Cationic Test Reagents for High-Sensitivity Multiplex Detection

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Solution Overview

Problem

Existing test methods for respiratory infections, such as those caused by SARS-CoV-2, face challenges in detecting substances with an isoelectric point of 10.0 or more due to adsorption on glass or nitrocellulose materials, leading to decreased measurement sensitivity.

Innovation Solution

A test method and reagent system that includes bringing substances with an isoelectric point of 10.0 or more into contact with glass or nitrocellulose materials in the presence of cationic substances to prevent adsorption, using a reagent system with specific binding substances and detection parts, and optionally including a specimen filtration step.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a substance with an isoelectric point of 10.0 or more is brought into contact with a glass-made member or nitrocellulose-made member, then filtration or structural support is achieved, but the substance is adsorbed on the material and measurement sensitivity decreases

Engineering Contradiction:

Improvemeasurement sensitivityVSAvoidadsorption on glass or nitrocellulose

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A cationic substance is introduced as an intermediary between the substance to be detected (with isoelectric point ≥10.0) and the glass-made member or nitrocellulose-made member. The cationic substance prevents direct adsorption by competing for binding sites on the glass or nitrocellulose surface, thereby maintaining measurement sensitivity while allowing filtration and structural support functions to proceed

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The chemical environment is modified by adjusting pH and introducing cationic substances to change the surface charge characteristics of the glass or nitrocellulose materials. This parameter change prevents electrostatic adsorption of the basic substance (isoelectric point ≥10.0) while maintaining the functional integrity of the filtration and support structures

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If multiple respiratory infections are tested using separate specimen collection for each pathogen, then accurate diagnosis is achieved, but the risk of droplet exposure to medical workers increases

Engineering Contradiction:

Improvediagnostic accuracyVSAvoiddroplet exposure risk

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

Multiple respiratory infection tests that previously required separate specimen collections are merged into a single testing workflow using one specimen. The invention enables parallel detection of multiple pathogens (including SARS-CoV-2, influenza, adenovirus, RS virus) from a single nasopharyngeal or oropharyngeal swab specimen, reducing the number of exposure events while maintaining diagnostic accuracy through multiplex detection capabilities

Inventive Principle:

Principle #5Merging (Combining)

3Object-affected harmful factors

If a single specimen is used for multiple respiratory infection tests, then droplet exposure risk is reduced, but adsorption of substances with high isoelectric point on test reagents decreases measurement sensitivity

Engineering Contradiction:

Improvedroplet exposure riskVSAvoidmeasurement sensitivity

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

Cationic substances are used as protective intermediaries in the test reagents and on glass-made members throughout the testing workflow. This intermediary layer prevents adsorption of substances with isoelectric point ≥10.0 (such as SARS-CoV-2 nucleocapsid protein) while allowing the single-specimen multi-test workflow to function, thereby maintaining both safety and sensitivity

Inventive Principle:

Principle #24Intermediary (Mediator)

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 high-sensitivity detection of multiple substances, including SARS-CoV-2 proteins, while maintaining measurement sensitivity by using cationic substances to mitigate adsorption issues.

Implementation Method 1

a first substance to be detected having an isoelectric point of 10.0 or more is brought into contact with any one or both of a glass-made member and a nitrocellulose-made member in a presence of a cationic substance

Methodology Applied

Scientific EffectElectrostatic repulsion: Electrostatics

Data Source

PatentUS20250283883A1Test method, test reagent, and test kit

Publication Date: 2025.09.11 SEKISUI MEDICAL CO LTD

AI summary

A qualitative or quantitative test method to detect a substance to be detected contained in a specimen, the test method including a preparation step of preparing a test sample from the specimen, and a test step of testing at least part of the test sample with a reagent to detect each of a first substance to be detected and a second substance to be detected, in which the first substance to be detected has an isoelectric point of 10.0 or more, and in any one or both of the preparation step and the test step, the first substance to be detected is brought into contact with any one or both of a glass-made member and a nitrocellulose-made member in the presence of a cationic substance. In this test method, two or more substances to be detected including a substance having an isoelectric point of 10.0 or more can be detected with high sensitivity using the same specimen while suppressing a decrease in measurement sensitivity.