Apl. Prof. Dr. Rainer Müller

Short biography

Rainer Müller was born on December 22, 1968 in Schrobenhausen, Bavaria (Germany). He studied chemistry at the University of Regensburg where he graduated in February 1995. His diploma-thesis was entitled "Synthesis and physicochemical characterization of biologically degradable cationic polyelectrolytes" and was prepared at the Institute of Physical and Macromolecular Chemistry under supervision of Professor Klaus Heckmann. He obtained his PhD in February 1998 at the Laboratory of Interface Chemistry which was the follow-up institution after Professor Heckmann?s retirement. The PhD-thesis was entitled "Synthesis of corrosion-inhibiting coupling agents for microelectronic devices".

After attaining his doctoral degree, Rainer Müller was scientific co-worker at the Laboratory of Interface Chemistry where he established a research group focused on colloid and interface chemistry with special emphasis on biomaterials and tissue engineering. In December 2000 he became scientific assistant at the Institute of Physical and Theoretical Chemistry of the University of Regensburg headed by Professor Werner Kunz starting his habilitation work. He initiated several co-operations with the Departments of Trauma Surgery, Operative Dentistry, and Neurology of the University Hospital of Regensburg and other university institutes which were funded by the Deutsche Forschungsgemeinschaft (DFG) or by the Bavarian State Ministry of Sciences, Research and the Arts. In November 2009 he finished his habilitation-thesis entitled "Chemical modification of biomaterial surfaces and scaffolds to direct biological responses in regenerative medicine".

Since August 2011 Rainer Müller is senior research assistant at the Institute of Physical and Theoretical Chemistry of the University of Regensburg. He gives lecture courses, tutorials and laboratory classes for undergraduate students of chemistry, biochemistry and biology. In October 2016 he was appointed 'Au?erplanm??iger Professor' at the University of Regensburg.

Teaching

Apl. Prof. Dr. Rainer Müller

University of Regensburg

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Chemistry Undergraduates

• Tutorial Mathematical Methods in Physical Chemistry (2. Sem., summer term)
• Tutorial Thermodynamics Part 1 (2. Sem., summer term)
• Tutorial Chemical Kinetics (2. Sem., summer term)
• Tutorial Thermodynamics Part 2 (3. Sem., winter term)
• Tutorial Electrochemistry (3. Sem., winter term)
• Laboratory Course Physical Chemistry Part 1 (3. Sem., winter term)
• Seminar to Laboratory Course Physical Chemistry Part 1 (3. Sem., winter term)
• Laboratory Course Physical Chemistry Part 2 (4. Sem., summer term)

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Chemistry Graduates

• Lecture Physical Chemistry of Biological Interfaces and Biomaterials (7. Sem., winter term)
• Laboratory Course Physical Chemistry Part 3 (Kurspraktikum, Vertiefungspraktikum), Adsorption Isotherms (8. Sem., summer term)
• Laboratory Course Formulation (8. Sem., summer term)
• Research Internship (7./8.Sem. winter or summer term)

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Teachers of Chemistry

• Lecture and Tutorial Physical Chemistry – Introduction to thermodynamics, kinetics, surface chemistry and electrochemistry (3./5. Sem., winter term)
• Laboratory Course Physical Chemistry (4./6. Sem., summer term)
• Seminar to Laboratory Course Physical Chemistry (4./6. Sem., summer term)

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Biochemistry and Biology Undergraduates

• Lecture and Tutorial Physical Chemistry – Introduction to thermodynamics, kinetics, surface chemistry and electrochemistry (3. Sem., winter term)
• Laboratory Course Physical Chemistry (4. Sem., summer term)
• Seminar to Laboratory Course Physical Chemistry (4. Sem., summer term)

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Teaching

Privat-Dozent Dr. Rainer Müller

University of Regensburg

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Research in the Work Group of Rainer Müller, Department of Physical Chemistry

Contributions of Colloid and Interface Chemistry to Biomaterials Science and Regenerative Medicine

Biomaterial science aims to develop man-made materials and living tissues for replacing the physical and biological function of injured or diseased tissues in the human body. A broad understanding of material science and human biology is a prerequisite for the development of materials which not only exert certain structural and mechanical properties, but are also compatible with the biological system in which they are implanted. In addition, an understanding of the surface chemistry of materials is also very important since this is a main determinant for biocompatibility. The goal of material-based regenerative medicine has changed from using materials, which only match the physical properties of the replaced tissue combined with a minimal toxic response in the host, to the design of bioactive and biodegradable materials. Members of the so-called ‘third-generation biomaterials’ should instead be able to elicit specific desired responses from the surrounding tissues at the molecular level. Methods of colloid and surface chemistry play an important role in the design of new biomaterials, especially by improving the surface performance of materials and creating biocompatible three-dimensional guiding structures. Advances in surface science and molecular biology must be combined in order to understand how surface properties control the biological response of a tissue interacting with this surface.

