A Technique to Generate and Deliver Drug Aerosols Directly to Mouse Lungs

To generate a nebulized liquid aerosol, dissolve the drug of interest in 100 milliliters of water and load a 100-milliliter syringe with the resulting drug solution.

Place the syringe into a syringe pump with the flow rate set at 1 milliliter per minute, and connect the pump to the jet nebulizer.

Purge the air from the feed line leading to the nebulizer, and connect the pressurized air source to the jet nebulizer. Then, set the airflow meter to 10 liters per minute with the jet nebulizer installed into the pre-separator, which connects the nebulizer to the central aerosol plenum of the inhalation unit.

First, transfer a pre-weighed filter into the filter holder and assemble the holder.

Connect the inlet of the absolute filter holder to a central aerosol plenum sample port in the outlet to a vacuum source.

Next, assemble the cascade impactor to collect the aerosol by placing pre-weighed filters onto each of the seven stages of the cascade impactor, and assemble the Mercer Cascade Impactor.

Proper assembly of the cascade impactor is critical. The stages must be loaded in the correct order and orientation, with the largest stage closest to inlet.

Connect the inlet of the cascade impactor to a central aerosol plenum sample port in the outlet to a vacuum source.

To monitor the aerosol content of the inhalation unit, connect the inlet of the real-time aerosol monitor to a central aerosol plenum sample port in the outlet to a vacuum source.

Set the process control parameters to the appropriate values according to the number of animals to be connected to the inhalation unit, and begin the delivery of the aerosolized drug of interest. Plug the delivery ports of the inhalation unit with stoppers and activate the aerosol generator, the compressed air flow controller, and the inhalation unit vacuum pump from within the process control software.

Now, load the experimental mice into the nose-only restrainers, angling the restraining tubes up towards the ceiling as the animals tend to run upward during the loading process with the noses in the pointed ends of the tubes.

Fix the variable-position plungers into the back ends of the restrainers so that the animals can rotate but not turn head-to-tail.

Loading the mice into the restraining tubes takes patience and coordination. Please handle the animals gently.

When the readings from the real-time aerosol monitor demonstrate that the aerosol concentration has reached equilibrium, begin removing the stoppers and inserting the nose-only restraining tubes into the inhalation unit.

When all of the experimental animals are connected to the exposure unit, turn on the vacuum sampling pumps connected to the absolute filter in the cascade impactor.

Deliver the drug to the animals for the appropriate time periods.

When all of the exposures are complete, turn off the aerosol generator and remove the mice from the inhalation unit.