Biotin-Functionalized Block Catiomers as an Active Targeting Approach in Gene Delivery

Recently, biotin (vitamin H) has been described as a ligand for active targeting and it has been found that many cancer cells overexpress the biotin receptor. In this study a biotin-conjugated block copolymer, biotin-poly(2-ethyl-2-oxazoline)-block-poly{N '-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} (biotin-pEtOx-b-pASP(DEA) is synthesized by a living cationic polymerization of the pEtOx-block followed by the nucleophilic ringopening polymerization of the pASP-block. The biotin moiety is coupled to the pEtOx-b-pASP precursor by a Cu(I) mediated azide-alkyne click chemistry and finally, the diethylamine (DEA) side chain is introduced by a polymer analogous reaction. The final polymer P1 formed polyplexes in the presence of plasmid DNA that are characterized with respect to N/P ratio, size, zeta potential, and shape compared to a control polymer P2 without biotin. In addition, HEK293 cells are transfected with these polyplexes and the number of fluorescent HEK293 cells is evaluated to assess the influence of polymer nature on the activity of the micelles. Flow cytometric analysis revealed a significantly higher uptake of the biotin-PEtOx-PASP(DEA)/pDNA micelle than the PEtOx-PASP(DEA)/pDNA micelle against HEK293 cells at a low N/P ratio of 20, consistent with the transfection results whereas at higher N/P ratio no difference can be observed anymore between the two polymers.