Chitosan immobilization on polyacrylic acid grafted polypropylene monofilament

Polypropylene (PP) suture was prepared by plasma-induced graft polymerization of acrylic acid onto polypropylene monofilament. The monofilament was treated with oxygen plasma to create hydroperoxide groups and subsequent graft polymerization was initiated on this exposed monofilament. The grafted filament was immobilized with chitosan (CS) using N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) as the linking agent between amino and carboxyl groups. The chitosan content increased with the increase in the degree of grafting on the filament. However, a fraction of the carboxyl groups remained as free functional groups. The pH of the medium has significant influence over the CS immobilization. The transition in immobilization was observed at 4–4.6 pH. The characterization of the immobilized surface by attenuated total reflectance (ATR), contact angle, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). ATR showed that the CS is bonded to the filament surface. The contact angles of the surfaces are significantly enhanced and are the indicative of the enhanced hydrophobicity as compared to the grafted surfaces. XPS showed an increasing trend in the nitrogen content with the increasing graft levels on the filaments. The SEM/AFM revealed that the surface morphology undergoes a gradual change with the increase in the degree of grafting.