Bioreactivity of carbon black and diesel exhaust particles to primary Clara and type II epithelial cell cultures

Objectives-To begin to elucidate the mechanisms of particle toxicity to the lung, the bioreactivity of four carbon black (CB) and diesel exhaust parti cles ((DEPs), a surrogate for particulate matter of aerodynamic diameter <1 0 mu m (PM10), were examined with primary cultures of Clara and type II epi thelial cells. Methods-The particles were extensively characterised by surface chemistry, size, and aggregation properties. Toxicity of the particles was assessed by determining cell attachment to an extracellular matrix substratum. Results-The spherulite size range for the particles ranged from 50, 40, 20, 20, and 30 nm for CB1-4 and DEPs. All particle samples had different surfa ce chemical compositions. CB1 was the least toxic to Clara (170 mu g) and t ype II cells (150 mu g) and CB4 was the most toxic (55 mu g and 23 mu g res pectively). DEPs stored for 2 weeks were equally toxic to both epithelial c ell types (27-28 mu g). DEPs became progressively less toxic to type II cel ls with time of storage. Both primary epithelial cell types internalised th e particles in culture. Conclusions-Bioreactivity was found to be related to CB particle spherulite size and hence surface area: the smaller the particle and larger the surfa ce area, the more toxic the particles. Also, CB particles with the most com plicated surface chemistry were the most bioreactive. Freshly prepared DEPs were equally toxic to type II and Clara cells and they became progressivel y less toxic to the type II cells with time. With all CB and DEPs, the prim ary epithelial cells internalised the particles, although this was noted mo st in cells of low functional competence.