Microfluidic iSCAT Tracking for Single-Molecule Characterization
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Solution Overview
Problem
Existing optical microscopy techniques struggle to characterize individual molecules and molecular complexes in solution due to their invisibility and the modification of molecules when immobilized on surfaces, and capillary-based methods face challenges in fabrication and single-point detection.
Innovation Solution
A method using interferometric scattering optical microscopy (iSCAT) in a microfluidic channel with dimensions greater than 1µm in the x-direction, allowing tracking of molecules' motion to determine their size and diffusion coefficients, and optionally using fluorescence microscopy for high-throughput characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If molecules are immobilized on a glass cover slip for optical imaging, then single molecule imaging becomes possible, but the molecules are modified and their natural state is altered
Solution Approach 1:
The patent uses an interferometric scattering microscopy technique where a reference beam interferes with light scattered by the molecule, creating an enhanced signal without requiring the molecule to be immobilized on a surface. The interference pattern serves as an intermediary that amplifies the detection signal while keeping the molecule in its natural solution state.
2Measurement precision
If a capillary with small bore is used for single molecule imaging, then single point detection is achieved, but fabrication becomes difficult and throughput is limited
Solution Approach 1:
The patent divides the detection space into multiple independent imaging regions within a single microfluidic channel, allowing parallel observation of multiple molecules simultaneously. This segmentation approach maintains the precision of single molecule detection while enabling high-throughput analysis and simplifying fabrication compared to multiple capillaries.
Solution Approach 2:
The patent transitions from one-dimensional capillary flow to a two-dimensional microfluidic channel with defined imaging regions, allowing molecules to diffuse into designated observation areas. This dimensional change enables controlled single-point detection within a larger, more manufacturable device structure.
3Measurement precision
If the imaging region has small dimensions, then single molecule resolution is improved, but the number of molecules that can be observed simultaneously is reduced
Solution Approach 1:
The microfluidic channel is divided into multiple distinct imaging regions along the flow direction, each capable of independently resolving single molecules with high precision. Multiple molecules can simultaneously occupy different imaging regions, enabling parallel characterization and increasing throughput without sacrificing localization precision.
Solution Approach 2:
The microfluidic channel design pre-concentrates molecules into specific imaging regions through controlled flow and diffusion, ensuring that molecules are positioned optimally for detection before observation. This preliminary positioning action enables both high precision and high throughput by preparing the sample in advance for parallel analysis.
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
Enables characterization of molecular complexes by tracking their motion, determining size, shape, and interaction with solvent, facilitating high-throughput analysis of particles including biomolecules and nanoparticles, with enhanced sensitivity and specificity.
Implementation Method 1
capturing the images using interferometric scattering optical microscopy
Implementation Method 2
capturing the images using interferometric scattering optical microscopy
Implementation Method 3
tracking movement of the individual molecules/molecular complexes in at least the x-direction in the imaging region
Implementation Method 4
determining a diffusion coefficient of the molecules/molecular complexes from the tracked movement
Data Source
Figure 1
Figure 2
Figure 3a~5b
AI summary
A method of optically characterizing individual molecules/molecular complexes, or other particles, in solution. The method comprises flowing a solution comprising the molecules/molecular complexes into an imaging region of a microfluidic channel, wherein the imaging region of the microfluidic channel has a first lateral dimension of greater than 1μm in an x-direction wherein the x-direction is perpendicular to a direction of the flow; capturing a succession of images of the individual molecules/molecular complexes in the imaging region; tracking movement of the individual molecules/molecular complexes in at least the x-direction in the imaging region using the succession of images; and characterizing the individual molecules/molecular complexes from the tracked movement. In some implementations the characterizing comprises determining a diffusion coefficient of the molecules/molecular complexes from the tracked movement.