Influence of polymer architecture on the structure of complexes formed by PEG-tertiary amine methacrylate copolymers and phosphorothioate oligonucleotide.
The influence of polymer structure on the characteristics of complexes of a phosphorothioate antisense oligonucleotide (ISIS 5132) was studied, using well-defined cationic copolymers based on 2-(dimethylamino) ethyl methacrylate (DMAEMA) and poly(ethylene glycol) (PEG). The three related copolymer structures were: DMAEMA-PEG (a diblock copolymer) DMAEMA-OEGMA 7 (a brush-type copolymer), DMAEMA-stat-PEGMA (a comb-type copolymer); each of these were examined together with DMAEMA homopolymer, which served as a control. The results revealed that all the polymers exhibited good binding ability with the oligonucleotide (ON). Interestingly, the comb-type polymer DMAEMA-stat-PEGMA demonstrated the highest binding ability and DMAEMA homopolymer the lowest, as judged by a dye displacement assay. DMAEMA homopolymer produced large agglomerates of smaller individual complexes as observed by optical density, photon correlation spectroscopy and transmission electron microscopy studies. In contrast, two PEG-block copolymers, DMAEMA-PEG and DMAEMA-OEGMA 7, formed compact complexes of 80-150 nm which had good long-term colloidal stability. This is attributed to the steric stabilisation effect of the PEG chains on the ON-copolymer complexes. These two copolymers are believed to form complexes with ON that have a micellar structure. Comb-type DMAEMA-stat-PEGMA copolymer formed highly soluble complexes with the ON that did not phase separate from the buffer solution. This study clearly demonstrates that varying the copolymer architecture allows access to a range of ON complexes. In vitro cytotoxicity experiments on HepG2 cells showed that all of the tertiary amine methacrylate copolymers displayed lower cytotoxicity than the control poly(L-lysine).
Deshpande
Mangesh C
MC
School of Pharmaceutical Sciences, Boots Research Institute, University of Nottingham, University Park, NG7 2RD, Nottingham, UK.
Garnett
Martin C
MC
Vamvakaki
M
M
Bailey
Lindsey
L
Armes
Steven P
SP
Stolnik
Snjezana
S
D000588:Amines / Q000737:chemistry* / Q000633:toxicity; D002412:Cations; D011232:Chemical Precipitation; D004587:Electrophoresis, Agar Gel; D004996:Ethidium / Q000737:chemistry; D008027:Light; D008689:Methacrylates / Q000737:chemistry* / Q000633:toxicity; D008854:Microscopy, Electron; D020319:Oligodeoxyribonucleotides, Antisense / Q000737:chemistry* / Q000633:toxicity / Q000648:ultrastructure; D011092:Polyethylene Glycols / Q000737:chemistry* / Q000633:toxicity; D011108:Polymers / Q000737:chemistry* / Q000633:toxicity; D012542:Scattering, Radiation; D013053:Spectrophotometry; D013873:Thionucleotides / Q000737:chemistry* / Q000633:toxicity; D017186:Titrimetry; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000588:Amines; D002412:Cations; D008689:Methacrylates; D020319:Oligodeoxyribonucleotides, Antisense; D011108:Polymers; D013873:Thionucleotides; D011092:Polyethylene Glycols; C099587:ISIS 5132; D004996:Ethidium; C049840:2-(dimethylamino)ethyl methacrylate