Grating-Coupled SPR Analyzer with Enhanced Fluorescence Mode
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Solution Overview
Problem
Current optical techniques for detecting and measuring biological cells and macromolecules require fluorescent or enzymatic labels and physical compartmentalization, limiting sensitivity and efficiency, especially for small molecules like cytokines.
Innovation Solution
A grating-coupled surface plasmon resonance analyzer operating in scanning, non-scanning, and SPR-enhanced fluorescence modes, utilizing a gold-coated diffraction grating and dichroic beamsplitter to enhance fluorescence detection, allowing for real-time monitoring and quantitative measurement of cells and molecules with high sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If fluorescent or enzymatic labels are used for detection, then detection capability is achieved, but device complexity and operational complexity increase
Solution Approach 1:
The patent extracts the detection function from complex labeling systems and physical compartmentalization requirements, using SPR resonance angle shifts to directly detect analyte binding events. The system removes the need for fluorescent/enzymatic labels by measuring refractive index changes at the metal/dielectric interface, thereby simplifying the overall device architecture while maintaining detection capability.
Solution Approach 2:
The patent replaces mechanical/chemical labeling systems with an optical field-based detection mechanism. Instead of using fluorescent or enzymatic labels that require complex optical paths and detection systems, the invention uses surface plasmon resonance to directly sense analyte presence through refractive index changes, substituting a simpler optical measurement approach.
2Difficulty of detecting and measuring
If physical compartmentalization is used to isolate analytes, then specific detection is achieved, but device complexity and sample throughput are reduced
Solution Approach 1:
The patent creates a universal detection platform where a single SPR sensor surface can detect multiple different analytes simultaneously through the use of different capture ligands immobilized on the metal surface. The system eliminates the need for physical compartmentalization by using specific immunochemical interactions to capture analytes at defined regions, allowing one instrument to universally detect various cells, macromolecules, and cytokines without requiring separate physical chambers for each analyte type.
Solution Approach 2:
The patent uses immobilized capture ligands (antibodies) on the metal surface that act as stationary copies or surrogates for the analytes. These ligands are positioned at specific regions and capture their target analytes from the flowing sample, creating a spatial map of analyte binding events that can be detected simultaneously across multiple regions without requiring physical separation of the sample into different chambers.
3Difficulty of detecting and measuring
If SPR resonance angle measurement is used for small molecules, then detection is possible, but measurement precision is insufficient for cytokines
Solution Approach 1:
The patent introduces fluorophore molecules as intermediary agents that amplify the detection signal for small molecules like cytokines. The fluorophores are positioned in close proximity to the metal surface where they experience enhanced local electromagnetic fields from surface plasmons, resulting in greatly enhanced fluorescence emission. This intermediary fluorophore system converts the weak SPR angle shifts into strong fluorescent signals that can be precisely measured, thereby bridging the gap between SPR detection capability and the need for high precision in detecting small cytokine molecules.
Solution Approach 2:
The patent changes the detection parameter from measuring small SPR resonance angle shifts to measuring enhanced fluorescence intensity. By introducing fluorophores that couple to the surface plasmon field, the system transforms the detection mechanism to measure optical emission intensity rather than angle changes, providing significantly enhanced measurement precision for small molecules like cytokines while maintaining the label-free capture advantage of SPR.
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 simultaneous analysis of over 1000 capture sites without crosstalk and achieves femptomolar range sensitivity, effectively quantifying cytokine secretion from single cells with improved detection efficiency compared to traditional methods.
Implementation Method 1
Surface plasmon resonance (SPR) techniques separate analytes contained in complex mixtures through the use of specific capture ligands, usually antibodies, bonded to a metallic surface in contact with a dielectric. Light of a specific wavelength striking the metal/dielectric interface at a specific angle can support a rapidly decaying wave phenomenon (surface plasmon) if there is a means of matching the momentum (K-vector) of the light with that of the loosely bound electrons at the metal/dielectric interface.
Implementation Method 2
In the present case, a diffraction grating immediately below a thin layer of metal provides the momentum matching mechanism.
Implementation Method 3
dichroic beamsplitter to enhance fluorescence detection
Implementation Method 4
Energy from surface plasmons can be out-coupled and absorbed by fluorophore molecules in close proximity to the metal surface. The local field of the propagating wave at the metal/dielectric boundary enhances absorption of plasmons as compared to free-space absorption. The subsequent fluorescent emission is out-coupled into free-space propagating lobes in accordance with the momentum matching conditions previously described.
Implementation Method 5
SPR Surface Enhanced Fluorescence with a Gold-Coated Corrugated Sensor Chip
Data Source
AI summary
An instrument for measuring and analyzing surface plasmon resonance on a sensor surface has a polarized light source optically connected to the sensor surface by a plurality of optical elements, including in one embodiment an optical telescope that transfers light from a rotatable reflecting surface to the sensor surface. Selective positioning of a cylindrical lens into a first position within the path of light transforms collimated light to a rectangular wedge that is incident upon the sensor surface at numerous angles. In another embodiment, the light source is operated as a laser to excite fluorescence on the sensor surface and the fluorescence is selectively directed to a detector by appropriate optical elements positioned in specific configurations.