Dual properties of the deacetylated sites in chitosan for molecular immobilization and biofunctional effects.

Polypropylene nonwoven fabric was surface-activated by high-density oxygen microwave plasma, followed by graft copolymerization with acrylic acid (AAc) and then coupling with chitosan molecules. The pAAc-grafted surface containing C=O in carboxylic acid exhibited a hydrophilic character capable of promoting water absorbency. A larger portion of minimum 85% deacetylated sites in chitosan molecules was then coupled with the grafted pAAc (around 149 microg.cm(-2)) by forming amide bonds at their interface. The covalently bonded chitosan was weighted around 44 microg.cm(-2). The smaller portion of the deacetylated sites demonstrated a distinctive structure as polycations, i.e., NH(3)(+), on the immobilized chitosan. The respective structures following sequential reactions were identified using Fourier transform infrared-attenuated total reflection and X-ray photoelectron spectroscopy with peaks deconvolution. The NH(3)(+) sites on the immobilized chitosan exhibited biofunctional in anticoagulation and in antibacterial property. Blood cells agglutination or agglomeration upon the chitosan-immobilized surface, in particular for red blood cells and platelets, resulted from hydrophilic effect derived from the grafted pAAc and the chitosan itself, and ionic attractions between polycations and blood cells. In addition, the agglutinated cells retained their original morphologies. It is therefore very promising to apply this durable chitosan-immobilized surface for making an antibacterial support, at the same time, for retaining blood cell affinity.