Nanotechnology has been highly influential across different fields, prompting substantial progression a relatively short time. In biomedicine, nonmaterial’s can be potentially used as tools for immunohistochemical detection and bioimaging, as biosensors and new modes of drug delivery [1-3]. Many research laboratories currently work with nonmaterial’s, which results in greater occupational exposure and, certainly, greater environmental pollution . However, knowledge of their toxic potential is limited and there is no appropriate regulatory measures regarding their use . Quantum dots (QDs) are semiconductor nanomaterials with particular optical and physicochemical properties. They are synthesized with different sizes and coating, so current research has focused on how theseproperties affect their fate and how they interact with their cellular environment [6-8]. CdTeQDs has shown evidence of cytotoxicity in vitro [9-12]. Nevertheless, there is little information regarding their potential effect on cellular systems and how this is affected by concentration, exposure time and functionalization. Short- and long-term dose-response pharmacological studies of new molecules are necessary in order to know whether there is accumulation or toxicity, and if these molecules can be potentially used in humans. Cadmium selenide or cadmium telluride particles are considered the most suitable emitting ‘core’ materials because of their bright emission in the visible range and near the infrared region of the electromagnetic spectrum [13-15]. However, there are problems regarding unsuitable capping agents, retention of particles over a certain size, biological magnification, and the breakdown and decomposition products of these inorganic materials. Protecting the core can, to some degree, control the toxicity related to cadmium and selenium leakage. However, the change in the physicochemical and structural properties of engineered quantum dots could be responsible for a number of material interactions that could also have toxicological effects. This study employed CdTe quantum dots (QDs) with a carboxylgroup for the surface coating (CdTe-COOH QDs) and evaluated their cytotoxicity on HeLa cells. In order to determine cytotoxicity, we treated cells at 0.1 to 1000 ng/mL for short and long time periods, and examined cell death and genotoxic effects. Cellular and sub cellular uptake were also studied.