Practice question

Non-viral delivery uses chemically defined materials condensing nucleic acids avoiding viral capsid immunity and packaging limits. Cationic liposomes DOTAP, DOTMA, helper DOPE facilitating hexagonal phase transition, and cholesterol stabilizing bilayer electrostatically interact with negatively charged phosphate backbone plasmid DNA or mRNA condensing into lipoplexes 100-300 nm diameter positive zeta potential promoting binding anionic proteoglycans initiating endocytosis via clathrin and caveolae. Modern LNPs employ ionizable lipids DLin-MC3-DMA neutral at physiological pH 7.4 minimizing toxicity but cationic upon protonation acidic endosomal lumen pH 5.5-6.0 destabilizing endosomal membrane via inverted hexagonal structure releasing RNA into cytosol for ribosomal translation. Absence viral proteins eliminates insertional mutagenesis permits repeated dosing, scalability via microfluidic mixing, and accommodation large plasmids >10 kb. Transient expression suits vaccination and Cas9 provision where permanent integration undesirable, reducing oncogenesis. Cytotoxicity from cationic lipids at high doses managed by optimization lipid:DNA ratio and inclusion PEG-lipid shielding reducing opsonization and prolonging circulation enabling targeted delivery.