BACKGROUND: On the basis of effective bioaffinity adsorption of Ag+, silver nanoparticles (Ag NPs) were synthesized on the surface of chitosan-TiO2 adsorbent (CTA) by TiO2 photocatalysis for crystal growth. RESULTS: Among the microstructure characterizations of the resulting silver nanoparticles-loaded chitosan-TiO2 adsorbent (Ag-CTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX) revealed the formation of metallic Ag on the CTA, which was further confirmed by the surface plasmon resonance of Ag NPs in the UV-visible absorption spectrum. The underlying mechanism behind the formation of Ag NPs on the CTA by TiO2 photoreduction was studied by Fourier transform infrared (FTIR) spectroscopy. The distinctive feature of Ag-CTA after adsorption was the highly efficient antimicrobial activity in inactivating different test strains. In the case of Escherichia coli, 1.50 mg 1.67 wt% Ag-CTA could totally inhibit 1.0-1.2 x 10(7) colony forming units (CFU) in 100 mL nutrient medium, which was superior to that previously reported. CONCLUSIONS: CTA effectively adsorbed the precious metal ion Ag+ onto active imprinting sites on the adsorbent and then exerted efficient antimicrobial effects against diverse microbes. This research will be useful for designing a novel CTA-based wastewater treatment formulti-functional performance. (C) 2010 Society of Chemical Industry