title: Effect of L-leucine graft content on aqueous solution behavior and membrane-lytic activity of a pH-responsive pseudopeptide.
abstract: A series of pH-responsive polymers have been synthesized by grafting L-leucine onto the pendant carboxylic acid groups of the linear pseudopeptide, poly(L-lysine iso-phthalamide). The effect of the degree of grafting on aqueous solution properties, cell membrane-disruptive activity, and in vitro cytotoxicity was examined by UV-visible and fluorescence spectroscopy, hemolysis, alamar blue staining, and propidium iodide fluorescence assays. Modification of poly(L-lysine iso-phthalamide) with < or =23.6 mol % L-leucine caused a marginal effect on the pH-mediated hydrophobic association and hemolytic activity. Increasing the degree of grafting from 31.9 to 61.2 mol % resulted in polymers with progressively enhanced hydrophobic association and cell membrane disruption, thus confirming that the pH responsiveness and the extent of hydrophobic association and membrane disruption of the polymers can be modulated by varying the degree of grafting with hydrophobic amino acids. The pH responses were demonstrated to be concentration-dependent. At certain degrees of leucine grafting, the polymers were nonmembrane-lytic at physiological pH but mediated considerable membrane lysis at endosomal pH values (5.0-6.8), a feature critical for potential drug delivery applications.
authors: Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom.
authors: Rongjun
authors: R
authors: Chen
authors: Sariah
authors: S
authors: Khormaee
authors: Mark E
authors: ME
authors: Eccleston
authors: Nigel K H
authors: NK
authors: Slater
mesh_terms: D002463:Cell Membrane Permeability; D016503:Drug Delivery Systems / Q000379:methods*; D006801:Humans; D007930:Leucine / Q000737:chemistry / Q000494:pharmacology*; D018716:Molecular Mimicry; D010455:Peptides; D010795:Phthalic Acids / Q000737:chemistry* / Q000627:therapeutic use; D011107:Polylysine / Q000737:chemistry* / Q000627:therapeutic use; D011108:Polymers / Q000737:chemistry* / Q000627:therapeutic use; D012996:Solutions; D014867:Water
chemical_list: D010455:Peptides; D010795:Phthalic Acids; D011108:Polymers; D012996:Solutions; C507264:poly(L-lysine iso-phthalamide); D014867:Water; D011107:Polylysine; D007930:Leucine