Biomaterials 26 (2005) 3495–3502 Chemical modification of poly(vinyl chloride) resin using poly(ethylene glycol) to improve blood compatibility Biji Balakrishnan a , D.S. Kumar b , Yasuhiko Yoshida b , A. Jayakrishnan a,Ã a Polymer Chemistry Division, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Satelmond Palace Campus, Poojapura, Trivandrum 695 012 Kerala, India b Department of Applied Chemistry, Bio-Nano Electronics Research Centre, Toyo University, Kawagoe, Saitama 350-8585, Japan Received 15 April 2004; accepted 20 September 2004 Abstract Poly(vinyl chloride) (PVC) was aminated by treating the resin with a concentrated aqueous solution of ethylenediamine. The aminated PVC was then reacted with hexamethylene diisocyanate to incorporate the isocyanate group onto the polymer backbone. The isocyanated PVC was further reacted with poly(ethylene glycol) (PEG) of molecular weight 600 Da. The modified polymer was characterized using infrared and X-ray photoelectron spectroscopy (XPS) and thermal analysis. Infrared and XPS spectra showed the incorporation of PEG onto PVC. The thermal stability of the modified polymer was found to be lowered by the incorporation of PEG. Contact angle measurements on the surface of polymer films cast from a tetrahydrofuran solution of the polymer demonstrated that the modified polymer gave rise to a significantly hydrophilic surface compared to unmodified PVC. The solid/ water interfacial free energy of the modified surface was 3.9 ergs/cm 2 as opposed to 18.4 ergs/cm 2 for bare PVC surface. Static platelet adhesion studies using platelet-rich plasma showed significantly reduced platelet adhesion on the surface of the modified polymer compared to control PVC. The surface hydrophilicity of the films was remarkably retained even in the presence of up to 30 wt% concentration of the plasticizer di-(2-ethylhexyl phthalate). The study showed that bulk modification of PVC with PEG using appropriate chemistry can give rise to a polymer that possesses the anti-fouling property of PEG and such bulk modifications are less cumbersome compared to surface modifications on the finished product to impart anti-fouling properties to the PVC surface. r 2004 Elsevier Ltd. All rights reserved. Keywords: Polyvinyl chloride; Polyethylene oxide; Surface modification; Surface energy; Platelet adhesion; Biocompatibility 1. Introduction Poly(vinyl chloride) (PVC) finds extensive application in the medical field [1]. Bags for the storage of blood and its components, tubings for extracorporeal circulation and endotracheal intubation and intravenous catheters are some of the medical devices wherein plasticized PVC is employed. PVC is not a blood-compatible polymer per se and additives such as plasticizers added to the polymer during processing to impart flexible character to an otherwise rigid PVC also contribute to many adverse effects when used in contact with tissue or blood [2]. Many attempts to improve the biocompatibility of PVC have been reported in the literature. This includes polymer surface modification with endpoint attachment of heparin [3,4], immobilization of albumin [5], amina- tion of PVC followed by complexation with heparin [6,7], grafting hydrophilic polymers onto PVC surface [8] and plasma modification [9]. In a recent study, it was shown that grafting poly(ethylene glycol) (PEG) onto PVC surface by the well-known Williamson reaction, taking advantage of the labile nature of chlorine atoms on PVC, can generate a protein and platelet repelling surface [10]. ARTICLE IN PRESS www.elsevier.com/locate/biomaterials 0142-9612/$-see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.biomaterials.2004.09.032 Ã Corresponding author. Fax: +914712341814. E-mail address: dr_jkrishnan@sify.com (A. Jayakrishnan).