Explain the working principle of a surface plasmon resonance (SPR) biosensor and its applications in label-free detection.
1 Answer
Surface Plasmon Resonance (SPR) biosensors are powerful tools used in the field of biotechnology and analytical chemistry for label-free detection and real-time monitoring of biomolecular interactions. The working principle of SPR biosensors is based on the interaction of light with a thin metal film on the surface of a sensor chip, typically made of gold or silver, in contact with a transparent medium (often glass) and the sample solution.
Working Principle of SPR Biosensors:
Metal Surface: The sensor chip's metal surface is coated with a thin layer of gold or silver. This metal film supports the propagation of surface plasmons, which are collective oscillations of electrons at the metal-dielectric interface.
Prism Coupling: A prism is placed on top of the metal-coated sensor chip at a specific angle. The incident light, usually from a monochromatic light source like a laser, is directed through the prism and interacts with the metal-dielectric interface.
Evanescent Wave: When the light hits the metal-dielectric interface at a specific angle called the resonance angle or SPR angle, it creates an evanescent wave. This evanescent wave penetrates into the sample solution adjacent to the metal surface.
Biomolecular Interactions: When biomolecules, such as proteins, DNA, or antibodies, bind to the metal surface (covalently or non-covalently) or interact with molecules already bound there, it leads to a change in the refractive index of the medium close to the metal surface.
Real-Time Detection: As the binding of biomolecules occurs, the refractive index change at the metal surface alters the resonance angle of the incident light. This shift in the SPR angle is measured in real-time, providing valuable information about the kinetics (association and dissociation rates) and affinity of the biomolecular interactions.
Applications of SPR Biosensors in Label-Free Detection:
Biomolecular Interaction Studies: SPR biosensors are widely used to study molecular interactions, such as protein-protein interactions, protein-ligand binding, antibody-antigen binding, DNA hybridization, and more. The label-free nature of the detection allows researchers to monitor binding events in real-time without the need for fluorescent or radioactive tags.
Drug Discovery: SPR biosensors play a crucial role in drug development by helping researchers characterize the interactions between potential drug candidates and their target molecules. This information is valuable for determining drug potency and selectivity.
Disease Diagnosis: In medical diagnostics, SPR biosensors can be employed for detecting biomarkers related to various diseases, including cancer, infectious diseases, and autoimmune disorders. The label-free approach simplifies the assay and reduces the risk of false-positive results.
Protein Engineering: Researchers use SPR biosensors to optimize the design of proteins and antibodies by assessing binding affinities and kinetics for different variants.
Environmental Monitoring: SPR biosensors have applications in environmental monitoring, such as detecting pollutants, toxins, or pathogens in water or air samples.
In summary, SPR biosensors work based on the principle of detecting changes in the resonance angle of light caused by biomolecular interactions on the metal surface. This label-free and real-time detection approach makes SPR biosensors highly valuable in a wide range of research and practical applications.
Working Principle of SPR Biosensors:
Metal Surface: The sensor chip's metal surface is coated with a thin layer of gold or silver. This metal film supports the propagation of surface plasmons, which are collective oscillations of electrons at the metal-dielectric interface.
Prism Coupling: A prism is placed on top of the metal-coated sensor chip at a specific angle. The incident light, usually from a monochromatic light source like a laser, is directed through the prism and interacts with the metal-dielectric interface.
Evanescent Wave: When the light hits the metal-dielectric interface at a specific angle called the resonance angle or SPR angle, it creates an evanescent wave. This evanescent wave penetrates into the sample solution adjacent to the metal surface.
Biomolecular Interactions: When biomolecules, such as proteins, DNA, or antibodies, bind to the metal surface (covalently or non-covalently) or interact with molecules already bound there, it leads to a change in the refractive index of the medium close to the metal surface.
Real-Time Detection: As the binding of biomolecules occurs, the refractive index change at the metal surface alters the resonance angle of the incident light. This shift in the SPR angle is measured in real-time, providing valuable information about the kinetics (association and dissociation rates) and affinity of the biomolecular interactions.
Applications of SPR Biosensors in Label-Free Detection:
Biomolecular Interaction Studies: SPR biosensors are widely used to study molecular interactions, such as protein-protein interactions, protein-ligand binding, antibody-antigen binding, DNA hybridization, and more. The label-free nature of the detection allows researchers to monitor binding events in real-time without the need for fluorescent or radioactive tags.
Drug Discovery: SPR biosensors play a crucial role in drug development by helping researchers characterize the interactions between potential drug candidates and their target molecules. This information is valuable for determining drug potency and selectivity.
Disease Diagnosis: In medical diagnostics, SPR biosensors can be employed for detecting biomarkers related to various diseases, including cancer, infectious diseases, and autoimmune disorders. The label-free approach simplifies the assay and reduces the risk of false-positive results.
Protein Engineering: Researchers use SPR biosensors to optimize the design of proteins and antibodies by assessing binding affinities and kinetics for different variants.
Environmental Monitoring: SPR biosensors have applications in environmental monitoring, such as detecting pollutants, toxins, or pathogens in water or air samples.
In summary, SPR biosensors work based on the principle of detecting changes in the resonance angle of light caused by biomolecular interactions on the metal surface. This label-free and real-time detection approach makes SPR biosensors highly valuable in a wide range of research and practical applications.