Synthesis of Carbohydrate Capped Silicon Nanoparticles and their Reduced Cytotoxicity, In Vivo Toxicity, and Cellular Uptake.

The development of smart targeted nanoparticles (NPs) that can identify and deliver drugs at a sustained rate directly to cancer cells may provide better efficacy and lower toxicity for treating primary and advanced metastatic tumors. Obtaining knowledge of the diseases at the molecular level can facilitate the identification of biological targets. In particular, carbohydrate-mediated molecular recognitions using nano-vehicles are likely to increasingly affect cancer treatment methods, opening a new area in biomedical applications. Here, silicon NPs (SiNPs) capped with carbohydrates including galactose, glucose, mannose, and lactose are successfully synthesized from amine terminated SiNPs. The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] analysis shows an extensive reduction in toxicity of SiNPs by functionalizing with carbohydrate moiety both in vitro and in vivo. Cellular uptake is investigated with flow cytometry and confocal fluorescence microscope. The results show the carbohydrate capped SiNPs can be internalized in the cells within 24 h of incubation, and can be taken up more readily by cancer cells than noncancerous cells. Moreover, these results reinforce the use of carbohydrates for the internalization of a variety of similar compounds into cancer cells.

Synthesis of D-mannose capped silicon nanoparticles and their interactions with MCF-7 human breast cancerous cells.

Silicon nanoparticles (SiNPs) hold prominent interest in various aspects of biomedical applications. For this purpose, surface functionalization of the NPs is essential to stabilize them, target them to specific disease area, and allow them to selectively bind to the cells or the bio-molecules present on the surface of the cells. However, no such functionalization has been explored with Si nanoparticles. Carbohydrates play a critical role in cell recognition. Here, we report the first synthesis of silicon nanoparticles functionalized with carbohydrates. In this study, stable and brightly luminescent d-Mannose (Man) capped SiNPs have been synthesized from amine terminated SiNPs and d-mannopyranoside acid. The surface functionalization is confirmed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and energy dispersive X-ray spectroscopy (EDX) studies. The mean diameter of the crystal core is 5.5 nm, as measured by transmission electron microscopy (TEM), while the hydrodynamic diameter obtained by dynamic light scattering (DLS) is 16 nm. The quantum yield (QY) of photoluminescence emission is found to be 11.5%, and the nanoparticles exhibit an exceptional stability over two weeks. The Man-capped SiNPs may prove to be valuable tools for further investigating glycobiological, biomedical, and material science fields. Experiments are carried out using Concanavalin A (ConA) as a target protein in order to prove the hypothesis. When Man functionalized SiNPs are treated with ConA, cross-linked aggregates are formed, as shown in TEM images as well as monitored by photoluminescence spectroscopy (PL). Man functionalized SiNPs can target cancerous cells. Visualization imaging of SiNPs in MCF-7 human breast cancer cells shows the fluorescence is distributed throughout the cytoplasm of these cells.

Highly luminescent and nontoxic amine-capped nanoparticles from porous silicon: synthesis and their use in biomedical imaging.

Stable and brightly luminescent amine-terminated Si nanoparticles (SiNPs) have been synthesized from electrochemically etched porous silicon (PSi). The surface amine termination was confirmed by FTIR, NMR, and XPS studies. The mean diameter of the crystal core of 4.6 nm was measured by transmission electron microscopy (TEM), which is in a good agreement with the size obtained by dynamic light scattering (DLS). The dry, amine-terminated product can be obtained from bulk silicon wafers in less than 4 h. This represents a significant improvement over similar routines using PSi where times of >10 h are common. The emission quantum yield was found to be about 22% and the nanoparticles exhibited an exceptional stability over a wide pH range (4-14). They are resistant to aging over several weeks. The amine-terminated SiNPs showed no significant cytotoxic effects toward HepG2 cells, as assessed with MTT assays.