Manipulation of genes in human embryonic stem cells (hESCs) is imperative for their highly potential applications; however, the transduction efficiency remains very low. Although existing evidence revealed the type, size, and zeta potential of vector affect gene transfection efficiency in cells, the systematic study in hESCs is scarce. In this study, using poly(amidoamine) (PAMAM) dendrimers ended with amine, hydroxyl, or carboxyl as model, we tested the influences of size and surface group as well as cytotoxicity and endocytosis on hESC gene transfection. We found that in culture medium of mTeSR the particle sizes of G5, G7, G4.5COOH, and GSOH were around 5 nm and G1 had a smaller size of 3.14 nm. G5 and G7 had a slight and significant positive zeta potential, respectively, whereas G1 was slightly negative, and G4.5COOH and GSOH were significantly negative. We demonstrated that only amine-terminated dendrimers accomplished gene transfection in hESCs, which is greater than that from Lipofectamine 2000 transfection. Ten micromolar GS had the greatest efficiency and was better than 1000 mu M G1. Only a low concentration (0.5 and 1 mu M) of G7 realized gene delivery. Amine-ended dendrimers, especially with higher generations, were detrimental to the growth and pluripotent maintenance of hESCs. In contrast, similarly sized hydroxyl- and carboxyl-terminated dendrimers exerted much lower cytotoxicity, in which carboxyl-terminated dendrimer maintained pluripotency of hESCs. We also confirmed the endocytosis into and significant exocytosis from hESCs using FITC-Iabeled GS dendrimer. These results suggested that careful considerations of size, concentration, and zeta potential, particularly the identity and position of groups, as well as minimized exocytosis in the design of a vector for hESC gene delivery are necessary, which helps to better design an effective vector in hESC gene transduction.
We thank Dr. Ye-Guang Chen from Tsinghua University for providing us H1 hES cells upon Simple Letter Agreement between Dr. Chen's and Dr. Long's laboratories that is approved by WiCell Research Institute. This work was supported by National Natural Science Foundation of China grants 31110103918 and 31470907, Chinese Academy of Sciences Strategic Priority Research Program grants XDA01030604 and XDA04020219, National High Technology Research and Development Program of China grant 2011AA020109, and Fundamental Research Funds for the Central Universities of China grant CQKLBST-2012-002.