In vitro and in vivo degradation studies of a dual medical-grade scaffold design for guided soft tissue regeneration†

Biodegradable scaffolds with tailored mechanical and structural properties are essential for scaffold-guided soft tissue regeneration (SGSTR). SGSTR requires scaffolds with controllable degradation and erosion characteristics to maintain mechanical and structural integrity and strength for at least four to six months. Additionally, these scaffolds must allow for porosity expansion to create space for the growing tissue and exhibit increased mechanical compliance to match the properties of the newly formed tissue. Although progress has been made in this area, previous studies have yet to fully explore these aspects using biodegradable polymers that are synthesized and 3D printed into filaments classified as medical-grade. In this study, we optimized scaffold design based on the properties of biodegradable materials and employed digital-assisted 3D printing to adjust the degradation pathway of dual-material scaffolds dynamically, thereby modulating mechanical and structural changes. Two medical-grade 3D printing filaments were utilized: Dioxaprene® (DIO), which has a degradation rate of approximately six months, and Caproprene™ (CAP), which has a degradation rate of about 36 months. The scaffolds were 3D printed with these materials to create the desired architecture. An in vitro degradation study showed the increasing pore size and compliance (>90% increase) of the scaffold architecture via the breakdown of DIO. Meanwhile, the slow-degrading CAP maintained long-term mechanical and structural integrity. Furthermore, over six months of subcutaneous implantation in rats, the dual material showed an approximately two-fold increase in mechanical compliance and free volume expansion, with the pore size increasing from 1 mm to 2 mm to accommodate the growing tissue. The scaffold remained structurally intact and provided mechanical support for the newly formed tissue. Histological and immunohistochemical analyses indicated good in vivo biocompatibility, tissue guidance, and the formation of organized soft tissue architecture, supported by an extensive network of blood vessels.