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Abstract: A family of bioreducible poly(disulfide amine)s, which differ in the length of polymethylene spacer [–(CH2) n –] in the main chain and the side chain, has been synthesized. These bioreducible poly(disulfide amine)s exhibit local environment specific degradability and are associated with lower cytotoxicity than branched poly(ethylenimine) (bPEI, 25kDa). These cationic polymers also show higher buffering capacity and protonation degree than bPEI, facilitating the endosomal escape of carried genetic materials. The transfection efficiency of these agents is oligomethylene length dependent. Poly(cystaminebisacrylamide-spermine) [poly(CBA-SP)], poly(cystaminebisacrylamide-bis(3-aminopropyl)-1,3-propanediamine) [poly(CBA-APPD)], and poly(cyxtaminebisacrylamide-bis(3-aminopropyl)-ethylenediamine) [ploy(CBA-APED)] with longer propylene [–(CH2)3–] side spacer, demonstrate higher transfection efficacy than the counterpart poly(cystaminebisacrylamide-bis(2-aminoethyl)-1,3-propanediamine) [poly(CBA-AEPD)] and poly(cystaminebisacrylamide-triethylenetetramine) [poly(CBA-TETA)], which have shorter ethylene [–(CH2)2–] side spacer. The poly(CBA-SP), poly(CBA-APPD), poly(CBA-APED) with the main chain spacer of –(CH2)4–, –(CH2)3–, –(CH2)2– demonstrate similar transfection efficiency, indicating the length of polymer main chain spacer has less influence on transfection efficiency. However, with the same short ethylene [–(CH2)2–] side spacer, poly(CBA-AEPD), with the longer main chain oligomethylene units [–(CH2)3–], showed relatively higher transfection efficiency than poly(CBA-TETA), having shorter main chain oligomethylene units [–(CH2)2–]. Of these polymeric carriers, poly(CBA-SP) demonstrated the highest transfection in the C2C12 cell line, while poly(CBA-APED) showed the highest transfection in the HeLa cell line. All of these agents showed greater transfection activity than commercialized bPEI 25kDa. The poly(disulfide amine)s are promising safe and efficient non-viral vectors for gene delivery. [Copyright &y& Elsevier]

Abstract: Arginine-grafted bioreducible poly(disulfide amine) (ABP) polymer was synthesized for non-viral gene delivery systems. Its Mw was measured to be 4.45×103 Da/mole by FPLC-SEC and its PDI value was 1.49. ABP was able to retard pDNA from a weight ratio of 2 but ABP could not retard pDNA even at a weight ratio of 10 in the presence of DTT, showing that it can be biodegraded in reducing environment such as cytoplasm. ABP was examined to form positively charged nano-sized particles (<200nm) with pDNA. ABP showed no significant cytotoxicity and greatly enhanced transfection efficiency in comparison with unmodified poly(cystaminebisacrylamide-diaminohexane) (poly(CBA-DAH)) and PEI25k in mammalian cells. The transfection efficiency of ABP was not much reduced even in the serum condition. Chloroquine treatment was not found to improve the transfection efficiency of ABP. The cellular uptake pattern of ABP polyplexes was almost similar with poly(CBA-DAH), suggesting that greatly enhanced transfection efficiency of ABP is not induced by its high cellular penetrating ability but may be mediated by other factors such as good nuclear localization ability. [Copyright &y& Elsevier]

Abstract: Implantation of skeletal myoblasts to the heart has been investigated as a means to regenerate and protect the myocardium from damage after myocardial infarction. While several animal studies utilizing skeletal myoblasts have reported positive findings, results from clinical studies have been mixed. In this study we utilize a newly developed bioreducible polymer system to transfect skeletal myoblasts with a plasmid encoding vascular endothelial growth factor (VEGF) prior to implantation into acutely ischemic myocardium. VEGF has been demonstrated to promote revascularization of the myocardium following myocardial infarction. We report that implanting VEGF expressing skeletal myoblasts into acutely ischemic myocardium produces superior results compared to implantation of untransfected skeletal myoblasts. Skeletal myoblasts expressing secreted VEGF were able to restore cardiac function to non-diseased levels as measured by ejection fraction, to limit remodeling of the heart chamber as measured by end systolic and diastolic volumes, and to prevent myocardial wall thinning. Additionally, arteriole and capillary formation, retention of viable cardiomyocytes, and prevention of apoptosis was significantly improved by VEGF expressing skeletal myoblasts compared to untransfected myoblasts. This work demonstrates the feasibility of using bioreducible cationic polymers to create engineered skeletal myoblasts to treat acutely ischemic myocardium. [ABSTRACT FROM AUTHOR]

Abstract: A cardiomyocyte-targeted Fas siRNA delivery system was developed using prostaglandin E2 (PGE2)-modified siRNA polyplexes formed by a reducible poly(amido amine) to inhibit cardiomyocyte apoptosis. PGE2, which was used as a specific ligand for cardiomyocyte targeting, was conjugated to the terminal-end of the sense siRNA (PGE2-siRNA). The reducible cationic copolymer, synthesized via Michael-type polyaddition of 1,6-diaminohexane and cystamine bis-acrylamide (poly(DAH/CBA)), tightly condensed the PGE2-siRNA conjugate to form nanosize polyplexes having a diameter of 100–150nm. The PGE2-siRNA/poly(DAH/CBA) polyplexes decomplexed to release PGE2-siRNA in a cytosolic reducing environment due to the degradation of the reducible poly(DAH/CBA). The cellular uptake of the PGE2-siRNA/poly(DAH/CBA) polyplex was increased in rat cardiomyocytes (H9C2 cells) due to PGE2 receptor-mediated endocytosis. When H9C2 cells were transfected with siRNA against Fas, a key regulator of ischemia-induced apoptosis, the PGE2–Fas siRNA/poly(DAH/CBA) polyplex delivery system led to a significant increase in Fas gene silencing, resulting in inhibition of cardiomyocyte apoptosis. The PGE2–Fas siRNA/poly(DAH/CBA) polyplex did not induce interferon-alpha in peripheral blood mononuclear cells. These results suggest that the PGE2–Fas siRNA/poly(DAH/CBA) polyplex formulation may be clinically applicable as a cardiomyocyte-targeted Fas siRNA delivery system to inhibit apoptosis in cardiovascular disease. [Copyright &y& Elsevier]