Caltech researchers have developed a new method for 3D printing polymers inside living organisms. The technique, called deep tissue in vivo sound printing (DISP), uses ultrasound to trigger the formation of polymers at specific locations deep within animal tissue. Unlike previous methods that relied on infrared light with limited penetration capabilities, this ultrasound-based approach can reach deeper tissues.
The process involves injecting a composite bioink containing temperature-sensitive liposomes loaded with a crosslinking agent. When focused ultrasound raises the temperature of a targeted area by approximately 5 degrees Celsius, the liposomes release their payload, initiating localized polymerization. Gas vesicles derived from bacteria serve as imaging contrast agents, allowing researchers to visualize exactly where the printing occurs.
“Our new technique reaches the deep tissue and can print a variety of materials for a broad range of applications, all while maintaining excellent biocompatibility,” explains Wei Gao, professor of medical engineering at Caltech. The team has successfully printed polymer capsules for drug delivery, adhesive polymers for sealing internal wounds, and bioelectric hydrogels for monitoring physiological signs.
In tests with mice, the researchers used the DISP platform to print polymers containing doxorubicin near bladder tumors. This targeted delivery method resulted in significantly more tumor cell death compared to direct drug injection. The technology shows promise for applications including tissue repair and targeted treatment delivery.
The research team is now working to test the technology in larger animal models with hopes of eventually evaluating it in humans. Gao suggests that machine learning could further enhance the precision of the technique. “In the future, with the help of AI, we would like to be able to autonomously trigger high-precision printing within a moving organ such as a beating heart,” he says.
The findings were published in the journal Science, with Elham Davoodi as lead author. The research received funding from the National Institutes of Health, the American Cancer Society, the Heritage Medical Research Institute, and the Challenge Initiative at UCLA.
Source: caltech.edu