Integrated Systems and Photonics

Biosensor technology

 

The detection of biological materials during a blood test, such as biomarkers or pathogens, is of great importance for our healthcare system. Current detection methods are based on stationary laboratory instruments and can only be carried out by qualified personnel. An example of a widely-used method to determine concentrations of biological materials in an analyte is the ELISA test (enzyme-linked immunosorbent assay). This includes several chemical steps, followed by a final photometric measurement of the marker molecules introduced. Biosensors are currently developed based on immobilised biological receptors, which enable a highly-selective measurement of biological, biomedical or chemical substances, while also enabling much more compact, mobile equipment.

One of the most important properties of biosensors is their potential for marker-free detection. The sensor surface itself assumes the role of the marker, and allows for direct detection of biological material. This facilitates faster, easier and more physiological measurement. Another characteristic of biosensors is their possible use for molecular binding kinetics experiments in real time, which answer important questions for drug development.

We research biosensors which use a periodic nanostructured sensor surface (photonic crystal). Quasi guided modes in these structures enable contact-free and sensitive measurement. We have demonstrated that by combining light source, polarising filters and photonic crystal, a simple intensity measurement allows real-time determination of concentration. In a series of experiments, we were able to determine the binding kinetics of a 2.5 nmol biotin-streptavidin solution with a compact prototype (Fig.1).

Abbildung 1:
Figure 1: Prototype of a biosensor with a nanostructured sensor surface. Real-time measurement of binding kinetics of streptavidin to biotin.

 

We have further developed this concept into a multi-parametric, marker-free protein measurement with a miniaturised measuring system, which uses a camera for detection (Fig.2).

Abbildung 2:
Figure 2: Scheme of a camera system for marker-free, multiparametric detection of various proteins.
Figure 3:
Figure 3: Photo of the camera system.

 

Another current project is the development of an intraocular pressure sensor which is integrated with an intraocular lens. Nowadays, many people have intraocular lenses implanted during the course of their life. These could be equipped with additional functions. We have developed a (not yet miniaturised) prototype of an intraocular pressure sensor. This is based on a nanostructured membrane which closes off a reference pressure chamber, the deformation of which can be measured optically and contactlessly from the outside.

Abbildung 4:

Figure 4: Diagram of an intraocular lens with the measuring range for intraocular pressure. A nanostructured membrane over the measuring chamber becomes deformed, depending on the pressure. The evaluation of the membrane curvature is contactless, performed by a camera system from the outside.

Selected Publications

Y. Nazirizadeh, V. Behrends, A. Prósz, N. Orgovan, R. Horvath, A. M. Ferrie, Y. Fang, C. Selhuber-Unkel & M. Gerken. "Intensity interrogation near cutoff resonance for label-free cellular profiling", Scientific Reports, Vol. 6, p. 24685 (2016).
Link: »https://dx.doi.org/10.1038/srep24685

S. Jahns, M. Bräu, B.-O. Meyer, T. Karrock, S. B. Gutekunst, L. Blohm, C. Selhuber-Unkel, R. Buhmann, Y. Nazirizadeh, and M. Gerken, "Handheld imaging photonic crystal biosensor for multiplexed, label-free protein detection", Biomed. Opt. Express, vol. 6, no. 10, p. 3724, (2015). 
Link: »https://dx.doi.org/10.1364/BOE.6.003724

Karrock, T., & Gerken, M., "Pressure sensor based on flexible photonic crystal membrane", Biomedical optics express, 6(12), 4901-4911 (2015).
Link: »https://doi.org/10.1364/BOE.6.004901