Poly(amido amine)s as gene delivery vectors: effects of quaternary nicotinamide moieties in the side chains.
To evaluate the effect of quaternary nicotinamide pendant groups on gene delivery properties, a series of poly(amido amine) (co)polymers were synthesized by Michael addition polymerization of N, N'-cystaminebisacrylamide with variable ratios of 1-(4-aminobutyl)-3-carbamoylpyridinium (Nic-BuNH(2)), and tert-butyl-4-aminobutyl carbamate (BocNH-BuNH(2)), yielding poly(amido amine)s (NicX-NHBoc) with X=0, 10, 30, and 50 % of quaternary nicotinamide groups in the polymer side chains. Deprotection of the pendant Boc-NH groups afforded an analogous series of polymers (NicX-NH(2)) with higher charge density (due to the presence of protonated primary amino groups in the side chains) and subsequent acetylation yielded a series of polymers (NicX-NHAc) of lower hydrophobicity than the Boc-protected polymers. The polymers with the Boc-protected or the acetylated amino groups showed high buffer capacity in the range pH 5.1-7.4, which is a property that can contribute to endosomal escape of polyplexes. The presence of quaternary nicotinamide groups has distinct beneficial effects on the gene vector properties of these polymers. The polymers containing >or=30 % of quaternary nicotinamide groups in their side chains condense DNA into small, nanosized particles (<or=200 nm) with positive surface charge (>or=+15 mV). Fluorescence experiments using ethidium bromide as a competitor showed that the quaternary nicotinamide groups intercalate with DNA, contributing to a more intimate polymer-DNA binding and shielding. Polyplexes of nicotinamide-functionalized poly(amido amine)s NicX-NHBoc and NicX-NHAc, formed at 12/1 polymerDNA mass ratio, efficiently transfect COS-7 cells with efficacies up to four times higher than that of PEI (Exgen 500), and with essentially absence of cytotoxicity. NicX-NH(2) polymers, possessing protonated primary amino groups in their side chains, have a higher cytotoxicity profile under these conditions, but at lower 3/1 polymer-DNA mass ratio also these polymers are capable of efficient transfection, while retaining full cell viability.
Mateos-Timoneda
Miguel A
MA
Department of Biomedical Chemistry and Department of Polymer Chemistry and Biomaterials, Institute for Biomedical Technology (BMTI), Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
Lok
Martin C
MC
Hennink
Wim E
WE
Feijen
Jan
J
Engbersen
Johan F J
JF
D000818:Animals; D019556:COS Cells; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002522:Chlorocebus aethiops; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004996:Ethidium / Q000737:chemistry; D018014:Gene Transfer Techniques; D007364:Intercalating Agents / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D053758:Nanoparticles / Q000737:chemistry; D009536:Niacinamide / Q000737:chemistry / Q000494:pharmacology*; D011073:Polyamines / Q000737:chemistry / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence; D055672:Static Electricity; D014162:Transfection
D007364:Intercalating Agents; D011073:Polyamines; D009536:Niacinamide; D004247:DNA; D004996:Ethidium