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Dr. Aneta Keliris (geb. Brud)

Adresse: Spemannstr. 41
72076 Tübingen
Raum Nummer: 4.B.10
Tel.: 07071 601 731
Fax: 07071 601 702
E-Mail: aneta.brud

 

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

Aneta Keliris (geb. Brud)

Position: Postdoc  Abteilung: Scheffler

Development of enzyme-responsive multimodal probes


Goal: The aim of this project is to develop a versatile multimodal imaging platform for monitoring the enzyme activity that would allow assessment of cellular events associated with gene expression and monitoring neuronal stem cells after their transplantation.

 

An enormous number of biochemical processes taking place in living organisms demands the action of enzymes. These highly specific essential catalysts serve as indicators of diseases (e.g. stroke, brain tumors), cellular processes and are used as essential markers of gene expression. Hence, real-time non-invasive in vivo mapping of enzyme activity can provide a means for the assessment of disease processes, evaluation of novel therapies (e.g. gene and neuronal stem cell therapies), and also better understanding of biochemical events vital for sustaining life. More specifically, we are developing probes that upon interaction with β-galactosidase enzyme, expressed by LacZ reporter gene, produce the characteristics detectable by 1H/19F MRI and optical imaging modalities. Such a multimodality approach for enzyme detection is expected to integrate the advantages and conquer the individual limitations of the different imaging technologies.

Methods

Dual-modal β-gal targeting imaging probes were obtained in a multi-step synthesis and fully characterized by analytical methods. Proton T1, T2 relaxation times in probe solutions and cellular relaxation rates of labeled cells were determined at 123 MHz and 300 MHz. 19F T1, T2 relaxation times and 19F images were acquired at 282 MHz. Cellular uptake of probes in C6/LacZ (β-gal containing) and C6 (no target) glioma cells was investigated by fluorescence spectroscopy, microscopy and MR measurements of labeled cells.

Results

Our initial work towards developing β-gal activable dual-modal probes focused on cell-permeable MR/optical probes whose activation by enzyme was based on a cellular retention strategy of imaging reporters in the β-gal expressing cells. This retention was achieved via enzymatic cleavage of a delivery vector following Gd-DOTA-k(FITC)-Gal-CPP probe internalisation. Although higher accumulation of imaging reporters in C6/LacZ cells compared to the C6 cells was shown [1], providing the proof of principle for the proposed strategy, a non-specific background signal in the β-gal-deficient cells was also observed due to predominantly vesicular localisation of unconverted probe restricting its fast efflux from these cells.To provide further advances and overcome the problem of non-specific background signal we are currently focusing on developing of β-gal responsive probes that show turn- on signal only upon enzymatic conversion. The first representative of this series, dual-modal 19F and 1H MRI probe (Gd-DOMF-Gal) [2] with a self-immolative linker was synthesized. The efficient enzymatic conversion of Gd-DOMF-Gal by β-gal resulted in the simultaneous turning-on of the initially quenched 19F MRI 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). With this molecular design we provided an efficient tool for monitoring β-gal activity by means of 1H and 19F MRI.

 

Conclusions

The presented here results indicate that our bimodal probes could be specifically activated in the presence of targeted enzyme. Further, Gd-DOMF-Gal as 1H/19F MRI probe with its remarkable characteristics will be now tested in vivo. Further developments towards novel probes responsive to other enzymes are also in progress.

References:

Keliris A., Ziegler T., Mishra R., Pohmann R., Sauer M., Ugurbil K., Engelmann J.: Biorganic & Medicinal Chemistry 19(8) 2529-2540 (2011).

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

 

 

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.

 

 

Development of catecholamine-sensing MRI probes


Goal: The goal of this project is to develop a new class of catecholamine-sensing MRI-detectable probes (contrast agents). The ability of such probes to affect the relaxation times in their surroundings is reversibly modulated in response to the dynamic changes in extracellular levels of catecholamine (dopamine or norepinephrine) during task dependent neuronal activity.

 

 

Catecholamines such as dopamine or norepinephrine are principal neurotransmitters that act as the chemical messengers of information between different brain cells. These communication agents mediate various central nervous system functions such as cognition, motor control, emotion, reward or memory processing. The ability to detect the fluctuation in catecholamine concentration would provide means for direct monitoring of neuronal processing, but also can be of critical importance for understanding the dysfunctions in catecholamine systems connected with several neurologic and neuropsychiatric disorders (e.g. Parkinson’s disease, depression). In this line, we are currently developing dopamine-responsive MRI probes based on the lanthanide complexes with specific recognition sites. The presence of catecholamine would induce changes in the observed MR signal as the result of modulation of parameters governing the relaxivity of contrast agents such as hydration number (model A) or rotational correlation time (model B).

 

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Artikel (4):

Keliris A Person, Mamedov I Person, Hagberg GE Person, Logothetis NK Person, Scheffler K Person und Engelmann J Person (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 Person, Ziegler T , Mishra R Person, Pohmann R Person, Sauer M , Ugurbil K und Engelmann J Person (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 Person 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 Person, 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.

Poster (8):

Hagberg GE Person, Keliris A Person, Mamedov I Person, Placidi M Person, Merkle H Person, Logothetis NK Person und Scheffler K Person (April-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.
pdf
Keliris A Person, Mamedov I Person, Hagberg GE Person, Logothetis NK Person, Scheffler K Person und Engelmann J Person (September-2012): Dual 1H/19F MR imaging approach for detection of enzyme activity, Fifth Annual World Molecular Imaging Congress (WMIC 2012), Dublin, Ireland.
Brud A Person, Mishra R Person, Engelmann J Person, Su W Person, 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.
Mishra R Person, Su W Person, Brud A Person, Sauer MG , Pfeuffer J Person, Ugurbil K und Engelmann J Person (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.
pdf
Brud AJ Person, Mishra R Person, Ugurbil K , Ziegler T und Engelmann J Person (September-2008): Evaluation of an Intracellular Contrast Agent Targeting Beta-Galactosidase for Cellular Labeling, 2008 World Molecular Imaging Congress (WMIC), Nice, France.
pdf
Engelmann J Person, Su W Person, Brud A Person, Mishra R Person, 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 Person, Engelmann J Person, 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 Person, Engelmann J Person, 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.
pdf

Vorträge (3):

Keliris A Person (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 Person (2010): Assessment of Intracellular Targets with MRI, CMST COST Action D38: Metal-Based Systems for Molecular Imaging Applications, Tübingen, Germany.
Brud A Person, Mishra R Person, Ugurbil K , Su W Person, Ziegler T und Engelmann J Person (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: Freitag, 17.01.2014