What is Biacore and How Does it Work? A Complete Guide to SPR Technology

In life sciences, understanding how molecules identify, combine, and separate is like the key to cracking the code of life - whether antibodies accurately snipe viruses, or drug molecules locking disease targets, these microcosmic "molecular dialogues" directly determine the health and disease of life.

The Biacore system, synonymous with surface plasmon resonance SPR technology, is a real-time translator of this microscopic conversation. It abandons the interference of traditional labeling technology, and transforms the instantaneous dynamics of molecular binding into quantifiable data curves through the precise "dance" of light and electrons, making invisible interactions clear and measurable. From the precise optimization of antibody drugs to the analysis of the binding mechanism of the novel coronavirus and host receptors, from the mapping of protein interactions in basic scientific research to the ultimate efficiency of processing tens of samples per second in industrial drug screening, Biacore has become a core tool for decoding the complexity of life with its unique advantages of no marks, real-time, and high sensitivity.

This section takes you through how Biacore technology is disrupting the research paradigm and driving innovation from laboratory discovery to clinical application.

Introduction to Biacore Technology: Basics of Surface Plasmon Resonance

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?

Surface Plasmon Resonance (SPR) is a label-free optical sensing technology that enables real-time detection and quantification of molecular interactions. By measuring changes in the refractive index near a metal surface (typically gold), SPR reveals how molecules bind to each other—whether it's a protein latching onto a drug candidate, an antibody recognizing an antigen, or DNA hybridizing with its complementary strand.

The Physics Behind SPR

The core of SPR lies in the energy coupling between light waves and free electrons on the surface of the metal film. When a beam of polarized light hits the surface of a prism coated with nanoscale gold film at a specific Angle (called an "SPR Angle"), the energy of the light wave excites free electrons on the surface of the gold film, forming a collectively oscillating electron cloud, known as a surface plasma wave. At this time, the intensity of light reflection will be significantly reduced by energy transfer, a phenomenon known as "resonance". When a molecule (such as a protein or antibody) binds to an immobilized ligand on the surface of the gold film, the refractive index of the local environment changes slightly due to the increase in molecular mass, which in turn changes the resonance conditions of the plasma wave, resulting in a shift in the SPR Angle. This offset is captured in real-time by the optical sensor and converted into a signal curve with time (that is, the sensor map), so as to accurately reflect the dynamics of the intermolecular binding process (such as the binding rate, the dissociation rate) and the affinity strength. SPR technology is unique in that it does not need to label molecules, only through the change of optical signal can achieve it interference-free, highly sensitive real-time monitoring, and become a "molecular microscope" to analyze the mechanism of biomolecular interaction.

Biacore: SPR technology pioneer and industry benchmark

Since the introduction of the first commercial SPR instrument in 1990, Biacore's pioneering technical ideas have transformed SPR from a physical phenomenon in the laboratory to an analytical tool in the life sciences. The breakthrough resulted from insights into the nature of biomolecular interactions - traditional labeling techniques, such as fluorescence or radiolabelling, can detect binding events but can interfere with the natural conformation of molecules, obscuring the true dynamics. Biacore's solution goes right to the pain point, allowing researchers to "see" every second of molecular bonding and dissociation for the first time through a labeling-free, real-time monitoring design. Its core technology revolves around sophisticated optical systems and microfluidic control: When biomolecules immobilized on the surface of the sensor chip (such as antibodies or receptors) come into contact with analytes in the mobile phase (such as drugs or antigens), the refractive index changes caused by the binding event are converted into dynamic signals in real-time, and key parameters such as binding rate, dissociation rate and affinity can be automatically calculated by software within a few minutes. This combination of efficiency and precision has quickly made Biacore the standard for pharmaceutical giants and leading laboratories.

