By Rae Nadler-Olenick
College of Engineering

A team of engineers from The University of Texas at Austin has developed a promising new process for binding tiny semiconductor crystals known as nanocrystals or "quantum dots" to nerve cells. Their technology could lead to advances in biomedical products ranging from hearing aid implants to robotic prosthetics.

Pictured is the quantum dot attaching to neurons using antibody (A, B) and peptide (C, D) binding techniques. Images B and D show the self-fluorescence of the cell's cytoplasm and the quantum dot luminescence.

Professor of Biomedical Engineering Christine Schmidt, an expert in neuro-cell culture and nerve engineering, and Brian Korgel, a chemical engineering professor whose specialty is growing nanocrystals, report the initial results of their yearlong collaboration in the Nov. 16 issue of Advanced Materials.

Doctoral candidate Jessica Winter performed key research in both professors’ laboratories.

The researchers succeeded in making cadmium sulfide quantum dots about one-four thousandth the width of a human hair in diameter stick one-on-one to human brain neurons, using a short protein chain called a peptide as a tether. That involved modifying what Korgel describes as a "standard chemistry recipe" by substituting the single peptide for two much longer protein antibodies.

Schmidt noted that most work in the realm of biological-electronic interfaces to date has involved comparatively large silicon-based electrodes and larger tissue areas. "Our goal was to gain more molecular specificity, to target specific receptors on the cell surface," she said.

The next challenge will be to establish communication between the biological and non-biological systems. Because the dots are semiconductors, they become active in the presence of an electrical field.

Korgel said the few previous efforts by other research groups to attach quantum dots to human cells have concentrated strictly on silicon-based dots intended for use as inert dyes.

"But we’re working toward putting these quantum dots on nerve cells and then generating local electrical fields that will influence the cells to ‘talk’ to the dots," said Korgel.

Once that kind of communication is achieved, quantum dots eventually could function as the interface between a wide array of new microelectronic biomedical applications, including pioneering prosthetic limbs and the neural cells of the people using them, the researchers said.