Single-Molecule Imaging With Plasmonic Scattering Noise Removal
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Solution Overview
Problem
Traditional label-free optical detection methods, such as surface plasmon resonance (SPR) and total internal reflection (TIR) microscopy, struggle with imaging single molecules due to strong background reflections and low spatial resolution, making it difficult to distinguish weak signals from single molecules.
Innovation Solution
Implementing a near-field plasmonic scattering microscopy (PSM) system that utilizes a sensor surface with controlled roughness to enhance scattered light interference, combined with a differential-integral imaging processing algorithm to subtract background noise and correct for mechanical drift, allowing for precise measurement of single molecule binding kinetics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional SPR or TIR detection methods are used, then the system can detect reflected light, but the strong background reflection overwhelms the weak signal from single molecules
Solution Approach 1:
The patent extracts and removes the harmful reflected light component from the detection system. By using a spatial filter or confocal aperture, the strong background reflection is physically separated and excluded from the detection path, allowing the weak scattered light from single molecules to be detected without overwhelming background interference.
Solution Approach 2:
The patent introduces scattering particles or structured illumination patterns as intermediaries to convert the weak molecular signal into a detectable form. These intermediaries enhance the scattered light intensity while maintaining spatial resolution, enabling single molecule detection through indirect measurement rather than direct observation of the molecular signal alone.
2Measurement precision
If traditional SPR or TIR microscopy is used, then the system can achieve label-free detection, but the diffraction pattern of several microns in size lowers the image spatial resolution
Solution Approach 1:
The patent applies local quality enhancement by using super-resolution techniques such as STORM or PALM that exploit the localized fluorescence emission of individual molecules. By activating and localizing sparse subsets of molecules sequentially, the system achieves spatial resolution beyond the diffraction limit while maintaining label-free detection capabilities for the bound complexes.
Solution Approach 2:
The patent transitions from two-dimensional diffraction-limited imaging to three-dimensional localization by measuring the focal volume position of single molecules through intensity distribution analysis. This dimensional extension allows precise spatial mapping of molecular binding events with resolution independent of the diffraction pattern size.
3Measurement precision
If incident light intensity is increased to minimize shot noise, then the signal-to-noise ratio improves, but heating of the molecules on the sensor surface occurs
Solution Approach 1:
The patent employs periodic scanning or intermittent illumination strategies where the incident light is applied in pulsed or alternating sequences rather than continuously. This periodic action allows the sensor surface and molecules to cool between illumination cycles, maintaining acceptable temperature levels while accumulating sufficient signal through multiple measurement cycles to achieve high signal-to-noise ratio.
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
The PSM system achieves high sensitivity and spatial resolution by enhancing the signal-to-noise ratio, enabling the detection and analysis of single molecules, including protein binding processes, even in complex media like serum, with improved reproducibility and stability.
Implementation Method 1
surface plasmon resonance (SPR) or total internal reflection (TIR)
Implementation Method 2
total internal reflection (TIR)
Implementation Method 3
Light scattered from an isolated object (e.g., a molecule) drops quickly with the size of the object. Here, a sensor with an appropriate level of surface roughness is used to produce scattered light that interferes with light scattered from the object, producing an image contrast
Implementation Method 4
produce scattered light that interferes with light scattered from the object, producing an image contrast
Data Source
AI summary
Detecting single molecules includes binding the single molecules to a surface of an optically transparent substrate, irradiating the surface of the substrate with light having an incident angle selected to achieve total reflection of the light, thereby scattering light from the surface and from the single molecules bound to the surface, and collecting light scatted by the surface and by the single molecules bound to the surface to form a series of images. Systems for detecting single molecules include an optically transparent substrate, a means for flowing a sample solution over a surface of the substrate, a light source configured to irradiate the surface, a camera, and a collection optical system configured to collect light scatted by the surface and by the target molecules on the surface to form a series of images on the camera.