Hemocompatibility of inhaled environmental nanoparticles: Potential use of in vitro testing

Hemocompatibility testing is an important part in the evaluation of nano-based medicines. However, it is not systematically used for the assessment of environmental particles since they do not come in contact with blood immediately. Studies on human exposure to air-borne particles and pulmonary exposure of rodents have reported alterations in blood physiology. It is not clear, whether these effects are majorly caused by tissue inflammation or translocated particles in blood. This review addresses the question, if in vitro hemocompatibility testing could help in the risk evaluation of inhaled particles. Particle blood concentrations were estimated based on exposure levels, ventilation volume, deposition rate, lung surface area, and permeability of the alveolar epithelium to particles. The categories of hemocompatibility, thrombosis, coagulation, platelets, hematology, and immunology, were introduced. Also, concentrations of ultrafine particles, silver nanoparticles, carbon nanotubes that caused adverse effects in human blood samples were compared to the estimated concentrations of translocated particles. The comparison suggested that, it is unlikely for translocated nanoparticles to be the sole cause of adverse blood effects. Nevertheless, the testing of specific hemocompatibility parameters (hemolysis and clotting) in healthy blood might help to compare biological effect of inhaled particles containing different amounts of contamination. Testing of samples from healthy and diseased persons might help to identify pathological dispositions that increase the possibility of adverse reaction of nanoparticles in blood.