Peptide-Functionalized Selenium Nanoparticle-Based Effective Delivery System for Src-Targeting siRNA in Triple-Negative Breast Cancer Cells.

siRNA technology represents a promising approach in RNAi-based gene therapy due to its unique ability to silence target-specific genes implicated in life-threatening diseases, such as cancer. However, developing an effective nucleic acid delivery system remains challenging due to its limitations, such as enzymatic degradation, poor cellular internalization of nucleic acids, and cytotoxicity of the delivery vehicles, which are considered to be critical factors for clinical translation. Herein, we developed peptide-functionalized selenium nanoparticles to address this issue. In this study, eight short linear peptides (LP) primarily composed of tryptophan and arginine residues were designed for the one-pot synthesis of peptide-capped selenium nanoparticles (LP-SeNPs). The synthesized LP-SeNPs were characterized using field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), and the dynamic light scattering (DLS) technique. Among the SeNPs, LP5-SeNP showed the highest siRNA loading capacity and protection against 25% serum. Flow cytometry analysis indicated significant cellular uptake of FAM-siRNA with 23-24% of the cell population when delivered using LP1-SeNP and LP5-SeNP, respectively, compared to control FAM-siRNA. Fluorescence microscopy confirmed the cytosolic localization of SeNP/siRNA complexes. Cell viability assay revealed that LP5-SeNP and the LP5-SeNP/siRNA complex did not exhibit any cytotoxicity at their experimental concentration. Further, Western blotting analysis exhibited that the LP5-SeNP/Src siRNA complex could efficiently down-regulate ∼70% Src protein expression in triple-negative breast cancer cells, MDA-MB-231. The cellular uptake mechanism revealed that LP5-SeNP/siRNA most probably followed the macropinocytosis pathway for successful internalization of the complex into TNBC cells. In summary, the designed peptides can generate stable peptide-coated SeNPs, which may unveil a new therapeutic strategy for siRNA therapy.