For some, tattoos are an expression of freedom: a piece of body art that will either prove to be a cool investment or a terrible regret once one realizes that the writing permanently etched into their skin reads “born to be mild” instead of “born to be wild.” But while tattoos are intended to enhance the wearer’s image in some way, in the research laboratory, scientists have been exploring how they could subdermally enhance the identification of samples. Researchers from the Johns Hopkins Whiting School of Engineering have been exploring ways to evolve the street art into an actionable labeling protocol in their research of a variety of biosamples. They developed a proof-of-concept of a technique that would allow them to tattoo live cells and tissues with flexible arrays of gold nanodots and nanowires. This could have potential benefits for the analysis of disease progression as well as living system dynamics with limited toxic effect — no needles required. An array of nanodots on a human skin fibroblast cell. Courtesy of Kam Sang Kwok and Soo Jin Choi/Gracias Lab at Johns Hopkins University. They strived to avoid using a process that would employ harsh chemicals, high temperatures, scary needles, or pressure extremes that could possibly kill or harm the living cells receiving the tattoos. The researchers discovered a much safer method for their collected cells and tissues, with the use of advancements in nanoimprint lithography to print a pattern of sub-300-nm gold lines, or dots, on a polymer-coated silicon wafer. The printed polymer undergoes a process of dissolving that leaves the print on a thin glass plate. Then, they functionalized the gold with cysteamine and covered it with a hydrogel layer. When the hydrogel layer was peeled away, it removed the array from the glass, essentially making a biomedical version of a temporary tattoo. The patterned side of the flexible array went through further processing during which it was coated with gelatin and attached to individual live fibroblast cells, and, finally, the hydrogel was degraded to expose the gold pattern on the surface of the selected cells. The researchers used similar techniques to apply gold nanoarrays to sheets of fibroblasts and, probably most impressive of all, to rat brains. The experiments showed that the arrays are biocompatible and could guide cell orientation and mitigation, which means that in the future, the implementation and wide commercialization of the technology could very well lead to microscopic cyborgs becoming a reality in a highly controlled and adaptable operation. Whether one is excited to live in a world of cyber punk aesthetics, the researchers say that their approach could open opportunities for the development of biohybrid materials, bionic devices, and biosensors that could transfer information wirelessly from living cells. So, while cyborg enhancements are still a ways away, perhaps one day soon, a misspelled tattoo might have more use than a cautionary tale of a bad night out.
