In Situ Polymerization for Manufacture of Multifunctional Delivery Systems for Transcellular Delivery of Nucleic Acids

Electrostatic self-assembly between negatively charged nucleic acids and cationic materials is the basis for the formulation of the delivery systems. Nevertheless, structural disintegration occurs because their colloidal stabilities are frequently insufficient in a hostile biological environment. To overcome the sequential biological barriers encountered during transcellular gene delivery, we attempted to use in situ polymerization onto plasmid DNA (pDNA) with a variety of functional monomers, including N-(3-aminopropyl)methacrylate, (aminopropyl)methacrylamide hydrochloride, 1-vinylimidazole, and 2-methacryloyloxyethylphosphorylcholine and N,N'-bis(acryloyl) cystamine. The covalently linked monomers could polymerize into a network structure on top of pDNA, providing excellent structural stability. Additionally, the significant proton buffering capacity of 1-vinylimidazole is expected to aid in the release of pDNA payloads from acidic and digestive endolysosomes. In addition, the redox-mediated cleavage of the disulfide bond in N,N'-bis(acryloyl)cystamine allows for the selective cleavage of the covalently linked network in the cytosolic microenvironment. This is due to the high intracellular level of glutathione, which promotes the liberation of pDNA payloads in the cell interiors. The proposed polymerization strategies resulted in well-defined nanoscale pDNA delivery systems. Excellent colloidal stabilities were observed, even when incubated in the presence of high concentrations of heparin (10 mg/mL). In contrast, the release of pDNA was confirmed upon incubation in the presence of glutathione, mimicking the intracellular microenvironment. Cell transfection experiments verified their efficient cellular uptake and gene expression activities in the hard-transfected MCF-7 cells. Hence, the polymerization strategy used in the fabrication of covalently linked nonviral gene delivery systems shows promise in creating high-performance gene delivery systems with diverse functions. This could open new avenues in cellular microenvironment engineering.