The first temperature-sensitive hydrogel-based bioink has been developed for 3D printing artificial tissues.

Researchers from the Korea Institute for Science and Technology (Seoul, Korea) have developed a new bioink that does not require photocuring during the transplantation of 3D-printed tissues. This can significantly reduce the risk of unwanted side effects during this process.

Due to the increase in accidental injuries, chronic disease and a progressively aging population, there is an increased need for the transplantation of artificial organs and tissues. 3D printing technology can be used to create these 3D artificial tissues. Typically, these tissues are formed from hydrogel-based bioinks that go through a ‘hardening’ process in the body to enhance the 3D mechanical properties of the printed tissue. However, this process, known as ‘photocuring’, relies on chemical cross-linking agents and UV light to ‘set’ the 3D scaffold. This can have detrimental side effects such as causing cytotoxicity in the tissue, which damages or kills cells.

To address this issue, the researchers developed a new temperature-sensitive poly(organophosphazene) hydrogel bioink that does not require photocuring, therefore significantly lowering the risk of adverse side effects. This bioink is liquid at cool temperatures and then hardens to a hard gel consistency once it is transplanted into the body and is heated to body temperature. Further to this, it has also been designed to interact with the body’s growth factor proteins, which assist in tissue regeneration in the body. The implanted 3D scaffold creates an environment that maximizes tissue regeneration, encouraging the body to do so autonomously. This means that after a period of time, the scaffold can degrade in the body, but the tissue should continue to be regenerated via the body’s internal mechanisms.

To test this new bioink, the researchers 3D printed a scaffold using bioink that contained the growth factor proteins TGF-β1 and BMP-2, which are integral to bone regeneration. This scaffold was then transplanted into rats with damaged bones. The results showed that the surrounding tissue cells migrated into the scaffold and the bone was regenerated to normal functioning tissue. Then after 42 days, the scaffold had biodegraded away.

These were very encouraging results so the researchers hope to implement this new bioink into regenerating other tissue and organ types. “As the bioink developed this time has different physical properties, follow-up research to apply it to the regeneration of other tissues besides bone tissue is being conducted, and we expect to finally be able to commercialize bioink tailored to each tissue and organ,” commented corresponding author Song Soo-Chang.

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