Evaluating Regional Pulmonary Deposition using Patient-Specific 3D Printed Lung Models

This protocol has the potential to drive the development of new targeted pulmonary therapeutics by enabling the pre-clinical predictions of regional deposition. This technique incorporates anatomically accurate lung models, 3D printed from patient’s CT scans for the rapid generation of personalized predictive results regarding the efficacy of potential treatments. This technique can be used to develop targeted therapies that minimize off target effects for diseases that are characterized by regional area obstructions such as lung cancer or COPD.

After printing the experimental components and completing post-processing as per the manufacturer’s instructions, carefully wash the parts printed in soft resin with at least 99%purity isopropyl alcohol to remove any excess uncured resin before thermal curing the parts in a convection oven for eight hours according to the manufacturer’s specifications. Then, wash the parts printed in hard resin with the alcohol to remove any excess uncured resin and cure the parts in a UV oven for one minute per side. For lobe outlet cap assembly, insert one end of the oval barbed tubing connection base into the cap before carefully stretching the flexible cap over the other end of the oval base, taking special care not to crack the thin base and with the nozzle protruding through the opening in the cap base.

Next, cut 10 microliter filter paper to a size slightly larger than the outlet area and fold the filter paper over the lobe outlet, holding the paper in place with one hand. Then use tweezers in the other hand, to stretch the cap with the barbed tubing connection over the outlet and press the cap down until the notch matches the corresponding notch on the lobe outlet. Before each experimental run, connect each lung model lobe outlet to the tubing of the corresponding flow meter and valve taking care not to apply too much lateral pressure to the barbed tubing connection.

Attach the electronic flow meter to the lung model mouth inlet to measure the total airflow rate to the lung model and turn on the flow controller and vacuum pump. In the flow controller, select the test setup setting and slowly increase the flow rate until the electronic flow meter displays the desired total flow rate. Use the valves to adjust the flow rate through the right upper, right middle, right lower, left upper and left lower lung lobes.

Once the load flow rates shown on the flow meters are steady at the desired value, check the overall flow rate again on the electronic flow meter to verify that there are no leaks in the system. Then, exit the test setup in the flow controller leaving the vacuum pump on. For aerosol delivery to the lung model, fill a nebulizer with a solution of the desired fluorescent particles and connect the nebulizer to the lung model inlet.

To measure the efficacy of the targeting device, insert the device into the lung model and connect the nebulizer to the device. Connect the compressed airline to the nebulizer. Set the flow controller to run for one ten second trial and open the compressed air valve slightly to begin generating an aerosol within the nebulizer.

Press start on the flow controller and immediately open the compressed air valve fully. When the flow controller reaches about nine seconds, begin closing the compressed air valve and close the fume hood sash as much as possible. Once the valve is fully closed, disconnect the nebulizer from the compressed airline.

Fully close the fume hood sash, shut off the vacuum pump and let any aerosols clear from the fume hood. After about 10 minutes, disconnect the lung model from the tubing system, taking care not to crack the barbed tubing connections and run a pair of tweezers under the edge of each lobe outlet cap to remove the caps from the outlets. Then transfer the filter paper from each cap into individual wells of a 24-well plate particle depositions side down.

When all of the filter paper has been collected, place the plate onto the stage of a digital fluorescence microscope and set the microscope to a 4X magnification and the appropriate fluorescence channel. Then take at least three images of the filter paper from each lobe at random locations and save the images as TIF files. Under one liter per minute collection conditions in a healthy lung, ended along effected by COPD, the experimentally determined deposition profile is not statistically different from the clinical data demonstrating that the setup accurately mimics the distribution of air flow to each of the lung lobes.

Compared to the non-targeted particle deposition profile, the use of a modified endotracheal tube generates a nearly four fold increase in left lower lobe delivery. In addition to diverting over 96%of the delivered particles to the left lung. Altering the release location setting to target the right lower lobe, this device generates more than double the particle delivery to the right lobe and diverts 94%of the delivered particles to the right lung.

Compared to the non-targeted particle deposition profile, the concentric cylinder device causes a nearly three fold increase in left upper lobe delivery in addition to diverting over 87%of the delivered particles to the left lung. Targeting efficiency can also be observed qualitatively by comparing the images of the target lobe filter to the other outlet filters. As illustrated, the most effective targeting method will yield a high particle deposition at the intended lobe of interest and a low deposition at the remaining lobe outlets.

It is essential to make sure that components are properly connected to prevent leaks within the system as leaks will impact deposition results. This protocol permits researchers to test potential drug delivery devices for targeting specific regions of the lung prior to clinical trials reducing the cost associated with drug development and efficacy enhancement in human patients.