Local bone metabolism balance regulation via double-adhesive hydrogel for fixing orthopedic implants

The effective osteointegration of orthopedic implants is a key factor for the success of orthopedic surgery. However, local metabolic imbalance around implants under osteoporosis condition could jeopardize the fixation effect. Inspired by the bone structure and the composition around implants under osteoporosis condition, alendronate (A) was grafted onto methacryloyl hyaluronic acid (H) by activating the carboxyl group of methacryloyl hyaluronic acid to be bonded to inorganic calcium phosphate on trabecular bone, which is then integrated with aminated bioactive glass (AB) modified by oxidized dextran (O) for further adhesion to organic collagen on the trabecular bone. The hybrid hydrogel could be solidified on cancellous bone in situ under UV irradiation and exhibits dual adhesion to organic collagen and inorganic apatite, promoting osteointegration of orthopedic implants, resulting in firm stabilization of the implants in cancellous bone areas. In vitro, the hydrogel was evidenced to promote osteogenic differentiation of embryonic mouse osteoblast precursor cells (MC3T3-E1) as well as inhibit the receptor activator of nuclear factor-κ B ligand (RANKL)-induced osteoclast differentiation of macrophages, leading to the upregulation of osteogenic-related gene and protein expression. In a rat osteoporosis model, the bone-implant contact (BIC) of the hybrid hydrogel group increased by 2.77, which is directly linked to improved mechanical stability of the orthopedic implants. Overall, this organic-inorganic, dual-adhesive hydrogel could be a promising candidate for enhancing the stability of orthopedic implants under osteoporotic conditions.