Dr. Aneta Keliris (geb. Brud)

Adresse: Spemannstr. 41
72076 Tübingen
Raum Nummer: 4.B.10
Tel.: 07071 601 717
Fax: 07071 601 702
E-Mail: aneta.brud


Bild von Keliris (geb. Brud), Aneta, Dr.

Aneta Keliris (geb. Brud)

Position: Gastwissenschaftler  Abteilung: Scheffler

My research is focused on development of targeted and responsive multimodality MRI probes for non-invasive in vivo visualization of key target molecules being specific markers of distinct cellular and physiological processes. Currently, this primarily involves enzyme-activity imaging and cell tracking applications.


Enzyme-responsive MRI probes

An enormous number of biochemical processes taking place in living organisms demand the action of enzymes. These highly specific catalysts serve as indicators of diseases (e.g. stroke, brain tumors, inflammations), cellular processes and are used as essential markers of gene expression.

Aim of this project is to develop a versatile multimodal imaging platform for in vivo mapping of enzyme activity in real-time that would allow: early disease diagnosis, assessment of cellular events associated with i.e. gene expression, or monitoring neuronal stem cells via reporter gene strategy after their transplantation. Here, “switched off/on” fluorinated MRI probes are developed, which remain silent in the absence of enzyme and only in the presence of enzyme produce the signal detectable by MRI. Importantly such approach allows detection of enzyme activity with a large MR signal amplification and without perturbation to biological process of targeted enzyme since its complete recovery is taking place after each cycle of enzymatic conversion of probe.

In this line, 1H/19F MRI probe, Gd-DOMF-Gal, responsive to β-galactosidase (β-gal) enzyme, expressed by the LacZ gene most widely used reporter genes in transgenic studies, was successfully developed and characterized. Accordingly, Gd-DOMF-Gal showed upon enzymatic conversion a simultaneous “switching-on” of the initially quenched 19F MR signal (Fig 1a) and changed the ability of the cleaved Gd3+complex (Gd-DOM) to modulate the 1H MR signal intensity of the surrounding water (Fig 1b). Specific activation of Gd-DOMF-Gal has been proven in vitro (phantoms, cells) and lately being investigated in in vivo studies with mice bearing β-galactosidase expressing tumor xenografts (in collaboration with MPI for Metabolism Research, Cologne). Another responsive 1H/19F MRI probes that have been recently developed by following this research line,  are sensing the activity of matrix metalloproteinase (MMP-2), an enzyme overexpressed in almost every type of human cancer and being marker of inflammation.  With proposed molecular design an efficient tool was provided for monitoring enzymes activity by means of 1H /19F MRI. Such a multimodality approach for enzyme detection is expected to integrate the advantages and conquer the individual limitations of the different imaging technologies.




Figure 1. 19F MRI images (left) and the corresponding proton T1 relaxation map (right image) acquired at 7 T (~25°C). Gd-DOMF-Gal (0.96 mM) was incubated in the absence or presence of β-gal in PBS reaction buffer at 37°C for the indicated time periods.


Keliris A., Mamedov I., Hagberg G., Logothetis N.K., Scheffler K., Engelmann J., Contrast Media & Molecular Imaging,  7(5) 478–483 (2012).



Cell tracking by 19F MRI

Stem cells based therapies endow modern medicine with a powerful tool for treatment of many severe diseases such as cancer, neurodegenerative disorders, acute CNS disorders or diabetes that immensely affect the life of millions of people worldwide today. The basic idea of such therapies is that cells provided with a specified function should act as a “therapeutic drug” after they are transferred into a living subject (i.e. restore damaged tissues, recognize inflammation sites, fight diseases or help to cure genetic disorders). Recent years have seen a huge progress in development of these therapies, particularly in preclinical work. Despite this showcased promise of cure, the effectiveness of cell therapies is still much far from being ideal and their translation into clinical practice proved to be very difficult. This is mainly due to the current inability to adequately answer the critical questions about the fate of the transplanted cells in vivo i.e. distribution, survival. To address this, highly efficient tools are needed that would enable to follow cells in vivo. Among various imaging techniques, MRI is nowadays a modality of choice for tracking stem cells longitudinally and non-invasively in vivo. This approach requires, however, high efficiency MRI probes that do not affect the function of the stem cells and at the same guarantee their specific, quantitative and long-term detection after transplantation. Recently, after a dominance era of iron oxide nanoparticles, the use of 19F MRI probes has emerged for in vivo cell tracking in order to overcome the drawbacks of signal ambiguity often faced with 1H MRI T2/T2* contrast agents, and enable reliable cell quantification.

