At the Crossroads of Nanotoxicology in vitro: Past Achievements and Current Challenges.

The exponential growth in the employment of nanomaterials (NMs) has given rise to the field of nanotoxicology; which evaluates the safety of engineered NMs. Initial nanotoxicological studies were limited by a lack of both available materials and accurate biodispersion characterization tools. However, the years that followed were marked by the development of enhanced synthesis techniques and characterization technologies; which are now standard practice for nanotoxicological evaluation. Paralleling advances in characterization, significant progress was made in correlating specific physical parameters, such as size, morphology, or coating, to resultant physiological responses. Although great strides have been made to advance the field, nanotoxicology is currently at a crossroads and faces a number of obstacles and technical limitations not associated with traditional toxicology. Some of the most pressing and influential challenges include establishing full characterization requirements, standardization of dosimetry, evaluating kinetic rates of ionic dissolution, improving in vitro to in vivo predictive efficiencies, and establishing safety exposure limits. This Review will discuss both the progress and future directions of nanotoxicology: highlighting key previous research successes and exploring challenges plaguing the field today.