Development and Characterization of Non-coated and PLGA-Coated S53P4 and S59 Bioactive Glass Scaffolds for Treatment of Load-Bearing Defects

We studied how in vitro reactions affect long-term biochemical and mechanical properties of porous tissue engineering scaffolds based on two bioactive glasses and accordingly their potential suitability for treating critical-size load-bearing bone defects. Granules of bioactive glass S53P4 and S59 were used to sinter the porous scaffolds. The sintering variables for mechanically durable scaffolds were initially selected according to the thermal behaviour of the glasses during heating. The S53P4 and S59 scaffolds were further divided into the following three groups: uncoated scaffolds, poly( dl -lactide-co-glycolide) (PLGA) coated scaffolds, and scaffolds coated with a mixture of PLGA and powdered S53P4. The purpose of the coating is to enhance mechanical abilities and to induce a membrane rich in growth factors surrounding the BAG implant. Characterization of the scaffolds included water absorption, pH, ion release, reaction layer formation, and compressive strength. Polymer coatings with powdered S53P4 absorbed more water than pure polymer coatings. The pH of the immersion solution increased more upon immersion of the uncoated scaffolds. No marked differences were seen between the coated scaffolds. During the 28-day in vitro immersion, the Ca-ion concentration initially increased for non-coated S53P4 scaffolds, followed by a slight increase starting at 14 days for all S53P4-based scaffolds and S59-PLGA scaffolds. The lowest P species concentration was observed for uncoated S53P4 scaffolds. The polymer coatings hindered the dissolution of Si-species from the scaffolds. Thicker calcium phosphate layers were identified at the uncoated scaffolds, suggesting a higher bioactivity. In contrast, the polymer coatings enhanced the compressive strength of the scaffolds. The results reflect the impact of glass composition and polymer coating on the chemical and physical properties of scaffolds, emphasizing the requirements in clinical applications for critical load-bearing bone defects. Graphical Abstract