Zhenming Che

Selection and characterization, application of a DNA aptamer targeted to Streptococcus pyogenes in cooked chicken

An aptamer against Streptococcus pyogenes was selected and identified, and a fluorescent method based on the reported aptamer was established to detect S. pyogenes in the cooked chicken. Through a twelve rounds of whole-bacterium SELEX (systematic evolution of ligands by exponential enrichment) selection in vitro, a set of aptamers binding to the whole cell of S. pyogenes were generated, harvesting a low-level dissociation constant (Kd) value of 44 ± 5 nmol L-1 of aptamer S-12. Aptamer-based quantification of S. pyogenes in the cooked chicken sample was implemented in a fluorescence resonance energy transfer-based assay by using graphene oxide, resulting in a limit of detection of 70 cfu mL-1. The selected aptamer showed affinity and selectivity recognizing S. pyogenes; besides, more biosensors based on the selected aptamer as a molecular recognition element could be developed in the innovative determinations of S. pyogenes.

Oxidation of Chlorpromazine by Lipoxygenase Immobilized on Magnetic Fe3O4 Nanoparticles.

In this work, soybean lipoxygenase enzyme was immobilized on the magnetic Fe3O4 nanoparticles to oxidate chlorpromazine (CPZ). The physicochemical properties of the nanoparticles were characterized with transmission electronic microscopy (TEM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA), and the magnetic properties were detected by a vibrating sample magnetometer (VSM). The TEM images indicated the surface and the size of the immobilized enzyme were much rougher and thicker than those of the naked particles. The analyses of XRD patterns showed that the structure of the magnetic nanoparticles had no significant change while the nanoparticles also exhibited higher superparamagnetism at room temperature. Compared to free enzyme or the enzyme immobilized with other methods, the optimal pH, temperature and H2O2 concentration for the activity of immobilized enzyme did not have great changes, but the immobilized enzyme was more stable and less sensitive to the change of the influence factors than free counterpart. The immobilized enzyme could be recovered easily by magnetic separation and could be reused for many times in the process of CPZ oxidation. The results obtained by simulating the model of Michaelis-Menten indicated that the reaction of CPZ oxidation followed Michaelis-Menten kinetics and the enzyme still retained its affinity for CPZ while the enzyme was immobilized.