Q-Sense E1

Application examples

Electrochemistry and QCM-D on the same surface

One way of coupling electrochemistry with QCM-D (EQCM-D) is to combine cy­clic voltammetry (CV) and QCM-D. This means that  simultaneous measurements of the frequency (f), dissipation (D), and current (I) are made as they respond to a varying potential (E) above a single sensor surface. An example of where the EQCM-D combination provides a unique insight is the study of electrically active poly­electrolyte multilayers. 

The Q-Sense electrochemistry module (QEM 401) was used where the standard sensor acts as both the QCM-D sensor and as the working electrode of the electrochemistry cell. The figure shows how the contraction and expansion of a multilayer upon application of a po­tential is followed via frequency and Dissipation. A positive potential makes the film ex­pand and soften (lower frequency and higher dissipation). When the potential is reduced back to 0 Volts, the film contracts reversibly. Frequency and dissipation change as a function of the applied potential over a polyelectrolyte multilayer.

For more information, see:

• Technology Note 2 — Electrochemistry and QCM-D on the Same Surface

QCM-D/Ellipsometry to characterize thin molecular films

Both QCM-D and ellipsometry can provide information about adsorption on surfaces and the proper­ties of the resulting films. In particular, both techniques can quantify adsorbed masses in real-time. Ellipsometry, be­ing an optical technique, measures adsorbed molecules only, whereas QCM-D also measures solvent coupled to the film. Comparing the masses measured by the two techniques indicates the amount of solvent in the film. In this way, film swelling or col­lapse can easily be distinguished from adsorption/desorption events. Additionally, chang­es in the solvent content of thin films can be monitored over time and other structural or morphological changes of adsorbed films can be identified.

The figure shows the combination of QCM-D and ellipsometry that was used to investigate the formation of a supported lipid bilayer from small unilamellar vesicles (SUVs) containing 10% biotinylated lipids, followed by the specific binding of streptavidin, as well as biotinylated vesicles. This involves generating QCM-D data through changes in oscil­lation frequency of the sensor to ac­quire information on mass and dissipa­tion data to acquire data on structural properties of the film. Si­multaneously, polarized light is reflect­ed at the surface of the QCM-D sen­sor and the changes in its polarization state are measured.

For more information, see:

• Application Note 20 — Ellipsometry and QCM-D on the Same Surface

Simultaneous QCM-D and microscopy monitoring of cell adhesion 

Controlling interactions between living and non-living matter is essential in tissue engineering, in designing medical implants and in cell-based biosensors and. It is therefore crucial to identify and understand events taking place at the living/non-living interface. Microscopy, which probes the sample from the top, may be insufficient to evaluate cell-substrate interactions. In that respect, the QCM-D technique provides a powerful complement to microscopy as it enables  real-time in situ analysis of cell attachment and cell membrane rearrangement at the sensor surface. QCM-D can be directly combined with microscopy using the window QCM-D module, which enables visual access to the sensor. Changes in mass and viscoelastic properties sensed with QCM-D can then be directly correlated to real-time observation of cell number and morphology.

For more information, see:

• Application Note 13 — QCM-D and Microscopy Monitoring of Cell Adhesion

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• • Biomaterials
    
  • Energy
  • Environmental
  • Polymers
  • Cell & Molecular Biology
  • Biomolecules (DNA, Lipids, andProteins),surfactants and nanoparticles