Efficacy of photodynamic therapy using TiO2 nanoparticles doped with Zn and hypericin in the treatment of cutaneous Leishmaniasis caused by Leishmania amazonensis.

Since Leishmania parasites exhibit resistance outbreaks to drugs conventionally used in medical treatments, research of new antileishmanial compounds or alternative treatment therapies are essential. A focus of interest has been the implementation of light-based therapies such as photodynamic therapy, where inorganic compounds such as titanium dioxide have shown promising results as drug delivery carriers. In this work, nanoparticles of TiO2 doped with Zn (TiO2/Zn) were synthesized through solution combustion route and with hypericin (HY) in order to enhance its photodynamic activity in the visible light region. Scanning (SEM) and transmission (TEM) electron microscopy analyses showed particles of (TiO2/Zn) with sizes smaller than 20 nm and formation of aggregates smaller than 1 µm, whilst electron diffraction spectroscopy (EDS) analysis ensured the presence of Zn in the system. The association of the TiO2/Zn with HY (TiO2/Zn-HY) was further confirmed by fluorescence spectrometry. Measurements of its cellular uptake showed the presence of smaller molecules into promastigotes after 120 min incubation. TiO2/Zn-HY showed good antileishmanial activity (EC50 of 17.5 ± 0.2 µg mL-1) and low cytotoxicity against murine macrophages (CC50 35.2 ± 0.3 µg mL-1) in the visible light (22 mW cm-2; 52.8 J cm-2). Moreover, in the in vivo analysis, TiO2/Zn-HY decreased the parasite load of L. amazonensis - BALB/c infected mice by 43% - 58% after a combination of blue and red light presenting 22 mW cm-2 of intensity and 52.8 J cm-2 of fluency delivered. All together, these data indicate a new combined system of nanoparticles associated with a photosensitizer and PDT as alternative to amphotericin B for the treatment of cutaneous leishmaniasis.

N, N', N″-trisubstituted guanidines: Synthesis, characterization and evaluation of their leishmanicidal activity.

Leishmaniasis is a group of diseases caused by protozoan parasites from the genus Leishmania. There are estimated 1.3 million new cases annually with a mortality of 20,000-30,000 per year, when patients are left untreated. Current chemotherapeutic drugs available present high toxicity and low efficacy, the latter mainly due to the emergence of drug-resistant parasites, which makes discovery of novel, safe, and efficacious antileishmanial drugs mandatory. The present work reports the synthesis, characterization by ESI-MS, 1H and 13C NMR, and FTIR techniques as well as in vitro and in vivo evaluation of leishmanicidal activity of guanidines derivatives presenting lower toxicity. Among ten investigated compounds, all being guanidines containing a benzoyl, a benzyl, and a substituted phenyl moiety, LQOF-G2 (IC50-ama 5.6 µM; SI = 131.8) and LQOF-G7 (IC50-ama 7.1 µM; SI = 87.1) were the most active against L. amazonensis intracellular amastigote, showing low cytotoxicity to the host cells according to their selectivity index. The most promising compound, LQOF-G2, was further evaluated in an in vivo model and was able to decrease 60% of the parasite load in foot lesions at a dose of 0.25 mg/kg/day. Moreover, this guanidine derivative demonstrated reduced hepatotoxicity compared to other leishmanicidal compounds and did not show nephrotoxicity, as determined by the analyses of biomarkers of hepatic damage and renal function, which make this compound a potential new hit for therapy against leishmaniasis.