Nanosheet-assembled hierarchical nanostructures of hydroxyapatite: surfactant-free microwave-hydrothermal rapid synthesis, protein/DNA adsorption and pH-controlled release

Abstract

In this paper, a surfactant-free rapid microwave-assisted hydrothermal synthesis of hydroxyapatite nanosheet-assembled flower-like hierarchical nanostructures (NFHNs) is reported. The effects of the experimental conditions on the morphology and crystal phase of the product are investigated. A possible formation mechanism of hydroxyapatite NFHNs is proposed. The morphology of the product can vary from flower-like to polyhedra by adjusting the microwave heating temperature. The protein and DNA adsorption properties of the as-prepared hydroxyapatite NFHNs are studied. The loading capacities of the as-prepared hydroxyapatite NFHNs for bovine serum albumin (BSA), hemoglobin (Hb) and fish sperm DNA are determined to be 165, 164 and 112 mg g⁻¹, respectively. The protein release process is conducted at different pH values (pH 7.2, 5.5 and 4.8) in phosphate buffer saline (PBS), and the pH-controlled protein release behavior has been found. Thus, the as-prepared hydroxyapatite NFHNs are promising for protein drug delivery applications.