Biacore's success lies not only in its hardware innovation but also in the paradigm shift it has driven. In antibody drug development, traditional methods can take weeks to indirectly assess affinity through ELISA or cell experiments, but Biacore can directly quantify the strength of the antibody to the antigen in a single experiment, reducing the development cycle by several times. For example, in the screening of COVID-19 antibodies, several institutions around the world have used the Biacore system to rapidly assess the neutralization capacity of thousands of candidate antibodies, buying valuable time for vaccine development. In addition, the high reproducibility of its data has been recognized by regulatory agencies such as the FDA and has become the gold standard for the equivalence evaluation of biosimilar drugs and original drugs. From the analysis of protein interaction mechanisms in basic research to industrial-grade high-throughput drug screening, Biacore has always stood at the forefront of technology iteration - the new generation of Biacore 8K system can run eight independent channels in parallel and detect up to 384 samples per day, fully meeting the needs of large-scale drug development.

In nearly three decades of development, Biacore's landmark contributions have been deeply embedded in the course of life sciences. It is not only an instrument in the laboratory but also represents the cognitive leap from qualitative to quantitative, from static to dynamic molecular interaction analysis. With the rise of precision medicine and AI drug design, Biacore continues to integrate automation and intelligent technology and may become a more powerful bridge connecting molecular mechanisms and clinical applications in the future.

How Does Biacore Work?

The core of Biacore's system is to translate the physics of the SPR into a quantifiable, visual record of molecular "conversations." When a beam of polarized light hits the surface of the sensor chip's gold film at a specific Angle, the light resonates with the metal's free electrons, forming a "dark Angle" of sharply diminished energy - an Angle that is extremely sensitive to the refractive index of the surrounding environment. If the target molecule (such as an antibody) is fixed on the surface of the chip, when the tested molecule (such as an antigen) in the solution flows through, the combination of the two will change the local refractive index like a stone thrown in the calm water, resulting in a shift in the resonance Angle. Biacore's optical system captures this angular change several times per second, turning it into a real-time rising or falling signal curve that acts like a high-precision camera, recording each dynamic moment of molecular binding and dissociation, frame by frame.

The beauty of this process is that it is real-time and distract-free. While traditional techniques rely on labeling molecules to indirectly predict binding events, Biacore directly "observes" interactions in their natural state. For example, in antibody drug development, researchers anchor a target protein onto a chip and let a solution containing a candidate antibody flow across the surface. As the antibody binds to the protein, the signal curve climbs rapidly. After changing the buffer, if the antibody dissociates, the curve gradually decreases. The system automatically fits these data algorithmically and within minutes calculates the binding rate, dissociation rate, and affinity - parameters that are like molecular "fingerprints" that reveal the strength and stability of interactions and provide a direct basis for optimizing drug design.

Figure 1. Concept of surface plasmon resonance biosensor: (A) Kretschmann geometry of ATR method; (B) The reflected light spectrum before and after the refractive index change; (C) the analyte-biometric element bound to the surface of the SPR sensor and (D) the refractive index change caused by molecular interactions in the reaction medium. (Nguyen HH,2015)

Key Components of a Biacore System

Sensor Chips

The sensor chip is an important element of Biacore, and the nano-scale gold film covered on its surface not only acts as a carrier for SPR signal generation but also provides an "anchor point" for molecular fixation through various chemical modifications. For example:

• CM5 chip: The surface carboxymethyl glucan layer can covalently fix amino proteins (such as antibodies) to form a hydrophilic three-dimensional network to simulate the physiological environment to reduce non-specific adsorption.
• SA chip: Streptavidin-modified surfaces directly capture biotinized molecules (such as DNA or biotin-labeled antibodies) for rapid, targeted immobilization.
• NTA chips: Tagged by nickel ion chelate histamine (His-tag) proteins, especially suitable for the study of membrane proteins or receptors that are difficult to covalently fix.

The choice of the chip directly affects the sensitivity and specificity of the experiment - for example, small molecule fragment screening requires the use of low-density immobilized chips to avoid steric hindrance, while viral particle binding requires a high-load surface design.

For specific chip selection, you can refer to the Biacore Sensor Chips Types, Applications, and Selection Guide.

Flow Cells

The flow cell is a micro-flow system wrapped on a sensor chip, whose precise fluid control determines the efficiency and repeatability of molecular interactions. Biacore's flow tank design features include:

• Laminar flow control: The micrometer channel ensures that the sample flows through the chip surface in a stable laminar flow form to avoid turbulence interfering with the signal.
• Multichannel parallel (such as the 8-channel design of Biacore 8K): allows the control and experimental group to be run simultaneously, automatically deducting background noise (such as buffer refractive index fluctuations).
• Temperature control: The integrated thermostatic system (±0.05℃ accuracy) ensures that the binding experiment is performed at physiological temperatures, especially for the study of membrane proteins or temperature-sensitive molecules.

