Introduction

Relatively recent work has seen calcium phosphate (CaP) salts used for the delivery of biological materials into cells in the form of peptides, polymers and DNA sequences. Calcium phosphate salts have a critical safety advantage over other vectors such as viruses in that they pose no risk of pathogenicity due to mutation and show no apparent cytotoxicity. Previous work within the group showed that Ca:P ratio influenced the transfection efficiency, but the fate of the particles on internalisation is yet unknown. The difficulty in tracking the particles can be related to the visual similarity to granulation within the cells. Using a surface modification method that enables the fluorescent labeling of silicon-substituted hydroxyapatite (SiHA) particles, we have tracked the internalisation of the particles to understand their mechanism of entry and how particle composition may influence transfection efficiency.