Methods and systems for extending dynamic range in assays for the detection of molecules or particles
Inventors
Rissin, David M. • Fournier, David • Duffy, David C.
Assignees
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Publication Number
US-9110025-B2
Publication Date
2015-08-18
Expiration Date
Abstract
Described herein are systems and methods for extending the dynamic range of assay methods and systems used for determining the concentration of analyte molecules or particles in a fluid sample. In some embodiments, a method comprises spatially segregating a plurality of analyte molecules in a fluid sample into a plurality of locations. At least a portion of the locations may be addressed to determine the percentage of said locations containing at least one analyte molecule. Based at least in part on the percentage, a measure of the concentration of analyte molecules in the fluid sample may be determined using an analog, intensity-based detection/analysis method/system and/or a digital detection/analysis method/system. In some cases, the assay may comprise the use of a plurality of capture objects.
Core Innovation
The invention provides a system for determining a measure of the concentration of analyte molecules or particles in a fluid sample. An assay substrate provides locations with binding surfaces, a detector produces signals indicative of analyte presence or absence as well as signal intensity, and a signal processor determines the percentage of analyte-positive locations. Based on that percentage, the processor determines concentration using either positive-location counts or signal intensity, thereby extending the analyte-concentration dynamic range.
The system applies digital positive-location counting at lower occupancy and intensity-based analog measurement at higher occupancy, with intermediate measures optionally combined. Calibration links the measurement regimes through average molecules per bead or an analog-to-digital conversion factor. In an SβG bead assay, Poisson adjustment converts the fraction of active beads to average molecules per bead to maintain linear response, and the system quantifies PSA in post-prostatectomy serum samples.
Claims Coverage
The provided relevant claims identify one independent claim, claim 1, which covers a system for determining analyte concentration using analyte-positive locations and either location counts or signal intensity, comprising 3 inventive features.
Assay substrate with analyte-bearing locations
The system comprises an assay substrate with a plurality of locations, each comprising a binding surface forming or contained within the location, with at least one analyte molecule or particle immobilized on at least one binding surface.
Detector producing location-specific signals
At least one detector addresses a plurality of locations and produces a signal indicative of the presence or absence of an analyte molecule or particle at each addressed location, with signal intensity varying with the number of analyte molecules or particles at each location.
Signal processor selecting a concentration measure
At least one signal processor determines the percentage of locations containing at least one analyte molecule or particle and, based on that percentage, determines concentration using either the number of analyte-positive locations or signal intensity indicative of multiple analyte molecules or particles.
The independent claim combines an assay substrate, detector, and signal processor to determine analyte concentration using analyte-positive location counts, signal intensity, or a selection based on the percentage of positive locations.
Stated Advantages
The assay system extends the analyte-concentration dynamic range, with reported examples of over 6-log enzyme detection and a 4-log PSA working range.
Documented Applications
Determining a measure of the concentration of analyte molecules or particles in a fluid sample, including enzyme detection.
Quantifying PSA in post-prostatectomy patient serum samples, including samples in which a leading diagnostic test did not detect PSA.
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