GET of nucleic acids. (A) Schematic of the LK15 proteins engineered to bind to and transduce nucleic acids. (B) Transfection of human mesenchymal stem cells using GET-LK15. Initially we assessed binding capacity of LK15 peptides for plasmid (p)DNA (SIN GFP, to express GFP on transfection), modified synthetic messenger RNA (modRNA) (Miltenyi Biotech; to express GFP on transfection), and small inhibitory (si)RNAs (labeled with FAM fluorophore to detect delivery). After optimizing ratios, we transfected human mesenchymal stem cells with P21-LK15-8R and pDNA (10 µg), modRNA (10 µg), or siRNA (1 µg) and visualized transfection by fluorescence microscopy. (Scale bar, 100 µm.) (C) Quantification of GET-LK15 transfection of human mesenchymal stem cells by flow cytometry (percentage transfection efficiency or relative fluorescence for siRNA) compared with LIPO2000 as a commercial standard. Error bars indicate SD.