Reliable diagnostics at your fingertips

Biomarkers are components that may be present in biological samples and are linked to specific diseases. Therefore, doctors can analyze biological samples from a patient to check their health or to monitor the progress of a specific treatment. Typically, these samples must be purified and diluted before analysis, and current medical diagnostic techniques rely on healthcare facilities and laboratories for these routine analyses. It is a time-consuming process that requires trained personnel and expensive instruments to extract, transport, store, process and analyze samples in centralized locations. Moreover, in times of global crisis such as the current pandemic, the pressure of thousands of requests for analyzes can saturate and collapse the health system.

On the other hand, point-of-care devices, which are small automated instruments, are capable of performing diagnostics in decentralized locations and can provide quick responses. An example of such a device is the blood glucose meter that people with diabetes use to monitor their blood sugar levels. These devices can overcome the inherent limitations of processing a sample through a centralized system, allowing anyone to monitor their health from home, using just a tiny blood sample extracted with a finger prick.

However, the development of these devices has been hampered by the technical challenges of measuring biological samples. Biomarkers of some diseases and infections are present in samples only in very small quantities, which in turn imposes the challenge of developing extremely sensitive detection techniques. While increasing the surface area of ​​the biosensor can increase the sensitivity of the instrument, these surfaces tend to quickly become clogged and contaminated, rendering them unusable.

To this end, the team led by Professor CHO, Yoon-Kyoung at the Center for Soft and Living Matter within the Institute of Basic Sciences (IBS) in Ulsan, South Korea, recently developed a biosensor using a method for generating nanostructured and nanoporous surfaces. This combined strategy not only gives the sensor unprecedented sensitivity, but also makes it resistant to protein fouling.

While there was previously no known method to reliably create electrodes using such nanostructured and nanoporous substrates, the team reported a simple method to generate such materials. The mechanism is based on the application of electrical pulses to a flat gold surface in the presence of sodium chloride and a surfactant capable of forming micelles in solution. These electrical pulses drive a preferential reaction to etch and redeposit gold from the surface and, in turn, grow nanostructures and form the nanopores (Figure 1). The use of surfactant in the form of micelles is essential to the success of this strategy since it prevents the material being etched from diffusing during the process, so it can be redeposited.

The formation of these nanostructures yielded a large surface area which was beneficial for increasing assay sensitivity, whereas the formation of nanopore substrates was ideal for preventing contamination of biological samples. The combined advantages of nanostructures and nanopores were key to the success of this strategy, which could be applied to the direct analysis of clinical plasma samples.

The researchers further demonstrated this new technology by constructing a biosensor for the detection of prostate cancer. The electrode was sensitive enough to distinguish between a group of prostate cancers and healthy donors using only a tiny amount of blood plasma or urine samples. No dilution or pre-treatment steps were used, meaning the technology could easily be used for point-of-care cancer diagnosis.

Professor Cho said: “We believe this technology is essential for the future development of point-of-care devices and diagnostic tests that work with biological samples. The ability to detect low concentrations of relevant biomarkers with robust performance opens the door to possibilities in the field of diagnosis of cancer, pathogens and other diseases.

The results of this research were published in Advanced Materials (IF: 30.849) on May 17and2022 and the associated illustration has been selected for the frontispiece of the current issue.

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