Nanoscale tattoos could track health of individual cells

For the first time, the new technology allows the placement of optical elements or electronics on live cells with tattoo-like arrays that stick on cells while flexing and conforming to the cells’ wet and fluid outer structure. The structures were able to stick to soft cells for 16 hours even as the cells moved. The team’s findings are detailed in Nano Letters.

“If you imagine where this is all 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,” said David Gracias, a professor of chemical and biomolecular engineering at Johns Hopkins University who led the effort. “If we had technologies to track the health of isolated cells, we could maybe diagnose and treat diseases much earlier and not wait until the entire organ is damaged.” 

Gracias said the tattoos bridge the gap between living cells or tissue and conventional sensors and electronic materials, adding that they are essentially like barcodes or QR codes.

“We're talking about putting something like an electronic tattoo on a living object tens of times smaller than the head of a pin,” Gracias said. “It’s the first step towards attaching sensors and electronics on live cells.”

The researchers built the tattoos in the form of arrays with gold, a material that prevents signal loss or distortion in electronic wiring.

They attached the arrays to fibroblasts, which are cells that make and sustain tissue in the human body. The arrays were then treated with molecular glues and transferred onto the cells using an alginate hydrogel film, a gel-like laminate that can be dissolved after the gold adheres to the cell. The molecular glue on the array bonds to a film secreted by the cells called the extracellular matrix.

Previous research has demonstrated how to use hydrogels to stick nanotechnology onto human skin and internal animal organs.

“We’ve shown we can attach complex nanopatterns to living cells, while ensuring that the cell doesn’t die,” Gracias said. “It’s a very important result that the cells can live and move with the tattoos because there’s often a significant incompatibility between living cells and the methods engineers use to fabricate electronics.”

The team’s ability to attach the dots and wires in an array form proved crucial; to use this technology to track bioinformation, researchers must be able to arrange sensors and wiring into specific patterns. 

“This is an array with specific spacing, not a haphazard bunch of dots,”  said Gracias

Looking forward, the team will try to attach more complex nanocircuits that can stay in place for longer periods and experiment with different types of cells.