A free-standing,
antibacterial hydrogel was fabricated using silver-nanoparticle-immobilized
cellulose nanofibers (CNFs) and alginate. Surface hydroxyl groups
of CNFs were oxidized to carboxylate groups using (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl
(TCNF), followed by the treatment with silver nitrate solution for
surface adsorption of silver ions. In situ reduction of silver ions
to produce silver nanoparticles was performed for the silver-adsorbed
CNFs. Electron microscopy, X-ray diffraction, and spectroscopic analysis
revealed that higher amounts of silver nanoparticles were immobilized
on the surface of TCNF than on the surface of native CNF. Silver-nanoparticle-immobilized
TCNF was embedded in alginate gels and silver ions from the matrix
were slowly released for 7 days. Silver-nanoparticle-loaded alginate
gels showed comparable antibacterial activity to silver-ions-loaded
alginate gels, although the former showed a significantly lower cytotoxicity
against animal cells. Thus, the antibacterial gels can potentially
be applied to various skin surfaces to prevent bacterial infection
while minimizing skin damage.