Hydro-Expandable Calcium Phosphate Micro/Nano-Particles with Controllable Size and Morphology for Mechanical Ablation

Phosphate-based glasses are well-studied biodegradable materials in the bulk. However, less is known about the synthesis and properties of phosphate glass when prepared as microparticles or nanoparticles. These glasses have excellent biodegradability and biocompatibility. Therefore, phosphate glass micro/nanoparticles have significant potential for advances in drug delivery, bioimaging, degradable implants, and tissue engineering. In this study, calcium phosphate micro/nanoparticles (CPPs) with the composition (P2O5)25-(CaO)75 were prepared through a combination of the sol–gel and electrospray methods. This synthesis method shows great flexibility in controlling the size and morphology of CPPs. CPPs with an average diameter in the range of 345–952 nm and various morphologies including carnation flower-like, golf-ball-like, and apple-like were obtained. Optical microscopy was further used to demonstrate that the CPPs can have an average size increase of 95% in diameter and 720% in volume within the first 5–10 min of hydration in neutral aqueous media. The hydro-expansion process is accompanied by a two-stage ion release of phosphorus and calcium. We propose to utilize the expansion of the particle to mechanically ablate tissue and destroy cells.