Caltech researchers develop novel method for in vivo 3D printing using ultrasound.
There’s no doubt that 3D printing has revolutionized the medical industry, from surgical jigs and training models developed with the aid of 3D scanning, to customized prosthetics that incorporate lattice structures to accelerate bone regrowth.
Taking 3D printing for better health to the next level, a team of researchers at Caltech have developed a method for 3D printing polymers at specific locations deep inside living animals. The technique uses sound for localization has already been deployed to print polymer capsules for selective drug delivery adhesive polymers to seal internal wounds.
Previous research used infrared light to trigger polymerization in vivo. However, by its nature, this approach is limited to just below the surface of the skin. “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,” said Wei Gao, a professor of medical engineering at Caltech.
Along with bioadhesive gels and polymers for drug and cell delivery, Gao and his colleagues are also investigating printing bioelectric hydrogels for use in the internal monitoring of physiological vital signs as in electrocardiograms.
The use of ultrasound for targeting deep tissues is common in biomedicine, but the researchers needed a way to initiate the polymerization process on-demand at specific locations. Their solution is to combine ultrasound with low-temperature-sensitive liposomes: spherical cell-like vesicles with protective fat layers that are used for drug delivery.
By loading the liposomes with a polymerizing agent and embedding them in a solution of to-be-printed monomers along with an imaging contrast agent and the desired “cargo” such as cells or conductive materials, they created a bioink that can be injected directly into the body. Using focused ultrasound raises them temperature of the liposomes, they can thereby trigger the printing process.
“Increasing the temperature by a few degrees Celsius is enough for the liposome particle to release our crosslinking agents,” said Gao. “Where the agents are released, that’s where localized polymerization or printing will happen.”
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