Biomaterials 23 (2002) 3149–3158 Acrylic acid grafting and collagen immobilization on poly(ethylene terephthalate) surfaces for adherence and growth of human bladder smooth muscle cells Isabelle Bisson a , Marek Kosinski b , Sylvie Ruault a , Bhuvanesh Gupta c ,J . ons Hilborn c , Florian Wurm d , Peter Frey a, * a Laboratory for Experimental Pediatric Urology, Centre Hospitalier Universitaire Vaudois, Department of Pediatric Surgery, 1011 Lausanne, Switzerland b University Institut of Applied Radiophysics, Lausanne, Switzerland c The ( Angstr . om Laboratory, Polymer Chemistry, University of Uppsala, Sweden d Laboratory of Cellular Biotechnology, Ecole Polytechnique F ! ed ! erale, Lausanne, Switzerland Received 19 September 2001; accepted 8 February 2002 Abstract In tissue engineering, degradable or non-degradable polymer matrices can act as cell-carrier-scaffolds. Cell adhesion and growth on these scaffolds can be promoted by immobilizing extracellular matrix proteins. Therefore, in this study, polymer poly(ethylene terephthalate) (PET) films were surface modified by graft polymerization of acrylic acid, to subsequently allow collagen (types I and III) immobilization and human smooth muscle cell expansion. The surfaces of PET were activated by plasma, followed by acrylic acid graft polymerization, resulting in covalently bound brushes, containing an average of either 0.2270.1 or 5.9370.87 mg/cm 2 of poly(acrylic acid) (PAA). Subsequent electrostatic adsorption of collagen gave a surface concentration of 4.96 and 17.2 mg/cm 2 , respectively, as determined using radiolabelled 125 I collagen. Both PET films grafted with 0.22 mg/cm 2 of PAA with or without adsorbed collagen were apt for smooth muscle cell adhesion and proliferation. However, films grafted with 5.93 mg/cm 2 were not. PAA-grafted PET films, onto which serum proteins of the culture medium adsorbed spontaneously, proved to be better matrices than films on which collagen has been immobilized. It, therefore, can be speculated that other serum proteins are more important than collagen for the human smooth muscle cell adhesion and growth on surface-modified polymer matrices. r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Poly(ethylene terephthalate); Plasma graft polymerization; Acrylic acid grafting; Collagen immobilization; Adherence and growth of human smooth muscle cells; Tissue engineering 1. Introduction In response to congenital or acquired urinary tract disorders, such as bladder extrophy, epispadias, chronic interstitial cystistis, bladder cancer, congenital or trau- matic neurogenic bladder, surgical procedures may often become necessary (e.g. bladder augmentation) to add missing, or to replace diseased tissues. Due to a lack of native urological tissue, traditionally intestinal or gastric segments are used for these operative procedures. However, a variety of complications, such as metabolic disorders, infection, mucous and calculi formation or even malignancy have been associated with these non- urological tissues [1,2]. Naturally derived polymers (collagen, gelatin sponges) and non-degradable syn- thetic materials (Teflon s , silicon) have also been utilized to replace urinary tissues. These materials have failed due to mechanical, structural or biocompatibility reasons [3]. Native urinary tissue is composed of stratified epithelium (urothelium), extracellular matrix and smooth muscle. The extracellular matrix contains fibroblasts, small arteries and veins, nerves and extra- cellular matrix proteins such as collagen, laminin or fibronectin [4]. The extracellular matrix acts as a support to sustain mechanical stress during urinary bladder filling and emptying. Moreover, the matrix supports urothelial and smooth muscle cells and it regulates their *Corresponding author. Tel.: 41-21-314-3070; fax: 41-21-314-3031. E-mail addresses: isabisson@hotmail.com (I. Bisson), pfrey@ chuv.hospvd.ch (P. Frey). 0142-9612/02/$-see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII:S0142-9612(02)00061-3