Biocompatibility of a polyether urethane, polypropylene oxide, and a polyether polyester copolymer. A qualitative and quantitative study of three alloplastic tympanic membrane materials in the rat middle ear

Abstract

The biocompatibility of porous implants made of Estane 5714 F1 polyether urethane, polypropylene oxide, and a poly(ethylene oxide hydantoin) and poly(tetramethylene terephthalate) segmented polyether polyester copolymer (HPOE/PBT copolymer), which were selected as candidates for an alloplastic tympanic membrane, was assessed after implantation in rat middle ears for periods of up to 1 year. Implantation of the materials led to tissue reactions initially associated with the wound-healing process, whereas after 1 month not only the presence of macrophages and foreign-body giant cells surrounding the implant materials but also implant degradation were characteristic for a foreign-body reaction. Macrophages and foreign-body giant cells dominated the picture of the tissue surrounding polypropylene oxide. The altered morphology of these cells, the persistent infiltration of the implantation sites by exudate cells, and the premature death of five rats in the 1-year group suggest that polypropylene oxide degradation was accompanied by the release of toxic substances. Estane and copolymer degradation did not induce tissue responses reflecting implant toxicity, and tympanic membranes given these alloplasts showed a normal healing pattern. Inclusions in the cytoplasm of macrophages associated with degradation and phagocytosis of all of the polymers under study were found to contain iron, silicon, titanium, and aluminum. Growth of fibrous tissue and bone, the latter into Estane and HPOE/PBT copolymer implants, indicated appropriate implant fixation by tissue, although macrophages and foreign-body giant cells were present as well. Especially the fixation of copolymer by ingrowth of bone seems promising in terms of the amount of bone in the pores and the electron-dense bone/copolymer interface. The latter is indicative for bonding osteogenesis. The HPOE/PBT copolymer is a better candidate for alloplastic tympanic membrane than Estane, and the use of polypropylene oxide cannot be recommended.

Stem cell technology and bioceramics: From cell to gene engineering

“…37 Since their discovery, many bioactive ceramics have been used for bone reconstruction surgery in clinical situations and have been reported to show excellent results. In addition, some nonceramic materials such as calcium carbonate crystals (aragonite and calcite) [38][39][40][41] and organic polymers [42][43][44][45] have been reported to show bone-bonding characteristics. Bone is formed by cells called osteoblasts, which arise from progenitor cells in a multistep lineage cascade.…”

Long-term Evaluation of Porous PEGT/PBT Implants for Soft Tissue Augmentation

“…PEGT/PBT copolymer degradation has been analyzed in other studies and proceeds mainly via mechanisms of hydrolysis, oxidation, and phagocytosis [15,[28][29][30]44,45]. Deschamps et al [45] showed not only that during accelerated hydrolysis of the copolymer a decrease in copolymer MW is mainly caused via scission of the ester bonds connecting the PEG and terephthalate, but that cleavage in the PBT hard segment also occurred.…”

“…By variation in the weight percentage and/or length of the soft and hydrophilic PEGT segment, copolymers can be prepared differing in hydrophilicity, pliability, mechanical integrity, degradation rate, and cell-adhesion affinity. Furthermore, the PEGT/PBT copolymer has already been introduced to the clinic as a degradable scaffold for the repair of tympanic membranes [14,15] more than 15 years ago. More recently the FDA approved it as a cement restrictor in orthopedics [16,17].…”

“…In the field of soft tissue regeneration, several polymer compositions have been shown in vitro to support adhesion and growth of skin cells and in vivo ingrowth of vessels and connective tissue [18][19][20][21][22][23][24]. These developments are supported by several in vitro and in vivo studies which showed that PEGT/PBT copolymers are biocompatible, well-tolerated, and do not cause adverse tissue reactions or systemic site effects [15,21,[25][26][27][28][29][30].…”

Bilayered biodegradable poly(ethylene glycol)/poly(butylene terephthalate) copolymer (Polyactive?) as substrate for human fibroblasts and keratinocytes

“…1 Various studies have been performed to assess the biocompatibility of these degradable PEGT/PBT copolymers upon implantation in soft and hard tissue. [2][3][4][5][6][7][8] It was concluded that PEGT/PBT copolymers did not induce any adverse affect on the surrounding tissue and thus showed satisfactory biocompatibility. Clinical studies have been performed using PEGT/PBT copolymers as an artificial tympanic membrane, 9,10 ventilation tubes, an adhesion barrier, 11 a cement restrictor, bone fillers, [12][13][14] elastic bioactive coatings on load-bearing dental and hip implants, [15][16][17] and also for wound healing purposes.…”