Nanoscale device allows brain chemistry observation at smallest level

Silicon-based biosensor

It is based on silicon technology and applies microelectronics production processes. 

This tiny sensor can capture chemical content from very targeted tissue patches with about 100 percent efficiency in a fraction of a second. This characteristic is critical for accurately tracking medication distribution throughout the body.

This device is based on the microdialysis technique and uses a probe with a narrow membrane that is introduced into biological tissue. 

Within this intricate process, chemicals traverse the membrane, entering a fluid systematically pumped away for detailed analysis. 

The technique’s capability to directly sample from tissue has reverberated as a significant breakthrough, particularly influencing the realms of neuroscience, pharmacology, and dermatology.

The process of nanodialysis

“With our nanodialysis device, we take an established technique and push it into a new extreme, making biomedical research problems that were impossible before quite feasible now. Moreover, since our devices are made on silicon using microelectronics fabrication techniques, they can be manufactured and deployed on large scales,” said Yurii Vlasov, electrical & computer engineering professor and the study's co-lead.

The key innovation in nanodialysis, as highlighted in the release, lies in the ultra-slow flow rate of the fluid pumped through the device. 

This purposeful reduction in flow rate, calibrated at 1,000 times slower than typical microdialysis, is extremely significant. The deliberate slowing down of the fluid flow enables the device to capture the chemical composition of tissue from an area 1,000 times smaller than conventional techniques can achieve. 

Despite the substantial reduction in scale, the instrument captures and analyzes the precise chemical makeup of the tested tissue with an astounding 100 percent efficiency.

“By drastically decreasing the flow rate, it allows the chemicals diffusing into the probe to match the concentrations outside in the tissue,” Vlasov explained. 

“Imagine you’re adding dye to a pipe with flowing water. If the flow is too fast, the dye gets diluted to concentrations that are difficult to detect. To avoid dilution, you need to turn the water almost all the way down,” Vlasov added. 

The device fabrication

Standard microdialysis devices, manufactured using glass probes and polymer membranes, provide a substantial barrier to downsizing.

Because of the intrinsic qualities of glass and polymers, reducing the size of these devices while maintaining structural integrity and performance is challenging.

The researchers opted for a different approach to overcome this limitation and build devices suitable for nanodialysis. They relied on processes established for electrical chip fabrication, specializing in generating minute and complicated shapes on silicon surfaces.

“In addition to enabling us to go smaller, silicon technology makes the devices cheaper,” Vlasov said. 

“By putting in the time and effort to develop a fabrication process for building our nanodevices on silicon, it is now very straightforward to manufacture them at industrial scales at an incredibly low cost,” Vlasov concluded in the press release.

The findings were reported in the journal ACS Nano.