Coordinative Amphiphiles as Tunable siRNA Transporters

Abstract

In this study, we developed coordinative amphiphiles for use as novel siRNA transporters. As a modification of a conventional cationic lipid structure, we replaced the cationic head with zinc(II)-dipicolylamine complex (Zn/DPA) as a phosphate-directing group, and used various membrane-directing groups in the place of the hydrophobic tails. These simple amphiphiles are readily synthesized and easy to modify. The Zn/DPA head groups bind to the phosphate backbones of siRNAs, and to our surprise, they prevented the enzymatic degradation of siRNAs by RNase A. Interestingly, the Zn/DPA head itself exhibited moderate transfection efficiency, and its combination with a membrane-directing group-oleoyl (CA1), pyrenebutyryl (CA2), or biotin (CA3)-enhanced the delivery efficiency without imparting significant cytotoxicity. Notably, the uptake pathway was tunable depending on the nature of the membrane-directing group. CA1 delivered siRNAs mainly through caveolae-mediated endocytosis, and CA2 through clathrin- and caveolin-independent endocytosis; CA3 recruited siRNAs specifically into biotin receptor-positive HepG2 cells through receptor-mediated endocytosis. Thus, it appears possible to develop tunable siRNA transporters simply by changing the membrane-directing parts. These are the first examples of amphiphilic siRNA transporters accompanying coordinative interactions between the amphiphiles and siRNAs.

Review of Zinc(II) Scaffolds: Efficient Role in Gene Delivery

“…[44] E. K. Bang and co-workers have reported an effective delivery of siRNA by synthesized low toxicity cationic head with zinc(II)-dipicolylamine complex (Zn-DPA) (as a phosphate directing group) which used different membrane-directing groups in the place of water-hating species (hydrophobic tails) i. e., group-oleoyl (17 a), pyrenebutyryl (17 b), and biotin (17 c) ( Figure 10). [45] While, in vitro evaluation of transfection efficiency against HepG2, HeLa and HCT116 (human colon cancer) cell-lines, they have observed that 17 b and 17 c were the best in delivering siRNAs into the cells. Whereas, 17 c which is a simple biotin-tethered molecule, that allowed specific delivery towards the biotin receptor-rich cancer cells.…”

Phosphate-sensing with (di-(2-picolyl)amino)quinazolines based on a fluorescence on–off system

“…In fact, dpa-metal complexes are well-known for their recognition of phosphoric acid derivatives, including ATP. [11][12][13][14][15][16] CyDs are well-known water-soluble host molecules comprising nano-sized hydrophobic cavities that enable them to incorporate various organic compounds in aqueous solutions. 17 In addition, the structural modications of CyDs are straightforward, which allow the incorporation of a variety of functionalities for modulating their properties.…”

Nanoformulated Single‐Stranded RNA‐Based Adjuvant with a Coordinative Amphiphile as an Effective Stabilizer: Inducing Humoral Immune Response by Activation of Antigen‐Presenting Cells

“…We previously reported the adjuvant effects of ssRNAs derived from the cricket paralysis virus (CrPV) intergenic region (IGR) internal ribosome entry site (IRES) . Here, we studied the adjuvant effect of these ssRNAs formulated with coordinative amphiphiles (CAs) …”

“…A CA is defined as an amphiphilic molecule consisting of a phosphate‐directing group [a phosphate‐specific binder, zinc‐dipicolylamine (Zn/DPA) complex] and a membrane‐directing group . It serves as a cationic lipid mimic, which are amphiphiles with positively charged heads and are commonly used as nonviral vectors for nucleic acids.…”

“…Owing to their cationic character, cationic lipids can bind nonspecifically to proteins in the bloodstream and their detergent‐like structure can cause cell lysis, while the cationic complexes cause systematic toxicity in vivo . By substituting the head group with Zn/DPA, CAs interact with phosphate groups in the backbone of RNAs by specific coordinative binding rather than electrostatic interaction, resulting in low cytotoxicity as well as RNA stabilization . In the current study, we applied CAs as a stabilizer for ssRNA‐based adjuvants and evaluated whether they effectively stabilize ssRNA‐based adjuvants.…”