Chitosan Color-Fixing Agent Lateral-Flow Test Timing
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Solution Overview
Problem
Lateral-flow test devices using humidity color indicators face challenges in controlling the duration of color change visibility, making it difficult to determine when test results can be accurately read and when they should no longer be read due to diffusion of indicator molecules.
Innovation Solution
Incorporating chitosan with humidity color indicators like cobalt chloride, copper chloride, or lead iodide on a cellulose or nitrocellulose substrate, adjusting the chitosan-to-indicator ratio to modulate the time period for color change and disappearance, thereby providing a time indication mechanism that fixes the color indicator molecules, ensuring accurate result reading and determination of when results are no longer valid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If humidity color indicators are used in lateral-flow test devices, then visualisation of sample arrival and test result detection is enabled, but the duration of color change visibility cannot be controlled, making it difficult to determine when results should be read
Solution Approach 1:
Chitosan is introduced as an intermediary substance between the humidity color indicator and the aqueous sample. It acts as a controlling layer that regulates the interaction between water molecules and the indicator, thereby controlling the duration and intensity of the color change. This mediator allows the system to maintain color visibility for an extended period while still providing a clear read window.
Solution Approach 2:
The patent modifies the chemical environment by introducing chitosan, which changes the physical-chemical parameters of the indicator system. Chitosan's interaction with water and the indicator molecules alters the diffusion rate and color development kinetics, enabling control over the temporal characteristics of the color change without affecting the fundamental detection mechanism.
2Illumination intensity
If the excess of indicator molecules is increased, then color change becomes more pronounced, but the color faints faster due to diffusion
Solution Approach 1:
Chitosan serves as a buffering intermediary that moderates the interaction between indicator molecules and water. It allows sufficient indicator molecules to be present for strong color intensity while controlling their diffusion rate, preventing rapid fading. The chitosan layer creates a controlled release mechanism that maintains both intensity and duration.
Solution Approach 2:
The patent creates a composite system combining chitosan with the humidity color indicator. This composite material integrates the color-changing properties of the indicator with the moisture-regulating properties of chitosan, achieving a synergistic effect where the color intensity and visibility duration are both optimized through the combined material properties.
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 use of chitosan as a color-fixing agent allows for controlled color change and disappearance, enabling precise timing for result readability and validity, enhancing the diagnostic capabilities of lateral-flow test devices for analytes such as hCG antigen, Helicobacter pylori antibody, and HIV antibody.
Implementation Method 1
The mechanism is based on the property of chitosan to form cross-links with e.g. cellulose or nitrocellulose. The resulting structure allows for entrapping colour indicator molecules.
Implementation Method 2
The resulting structure allows for entrapping colour indicator molecules. The ratio of chitosan and colour indicator determines the time period after which the colour indication molecules are washed out, e.g. by diffusion in an aqueous sample to be tested.
Implementation Method 3
Cobalt (II) chloride forms hydrates of different colours ranging between blue-violet (CoCl 2 · H 2 O) and pink (CoCl 2 · 6H 2 O).
Implementation Method 4
once appeared upon contact of indicator and sample, the colour faints over time due to a diffusion of the indicator molecules.
Data Source
AI summary
The present invention refers to an indication means comprising an indicator, preferably a humidity colour indicator, and chitosan. The invention further refers to a lateral-flow test device comprising said indication means, and to a use of said test device for diagnosis, prognosis and/or observation of a disease. The invention also refers to a use of chitosan for the preparation of an indication means and/or a lateral-flow test device.