Fluorescent Detection System Using High Molecular Weight Polymer Probes
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Solution Overview
Problem
Current fluorescent immunoassays using arylsulfonate cyanine dyes, such as Cy5, face limitations due to a narrow Stokes shift causing self-quenching, which restricts the number of dye molecules that can be conjugated to a single antibody, thereby reducing sensitivity and signal output.
Innovation Solution
A fluorescent detection system employing a probe with a small sensing surface area, a light source and detector mounted on the same side, and a high molecular weight polymer conjugated with multiple binding molecules and fluorescent labels, along with a method involving multiple steps of binding and amplification to enhance sensitivity and minimize background noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple arylsulfonate cyanine dye molecules are conjugated to a single antibody molecule, then the fluorescent signal output should increase, but self-quenching occurs due to narrow Stokes shift, causing the signal to drop rapidly
Solution Approach 1:
The patent changes the fundamental parameter of Stokes shift by switching from arylsulfonate cyanine dyes to fluorescent proteins with wider Stokes shifts. This parameter change allows multiple fluorescent labels per antibody without self-quenching, directly resolving the contradiction between increasing dye quantity and avoiding signal loss.
Solution Approach 2:
The patent uses composite fluorescent protein structures (e.g., GFP, RFP) instead of simple organic dyes. These fluorescent proteins provide both the necessary fluorescence properties and a wider Stokes shift, enabling multiple labels per antibody while preventing self-quenching through their inherent structural and spectral properties.
2Quantity of substance
If a larger sensing surface area is used on the probe, then more analyte binding sites are available, but background noise increases due to non-specific binding
Solution Approach 1:
The patent applies local quality by creating distinct functional zones on the probe: a small sensing surface area (0.01-10 mm²) optimized for specific analyte binding with minimal non-specific binding, and a separate amplification zone where polymer conjugation occurs. This spatial differentiation allows high binding capacity without proportional increase in background noise.
Solution Approach 2:
The probe functionality is segmented into distinct regions: a small sensing surface for specific binding, and a separate amplification region where polymer conjugation with multiple fluorescent labels occurs. This segmentation allows the binding surface to remain small (reducing background) while the amplification process provides sufficient signal through multiple labels per bound analyte.
3Measurement precision
If enzyme-based assays are used, then high sensitivity is achieved through catalytic accumulation of product, but the assay time becomes too long for point-of-care applications
Solution Approach 1:
The patent replaces the time-dependent enzymatic catalysis mechanism with an instantaneous fluorescent label binding mechanism. Instead of enzymes that require time to convert substrate to product, fluorescent labels bind directly to the analyte-antibody complex, providing immediate signal generation without catalytic time delays, thus achieving both high sensitivity and rapid results.
Solution Approach 2:
The fluorescent labels are pre-conjugated to the polymer structure before the assay begins. When the analyte binds to the antibody on the probe, the pre-prepared polymer-fluorophore conjugate can immediately bind and amplify the signal without requiring time-consuming enzymatic reactions or substrate conversion steps.
4Productivity
If fluorescent labels are used instead of enzyme labels, then assay time is reduced and stability is improved, but sensitivity is reduced due to lack of catalytic amplification
Solution Approach 1:
The patent implements a nested structure where multiple fluorescent labels are nested within a single polymer molecule that binds to a single antibody-analyte complex. This nesting provides signal amplification similar to enzymatic cascades: one bound polymer-fluorophore conjugate contributes multiple fluorescent signals, achieving high sensitivity without requiring time-dependent catalysis.
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 system achieves high sensitivity and minimal background noise by using a small probe surface area, lateral flow of reaction solutions, and high molecular weight polymers with multiple fluorescent labels, improving detection limits to pg/mL levels.
Implementation Method 1
a probe having a sensing surface bound with a fluorescent label... a light source and a detector both mounted at the proximal side of the sensing surface of the substrate
Data Source
AI summary
This invention relates to a detection system for measuring a fluorescent signal in a fluorescent assay. The system comprises a probe having a small sensing surface bound with a fluorescent label, and a light source and a detector both mounted at the proximal side of the sensing surface of the substrate. The invention also relates to a method for detecting an analyte in a liquid sample using a probe tip having a small surface area (≤5 mm) and a high molecular weight polymer (≥1 MD) having multiple binding molecules and multiple fluorescent labels. The binding reaction is accelerated by flowing the reaction solutions laterally and moving the probe tip up and down in the reaction vessels. The invention furthers relates to a fluorescent labeling composition comprising a cross-linked FICOLL® molecule having a plurality of binding molecules and a plurality of fluorescent labels.