Search

Dehydrogenases (DHs) are widely explored bioelectrocatalysts in the development of enzymatic bioelectronics like biosensors and biofuel cells. However, the relatively low intrinsic reaction rates of DHs which mostly depend on diffusional coenzymes (e.g., NAD+) have limited their bioelectrocatalytic performance in applications such as biosensors with a high sensitivity. In this study, we find that rare-earth elements (REEs) can enhance the activity of NAD+-dependent glutamate dehydrogenase (GDH) toward highly sensitive electrochemical biosensing of glutamate in vivo. Electrochemical studies show that the sensitivity of the GDH-based glutamate biosensor is remarkably enhanced in the presence of REE cations (i.e., Yb3+, La3+ or Eu3+) in solution, of which Yb3+ yields the highest sensitivity increase (ca. 95%). With the potential effect of REE cations on NAD+ electrochemistry being ruled out, homogeneous kinetic assays by steady-state and stopped-flow spectroscopy reveal a two-fold enhancement in the intrinsic reaction rate of GDH by introducing Yb3+, mainly through accelerating the rate-determining NADH releasing step during the catalytic cycle. In-depth structural investigations using small angle X-ray scattering and infrared spectroscopy indicate that Yb3+ induces the backbone compaction of GDH and subtle β-sheet transitions in the active site, which may reduce the energetic barrier to NADH dissociation from the binding pocket as further suggested by molecular dynamics simulation. This study not only unmasks the mechanism of REE-promoted GDH kinetics but also paves a new way to highly sensitive biosensing of glutamate in vivo., This study demonstrated that REEs serve as allosteric promoters for bioelectrocatalysis of glutamate dehydrogenase by triggering subtle reorientation of peptide segments, consequently expediting phase coupling along with the catalytic scheme.

Dual biocidal groups of N-halamine and pyridinium were used to modify surface of magnetic sub-microparticles to exert enhanced synergistic antibacterial capacity. Magnetic silica Fe3O4 sub-microparticles (SMPs) were synthesized and then encapsulated with interpenetrating polymer network (IPN) of polystyrene (PS) and poly(acrylic acid) (PAA). The carboxylic acid groups of PAA were used as surface reactive sites to bond with amino groups of 4-aminopyridine through amidation reaction. N-halamine/pyridinium-derivatized magnetic sub-microparticles were sequentially produced by quaternization of the pyridine to pyridinium with 1-chlorohexane and chlorination of amide N–H to N-halamine with NaClO. The synthetic steps and products were characterized with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray photoelectron spectrocsopy (XPS). The N-halamine/pyridinium-derivatized SMPs with dual biocidal functionalities showed faster deactivation abilities against both Escherichia coli and Staphylococcus aureus compared with their counterparts that contained only N-halamine or pyridinium, and exhibited promising stability toward repeated washing and long-term storage. The designed SMPs in this study offer potential and ideal candidates for sterilization application due to multiple advantages including improved synergistic biocidal ability, high surface area, and easy recyclability.

A novel electrochemical online system for indirect, highly sensitive and selective online monitoring of ATP in the cerebral microdialysate is presented based on the particular reaction of ATP with zeolitic imidazole framework-90 (ZIF-90) encapsulated laccase microcrystals (laccase@ZIF-90) and the natural catalytic activity of laccase.

Antibacterial modification of polymers with potent biocides via an efficient and universal approach is very desirable in both academia and industry. A polysiloxane with both quaternary ammonium and N-chloramine was prepared via a facile three-step synthetic route. Poly(methylhydrosiloxane) (PMHS) was first reacted with 2-(dimethylamino)ethyl acrylate to introduce an ending tertiary amine that was subsequently quaternized with 3-(3-chloropropyl)-5,5-dimethylhydantoin (CPDMH). The 5,5-dimethylhydantoin moiety was then transformed into its N-chloramine counterparts by chlorination with tert-butyl hypochlorite to produce quaternary ammonium (quat)/N-chloramine polysiloxane. The CO2-philic quat/N-chloramine polysiloxane was interpenetrated into polyethylene terephthalate (PET) in supercritical carbon dioxide (scCO2) and formed a 70 nm biocidal layer. The synthetic procedures and interpenetration results were characterized with Fourier transform infrared spectroscopy (FTIR), 1H NMR, scanning electron microscopy...