I tried to downregulate one protein expression in RAW264.7 Macrophage cell line using recommended RNAiMAX Lipofectamine, but not geting any good result. I tried different siRNA sequence already?
Have you optimized your transfection efficiciency by using a control siRNA, something targeting a housekeeping gene that you can reliably and reproducibly knock-down? Then you take those conditions and apply to your siRNA of choice. Working with optimized conditions will net you improved results.
try positive control siRNA first, to make sure delivery and the entire protocol including readout (eg qRT-PCR) works well. For instance GAPDH silencer select siRNA typically induces > 90% knockdown in all cell lines, when delivered with RNAiMax or Lipo 2000