Guanidine-Containing Methacrylamide (Co)polymers via aRAFT: Toward a Cell-Penetrating Peptide Mimic
We report the synthesis and controlled radical homopolymerization and block copolymerization of 3-guanidinopropyl methacrylamide (GPMA) utilizing aqueous reversible addition–fragmentation chain transfer (aRAFT) polymerization. The resulting homopolymer and block copolymer with N-(2-hydroxypropyl) methacrylamide (HPMA) were prepared to mimic the behavior of cell-penetrating peptides (CPPs) and poly(arginine) (>6 units), which have been shown to cross cell membranes. The homopolymerization mediated by 4-cyano-4-(ethylsulfanylthiocarbonylsulfanyl)pentanoic acid (CEP) in aqueous buffer exhibited pseudo-first-order kinetics and linear growth of molecular weight with conversion. Retention of the “living” thiocarbonylthio ω-end group was demonstrated through successful chain extension of the GPMA macroCTA yielding GPMA37-b-GPMA61 (Mw/Mn = 1.05). Block copolymers of GPMA with the nonimmunogenic, biocompatible HPMA were synthesized yielding HPMA271-b-GPMA13 (Mw/Mn = 1.15). Notably, intracellular uptake was confirmed by fluorescence microscopy, confocal laser scanning microscopy, and flow cytometry experiments after incubation for 2.5 h with KB cells at 4 °C and at 37 °C utilizing FITC-labeled, GPMA-containing copolymers. The observed facility of cellular uptake and the structural control afforded by aRAFT polymerization suggest significant potential for these synthetic (co)polymers as drug delivery vehicles in targeted therapies.