Keisaku Okada

Novel biodegradable lipid nano complex for siRNA delivery significantly improving the chemosensitivity of human colon cancer stem cells to paclitaxel.

BACKGROUND Targeting of a specific subset of cells is mandatory for the successful application of siRNA mediated silencing in anticancer therapy. A recent theory suggests that colon cancer is sustained by a small subpopulation of cells, termed cancer stem cells (CSCs). These cells are characterized by their innate drug resistance properties, which is one of the key factors of chemotherapy failure. The goal of this study was to assess whether a novel siRNA delivery carrier, with an appropriate siRNA, targeted to CD133+ cells has the potential to improve the efficacy of conventional chemotherapy. METHODS In this study, a novel synthetic siRNA carrier platform was designed and synthesized. This carrier was composed of a cationic oligomer (PEI(1200)), a hydrophilic polymer (polyethylene glycol) and a biodegradable lipid-based crosslinking moiety. Libraries of polymers were synthesized by varying their lipid composition. Their transfection efficacy was evaluated in vitro using CHOK1 cells. The polymer was characterized using molecular weight, particle encapsulation assay, particle size and surface charge analysis. RESULTS It was demonstrated that the lipid composition in the polymer plays a critical role in transfection. Optimizing the physicochemical properties of the polymers is crucial in achieving favorable knockdown. Lipid nano complex with composition PEI-Lipid(1:16) was the optimum ratio for gene silencing. Additionally, silencing of multidrug resistance gene (MDR1) and treatment with paclitaxel play a synergistic role in increasing the efficacy as compared to the drug alone. CONCLUSIONS In the present study a novel siRNA delivery carrier system with an MDR1-targeting siRNA (siMDR1) effectively reduced the expression of MDR1 in human colon CSCs (CD133+ enriched cell population), resulting in significantly increasing the chemosensitivity to paclitaxel.

A targeting approach for delivery of polymer microparticle-antibody conjugate against Vibrio parahaemolyticus-induced cytotoxicity to human intestinal epithelial cells

A major traditional of antibacterial drugs is antibiotic which promotes more rapid release of the toxins from bacteria cells in human body, which causes severe infection. The thermostable direct hemolysin (TDH) has been proposed as a major virulence factor of Vibrio parahaemolyticus (Vp). This study covers the preparation of polymer microparticle-antibody conjugate for the development of a drug targeting approach for antibacterial drug delivery. The chemical binding of antibodies (ab) to latex bead of 0.2 μm diameter was performed by using a water-soluble carbodiimide technique. Confocal microscopy revealed that the bacteria were strongly absorbed by the latex beads with bound anti-Vp polyclonal antibody (pAb). Treatment with a latex bead bound both anti-Vp pAb and anti-TDH monoclonal antibody (mAb) significantly inhibited bacterial adherence to the Caco-2 cells (p < 0.01), and reduced TDH-induced cytotoxicity in histology. These preliminary results suggest that it may be possible to effectively protect against Vp infection by using this microparticle-antibody conjugate delivery system.