Diagnostic test using gated measurement of fluorescence from quantum dots

1 . A rapid diagnostic test system comprising:

a light source for illuminating a medium containing a sample under test, wherein the medium comprises a labeling substance that binds a quantum dot to a target analyte;

a first photodetector positioned to measure light from a test area of the medium; and

a control system coupled to the light source and the photodetector, wherein the control system executes a measurement processes including processing a measurement signal from the photodetector that indicates a light intensity after the light source has been off for a time.

2 . The system of claim 1 , wherein the light that the first photodetector measures has a frequency characteristic of fluorescent light from the quantum dot.

3 . The system of claim 2 , wherein the medium comprises a lateral-flow strip for performing a binding assay, and the test area contains an immobilized substance that binds to and holds a complex including the labeling substance and the target analyte.

4 . The system of claim 1 , wherein the control system processes multiple measurements from the photodetector that indicate the light intensity after the light source has been off for the time.

5 . The system of claim 1 , further comprising:

a second photodetector; and

an optical system positioned to receive light from the test area, wherein the optical system separates light having a first frequency from light having a second frequency so that the first photodetector measures light having the first frequency and the second photodetector measures light having the second frequency.

6 . The system of claim 5 , wherein the optical system comprises a diffractive element that directs the light of the first frequency on the first photodetector and directs the light of the second frequency on the second photodetector.

7 . The system of claim 5 , wherein the optical system comprises a color filter that transmits light having one of the first and second frequencies and reflects light having the other of the first and second frequencies.

8 . The system of claim 6 , wherein the quantum dot emits fluorescent light having the first frequency; and wherein the medium further comprises a second labeling substance containing a second quantum dot emits fluorescent light having the second frequency.

9 . The system of claim 1 , wherein the first photodetector comprises a portion of an imaging array that captures an image containing the test area of the medium.

10 . The system of claim 1 , wherein the first photodetector and the medium are contained in a single-use module.

11 . A process for rapid diagnostic testing, comprising:

applying a sample to a medium containing a labeling substance that binds a quantum dot to a target analyte;

illuminating a portion of the medium with light capable of causing the quantum dot to fluoresce;

stopping illumination of the portion of the medium;

measuring light from the portion of the medium after the illumination remains stopped for a delay time; and

determining a test result from the measuring of the light.

12 . The process of claim 11 , further comprising repeating the illuminating, stopping illumination, and measuring steps a plurality of times, wherein determining the test result uses results from each repetition of measuring the light.

13 . The process of claim 12 , wherein the measuring step is repeated at a frequency between about 1 MHz and about 200 MHz.

14 . The process of claim 11 , wherein the medium is in a single-use structure that includes a photodetector that measures light from the quantum dot.

15 . The process of claim 1 1 , further comprising activating a display on the single-use module to indicate the test result signal.

16 . The process of claim 11 , further comprising producing an electrical signal that is output from the single-use structure.