CryoTEM Hydrated State Imaging for VLP Content Quantification
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Solution Overview
Problem
Current methods for assessing the content of Virus-Like Particles (VLPs) and Adeno Associated Virus (AAV) particles, such as negative-stain Transmission Electron Microscopy (nsTEM), are unreliable due to stain interference and mechanical stress, leading to false positives and negatives, making it difficult to accurately determine particle fullness or emptiness.
Innovation Solution
The method employs Cryo Transmission Electron Microscopy (CryoTEM) to maintain particles in a hydrated state, eliminating the need for stain and allowing direct visualization of internal features, with optional use of ionic liquids or liquid sample holders to preserve the native structure, enabling accurate classification of particles as empty, full, or ambiguous based on internal density and morphology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If negative-stain TEM is used to visualize particles, then contrast is enhanced and particles can be seen, but the stain covers the particles and prevents direct viewing of internal content, leading to unreliable classification
Solution Approach 1:
The patent removes the staining step entirely from the preparation process. By using cryo-TEM without stain, the harmful coating that prevents direct viewing of particle content is eliminated, while particles remain visible through inherent electron scattering contrast in the frozen-hydrated state.
Solution Approach 2:
The patent changes the physical state parameter of the sample from dried/stained to frozen-hydrated. This parameter change allows direct visualization of particle content without stain interference, resolving the contradiction between needing contrast and avoiding coverage.
2Strength
If stain is applied to protect particles and enhance contrast, then particle morphology is preserved, but the stain layer thickness cannot be controlled and creates false appearances of empty or filled particles
Solution Approach 1:
The patent extracts and removes the staining step from the preparation process. By eliminating stain application, the uncontrolled variable of stain layer thickness is removed, preventing false classification of particles while still preserving morphology through cryo-protection.
Solution Approach 2:
The patent introduces cryo-protection as an intermediary mechanism instead of chemical stain. The frozen-hydrated state acts as a mediator that protects particle morphology during preparation without interfering with internal content visualization.
3Illumination intensity
If particles are viewed in dried state with stain, then contrast is improved, but mechanical stress from blotting and staining causes particle collapse and shape distortion
Solution Approach 1:
The patent changes the physical state parameter from dried to frozen-hydrated. This maintains particles in their native hydrated conformation throughout preparation, eliminating mechanical stress-induced collapse while preserving morphology through cryo-protection.
Solution Approach 2:
The patent applies cryo-protection beforehand by freezing particles in their hydrated state. This pre-protection cushions particles against mechanical stress during subsequent handling, preventing collapse and shape distortion.
4Productivity
If conventional nsTEM classification is used, then particles can be categorized as empty or full, but false positives and negatives occur due to stain interference and preparation artifacts
Solution Approach 1:
The patent removes the staining step that causes false classifications. By using unstained cryo-TEM, particles display their true internal content without stain-induced artifacts, eliminating false positives and negatives while maintaining classification efficiency.
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
CryoTEM provides robust, accurate, and repeatable quantification of particle content by maintaining consistent particle appearance across the sample, reducing false classifications and enhancing the reliability of determining particle fullness or emptiness, thereby improving the assessment of genetic material content for gene delivery applications.
Implementation Method 1
the sample is rapidly frozen into a cryogenic liquid at a cryogenic temperature
Data Source
AI summary
The method is for quantitative measurement of particle content using hydrated state imaging such as CryoTEM. A sample of virus-like particles (VLPs) or virus particles is provided. Preferably, the sample is rapidly frozen into a cryogenic liquid at a cryogenic temperature. While at the cryogenic temperature, the particle content of each VLP in the frozen sample is observed in the CryoTEM. An amount of the particle content of the VLPs is determined to assess whether the VLPs are empty or not.