Xiaojuan Wang

In this study, UiO-66-NH ₂ metal–organic framework (MOF) nanoparticles with peroxidase and oxidase mimetic activities were incorporated into a chitosan (CS) matrix by a simple and environmentally friendly method.

A series of poly (amino acid) with zwitterionic character was prepared for surface coating to avoid protein adsorption, by modifying the poly (aspartic acid) side chain with tertiary amine groups. An interesting and facile procedure is described with starts with polysuccinic acid which is followed by ring-opening with amino functions and finally hydrolysis of the remaining succinic acid groups achieving the polyaspartic acid structure as backbone. The degree of cationic tertiary amino group was easily varied by the degree of ring-opening with amines. The materials show isoelectric point between pH 4 and 9, have a typical zwitterionic character, and can be used to coat negatively as well as positively charged surfaces, depending on composition. The protein adsorption behavior is thus pH dependent and was studied with various proteins mainly available in blood. The adsorption test proved that a significant reduction of protein adsorption could be found for fibrinogen and albumin, and this protein-repellent behavior is strongly dependent on the amount of the absorbed polymer (adsorbed at pH = 7.4). This is a nice additional contribution to polymers with zwitterionic character used as coating reducing nonspecific protein adsorption.

Fe₃O₄ nanoparticles, used as peroxidase mimetics, exhibit splendid future in the biomedical field. However, the functionalization on Fe₃O₄ nanoparticles always goes with the loss of superparamagnetism and decrease in peroxidase-activity. Here, we synthesized green polyethylene glycol (PEG)-functionalized magnetic/N-trimethyl chitosan (CS) hybrid nanoparticles (Fe₃O₄@PAA/TMC/PEG NPs) with improved water dispersibility, superparamagnetism, high saturation magnetization and well peroxidase-like activity. The functionalized coating was divided in two steps, one involved a cross-linked PEG/PAA/CS middle layer to protect the nanocrystal Fe₃O₄ from oxidization, the other was a hydrophilic PEG/TMC outer layer improving the water dispersion, biocompatibility, as well as supplying positive quaternary ammonium groups for a potential increase of cell binding efficiency. The structure, composition and morphology of Fe₃O₄@PAA/TMC/PEG NPs were characterized by TEM, FT-IR spectroscopy, DLS, zeta potential measurement, respectively. Thermal performance was characterized by TGA, and the peroxidase-like mimics activity was tested by TMB·2HCl colour development experiments. The magnetic property of the as-prepared hybrid nanoparticles was first confirmed by VSM, and then proved by the bacterial pathogens adsorption, especially at ultralow pathogen concentration. Particularly, with an external magnet, the Fe₃O₄@PAA/TMC/PEG NPs, combined cationic quaternary ammonium groups and peroxidise-mimetic catalytic activity, were tested for antibacterial effect by plating method.