Balance of the interfacial interactions of 4,4′-bipyridine at Bi(111) surface

The data from impedance spectroscopy, electrochemical in situ scanning tunnelling microscopy (STM), surface-enhanced infrared adsorption spectroscopy (SEIRAS) and density functional theory (DFT) were measured, combined and analysed to describe the 4,4′-bipyridine (4,4′-BP) adsorption at Bi(111) single crystal electrode from weakly acidified 0.5 M and 0.05 M Na 2SO4 aqueous solutions (pH ≈ 5.5÷6.0). The influence of electrode potential (E) on the adsorption kinetics of 4,4′-bipyridine on Bi(111) has been demonstrated. The capacitance pits in the differential capacitance versus E curve have been observed. The in situ STM data reveal two molecular patterns at different concentration of the supporting electrolyte. The stable adsorbate adlayer detectable by using the infrared spectroscopy method has been observed within E from -0.75 to -0.5 V (vs. Ag|AgCl sat. KCl). The results of DFT calculations and SEIRAS data have been used to establish the various possible orientations of the 4,4′-BP molecules at Bi(111) surface. The DFT investigation has been focused on the factors governing the self-assembly of 4,4′-BP, such as the intermolecular van der Walls attractions and interplay between the surface and the nanostructure lattices, both essential for the interfacial self-assembly

Targeted gene silencing in human embryonic stem cells using cell-penetrating peptide PepFect 14

Background Human embryonic stem (hES) cells serve as an invaluable tool for research and future medicine, but their transfection often leads to unwanted side effects as the method itself may induce differentiation. On the other hand, RNA interference (RNAi)-based targeted gene silencing is a quick, cost-effective, and easy-to-perform method to address questions regarding the function of genes, especially when hypomorphic knockdowns are needed. Therefore, effective transfection method with minimal side effects is essential for applying RNAi to hES cells. Here, we report a highly promising approach for targeted gene silencing in hES cells with siRNA complexed with cell-penetrating peptide PepFect 14 (PF14). This strategy provides researchers with efficient tool for unraveling the functions of genes or addressing the differentiation of pluripotent stem cells. Methods We present a method for delivery of siRNA into hES cells with cell-penetrating peptide PF14. Accordingly, hES cells were transfected in ROCK inhibitor containing medium for 24 h right after EDTA passaging as small cell clumps. Fluorescently labeled siRNA and siRNAs targeting OCT4 or beta-2-microglobulin (B2M) mRNA sequences were used to evaluate the efficiency of transfection and silencing. Analyses were performed at various time points by flow cytometry, RT-qPCR, and immunofluorescence microscopy. Results Effective downregulation of OCT4 in 70% of treated hES cells at protein level was achieved, along with 90% reduction at mRNA level in bulk population of cells. The applicability of this low-cost and easy-to-perform method was confirmed by inducing silencing of another target not associated with hES cell pluripotency (B2M). Furthermore, we discovered that downregulation of OCT4 induces neuroectodermal differentiation accompanied by reduced expression of B2M during early stage of this lineage. Conclusions The results demonstrate PF14 as a promising tool for studying gene function and regulatory networks in hES cells by using RNAi

Targeted gene silencing in human embryonic stem cells using cell-penetrating peptide PepFect 14

Background Human embryonic stem (hES) cells serve as an invaluable tool for research and future medicine, but their transfection often leads to unwanted side effects as the method itself may induce differentiation. On the other hand, RNA interference (RNAi)-based targeted gene silencing is a quick, cost-effective, and easy-to-perform method to address questions regarding the function of genes, especially when hypomorphic knockdowns are needed. Therefore, effective transfection method with minimal side effects is essential for applying RNAi to hES cells. Here, we report a highly promising approach for targeted gene silencing in hES cells with siRNA complexed with cell-penetrating peptide PepFect 14 (PF14). This strategy provides researchers with efficient tool for unraveling the functions of genes or addressing the differentiation of pluripotent stem cells. Methods We present a method for delivery of siRNA into hES cells with cell-penetrating peptide PF14. Accordingly, hES cells were transfected in ROCK inhibitor containing medium for 24 h right after EDTA passaging as small cell clumps. Fluorescently labeled siRNA and siRNAs targeting OCT4 or beta-2-microglobulin (B2M) mRNA sequences were used to evaluate the efficiency of transfection and silencing. Analyses were performed at various time points by flow cytometry, RT-qPCR, and immunofluorescence microscopy. Results Effective downregulation of OCT4 in 70% of treated hES cells at protein level was achieved, along with 90% reduction at mRNA level in bulk population of cells. The applicability of this low-cost and easy-to-perform method was confirmed by inducing silencing of another target not associated with hES cell pluripotency (B2M). Furthermore, we discovered that downregulation of OCT4 induces neuroectodermal differentiation accompanied by reduced expression of B2M during early stage of this lineage. Conclusions The results demonstrate PF14 as a promising tool for studying gene function and regulatory networks in hES cells by using RNAi