Targeting of antileishmanial drugs produced by nanotechnologies

Abstract

The aim of this work is to develop an effective new MGA delivery system by means of nanotechnology for the treatment of leishmaniosis which could be administered by parenteral or oral route in a future. Moreover, for ensuring the effectiveness of the formulations developed, their in vitro activities will be assessed against L. infantum. The intention is to prepare a target drug delivery system by means of different technological strategies like micro-nanoparticles by spray drying. These formulations should target the antileishmanial drug to the macrophages which are the host cells of Leishmania parasites. If this purpose was achieved the drug bioavaibility would be increased, therefore lower doses could be administered, reducing the side effects and improving the efficiency of the treatment. The main objective can be summarized as to develop and characterize a new MGA formulation using nanotechnologies. It implies: 1. To study in vitro the effectiveness and cytotoxicity of formulations against Leishmania. 2. To develop preliminary in vitro uptake studies in macrophages using quantum dots assisted imaging. 3. To study MGA release profile from the new delivery device developed. The present development of a new dosage form of MGA starts with the elaboration of emulsions, self-emulsifying drug delivery systems and nanosuspensions. However, the main part is centralized by the microencapsulation of MGA by spray drying using the preliminary studies as reference and the polymer chitosan as the main excipient. Spray drying technique has been used to elaborate two kinds of nano/microspheres, on one side those which come from emulsions and on the other side those which come from solutions. Both cases have been morphologically characterized and their effectiveness has been studied in vitro against Leishmania parasites. Moreover, the ability to be phagocyted by macrophages cells has been investigated using quantum dots assisted imaging in the Department of Pharmaceutical Sciences of the University of Connecticut during a stage. A new meglumine antimoniate delivery device for the treatment of leishmaniosis has been properly developed using spray drying technique achieving efficiencies of encapsulation higher than 90 % and process yields of 60 %. All the antimony IC50 values from encapsulated meglumine antimoniate in the chitosan microspheres tested against promastigotes and amastigotes are considerably lower compared to the mean value of IC50 in Glucantime® solution and give an Safety Index ratio higher than 1. Moreover, it is reported for the first time a novel in vitro activity of chitosan against L.infantum with a low cytotoxicity in macrophages assays (PATENEP P200700968). The uptake studies confirm the better suitability of chitosan as polymer to target drugs to macrophages compared to the commonly used PLGA. It has been shown that high percentages of chitosan in solutions to be spray-dried reduce the yield of the process, produce larger wrinkled microspheres but increase the efficiency of encapsulation. Chitosan microspheres exhibit a biphasic prolonged release for 24 h, characterized by an initial burst effect followed by slow release. High polymer ratios reduce the drug release in all the study. Moreover, high percentages of glutaraldehid in chitosan microspheres tend to increase significantly the presence of Non-Fickian drug release mechanism. These microspheres show the slowest release for the first 3 h but the highest percentage of drug released at 24 h. Moreover, they are among the more active microspheres against L.infantum. The minimum antimony IC50 value of chitosan microspheres is obtained using high percentages of glutaraldehid, low percentages of chitosan and low inlet temperatures. This new delivery system could offer a new pharmacological tool for treatment of leishmaniosis that reduces the doses required, lowering toxic side effects due to meglumine antimoniate.