SPFS Biosensor DNA Ligand Structural Switch
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Solution Overview
Problem
Conventional surface plasmon field-enhanced fluorescence spectroscopy (SPFS) biosensors require multiple steps and a long turnaround time due to the need for fluorescent labeled antibodies, which complicates the detection process.
Innovation Solution
A DNA ligand with a structure that changes in the presence of a target is used as a molecular switch, relocating a fluorescent marker from the quenching region to the enhanced region or vice versa, allowing for one-step SPFS biosensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fluorescent labeled second antibodies are used for protein detection in conventional SPFS biosensors, then detection sensitivity is maintained, but the number of assay steps increases and turnaround time is extended
Solution Approach 1:
The patent combines the target recognition function and fluorescent signal generation function into a single DNA ligand molecule. The DNA ligand contains both the target recognition sequence and the fluorescent label, eliminating the need for separate antibody molecules. This merging of functions reduces the number of assay steps from multiple antibody binding steps to a single hybridization step while maintaining detection sensitivity through the fluorescent label.
Solution Approach 2:
The DNA ligand serves multiple functions simultaneously: it acts as the capture molecule immobilized on the metal film, serves as the target recognition element through its sequence specificity, and provides the fluorescent signal through its attached fluorophore. This multi-functionality eliminates the need for separate first and second antibodies, simplifying the assay procedure while maintaining detection capability.
2Measurement precision
If multiple antibody binding steps are performed in conventional SPFS biosensors, then specific detection is achieved, but turnaround time is prolonged
Solution Approach 1:
The DNA ligand is pre-designed and immobilized on the metal film with the target recognition sequence already in place. This preliminary preparation allows direct hybridization with the target sequence without requiring sequential antibody binding steps. The pre-positioned fluorescent label is already attached to the DNA ligand, ready to emit signal upon target binding, thus reducing turnaround time while maintaining specificity.
Solution Approach 2:
The patent skips the intermediate steps of first antibody binding and second antibody binding by using a single DNA ligand that performs both functions. The assay rushes through the detection process by utilizing direct DNA-DNA hybridization between the immobilized DNA ligand and the target sequence, followed immediately by fluorescent signal detection, eliminating time-consuming sequential steps.
3Productivity
If DNA ligand structural change is used as a molecular switch, then assay steps are reduced to one step, but the mechanism becomes more complex
Solution Approach 1:
The DNA ligand utilizes changes in its structural parameters (conformational changes) in response to target binding. When the target sequence hybridizes with the DNA ligand, it induces a structural transition that changes the distance between the fluorescent label and the metal surface. This parameter change (position of fluorophore) modulates the fluorescent signal intensity, providing a direct readout of target presence without requiring additional assay steps.
Solution Approach 2:
The patent replaces complex mechanical or chemical amplification systems with a straightforward optical detection system based on fluorescent emission. The structural change in the DNA ligand directly modulates the fluorescent signal through its interaction with the metal surface's electromagnetic field, substituting complex signal amplification mechanisms with a simple optical readout that enhances productivity.
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 approach reduces the complexity and turnaround time of SPFS biosensors while maintaining high sensitivity, enabling rapid and simple detection by leveraging DNA structural changes to optimize fluorescent signal emission.
Implementation Method 1
Surface plasmon field-enhanced fluorescence spectroscopy (SPFS) is a known biosensing technology
Implementation Method 2
If a fluorescent label is trapped in this enhanced region, a relatively strong fluorescent signal is generated
Implementation Method 3
the nucleic acid molecule changes its structure either from a folded state to an extended state upon binding to a target, or from an extended state to a folded state upon binding to a target
Data Source
AI summary
A DNA ligand capable of structural changes upon binding to a target is used as a molecular switch with a SPFS (surface plasmon field-enhanced fluorescence spectroscopy) biosensor to realize one-step SPFS biosensing with rapid turnaround time. The SPFS biosensor has a thin metal film on a prism; when a light of a certain wavelength irradiates on the prism at a certain angle, a strong electrical field is generated at the surface of the metal film. The DNA is immobilized on the metal film surface with its free terminal modified with a fluorescent marker. Without the target, the DNA is folded and the fluorescent marker is located in the region of metal quenching near the metal surface. Upon binding to the target, the DNA is extended and the fluorescent marker is located in the region of enhanced electric field near the metal surface and emits a strong fluorescent signal.