A new pH-responsive and glutathione-reactive, endosomal membrane-disruptive polymeric carrier for intracellular delivery of biomolecular drugs.

In this study, we have designed, synthesized and characterized a novel pH-responsive polymeric carrier for the enhanced cytoplasmic delivery of enzyme susceptible drugs, such as antisense oligonucleotides, proteins and peptides. A novel functionalized monomer, pyridyl disulfide acrylate, was synthesized and incorporated into an amphiphilic copolymer consisting of methacrylic acid and butyl acrylate, which resulted in a glutathione- and pH-sensitive, membrane-disruptive terpolymer with functional groups, that allow thiol-containing molecules to be readily conjugated. Conjugation and/or ionic complexation with oligopeptides or antisense oligonucleotides were performed and characterized. Hemolytic activity at low pHs remained high even after the conjugation/complexation with oligopeptides and asODNs. This polymer showed no toxicity, as determined with mouse 3T3 fibroblasts and human THP-1 macrophage-like cells. Uptake of the radiolabeled polymer and enhanced cytoplasmic delivery of FITC-ODN was also studied in THP-1 macrophage-like cells.