Nanoscale electronic 'tattoos' track the health of each living cell

The researchers have touted this as a novel experiment in attaching sensors and electronics on live cells.
Sejal Sharma
False-colored gold nanodot array on a fibroblast cell
False-colored gold nanodot array on a fibroblast cell

Johns Hopkins University 

Nanotechnology has been used to probe and install intricate materials for tissue engineering, transfer of drugs, or diagnostic purposes in the human skin and internal organs. But tracking the health of our bodies at a single cell level? Though it sounds ambitious, a team of researchers and engineers at Johns Hopkins University has claimed that it can be done.

They have developed an electronic tattoo that can be put on a single cell to track its health. These are nanoscale tattoos, tens of times smaller than the head of a pin, and are made up of dots and wires that adhere and conform to the shape of the live cells.

"It's the first step toward attaching sensors and electronics on live cells," said David Gracias, a professor of chemical and biomolecular engineering at Johns Hopkins University who led the development of the technology.

Tattoos stick to live cells for 16 hours

Essentially acting like barcodes or QR codes, these electronic tattoos can stick to soft live cells for 16 hours. They bridge the gap between living cells or tissue and conventional sensors and electronic materials, said Gracias in a press release.

Made up of arrays with gold, this tattoo is attached to cells that make and sustain tissue in the human body, called fibroblasts, explained the researchers in the press release. Gold is known for its ability to prevent signal loss or distortion in electronic wiring.

The researchers then treated the arrays with molecular glues and transferred them 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.

Early detection of diseases

This is nothing like arranging wires in electronic chips. In order to track bio information, the sensors and wiring must be arranged into specific patterns.

"This is an array with specific spacing," Gracias explained, "not a haphazard bunch of dots."

"We've shown we can attach complex nanopatterns to living cells, while ensuring that the cell doesn't die," added Gracias. "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 is now working on extending the time beyond 16 hours and attaching more complex nanocircuits to different kinds of cells in the body.

The study was published in Nano Letters.

Study article:

Lithographic nanopatterning techniques such as photolithography, electron-beam lithography, and nanoimprint lithography (NIL) have revolutionized modern-day electronics and optics. Yet, their application for creating nanobio interfaces is limited by the cytotoxic and two-dimensional nature of conventional fabrication methods. Here, we present a biocompatible and cost-effective transfer process that leverages (a) NIL to define sub-300 nm gold (Au) nanopattern arrays, (b) amine functionalization of Au to transfer the NIL-arrays from a rigid substrate to a soft transfer layer, (c) alginate hydrogel as a flexible, degradable transfer layer, and (d) gelatin conjugation of the Au NIL-arrays to achieve conformal contact with live cells. We demonstrate biotransfer printing of the Au NIL-arrays on rat brains and live cells with high pattern fidelity and cell viability and observed differences in cell migration on the Au NIL-dot and NIL-wire printed hydrogels. We anticipate that this nanolithography-compatible biotransfer printing method could advance bionics, biosensing, and biohybrid tissue interfaces.

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