Nanotoxicity by quantum dots (QDs) has been extensively studied in prokarionte and eukaryonte cells. In this context, we are using QDs capped with mercaptoacetic acid synthetized in an aqueous medium in order to evaluate the nanocytotoxicity effects as cell death by autophagy in Trypanosoma cruzi. To check this fact, we used two kinds of autophagy markers: 3 methyladenine autophagy (3-MA) a phosphatidylinositol 3-kinase (PI3k) inhibitor and monodansylcadaverine (MDC) a lisossomotropic fluorescent compound useful for identifying cadaverine protein present in the autophagic vacuoles. The quantification of control parasites, 3-MA treated parasites and/or incubated with two QDs concentrations (2 and 200 μM) was made from the growth curves. Then, the same samples were processed for transmission electron microscopy (TEM) and labeling of autophagic vacuoles by MDC was qualitatively analyzed. The results from the growth curve indicated a decrease in parasite numbers incubated with 200μM QDs when compared to parasites incubated with 2μM QDs and the control group. In contrast, parasites incubated with 200μM QDs and treated with 10 and 15mM of 3-MA showed a dose-dependent reversion of cell death by 10% and 15% respectively. The parasite treated by MDC demonstrated many autophagic vacuoles. Also, we found ultrastructural morphological changes in parasites incubated with 2μM and 200μM QDs when compared to control group. Our results show that high QDs concentrations are toxic to T. cruzi, inducing cell death by autophagy.231110Weng, J., Song, X., Li, L., Qian, H., Chen, K., Xu, X., Cao, C., Ren, J., Highly luminescent CdTe quantum dots prepared in aqueous phase as an alternative fluorescent probe for cell imaging (2006) Talanta, 70 (2), pp. 397-402Marquis, B.J., Love, S.A., Braun, K.L., Haynes, C.L., Analytical methods to assess nanoparticle toxicity (2009) Analyst, 134, pp. 425-439Gomes, S.A.O., Vieira, C.S., Almeida, D.B., Santos-Mallet, J.R., Menna-Barreto, F.S., Cesar, C.L., Feder, D., CdTe and CdSe Quantum Dots Cytotoxicity: A Comparative Study on Microorganisms (2011) Sensors, 11, pp. 11664-11678Vieira, C.S., Almeida, D.B., Thomaz, A.A., Menna-Barreto, R.F.S., Santos-Mallet, J.R., Lenz, C.C., Gomes, S.A.O., Feder, D., Studying nanotoxic effects of CdTe quantum dots in Trypanosoma cruzi (2011) Mem. Inst. Oswaldo Cruz, 106, pp. 158-165Ma, J., Chen, J., Guo, J., Wang, C.C., Yang, W.L., Xu, L., Wang, P.N., Photostability of thiol-capped CdTe quantum dots in living cells: The effect of photo-oxidation (2006) Nano Technol, 17 (9), pp. 2083-2089Aldana, J., Wang, Y.A., Peng, X., Photochemical instability of CdSe nanocrystals coated by hydrophilic thiols (2001) J. Am. Chem. Soc, 123 (36), pp. 8844-8850Samia, A.C.S., Chen, X., Burda, C., Semiconductor quantum dots for photodynamic therapy (2003) J. Am. Chem. Soc, 125, p. 15736Kirchner, C., Liedl, T., Kudera, S., Pellegrino, T., Muñoz, J.A., Gaub, H.E., Stölzle, S., Parak, W.J., Citotoxicity of colloidal CdSe and CdSe/ZnS nanoparticles (2005) Nano Lett, 5, pp. 331-338Bertin, G., Averbeck, D., Cadmium: Cellular effects, modifications of biomolecules, modulation of DNA repair and genotoxic consequences (a review) (2006) Biochemie, 