A computational model to characterize the Vitrocell® cell exposure system for evaluation of aerosols
In vitro exposure systems can be used as tools for toxicological assessment of e-cigarette aerosols. The VITROCELL® exposure system is designed such that exposure of cell cultures to the aerosol occurs at the air/liquid interface, which is relevant to e-cigarette use. It is difficult to experimentally quantify the actual cell dose applied in the VITROCELL® system, as it depends on multiple parameters such as system geometry, particle size and distribution, air flow-rate, exposure level and duration, etc.. A computational fluid dynamics aerosol tracking and deposition model that employs Lagrangian particle tracking method has been developed to quantify deposition rates of particles on the air/liquid interface in a VITROCELL® 24/48 system. The system consists of a 6 mm diameter main line carrying the aerosol, with six smaller 3 mm diameter tubes (trumpets) branching down to the cell exposure plates. Results of simulations for a main line air flow rate of 1 L/min and trumpet flow rates of 1- 4 mL/min will be discussed. Simulations were performed for inert non-reacting solid particles with a range of diameters between 0.5 and 4.5 µm and densities of 1050 kg/m3. The impact of particle size and air flow rate on deposition efficiency on the cell plates was explored. Results show that for a trumpet to main air flow ratio of 2/1000, the fraction of inlet particles deposited on the cell exposure plates is less than 0.001. This can be attributed to (1) lower particle concentration near the wall in the main line and (2) carryover of particles by the trumpet air out of the system. Once validated, the model will be used to quantify cell exposure from different e-cigarette aerosol streams.