Expanding hyperbranched polyglycerols on hydroxyapatite nanocrystals via ring-opening multibranching polymerization for controlled drug delivery system

► Hyperbranched polyglycerol (HPG) was grafted to HAP NCs via surface polymerization. ► The covalent immobilization of HPG to HAP was confirmed by FT-IR. ► The microstructure of HPG-g-HAP was investigated by TEM, SEM, and XRD. ► Thermal and charge behavior of samples were studied by TGA & Zeta, respectively. ► Drug loading/release behavior of the HPG-g-HAP nanocomposites were evaluated.