88, pp. 1549-1559Menna-Barreto, R.F.S., Salomão, K., Dantas, A.P., Santa-Rita, R.M., Soares, M.J., Barbosa, H.S., de Castro, S.L., Different cell death pathways induced by drugs in Trypanosoma cruzi: An ultrastrutural study (2009) Micron, 40, pp. 157-168Novy, F.G., McNeal, W.J., On the cultivation of Trypanosoma bruce (1904) J. Infect. Dis, 1, pp. 1-30Nicolle, G.L., Culture du parasite du Boutond'Orient (1908) C. R. Acad. Sci, 1, pp. 1-30Jaffe, C.L., Grimaldi, G., McMahon-Pratt, D., The cultivation and cloning of Leishmania (1984) Genes and Antigens of Parasites, pp. 48-91. , In Morel CM (ed.), A laboratory manual, 2nd ed. Fundação Oswaldo Cruz, Rio de JaneiroChiari, E., Camargo, E.P., Culturing and cloning of Trypanosoma cruzi (1984) Genes and Antigens of Parasites, pp. 23-26. , In: Morel C.M, A Laboratory Manual Rio de Janeiro, Fundação Oswaldo CruzFeder, D., Gomes, S.A.O., de Thomaz, A.A., Almeida, D.B., Faustino, W.M., Fontes, A., Stahl, C.V., Cesar, C.L., In vitro and in vivo Documentation of Quantum Dots Labeled Trypanosoma cruzi and Rhodnius prolixus Interaction using Confocal Microscopy (2009) Parasitol. Res, 106, pp. 85-93Monier, S., Samadi, M., Prunet, C., Denance, M., Laubriet, A., Athias, A., Berthier, A., Lizard, G., Impairment of the cytotoxic and oxidative activities of 7 beta-hydroxycholesterol and 7-ketocholesterol by esterification with oleate (2003) Biochem. Biophys. Res. Commun, 303 (3), pp. 814-824Pelley, J.L., Daar, A.S., Saner, M.A., State of Academic Knowledge on Toxicity and Biological Fate of Quantum Dots (2005) Toxicol. Sci, 112, pp. 276-296Parak, W.J., Pellegrino, T., Plank, C., Labelling of cells with quantum dots (2005) Nanotechnol, 16, pp. R9-R21Almeida, D.B., (2008) Pontos Quânticos Coloidais De Semicondutores II-VI Encapados Com SiO2, p. 111. , Dissertação de Mestrado. Universidade Estadual de CampinasChan, W.C., Maxwell, D.J., Gao, X., Bailey, R.E., Han, N., Nie, S., Luminescent quantum dots for multiplexed biological detection and imaging (2002) Curr. Opin. Biotechnol, 13, pp. 40-46Jaiswal, J.K., Mattoussi, H., Mauro, J.M., Simon, S.M., Long-term multiple color imaging of live cells using quantum dot bioconjugates (2003) Nat. Biotechnol, 21 (1), pp. 47-51Chaves, C.R., Fontes, A., Farias, P.M.A., Santos, B.S., Menezes, F.D., Ferreira, R., Cesar, C.L., Figueiredo, R.C.B.Q., Application of core-shell pegylated CdS/Cd(OH)2 quantum dots as biolabels of Trypanosoma cruzi parasites (2008) App. Surf. Sci, 255, pp. 728-730Dunn, W.A., Hubbard, A.L., Aronson Jr., N.N., Low temperature selectively inhibits fusion between pinocytic vesicles and lysosomes during heterophagy of 125I-asialofetuin by the perfused rat liver (1980) J. Biol. Chem, 255 (12), pp. 5971-5978Haylett, T., Thilo, L., Endosome-lysosome fusion at low temperature (1991) J. Biol. Chem, 266 (13), pp. 8322-8327Punnonen, E.L., Ryhänen, K., Marjomäki, V.S., At reduced temperature, endocytic membrane traffic is blocked in multivesicular carrier endosomes in rat cardiac myocytes (1998) Eur. J. Cell Biol, 75 (4), pp. 344-352Azzazy, H.M.E., Mansour, M.M.H., Luong, Q., Nanodiagnostics: A new frontier for clinical laboratory medicine (2006) Clin. Chem. Lab. Med, 52, pp. 