SEM-Based Optical DNA Mapping Without Heavy-Metal Staining
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing DNA imaging techniques, such as transmission electron microscopy (TEM) and fluorescence microscopy (FM), face challenges in achieving high-resolution imaging of DNA molecules while maintaining simplicity and accessibility, and scanning electron microscopy (SEM) struggles with DNA resolution exceeding its thickness.
Innovation Solution
A method involving nick translation with a nickase to label DNA, staining with a DNA-binding protein and polymer, and immobilizing on a functionalized silicon substrate for SEM imaging, enabling high-resolution DNA visualization without heavy metals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transmission electron microscopy (TEM) is used to achieve high-resolution DNA imaging, then imaging resolution is improved, but the process complexity and time required increase due to heavy metal salt staining and shadow casting methods
Solution Approach 1:
The patent extracts and eliminates the heavy metal salt staining step from the TEM imaging process. By using intrinsic electron scattering properties of DNA and alternative contrast enhancement methods, the invention removes the complicated shadow casting and heavy metal staining procedures while maintaining high-resolution imaging capability
Solution Approach 2:
The patent replaces the mechanical/chemical staining process (heavy metal salt application and shadow casting) with an alternative imaging approach that relies on electron beam interaction with the DNA molecule itself and its surrounding environment, substituting a complex chemical-mechanical system with a more direct physical imaging method
2Ease of operation
If fluorescence microscopy (FM) is used for DNA imaging, then simplicity and accessibility are improved, but imaging resolution deteriorates due to the diffraction limit making nanometer-scale observation challenging
Solution Approach 1:
The patent replaces the optical imaging system (fluorescence microscopy) with an electron microscopy-based system. This substitution transitions from light-based imaging limited by diffraction to electron beam-based imaging capable of nanometer-scale resolution, while maintaining operational simplicity through direct imaging protocols
Solution Approach 2:
The patent changes the fundamental imaging parameter from optical wavelength to electron wavelength. By using electrons instead of photons, the system achieves much higher resolution (nanometer scale vs. micrometer scale) while preserving the simplicity of the imaging approach through direct visualization methods
3Area of stationary object
If scanning electron microscopy (SEM) is used for DNA imaging, then observation range and flexibility are improved, but imaging resolution deteriorates because SEM resolution far exceeds the 2 nm thickness of DNA molecules
Solution Approach 1:
The patent introduces an intermediary coating or contrast-enhancing layer that deposits material around or on the DNA molecule. This intermediary layer amplifies the electron scattering signal from the thin DNA structure, making it visible at SEM resolution while preserving the large observation range advantage of SEM
Solution Approach 2:
The patent applies local contrast enhancement specifically to the DNA molecule regions of interest. By selectively depositing or staining only the DNA structures rather than the entire field of view, the method enhances local visibility without sacrificing the global observation range capability of SEM
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 method achieves high-resolution imaging of DNA molecules, including genomic and mitochondrial DNA, without the need for heavy metals, facilitating well-aligned images and seamless integration with microfluidic devices.
Implementation Method 1
While transmission electron microscopy (TEM) enables detailed observation of the fine structure of DNA, it requires DNA imaging performed by using heavy metal salts, such as uranyl acetate, in combination with a shadow casting method to overcome low electron scattering
Implementation Method 2
contacting a double-stranded DNA with a nickase to form a nick at a target sequence motif
Implementation Method 3
generating labeled double-stranded DNA by incorporating labeled nucleotides into a nick site of the double-stranded DNA
Implementation Method 4
staining a backbone of the labeled double-stranded DNA
Implementation Method 5
stretching and immobilizing the stained double-stranded DNA on a substrate having a functionalized surface
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided is a method of scanning electron microscopy (SEM)-based optical DNA mapping. The method of optical DNA mapping according to an aspect, by utilizing SEM as a basic platform, provides enhanced accessibility and user-friendliness, superior compatibility with chemically functionalized surfaces and microfluidic devices, and the ability to obtain high-resolution DNA images without metal usage, thereby enabling optical DNA mapping with improved resolution.