Aim of this project is to provide tools for reliable evaluation of efficacy of cell-based therapies in vivo through developing multimodal 1H/19F MRI-optical probes for stem cells labeling and establishment of MR methods for their efficient and long-term detection after transplantation.

In this line, we have prepared 19F PLGA nanoparticles 19F PLGA-NPs (PLGA=poly(D,L-lactide-co-glycolide) of various compositions, with and without surface modifications, loaded with perfluoro-15-crown ether (PFCE) and/or optical dye (i.e. carboxyfluorescein), and/or Gd-DOTA like complex . In our extensive in vitro studies, human mesenchymal stem cells (hMSCs) as well as mouse CD4+ T-cells were efficiently labeled with fluorinated nanoparticles without affecting their properties (i.e. proliferation kinetics, colony generation, adhesion, surface migration, and presence of stem-cell markers). Further, MR methods were optimized in vitro for efficient detection of labeled cells and estimation of method sensitivity (Dr. Gisela E. Hagberg).  Here, MRI detection limit for hMSCs cell load of 0.4x1012 19F/cell was 20.000 cells (pellet) or 10.000 cells per microliter (suspension) in a 2h scan. We are now on the way with in vivo testing of established methods, for instance in the treatment of urinary incontinence with hMSCs in collaboration with the University Hospital Tübingen.

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Artikel (4):

Keliris A, Mamedov I, Hagberg GE, Logothetis NK, Scheffler K und Engelmann J (September-2012) A smart 19F and 1H MRI probe with self-immolative linker as a versatile tool for detection of enzymes Contrast Media & Molecular Imaging 7(5) 478–483.
Keliris A, Ziegler T, Mishra R, Pohmann R, Sauer M, Ugurbil K und Engelmann J (April-2011) Synthesis and Characterization of a Cell-Permeable Bimodal Contrast Agent Targeting β-Galactosidase Biorganic & Medicinal Chemistry 19(8) 2529-2540.
Barbasiewicz M, Brud A und Makosza M (April-2007) Synthesis of Substituted Tetrahydropyrans via Intermolecular Reactions of δ-Halocarbanions with Aldehydes Synthesis 2007(8) 1209-1213.
Groszek G, Blazej S, Brud A, Swierczynski D und Lemek T (März-2006) Reactions of carbanions derived from α-substituted-methyl tolyl sulfones with quinone methides as Michael acceptors Tetrahedron 62(11) 2622-2630.

Beiträge zu Büchern (1):

Keliris A, Scheffler K und Engelmann J: Responsive Probes for 19F MRS/MRI, 141-170. In: Fluorine Magnetic Resonance Imaging, (Ed) U. Flögel, Pan Stanford Publishing, Singapore, (2016).

Poster (14):

