Lung diseases kill millions of people worldwide each year. Treatment options are limited, and animal models to study these diseases and experimental drugs are inadequate. Now, researchers describe in ACS Applied Biological Materials Their success in creating a mucus-based bioink for 3D printing lung tissue. This breakthrough could one day help study and treat chronic lung diseases.
Although some people with lung diseases receive transplants, donor organs remain in short supply. Alternatively, drugs and other treatments can be used to manage symptoms, but there is no cure for disorders such as chronic obstructive pulmonary disease and cystic fibrosis. Researchers continue to search for better drugs, often based on tests in rodents. But these animal models can only partially capture the complexities of lung diseases in humans, and might not accurately predict the safety and effectiveness of new drugs. Meanwhile, bioengineers are exploring producing lung tissue in the lab, either as a more accurate model for studying human lungs or as a potential material for use in implants. One technique involves 3D printing structures that mimic human tissue, but designing a suitable bioink to support cell growth remains a challenge. So Ashok Raichur and his colleagues set out to overcome this hurdle.
The team started with mucin, a component of mucus that has not been widely explored for bioprinting. Segments of this antibacterial polymer’s molecular structure resemble epidermal growth factor, a protein that promotes cell adhesion and growth. Raichur and colleagues reacted the mucin with methacrylic anhydride to form methacrylated mucin (MuMA), which they then mixed with lung cells. Hyaluronic acid, a natural polymer found in connective and other tissues, was added to increase the viscosity of the bioink and enhance cell growth and adhesion to MuMA. After the ink was printed in test patterns that included round and square grids, it was exposed to blue light to cross-link the MuMA molecules. The cross-linking bonds stabilized the printed structure as a porous gel that readily absorbed water to support cell survival.
The researchers found that the gel’s interconnected pores facilitated the diffusion of nutrients and oxygen, which stimulated cell growth and lung tissue formation. The printed structures were nontoxic and slowly biodegraded under physiological conditions, making them potentially suitable as implants in which the printed scaffold would be gradually replaced by newly developed lung tissue. The bioink could also be used to make 3D models of lungs to study lung disease processes and evaluate potential treatments.
The authors acknowledge funding from the Department of Science and Technology, Government of India.