1238-1246Hardman, R.A., Toxicologic Review of Quantum Dots: Toxicity Depends on Physicochemical and Environmental Factors (2006) Environm. Health Perspec, 114 (2), pp. 165-172Cho, S.J., Maysinger, D., Jain, M., Röder, B., Hackbarth, S., Winnik, F.M., Long-term exposure to CdTe quantum dots causes functional impairments in live cells (2007) Langmuir, 23, pp. 1974-1980Tang, M., Xing, T., Zeng, J., Wang, H., Li, C., Yin, S., Yan, D., Chen, R.D.Y., Unmodified CdSe quantum dots induce elevation of cytoplasmatic calcium levels and impairment of functional properties of sodium channels in rat primary culture hippocampal neurons (2008) Environ. Health Perspect, 116, pp. 915-922Zhang, L.W., Yu, W.W., Colvin, V.L., Monteiro-Riviere, N.A., Biological interactions of quantum dot nanoparticles in skin and in human epidermal keratinocytes (2008) Toxicol. Appl. Pharmacol, 228 (2), pp. 200-211Zhang, L.W., Zeng, L., Barron, A.R., Monteiro-Riviere, N.A., Biological interactions of functionalized single-wall carbon nanotubes in human epidermal keratinocytes (2007) Int. J. Toxicol, 26, pp. 103-113Lovric, J., Bazzi, H.S., Cuie, Y., Fortin, G.R.A., Winnik, F.M., Maysinger, D., Differences in subcellular distribution and toxicity of green and red emitting CdTe quantum dots (2005) J. Mol. Med, 83 (5), pp. 377-385Alvarez, V.E., Kosec, G., Sant, A.C., Turk, V., Cazzulo, J.J., Turk, B., Autophagy is Involved in Nutritional Stress Response and Differentiation in Trypanosoma cruzi (2008) J. Biol. Chem, 6 (283), pp. 3454-3464Chiela, E.C.F., (2011) A Autofagia E O Ciclo Celular Desempenham Papel Central No Mecanismo De Ação Do Resveratrol E Do Co-tratamento Com Temozolamida Em Células De Linhagens De Glioblastoma Humano, p. 172. , Dissertação de mestrado. Universidade Federal de Porto AlegreSeglen, P.O., Gordon, P.B., 3-Methyladenine: Specific inhibitor of autophagic / lysosomal protein degradation in isolated rat hepatocytes (1982) PNAS, 79, pp. 1889-1892Munafó, D.B., Colombo, M.I., A novel assay to study autophagy: Regulation of autophagosome vacuole size by amino acid deprivation (2001) J. Cell Sci, 20, pp. 3619-3629Fernandes, M.C., da Silva, E.N., Pinto, A.V., de Castro, S.L., Menna-Barreto, R.F., A novel triazolic naphthofuranquinone induces autophagy in reservosomes and impairment of mitosis in Trypanosoma cruzi (2012) Parasitol, 139 (1), pp. 26-36Rohloff, P., Docampo, R., A contractile vacuole complex is involved in osmoregulation in Trypanosoma cruzi (2008) Exp Parasitol, 118 (1), pp. 17-24. , Epub May 10Rohloff, P., Montalvetti, A., Docampo, R., Acidocalcisomes and the contractile vacuole complex are involved in osmoregulation in Trypanosoma cruzi (2004) J. Biol. Chem, 279 (50), pp. 52270-52281. , Epub 2004 Oct 4Mizushima, N., Methods for monitoring autophagy (2004) Int. J. Biochem. & Cell Biol, 36, pp. 2491-2502Lovric, J., Cho, S.J., Winnik, F.M., Maysinger, D., Unmodified Cadmium Telluride Quantum Dots induce reactive oxygens species formation leading to multiple organelle damage and cell death (2005) Chem. Biol, 12, pp. 1227-1234Gordeeva, A.V., Labas, Y.A., Zvyagilskaya, R.A., Apoptosis in unicellular organisms: Mechanisms and evolution (2004) Biochem, 69, pp. 1055-1066