Reflectometric interference spectroscopy

The reflectometry interference spectroscopy ( RIfS ) is a physical method based on the interference of white light in thin layers. This method is used in practice to study molecular interactions. The basic measuring principle is the Fabry -Perot interferometer.

Realization

White light is irradiated vertically to a multi- layer system. This consists of a silicon dioxide ( SiO2 ), a high refractive index of tantalum pentoxide ( Ta2O5 ) and a further silicon dioxide layer, which can be chemically modified. At each phase boundary partial beams of white light can be reflected and refracted transmitted. The reflected partial beams are superposed to form an interference spectrum, which is detected by a diode array spectrometer. By chemically modifying the top SiO2 layer is modified so that it can interact with target molecules. This interaction causes a change in the physical layer thickness and the refractive index of this layer. The product of the two is defined as the optical layer thickness. The change in optical layer thickness leads to a modulation of the interference spectrum. Observed the change of the interference spectrum over time, it is possible to monitor the binding behavior of the target molecules.

Application

RIfS is primarily used as a detection method in chemo-and biosensors application.

Chemical sensors are particularly suitable for measurements under difficult conditions and in the gas phase. As sensitive layers not selectively measured polymers the analytes either by size (so-called molecular sieving in microporous polymers) or due to different polarities (eg functionalized polydimethyl siloxanes ) are mostly used to sort. For non- selective measurements, a sum signal is measured by several analytes in RIfS, it must be that recourse for the quantification of multivariate data analysis such as neural networks. However, it can also specifically measured polymers, the so-called molecularly imprinted polymers (MIPs ) are used to provide the artificial recognition structures.

In the field of biosensors, polymers such as polyethylene glycols or dextrans are applied to the layer system and immobilized thereon biomolecules detection structures. As recognition structures are in principle all classes of substances can be used ( for example, proteins such as antibodies, DNA / RNA, such as aptamers, small organic molecules such as estrone, but also lipids, such as phospholipid membranes).

The method makes it possible to monitor a time-resolved interaction between the binding partners, without having to rely on fluorescence or radioactivity labels. It is like the surface plasmon resonance spectroscopy ( SPRS ) is a label-free technology.