The Research Group Biosensing Surface (RG BSO) is engaged in the development and characterization of novel functional layers for sensors and microfluidic applications in the life science sector (e.g. medicine, pharmacy and biotechnology). Nowadays, biosensors are used in many different ways; for example, in clinical medicine to control blood sugar levels, for food quality control or in environmental analysis to detect potentially environmentally harmful chemicals.
For bionsensing and microfluidic applications, the control of the physical, chemical and biological interface properties is essential to ensure the best possible performance regarding the interaction with the biological environment. Plasma-assisted surface modification processes produce materials with new properties by creating new surface functionalities or depositing thin layers. Plasma surface treatments offer a variety of technical advantages, such as easy scalability, long-term stability of the modified surface, applicability to nearly all materials/ surfaces, fast and environmental-friendly processes, as well as the production of a multitude of functional groups. As a result, the range of applications is equally varied.
In the RG BSO, the production of thin plasma-polymer (pp) coatings at the macro- and micro-scale with different functionalities is investigated in an interdisciplinary research environment at the interface of polymer chemistry, material sciences and plasma technology. Moreover, a goal of the group is to find safer and greener precursors to produce the pp films at atmospheric pressure. Another focus is the coupling of molecules/enzymes/proteins/cells, which can be realized by plasma-based surface modifications. The properties of the generated layers are investigated using state-of-the-art surface analysis, to obtain information on the layer structure and stability as a function of the coating process. As these characteristics are directly related to the functionality of the layer as a biosensing surface, investigations on the interaction with the analyte are also carried out.
The core of every biosensor is the biological recognition structure, which can consist of an enzyme, an antibody, DNA or whole cells. In order to be able to selectively detect the analyte in the sample, a surface modification of the biological recognition layer is required. The surface chemistry of the recognition structure must be selected in such a way that, as far as possible, no non-specific interactions occur and, at the same time, targeted coupling of the analyte-binding partner on the sensor surface is realized. In particular, for measurements in real samples it is crucial that the functionalized surface has a sufficient immobilization density and a sufficiently high binding activity so that even low concentrations can be detected.
One focus of the BSO research group is the generation of thin plasma-polymerized films enriched with oxygen-containing functional groups, as well as other functionalities, including conductive polymers. Investigations into the chemical composition, morphology and stability of the plasma-polymerized films in aqueous environments and other testing setups are carried out, in order to examine their functionality and validate them for industry-related applications.
Chemically patterned surfaces in the submillimeter to micrometer range are proving to be a particularly valuable platform in microfluidics.For many modern diagnostics, fluid volumes are now in the microliter or even nanoliter range. This allows microfluidics to drastically reduce sample and reagent volumes, run reactions faster, and thus increase throughput and enable resource-conserving measurements. Increased interest is therefore being shown in the use of multiplex arrays whereby a large number of analytes can be processed simultaneously on a single microchip. This requires areas of defined chemical and physical properties which can be generated on any surface, for example, by means of a plasma printing process developed in the RG BSO, called SurfAP3®. This innovative process enables site-selective deposition of plasma polymer coatings with structural dimensions from 50 to 250 μm and layer thicknesses in the range of 20 to 150 nm, using an atmospheric pressure plasma jet and method developed at INP.
In addition, by means of SurfAP3® it is possible to enable and envision plasma-assisted microfabrication techniques at atmospheric pressure, suitable for applications in microelectronics, flexible electronics, microfluidics, bioelectronics and additive manufacturing.
Hydrogels are predestined for applications in microfluidics and medical technology due to their stimuli-responsive properties. In addition, hydrogel layers are suitable for the development of biomedical (implantable) sensors due to their high water content and tissue-like mechanical properties and the associated biocompatibility.
The work of the BSO research group involves the synthesis of hydrogel layers using plasma polymerization at atmospheric pressure. For example, acrylate-based hydrogel layers of thicknesses up to 10 µm could be generated, which show controlled and reversible swelling behavior depending on the pH value. Furthermore, investigations have shown that the specific adjustment of the layer thickness and the associated characteristic wrinkling favors the immobilization of biomolecules. The characterization of the produced layers and their deposition on screen-printed electrodes have showed their practical application on electrochemical biosensing, for example when used for the detection of glucose and the parasympathomimetic alkaloid eserine.