In Vivo Assessment of Trimetaphosphate Nanocomposite‐Based Polyamide‐6 Scaffolds Enhanced With Silver Nanoparticles for Bone Regeneration

The aim of this study was to evaluate the influence of nanocomposite materials, specifically sodium trimetaphosphate (TMP) nanoparticles decorated with 2.5% silver nanoparticles (AgNP), incorporated into polyamide-6 (Pa6) polymeric matrices on bone repair in surgically created critical-size defects in rat calvaria. Eighteen male Wistar rats were divided into three groups based on the treatment received: control group (C)-blood clot; Pa6-AgNP; and Pa6-TMP-AgNP. A 5 mm diameter defect was created in the calvaria of each animal. In Group C, the defect was filled with blood clots only, while the other groups were filled with scaffolds containing Pa6-AgNP and Pa6-TMP-AgNP. After 30 days post-surgery, the animals were euthanized, and microtomographic, histomorphometric, and immunohistochemical analyses were performed. The area of newly formed bone was calculated as a percentage of the total area of the original defect, and immunostaining for TGFβ-1, BMP-2/4, and OCN was assessed. Intergroup analysis revealed that the Pa6-TMP-AgNP group exhibited a greater volume of newly formed bone, while the Pa6-AgNP group showed a significantly increased bone formation compared to the control group (p < 0.05). Immunohistochemistry indicated that the Pa6-TMP-AgNP and Pa6-AgNP groups showed high and moderate immunostaining for TGFβ-1 and OCN, respectively. Additionally, the Pa6-TMP-AgNP group had a higher number of BMP-2/4 positive cells compared to the other groups (p < 0.001). Based on these results, it can be concluded that Pa6-TMP-AgNP provides a biological response conducive to bone neoformation, exhibiting osteoinductive and osteoconductive properties when used to fill critical-size defects in rat calvaria.