OBJECTIVETo investigate the effects of the small interfering RNA plasmid-dextran magnetic nanoparticles (siRNA-DMN) combination with external magnetic fields on silencing survivin gene expression of bladder cancer cells and apoptosis when DMN used as gene carrier to transfer siRNA-survivin recombinant plasmid in vivo.

METHODSThe siRNA-survivin recombinant plasmid specific targeted survivin was synthesized in previous experiment. DMN were prepared by chemical coprecipitation method and used as gene carrier. The siRNA-DMN were constructed by static electricity of polylysine and transferred into human bladder cancer BIU-87 cells with the help of external magnetic fields. The growth inhibiting rate (IR) of BIU-87 cells was observed by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyl tetrazolium bromide's test and the apoptosis index (AI) was detected by transferase-mediated dUTP nick end labeling method. The relatively transcription levels of survivin mRNA and protein expression were respectively detected by semi-quantitive reverse transcription polymerase chain reaction and Western Blotting techniques.

RESULTSThe diameter, effective diameter and saturation magnetization of DMN-siRNA were about 10 - 12 nm, 94.8 nm and 0.19 emu/g, respectively. The IR (39.60%) and AI (28.72%), the relative expression of survivin mRNA and protein of siRNA-DMN combination with external magnetic fields on BIU-87 cells were significantly higher and lower than those in the control group and single siRNA-DMN group, respectively (P < 0.05).

CONCLUSIONSThe siRNA-survivin plasmid-DMN combination with external magnetic fields could effectively inhibit survivin expression and induce BIU-87 cells apoptosis which provided experimental basis for the magnetic targeting gene therapy of bladder tumor.