Nanotechnology is rapidly growing and has great potential in various fields such as biomedical engineering, drug delivery, environmental health, pharmaceutical industries and even electronics and communication technologies. However, with this rapid development, these new nanoscale materials (including nanotubes, nanowires, nanowhiskers, fullerenes or buckyballs, and quantum dots) might have unintended human health and environmental hazards. Testing for toxicological parameters is a necessary first step toward ensuring the compatibility of nanomaterials for medical applications and for the safety of the environment. Here, we describe an array formatted electrical impedance sensing (EIS) system that is capable of measuring nanotoxicity in real time.