A nanobody-functionalized organic electrochemical transistor for the rapid detection of SARS-CoV-2 and MERS antigens at the physical limit

Abstract

The COVID-19 pandemic highlights the need for rapid protein detection and quantification at the single-molecule level in a format that is simple and robust enough for widespread point-of-care applications. We here introduce a modular nanobody-organic electrochemical transistor architecture that enables the fast and specific detection and quantification of single-molecule to nanomolar protein antigen concentrations in complex bodily fluids. The sensor combines a new solution-processable organic semiconductor material in the transistor channel with the high-density and orientation-controlled bioconjugation of nanobody fusion proteins on disposable gate electrodes. It provides results after a 10 minutes exposure to 5 µL of unprocessed samples, maintains high specificity and single-molecule sensitivity in human saliva or serum, and is rapidly reprogrammed towards any protein target for which nanobodies exist. We demonstrate the use of this highly modular platform for the detection of green fluorescent protein, SARS-CoV-1/2, and MERS-CoV spike proteins and validate the sensor for COVID-19 screening in unprocessed clinical nasopharyngeal swab and saliva samples.

Sensing of COVID-19 spike protein in nasopharyngeal samples using a portable surface plasmon resonance diagnostic system

“…4 With a cycle threshold (Ct) cut off correlating to Ct = 28 in the best cases, concerns regarding the high frequency of false negative results raised research efforts in finding alternative strategies to real-time RT-qPCR tests. A large number of electrical and electrochemical approaches have been proposed as point-of-care strategies, [5][6][7][8] with an original COVID-19 detection using an organic electrochemical transistor. 7 The combination of a solution-processable conjugated polymer as transistor channel together with nanobody-SpyCatcher fusion protein surface receptors allowed SARS-CoV-2 spike protein (S1) detection in nasopharyngeal swab samples of different viral loads.…”

“…A large number of electrical and electrochemical approaches have been proposed as point-of-care strategies, [5][6][7][8] with an original COVID-19 detection using an organic electrochemical transistor. 7 The combination of a solution-processable conjugated polymer as transistor channel together with nanobody-SpyCatcher fusion protein surface receptors allowed SARS-CoV-2 spike protein (S1) detection in nasopharyngeal swab samples of different viral loads. 7 Similar to other coronaviruses, the surface of SARS-CoV-2 is decorated with spike glycoproteins that bind host angiotensin-converting enzyme 2 (ACE2) receptors to mediate the fusion of viral and host cell membranes.…”

“…7 The combination of a solution-processable conjugated polymer as transistor channel together with nanobody-SpyCatcher fusion protein surface receptors allowed SARS-CoV-2 spike protein (S1) detection in nasopharyngeal swab samples of different viral loads. 7 Similar to other coronaviruses, the surface of SARS-CoV-2 is decorated with spike glycoproteins that bind host angiotensin-converting enzyme 2 (ACE2) receptors to mediate the fusion of viral and host cell membranes. 9 Targeting the spike glycoprotein is considered a direct way to measure the COVID-19 infectivity state of a patient, [10][11][12] which is different from the most commercial antigen kits targeting the nucleocapsid protein.…”

Fast‐Scanning Potential‐Gated Organic Electrochemical Transistors for Highly Sensitive Sensing of Dopamine in Living Rat Brain

“…[11] The efficient coupling between ionic and electronic charges within the semiconducting channel substantially enables OECTs to hold tremendous potential in highly sensitive sensing. [12] To this end, OECT-based (bio)sensors have emerged as a powerful platform for chemical sensing [13] and electrical signal recording [14] because of their signal amplification capability, subvolt operation regimes, and biocompatibility. Very recently, miniaturized OECT arrays and fiber-shaped OECTs have been developed into implantable OECT devices.…”

Ionic-Liquid Induced Morphology Tuning of PEDOT:PSS for High Performance Organic Electrochemical Transistors

“…Organic electrochemical transistors (OECTs) with the capability of transducing biological and ionic signals to electronic output have attracted significant attention in various applications such as neuromorphics [1,2] , biosensors [3][4][5][6] , digital logic circuits [7] , and chemical sensors [8,9] . The attractive features of OECTs for these applications are their low operating voltage (< 1 V), high transconductance (~mS) and enabling an amiable interface with cells and biological systems in water-based electrolytes.…”