In this study, we developed composite chitosan beads combining various metal ions, including Ni2+, Cu2+, Zn2+, and Fe2+, for direct adsorption of enterovirus 71 (EV71). The metal-ion species had significant effects on the adsorption capacity of beads. Among these metal ion-composite chitosan beads, Ni2+-chitosan beads exhibited the best adsorption capacity of EV71. Using a concentration of 0.01-M Ni2+ was found to best provide for bead formation and EV71 adsorption. The adsorption of EV71 for Ni2+-chitosan beads at neutral or alkaline pH was favored. Under a competitive condition with albumin proteins, Ni2+-chitosan beads exhibited significant capacity of EV71 adsorption in culture media. The adsorption of EV71 on the Ni2+-chitosan beads was attributed to the strong binding between Ni2+ ions chelated to the surface amino acid of EV71 capsids and Ni2+ ions chelated on the chitosan materials. Moreover, the adsorbed EV71 retained its antigenicity and infectivity after desorption. The Ni2+-chitosan beads exhibit a promising application to EV71 adsorption and removal. (c) 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2012