Cell Phone Camera Nucleic Acid Detection via Colorimetric Ratiometry
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Solution Overview
Problem
Current point-of-care nucleic acid detection methods in limited resource settings lack affordability, sensitivity, and user-friendliness, with existing ultrasensitive techniques requiring skilled technicians and laboratory settings, while visual readouts for digital single-molecule isothermal amplification are constrained by the need for fluorescent signals and precise measurement.
Innovation Solution
A method utilizing an unmodified cell phone camera for visual detection of nucleic acid amplification by dividing samples into compartments, performing amplification reactions, exposing reaction products to indicators, and determining intensity ratios between colors in images, enabling a robust and quantitative visual readout without modifications to the camera.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fluorescent readout methods are used for digital single-molecule amplification, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses colorimetric indicators that change color in response to amplification products, allowing detection with standard unmodified cell phone cameras. The ratiometric analysis of color changes (e.g., green/red ratio) provides quantitative measurement without requiring fluorescent markers or specialized imaging equipment.
Solution Approach 2:
The patent creates a visual copy of the amplification signal through color changes that can be captured by standard camera sensors. Instead of relying on fluorescent emission that requires specialized detection, the method converts the molecular amplification signal into a visible color change that replicates the detection capability using ordinary photography.
2Measurement precision
If quantitative measurement methods are used for nucleic acid detection, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The system performs automated image capture and ratiometric analysis through software processing. The cell phone automatically captures the color image, and the embedded software calculates the intensity ratios and determines amplification results without requiring manual color matching or complex user interpretation, making quantitative analysis as easy as taking a photograph.
Solution Approach 2:
The patent replaces manual visual assessment and subjective color comparison with automated digital image processing. The software algorithm objectively measures color intensities, calculates ratios, and determines results, eliminating the need for trained technicians to perform subjective visual evaluations while maintaining quantitative precision.
3Ease of operation
If standard cell phone cameras are used for detection, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The patent changes the detection parameter from fluorescent intensity (which requires specialized equipment) to color intensity ratios (which can be measured by standard camera sensors). By measuring the ratio of green to red channel intensities in the captured image, the system achieves quantitative precision comparable to specialized equipment while using only a standard cell phone camera.
Solution Approach 2:
Instead of relying on the intensity dimension alone (which is sensitive to lighting variations), the patent introduces a ratio dimension by comparing multiple color channels (green/red or blue/red ratios). This additional dimensional approach to measurement compensates for the limitations of standard camera sensors and provides robust quantitative data even with variable lighting conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for ultrasensitive and quantitative detection of nucleic acid molecules using an unmodified cell phone camera, facilitating global distribution of diagnostic tests into limited resource settings with a simple, cost-effective, and user-friendly method for visualizing single nucleic acid molecule amplification.
Implementation Method 1
exposing the reaction product to an amplification indicator; obtaining a color image of the reaction product
Implementation Method 2
determining a plurality of first intensities for a first color of the color image; determining a plurality of second intensities for a second color of the color image; and determining a ratio between the first color intensity and the second color intensity
Data Source
AI summary
The present invention relates to methods, computer readable medium and systems for detecting and counting single nucleic acid molecules confined in nanoliter volumes using an unmodified camera, such as a cell phone camera. In particular, it identifies colorimetric amplification-indicator dyes that are compatible with the spectral sensitivity of standard mobile phones. The invention further provides an optimal ratiometric image-process for a selected dye to achieve a readout that is robust to lighting conditions and camera hardware and provides unambiguous quantitative results, even for colorblind users.