Lung diseases kill millions of people worldwide each year; treatment options are limited, and animal models for studying the disease and experimental drugs are insufficient. But researchers report in the journal ACS Applied Biomaterials on July 12 that they have successfully created a mucus-based bioink for 3D printing of lung tissue, an advance that could one day help study and treat chronic lung conditions.
The challenge facing scientists
While some people with lung disease receive transplants, donated organs remain in severe shortage. Alternatively, medications and other therapies can be used to manage symptoms, but there is no cure for disorders such as COPD and cystic fibrosis.
Researchers continue to search for better drugs, often relying on laboratory mice for their tests, but these animal models may only partially capture the complexities of lung disease in humans, and may not accurately predict the safety and effectiveness of new drugs.
Meanwhile, scientists are exploring the production of lung tissue in the lab, either as a more accurate model for studying human lungs or as a potential material for use in transplants. 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 at the Department of Materials Engineering, Indian Institute of Science in India, decided to overcome this hurdle, according to EurekAlert.
Steps forward
The team started with mucin, a component of mucus that has not been widely explored in bioprinting. Parts of the molecular structure of this antibacterial polymer resemble epidermal growth factor, a protein that promotes cell attachment and growth. Raichur and his colleagues reacted mucin with methacrylic anhydride to form mucin methacrylate (MuMA), which they then mixed with lung cells.
Hyaluronic acid, a natural polymer found in connective tissues and elsewhere, was added to increase the viscosity of the bioink and promote cell growth and adhesion to the methacrylate mucin. After the ink was printed into test patterns including round and square grids, it was exposed to blue light to cross-link the methacrylate mucin molecules. The cross-links were observed to stabilize the printed structure into a porous gel that readily absorbs water to support cell survival.
The researchers found that the interconnected pores in the gel facilitated the diffusion of nutrients and oxygen, which encouraged cell growth and lung tissue formation. The printed structures were non-toxic and biodegraded slowly under physiological conditions, making them potentially suitable as implants in which the printed structure is gradually replaced by new lung tissue. The bioink could also be used to create 3D models of the lungs to study lung disease processes and evaluate potential treatments.