The effect of eliminating sintering during the synthesis of 3D scaffolds using the gel-casting method on their biological characteristics: in vivo and in vitro evaluations

Abstract The possibility of making shapeable three-dimensional scaffolds along with suitable mechanical properties is one of the most challenging points in tissue engineering. This study investigated the effect of the eliminating sintering during the synthesis of Hydroxyapatite/Agarose nanocomposite foam produced by gel-casting method, as bone tissue cellular scaffold, on its biological characteristics. The Hydroxyapatite/Agarose nanocomposite foam was synthesized by gel-casting, and samples were divided into two groups: group S, in which half of the samples were sintered, and group C, which the other half of the samples were left unsintered. To assess in vitro cytotoxicity, the supernatant culture medium was extracted from 100 mg ml⁻¹ foam suspension in complete culture medium after 72 h incubation and diluted into various concentrations. SaOs-II cells were incubated with extracts of each scaffold at different concentrations and analyzed using the MTT assay. Additionally, in vivo characteristics were evaluated by implanting the scaffolds in rat tibia. Overall, the number of living cells was higher in group S than in group C, except for concentrations of 25% and 75% after 24 and 48 h of incubation, respectively. MTT assay results indicated that concentrations below 50% for group S and 25% for group C could be considered non-toxic. All in vivo variables exhibited significant changes over time, with most changes occurring faster in group S than in group C. There was a statistically significant difference between the two groups in terms of inflammation rate, osteocyte, osteoblast, and osteoclast count, as well as remaining biomaterial percentage only on day 30. Despite the delay in the tissue regeneration process observed by eliminating sintering during the gel-casting method, it is recommended as a means of producing reversible polymeric scaffolds with proper handling, cutting, and shaping capabilities that can be easily applied by clinicians during surgery according to the specific defect site.