Biomodification of thermosensitive copolymer of ethylene glycol vinyl ether by RGD and insulin Menems ßeG€ um€ us ßderelio glu * , Oks ßen M€ uft € uo glu, Ays ßeG€ onen Karakec ßili Department of Chemical Engineering and Bioengineering, Hacettepe University, Beytepe, Ankara 06532, Turkey Received 1 August 2003; received in revised form 1 November 2003; accepted 30 November 2003 Abstract The radiation copolymerization of hydrophilic vinyl ether monomer, ethylene glycol vinyl ether (EGVE), and hy- drophobic comonomer butyl vinyl ether (BVE) was realized in the presence of crosslinking agent diethylene glycol divinyl ether. The results of swelling experiments indicated that the hydrogel which has 60:40 comonomer ratio (mole percentage of EGVE:BVE in monomeric mixture) is temperature-sensitive at 4–37 °C temperature range. While the hydrogel shows fully hydrated form at low temperature (+4 °C), it extensively dehydrates at 37 °C. This thermosensitive gel was modified by immobilizing RGD (Arg–Gly–Asp) sequence of cell adhesion factor, fibronectin, or cell-growth factor, insulin, to the copolymer for its possible use in mammalian cell cultures. The effectiveness of immobilization process was checked with SEM, FTIR spectroscopy and swelling studies. However, after biomodification the effect of the temperature change on the EWC value of hydrogel is less marked for both gels modified by RGD and insulin. Ó 2003 Elsevier B.V. All rights reserved. Keywords: Biomaterials; Biomodification; Stimuli-sensitive polymers; Poly(vinyl ethers); Hydrogel 1. Introduction Polymeric hydrogels are unique materials, which absorb and retain large amounts of water. The presence of crosslinks between the polymer chains makes them insoluble, soft and elastic. Much attention has currently been devoted to the stimuli-responsive hydrogels which display phase transitions in response to small environmental changes like temperature, pH, solvent composi- tion, electric field and light [1,2]. Among them temperature-sensitive hydrogels have potential applications in gel-based separation processes and in biomedical area, e.g., preparation of drug de- livery systems, separation of cells, manufacturing of some artificial organs, etc. [3,4]. The thermo-sensitive character of poly(N -iso- propyl acrylamide) (NIPAAm) and poly(vinyl me- thyl ether) hydrogels which shrink or swell below or above LCST has widely been investigated [5–7]. Recently, Mun et al. [8] synthesized linear and crosslinked copolymers of a vinyl ether of ethylene glycol (2-hydroxyethyl vinyl ether) (EGVE) and butyl vinyl ether (BVE) by c-irradiation polymeri- zation to produce a gel with any desired temperature Reactive & Functional Polymers 58 (2004) 149–156 www.elsevier.com/locate/react REACTIVE & FUNCTIONAL POLYMERS * Corresponding author. Tel.: +90-312-2977-447; fax: 90-312- 2992-124. E-mail address: menemse@hacettepe.edu.tr (M. G€ um€ us ßder- elio glu). 1381-5148/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.reactfunctpolym.2003.11.016