It may seem like the ultimate in bling, but a new technique for tattooing gold onto living tissue is a step toward integrating human cells into electronic devices.
Using a fabrication technique called nanoimprint lithography, scientists printed live mouse embryonic fibroblast cells with patterns of gold nanodots and nanowires. This is an important first step towards adding more complex circuits.
And not just because cyborgs are cool. According to the scientists who developed it, led by Johns Hopkins University engineer David Gracias, the technique could have incredible health applications.
A mouse fibroblast “tattooed” with gold nanodots. (Kwok et al., Nano Lett., 2023)
“If you imagine where all this is going in the future, we would like to have sensors to remotely monitor and control the state of individual cells and the environment surrounding those cells in real time,” says Gracias.
“If we had technologies to track the health of isolated cells, we might be able to diagnose and treat diseases much earlier and not wait until the entire organ is damaged.”
Engineers have been looking for a way to integrate electronics into human biology for some time, but significant obstacles remain. One of the biggest hurdles is the incompatibility of living tissue with the manufacturing techniques used to create electronics.
Although there are ways to make things small and flexible, they often use harsh chemicals, high temperatures, or vacuum that destroy living tissue or soft, water-based materials.
A gold nanowire array sticking to one ex vivo rat brain. (Kwok et al., Nano Lett., 2023)
Gracias and his team based their technique on nanoimprint lithography, which is exactly what it sounds like: using a stamp to imprint nanoscale patterns into a material. Here the material is gold, but that is only the first step of the process. Once the pattern is created, it must be transferred to living tissue and adhere there.
The researchers first printed their nanoscale gold onto a polymer-coated silicon wafer. The polymer was then dissolved so the pattern could be transferred onto thin glass films, where it was treated with a biological compound called cysteamine and coated with a hydrogel.
Then the pattern was removed from the glass and treated with gelatin before being transferred to a fibroblast cell. Finally, the hydrogel was dissolved. The cysteamine and gelatin helped the gold bind to the cell, where it stayed and moved with the cell for the next 16 hours.
They used the same technique to attach gold nanowire arrays to it ex vivo rat brains. But the fibroblasts are the most exciting result.
A diagram illustrating the transfer process to the cell. (Kwok et al., Nano Lett., 2023)
“We have shown that we can attach complex nanopatterns to living cells while ensuring that the cell does not die,” says Gracias.
“It is a very important finding that the cells with the tattoos can live and move, as there is often a significant incompatibility between living cells and the methods that engineers use to manufacture electronics.”
Because nanoscale lithography is relatively simple and inexpensive, the work represents a way to develop more complicated electronics such as electrodes, antennas and circuits that can be integrated not only into living tissue but also into hydrogels and other soft materials that can be used they are not compatible with harsher manufacturing methods.
“We expect that this nanostructuring process, in combination with different classes of materials and standard microfabrication techniques such as photolithography and electron beam lithography, will open up opportunities for the development of new cell culture substrates, biohybrid materials, bionic devices, etc.” Biosensors.
The research was published in nano letters.