Polymerized spermine as a novel polycationic nucleic acid carrier system.

Spermine, an endogenous amino-group bearing monomer that condenses DNA in sperm, was used as the basic building block to form polycationic nucleic acid carriers via condensation with one of three linker molecules - bischloroformate, succinyl chloride, and glyoxal. The three cationic polymers, polyspermine carbamate (PSP-Carb), polyspermine amide (PSP-Amide) and polyspermine imine (PSP-Imine) were examined for their degradability, cytotoxicity, ability to condense nucleic acids to nanoparticles, and ability to transfect genes or siRNA to cells. PSP-Carb and PSP-Amide exhibited a half-life of more than 2 months when incubated in aqueous buffers at 37°C, while the half-life of PSP-Imine was 11h.

Hydrothermal synthesis of a highly sensitive T2-weigthed MRI contrast agent: zinc-doped superparamagnetic iron oxide nanocrystals.

A highly efficient hydrothermal strategy for the synthesis of zinc-doped superparamagnetic iron oxide nanocrystals (SPION:Zn) with lower toxicity and improved sensitivity has been demonstrated. The saturation magnetizations of as-synthesized SPION:Zn were demonstrated to be Zn-dependent and could be tuned from 41.88 emu/g to 79.

Novel poly(ethylene imine) biscarbamate conjugate as an efficient and nontoxic gene delivery system.

We report a novel poly(ethylene imine) biscarbamate conjugate (PEIC) with a low molecular weight (M(W) = 2800, M(n) = 910), and low cytotoxicity which has orders of magnitude higher luciferase gene transfection activity at its optimal conditions as compared with poly(ethylene imines) (PEIs) of M(W) 2000 or 25,000. This polycationic gene carrier was synthesized by reacting low molecular weight PEI (M(W) = 800) with 1,4-Butanediol bis(chloroformate) to give a copolymer with biodegradable carbamate linkages. When added to a DNA solution, PEIC condensed DNA at a w/w ratio above 1 to form 53-91 nm polyplexes with 20-24 mV in zeta potential (about half of that of branched 25kDa PEI).