In situ synthesis and in vitro biocompatibility of needle-like nano-hydroxyapatite in agar–gelatin co-hydrogel

•Needle-like n-HA was fabricated in agar–gelatin co-hydrogel using the in situ method.•The crystallinity of n-HA was improved with increasing gelatin content.•The n-HA prepared in co-hydrogel was favorable for viability and differentiation.

Needle-like nano-hydroxyapatite (n-HA) was firstly fabricated in the current study based on agar–gelatin co-hydrogel using the in situ method. It was found that the crystallinity of n-HA was improved with the gelatin content increasing within the hydrogel. In vitro biocompatibility of the obtained n-HA was characterized by testing cell proliferation and differentiation (alkaline phosphatase activity) of MC3T3-E1 cells. The results indicated that the needle-like n-HA synthesized in the presence of agar–gelatin co-hydrogel was more favorable for the proliferation and differentiation of MC3T3-E1 compared to the traditional method. These biocompatible n-HA crystals hold great potential to be applied as bioactive materials for bone tissue engineering.