Biological properties of nanocrystalline silicon particles for biomedical applications

We have studied the biological properties of nanocrystalline silicon (nc-Si) particles after injection at various places in a mouse. The nc-Si particles with a size of 2.5 nm and a concentration of 1.3 mg/ml were dispersed in a normal saline solution (NSS). The NSS dispersible nc-Si particles were safely injected into the mouse. When the nc-Si particles in the NSS were directly injected into the subcutaneous vein and the coronary artery of the heart by syringe, the condition of bloodstream at each place was confirmed by the red luminescence (peak wavelength at 720 nm) from the nc-Si particles under the ultraviolet (UV) light-irradiation. Moreover, the nc-Si particles in the NSS, which were injected into the vein in the sole, smoothly flowed to the small intestine, and the smooth fluidity of nc-Si particles was also observed for the condition of the peristalsis of the small intestine. The nc-Si particles in the small intestine emitted-red fight during peristalsis under the UV light-irradiation. The red luminescence at each place was very bright and could be clearly seen with the naked eye. These phenomenons were achieved by the utilization of the harmless material, the formation of nc-Si particles with the single-order-size and the realization of the stable surface modification as silicon-oxygen bond to the nc-Si particles.