A sustained release of alendronate from an injectable tetra-PEG hydrogel for efficient bone repair

Injectable and high-strength PLGA/CPC loaded ALN/MgO bone cement for bone regeneration by facilitating osteogenesis and inhibiting osteoclastogenesis in osteoporotic bone defects

Osteoporosis (OP) can result in slower bone regeneration than the normal condition due to the imbalance between osteogenesis and osteoclastogenesis, making osteoporotic bone defects healing a significant clinical challenge. Calcium phosphate cement (CPC) is a promising bone substitute material due to its good osteoinductive activity, however, the drawbacks such as fragility, slow degradation rate and incapability to control bone loss restrict its application in osteoporotic bone defects treatment. Currently, we developed the PLGA electrospun nanofiber sheets to carry alendronate (ALN) and magnesium oxide nanoparticle (nMgO) into CPC, therefore, to obtain a high-strength bone cement (C/AM-PL/C). The C/AM-PL/C bone cement had high mechanical strength, anti-washout ability, good injection performance and drug sustained release capacity. More importantly, the C/AM-PL/C cement promoted the osteogenic differentiation of bone marrow mesenchymal stem cells and neovascularization via the release of Mg2+ (from nMgO) and Ca2+ (during the degradation of CPC), and inhibited osteoclastogenesis via the release of ALN in vitro. Moreover, the injection of C/AM-PL/C cement significantly improved bone healing in an OP model with femur condyle defects in vivo. Altogether, the injectable C/AM-PL/C cement could facilitate osteoporotic bone regeneration, demonstrating its capacity as a promising candidate for treatment of osteoporotic bone defects.

Alendronate-functionalized double network hydrogel scaffolds for effective osteogenesis

Development of artificial bone substitutes mimicking the extracellular matrix is a promising strategy for bone repair and regeneration. In views of the actual requirement of biomechanics, biodegradability, and bioactivity, herein, a double-network (DN) hydrogel was constructed by interspersing a methacrylated gelatin (GelMA) network into alendronate (ALN)-modified oxidized alginate (OSA) network via Schiff base reaction and photo-crosslinking process to promote in situ bone regeneration. This GelMA@OSA-ALN DN hydrogel possessed favorable network and pores, good biocompatibility, and enhanced biomechanics. Notably, the introduction of Schiff base furnished the ND hydrogel scaffold with pH-responsive biodegradation and sustained ALN drug release delivery, which could provide effective bioactivity, upregulate osteogenesis-related genes, and promote the cell viability, growth, proliferation, and osteogenesis differentiation for bone regeneration. Therefore, we provide a new insight to develop functional DN hydrogel scaffold toward governing the on-demand drug release and achieving the stem cell therapy, which will be developed into the minimally invasive gelling system to prolong local delivery of bisphosphonates for the bone-related diseases.