eRapid: Antifouling Nanocomposite Coating Enables Multiplexed Electrochemical Detection of Biomarkers in Samples as Complex as Human Blood

Rising healthcare costs incentivize new clinical care models that emphasize early diagnosis, personalized health monitoring, and out-of-hospital care. Moving diagnostic testing out of hospitals and into physician offices, pharmacies, and patient homes has the potential to dramatically reduce barriers to care and help drive the critical shift from treatment to prevention. There is therefore a great need for new technologies that can enable more convenient, faster, and lower cost diagnostics.<br/>Electrochemical (EC) sensor technology is ideally suited to meet these needs as the worldwide success of the glucometer has demonstrated in the management of diabetes. However, market penetration of electronic sensors has been limited to only a handful of applications that are amenable to enzyme-based detection. The great majority of biosensing applications require the use of affinity-based sensors; however, most existing detection devices require optical readouts and/or sophisticated laboratory-based detectors that are difficult to miniaturize and integrate into portable devices. Affinity-based EC sensors exist and have much simpler electronic readouts, but their use has been limited by rapid fouling of sensor surfaces caused by non-specific adsorption of biological components in human blood, plasma, or other complex fluid samples, which dramatically limits their sensitivity and selectivity.<br/> Thus, to enable the broad use of affinity-based electrochemical sensors for diagnostic applications, we must solve this biofouling problem. In response to this challenge, we have developed a robust, low-cost, nanocomposite-based antifouling coating for multiplexed EC sensors, we call “<i>eRAPID</i>”, which enables unprecedented performance, speed, and ease of use in terms of quantitative biomarker signal detection compared to existing technologies. The eRAPID nanoporous composite coating contains conductive nanomaterials, such as gold nanowires, carbon nanotubes, or reduced graphene oxide nanoflakes integrated within a 3D porous unreactive protein matrix. Through a series of studies, we have also progressively evolved this technology to provide increased performance while simplifying process flow, reducing time, and decreasing cost. Currently, we use a localized heat-induced method for coating eRAPID on EC sensors that can be completed within the unprecedented time of &lt;1 min (at least 3 orders of magnitude faster than state-of-the-art).<br/>Importantly, we have shown that eRAPID-coated EC sensors enables both multiplexed and multichannel detection of analytes. Proof-of-concept studies with over 27 different biomarkers completed at Harvard’s Wyss Institute have demonstrated that eRapid’s technology can detect small chemicals and large biomolecules within minutes in complex fluid samples, including blood, saliva, and urine without requiring sample preparation. We leveraged these sensors to develop several multiplexed diagnostic platforms for complex diseases (e.g., sepsis, myocardial infarction, concussion, COVID-19) that require only 15 µL of blood for biomarker detection. Single-digit pg/mL sensitivity was obtained within minutes for all the biomarkers tested in unprocessed human plasma samples and whole blood, which is much faster and at least 50 times more sensitive than traditional ELISA methods, and the signal was stable enough to be measured after one week of storage. This proprietary sensor technology offers a versatile, multiplexed, cost-effective, robust, manufacturable, and scalable approach for creating multiplexed EC sensors that is adaptable to a variety of testing strategies addressing high-value diagnostic and detection challenges in multiple fields, ranging from home healthcare to industrial, environmental, and food applications.