The surface properties of poly(vinyl pyrrolidone) (PVP) films and PVP films containing 1, 3 and 5% of collagen before and after UV irradiation (lambda = 254 nm) were investigated using atomic force microscopy (AFM) and monitored by contact angle measurements. Measurements of the contact angle for diiodomethane (D) and glycerol (G) on PVP films were made before and after UV irradiation of the films. AFM images show the fibrils formation in PVP films containing collagen. The amount of collagen in PVP matrix has an important effect on the structure and size of collagen fibril formed. The size of collagen fibrils in irradiated PVP films is bigger than in non irradiated ones. The values of polar and dispersive components of surface free energy show that PVP films are more polar when collagen was added. (C) 2008 Elsevier B. V. All rights reserved.