Dr. Felix Löffler
- [sci.] Gruppenleiter am Max-Planck-Institut für Kolloid- und Grenzflächenforschung
- Physik
Microarray Technology and Application - Gruppe: [prev.] Carl Zeiss
- Raum: Deutschland, Potsdam
Current research
Which antibodies protect from infections? And which ones are useless or even harmful? If we would know, where antibodies have to bind to a pathogen to protect us, we could design a targeted vaccine or therapy with this knowledge.
Depending on the sequence of their 20 different amino acid building blocks, peptides (= small protein fragments) are a major class of antibody binders, which qualifies them to be used as diagnostic biomarkers or therapeutics. Therefore, a large set of different peptides has to be synthesized and screened in order to find e.g. novel biomarkers.
Our current research topics in microarray technology and application are:
- Development of matrix-based array technology (Physics, Engineering, Chemistry)
- Antibody profiling for infectious diseases (Biomedical research, Bioinformatics)
Application of microarrays
We employ novel high-density peptide arrays for the screening of patient sera. The principle is illustrated in Figure 1: The microarray slide with the immobilized molecule library (a) is incubated with a small amount of analyte (b). The fluorescently labeled analytic molecules bind to the surface, which is visible in the fluorescence image of the microarray (c).
Fig. 1. Principle of a patient serum analysis using a peptide array.
For a comprehensive serum readout regarding e.g. the malaria parasite Plasmodium falciparum, we translate the genomic information from databases into sequences of overlapping peptides (Fig. 2). These peptides are then synthesized on arrays and stained with patient sera.
Fig. 2. Generating a peptide array from overlapping proteome fragments of a pathogen.
Technology development
High-density peptide arrays represent an attractive method for high-throughput identification of peptide-protein interactions. They are essential to reduce the consumption of reagents required for the binding assay and, thus, save rare serum samples or expensive proteins. However, today's peptide array market is still dominated by the over 20 year old SPOT synthesis, which provides only low spot densities and achieves at most a few hundred spots per cm² if pre-synthesized peptides are spotted.
We developed a novel method of peptide array synthesis, which combines the high spot densities achieved by light-controlled lithographic methods with the cost-efficiency of one-cycle-per-layer coupling in biofunctional xerography.
Fig. 3. Selective combinatorial laser fusing for combinatorial peptide synthesis.
First, a homogenous layer of one particle type (with one kind of amino acid embedded within) is deposited onto a functionalized glass substrate. Subsequently, the layer is selectively irradiated with a laser beam (Fig. 3A), whereby the particles within the laser beam focus fuse together on the surface. Due to surface tension, the fused particle matrix forms a very small hemisphere, with its size being dependent only on the particle size and on the focus of the laser beam. Afterwards, unfused particles are simply blown away from the glass slide, whereas fused spots remain on the substrate due to much higher adhesion (Figure 3B). Repeating the patterning step with different particle types, results into a pattern of spots each comprising a freely chosen amino acid (Figure 3C).
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Fig. 4. Coupling reaction of monomers after combinatorial laser fusing. |
Although laser radiation heats and fuses the polymer matrix in order to form the distinct reaction hemispheres (Figure 4A), the laser pulse duration is too short to accomplish the coupling reaction. For an efficient diffusion and coupling of the amino acids to free amino groups on the surface, the complete layer of structured amino acid particles is heated to 90°C for several minutes (Figure 4B). At this temperature, the matrix material within the particles liquefies, and, thereby, serves as a solvent for peptide synthesis. Afterwards, the particle matrix and unreacted monomers are washed away (Figure 4C), and the transient protecting groups are removed to reveal free amino groups for the next synthesis layer (Figure 4D). Repeating this cycle for e.g. 13 consecutive layers results into an array of 13meric peptides.
Curriculum vitae
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Young Investigator |
Institute of Microstructure Technology, Karlsruhe Institute of Technology, Germany |
Since 07/2014 |
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Visting Scholar |
UC Berkeley, USA |
01/2014 – 06/2014 |
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Postdoctoral fellow |
Institute of Microstructure Technology, Karlsruhe Institute of Technology, Germany |
10/2012 – 12/2013 |
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Postdoctoral fellow |
German Cancer Research Center Heidelberg, Germany |
05/2012 – 10/2012 |
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PhD |
Kirchhoff Institute of Physics & German Cancer Research Center Heidelberg, Germany |
10/2009 – 04/2012 |
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Physics diploma and certificate in biophysics |
Heidelberg University, Germany |
10/2004 – 09/2009 |
Top publications
List of publications
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