Journal of Applied Polymer Science, Vol.103, No.5, 3064-3075, 2007
Cholesteryl moiety terminated amphiphilic polymethacrylates containing nucleic acid bases for drug delivery
Poly[9-(2-methacryloyloxyethyl)adenine] and poly[1-(2-methacryloyloxyethyl)thymine] with one pendant cholesteryl moiety at the polymer end (PMEA-Chol, PMET-Chol) and with two pendant cholesteryl moieties at both polymer ends as terminal groups (PMEA-2Chol, PMET-2Chol) were prepared by radical polymerization of 9-(2-methacryloyl-oxyethyl)adenine (MEA) and 1-(2-methacryloyloxyethyl)thymine (MET) initiated with 4,4'-azobis[(3-cholesteryl)4-cyanopentanoate] in the presence of 2-mercaptoethanol or thiocholesterol as chain transfer reagents, respectively. The copolymers [PNiPAAm-co-PMEA-nChol (n = 1,2)] composed of N-isopropylacrylamide (NiPAAm) and MEA were also prepared in a similar manner. The self-organization of these polymers and copolymers was confirmed by a fluorescence measurement, and then their critical concentrations of micelle formation (CMC) were determined. The mixture of PMEA-2Chol and cholesterol as a lipophilic drug model formed a lamella type of complex with an interplaner spacing of d = 35.3 angstrom. The hypochromism based on the formation of a 1 : I interaction of adenine and thymine moieties was found to appear in the mixed aqueous solution of PMEA-Chol and PMET-Chol. Complementary interactions were also confirmed in the system of PMET-2Chol and adenosine as well as PMEA-2Chol and uridine. Cis-dichlorodiammine platinum(II) (CDDP) was bound to PNiPAAm-co-PMEA-Chol through the adenine moiety by ligand substitution atoms of CDDP. The amount of CDDP loaded on the copolymer was found to be 0.143 g g(-1). (c) 2006 Wiley Periodicals, Inc.
Keywords:adenine;thymine;radical polymerization;polymethacrylates;cholesteryl moiety;self-organization;hydrophobic interaction;hypochromism;CDDP;DDS