Anna K. Keshek

Lead and mercury are among the most dangerous environmental pollutants due to their high toxicity to humans and other living organisms. They are also ubiquitous in our ecosystems as a result of industrial waste. Therefore, it is essential to develop a simple and inexpensive method to rapidly detect low concentrations of these metals in various liquids, including wastewater. Aptamer-based electrolyte-gated organic field-effect transistors (EGOFETs), which are traditionally used to detect large biomolecules such as viruses and proteins, are a promising concept for heavy-metal detection. To achieve this, we chose several aptamers with high affinity for and specificity to Pb²⁺ and Hg²⁺ ions, determined the dissociation constants and stoichiometry of the complexes, investigated the kinetics of complex formation and cross-specificity and proposed structures for the aptamer–cation complexes. Based on these aptamers, we developed EGOFET-based aptasensors for Pb²⁺ and Hg²⁺. The fabricated EGOFET devices have been shown to be sensitive to low concentrations of lead (from 30 nM to 2.5 μM) and mercury (from 250 nM to 2.5 μM) cations. These ranges correspond to the maximum permissible concentrations in drinking and wastewater for lead, which are 144 nM and 1.2 μM, respectively, and exceed the range of maximum permissible concentration in drinking and wastewater for mercury, which is 5 nM. Despite this, it was possible to detect mercury cations at a concentration of 5 nM within five minutes in a model system that simulates liquid flow using the EGOFET device. This demonstrates the potential for fast and selective detection of Pb²⁺ and Hg²⁺ ions at maximum permissible concentrations in drinking water using EGOFET-based aptasensors. This is a significant step forward in the development of flow sensors for detecting heavy metals in liquid media.

EGOFET-based aptasensor with a single recognition element for multitarget detection on a single chip.

Nowadays, biosensor platforms based on various organic electrolytic transistors are in great demand due to their ability to specifically determine a wide range of biological analytes with extreme sensitivity. The main drawback of such platforms is their disposability at relatively high costs, preventing widespread application. In this work, we elaborate and successfully demonstrate a proof of concept for a universal approach for the fabrication of a reusable EGOFET-based aptasensor using polymer track-etched membranes as cheap disposable elements for biorecognition layers. We defined the most suitable pore size of track-etched membranes, which was enough for the penetration of viral particle and their capture near the current-carrying layer of EGOFET. The sensitivity of the fabricated EGOFET-based aptasensor to influenza A virus was comparable with disposal EGOFET-based biosensors having a biorecognition layer placed directly on the semiconducting layer. The limit of detection of the fabricated device was 8 × 10⁴ VP mL⁻¹, which was superior to those of antibody-based rapid analysis test systems (1 × 10⁶–4 × 10⁸ VP mL⁻¹) but inferior to those of the PCR method (3 × 10²–1.2 × 10³ VP mL⁻¹). The elaborated approach paves the way for the simple development of universal point-of-care tools consisting of rapid, non-invasive miniaturized sensors for the detection of a wide range of analytes, which are recognizable by aptamers.

Elaboration of biosensors on the base of organic transistors with embedded biomolecules which can operate in an aqueous environment is of paramount importance. Electrolyte-gated organic field-effect transistors demonstrate high sensitivity in detection of various analytes. In this paper, we demonstrated the possibility of quantitative fast specific determination of virus particles by an aptasensor based on EGOFET. The sensitivity and selectivity of the devices were examined with the influenza A virus as well as with control bioliquids like influenza B, Newcastle disease viruses or allantoic fluid with different dilutions. The influence of the semiconducting layer thickness on EGOFETs sensory properties is discussed. The fabrication of a multi-flow cell that simultaneously registers the responses from several devices on the same substrate and the creation of a multi-sensor flow device are reported. The responses of the elaborated bioelectronic platform to the influenza A virus obtained with application of the portable multi-flow mode are well correlated with the responses obtained in the laboratory stationary mode.

Rapid and reliable techniques for virus identification are required in light of recurring epidemics and pandemics throughout the world. Several techniques have been distributed for testing the flow of patients. Polymerase chain reaction with reverse transcription is a reliable and sensitive, though not rapid, tool. The antibody-based strip is a rapid, though not reliable, and sensitive tool. A set of alternative tools is being developed to meet all the needs of the customer. Surface-enhanced Raman spectroscopy (SERS) provides the possibility of single molecule detection taking several minutes. Here, a multiplex lithographic SERS aptasensor was developed aiming at the detection of several respiratory viruses in one pot within 17 min. The four labeled aptamers were anchored onto the metal surface of four SERS zones; the caught viruses affect the SERS signals of the labels, providing changes in the analytical signals. The sensor was able to decode mixes of SARS-CoV-2 (severe acute respiratory syndrome coronavirus two), influenza A virus, respiratory syncytial virus, and adenovirus within a single experiment through a one-stage recognition process.