New York: A team led by engineers at University of California-San Diego has 3D-printed a tissue that closely mimics the human liver's sophisticated structure and function.

The new model can be used for patient-specific drug screening and disease modeling, thus helping pharmaceutical companies save time and money when developing new drugs.

It typically takes about 12 years and $1.8 billion to produce one FDA-approved drug because over 90 percent of drugs don't pass animal tests or human clinical trials.

"We have made a tool that pharmaceutical companies could use to do pilot studies on their new drugs, and they won't have to wait until animal or human trials to test a drug's safety and efficacy on patients," said Shaochen Chen, nano engineering professor at the UC San Diego's Jacobs School of Engineering.

The team engineered a human liver tissue model that more closely resembles the real thing -- a diverse combination of liver cells and supporting cells systematically organised in a hexagonal pattern.

The liver is unique in that it receives a dual blood supply with different pressures and chemical constituents.

"Our model has the potential of reproducing this intricate blood supply system, thus providing unprecedented understanding of the complex coupling between circulation and metabolic functions of the liver in health and disease," Chen explained.

The entire structure - 200 micrometers thick -- takes just seconds to print. This is a vast improvement over other methods to print liver models which typically take hours.

The structure was cultured in vitro for at least 20 days. The researchers then tested the resulting tissue's ability to perform various liver functions, such as albumin secretion and urea production, and compared it to other models.

They found that their model was able to maintain these functions over a longer time period than other liver models.

Their model also expressed a relatively higher level of a key enzyme that's considered to be involved in metabolizing many of the drugs administered to patients.

"I think that this will serve as a great drug screening tool for pharmaceutical companies and that our 3D bio printing technology opens the door for patient-specific organ printing in the future," Chen added in a paper published in the journal Proceedings of the National Academy of Sciences.

The liver tissue constructed by this novel 3D printing technology will also be extremely useful in reproducing in vitro disease models such as hepatitis, cirrhosis, and cancer, the authors noted.

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