Abstract
We report on the synthesis of star copolymers possessing dual functions of gene delivery vectors and magnetic resonance (MR) imaging contrast enhancement. Starting from asymmetrically functionalized β-cyclodextrin (β-CD) comprising 7 azide moieties and 14 α-bromopropionate functionalities at the upper and lower rim of a rigid toroidal β-CD core, (DOTA-Gd)7-CD-(PDMA)14 star copolymers were synthesized via atom transfer radical polymerization (ATRP) of N,N-dimethylaminoethyl methacrylate (DMA) and subsequent click reaction with an alkynyl-functionalized gadolinium (Gd3+) complex, DOTA-Gd, where DOTA is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid. The obtained Janus-type star copolymers, (DOTA-Gd)7-CD-(PDMA)14, could completely complex with anionic plasmid DNA (pDNA) via electrostatic interactions at N/P ratios equal to or higher than 2 and exhibit optimal in vitro transfection efficiency at an N/P ratio of 8. In addition, in vitro MR imaging experiments demonstrated considerably enhanced T1 relaxivity (r1 ∼ 10.9 s−1 mM−1) for the star copolymer compared to that of commercially available small molecular MR imaging contrast agents (2.4–3.2 s−1 mM−1). The star-type topology of asymmetrically functionalized β-CD based copolymers in combination with the integrated design of diagnostic and therapeutic functions augurs well for their potential applications in the field of image-guided gene therapy.
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