Synthesis and characterisation of polyamine-poly(ethylene glycol) constructs for DNA binding and gene delivery

Improved non-viral vector systems are needed for efficient delivery of DNA to target cell nuclei in gene therapy. A series of linear polyamine-poly(et hylene glycol) (PEG) constructs has been synthesised by reaction of appropr iately Boc-protected thermine derivatives with omega-methoxyPEG oxiranylmet hyl ethers. Constructs carrying 1-3 MeOPEG units and 0, 2 or 4 N-methyl gro ups have been prepared by this method. H2N(CH2)(3)NBoc(CH2)(3)NBoc(CH2)(3)N HBoc was prepared efficiently by mono-trifluoroacetylation of thermine, att achment of Boc and removal of the trifluoroacetyl group in one pot. A simil ar process gave H2N(CH2)(3)NBoc(CH2)(3)NBoc(CH2)(3)NH2. BocMeN(CH2)(3)NHMe was alkylated by 1,3-dibromopropane to give BocMeN(CH2)(3)-NMe(CH2)(3)NMe(C H2)(3)NMeBoc. A cyanoethylation/reduction sequence extended H2N(CH2)(3)NBoc (CH2)(3)NBoc(CH2)(3)NH2 to give H2N(CH2)(3)NBoc(CH2)(3)NBoc(CH2)(3)NBoc(CH2 )(3)NBoc(CH2)(3)NH2, which was converted to its mono- and di-MeOPEG550 deri vatives. Deprotection gave the linear polyamine-MeOPEG constructs. A branch ed triamine-poly(ethylene glycol) construct was prepared by acylation of (B ocHN(CH2)(3))(2)N(CH2)(3)NH2 with omega-methoxyPEG 550 chloroformate, follo wed by deprotection. A cyanoethylation/reduction/protection sequence from ( H2N(CH2)(3))(2) N(CH2)(3)NHBoc gave a protected pentamine. Alkylation with Br(CH2)(5)CONH(CH2)(2)NHBoc, deprotection, acylation with MeOPEG chloroform ate and deprotection gave a pentamine-MeOPEG construct in which the MeOPEG is attached through a linker to the central amine. The linear hexamine cons truct carrying MeOPEG550 at only one terminus was the most effective DNA-in teractive member of the two series in an ethidium displacement assay and wa s effective in delivering a reporter gene to RIF-1 tumours. (C) 2000 Elsevi er Science Ltd. All rights reserved.