In another example, HAP NPs were surface-modified with HA-SH and homogeneously dispersed within a COL/HA-SH matrix. The formation of multiple disulfide bonds, allowed the development of a highly crosslinked porous structure, making it well suited for bone regeneration. Once loaded with rBMSC and SC injected, these hydrogels induced osteodiffentiation and biomineralization highlighting the beneficial impact of a biomimetic structure, which could not be reproduced with the corresponding physical dispersion of bare, amino-functionalized HAP NPs in the matrix (Figure ). Another strategy to ensure optimal dispersion of HAP NPs in a PGA/Dex-based matrix relied on their chelation with bisphosphonate ligands grafted on PGA. Noteworthy is that the bisphosphonate also participated in new bone formation that occurred without the need for additional growth factors. mineralization volume formed in the explants. Adapted with permission. Copyright 2020