Backgrounds Osteoporosis, a progressive silent bone disease characterized by a great loss in bone mass, affects 200 million people worldwide, and is expected to double by 2040. The femoral neck, vertebral bodies, and distal radius are the most common sites of fragility caused by osteoporosis. Therefore, functional solutions for the treatment of osteoporotic fractures are crucial as they can be beneficial to a large population. In this project, we aimed to develop an injectable hydrogel as a patient-specific 3D scaffold for healing osteoporosis-related fractures and also prevention of new ones due to the osteogenic potential of the implant. Chitosan, as a biocompatible and low immunogenic natural osteoinductive polysaccharide, was chosen as the basic component of the scaffold. The natural bone matrix was mimicked by adding nano-hydroxyapatite. The injectable hydrogel was formulated by addition of alendronate as a first-line drug treatment for osteoporosis. The injectable formulation is proposed as a filler for cancellous osteoporotic bones with the aim of treatment or preventing dangerous fractures. Methods The cytotoxicity of alendronate for human adipose-derived mesenchymal stem cells (Ad-MSCs) was evaluated by MTT assay and the highest concentration of alendronate which is not toxic for the cells was chosen to be added in the hydrogel. For increasing the stability of the scaffold beta-glycerol phosphate was used as a crosslinker. Rheological and DMA analyses were performed using TA instrument. Results The viability of encapsulated human Ad-MSCs in the injectable formulation was evaluated by FDA/PI staining. The results indicated that the hydrogel is not toxic to the cells and the high viability of encapsulated cells in the hydrogel was observed after 5 days of investigation. The drug release profile of the system will be evaluated by OPA assay Conclusions We hypothesize that the presence of alendronate will prevent osteoclastogenesis and therefore would be beneficial for treatment of osteoporosis. However, further research is required to confirm this and also before it can be translated to the clinic.

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