Crossover analytical systems and methods using an immunosensor and magnetic immunosensor

An immunoassay system for determining a concentration of an analyte in a sample over an extended concentration range, the system comprising:

• a first electrochemical sensor including an immobilized layer of antibodies configured to bind to a first complex of signal antibodies and the analyte to form a second complex;
• a second electrochemical sensor having a magnetic field disposed locally around the second electrochemical sensor, wherein the magnetic field is configured to attract magnetic beads onto a surface of the second electrochemical sensor such that a third complex of the first complex and antibodies immobilized on the magnetic beads is localized on the second immunosensor;
• a fluid comprising a substrate;
• one or more processors;
• and
• non-transitory machine readable storage medium storing a set of instructions which when executed by the one or more processors cause the one or more processors to:
• measure a first electrochemical signal at the first electrochemical sensor from a reaction of the substrate with the second complex;
• measure a second electrochemical signal at the second electrochemical sensor from a reaction of the substrate with the third complex;
• determine a first concentration of the analyte in the sample from the first electrochemical signal;
• determine a second concentration of the analyte in the sample from the second electrochemical signal;
• determine a weighted average of the first concentration and the second concentration;
• compare the weighted average of the first concentration and the second concentration to a predetermined crossover concentration zone;
• when the weighted average is greater than the crossover concentration zone, report the first concentration as a final concentration of the analyte in the sample from the first electrochemical signal;
• when the weighted average is less than the crossover concentration zone, report the second concentration as the final concentration of the analyte in the biological sample from the second electrochemical signal;
• and
• when the weighted average is within the crossover concentration zone, report the weighted average as the final concentration of the analyte in the biological sample.

A non-transitory machine readable storage medium having instructions stored thereon that when executed by one or more processors cause the one or more processors to perform a method comprising:

• measuring a first signal at a first immunosensor from a reaction of a signal agent with a first complex of signal antibodies, analyte, and capture antibodies immobilized on a surface of the first immunosensor;
• measuring a second signal at a second immunosensor from a reaction of the signal agent with a second complex of the signal antibodies, the analyte, and capture antibodies immobilized on magnetic beads that are localized on or near a surface of the second immunosensor via a magnetic field;
• determining a first concentration of the analyte in the sample from the first electrochemical signal;
• determining a second concentration of the analyte in the sample from the second electrochemical signal;
• determining a weighted average of the first concentration and the second concentration;
• comparing the weighted average of the first concentration and the second concentration to a predetermined crossover concentration zone;
• when the weighted average is greater than the crossover concentration zone, reporting the first concentration as a final concentration of the analyte in the sample from the first signal;
• when the weighted average is less than the crossover concentration zone, reporting the second concentration as the final concentration of the analyte in the biological sample from the second signal;
• and
• when the weighted average is within the crossover concentration zone, reporting the weighted average as the final concentration of the analyte in the biological sample from the first signal and the second signal.