SH SAW Biosensor Sensitivity via DNA Isothermal Amplification
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Solution Overview
Problem
Current shear horizontal surface wave acoustic (SH SAW) detectors, such as the Optikus™ platform, are unable to reliably detect bioanalytes at concentrations as low as 2 pg/ml, which is two orders of magnitude lower than their minimum detectable limit, failing to meet FDA-compliant sensitivity standards.
Innovation Solution
A method involving the use of a portable, handheld microfluidic reader that captures analytes with antibodies tagged with DNA, amplifies the DNA tags using isothermal amplification, and measures the amplified DNA tags with a SAW detector to achieve enhanced sensitivity, allowing for the detection of analytes at concentrations as low as 2 pg/ml.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mass enhanced detection method using gold or magnetic particles is employed, then sensitivity is improved to 12-24 pg/ml, but the detector still cannot reliably measure concentrations at 800 fg/ml or lower to meet FDA standards
Solution Approach 1:
The detection process is segmented into two independent stages: (1) immunoassay capture stage using magnetic particles to capture analytes, and (2) DNA amplification stage to amplify detected signals. This segmentation allows the mass detection limitation to be overcome by decoupling the capture function from the detection function, enabling reliable measurement at 800 fg/ml and lower concentrations.
Solution Approach 2:
DNA tags attached to magnetic particles serve as intermediaries between the analyte capture and the final detection. The DNA tags are amplified using isothermal amplification, creating a signal amplification intermediary that bridges the gap between the limited mass sensitivity of SAW detectors and the need for ultra-low concentration detection, enabling FDA-compliant sensitivity of 2 pg/ml or lower.
2Measurement precision
If isothermal amplification of DNA tags is performed, then sensitivity is enhanced to detect analytes at 2 pg/ml, but device complexity increases due to additional amplification components
Solution Approach 1:
The complex thermal cycling system required for traditional PCR amplification is replaced with an isothermal amplification system that operates at a constant temperature. This substitution eliminates the need for complex temperature cycling mechanisms, reducing device complexity while maintaining the sensitivity enhancement needed for 2 pg/ml detection.
Solution Approach 2:
The amplification process parameter is changed from temperature-cycling (PCR) to constant-temperature (isothermal) operation. This parameter change simplifies the device requirements by eliminating the need for complex thermal control systems, making the overall detection system more suitable for portable applications while achieving the required sensitivity.
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 significantly increases the sensitivity of SH SAW detectors, enabling reliable detection of bioanalytes at femtomolar to nanomolar concentrations, meeting FDA standards and overcoming the limitations of existing technologies.
Implementation Method 1
a magnetic field is applied to attract the magnetic nanoparticle
Implementation Method 2
The DNA tag is replicated using isothermal amplification to a predetermined amount of DNA tags detectable by a detector
Implementation Method 3
measuring the amount of replicated DNA tags using the detector... shear horizontal surface wave acoustic (SH SAW) detector
Data Source
AI summary
The invention includes a method of assaying an analyte in a sample in a portable, handheld microfluidic reader. The method includes the steps of: inserting the sample in the reader; capturing the analyte with a first antibody having a DNA tag attached thereto; capturing the analyte in the sample with a second antibody attached to a surface or having a magnetic nanoparticle (MNP) attached thereto; where a sandwich including the magnetic nanoparticle, first and second antibodies, the analyte and the DNA tag is formed; replicating the DNA tag using isothermal amplification to a predetermined amount of DNA tags detectable by a detector sufficient to overcome the minimal mass sensitivity limitations of the detector; and measuring the amount of replicated DNA tags using the detector. The invention also includes an apparatus or handheld portable field microfluidic reader in which the method is performed.