You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Zinc oxide nanoparticle induced autophagic cell death and mitochondrial damage via reactive oxygen species generation. Zinc oxide nanoparticles (ZnO-np) are used in an increasing number of industrial products such as paint, coating and cosmetics, and in other biological applications. There have been many suggestions of a ZnO-np toxicity paradigm but the underlying molecular mechanisms about the toxicity of ZnO-np remain unclear. This study was done to determine the potential toxicity of ZnO-np and to assess the toxicity mechanism in normal skin cells. Synthesized ZnO-np generated reactive oxygen species (ROS), as determined by electron spin resonance. After uptake into cells, ZnO-np induced ROS in a concentration- and time-dependent manner. To demonstrate ZnO-np toxicity mechanism related to ROS, we detected abnormal autophagic vacuoles accumulation and mitochondria dysfunction after ZnO-np treatment. Furthermore mitochondria membrane potential and adenosine-5'-triphosphate (ATP) production are decreased for culture with ZnO-np. We conclude that ZnO-np leads to cell death through autophagic vacuole accumulation and mitochondria damage in normal skin cells via ROS induction. Accordingly, ZnO-np may cause toxicity and the results highlight and need for careful regulation of ZnO-np production and use.
{"Chemical": ["Zinc oxide", "ATP", "ZnO", "adenosine-5\u0027-triphosphate", "oxygen"]}