Response surface method optimization of a novel Hypericin formulation in P123 micelles for colorectal cancer and antimicrobial photodynamic therapy

The photodynamic properties of Hypericin (Hyp) may be used as an alternative treatment for malignancies of the lower gastrointestinal tract and for the prevention of surgical-site infection; however, its use in photodynamic therapy has been limited because of its poor hydrosolubility. Therefore, in order to improve its water solubility and its photodynamic effect, Hyp was encapsulated in Pluronic P123 (P123) and the photodynamic effects against intestinal and epidermal bacteria and against two lineages of intestinal colon carcinoma cells were investigated. Two response surface methods (RSM) were used to achieve the best in vitro photodynamic activity against Enterococcus faecalis, Escherichia coil and Staphylococcus nitrous: in the first (full 2(3) RSM), Hyp concentration (HC*), incubation time (IT*) and LED-light time (LT*) were considered as the independent variables and E. faecalis inhibition as the dependent variable. In the second (full 3(2) RSM), Hyp concentration (HC*) and P123 concentration (CC*) were considered as independent variables and E. faecalis, E. coli and S. aureus inhibition as dependent variables. The optimized experimental conditions achieved were: Hyp concentration = 37.5 mu mol/L; P123 concentration = 21.5 mu mol/L and 6.3 J/cm(2), which resulted in 2.86 +/- 0.12 and 2.30 +/- 0.31 CFU log-reductions of E. faecalis and S. aureus. No effect was seen against E. coli. The cytotoxic effects of Hyp/P123 were also investigated for Caco-2 and HT-29 intestinal colon carcinoma cells at Hyp/P123 concentrations of 1, 0.5, 0.25 and 0.1 mu mol/L for Caco-2 cells and 4, 3, 2 and 1 mu mol/L for HT 29 cells. The cytotoxic concentrations for 50% (CC50) and 90% (CC90) of Hyp/P123 were 0.443 and 0.870 mu mol/L for Caco-2 cells and 1.4 and 2.84 mu mol/L for HT-29 cells. The P123 nanocarrier played a significant role in the permeation of Hyp through the cell membrane leading to significant cell death, and showed itself to be a promising photosensitizer for PDT that could be suitable for the treatment of colonic diseases since it is effective against positive Gram bacteria and intestinal colon carcinoma cells.