

This is the first comprehensive overview of laccase-triggered anabolism from fundamental theory to biotechnology applications. Laccase is a typical biological oxidordeuctase that induces the one-electronic transfer of diverse substrates for engendering four phenoxy radicals with concomitant reduction of O₂ into 2H₂O. In vivo, laccase can participate in anabolic processes to create multifarious functional biopolymers such as fungal pigments, plant lignins, and insect cuticles, using mono/polyphenols and their derivatives as enzymatic substrates, and is thus conducive to biological tissue morphogenesis and global carbon storage. Exhilaratingly, fungal laccase has high redox potential (E° = 500-800 mV) and thermodynamic efficiency, making it a remarkable candidate for utilization as a versatile catalyst in the green and circular economy. This review elaborates the anabolic mechanisms of laccase in initiating the polymerization of natural phenolic compounds and their derivatives in vivo via radical-based self/cross-coupling. Information is also presented on laccase immobilization engineering that expands the practical application ranges of laccase in biotechnology by improving the enzymatic catalytic activity, stability, and reuse rate. Particularly, advances in biotechnology applications in vitro through fungal laccase-triggered macromolecular biosynthesis may provide a key research direction beneficial to the rational design of green chemistry.

Soft Materials for Wearable/Flexible Electrochemical Energy Conversion, Storage, and Biosensor Devices

Next-generation wearable technology needs portable flexible energy storage, conversion, and biosensor devices that can be worn on soft and curved surfaces. The conformal integration of these devices requires the use of soft, flexible, light materials, and substrates with similar mechanical properties as well as high performances. In this review, we have collected and discussed the remarkable research contributions of recent years, focusing the attention on the development and arrangement of soft and flexible materials (electrodes, electrolytes, substrates) that allowed traditional power sources and sensors to become viable and compatible with wearable electronics, preserving or improving their conventional performances.

Immobilization of laccase on magnetically separable biochar for highly efficient removal of bisphenol A in water

Laccase was stably immobilized on a cost effective and nanosized magnetic biochar (L-MBC) by adsorption, precipitation and crosslinking, and it was used for high performance BPA removal. A large amount of enzyme could be immobilized on the magnetic biochar with high activity (2.251 U per mg MBC), and the L-MBC could be magnetically separated from the aqueous solution in 20 seconds. The successful immobilization of laccase was also confirmed via FTIR, SEM, and EDS analyses. The L-MBC presented better storage and stability performances, pH tolerance and thermal stability than the free laccase. It was found that BPA with an initial concentration of 25 mg L-1 could be thoroughly removed within 75 min, where BPA removal was attributed to enzymatic degradation and adsorption. In addition, the BPA removal efficiency by the L-MBC could be maintained above 85% even after seven cycles of repeated use. Due to high stability and efficient recyclability, the L-MBC-based biocatalyst has the potential to be a reliable method for treating BPA in environmental water sources.

Electrochemical Study of Enzymatic Glucose Sensors Biocatalyst: Thermal Degradation after Long-Term Storage

The thermal degradation related to stability in long-term storage of a carbon nanotube-based biosensor has been investigated. The effect of storage temperature on detachment and denaturation of glucose oxidase (GOx) biocatalyst has been proved. The carbon nanotubes (CNTs) coated with polyethyleneimine (PEI) as entrapping polymer to attract more GOx to form a durable and layered CNT/PEI/GOx structure is used for long-term storage to minimize GOx detachment from the structure and minimize the possibility of enzyme and protein denaturation. After 120 days, the glucose response of the CNT/PEI/GOx biosensor stored under 4°C is preserved up to 66.7% of its initial value, while under a 25 °C storage the response is maintained up to 41.7%. The enzyme coverage activity of CNT/PEI/GOx stored at 4 °C and 25 °C has decreased by 31.1% and 51.4%, respectively. Denaturation and detachment of GOx are the common causes of thermal degradation in biosensors under improper storage temperatures, but the presence of PEI in the structure can slow-down these phenomena. Moreover, the electrons transfer constant of CNT/PEI/GOx biocatalyst stored at 4 °C and 25 °C were 7.5 ± 0.5 s−1 and 6.6 ± 0.3 s−1, respectively, indicating that also electrons mobility is damaged by detachment and denaturation of enzyme protein and the detection of glucose from the glucose oxidation reaction (GOR) is compromised.

Wearable biofuel cells based on the classification of enzyme for high power outputs and lifetimes

Wearable enzymatic biofuel cells would be the most prospective fuel cells for wearable devices because of their low cost, compactness and flexibility. As the high specificity and catalytic properties of enzymes, enzymatic biofuel cells (EBFCs) catalyze the fuel associated with the redox reaction and get electrical energy. Available biofuels such as glucose, lactate and pyruvate can be harvested from biofluids of sweat, tears and blood, which afford cells a favorable use in implantable and wearable devices. However, the development of wearable enzymatic biofuel cells requires significant improvements on the power density and enzymes lifetime. In this paper, some new advances in improving the performance of wearable enzymatic biofuel cells are reviewed based on the bioanode and biocathode by classifying single-enzyme and multi-enzyme catalysis system. Thereinto, the bioanode usually contains oxidases and dehydrogenases as catalyst, and the biocathode utilizes the catalysis of multi-copper oxidases (MCOs) in the single system. For further enhancing the power density, efforts to develop multi-enzyme catalysis strategies are discussed in bioanode and biocathode respectively. Moreover, some potential technologies in recent years, such as carbon nanodots, CNT sponges and mixed operational/storage electrode are summarized owing to notable efficiency and the capability of enhancing electron transfer on the electrode. Finally, major challenges and future prospects are discussed for the high power output, stable and practical wearable enzymatic biofuel cells.