chemical engineering research and design 89 (2011) 328–334 Contents lists available at ScienceDirect Chemical Engineering Research and Design journal homepage: www.elsevier.com/locate/cherd Effect of copolymer ratio on hydrolytic degradation of poly(lactide-co-glycolide) from drug eluting coronary stents Chhaya Engineer a,1 , Jigisha Parikh a,* , Ankur Raval b,2 a Department of Chemical Engineering, Sardar Vallabhbhai National Institute of Technology, Ichchanath, Surat 395007, Gujarat, India b Sahajanand Medical Technologies Pvt. Ltd., Wakhariawadi, Nr. Dabholi Char Rasta, Ved Road, Surat, India abstract The in vitro hydrolytic degradation behavior of poly(d,l-lactide-co-glycolide) (PLGA) has been systematically inves- tigated from the drug eluting coronary stents with respect to different copolymer compositions. The drug–polymer coated stents were incubated in phosphate buffer saline (pH 7.4) at 37 ◦ C and 120 rpm up to 12 months to facili- tate hydrolytic degradation. Gel permeable chromatography, differential scanning calorimetry and scanning electron microscopy were employed to characterize their degradation profiles. The study supports the bulk degradation behav- ior for PLGA from coated stents. Molecular weight of polymer decreased immediately after immersion in PBS but mass loss was not observed during first few days. The rate of hydrolytic degradation was influenced by copolymer ratio, i.e., degradation of 50:50 PLGA was fastest followed by 65:35 PLGA and 75:25 PLGA. The drug release from PLGA coated stent followed biphasic pattern which was governed by surface dissolution and diffusion of drug rather than polymer degradation. © 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Keywords: Poly(d,l-lactide-co-glycolide); Hydrolytic degradation; Restenosis; Drug eluting stent 1. Introduction Coronary stents are a major advance in the treatment of obstructive cardiovascular disease. However, in the substan- tial number of patients, stent placement can trigger restenosis after implantation (Costa et al., 2002). The concept of using drug eluting stents for prolonged, sufficient, and localized drug delivery to address restenosis is an important contem- porary advance in interventional cardiology (Costa et al., 2002; Babapulle and Eisenberg, 2002; Sousa et al., 2003). Polymers play a critical role in local drug delivery from the stent scaffold and to date, attempts to deliver drug with- out polymer have not proven successful (Lansky et al., 2004; Teirstein, 2004; John et al., 2008). The majority of first gen- eration drug eluting coronary stent coatings are based on hydrophobic polymers which retain and release drug in a con- trolled fashion. Biodegradable polymers are often cited as an alternative to biostable polymers for drug eluting stent coat- ∗ Corresponding author. Tel.: +91 261 2201689; fax: +91 261 2201641. E-mail addresses: e.chhaya@ched.svnit.ac.in (C. Engineer), jk parikh@yahoo.co.in, jkp@ched.svnit.ac.in (J. Parikh), ankur.med@sahmed.com (A. Raval). Received 30 March 2010; Received in revised form 28 June 2010; Accepted 29 June 2010 1 Tel.: +91 261 2201689. 2 Tel.: +91 261 2521251; fax: +91 261 2520252. ings (Doyle and Holmes, 2009; Hezi-Yamit et al., 2009). These polymers degrade temporally, leaving behind only a bare metal stent. The family of aliphatic polyesters has been by far the dominating choice for materials in degradable drug delivery systems. The most extensively investigated and advanced polymers in regard to available toxicological and chemical data are the polylactide (PLA) and poly(lactide-co-glycolide) (PLGA) (Lewis, 1990). The popularity of PLA and PLGA is fur- ther explained by the fact that FDA has approved them for the number of clinical applications (Edlund and Albertsson, 2002). However the biocompatibility of these polymers, specifically in a vascular setting, depends to a large extent on degradation kinetics. Moreover, drug elution kinetics from the stent also greatly depends upon polymer degradation. In recent years, a number of parameters have been iden- tified that influence the polymer degradation. Among them are the copolymer composition (Vert et al., 1984), morphol- 0263-8762/$ – see front matter © 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.cherd.2010.06.013