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-cyano4-(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 omega-end group was demonstrated through successful chain extension of the GPMA macroCTA yielding GPMA(37)-b-GPMA(61) (M-w/M-n = 1.05). Block copolymers of GPMA with the nonimmunogenic, biocompatible HPMA were synthesized yielding, HPMA(271)-b-GPMA(13) (M-w/M-n = 1.15). Notably, intracellular uptake as confirmed by fluorescence microscopy, confocal laser scanning microscopy, and flow cytometry experiments after incubation for 2.5 h with KB cells at 4 degrees C and at 37 degrees 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.