One of the longstanding challenges in biomedical research is the monitoring of brain chemistry and tracking of the spread of drugs through the body. Since these procedures require much smaller and more precise sensors, microdialysis-based sensing is typically used. Such capabilities allow the new nanoscale device to outperform standard technologies.
Disadvantages of Microdialysis
Microdialysis is a minimally-invasive sampling technique which is used in exploring and monitoring the chemistry of biological tissues. It is a helpful technique in neuroscience because it allows experts to investigate and understand the complex brain functions.
In using this technique, a thin-membrane probe is insured into a living tissue. Chemicals are then passed through the membrane into a fluid which is pumped away for analysis. This ability of sampling the tissue directly also benefits other areas like dermatology and pharmacology.
However, traditional microdialysis has some limitations. Since the probes can only sample from a few square millimeters, they can only measure the average chemical composition over larger regions in the tissue.
The large size also causes tissue damage when the probe is inserted, potentially damaging the analysis results. Aside from this, the fluid pumped through the probe flows at a high rate, affecting the accuracy and efficiency with which the concentration can be read. Standard microdialysis devices are also made from glass probes and polymer membranes which make them hard to miniaturize.
Experts believe that the problems in using traditional microdialysis can be addressed by using a much smaller device. Performing the technique at nanoscale is believed to be more precise and causes less damage from the location of the tissue. As a result, chemically mapping the tissue can be done with higher spatial resolution, and a faster readout time enables a more detailed image of the changes in tissue chemistry.
New Sensor for Brain Chemistry Analysis
As a response to this challenge, experts from the University of Illinois Urbana-Champaign developed a silicon-based device which takes advantage of techniques for microelectronics manufacturing. The details of this new technology is described in the paper "Highly Localized Chemical Sampling at Subsecond Temporal Resolution Enabled with a Silicon Nanodialysis Platform at Nanoliter per Minute Flows."
The device is a nanoscale sensor which is small enough to collect chemical content of tissues close to 100% efficiency from highly localized regions in just a fraction of a second. It can monitor areas of the body which are 1,000 times smaller than current technology. It can also track subtle changes in the chemical composition of biological tissue with sub-second resolution. Since the sensor is made from silicon using microelectronics fabrication techniques, it can be manufactured and deployed on large scales.
Unlike microdialysis, nanodialysis allows ultra-slow flow rate of the fluid to be pumped through the probe. It makes the flow rate 1,000 times slower, enabling the capture of tissue chemistry from a smaller area with higher efficiency. It also permits chemical diffusion to match the concentrations outside the tissue.
In building suitable devices for nanodialysis, the research team developed techniques for electronic chip manufacturing to allow creation of a device based on silicon. Silicon technology enables manufacturers to not only make devices smaller, but also cheaper.
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