Fig. 1: Potential applications of colloid and surface chemistry in context with biomaterials science.

Influence of Biomaterial Surface Characteristics on Biological Processes

We investigate the influence of physicochemical surface parameters of biomaterials on the adsorption of proteins and the adhesion of eukaryotic and bacterial cells. Together with the Department of Operative Dentistry and Periodontology (UR) we developed new chemiluminescence- and fluorescence-based assays for the quantification of proteins and bacteria attached to surfaces of low specific area. In our group, silicon-based model surfaces with varying degrees of surface wettability, surface charge, and topography were prepared to study the impact of these parameters on biological systems interacting with these surfaces.

Fig. 2: Physicochemical properties of silicon-based model surfaces.

Using our model system, we identified certain surface chemical groups to which eukaryotic cell adhesion was different compared to bacterial cell binding. Surface modification with short-chain poly(ethylene glycol) moieties allowed adhesion of anchorage-dependent osteoblasts and fibroblasts, while binding of pathogenic bacteria was significantly inhibited. In contrast, surfaces modified with fluorocarbon moieties promoted attachment of bacteria but inhibited adhesion of eukaryotic cells. Moreover, we manufactured surfaces which clearly exerted antibacterial properties. Surface modification with cationic pyridinium group-containing molecules did in fact allow binding of oral bacterial strains but killed these bacteria almost completely on contact. We could show that even more than surface chemistry and topography, the adsorption of proteins to a substrate surface most significantly influenced the response of the contacting biological system. Pre-adsorption of cell adhesive proteins most often increased eukaryotic cell adhesion and subsequent cellular responses, although it also enhanced the potential of undesirable bacterial processes. In this context, surfaces pre-conditioned with saliva proteins were shown to increase the attachment of oral bacteria and, with the most definitive consequences, abolish the bactericidal efficiency of cationic surface modifications.

Fig. 3: Cell adhesion and bacterial viability on differently modified silicon-based model surfaces.

Based on these findings, follow-up research in our group focused both on the development of antibacterial surface coatings that additionally resist protein adsorption and on the surface modification of implant materials to specifically increase eukaryotic cell adhesion. These new surface coatings, which are based on dendrimers, are currently being investigated in cooperation with the Department of Oral Biology, State University of New York at Buffalo and the Division Cell Biology of the Center for Medical Research of the University of Rostock.

Fig. 4: Dendrimers as new type of biomaterial coating.

Literature: S. St?hlke et al. Materials Science & Engineering C, 2019, 101, 190-203, H. Schweikl et al. Dental Materials 2013, 29, 1080-1089, V. Katzur et al. Journal of Colloid and Interface Science 2012, 366, 179-190, M. Eichler et al. Biomaterials 2011, 32, 9168-9179, R. Müller et al. Biomaterials 2009, 30, 4921-4929, R. Müller et al. Journal of Biomedical Materials Research A 2008, 84, 817-827, H. Schweikl et al. Journal of Material Science Materials in Medicine 2007, 18, 1895-1905, R. Müller et al. Applied Environmental Microbiology 2007, 73, 2653-2660, R. Müller et al. Analytical Biochemistry 2006, 359, 194-202.

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Capillary Hydrogels for Neural Tissue Regeneration

We employ delicate colloid chemical procedures to prepare three-dimensional scaffolds exhibiting a highly exclusive porous structure. Although the natural polyelectrolyte alginate has been used in many biomedical disciplines for some time, the very specific feature this colloid system is able to exert has remained unrecognized in the field. It was the German colloid chemist Heinrich Thiele who discovered the formation of highly anisotropic capillary hydrogels, in which water-filled capillaries of round shape are aligned parallel to each other with a capillary density of up to 1000 per mm², by a simple ion-driven process. We are the first to utilize this specialized structure for biomedical applications with the intention of preparing a guiding structure to conduct the regeneration of injured nerves. We could show that the variation of experimental parameters allowed us to specifically modify the anisotropic alginate gels with respect to their capillary diameter and capillary density. The capillary diameter can be defined within 10 and 200 ?m and we contend that this parameter will exert a significant influence on the capability of capillary hydrogel-guided axon regeneration. In collaboration with the Spinal Cord Injury Center of the Heidelberg University Hospital we are currently investigating these gels with regard to their capacity to guide disrupted nerve axons in the central or peripheral nerve system.