Interpreting MP-SPR and QCM/QCM-D results

 

Quartz Crystal Microbalance with Dissipation (QCM-D) or simple Quartz Crystal Microbalance (QCM) and Multi-Parametric Surface Plasmon Resonance (MP-SPR) are both real-time, label-free measurements. Both techniques measure molecular interactions and layer properties. However, the results differ due to the underlying working principle.


 

MP-SPR

  • MP-SPR is based on measurement of optical properties. 
  • It provides a direct measurement of optical thickness (dry mass - excluding the solvent between molecules).
  • Typical volume above the measured area is 1 µL.
  • MP-SPR uses glass with a thin film of gold as a substrate. A wide variety of surfaces are available.

QCM, QCM-D

  • QCM-D is based on measurement of mechanical properties. 
  • It provides a direct measurement of acoustic mass (wet mass includes the mass of solvent between molecules) .
  • Typical volume above the measured area is 40 µL.
  • QCM uses quartz crystal substrates. A wide variety of surfaces comparable to that of MP-SPR are available.

 

Interpreting results in Material Science Studies:
Difference between measurement of dry and wet mass.

The combined information from MP-SPR and QCM-D reveals the water content of the film, which is very useful in material studies. MP-SPR can be further used to probe the structural properties of the film using the thickness and optical density information.

Testimonial

"It is essential for us to decouple the contribution of hydration and bound water for quantification of adsorbed mass, layer thickness, etc." Prof. Orlando Rojas, NCSU, USA and Aalto University, Finland

 

Interpreting results of QCM-D and MP-SPR in Life Science Studies:

Sample consumption

In QCM (or QCM-D), the flow-cell volume is 40 µl, in MP-SPR it is 1 µl. Typical flowrates in QCM are 50-200 µL/min, while they are 5-50µL/min in MP-SPR. In fact, as can be seen in Viitala 2012 and Liang 2013, one has to use 7 times higher flow-rates in QCM than in MP-SPR in order to achieve the same mass transport. So while the sample consumption for a single injection of 4 min at 50µL/min is 200 µl in MP-SPR, the QCM has to run at 350 µL/min, which means 1,75 ml for one injection.
This is the reason, why SPR biosensors are much more common for affinity measurements than QCM.

Speed of measurement

By an example, when depositing a new polyelectrolyte layer, one can make 3-4 layers in MP-SPR, while in the same time only 1 layer is formed in QCM (QCM-D). So although with MP-SPR there are 2 channels on the sensors and with QCM you could use 4 senosors, each with one chamber, the result will be 6-8 measurements with MP-SPR in the same time that QCM delivers 4 measurements. This is just because of the distances, volumes and fluidics design.

 

Mass transfer

To ensure same kinetics, the flow-rate has to be adjusted to result in the same mass transfer. According to Viitala (1), the flow-rate of 10 μl/min in MP-SPR corresponded to 73 μl/min flow rate in QCM. Therefore, in order to obtain comparable results in studies with QCM and MP-SPR, the flow-rate used in the experiment should be 7.3 times higher for QCM than for MP-SPR.


Typical flow-rates:

qcm_mp-spr_mass_transfer_flow-rate_m.png

MP-SPR

QCM

QCM-D

5 µL/min 35 µL/min
10 µL/min 73 µL/min
50 µL/min 365 µL/min
100 µL/min 730 µL/min

Hydration artifacts

In regards to kinetic studies, there are known hydration effects. Both methods require long hydration of the hydrogel surfaces to avoid drifting (substrate swelling during the experiment). On the other hand, hydration is recorded in the QCM measurement (wet mass measured), while in MP-SPR it is excluded (dry mass measured) and therefore, does not cause problems in small molecule measurements.

References

Fluid dynamics modeling for synchronizing surface plasmon resonance and quartz crystal microbalance as tools for biomolecular and targeted drug delivery studies, Viitala et al. Journal of Colloid and Interface Science 2012

Non-labeled monitoring of targeted liposome interactions with a model receptor surface: Effect of flow rate and water content, Liang et al. European Journal of Pharmaceutical Sciences, 2013

Scientific publications where both QCM and MP-SPR are used:

Adsorption of a Nonionic Symmetric Triblock Copolymer on Surfaces with Different Hydrophobicity, Xiaomeng Liu†, Dong Wu‡, Salomon Turgman-Cohen§, Jan Genzer§, Thomas W. Theyson∥ and Orlando J. Rojas*†⊥∥, Langmuir 2010, 26(12), 9565–9574

Effect of Molecular Architecture of PDMAEMA-POEGMA Random and Block Copolymers on Their Adsorption on Regenerated and Anionic Nanocelluloses and Evidence of Interfacial Water ExpulsionVuoriluoto M. 1, Orelma H. 1,2, Johansson L.S. 1, Zhu B. 3, Poutanen M. 4, Walther A. 3, Laine J. 1, Rojas O.J. 1, J Phys Chem B. 2015 Dec 10; 119(49): 15275-86

Modification of cellulose films by adsorption of CMC and chitosan for controlled attachment of biomolecules, Hannes Orelma1, Ilari Filpponen2, Leena-Sisko Johansson3, Janne Laine4, Orlando Jose Rojas5, Biomacromolecules (2011) 10

Fluid dynamics modeling for synchronizing surface plasmon resonance and quartz crystal microbalance as tools for biomolecular and targeted drug delivery studies, Tapani Viitala (a); Huamin Liang (a); Mayur Gupta (a), (b); Thomas Zwinger (c); Marjo Yliperttula (a); Alex Bunker (d); (e); Journal of Colloid and Interface Science 378 (2012) 251–259

Strongly Stretched Protein Resistant Poly(ethylene glycol) Brushes Prepared by Grafting-ToGustav Emilsson †, Rafael L. Schoch ‡, Laurent Feuz , Fredrik Höök †, Roderick Y. H. Lim ‡, and Andreas B. Dahlin *†,  ACS Applied Materials & Interfaces, 2015, 7 (14), pp 7505–751

Find more than 30 other publications with MP-SPR and QCM here

Selected Application Notes:

  • AN#149 Polymer characterization using MP-SPR - Adsorption studies and layer thickness
  • AN#129 Comparing QCM & MP-SPR. A flowrate study.
  • AN#115 Polymer layers MP-SPR & QCM-D