GUANINE HAS REVOLUTIONIZED ELECTROCHEMICAL DETECTION
Electrochemical detection is a widely used technique to detect redox materials such as glucose and metals. A voltammetry method changes the chemical state of the redox material and produces an electrical signal that is measured with a sensor. Electrochemical detection is fast, easy to use, inexpensive, quantitative and mobile. Commercial instruments such as the Abbott iSTAT simultaneously detect multiple redox chemicals and glucose from the same sample.
Redox materials also include nucleotides such as guanine. Specific DNA, RNA and gene sequences can be detected by hybridizing targets with complementary probes bound to the electrode surface on a sensor. When voltage is applied guanine molecules oxidize and emit electrons to the electrode which produce an electrical current. The specific nucleic acid target is determined to be present when the peak current exceeds a threshold value from electrical noise.
Nucleic acid sensors are rarely used commercially since their detection limits are not capable of measuring low levels needed for clinical use. Attempts have been made to improve the signal-to-noise resolution using sensor electrodes made from nanomaterials such as carbon nanotubes. However nanosensors are expensive to manufacture, have a low production yield, and their signals are highly variable from electrode-to-electrode due to manufacturing inconsistencies.
Redox tags are an alternative approach for electrochemical detection. Redox tags such as ferrocene can be bound to targets instead of conventional optical tags. Low detection limits are achieved by replicating nucleic acid targets in advance of detection. GenMark increases bacteria targets using PCR. Its blood pathogen assay employs a 5 hour multiplex PCR stage following a 12 hour culture to detect a high number of bacteria and antimicrobial resistance markers. Cue Health replicates COVID-19 targets using isothermal amplification with a redox substrate to detect COVID RNA in a 20 minutes process. Because of the high number of primers used in isothermal amplification, it may not be feasible to detect multiplex targets or to quantify target concentrations.
Guanine Inc. takes a different approach to detect multiple targets at low detection limits while maintaining all of the benefits achieved from electrochemical detection. Guanine invented the oligonucleotide tag (synthetic DNA) that binds specific detection targets with millions of tags on a microparticle. This amplifies detection signals without using PCR or isothermal replication. The oligonucleotide tags contain a 70 mer capture sequence for rapid and specific hybridization, and a 20 mer detection sequence from a string of G, A, T or C to produce unique oxidation peaks on a common electrode. Multiple electrodes and microparticle conjugates enable high multiplexing from a single sample.
Redox materials also include nucleotides such as guanine. Specific DNA, RNA and gene sequences can be detected by hybridizing targets with complementary probes bound to the electrode surface on a sensor. When voltage is applied guanine molecules oxidize and emit electrons to the electrode which produce an electrical current. The specific nucleic acid target is determined to be present when the peak current exceeds a threshold value from electrical noise.
Nucleic acid sensors are rarely used commercially since their detection limits are not capable of measuring low levels needed for clinical use. Attempts have been made to improve the signal-to-noise resolution using sensor electrodes made from nanomaterials such as carbon nanotubes. However nanosensors are expensive to manufacture, have a low production yield, and their signals are highly variable from electrode-to-electrode due to manufacturing inconsistencies.
Redox tags are an alternative approach for electrochemical detection. Redox tags such as ferrocene can be bound to targets instead of conventional optical tags. Low detection limits are achieved by replicating nucleic acid targets in advance of detection. GenMark increases bacteria targets using PCR. Its blood pathogen assay employs a 5 hour multiplex PCR stage following a 12 hour culture to detect a high number of bacteria and antimicrobial resistance markers. Cue Health replicates COVID-19 targets using isothermal amplification with a redox substrate to detect COVID RNA in a 20 minutes process. Because of the high number of primers used in isothermal amplification, it may not be feasible to detect multiplex targets or to quantify target concentrations.
Guanine Inc. takes a different approach to detect multiple targets at low detection limits while maintaining all of the benefits achieved from electrochemical detection. Guanine invented the oligonucleotide tag (synthetic DNA) that binds specific detection targets with millions of tags on a microparticle. This amplifies detection signals without using PCR or isothermal replication. The oligonucleotide tags contain a 70 mer capture sequence for rapid and specific hybridization, and a 20 mer detection sequence from a string of G, A, T or C to produce unique oxidation peaks on a common electrode. Multiple electrodes and microparticle conjugates enable high multiplexing from a single sample.
TECHNOLOGY OVERVIEW
Guanine has re-invented electrical detection using synthetic DNA tags that will revolutionize accurate, mobile detection of multiple infections.
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SIMPLE TEST PROCESS
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Detection employs simple steps that can be conducted in minutes in a test cartridge that captures targets after onboard lysing, magnetic separation and electrochemical detection.
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Samples are lysed and targets are captured by magnetic particles
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Particle-target complexes for proteins and nucleic acids are magnetically separated and form sandwiches on electrodes
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Tags composed of majority guanine, adenine, thymine or cytosine generate peaks at different voltage potentials
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SIGNAL AMPLIFICATION
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Signal amplification is achieved by binding analytes with a magnetic particle conjugated with millions of guanine-rich oligonucleotide tags instead of replicating millions of copies.
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CONFIGURABLE LIMIT OF
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Limit of detection is configured for the intended use since bigger particles bind more tags to produce a stronger signal for measuring lower limit of detection.
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MULTIPLEXING
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Voltage generates a current peak if the pathogen is present. A bigger particle with more tags produces a stronger signal for lower limit of detection. A sensor can detect up to 24 targets per sample using 6 working electrodes that can each detect 4 groups of unique tag signals.
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QUANTIFICATION
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Detection tags bind to targets and produce an electrical current peak proportional to the quantity of targets in the sample. The burst is bigger when tags comprise a 20 Guanine sequence that is prefabricated into quadruplexes (planes of 4 guanine separated by Na+ cations) that generate 8-oxoguanine oxidation peaks.
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AI MODULES
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Guanine’s detection platform can be integrated with AI modules to provide cost and time savings in medical diagnosis. Modules can assist by assessing symptoms and recommending what tests are appropriate, enabling patients to supply their symptoms and history by answering specific queries, providing a preliminary diagnosis that can link symptoms with the test results, and learning new diagnostic rules by assessing multiple patient factors.
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PUBLICATION |
Carbapenem-Resistant Enterobacteriaceae Testing in 45 Minutes using an Electronic Sensor Gordon, N., Bawa, R., Palmateer, G., Rajabi, M., Gordon J.B., Kotb, N.M., Balasubramaniyam, R, Gordon, B.R. Advances in Therapeutics, Diagnostics and Applications. Volume 4, Chapter 26, Jenny Stanford Publishers, Singapore (2022) (in press) Download Universal Bioanalyte Signal Amplification for Electrochemical Biosensor Gordon, N. Biosensors J 5: 135 (2016) Download Highly Sensitive Bacteria Quantification Using Immunomagnetic Separation and Electrochemical Detection of Guanine-Labeled Secondary Beads Jayamohan, H. Gale, B.K,. Minson, B.J., Lambert, C.J., Gordon, N., Sant, H.J. Sensors, 15, 12034–12052 (2015). Download |
