Hydroxyapatite nanoparticles as a vehicle for drug delivery approach in Alzheimer's disease

Hydroxyapatite (HAp) nanoparticles are gaining attention as potential drug delivery systems for Alzheimer's Disease (AD) because of their compatibility with biological systems, stability, and adaptable surfaces. Their small size facilitates effective drug encapsulation and controlled release, while surface alterations with ligands or antibodies enable precise targeting of delivery to the blood-brain barrier (BBB) and to areas affected by amyloid-beta (Aβ) plaques and tau accumulations. HAp nanoparticles are capable of transporting anti-amyloid, anti-tau, and neuroprotective drugs, which increases therapeutic levels and reduces systemic adverse effects. Research shows that HAp nanoparticles can pass through the BBB using adsorptive-mediated and receptor-mediated transcytosis, and methods such as temporarily opening tight junctions or modifying surface charges can further improve their permeability. Drugs can be integrated via co-precipitation, adsorption, or encapsulation techniques, often allowing for pH-responsive release in the acidic environment of diseased brain tissue. Nevertheless, there are still obstacles to address regarding the scalability of production, stability and clearance in living organisms, and the long-term compatibility and safety in neural tissue.