Recent progress on biomedical applications of functionalized hollow hydroxyapatite microspheres

Abstract Hollow hydroxyapatite microspheres (HHAM), a type of mesoporous nanomaterials with a specific internal cavity and hierarchical architectures, have attracted enormous interest over the past years owing to their remarkable potential for biomedical applications. However, the as-obtained HHAM fail to meet the need of the ever-updating diagnosis, treatment, and theranostics technologies. With the attempt to enhance performances and expand applications of HHAM, scientists have tailored the properties of HHAM by various methods including -doping modification and surface functionalization to give a versatile type of biomaterials, i.e., functionalized hollow hydroxyapatite microspheres (f-HHAM). Actually, significant achievements in the realm of f-HHAM have been obtained and various intractable clinic problems have been resolved. Nevertheless, designing desirable f-HHAM is expected to accelerate the development of the biomedicine field. In this contribution, the state-of-the-art progress f-HHAM is overviewed, which covers from the developments and preparation methods to bioapplications of these biomaterials. In addition, the current trends and key points as well as the future prospects and challenges for the applications of f-HHAM are discussed, aiming at providing a guideline for rational design of more creative f-HHAM according to different therapeutic requirements.