Technology
Profit from our expertise in kinetics, optics and fluidics

Biametrics offers you solutions to study interaction between biomolecules within an unparalleled robustness and flexibility. Enhance your research with the ability to investigate kinetic and thermodynamic properties of your biomolecules with high accuracy and reproducibility.

Measurement principle

Our proprietary SCORE (Single Colour Reflectometry) technology exploits the interference of monochromatic light at the boundaries between biolayers to directly monitor the binding between biomolecules. You gain direct access to binding curves without labels, within a robust hardware setup, using low cost consumables.

Monochromatic light from a light source is used for illuminating a transparent sensor element from the backside. The light beams are partially reflected at the two boundaries 1. chip / biolayer and 2. biolayer / buffer of this sensor chip. Binding of biomolecules (e.g. antibodies) to surface-bound ligands (e.g. antigens) increases the optical thickness (n*d) of the biolayer, which is the product of physical thickness d and refractive index n. This leads to an increased reflection at the second boundary biolayer / buffer. The interference of the two reflected light beams can be detected by photosensitive elements as an intensity encoded change of the reflection coefficient. By monitoring the change of this reflection coefficient over time, it is possible to study label-free biomolecular interactions in real time.

The intensity of the reflected light depends on the optical thickness of the biolayer on the sensor element, which is directly depending on the concentration and affinity of the specifically bound analyte. The time resolved and label-free read out allows for determining kinetic and affinity data (KD, ka, kd), specificity, concentration and thermodynamic data (enthalpy, entropy) of the interaction.

SCORE provides high robustness due to its inherent properties: the sensor read out is stable towards temperature fluctuations, as opposing influences of temperature changes on refractive index n and physical thickness d are compensated by measuring the product as optical thickness (n*d).

The two dimensional read out of the sensor element provides perfect scalability and high-throughput of the SCORE technology. The sensor elements can be designed as an array of (n x m) spots (up to 10,000 spots per cm2) in order to detect multiple different specific interactions with one single measurement.

Label-free kinetic measurements / real-time measurements

Label-free real-time measurements are predestined for analysis of kinetic and thermodynamic constants of a biomolecular interaction in its unaltered state. Using SCORE, robust kinetic data from even low affinity binder can be obtained.

The real-time label-free read out allows for determining kinetic data like the association rate constant ka and the dissociation rate constant kd. Furthermore, thermodynamic data like the affinity constant KD as well as enthalpic and entropic parts of the interaction can be analysed.

As no labels are used for the detection of the interaction, the analysis of kinetic constants is not falsified as the interaction is maintained in its natural, unaltered state. Also, the interaction is characterised during a flow injection of the analyte solution and not in a steady state flow. This leads to two advantages:

  1. Concentration decrease in the bulk due to the interaction with the binding partner on the sensor surface does not occur using SCORE and therefore real kinetic data can be obtained. Steady state flow technologies obtain altered information on kinetic data due to concentration decrease during the analysis.
  2. Information on low affinity binders are not lost as their binding to their interaction partner on the surface can also be detected during the flow injection analysis. Steady state flow technologies lose the information on low affinity binders due to washing steps.

SCORE therefore provides more precise information than other labelled technologies like fluorescence read-out. Also, the sampling rate is adjustable between 1 and 100 Hz, allowing for characterisation of fast kinetic interactions.

Fluidics

High precision micro-fluidics within the Biametrics devices guarantee high reproducibility of your measurements, even with complex liquid samples like e.g. whole-blood.

The Biametrics devices use high precision micro-fluidics components for the flow injection of analytes. Thus, high reproducibility of measurements is guaranteed and disturbing effects like concentration decrease in the bulk solution during the interaction are eliminated. The used micro-fluidic system is capable of injecting almost all kinds of liquid samples ranging from low MW drug candidates up to high MW proteins including DNA, RNA, polysaccharides, lipids, cells, viruses and nanoparticles, all in various matrices, e.g. DMSO-containing buffers, urine, plasma, serum, whole blood. Samples volumes between 100 µL and 1000 µL can be injected and analysed.

The sensor element

Our sensor chips provide high selectivity with excellent inhibition of non-specific binding and can be used in with all common printing technologies. The sensor coatings can easily be tailored to your respective applications.

SCORE uses specific affinity surfaces on transparent glass or polymer substrates. These sensor elements offer a high selectivity related to the specific target molecule in order to change the optical properties when an affinity reaction occurs. Tailored surface chemistries provide excellent inhibition of non-specific binding of non-relevant proteins from the sample solution. Also, the surfaces can be tailored to the respective applications providing high or low amounts of binding sites for kinetic or concentration analysis, 2D (polymer brush) or 3D (hydrogel) structures, specifically tagged surfaces (e.g. Streptavidin, NTA, Protein A/G, etc.).

Using common printing technologies (pin-printers, capillary printers, etc.), it is easily possible to generate high-density arrays on the sensor elements with up to 10,000 spots/cm2 (depending on the performance of the used arrayer). As no gratings or gold layers are used on the sensor element, the individual spots do not interfere with each other during the label-free read out.

Performance

The Biametrics devices offer high performance in sensitivity and detection limits, in robustness of kinetic evaluation, as well as in fluidics and consumables.

Sensitivity and detection limit of the sensor: due to the extremely low baseline noise (typically <0.001 %/min) the LOD is below 1 pg/mm2.

Kinetics: association rate constants (ka) can be determined between 103 and 107 M-1s-1 (and even higher for macromolecular analytes). Due to the extremely low baseline drift (typically <0,0005 %/min) dissociation rate constants (kd) between 10-6 to 0,5 s-1 can be determined.

Types of samples: time resolved investigation of any kind of biomolecular interactions including whole cell assays.

Consumables: glass and plastics consumables (transducers).

Data acquisition: all Biametrics sensor devices provide a data acquisition rate between 1-100 Hz and in-line reference subtraction.

Fluidics: all Biametrics sensor devices are equipped with a powerful microfluidic sample handling system to guarantee precise biomolecular interaction studies.