Diminished fibrotic encapsulation and comparable physicochemical properties of poly (styrene-b-isobutylene-b-styrene) support its use as a biomaterial alternative to silicone implants

Silicone - namely polydimethylsiloxane (PDMS) - is a widely recognized elastomeric biomaterial commonly used in implantable medical devices such as breast implants, cardiac pacemakers and drug delivery devices. Despite its widespread use, PDMS can elicit a strong foreign body response with fibrous encapsulation that leads to discomfort, pain and implantable device failure in approximately 10% of cases. Poly (styrene-<i>block</i>-isobutylene-<i>block</i>-styrene) (SIBS) is a thermoplastic elastomer used clinically as a drug-eluting coating for coronary stents and experimentally in ocular drainage devices. Although SIBS has demonstrated excellent biocompatibility in these applications, the foreign body response it elicits has not yet been extensively studied in more inflammation-prone anatomic sites such as skin rich in macrophages and fibroblasts. Here, we characterize the physicochemical properties of SIBS, examine its effect on macrophage-fibroblast interactions and evaluate its biocompatibility by implanting it subcutaneously in mice to ultimately assess its viability as a potential alternative to PDMS. We establish that both materials have comparable physicochemical properties, demonstrate that fibroblasts adopt a less contractile pro-inflammatory phenotype when exposed to SIBS-macrophage conditioned media and show reduced fibrotic encapsulation around SIBS implants in mice. These results suggest that SIBS could potentially be a favorable biomaterial alternative to silicone in clinical applications.