The antibacterial effect of G3-poly-amidoamine dendrimer on gram negative and gram positive bacteria in aqueous solutions

Dendrimers are symmetric, round and ramose macromolecules made up of monomers which have a certain structural order. The aim of this study was to evaluate the antibacterial effects of different concentrations of G3-poly-amidoamine dendrimer (G3-PAD) on 7 species of gram-negative and gram-positive bacteria in aqueous solutions. Different concentrations of G3-PAD were prepared and from each bacterial species, a suspension with a different pH was prepared according to the McFarland 0.5 standard. Bacteria were left in a 37 degrees C incubator and shaker from 0 to 60 min, and were cultivated on a Mueller-Hinton Agar plate. The bacteria that grew on each plate were counted and analyzed. The results showed that the antibacterial effect of G3-PAD in aqueous solutions was directly related to dendrimer concentration, contact time and pH. The strongest effect on Salmonella and Bacillus Subtilis was at pH = 6.5 and 7.5 and contact time 45 min, and in pH = 9, contact time 30 min; for Enterococcus faecalis in all three pH, it was 60 min; for Staphylococcus Aureus in pH = 6.5 and 7.5, 60 min and in pH = 9, 30 min; for E. coli in pH = 6.5 and 7.5, 60 min and in pH = 9, 45 min. G3-PAD showed its strongest effect on Shigella bacteria in pH = 6.5, contact time 60 min. In pH = 7.5 there was no optimum condition and in pH = 9, the optimum contact time was 60 min. The strongest effect of G3-PAD on all species was seen in 2000 ppm concentration. These results show a new strategy to improve bacteria elimination from aqueous solutions. However, safely using dendrimers for disinfecting drinking water still needs more research.