Calcium Phosphate Shell on Functionalized Gold Nanoparticles

Objectives: The aim of this study was to evaluate the formation of calcium phosphate nanoshell on a silicate/tetraethoxy saline -functionalized gold nanoparticle. They could mixing with paste bone cement and work in drug delivery carriers or as probes techniques.

Methods: Stable suspensions of gold nanoparticle were prepared by controlled reduction of a boiling solution of HAuCl4 using the sodium citrate method. The, gold nanoparticles were used as seeds and the surface was functionalized with mercapto-propyl-trimethyloxy-silane (MPTS) and sodium silicate leading to the efficient formation of a silicate nanoshell with gold nanoparticles encapsulated within. The solution continuous reacted with ammonia and tetraethoxy saline (TEOS) to obtain nanogold-MPTS-silicate-TEOS capped particles solution, then directly reacted with calcium and phosphate ion solution. Optical characterization of different gold nano-composite was examined by UV-VIS spectrometer. The core-shell like structure of the sample was revealed by transmission electron microscopy (TEM). The formation of silicate-Ca-P ceramic was confirmed by TEM/EDS. The electrochemical experiment was performed on an electrochemical workstation using a conventional three-electrode system.

Results: The median diameter of nanoparticles particle size distribution measured from TEM was near 15nm. The formed MPTS-silicate-TEOS functionalized nanoshell that could form nanogold-MPTS-silicate-TEOS-Ca-P ceramic effectively, compared with a non-silicate nanoshell. Higher ion concentration 10-3M had non-uniform dispersed whisker-like apatite surrounding gold seed surface than dilute solution. According to approach 1.0 at Ca/P ratio of EDS performed, we could assume the possibility that the uniform noanshell layers under 10-4M calcium and phosphate ion concentrations reacted for 24h could be a dicalcium phosphate phase (Ca/P=1) or bioglass-like phase.

Conclusion: The silicate-TEOS-Ca-P on the modified gold surface would have the potential of orthopedic and dental reconstruction applications combined with calcium phosphate bone cement.

Acknowledgments: The support for this research by the Kaohsiung Medical University Research Foundation (Q097001) and the National Science Council, Taiwan, ROC (NSC 95-2113-M-037-013).