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Published online by Cambridge University Press: 01 February 2011
Biocompatible, water-soluble, green luminescent silicon quantum dots (SiQDs) were developed as transfection tool for small interfering RNA (siRNA). The research goal was to down-regulate via the RNA interference (RNAi) mechanism the P-glycoprotein expression of the multidrug resistant gene 1 (MDR1) in a human colon carcinoma cell line (Caco-2). The internalization of 2-vinylpyridine terminated SiQDs (2-vipySiQDs) by Caco-2 cells as observed in confocal laser scanning microscopy imaging studies occurs via endocytosis. Experiments employing agarose gel electrophoresis revealed that 2-vipySiQD-siRNA complexes are formed through electrostatic interactions. The release of siRNA in the cytosol with subsequently RNAi induced down-regulation of the P-glycoprotein translation was verified by detecting a reduced ABCB1 mRNA level in transfected Caco-2 cells employing real-time PCR. Additional evidence for successful ABCB1 gene silencing was obtained by measuring a significant decrease of the P-glycoprotein transporter efficiency for the fluorescent substrate Rhodamine 123 (Rh123).