Novel siRNA delivery system targeting β-catenin in colorectal cancer Cells: Synergistic effect with 5-fluorouracil

Short interference RNA (siRNA) has emerged as a promising approach for the treatment of many diseases that require controlling protein expression such as cancer. Effective delivery of siRNA into cells is a challenge. This project aimed to develop a guided delivery system based on multi-walled carbon nanotubes (MWCNTs) that can deliver siRNA preferentially into colorectal cancer (CRC) cells (Caco-2) to knock down β-catenin. MWCNTs were functionalized with a tetra-amine linker to load siRNA (f-MWCNTs (8)), which was in the next stage functionalized with mannose sugar as a targeting agent (f-MWCNTs (12)). Loads of amine on f-MWCNTs (8) and f-MWCNTs (12) were 12.7 × 10³ and 40 × 10³ nmol/mg respectively. The amount of loaded mannose in f-MWCNTs (12) was 1.109 μg/mg. The optimum N/P ratio for loading siRNA was 5:1 for the f-MWCNTs (8) and 15:1 for the f-MWCNTs (12). siRNA-f-MWCNTs (8) knocked down β-catenin protein by about 20 % and reduced the cell viability by about 10 %, while siRNA-f-MWCNTs (12) knocked down β-catenin protein by 50 % and reduced the cell viability by 32 %. A combination of siRNA-f-MWCNTs (12) with the anticancer drug 5-fluorouracil (5-FU) reduced the cell viability by around 80 % compared to 25 % by monotherapy with 5-FU, while the combination with f-MWCNTs (8) did not show a significant effect. In conclusion, the functionalization of MWCNT with mannose increases the efficiency of siRNA delivery into Caco-2 cells and the knockdown of β-catenin can improve the sensitivity of Caco-2 cells to 5-FU.