gms | German Medical Science

Objectives: Critical-sized bone defects pose a substantial challenge in orthopedic surgery with high mortality and increasing healthcare costs. Biomaterials for scaffold design must meet numerous criteria including adequate bioactivity, cytocompatibility, osteoinductivity, osteoconductivity, and biodegradability. While bioactive glass compositions demonstrate exceptional bioactivity and cytocompatibility in vitro and in vivo, their brittle nature restricts their suitability for load-bearing applications. Hybrid materials, comprising polymer and bioactive glass phases, integrate the elasticity and load-bearing capacity of polymers with the distinctive bone bonding capability of bioactive glasses. Additionally, doping with metal trace elements allows for customization of scaffolds, adding antibacterial or highly osteoinductive properties.

Methods: Scaffolds made from a hybrid material consisting of 70% polycaprolactone (PCL) and 30% SiO2-CaO-MgO bioactive glass were processed via direct and indirect printing. Both undoped and doped hybrid scaffolds underwent thorough physicochemical examination for bioactivity, structural analysis, mechanical properties and wereassessed for cytocompatibility, cell attachment (LIVE/DEAD staining, WST1 assays, SEM), osteoinductivity and -conductivity (histological assessment of bone formation, ALP activity assay).

Results and conclusion: Both structural analysis and mechanical testing showed a very porous yet less brittle scaffold suitable for tissue ingrowth and formation. Incorporating metal trace elements into the bioactive glass phase of the hybrid material was found to modulate bioactivity rates; for example, zinc doping decreased apatite formation while magnesium acted as a promoter. The hydroxyapatite formed on the surface closely resembles the mineral phase of natural human bone. In cell culture, WST1 assays, LIVE/DEAD stainings and SEM demonstrated excellent cell attachment and cytocompatibility for up to 17 weeks, with cells infiltrating pores and continuously proliferating across all scaffolds. Comparable osteoinductive performance was observed compared to the current "gold standard" calcium phosphate (CaP) coated PCL scaffolds. Osteogenic differentiation and tissue formation could be increased significantly with magnesium doping, indicating successful doping and its potential positive influence on osteogenesis.

To the authors’ knowledge, this study marks the first successful attempt to create hybrid scaffolds via indirect 3D printing. Successfull doping suggests that this biomaterial's properties can be tailored to specific requirements – inorganic factors like zinc and magnesium offer anti-osteoclastogenic, pro-angiogenic and antibacterial properties. These properties can be harnessed not only for bone regeneration but also for infection control. The outstanding in vitro results for cytocompatibility, cell attachment, tissue formation and osteoinductivity underscore the potential of this bioactive glass hybrid material for bone tissue engineering.