This work describes the release of copper(II) ions from cellulose fibers, which have been chemically modified by periodate-induced oxidation of cellulose, followed by covalent attachment of biopolymer chitosan. The release of copper(II) ions has been investigated in physiological fluid (PF) and protein solution (PS) both at 37 degrees C. Fibers have demonstrated excellent antibacterial activity against E. coli. Finally, their borohydride-induced reduction has yielded copper nanoparticle-loaded fibers, with average diameter of particles, nearly 28.94 mn. The formation of copper nanoparticles has been established by surface plasmon resonance and FTIR spectroscopy. These fibers also show fair biocidal action against E. coli. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 757-766, 2009