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

Abstract

Porous PEGT/PBT implants with different physico-chemical characteristics were evaluated to identify its potential as biodegradable and biofunctional soft tissue filler. Implants (50 Â 10 Â 5mm3 ) were implanted subcutaneously in mini-pigs and tissue response, tissue volume generated and its consistency were assessed quantitatively with a 52 weeks follow-up. The absence of wound edema, skin irritation, and chronic inflammation demonstrated biocompatibility of all implants evaluated. The hydrophobic implants induced the mildest foreign body response, generated highest amount of connective tissue and demonstrated a decrease in copolymer MW of 34-37% compared to 90% decrease of the hydrophilic implants. The rate and extent of copolymer fragmentation seems to be the determining factor of success of soft tissue augmentation using porous PEGT/PBT copolymer implants.

Cell-based tissue engineering strategies used in the clinical repair of articular cartilage

“…PEOT/PBT 2D films with a higher PEOT mass ratio were found to support a rounded chondrocyte morphology, no proliferation, and higher collagen II:collagen I gene expression; films with a higher PBT mass ratio supported a flat cell morphology, cell adhesion, and proliferation (121, 122). Similarly, chondrocytes cultured in 3D scaffolds with the composition 1000PEG-70:30 (PEG molecular weight = 1000 g/mol; 70% PEOT and 30% PBT by mass) secreted more sulfated glycosaminoglycans (GAGs) than those in 300PEG-55:45 scaffolds after 4 weeks of in vitro culture (117).…”

“…In vitro hydrolysis experiments show more rapid degradation of scaffolds with a higher PEOT content (125). When implanted subcutaneously in mini-pigs for 52 weeks, 300PEG-55:45 scaffolds remained largely intact, while 2000PEG-80:20 scaffolds largely fragmented to < 1 μm particles (122). Molecular weight of polymer chains decreased 34% and 90%, respectively.…”

“…However, the scaffold resorption time of 12 months, as stated on the company website, is much slower than that of Bioseed ® -C. In vitro hydrolysis experiments show more rapid degradation of scaffolds with a higher PEOT content (125). When implanted subcutaneously in mini-pigs for 52 weeks, 300PEG-55:45 scaffolds remained largely intact, while 2000PEG-80:20 scaffolds largely fragmented to < 1 μm particles (122). After 3 months in a rabbit osteochondral or mouse subcutaneous model, 300PEG-55:45 and 1000PEG-70:30 scaffolds seemed to exhibit minimal degradation (117, 123).…”

Adipose tissue engineering: state of the art, recent advances and innovative approaches

“…Microspheres [49,50] Porous scaffold [81] Hydrogels [82] In vitro: release kinetics of insulin and IGF1 [50] In vivo: direct implantation into the deep muscular fascia of the abdominal wall of Sprague Dawley female rats [49,50] In vivo: subcutaneous implantation in mini-pigs up to 52 weeks …”

“…Results indicated that the more hydrophobic implants, compared with the more hydrophilic ones, induced the mildest foreign body response, generated the highest amount of connective tissue and demonstrated a lower decrease in the molecular weights. Despite the promising results, satisfactory biofunctionality was not obtained with any implants used and the consistency of the newly formed tissue was undesirable, being much stiffer than the surrounding adipose tissue [81].…”