Affinity-based sensors are electrochemical devices that can detect a large variety of disease biomarkers. They typically have enzyme-coated electrodes onto which chemical biomarkers can stick, in the process changing the electrical characteristics of the device, something that can be accurately measured. Although they’re extremely sensitive, when used in practice with whole blood, they quickly become fouled by all sort of compounds. This causes them to quickly lose their effectiveness, making affinity-based electrochemical detection impractical until now.
That is because researchers at Harvard’s Wyss Institute have now developed a way to make affinity-based sensors highly resistant to biofouling. Their novel electrode coating can resist most of the chemical compounds present in whole blood while allowing for target molecules to still stick to the sensor.
The new coating is a matrix of bovine serum albumin interwoven with glutaraldehyde. It has an electrically conducting network of nanowires or carbon nanotubes. Because the matrix has pores smaller than the proteins that exist in whole blood, they cannot stick to the material. Moreover, bovine serum albumin has a weak negative charge, which doesn’t let positively charged biomolecules to stick well to it.
The coating was tried in an affinity-based sensor and it managed to maintain the sensor’s function at more than 90% after being submerged within biofluids for an entire month. Previously, such a sensor would be useless when exposed to blood for about a day.
To actually make the device functional and not just resistant to most blood-borne molecules, the Wyss team added antibodies to the coating and used a so-called “sandwich assay” to detect the electrical signal when the antibody binds to its target. This was tried with antibodies for interleukin 6 (IL6), insulin, or glucagon, which are all important biomolecules, and the device performed exceptionally well.
The researchers believe that their technology will allow for point-of-care diagnostic devices that look and function like today’s widely available glucometers.
Here’s a Wyss Institute video report explaining the technology:
Study in Nature Nanotechnology: An antifouling coating that enables affinity-based electrochemical biosensing in complex biological fluids
Via: Wyss Institute