Colorimetric SARS-CoV-2 Biosensor Using Gold Nanoparticles
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Solution Overview
Problem
Current COVID-19 diagnostic methods, such as RT-PCR, are costly, time-consuming, and require specialized labor and equipment, making them inaccessible to resource-limited settings and low-income countries, where there is a need for affordable and rapid testing solutions.
Innovation Solution
The development of a low-cost, rapid COVID-19 diagnostic device called COLOR, which uses modified cotton swabs with ACE2 and gold nanoparticles to detect SARS-COV-2 through a colorimetric reaction that can be interpreted by the naked eye or with a smartphone, providing high accuracy and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RT-PCR is used for COVID-19 diagnosis, then high accuracy is achieved, but cost and time consumption increase significantly
Solution Approach 1:
The patent replaces the complex mechanical and chemical RT-PCR system with an optical detection system using gold nanoparticles. The colorimetric assay uses visual color changes (red to purple/blue) detected by smartphone cameras, eliminating the need for thermal cyclers, centrifuges, and complex reagent processing while maintaining diagnostic accuracy through plasmonic resonance detection of viral antigens.
Solution Approach 2:
The invention directly utilizes color changes of gold nanoparticles as the detection mechanism. When gold nanoparticles bind to SARS-CoV-2 viral antigens, their plasmonic resonance shifts cause visible color changes from red to purple/blue. This colorimetric response provides rapid visual readout within minutes, replacing time-consuming RT-PCR amplification and detection steps.
2Measurement precision
If RT-PCR is used for COVID-19 diagnosis, then high diagnostic accuracy is achieved, but device complexity and specialized equipment requirements increase
Solution Approach 1:
The patent replaces complex laboratory equipment (thermal cyclers, centrifuges, biosafety cabinets) with simple optical components. The detection system uses only a smartphone camera and basic optical filters to detect color changes, eliminating the need for expensive specialized equipment while maintaining diagnostic accuracy through plasmonic resonance detection.
Solution Approach 2:
The invention uses disposable test strips or well plates coated with capture antibodies and gold nanoparticles. These single-use components eliminate the need for complex reusable equipment, reducing device complexity and enabling deployment in resource-limited settings. Each test cartridge is self-contained and requires no specialized infrastructure.
3Measurement precision
If RT-PCR is used for COVID-19 diagnosis, then high sensitivity is achieved, but manufacturing cost increases
Solution Approach 1:
The patent uses inexpensive gold nanoparticles (typically 10-50 nm diameter) as the detection probe, which can be synthesized through simple chemical reduction methods. The test components (strips, plates, antibodies) are disposable and can be manufactured at scale using standard biotechnology processes, reducing per-test cost while maintaining sensitivity through the high signal amplification of plasmonic resonance.
Solution Approach 2:
The invention changes the detection parameter from measuring nucleic acid amplification (RT-PCR) to measuring optical properties (colorimetry). This parameter change enables the use of cheaper reagents and equipment while maintaining detection sensitivity, as gold nanoparticles provide strong optical signals that can detect low viral loads without requiring complex amplification chemistry.
4Measurement precision
If RT-PCR is used for COVID-19 diagnosis, then high accuracy is achieved, but skilled labor requirements increase
Solution Approach 1:
The patent replaces skilled technical operations (RNA extraction, reverse transcription, PCR amplification, gel electrophoresis) with simple sample application and visual color reading. The assay requires only dropping or swabbing a sample onto the test strip and observing color changes, eliminating the need for trained laboratory personnel while maintaining diagnostic accuracy through the robustness of gold nanoparticle-based detection.
Solution Approach 2:
The invention enables self-testing by individuals without medical training. The test strip provides automatic colorimetric readout that can be interpreted visually or with smartphone assistance, allowing users to perform and interpret their own tests without requiring skilled operators, thereby improving ease of operation while maintaining accuracy.
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
COLOR achieves 90% accuracy and 96% sensitivity in detecting SARS-COV-2, enabling rapid and affordable testing, particularly in resource-limited communities, with each test costing 15¢ and producing results within 5 minutes.
Implementation Method 1
gold nanoparticles stabilized with cysteamine functionalized with human angiotensin-converting enzyme 2 (ACE2) (AuNP-cys-ACE2)... a simple, minute-timescale color shift that can be detected by the naked eye
Implementation Method 2
The use of colorimetric devices for detection has been boosted in the clinical field, mainly because those biosensors are easy to prepare, fast, portable, and count on metallic nanoparticles that have well-established optical properties
Implementation Method 3
modified cotton swabs with ACE2 to recognize the SARS-COV-2 spike protein (SP)... a first protein that selectively binds to a binding domain of a biomarker or antigen
Data Source
AI summary
The COVID-19 pandemic has exacerbated society's tremendous health equity gap. Disadvantaged populations have been disproportionally affected by COVID-19, lacking access to affordable testing, a known effective tool for preventing viral spread, hospitalizations, and deaths. Here, we describe COvid-19 Low-cost Optodiagnostic for Rapid testing (COLOR), a colorimetric biosensor fabricated on cotton swabs using gold nanoparticles modified with human angiotensin-converting enzyme 2 (ACE2), which costs 15 ¢ to produce and detects SARS-COV-2 within 5 minutes. COLOR detected very low viral particle loads (limit of detection: 0.154 pg mL−1 of SARS-COV-2 spike protein) and its color intensity correlated with the cycle threshold (Ct) values obtained using RT-PCR. The performance of COLOR was assessed using 100 nasopharyngeal/oropharyngeal (NP/OP) clinical samples, yielding sensitivity, specificity, and accuracy values of 96%, 84%, and 90%, respectively. In summary, each COLOR test can be manufactured for 15 ¢ and presents rapid minute-timescale detection of SARS-COV-2, thus providing a solution to enable high-frequency testing, particularly in low-resource communities.