Linear cyclen-based polyamine (LCPA, M(w) = 7392, M(w)/M(n) = 1.19) as a novel non-viral gene vector was designed and synthesized from 1,7-diprotected 1,4,7,10-tetraazacyclododecane (cyclen), bis(beta-hydroxylethyl)amine and epichlorohydrin. Agarose gel retardation and fluorescent titration using ethidium bromide showed the good DNA-binding ability of LCPA. It could retard pDNA at an N/P ratio of 4 and form polyplexes with sizes around 250-300 nm from an N/P ratio of 10 to 60 and relatively lower zeta-potential values (< +3 mV) even at the N/P ratio of 60. The cytotoxicity of LCPA assayed by MTT is much lower than that of 25 kDa PEI. In vitro transfection against A549 and 293 cells showed that the transfection efficiency of LCPA/DNA polyplexes is close to that of 25 kDa PEI at an N/P ratio of 10-15, indicating that the new material could be a promising non-viral polycationic reagent for gene delivery.

Merrifield resin-supported cyclen (MRC) was directly prepared by attaching 1, 4, 7, 10-tetraazacyclododecane (cyclen) to Merrifield resin (MR). Subsequent coordination with Cu(II), Co(II), and Ni(II) gave immobilized cyclen complex MRC-Cu, MRC-Co, and MRC-Ni as ''solid artificial enzymes.'' These complexes were characterized by elemental analysis, IR spectroscopy, ICP-AES, and scanning electron microscopy (SEM). Furthermore, the DNA cleavage activities of these complexes were investigated by agarose gel electrophoresis.The results indicated that MRC-Cu was superior to other solid artificial enzymes, and the cleavage process was carried out via oxidative pathway. Moreover, the solid catalyst MRC-Cu was very stable and it could be reused at least four times without any loss of catalytic activity.

This study provided an experimental evidence for the use of cyclen (1, 4, 7, 10-tetraazacyclododecane)-based polymer for gene delivery. The interesting interaction of the polymer with plasmid DNA was studied by using fluorescence titration, circular dichroism spectra, agarose gel electrophoresis and atomic force microscopy. It was found that polyplex was formed between the polycation and plasmid DNA. The results demonstrated that the cyclen-based polymer could act as non-viral gene vector with relatively low cytotoxicity.

A novel cyclen-based linear polyamine (POGEC) was designed and synthesized from the reaction between 1,3-propanediol diglycidyl ether and 1,7-bis(diethoxyphosphory)-1,4,7,10-tetraazacyclod-odecane. High-affinity binding between POGEC and DNA was demonstrated by agarose gel electrophoresis and scanning electron microscopy (SEM). Moreover, the formed POGEC/DNA complex (termed polyplex) could be disassociated to release the free DNA through addition of the physiological concentration of NaCl solution. Fluorescence spectrum was used to measure the high-affinity binding and DNA condensation capability of POGEC. Circular dichroism (CD) spectrum indicates that the DNA conformation did not change after binding to POEGC.

Mass spectra (GC/MS) were recorded on an Agilent Tecnologies 6890-5973N mass spectrometer. 1 H NMR (400.00 MHz) and 13 C NMR (100.00 MHz) spectra were recorded on a Bruker DMX 400 spectrometer operating at room temperature in CDCl 3. For TLC plates coated with silica gel were run in petroleum ether / ethyl acetate mixture and spots were developed in Ultraviolet and I 2. Representative preparation of mono-substituted TosMIC: 1-bromobutane 5a (0.206g, 1.5mmol) was added to the mixture of TosMIC 4 (0.195g, 1mmol) , K 2 CO 3 (0.414g, 3mmol) and [bmIm]Br (2.5mL), after vigorous stirring 12 hours at room temperature, the mixture was poured into 10 mL water, and was extracted with diethyl ether (3×10mL), the combined organics were washed with water and brine. The organic phase was dried over Na 2 SO 4 , and concentrated in vacuum. The crude product was purified by chromatography on silica gel (petroleum ether : ethyl acetate 4 : 1) to provide pure 1-(1-isocyanopentylsulfonyl)-4-methylbenzene 2a (95 %). Representative preparation of 4,5-disubstituted oxazoles: 1-bromobutane 5a (0.206g, 1.5mmol) was added to the mixture of TosMIC 4 (0.195g, 1mmol) , K 2 CO 3 (0.414g, 3mmol) and [bmIm]Br (2.5mL), after vigorous stirring 12 hours at room temperature, the TosMIC 4 was consumed, benzaldehyde 6a (0.127g, 1.2mmol) was added, about 10 hours stirring, the mixture was poured into 10 mL water, and was extracted with diethyl ether (3×10mL), the combined organics were washed with water and brine. The organic phase was dried over Na 2 SO 4 , and concentrated in vacuum. The crude product was purified by chromatography on silica gel (petroleum ether : ethyl acetate 10 : 1) to provide pure 4-butyl-5-phenyloxazole 7a (85 %).