Hyperbranched poly(amidoamine) as the stabilizer and reductant to prepare colloid silver nanoparticles in situ and their antibacterial activity

This study provided a facile and green method to prepare stable colloid silver nanoparticles in aqueous solution by utilizing the amine-terminated hyperbranched poly(amidoamine) (HPAMAM-NH2) as both stabilizer and reductant. The formation of silver nanoparticles was verified by FTIR, UV-vis, TEM, EDS, and XRD measurements. Monodispersed colloid silver nanoparticles with small particle sizes were obtained, and the average particle size could be effectively controlled from ca. 15 to 4 nm by simply adjusting the molar ratio of N/Ag in feed. The antibacterial activity of the HPAMAM-NH2/Ag nanocomposites was also investigated against Gram-positive and Gram-negative bacteria. They were able to efficiently inhibit the growth and multiplication of several bacteria, including Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Klebsiella mobilis, and the bacterial inhibition ratio reached up to 95% at a low silver concentration of 2.7 mu g/mL.