Optimization of Tet1 ligand density in HPMA-co-oligolysine copolymers for targeted neuronal gene delivery

Targeted gene delivery vectors can enhance cellular specificity and transfection efficiency. We demonstrated previously that conjugation of Tet1, a peptide that binds to the GT1b ganglioside, to polyethylenimine results in preferential transfection of neural progenitor cells in vivo. In this work, we investigate the effect of Tet1 ligand density on gene delivery to neuron-like, differentiated PC-12 cells. A series of statistical, cationic peptide-based polymers containing various amounts (1-5 mol%) of Tet1 were synthesized via one-pot reversible addition-fragmentation chain transfer (RAFT) polymerization by copolymerization of Tet1 and oligo-l-lysine macromonomers with N-(2-hydroxypropyl)methacrylamide (HPMA). When complexed with plasmid DNA, the resulting panel of Tet1-functionalized polymers formed particles with similar particle size as particles formed with untargeted HPMA-oligolysine copolymers. The highest cellular uptake in neuron-like differentiated PC-12 cells was observed using polymers with intermediate Tet1 peptide incorporation. Compared to untargeted polymers, polymers with optimal incorporation of Tet1 increased gene delivery to neuron-like PC-12 cells by over an order of magnitude but had no effect compared to control polymers in transfecting NIH/3T3 control cells.