Solution-combustion synthesis of doped TiO2 compounds and its potential antileishmanial activity mediated by photodynamic therapy.

Photodynamic therapy has emerged as an alternative treatment for cutaneous leishmaniasis, and compounds with photocatalytic behavior are promising candidates to develop new therapeutic strategies for the treatment of this parasitic disease. Titanium dioxide TiO2 is a semiconductor ceramic material that shows excellent photocatalytic and antimicrobial activity under Ultraviolet irradiation. Due to the harmful effects of UV radiation, many efforts have been made in order to enhance both photocatalytic and antimicrobial properties of TiO2 in the visible region of the spectrum by doping or through modifications in the route of synthesis. Herein, Fe-, Zn-, or Pt- doped TiO2 nanostructures were synthesized by solution-combustion route. The obtained compounds presented aggregates of 100 nm, formed by particles smaller than 20 nm. Doping compounds shift the absorption spectrum towards the visible region, allowing production of reactive oxygen species in the presence of oxygen and molecular water when the system is irradiated in the visible spectrum. The Pt (EC50 = 18.2 ±â€¯0.8 µg/mL) and Zn (EC50 = 16.4 ±â€¯0.3 µg/mL) -doped TiO2 presented the higher antileishmanial activities under visible irradiation and their application as photosensitizers in photodynamic therapy (PDT) strategies for the treatment of cutaneous leishmaniasis should be considered.

Synthesis of calcium phosphate nanostructures by combustion in solution as a potential encapsulant system of drugs with photodynamic properties for the treatment of cutaneous leishmaniasis.

The traditional drugs used in the treatment of cutaneous leishmanisis (CL) have multiple disadvantages, such as high toxicity, high costs, and more recently the appearance of parasites resistant to those drugs. For this reason, some research has focused on the development of new drugs or treatment therapies. Photodynamic therapy (PDT) that involves the use of a photosensitive or photosensitizing compound capable of producing reactive oxygen species to which Leishmania parasites are sensitive, has emerged as an alternative for the treatment of CL. However, some of these sensitizing compounds exhibit some toxicity (cytotoxicity, allergic reaction, etc), low selectivity, and some of them are insoluble in aqueous media limiting their use. Therefore, the PDT can be improved using encapsulation systems which protect drugs, prevent their degradation, help them overcome physical barriers and increase their selectivity. In this study, we propose the use of calcium phosphate as a potential encapsulant or photodynamic support for photoactive drugs, using hypericin (HY) as a photosensitizer agent. The self-combustion route was used to synthesize the CP nanostructures. The structure and morphology of CP nanoparticles were evaluated via X-ray diffraction (XRD), Raman and field-emission scanning electron microscopy (FE-SEM). Phases rich in hydroxyapatite and CP ß phase, with granular morphology and an average grain size of 42.9 nm were obtained. The encapsulation uptake and the interactions between HY and the encapsulated system were evaluated by fluorescence spectroscopy and Fourier-transform infrared spectroscopy (FTIR), respectively. Approximately 13% of HY was enapsulated per 1 µg of nanoparticles of calcium phosphate. Composites were submitted to in vitro assays of cytotoxicity and anti-leishmanial activity. The CP nanoparticles did not affect the photodynamic activity of HY. On the contrary they showed antileishmanial response.