Guanidine-Containing Methacrylamide (Co)polymers via aRAFT: Toward a Cell-Penetrating Peptide Mimic

Nicholas J. Treat, University of Southern Mississippi
DeeDee Smith, University of Southern Mississippi
Chengwen Teng, University of Southern Mississippi
Joel D. Flores, University of Southern Mississippi
Brooks A. Abel, University of Southern Mississippi
Adam W. York, University of Southern Mississippi
Faqing Huang, University of Southern Mississippi
Charles L. McCormick, University of Southern Mississippi


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.