Nanoformulation of enzymes using various imaging probes and targeting agents such as nanoparticles improve their therapeutic impacts. In addition, considering some side effects and resistance against the conventional chemotherapeutic drugs in colon cancer therapy, we described a novel therapeutic NS including gold nanoparticles (GNPs) and bovine pancreatic ribonuclease (RNase A) against colon cancer, so-called RnaGNPs.

The physicochemical properties and cytotoxicity of RnaGNPs, as well as their effects on cellular uptake, cell cycling, apoptosis, invasion, and the expression of ERK1 and ERK2 genes of colon cancer SW-480 cells in-vitro, were evaluated. To determine the efficacy of RnaGNPs combined with the photothermal therapy (PTT), low doses of the near-infrared (NIR) laser irradiation in SW-480 cells were utilized.

From the flow cytometry results, the internalization of the RnaGNPs into the SW-480 cells was ≃ 90% and showed the significant cytotoxicity effect on cells. The IC50 value for RnaGNPs after 24, 48 and 72 h were obtained 182, 164, and 157 μg/mL, respectively. The RnaGNPs induced cell cycle arrest in the sub-G1 phase and a reduction in the G0/G1 and G2/M phases in SW-480 cells. Apoptosis assay using the FITC-labeled annexin V showed about 69.91% early and 5.04% late apoptosis in the treated cells. PTEN, Bax, and caspase 3 were upregulated, while AKT and Bcl-xL were downregulated, indicating the induction of apoptosis. The results of the cell invasion assay indicated that RnaGNPs significantly inhibited the migration and invasion of the treated cells, because of the downregulation of the ERK1/2 pathway. The combination of RnaGNPs with PTT decreased the IC50 value approximately to the half and significantly increased the impacts of RnaGNPs on the cancer cells.

Based on our findings, the engineered RnaGNPs are proposed as a promising nanoscaled modality for the combined enzyme therapy and PTT of solid tumors such as colon cancer.