Binding Assays

The essence of the Biacore experiment is to "capture dynamic binding events," and its standard process is divided into three stages:

• Immobilization: The mobilization of ligands, such as target proteins, onto the chip surface through chemical coupling or affinity capture, optimizing density to balance signal strength and molecular activity.
• Association/Dissociation: The molecules under test (such as drug candidates) flow through the chip at a constant flow rate, recording the binding phase (signal rise) and dissociation phase (signal fall) in real-time. For example, in antibody affinity testing, the KD value is calculated by drawing a saturation curve through a series of diluted antigen concentration injections.
• Regeneration: Elution of the bound molecule with a mild acid-based solution (e.g. 10 mM glycin pH 1.5) restores chip activity for reuse - optimization of this step directly determines chip life (typically 50-100 reuses).

Common Biacore Instruments

For a more detailed comparison and selection of instrument parameters, you can refer to the article A Comprehensive Guide to Biacore Instruments Features, Specifications, and Applications.

Biacore T200: Gold standard for high-sensitivity kinetic analysis

Ultra-low detection limit: It can detect pimolar (pM) class low-abundance samples (such as small molecule fragments, and rare cytokines), and the sensitivity is 5 times higher than that of the previous generation.

Fully automated temperature control: Accurate temperature control to ±0.005 ° C ensures stable analysis of temperature-sensitive molecules such as membrane proteins and RNA complexes.

Complex kinetic analysis: Support Multi-Cycle Kinetics and Single-Cycle Kinetics for accurate modeling of fast or ultra-slow binding reactions.

Biacore 8K: Industrial engine for high-throughput drug screening

Ready-to-use preset solution: built-in standardized experimental process (such as antibody affinity determination, epitope typing), one-click start, reduce the threshold of operation.

Low maintenance costs: With an open chip design (compatible with third-party chips), consumable costs are 40% lower than high-end models.

Compact size: Small footprint, suitable for laboratory space limited scenarios (such as university core sharing platform).

Biacore X100: Cost-effective molecular interaction analysis platform

Ready-to-use preset solution: built-in standardized experimental process (such as antibody affinity determination, epitope typing), one-click start, reduce the threshold of operation.

Low maintenance costs: With an open chip design (compatible with third-party chips), consumable costs are 40% lower than high-end models.

Compact size: Small footprint, suitable for laboratory space limited scenarios (such as university core sharing platform).

Applications

Protein-protein interaction

Biacore reveals the precise mechanisms of protein-protein interactions by monitoring binding dynamics in real-time, such as:

Using the soluble domain of MEG-14 (sMEG-14) of Schistosoma mansoni as bait, a yeast two-hybridization experiment was carried out on human leukocytes cDNA library. It was proved that S100A9 always interacts with sMEG-14 in yeast two-hybrid assay, sedimentation, and SPR experiments.

Antibody affinity assay

Biacore is the gold standard tool for antibody drug development, with applications throughout the process:

Tang J et al. used pseudovirus neutralization tests (PsVNA) covering SARS-CoV-2 WA-1, a variant of Concern (VOC), and a variant of Concern (VOI) to clarify post-vaccination antibody profiles in 69 naive and 17 adults recovering from COVID-19. Surface plasmon resonance (SPR) is used to measure the affinity of antibodies to pre-fused spikes and receptor-binding domains (RBD) and RBD mutants. By comparing differences in affinity, the underlying differences between male and female subjects were finally illuminated.

Drug Discovery and Development:

Target validation: Confirmation of specific binding of candidate drugs (such as small molecule inhibitors) to target proteins (such as kinases) to rule out off-target effects.

Fragment Screening: Screening weakly bound fragments (KD ~ mM class) from low molecular weight (<300 Da) compound libraries to improve affinity through structural optimization.

Epitope competition analysis: Evaluating the competitive binding ability of therapeutic antibodies to endogenous ligands (such as cytokines) to predict the efficacy of drugs in vivo.