title: Synthesis and endosomolytic properties of poly(amidoamine) block copolymers.
abstract: The poly(amidoamine)s (PAAs) ISA 1 and ISA 23 display pH-dependent conformational change and pH-dependent membrane perturbation. These properties confer potential for use as endosomolytic polymers for intracytoplasmic delivery of toxins and genes. Both polymers are relatively non-toxic, and moreover ISA 23 has the beneficial property in vivo, of being non hepatotropic when administered intravenously. Although ISA 23 and ISA 1 demonstrate ability to transfect cells, ISA 1 is also able to promote intracellular delivery of non-permeant toxins. The aim of this study was to synthesise random and block copolymers of ISA 1 and ISA 23 and investigate whether these second generation hybrids would allow optimisation of PAA biological characteristics. Random and block copolymers of ISA 1 and ISA 23 were synthesised by hydrogen transfer polyaddition to generate a library of PAAs with an ISA 23:ISA 1 molar ratios of 2:1 to 4:1. The resultant polymers have a pI slightly below 7.4 and a M(w) of 19,900-49,000 g/mol and a M(n) of 13,100-24,100 g/mol. Whereas none of the random or block copolymers were haemolytic at pH 7.4 all demonstrated pH-dependent membrane activity. At pH 5.5 they caused 50-60% haemoglobin (Hb) release over 1 h. This was slightly less than that seen for ISA 23 (80% Hb release). None of the copolymers were cytotoxic against B16F10 cells during a 72 h incubation (IC(50) > 2 mg/ml; MTT assay). The ability of the random and block copolymer PAAs to deliver the toxin gelonin was also examined, but only ISA 1 and the block copolymer B2 (ISA 23:ISA 1 at a 2:1 molar ratio) were able to promote intracellular delivery, as measured by cytotoxic activity. It would be interesting to study the body distribution of B2 and determine whether this toxin-delivering PAA is able to escape liver capture.
authors.affiliation: Centre for Polymer Therapeutics, Welsh School of Pharmacy, Redwood Building, Cardiff University, King Edward VII Avenue, Cardiff, CF10 3XF, UK.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Lavignac
authors.forename: Michelle
authors.initials: M
authors.lastname: Lazenby
authors.forename: Peli
authors.initials: P
authors.lastname: Foka
authors.forename: Beatrice
authors.initials: B
authors.lastname: Malgesini
authors.forename: Ilario
authors.initials: I
authors.lastname: Verpilio
authors.forename: Paolo
authors.initials: P
authors.lastname: Ferruti
authors.forename: Ruth
authors.initials: R
authors.lastname: Duncan
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D004337:Drug Carriers / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008546:Melanoma, Experimental; D051379:Mice; D008956:Models, Chemical; D010940:Plant Proteins / Q000737:chemistry; D011073:Polyamines / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D054789:Ribosome Inactivating Proteins, Type 1; D013696:Temperature; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology
chemical_list: D001672:Biocompatible Materials; D004337:Drug Carriers; D010940:Plant Proteins; D011073:Polyamines; D011108:Polymers; D054789:Ribosome Inactivating Proteins, Type 1; D013778:Tetrazolium Salts; D013844:Thiazoles; C025674:GEL protein, Gelonium multiflorum; C022616:thiazolyl blue