Multi-Parametric Surface Plasmon Resonance (MP-SPR)

MP-SPR for Material Sciences

For the past 20 years, SPR has been used for biomolecular interaction analysis. Now, MP-SPR broadens the application range to biophysical studies, and biomaterials studies, such as ceramic and polymer coating characterizations and biocompatibility studies.

Thickness and RI can be determined by fitting of curves using Fresnel formalism. With additional lasers, a singular solution can be found without known RI or thickness.

MP-SPR for Life Sciences

Multi-Parametric Surface Plasmon Resonance (MP-SPR) provides label-free measurements of molecular interactions with picomolar sensitivity in gas and in liquid. MP-SPR also allows use of a wide range of surfaces, enabling studies of surface-molecule interactions and additional lasers that are used to determine surface thickness and refractive index!

Unlike traditional SPR, MP-SPR can distinguish true molecular binding from differences in bulk liquid using Total Internal Reflection (TIR).

What is MP-SPR? MP-SPR utilizes the physical SPR phenomena, but requires special optical arrangements. MP-SPR broadens the capabilities of the physical SPR phenomena out of the black-box interactions approach by providing more information from the same experiment. MP-SPR is 6 parameters of a full SPR curve, while traditional SPR follows only a narrow area of the full SPR curve. Multi-Parametric does not only measure molecular interactions, but also properties of thin and thick layers! SPR Navi™ instruments are the only SPR instruments on the market using the newest technique – the MultiParametric SPR (MP-SPR). While others measure only the angular position of the SPR peak, we measure the whole SPR curve. This enables you to measure chips coated with other metals than gold, to measure both thin and thick samples, and many more. In fact, it can even distinguish a buffer change! Moreover, our instruments can be equipped with additional lasers with various wavelengths. This offers you the unique possibility to work also with absorbing samples or to measure refractive index (RI) when thickness is not known precisely and vice versa.

At a given angle, laser light excites surface plasmons at the metal-liquid/gas interface through a resonance phenomenon. This resonance results in a reduced intensity of the reflected light at the photodetector, which can thus be measured. Unlike the majority of competitors, SPR Navi™ does not measure at one narrow angular range only, but scans much broader range of incident angles, resulting in a full SPR curve. All changes in the interfacial layer can be measured and are reflected in the full SPR curve. Therefore, SPR Navi™ can measure on a number of samples, surfaces and conditions, others cannot…

Parameters achievable with both -Traditional SPR and MP-SPR:

1         Angular position of SPR peak min is the only parameter measured by traditional SPR. It is typically presented in a traditional SPR sensogram.

Parameters achievable only with MP-SPR:

2         Intensity of SPR peak min. depends on the sensor material and the media. Unlike others, SPR Navi™ is able to measure in liquid as well as in gas, on metals, metal oxides and hydrogels.

3         Total Internal Reflection (TIR) value is dependent on the bulk properties around the sensor. It is not affected by protein binding or mass deposition. It can be used to correct RI in bulk differences between control and sample channels as well as for dn/dc calculation.

4         Steepest falling and raising slope shows the most sensitive measurement area for the fast fixed angle measurements. 

5         SPR-width at 3 different levels defines the shape of the SPR peak. It contains information on light absorption by the binding molecules and therefore, enables characterization of absorbing coatings and samples. 

6         Another wavelength pair can be used for all measurements. This resolves layer thickness or RI and thus enables fitting of full SPR curves with Fresnell equations

SPR Navi™ with MP-SPR

• SPR Navi Prism: The optical arrangement enables to cover the whole refractive index range of 1.00-1.40 in one measurement without exchanging any components! This also means that we can cover the SPR angle range of 40 degrees! This is unprecedented range in SPR instruments!
• SPR Navi Elastomer: We are the second SPR manufacturer to use elastomer instead of index-matching oil. This enhances the comfort and speed of the use greatly as the users do not have to cover their slides with oil between measurements!
• SPR Navi Sensor Slides: The sensor slides are very easy-to-exchange due to our drop-in design. Our sensor slides cost only a fraction of prices of slides elsewhere. Moreover, the user can prepare their own slides enhancing the functionality and cost-effectiveness of our instrument even further.
  • GLASS: We use BK7 glass, which helps us to keep the sensor slide cost at minimum.
  • SPR METAL:SPR phenomena needs a conductive metal in order to be created. Gold is used as a "golden standard", but other metals can be used as well. Noble metals generally have best properties. Some examples include Au, Pt, Ag, Al, Cu.
  • OTHER MATERIAL: SPR metal can be covered with other materials. The maximum allowed thickness varies based on the material. Some of the techniques that can be used for coating include vapor deposition, sputtering, sol-gel deposition, Langmuir monolayer depositions, spin coating, dip coating, self assembly, electrochemistry. We can provide more information on request. Some examples of materials used with SPR Navi include Al2O3, SiO2, hydrogels, nylon, cellulose, PS, PP, PET.
  • FUNCTIONALIZATION: A number of systems can be used for functionalization of the sensor slides. Some of the examples include Carboxylate, Amine, Biotin, Disulfide, HisTag.
• Sample: Unlike with other systems, SPR Navi works both with samples in liquid and in gas phase. Also optically absorbing samples can be measured with SPR Navi.
• Flow-cell: As a standard, the SPR Navi instruments are equipped with a PDMS flow-cell, but other flow-cells are available as well. Most notably, an electrochemical flow-cell for simultaneous measurements of MP-SPR and EC, a gas flow-cell for gas samples, and a high-chemical-resistance flow-cell made of PEEK.

*) Traditional SPR is represented by instruments with focused beam, fixed angle set-up.

Protein binding to hydrogels

Example of utilizing peak minimum (2) and Total Internal Reflection (TIR) angle differences (3)

Injections:

1. Cleaning injection – Activation injection – Sensor molecule injection – deactivation injection – non-specific blocking injection – cleaning injection – ja lopuksi buffer change
2. Cleaning injection – 2 M NaCl with 10 mM NaOH – bulk shift
3. Actiation injection – EDC/NHS activation of COOH groups – bulk shift
4. Protein immobilization – relatively low concentration of protein and injected only to blue channel – only surface specific signal is detected
5. Deactivation – only bulk reaction
6. non specific blocking – BSA at 2.5 mg/mL concentration – both bulk and specific signal.
7. Cleaning – only bulk change observable.
8. Buffer change – bulk shift of buffer solution changing observable.