PH triggered release of protective poly(ethylene glycol)-b-polycation copolymers from liposomes

Debra T. Auguste, Steven P. Armes, Krystyna R. Brzezinska, Timothy J. Deming, Joachim Kohn, Robert K. Prud'homme

Research output: Contribution to journalArticlepeer-review

62 Scopus citations


Triggered release of adsorbed polymers from liposomes enables protection against immune recognition during circulation and subsequent intracellular delivery of DNA. Polycationic blocks, poly[2-(dimethylamino) ethyl methacrylate] (DMAEMA) (0.8, 3.1, 4.9, or 9.8 kg/mol) or polylysine (K) (3 kg/mol), act as anchors for poly(ethylene glycol) (PEG) (2 or 5 kg/mol) protective blocks. In addition, a copolymer with 15 strictly alternating blocks of PEG (2 kg/mol) and cationic amine sites was evaluated as a protective coating. Incorporation of 1,2-dioleoyl-3-dimethylammonium-propane, a titratable lipid with a pKa of ∼6.7, allows the liposome's net charge to increase as the pH shifts from 7.4 in the bloodstream to 5.5 in the endosome. The increased net liposome cationicity results in decreased cationic polymer adsorption. The EMPEG113-DMAEMA31 and EMPEG113-DMAEMA62 association constants decrease from 3.1 and 6.2 (mg/m2)/(mg/ml) at pH 7.4 to 1.7 and 3.2 (mg/m 2)/(mg/ml) at pH 5.5, respectively. However, EMPEG45-DMAEMA5, EMPEG45-DMAEMA20, and EMPEG45-N-DP15 did not show a strong response to changes in pH. Cationic polymer adsorption exceeds calculated values for liposome neutralization, resulting in adsorption profiles in the brush regime.

Original languageEnglish (US)
Pages (from-to)2599-2608
Number of pages10
Issue number12
StatePublished - Apr 2006

All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Ceramics and Composites
  • Bioengineering
  • Biophysics
  • Biomaterials


  • Adsorption
  • Controlled drug release
  • Drug delivery
  • Gene therapy
  • Liposomes
  • Polyethylene oxide


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