Abstract: Aim of study: Preparation and characterization of a series of new biocompatible injectable bone paste (IBP) nanocomposites, hydroxyapatite-gelatin (HA-Gel) and hydroxyapatite-Gelatin-alendronate (HA-Gel-Ald np). Material and methods IBP nanocomposites were synthesized from mixing different ratios of gelatin to aqueous solutions of both Ca(NO3)2.4H2O and (NH4)2HPO4 to obtain (HA-Gel np), while the target nanocomposites, HA-Gel-Ald np, were obtained by submitting aqueous solution of alendronate (Ald) to HA-Gel np nanocomposites. These composites crystallinity were analyzed by FTIR and XRD, and their morphology were characterized by scanning electron microscopy (SEM) and EDX measurements. XRD patterns, SEM and EDX presented changes in the crystal and surface structure from HA to HA-Gel np to HA-Gel-Ald np. Furthermore, the cytotoxicity of the nanocomposites on stem cells were assessed using MTT assay. Results The physico-chemical measurements, FTIR, XRD, SEM and EDX indicated the success in isolating the nanocomposites, HA-Gel np and HA-Gel-Ald np, with different ratios. Although the cytotoxicity data show significant effect of the prepared IBP nanocomposites (p = 0.00), their interaction together had no significant effect (p = 0.624).