Preparation and antibacterial characteristic of water-insoluble antibacterial material QPEI/SiO2

Polyethyleneimine (PEI) was grafted onto micron-sized silica gel particles via the coupling action of gamma-chloropropyl trimethoxy silane, and grafting particles PEI/SiO(2) was prepared. Then, polymeric reactions of two steps, tertiary amination reaction and quaterisation, were conducted for the grafted PEI. After quaterisation of the grafted polyethyleneimine, a composite particle, QPEI/SiO(2), was obtained. QPEI/SiO(2) is a water-insoluble antibacterial material. In this work, the antibacterial characteristic of QPEI/SiO(2) was mainly investigated using Escherichia coli (E. coli) as a disease-leading bacterium and adopting a colony count method. The effects of quaterisation degree of PEI and pH of the medium on the antibacterial ability of QPEI/SiO(2) were examined. The antibacterial mechanism of QPEI/SiO(2) was explored profoundly by using two enzyme activity determination methods, beta-D-galactosidase activity determination and TTC-dehydrogenase activity determination. The experimental results indicates that the water-insoluble antibacterial material QPEI/SiO(2) possesses strong antibacterial ability, for the bacterial suspension with a concentration of 10(9) CFU/ml, the antibacterial ratio of QPEI/SiO(2) can reach about 100% only with a dosage of 15 g/l and only for a contact time of 10 min. The main factors influencing the antibacterial ratio of QPEI/SiO(2) are the quaterisation degree of the grafted PEI and pH value of the medium. QPEI/SiO(2) with higher quaterisation degree has stronger antibacterial ability. In a certain range of pH value, the higher the pH value of the medium is, the stronger the antibacterial ability of QPEI/SiO(2 )is. Enzyme activity determination results show that the antibacterial mechanism of the water-insoluble antibacterial material QPEI/SiO(2) is based on a sterilization process and not only is a bacteriostasis action.