Surface Plasmon Resonance for Drug Discovery and Biomolecular Interaction Studies

In the intricate world of drug discovery and biomolecular interactions, understanding how molecules interact is paramount. Surface Plasmon Resonance (SPR) technology has emerged as a game-changer, offering researchers a powerful and versatile tool to study these interactions in real-time, label-free, and with exceptional sensitivity. From identifying potential drug candidates to unraveling the intricate mechanisms of biomolecular binding, SPR is revolutionizing the way we approach drug development and biological research.

This article delves into the principles, applications, and future prospects of SPR, highlighting its transformative impact on these critical fields.

SPR Technology Overview

According to statistics, 90% of drug candidates fail clinical trials due to imprecise target binding or off-target toxicity, often due to the lack of real-time, quantitative analysis of biomolecular interactions in early studies. Traditional techniques such as ELISA or radioligand binding assay can measure binding strength, but cannot capture the problem of dynamic binding of the drug to the target: when does binding begin? How long after bonding does it dissociate? Is there non-specific adsorption? These "invisible kinetic details" are the key to determining drug efficacy and safety. While scientists are still puzzled by the "blind man and elephant" -like molecular interaction data, surface plasmon resonance technology has quietly revolutionized the underlying logic of drug development - without fluorescent labeling, only a beam of light and nanoscale metal film can track every frame of molecular bonding/dissociation in real-time.

What is SPR technology?

Surface Plasmon Resonance technology is an optically based labeling-free detection method that enables real-time monitoring of interactions between biomolecules. Since its first commercialization in the 1990s, SPR technology has been widely used in drug discovery, proteomic research, disease diagnosis, and other fields. Its core advantages are high sensitivity, real-time performance, and no need for labeling, making it an important tool for studying molecular binding dynamics and affinity. SPR is an optical phenomenon in which the intensity or phase of reflected light changes when incident light excites a surface plasma wave at the interface between a metal (such as gold or silver) and a medium. This change is closely related to the refractive index near the interface, which in turn is caused by molecular binding events. By monitoring the changes in reflected light, the process of molecular binding and decoupling can be recorded in real-time, and the binding dynamics parameters can be obtained.

You can read the article Surface Plasmon Resonance (SPR) vs Biolayer Interferometry (BLI) Which is Better.

How does SPR technology work?

The core of SPR technology uses the surface plasmon resonance phenomenon to detect the interaction between molecules. When a beam of polarized light shines on the surface of a metal film (usually gold film) at a specific Angle, it will excite the free electrons on the metal surface to produce a collective oscillation, forming a surface plasma wave. This resonance phenomenon will lead to a significant reduction in the intensity of the reflected light, and the change of the resonance Angle is closely related to the change of the refractive index near the surface of the metal film. When the molecule to be measured is bound to the ligand molecule fixed on the surface of the metal film, the local refractive index changes, resulting in a change in the resonance Angle. By monitoring the change of resonance Angle in real time, the SPR instrument can accurately measure the dynamic process of molecular binding and decoupling, and obtain key parameters such as binding affinity and rate constant.

You can read the Surface Plasmon Resonance Sensorgram A Step-by-Step Guide article to learn more.

Benefits of SPR Technology

SPR technology has unique advantages, such as no fluorescence or radiolabelling of the molecules, keeping the molecules in their natural state; The process of molecular binding and dissociation was monitored in real-time and the kinetic parameters were obtained. It can detect very weak molecular interactions and so on. We've done a lot of comparisons in the article about Surface Plasmon Resonance (SPR) versus Biolayer Interferometry (BLI) Which is Better, so you can get an idea.

Application of SPR Technology in Drug Discovery

New drug development is a long and complex process, and SPR technology, with its unique advantages, is injecting new vitality into this process and significantly accelerating the process of new drug development.

Drug target screening

SPR technology can screen potential drug targets with high throughputs, such as disease-related proteins, nucleic acids, and other biomolecules. By fixing the candidate molecules on the sensor chip and injecting the sample to be tested successively, the molecules with binding ability to the target can be quickly screened, and the time of target screening is greatly shortened.

A classic example is desloratadine, an anti-allergy agent that inhibits proliferation in HCC cell lines, cell-derived xenografts (CDX) and patient-derived xenografts (PDX) models. Tan XP et al. identified N-myristoyltransferase 1 (NMT1) as a target of desloratadine by drug affinity response target stability (DARTS) and SPR assays. In conclusion, this study suggests that desloratadine may be a novel anticancer agent and that NMT1-mediated myristoylation contributes to HCC progression and is a potential biomarker and therapeutic target for HCC.

