Biomaterials use lithography to send out signals

A scientist has produced patterned surfaces on glass substrates that integrate biocompatible materials and live nerve cells using a lithographic technique called microstamping.

A University of Illinois scientist has produced patterned surfaces on glass substrates that integrate biocompatible materials and live nerve cells using a lithographic technique called microstamping.

Manipulating the attachment and growth patterns of individual nerve cells has potential application to biosensors, drug screening, implants and prosthetics.

‘Controlling tissue response is particularly important for implants, which tend to work for a while, then lose electrical sensitivity,’ said Bruce Wheeler, a UI professor of electrical and computer engineering and a researcher at the university’s Beckman Institute for Advanced Science and Technology.

‘If we can better understand and control the interface between electronic components and nerve cells, we could build more sophisticated and longer-lasting implants.’

Wheeler’s microstamping technique uses lithographic methods to precisely reproduce a master pattern with biologically relevant materials.

‘The microstamp works the same as a conventional rubber stamp except that the ink is polylysine (an artificial polymer commonly used for cell culture) and the patterns produced are measured in micrometers, or the same size as the cells themselves,’ said Wheeler.

To culture nerve cells in a dish, Wheeler worked with graduate students John Chang and Johnny Nam, as well as colleague Gregory Brewer, a professor of medical microbiology at the Southern Illinois University School of Medicine in Springfield.

The cells are chemically and mechanically separated then poured onto the patterned polylysine where they selectively attach to the surface.

‘Within a few days, the cells send out processes that explore the environment, preferring areas that have intact polylysine,’ Wheeler said. ‘The cells soon mature and begin sending electrical signals.’

Microlithographic techniques also can be used to fabricate planar microelectrode arrays. Confining the neurons to narrow tracks that intersect electrodes creates a technological basis for robust, designable neural networks useful for studying basic neuroscience or for constructing elaborate neural biosensors.

‘One problem with biomaterials growing on a micropatterned array, however, is the long-term stability and retention of biological activity,’ said Wheeler. ‘Also, because the brain has ordered layers of cells, we believe that orderly growth will lead to greater insight to brain activity, and we have had to develop techniques for maintaining the orderly growth of the neurons in culture.’

Working with UI professor Deborah Leckband, the researchers have placed a layer of polyethylene glycol to successfully reduce unwanted protein adhesion and cell growth in portions of the array.

‘The nerve cells maintained compliance to the microstamped patterns and remained viable for up to one month,’ said Wheeler.