Combined Immunoassay and Magnetic Immunoassay Methods for Extended Range of Sensitivity

A method for determining a concentration of a target analyte in a sample, the method comprising:

• introducing the sample into a sample chamber of a sensing device;
• moving the sample from the sample chamber to a conduit of the sensing device, the conduit comprising a sensor chip, wherein the sensor chip includes a first immunosensor having an immobilized layer of capture antibodies configured to bind to the target analyte, and a second immunosensor having a magnetic field localized around the second immunosensor;
• forming a first complex and a second complex in the sample, wherein the first complex
• includes signal antibodies and the target analyte, and the second complex includes the first complex and capture antibodies immobilized on magnetic beads;
• contacting the first immunosensor with the sample comprising the first complex and the second complex to form a third complex localized on or near a surface of the first immunosensor, wherein the third complex includes the first complex bound to the immobilized capture antibodies;
• contacting the magnetic field localized around the second immunosensor with the sample comprising the first complex and the second complex such that the second complex is localized on or near a surface of the second immunosensor;
• applying a substrate to the first immunosensor and the second immunosensor;
• measuring a first signal at the first immunosensor from a reaction of the substrate with the signal antibodies in the third complex that are localized on or near the surface of the first immunosensor;
• measuring a second signal at the second immunosensor from a reaction of the substrate with the signal antibodies in the second complex that are localized on or near the surface of the second immunosensor;
• determining a first concentration of the analyte in an upper concentration range based on the first signal;
• determining a second concentration of the analyte in a lower concentration range based on the second signal;
• calculating a weighted average of the first and the second concentrations;
• and
• based on the weighted average and a predetermined crossover point, determining the concentration of the target analyte in the sample as:
• the first concentration when the weighted average is more than the predetermined crosspoint, or
• the second concentration when the weighted average is less than the predetermined crossover point.

A non-transitory machine readable storage medium having instructions stored thereon, which, when executed by one or more processors, cause the one or more processors to perform a method for determining a concentration of a target analyte in a sample, the method comprising:

• moving a sample from a sample chamber to a conduit comprising a sensor chip, a first dry reagent, and a second dry reagent, wherein the moving results in the first dry reagent and the second dry reagent dissolving into the sample and forming a first complex and a second complex, the first complex including signal antibodies and the target analyte, and the second complex including the first complex and capture antibodies immobilized on magnetic beads, and wherein the sensor chip includes a first immunosensor having an immobilized layer of capture antibodies configured to bind to the target analyte, and a second immunosensor having a magnetic field localized around the second immunosensor;
• moving the sample into contact with the first immunosensor, such that the first complex and the second complex form a third complex localized on or near a surface of the first immunosensor, wherein the third complex includes the first complex bound to the immobilized capture antibodies;
• moving the sample into contact with the magnetic field localized around the second immunosensor with the sample comprising the first complex and the second complex, such that the second complex is localized on or near a surface of the second immunosensor;
• moving a substrate into contact with the first immunosensor and the second immunosensor;
• measuring a first signal at the first immunosensor from a reaction of the substrate with the signal antibodies in the third complex that are localized on or near the surface of the first immunosensor;
• measuring a second signal at the second immunosensor from a reaction of the substrate with the signal antibodies in the second complex that are localized on or near the surface of the second immunosensor;
• determining a first concentration of the analyte in an upper concentration range based on the first signal;
• determining a second concentration of the analyte in a lower concentration range based on the second signal;
• calculating a weighted average of the first and the second concentrations;
• and
• based on the weighted average and a predetermined crossover point, determining the concentration of the target analyte in the sample as:
• the first concentration when the weighted average is more than the predetermined crosspoint, or
• the second concentration when the weighted average is less than the predetermined crossover point.