Gold Standard Biosensor on a Budget

The advent of portable biosensor platforms has sparked a transformative shift in the field of diagnostics, enabling rapid and mobile detection of diverse analytes. These platforms commonly integrate biological recognition elements such as enzymes, antibodies, or nucleic acids with transducers to convert biochemical interactions into measurable signals. This marriage of biotechnology and electronics enables the detection of target molecules with high specificity and sensitivity, making them invaluable tools in a wide range of applications.

One significant application of portable biosensor platforms is in the field of healthcare diagnostics. These devices can be used for point-of-care testing, allowing for quick and accurate diagnosis of diseases such as infectious diseases, chronic conditions, and cancer. For example, portable biosensors can detect specific biomarkers associated with diseases like HIV, malaria, or diabetes from a drop of blood or saliva within minutes, enabling timely intervention and treatment.

One of the main advantages of portable biosensor platforms over traditional diagnostic methods is their portability and ease of use. Unlike centralized laboratory-based assays, which require specialized equipment and trained personnel, portable biosensors are compact, lightweight, and user-friendly, allowing for testing to be performed at the point of need, whether it is a remote clinic, field site, or patient's home.

Most portable biosensing devices share some limitations that hinder their utility, however. These systems are often costly, and in some cases they can be lacking in sensitivity. These limitations may soon be a thing of the past, however, thanks to the work of a team at the Institute of Radiopharmaceutical Cancer Research in Germany. They have developed a portable, palm-sized device that can perform up to 32 analyses on a single sample. And because of some clever design decisions, this device is inexpensive and highly sensitive.

For sensing, the system leverages an extended gate field-effect transistor (EGFET), using a well-known principle of operation. As an electrical current flows between the source and drain of the EGFET, electrical potential at the gate can alter its rate of flow. So by modifying the gate such that it can bind biological molecules of interest, the flow of current can be manipulated in predictable ways. In this way, one level of current might signal the presence of a flu virus, and another might signal its absence.

Traditionally, the gates themselves are modified to bind biological molecules, which means the biosensors are good for only a single use, after which they must be disposed of. This not only increases costs — a separate transistor must be used for each detected molecule, and then must be discarded after use — but also has negative environmental consequences. In this work, the researchers instead modified electrodes to bind the molecules, and the electrodes are then connected to the gate. As such, only the electrodes need to be replaced after use. Moreover, a multiplexing system was deployed that allows all of the electrodes to be evaluated, in turn, by a single transistor, dramatically cutting down the number of EGFETs needed by a large biosensor.

Another enhancement was made to the device with the help of gold nanoparticles. These nanoparticles are capable of concentrating or localizing an electrical charge, which amplifies the voltage signal and increases detection sensitivity. A five-fold amplification in signals was seen using this approach. This resulted in sensitivity levels that exceeded many of the best existing EGFET-based biosensing devices. This performance was achieved despite using only off-the-shelf electronic components and relatively simple production methods.

Given the unique properties of this novel biosensing platform, the team sees a bright future for their technology. They are presently looking for partners to help them commercialize their system.