Upstream Substrate Zone for Paper-Based Assay Sensitivity
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Solution Overview
Problem
Current paper-based assays, such as lateral flow tests, face limitations in sensitivity due to the poor limit-of-detection of detector molecules, requiring larger sample volumes and introducing the risk of human error with enzyme-substrate amplification methods, which can lead to false negatives if the substrate addition step is activated prematurely.
Innovation Solution
A test strip design with a substrate addition zone located upstream of the test zone, allowing for direct fluid flow and eliminating the need for a separate wash step, enabling immediate substrate addition without waiting time, thus enhancing assay sensitivity and reducing false positives and negatives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If enzyme-substrate amplification approach is used to improve sensitivity, then detection sensitivity is improved, but waiting time is required before substrate addition which introduces human error and false negatives
Solution Approach 1:
The substrate is pre-loaded into the substrate addition zone upstream of the test zone before the actual assay is performed. This preliminary action eliminates the need for waiting time and manual substrate addition during the assay, preventing human error and false negatives while maintaining high detection sensitivity through enzyme-substrate amplification.
Solution Approach 2:
The test strip design allows the substrate to automatically flow from the substrate addition zone to the test zone through capillary action without requiring external intervention. The system serves itself by eliminating the need for user activation of substrate addition, thereby removing the source of human error while preserving the sensitivity benefits of enzyme-substrate amplification.
2Reliability
If separate wash step is included to improve accuracy, then false positives are reduced, but assay complexity and time are increased
Solution Approach 1:
The substrate addition zone is integrated upstream of the test zone within the same test strip structure, allowing the substrate to flow directly to the test zone without requiring a separate wash step. This merging of functions maintains accuracy by preventing contamination while simplifying the assay procedure and reducing overall complexity.
Solution Approach 2:
The unnecessary wash step is extracted and eliminated from the assay protocol. The upstream substrate addition zone design inherently prevents contamination that would normally require washing, allowing the wash step to be removed entirely while maintaining or improving accuracy.
3Productivity
If substrate is added immediately without waiting to improve efficiency, then assay time is reduced, but false negatives may occur due to premature activation
Solution Approach 1:
The substrate is pre-positioned in the substrate addition zone upstream of the test zone before sample application. This preliminary positioning allows immediate substrate availability when needed, eliminating waiting time and improving efficiency while preventing premature activation through proper spatial separation and controlled flow.
Solution Approach 2:
The substrate addition zone acts as an intermediary reservoir between the user and the test zone. It controls the timing and location of substrate delivery through capillary flow, allowing immediate assay initiation while preventing false negatives by ensuring substrate reaches the test zone only when appropriate.
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 design improves paper-based assay results by providing cleaner signal readouts, reducing false positives and negatives, and increasing efficiency in obtaining results, while maintaining the simplicity of paper-based assays.
Implementation Method 1
a substrate addition zone for receiving a substrate and a test zone, said test zone comprising a capture agent, wherein the substrate addition zone is located upstream of said test zone
Data Source
AI summary
A test strip for paper based assay, the test strip comprising a substrate addition zone for receiving a substrate and a test zone, the test zone comprising a capture agent, wherein the substrate addition zone is located upstream of the test zone. The invention also relates to a paper-based enzyme assay comprising a test strip of the invention and methods of detecting the presence of an analyte in a sample using a test strip of the invention.