Figure 1. SPR analysis test results (Tan XP,2023)

Lead compound optimization

SPR technology can accurately determine the binding affinity of the compound to the target, which provides an important basis for the optimization of chemical structure. By comparing the affinity of different compounds, more potential lead compounds can be screened. SPR technology can monitor the process of molecular binding and deionization in real-time, and obtain the dynamic parameters such as binding rate constant and deionization rate constant. These parameters can help researchers understand the mechanism by which the compound binds to the target and guide the optimization of the chemical structure, such as increasing the binding rate or decreasing the dissociation rate. You can read Biacore Data Analysis Software Tools and Interpretation of Results for help in analyzing the results produced by the SPR.

Löfås S summarizes the process of SPR secondary screening and lead optimization. SPR is a label-free technique that can generate kinetic data of biomolecular interactions. This allows researchers to quantify the binding properties of lead compounds to their targets based on affinity, specificity, and association/dissociation rates. The latest generation of SPR biosensors integrates the hit-to-lead process and produces more in-depth information, providing answers that traditional endpoint analysis cannot address. This allows users to make more informed choices about the selection of candidate molecules prior to preclinical development. Many studies have used SPR biosensors for secondary screening, lead optimization, quantitative structure-activity relationship analysis, prediction of adsorption, distribution, metabolism, excretion, and/or toxicity assessment.

Study on mechanism of drug-target interaction

SPR technology can be used to identify specific sites where a drug binds to a target, such as through competitive experiments or mutation analysis to identify key amino acid residues for binding. In addition, SPR technology can be combined with other structural biology methods, such as X-ray crystallography or nuclear magnetic resonance (NMR), to resolve the detailed three-dimensional structure of the drug binding to the target and reveal the molecular mechanism of drug action. Most importantly, SPR technology can monitor in real-time the conformational changes caused by the binding of drugs to targets, such as the folding or unfolding of proteins, which provides important information for understanding the mechanism of action of drugs.

An example is Dong X et al. 's introduction of a high-fat diet-induced hamster NAFLD model to explore the lipid-lowering and liver-protecting effects of BVC. Then, the BVC small molecule probe is designed and synthesized based on CC-ABPP technology, and the target of BVC is dug out. A series of experiments were performed to identify the target, including competitive inhibition tests, SPR, cell heat transfer assays, drug affinity response target stability assays, and immunoprecipitation. Subsequently, the pro-regeneration effect of BVC was validated in vitro and in vivo by flow cytometry, immunofluorescence, and end-deoxynucleotide transfer enzyme-mediated dUTP notch end labeling (TUNEL).

Surface Plasmon Resonance in Virus Detection

The emergence of novel viruses and the constant threat of pandemics highlight the critical need for rapid, sensitive, and reliable virus detection methods. Surface Plasmon Resonance technology has emerged as a powerful tool in this field, offering several advantages over traditional techniques.

In the article by Ahmed T et al., prism-based optimized surface plasmon resonance SPR biosensors already exist for early detection of various cancer types. The SPR sensor based on the Kretschmann structure integrates several novel layers, including a silver layer, a zinc selenide layer, a lead telluride layer, and a silver nanocomposite layer. The SPR sensor was analyzed by Angle query analysis, which uses the attenuated total reflection (ATR) method to study the refractive index components and detect different forms of cancer cells. The finite element method is used for the design and performance evaluation.

Real-time and Label-free Detection

Direct Detection

SPR allows for the direct detection of viruses without the need for labeling or amplification steps, simplifying the detection process and reducing the risk of false positives.

Real-time Monitoring

SPR provides real-time monitoring of virus-binding events, enabling the determination of binding kinetics and affinity, which can be valuable for understanding virus-host interactions.

High Sensitivity and Specificity

Enhanced Sensitivity

SPR instruments can detect very low concentrations of viruses, making them suitable for early diagnosis and surveillance.

High Specificity

By utilizing specific antibodies or receptors immobilized on the sensor surface, SPR can achieve highly specific detection of target viruses, even in complex biological samples.

Multiplexed Detection

Simultaneous Detection

SPR platforms can be designed to detect multiple viruses simultaneously, increasing testing efficiency and reducing costs.

Differentiation of Virus Strains

SPR can differentiate between different strains of the same virus, providing valuable information for epidemiological studies and vaccine development.

Applications in Virus Detection

Clinical Diagnosis

SPR-based biosensors can be used for rapid and accurate diagnosis of viral infections in clinical settings, enabling timely treatment and infection control.

Virus Surveillance

SPR can be employed for continuous monitoring of virus circulation in the environment, such as in wastewater or air samples, providing early warning of potential outbreaks.

Vaccine Development

SPR can be used to evaluate the efficacy of vaccines by measuring the binding affinity and neutralizing activity of antibodies against target viruses.