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

Summary

We present a high-throughput, in vitro method for quantifying regional pulmonary deposition at the lobe level using CT scan-derived, 3D printed lung models with tunable air flow profiles.

Abstract

Development of targeted therapies for pulmonary diseases is limited by the availability of preclinical testing methods with the ability to predict regional aerosol delivery. Leveraging 3D printing to generate patient-specific lung models, we outline the design of a high-throughput, in vitro experimental setup for quantifying lobular pulmonary deposition. This system is made with a combination of commercially available and 3D printed components and allows the flow rate through each lobe of the lung to be independently controlled. Delivery of fluorescent aerosols to each lobe is measured using fluorescence microscopy. This protocol has the potential to promote the growth of personalized medicine for respiratory diseases through its ability to model a wide range of patient demographics and disease states. Both the geometry of the 3D printed lung model and the air flow profile setting can be easily modulated to reflect clinical data for patients with varying age, race, and gender. Clinically relevant drug delivery devices, such as the endotracheal tube shown here, can be incorporated into the testing setup to more accurately predict a device’s capacity to target therapeutic delivery to a diseased region of the lung. The versatility of this experimental setup allows it to be customized to reflect a multitude of inhalation conditions, enhancing the rigor of preclinical therapeutic testing.

Introduction

Many pulmonary diseases such as lung cancer and chronic obstructive pulmonary disease (COPD) exhibit regional differences in disease characteristics; however, there are a lack of therapeutic techniques available to target drug delivery to only diseased regions of the lung¹. Multiple computational fluid dynamic (CFD) models have demonstrated that it is possible to modulate drug deposition profiles by identifying specific streamlines in the lung^2,3. Development of both inhalers and endotracheal (ET) tube adaptors with regional targeting capabilities are on-going in our lab to control aero....

Protocol

1. Preparation of 3D printed experimental components

NOTE: All software used in the protocol are indicated in the Table of Materials. Additionally, the slicing software utilized is specific to the 3D printer listed in the Table of Materials; however, this protocol can be extended to a wide range of stereolithography (SLA) 3D printers.

1. Convert patient CT scans to 3D objects (.stl files).
   NOTE: For a more detailed discussion of the geometric features of the specific lung model used in these studies, refer to Feng et al.⁵.
   1. Render CT scans into a 3D ob....

Results

Particles in this size range (1-5 μm) and flow conditions (1-10 L/min) follow the fluid stream lines based on both their theoretical Stokes number and in vivo data; therefore, in the absence of a targeted delivery device, particles released into the lung model are expected to deposit according to the percentage of total airflow diverted to each lobe. The relative amounts of particle delivery to each lobe can then be compared to clinical lobe flow rate data obtained through analyzing patient-specific high-resolution compu.......

Discussion

The current state-of-the-art device for pulmonary pharmaceutical testing of a complete inhalation dose is the Next Generator Impactor (NGI), which measures the aerodynamic diameter of an aerosol⁴. This sizing data is then used to predict the lung generation at which the aerosol will deposit based on a correlation developed for a healthy adult male¹¹. Unfortunately, this method is limited in its ability to assess differences in regional lung deposition, determine the effects.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
1/4" Plastic Barbed Tube Fitting	McMaster Carr	5372K111
10 um Filter Paper	Fisher	1093-110
1um Fluorescent Polystyrene Particles	Polysciences	15702-10
1um Non-Fluorescent Polystyrene Particles	Polysciences	8226
2-Propanol	Fisher	A516-4	Referred to in protocol as "IPA"
3/8" Plastic Barbed Tube Fitting	McMaster Carr	5372K117
Air Flow Meter (1 - 280 mL/min)	McMaster Carr	41695K32	Referred to in protocol as "flow meter"
Carbon M1 3D Printer	Carbon 3D		https://www.carbon3d.com/, Associated software referred to in protocol as "slicing software"
Collison Jet Nebulizer	CH Technologies	ARGCNB0008 (CN-25)	6 Jet MRE style horizontal collision with glass jar, Referred to in protocol as "nebulizer", http://chtechusa.com/Manuals/MRE_Collison_Manual.pdf
Convection Oven	Yamato	DKN602
Copley Critical Flow Controller TPK2000 Reve 120V	MSP Corp	0001-01-9810	Referred to in protocol as "flow controller"
Copley High Capacity Pump Model HCP5	MSP Corp	0001-01-9982	Referred to in protocol as "vacuum pump"
Cytation	BioTek	CYT5MPV	Multifunctional Spectrophotometer/Fluorescent imager equiped with 4x/20x/40x objectives and DAPI/GFP/TexasRed laser/filter cubes
EPU40 Resin	Carbon 3D		https://www.carbon3d.com/materials/epu-elastomeric-polyurethane/, Referred to in protocol as "soft resin"
Filter for vacuum pump	Whatman	6722-5000
Flow Meter Model DFM 2000	MSP Corp	0001-01-8764	Referred to in protocol as "electronic flow meter"
ImageJ Software	ImageJ		https://imagej.nih.gov/ij/download.html
Inline Air Flow Control Valve (Push-to-Connect)	McMaster Carr	62005K333	Referred to in protocol as "valve"
Inline Filter Devices	Whatman	WHA67225000
Marine-Grade Plywood Sheet	McMaster Carr	62005K333	Referred to in protocol as "wooden board"
Materialise Mimics Software	Materialise		https://www.materialise.com/en/medical/mimics-innovation-suite, Referred to in protocol as "CT scan software"
Meshmixer Software	Autodesk		http://www.meshmixer.com/, Referred to in protocol as "mesh editing software"
Methanol	Fisher	A454-4
Opticure LED Cube	APM Technica	102843	Referred to in protocol as "UV oven"
PR25 Resin	Carbon 3D		https://www.carbon3d.com/materials/uma-urethanemethacrylate, /Referred to in protocol as "hard resin"
PVC Tube for Chemicals	McMaster Carr	5231K161	1/4" ID
Screws
SolidWorks Software	Dassault Systèmes SolidWorks Corporation		https://www.solidworks.com/, Referred to in protocol as "3D modeling software"
Straight Flow Rectangular Manifold	McMaster Carr	1125T31
Tubing to Flow Controller	McMaster Carr	5233K65	3/8" ID
Wire