Mimicking the Bone Extracellular Matrix through a Calcium Phosphate-Containing Thiol–Ene Cross-Linked Gelatin Composite

Hydroxyapatite (HAP) and amorphous calcium phosphate (ACP) nanoparticles were incorporated into a thiol-ene clickable gelatin network to elucidate to what extent osteogenic differentiation of human dental pulp- and adipose-derived stem cells (HDPSCs/HASCs) could be further boosted. ACP nanoparticles increased the specific surface area by 23% and reduced the density by 13% while maintaining a comparable particle size (ACP: 25 ± 3 nm; HAP: 27 ± 3 nm). Overall, the incorporation of ceramic nanoparticles did not significantly alter the mechanical properties of the ceramic-containing composites compared to the unsubstituted thiol-ene network. ACP nanoparticles at high concentrations promoted a 21-day osteogenic response in HASCs (72.09 ± 20.20 ng Ca²⁺/ng DNA) comparable to HDPSCs, with the latter showing high calcium production irrespective of the ceramic content (78.45 ± 10.87 ng Ca²⁺/ng DNA), suggesting that the provided cues must be optimized according to the investigated cell type toward a cell-interactive coating application stimulating osteogenesis.