Alkaline phosphatase-triggered charge converting lipid nanoparticles: An innovative approach for oral nucleic acid delivery

Enzyme-responsive lipid nanoparticles (LNPs) offer a promising strategy for oral nucleic acid delivery to gastrointestinal tumors. We hypothesized that coating LNPs with polyphosphates (PP) would enhance mucus penetration and enable charge conversion upon activation by intestinal alkaline phosphatase (IAP). The presence of the cell-penetrating peptide (CPP) stearyl-D-Arg₈ provides enhanced cellular uptake. LNPs were characterized regarding size, polydispersity index, zeta potential, charge conversion and evaluated for pH stability, behaviour in biorelevant fluids, and mucus diffusion. Plasmid DNA encoding for GFP or brain acid soluble protein-1 (BASP1) was encapsulated, and uptake and transfection were studied in intestinal cancer cell lines. Upon incubation with IAP, PP-coated D-Arg₈-LNPs released phosphate groups and underwent charge conversion. These particles remained stable across pH 1.5-9.0 and were more resistant to biorelevant fluids, though destabilization occurred with digestive enzymes. Compared to DOTAP- and D-Arg₈-LNPs, PP-coated LNPs showed superior mucus diffusion, cellular uptake, and transfection efficiency in hard-to-transfect Caco-2 and SW480 cells. Importantly, BASP1 expression from LNPs effectively suppressed SW480 proliferation. Overall, PP coated LNPs for oral administration can efficiently deliver nucleic acids into intestinal tumor cells, which may be suitable to interfere with the tumorigenic phenotype.