Hagberg GE, Keliris A, Srinivas M, Schulz H, Engelmann J, Schmehl J, Bantleon R und Scheffler K (März-19-2015): Characterization and MRI detection of 19F-PLGA labelled human mesenchymal stem cells, 10th Annual Meeting of the European Society for Molecular Imaging (EMIM 2015), Tübingen, Germany.
Keliris A, Engelmann J, Hagberg GE und Scheffler K (März-19-2015): Self-assembling peptide based system for detection of enzymatic activity by means of MRI, 10th Annual Meeting of the European Society for Molecular Imaging (EMIM 2015), Tübingen, Germany.
Hagberg GE, Keliris A, Mamedov I, Placidi M, Merkle H, Logothetis NK und Scheffler K (April-23-2013): 19F-Lanthanide Complexes: T1 - and T2 - Dependent Signal Gain Using Gradient Echoes, 21st Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2013), Salt Lake City, UT, USA.
Keliris A, Mamedov I, Hagberg GE, Logothetis NK, Scheffler K und Engelmann J (November-2012): Dual 1H/19F MR imaging approach for detection of enzyme activity, Fifth Annual World Molecular Imaging Congress (WMIC 2012), Dublin, Ireland, Molecular Imaging and Biology, 14(2 Supplement) S1235.
Hagberg GE, Mamedov I, Placidi M, Keliris A, Merkle H, Logothetis NK und Scheffler K (Oktober-29-2012): 19F-Lanthanide complexes: T1- and T2-dependent signal gain using gradient echoes, ENCITE Symposium "Red hot MRI: In vivo 19F imaging", Nijmegen, The Netherlands.
Keliris A, Engelmann J und Scheffler K (September-2011): Development of multimodal probes targeting β-galactosidase, COST D38 Final Meeting: Metal-Based Systems for Molecular Imaging Applications, Oxford, UK.
Engelmann J, Keliris A, Ziegler T, Mishra R, Pohmann R, Sauer MG und Ugurbil K (Juni-2011): A cell-permeable, β-galactosidase targeted contrast agent for optical and MR imaging, 6th European Molecular Imaging Meeting (EMIM 2011), Leiden, The Netherlands.
Brud A, Mishra R, Engelmann J, Su W, Ziegler T und Ugurbil K (2011): Intracellular MR Contrast Agents with Enzymatically Cleavable Part for Molecular Imaging, CMST COST Action D38: Metal-Based Systems for Molecular Imaging Applications, Tübingen, Germany.
Brud A, Mishra R, Ugurbil K, Ziegler T und Engelmann J (April-2009): Bimodal intracellular contrast agent based on the sugar moiety targeting beta-galactosidase, COST Action D38 Annual Workshop: Metal-Based Systems for Molecular Imaging Applications, Warsaw, Poland.
Mishra R, Su W, Brud A, Sauer MG, Pfeuffer J, Ugurbil K und Engelmann J (September-2008): Cell Penetrating Peptides Delivering Intracellular Targeted Agents for Molecular Imaging, 30th European Peptide Symposium (30 EPS), Helsinki, Finland, Journal of Peptide Science, 14(S1) 154-155.
Brud AJ, Mishra R, Ugurbil K, Ziegler T und Engelmann J (September-2008): Evaluation of an Intracellular Contrast Agent Targeting Beta-Galactosidase for Cellular Labeling, 2008 World Molecular Imaging Congress (WMIC), Nice, France.
Engelmann J, Su W, Brud A, Mishra R, Pfeuffer J und Ugurbil K (2008): Intracellular Targeted Agents for Molecular Imaging, CMST COST Action D38: Metal-Based Systems for Molecular Imaging Applications, Tübingen, Germany.
Brud A, Engelmann J, Pfeuffer J, Ziegler T und Ugurbil K (April-2006): Optical/MR Contrast Agents: Enzyme Activity and Relaxivity Studies, COST Chemistry Action D18: Lanthanide Chemistry for Diagnosis and Therapy, Orléans, France.
Brud A, Engelmann J, Pfeuffer J, Ziegler T und Ugurbil K (September-2005): Development and Synthesis of Optical/MR Contrast Agents for Detection of beta-Galactosidase Activity, 4th Annual Meeting of the Society for Molecular Imaging (SMI 2005), Köln, Germany, Molecular Imaging, 4(3) 378-379.

Vorträge (5):

Keliris A, Hagberg GE, Engelmann J und Scheffler K (Mai-26-2013) Abstract Talk: Dual modality approach for detection of enzyme activity by means of 1H/19F MRI, 8th European Molecular Imaging Meeting (EMIM 2013), Torino, Italy(298).
Keliris A (November-8-2012) Invited Lecture: Classes of MRI Contrast Agents and Chemical Modifications Enabling Functional Neuroimaging, Hands-on Workshop “Cell tracking with MRI“: The method of choice for preclinical investigations of revealing cell dynamics in vivo, Köln, Germany.
Keliris A (September-2011): Fluorine-labeled paramagnetic complexes as versatile tool for detection of enzymes for 19F and 1H MRI, ENCITE Hot Topic Workshop “19F in vivo MRI”, Köln, Germany.
Brud A (2010): Assessment of Intracellular Targets with MRI, CMST COST Action D38: Metal-Based Systems for Molecular Imaging Applications, Tübingen, Germany.
Brud A, Mishra R, Ugurbil K, Su W, Ziegler T und Engelmann J (Juli-2008) Abstract Talk: Targeted Intracellular Contrast Agents Based on Enzymatically Cleavable Part: Potential MRI Cell Tracking System, 35th Annual Meeting and Exposition of the Controlled Release Society 2008, New York, NY, USA.

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Last updated: Dienstag, 18.11.2014