Rapid,
yet accurate and sensitive testing has been shown to be
critical in the control of spreading pandemic diseases such as COVID-19.
Current methods which are highly sensitive and can differentiate different
strains are slow and cannot be conveniently applied at the point of
care. Rapid tests, meanwhile, require a high titer and are not sufficiently
sensitive to discriminate between strains. Here, we report a rapid
and facile potentiometric detection method based on nanoscale, three-dimensional
molecular imprints of analytes on a self-assembled monolayer (SAM),
which can deliver analyte-specific detection of both whole virions
and isolated proteins in microliter amounts of bodily fluids within
minutes. The detection substrate with nanoscale inverse surface patterns
of analytes formed by a SAM identifies a target analyte by recognizing
its surface nano- and molecular structures, which can be monitored
by temporal measurement of the change in substrate open-circuit potential.
The sensor unambiguously detected and differentiated H1N1 and H3N2
influenza A virions as well as the spike proteins of severe acute
respiratory syndrome coronavirus 2 (SARS-CoV-2) and Middle-East respiratory
syndrome (MERS) coronavirus in human saliva with limits of detection
reaching 200 PFU/mL and 100 pg/mL for the viral particles and spike
proteins, respectively. The demonstrated speed and specificity of
detection, combined with a low required sample volume, high sensitivity,
ease of potentiometric measurement, and simple sample collection and
preparation, suggest that the technique can be used as a highly effective
point-of-care diagnostic platform for a fast, accurate, and specific
detection of various viral pathogens and their variants.
The realization of a high-throughput biosensor platform with ultrarapid detection of biomolecular interactions and an ultralow limit of detection in the femtomolar (fM) range or below has been retarded due to sluggish binding kinetics caused by the scarcity of probe molecules on the nanostructures and/or limited mass transport. Here, as a new method for the highly efficient capture of biomolecules at extremely low concentration, we tested a three-dimensional (3D) platform of a bioelectronic field-effect transistor (bio-FET) with vertically aligned and highly dense one-dimensional (1D) ZnO nanorods (NRs) as a sensing surface capped by an ultrathin TiO2 layer for improved electrolytic stability on a chemical-vapor-deposited graphene (Gr) channel. The ultrarapid detection capability with a very fast response time (∼1 min) at the fM level of proteins in the proposed 3D bio-FET is primarily attributed to the fast binding kinetics of the probe-target proteins due to the small diffusion length of the target molecules to reach the sensor surface and the substantial number of probe molecules available on the largely increased surface area of the vertical ZnO NRs. This new 3D electrical biosensor platform can be easily extended to other electrochemical nanobiosensors and has great potential for practical applications in miniaturized biosensor integrated systems.
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