Vesicular polyion complexes (PICs) were fabricated through self-assembly of rigid cylindrical molecules, small interfering RNAs (siRNAs), with flexible block catiomers of poly(ethylene glycol) (2 kDa) and cationic polyaspartamide derivative (70 units) bearing a 5-aminopentyl side chain. 100 nm-sized siRNA-assembled vesicular PICs, termed siRNAsomes, were fabricated in specific mixing ranges between siRNA and block catiomer. The siRNAsome membrane was revealed to consist of PIC units fulfilling a simple molar ratio (1:2 or 2:3) of block catiomer and siRNA. These ratios correspond to the minimal integer molar ratio to maximally compensate the charge imbalance of PIC, because the numbers of charges per block catiomer and siRNA are +70 and -40, respectively. Accordingly, the ζ-potentials of siRNAsomes prepared at 1:2 and 2:3 were negative and positive, respectively. Cross-section transmission electron microscopic observation clarified that the membrane thicknesses of 1:2 and 2:3 siRNAsomes were 11.0 and 17.2 nm, respectively. Considering that a calculated long-axial length of siRNA is 5.9 nm, these thickness values correspond to the membrane models of two (11.8 nm) and three (17.7 nm) tandemly aligned siRNAs associating with one and two block catiomers, respectively. For biological application, siRNAsomes were stabilized through membrane-cross-linking with glutaraldehyde. The positively charged and cross-linked siRNAsome facilitated siRNA internalization into cultured cancer cells, eliciting significant gene silencing with negligible cytotoxicity. The siRNAsome stably encapsulated dextran as a model cargo macromolecule in the cavity by simple vortex mixing. Confocal laser scanning microscopic observation displayed that both of the payloads were internalized together into cultured cells. These results demonstrate the potential of siRNAsomes as a versatile platform for codelivery of siRNA with other cargo macromolecules.
Bibliographical noteFunding Information:
This research was financially supported in part by the Center of Innovation (COI) Program from the Japan Science and Technology Agency (JST), the Grant-in-Aid for Scientific Research (KAKENHI Grant Numbers: 25000006 to K.K., 23685037, 26288082, and JP17K20109 to A.K., and 25282141, 17H02098, and 18K19900 to K.M.) from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan, Global Innovative Research Center (GiRC) Project (2012K1A1A2A01055811) of National Research Foundation (NRF) of Korea and Intramural Research Program of KIST, the research grant from the association for the progress of new chemistry (to A.K.), and a grant JSPS Core-to-Core Program, A. Advanced Research Networks. We are grateful to Dr. S. Fukuda, The University of Tokyo Hospital, Mr. H. Hoshi and the Research Hub for Advanced Nano Characterization at The University of Tokyo for their valuable support in the TEM measurements.
© 2019 American Chemical Society.
ASJC Scopus subject areas
- Colloid and Surface Chemistry