ADSORPTION OF DNA ONTO POLYPYRROLE-SILICA NANOCOMPOSITES

DNA adsorption onto polypyrrole (PPy) powder, a colloidal silica sol, and three polypyrrole-silica nanocomposite particles (untreated and am ine-or carboxylic acid-functionalized) was investigated at neutral pH using sodium phosphate buffer, The extent of DNA adsorption was found to be 32 and 22 mg/g for the aminated silica sol and aminated PPy-sili ca particles respectively, and 6.5 mg/g for the carboxylated particles . DNA adsorption onto the unfunctionalized PPy-silica particles occurs to a lesser extent, whereas no adsorption was detected for the colloi dal silica sol, Our results suggest that DNA adsorption is mainly gove rned by electrostatic and hydrophobic interactions, DNA is adsorbed on to polypyrrole chloride bulk powder and also onto the aminated PPy-sil ica particles, which both have cationic binding sites, The silica sol and the unfunctionalized PPy-silica particles both possess a net negat ive surface charge at this pH, which probably accounts for the zero or very low adsorbed amounts of DNA on these substrates. DNA adsorption onto the carboxylated PPy-silica particles may be enhanced by hydrogen bonding relative to the unfunctionalized polypyrrole-silica particles . (C) 1997 Academic Press.