Surface Functionalization to Enhance Porous Silicon Optical Stability in Biological Media and to Avoid Drug Reduction.

The discovery of photoluminescence (PL) from porous silicon (pSi) and the lack of evidence for its toxicity has stimulated effective methods to provide silicon nanostructures for biomedicine. We demonstrated that light emitting pSi particles can be up-taken by human dendritic cells without any toxicity or reduction in cell viability and can be tracked in cells by fluorescence imaging in real time. However, till now, the application of pSi in nanomedicine has been severely limited due to two important issues. First, pSi is incompatible with biological solutions, which leads to immediate surface oxidation and induces a degradation of its optical properties. Second, the decomposition of a carried drug by redox activity of pSi is a severe limiting factor for drug delivery. Herein, luminescent pSi has been obtained based on anodization method. In order to reach structural and optical stabilization in biological media, different surface functionalization procedures were investigated. Among them, PEG and chitosan were the more effective polymer for pSi stabilization, but with opposite electric surface charge. Visible light emission of pSi stabilized for over three months obtained for the first time. Then, use of pSi as a carrier has been evaluated for drug delivery. Cobinamide (Cbi) was selected as a reference drug based on its high sensitivity to reduction. Results demonstrated that PEG coating leads to avoid reduction and decomposition of Cbi. In addition, it leads to improve the drug loading amount and the release profile.