Micelleplexes: Terpolymer Micelle-Based Gene Delivery Vectors with Superior DNA Protection against Enzymatic Degradation
Rahul Sharma, Jae-Sung Lee, and You-Yeon Won. School of Chemical Engineering, Purdue University, 480 Stadium Mall Drive, West Lafayette, IN 47907
Protecting polynucleotides from nuclease degradation under physiological environment is an unresolved challenge associated with in vivo non-viral gene delivery. To address this problem, our research explores a new approach for improving DNA protection using a novel hydrophobically modified PEGylated polycation. Our approach utilizes an ABC triblock copolymer (“terpolymer”) composed of (A) hydrophilic poly(ethylene glycol) (PEG), (B) hydrophobic poly(n-butyl acrylate) (PnBA) and (C) cationic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA). Using this ABC sequence of blocks, spherical micelle-like aggregates coated with mixed PEG and PDMAEMA chains can be fabricated in water which can then be used as basic building blocks for constructing virus-mimetic DNA particles; when these micelles are mixed with DNA, the PDMAEMA chains in the corona primarily interact with the negatively charged phosphates on DNA, and the viral capsid-like morphology of the nanometers-thick micelle coating can be created at the outer surface of collapsed DNA. In this presentation, we will discuss our recent experiments (including polymer synthesis, nanostructure/surface charge characterization, and enzyme degradation/gene transfection assays) that support the feasibility of the proposed approach for in vivo gene delivery. Our results suggest that: (i) the cationic terpolymer micelles are very effective in condensing DNA molecules into the desired (virus-mimetic) morphology having sizes and molecular-level properties suitable for use as (in vivo) gene carriers; (ii) the resultant DNA/micelle complexes (“micelleplexes”) exhibit a great stability against serum nuclease-induced degradation, which far exceeds what can be achieved using conventional PEGylation-based approaches under similar conditions.