A new pH-responsive and glutathione-reactive, endosomal membrane-disruptive polymeric carrier for intracellular delivery of biomolecular drugs $ Volga Bulmus, Monica Woodward, Lianne Lin, Niren Murthy, Patrick Stayton * , Allan Hoffman * Department of Bioengineering, University of Washington, Seattle, WA 98195, USA Received 15 April 2003; accepted 30 June 2003 Abstract 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. D 2003 Elsevier B.V. All rights reserved. Keywords: pH-sensitive polymer; Glutathione; Polymer conjugates; Cytoplasmic delivery; Endosomal membrane disruption 1. Introduction Cytoplasmic delivery of enzyme-susceptible bio- molecular drugs is one of the major limitations in many therapeutic strategies, such as gene and anti- sense therapy, and vaccine development. Develop- ment of better delivery systems that can enhance the endosomal escape of such biotherapeutics and thereby avoid their degradation by lysosomal enzymes is still a major goal of drug delivery scientists. Researchers have studied certain viruses in order to understand how they are able to efficiently 0168-3659/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jconrel.2003.06.001 B Presented at 11th International Symposium on Recent Advances in Drug Delivery Systems and CRS Winter Symposium, Salt Lake City, UT, March 3– 6,2003. * Corresponding authors. Patrick S. Stayton is to be contacted at Department of Bioengineering, Box 351721, University of Washington, Seattle, WA 98195, USA. Tel.: +1-206-685-8148; fax: +1-206-685-8526. Allan S. Hoffman, Department of Bioen- gineering, University of Washington, AER Bldg., Room 334-338, Box 352255, Seattle, WA 98195, USA. Tel.: +1-206-543-9423; fax: +1-206-543-6124. E-mail addresses: stayton@u.washington.edu (P. Stayton), hoffman@u.washington.edu (A. Hoffman). www.elsevier.com/locate/jconrel Journal of Controlled Release 93 (2003) 105 – 120