Biomaterials 19 (1998) 2075 — 2082 In vivo and in vitro responses to poly(ethylene terephthalate-co- diethylene glycol terephthalate) and polyethylene oxide blends Ivonete O. Barcellos, Sonia G. Carobrez, Alfredo T.N. Pires, Marcio Alvarez-Silva*  Departamento de Quimica, Universidade Federal de Santa Catarina, Brazil  Departamento de MIP, Division of Imunologia, Universidade Federal de Santa Catarina, 880 040-900 Trindade SC, Brazil  Departamento de Quimica, Universidade Regional de Blumenau Received 8 July 1997; accepted 22 April 1998 Abstract Although biocompatible polymeric compounds are generally nontoxic, nonimmunogenic, and chemically inert, implants made from these materials may trigger acute and chronic inflammatory responses. These inflammatory reactions may induce degeneration of implanted biopolymer. Interactions between implanted biomaterial and inflammatory cells are mediated by many cellular events involving cellular adhesion and activation. We studied the inflammatory responses in vivo and in vitro to samples of biopolymers composed of poly(ethylene terephthalate-co-diethylene glycol terephthalate) plus 0, 5, 25% of polyethylene oxide. We observed that these biopolymers did not induce inflammatory responses when implanted in the peritoneal cavity of mice for 28 days. However we observed deposition of hyaluronic acid at the surface of implanted biomaterial, suggesting that tolerance to biomaterial occurred after surgical implantation. No significant adhesion of inflammatory cells such as mononuclear phagocytes and peripheral leukocytes were observed in vitro, when poly(ethylene terephthalate-co-diethylene glycol terephthalate) blends were used as substratum to cellular adhesion. These results suggest that blends composed of poly(ethylene terephthalate-co-diethylene glycol terephthalate) induce low inflammatory cell adhesion, since no rejection of biopolymer was observed when implanted in experimental animal models.  1998 Published by Elsevier Science Ltd. All rights reserved Keywords: Biopolymer; Blends; PET-co-DEGT; PEO; Implants; Inflammation 1. Introduction In the last few decades many polymer blends have been investigated. In order to perform a better definition about mixing of polymers, the concept of compatible polymer pairs has been introduced [1—3]. Polymer blends based on engineering polyesters are an important route for the development of new polymeric materials, with excellent performance. The practical importance has been demonstrated in recent years by the intensive re- search carried out on the subject [4, 6] as well as the utilization of different biopolymers for clinical and surgi- cal applications [7]. Poly(ethylene terephthalate) (PET) is an extensively used thermoplastic because of a combination of unique physical, mechanical, permanent properties and proces- sability, as well as biocompatibility [8]. Implanted PET *Corresponding author. Fax: 0055 48 331 9258. biomaterials frequently trigger inflammatory responses in animal models [9]. The inflammatory responses often result in accumulation of phagocytic cells, such as macro- phages on adjacent implant surface. These inflammatory responses may turn to chronic inflammatory lesions that result in rejection of implants, with degradation of bio- polymer [9]. The acute inflammatory events to these implants can be seen as rejection reactions to bio- polymers. Mobilization and adhesion of peripheral mononuclear phagocytes and accumulation of inflam- matory cells to induce granulomatous reactions [10] often trigger these acute reactions. Several groups have attempted to create a biocompatible or a non-cell-adhe- sive surface using polyethylene glycol (PEG) or polyethy- lene oxide (PEO) as a surface modifier [7, 8]. PEO has been shown to have protein-repelling activity when im- mobilized on a surface due to its hydrophilicity, chain mobility and lack of ionic charge [11]. Since most cellular interactions are protein-mediated, a reduction in protein adsorption would serve to prevent cellular 0142-9612/98/$—See front matter  1998 Published by Elsevier Science Ltd. All rights reserved. PII S0142-9612(98)00119-7