Hypericin photodynamic activity. Part III: in vitro evaluation in different nanocarriers against trypomastigotes of Trypanosoma cruzi

Abstract

Chagas is a parasitic endemic disease caused by the protozoan Trypanosoma cruzi. It represents a strong threat to public health due to its strong resistance against commonly available drugs. We studied the in vitro ability to inactivate the trypomastigote form of this parasite using photodynamic inactivation of microorganisms (or antimicrobial Photodynamic Therapy, aPDT). For this, we chose to use the photosensitizer hypericin (Hyp) formulated in ethanol/water (1% v/v) and Hyp loaded in the dispersion of different aqueous nanocarrier systems. These included polymeric micelles of F-127 and P-123 (both Pluronic™ surfactants), and liposomal vesicles of phospholipid 2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). These systems with Hyp had their activity compared against trypomastigote forms under light and in the dark. Hyp revealed a high level of effectiveness to eradicate protozoa in vitro. Samples at concentrations higher than 0.8 μmol L⁻¹ of Hyp in Pluronic micelles showed efficacy even in the dark, with the EC₅₀ around (6–8) μmol L⁻¹. Therefore, Hyp/Pluronics can be used also as a chemotherapeutic agent. The best result for EC₅₀ is at approximately 0.31 μmol L⁻¹ for illuminated systems of Hyp in F-127 micelles. For Hyp in P-123 micelles under light, the results also led to a low EC₅₀ value of 0.36 μmol L⁻¹. The highest value of EC₅₀ was 2.22 μmol L⁻¹, which was found for Hyp/DPPC liposomes under light. For the Hyp-free (ethanol/water, 1% v/v)/illuminated group, the EC₅₀ value was 0.37 μmol L⁻¹, which also is a value that shows effectiveness. However, in free-form, Hyp is not protected against blood components, unlike when Hyp is loaded into the nanocarriers.