single layers of cells grown in a small dish - have enabled researchers to study biological growth, develop or test drugs and even discover what causes some diseases. Cell spheroids, 3D versions of cell cultures built using a process known as cell aggregation, are the next step in advancing this work, capable of more closely modeling real tissue.
According to Amir Sheikhi, associate professor and Dorothy Foehr Huck and J. Lloyd Huck Early Career Chair in Biomaterials and Regenerative Engineering, there are several major flaws that limit the survivability and function of the cells comprising spheroids. First, oxygen and nutrients cannot breach the outer layer to keep the inner cells functioning; second, without the help of blood vessels or channels to remove cellular waste or deliver nutrients and oxygen, it is difficult to grow spheroids to be large enough for use tissue engineering; and third, these spheroids do not initially have an extracellular matrix, which provides critical structural and chemical support to the cells.
A new technology, invented by researchers from Penn State and detailed in a paper published in Advanced Science, could breathe fresh air into bottom-up tissue fabrication and potentially large-scale tissue engineering by addressing these issues. The team's biohybrid spheroids - a mixture of living cells and microgels, tiny materials that mimic the supportive tissue that surrounds cells in the body - can rapidly self-assemble or "snowball" in size, while still allowing cell-supporting oxygen and nutrients to reach the cells inside.
Watch the biohybrid spheroids assemble
Sheikhi said the team plans to further develop biohybrid spheroids capable of mimicking the properties of tissue, with the eventual goal of enabling commercial-scale tissue engineering and organ biofabrication.
This work was partially supported by the National Heart, Lung, and Blood Institute of the National Institutes of Health.
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