A) Cell viability changes upon SN-38, NPM, SN-NPM with or without light. The HT-29 human colon cancer cells were incubated with different concentrations of SN38, SN-NPM, and comparable amounts of NPM as SN-NPM for 24 hours. Cells were treated with LED panel light (635 nm) for 2 minutes, and cell viability was measured 72 hours later with MTS assay. (*p<0.05) B) Combination index (CI) versus Fraction affected (Fa) plot.