Hybrid alginate beads with thermal-responsive gates for smart drug delivery

Polysaccharide-based thermo-responsive material was prepared by grafting PNIPAAm onto hybrid alginate beads, in which a biomineralized polyelectrolyte layer was constructed aiming to enhance the mechanical strength and ensure higher graft efficiency. XPS results demonstrated that the incorporation of PNIPAAm to the hybrid beads was successful, and the PNIPAAm-grafted beads were more hydrophilic than the ungrafted ones as indicated by their swelling behavior. The drug release behaviors revealed that the grafted beads were both thermo- and pH-sensitive, and the PNIPAAm existed in the pores of the alginate beads acted as the on-off'' gates: the pores of the beads were covered by the stretched PNIPAAm to delay the drug release at 25 degrees C and opened to accelerate the drug release at 37 degrees C because of the shrinking of PNIPAAm molecules. This paper would be a useful example of grafting thermo-responsive polymers onto biodegradable natural polymer substrate. The obtained beads provide a new mode of behavior for thermo-responsive smart'' polysaccharide materials, which is highly attractive for targeting drug delivery system and chemical separation. Copyright (C) 2010 John Wiley & Sons, Ltd.