Surface functionalized calcium phosphate bioceramics for immunomodulatory biomaterials

Calcium phosphate (CaP) bioceramics, including apatite (Ap)-based materials, are naturally biocompatible, but they frequently require surface functionalization to achieve optimal integration with biological systems, especially with immune cells. Surface functionalization strategies tailor CaP bioceramic nanoparticles to enhance cell adhesion, proliferation, differentiation, and overall biocompatibility. This is because functionalized surfaces interact more dynamically with immune cells, i.e., macrophages, dendritic cells, and lymphocytes, through surface receptors and signaling pathways. The dynamic interaction may activate immune cells, release cytokine, differentiate cells, and regulate inflammation. Therefore, to resolve the limitations of natural CaP bioceramics, surface functionalization is crucial. Modified bioceramics nanoparticles' surface properties ensure more effective integration with biological tissues. In addition, biomolecule immobilization on CaP bioceramic surfaces provides a versatile approach in establishing a foundation for the development of immunomodulatory biomaterials. This review provides an overview of recent biomedical research on CaP bioceramics, especially Ap-based materials, focusing on advancements in surface functionalization strategies designed to improve interactions with immune cells. It also examines the role of immobilized biomolecules in modulating immune responses, highlighting their potential for clinical applications.