Sensors as tools for quantitation, nanotoxicity and nanomonitoring assessment of engineered nanomaterials

The discovery of fullerenes in 1985 has ushered in an explosive growth in the applications of engineered nanomaterials and consumer products. Nanotechnology and engineered nanomaterials (ENMs) are being incorporated into a range of commercial products such as consumer electronics, cosmetics, imaging and sensors. Nanomaterials offer new possibilities for the development of novel sensing and monitoring technologies. Nanosensors can be classified under two main categories: (i) Nanotechnology-enabled sensors or sensors that are themselves nanoscale or have nanoscale materials or components, and (ii) Nanoproperty-quantifiable sensors or sensors that are used to measure nanoscale properties. The first category can eventually result in lower material cost, reduced weight and energy consumption. The second category can enhance our understanding of the potential toxic effects of emerging pollutants from nanomaterials including fullerenes, dendrimers, and carbon nanotubes. Despite the enormous literatures and reviews on Category I sensors, there are few sensors to measure nanoscale properties or sensors belonging to Category II. This class of nanosensors is an area of critical interest to nanotoxicology, detection and risk assessment, as well as for monitoring of environmental and/or biological exposure. This article discusses emerging fields of nanotoxicology and nanomonitoring including the challenges of characterizing engineered nanomaterials and the potentials of combining existing analytical techniques with conventional cytotoxicity methods. Two case studies are provided for development of Category II nanosensors for fullerene nanoparticles and quantum dots. One highlights the uniqueness of a portable, dissolved oxygen electrochemical sensor arrays capable of detecting the ENMs as well as provide rapid nanotoxicological information. This review has shown that addressing the complex and critical issues surrounding the environmental transformation and toxicity of ENMs must be accompanied by the creation of new approaches or further developments of existing instrumentation.