Research home

Dan Cojoc

OM-Lab
 
Optical manipulation and imaging

Dan CojocSenior Scientist at IOM-CNR
 

Dan Cojoc is a senior scientist at the National Research Council of Italy (CNR), Institute of Materials (IOM) in Trieste, Italy. Since 2008, DC is the coordinator of the Optical Manipulation (OM) Lab, of which aim is to develop advanced optical techniques and instrumentation for applications in bio-nanotechnology, biophysics and biomedicine.

Expertise: optical manipulation of biological particles, functionalized nanoparticles and living cells using optical tweezers and laser microsurgery; fluorescence microscopy (live cell imaging, TIRF, FRET, nanoscopy); live cell quantitative phase microscopy; fluorescence microscopy (live cell imaging, TIRF, FRET, nanoscopy); photonic force microscopy; microRaman spectroscopy; Fourier optics and diffractive optical elements; phase contrast X-ray microscopy; microfabrication.

Scientific interests: cell signaling, cell mechanics, neurobiology, cancer cell biology.

DC has published more than 100 papers in international peer-reviewed journals and conference proceedings, 10 books/chapter as author/editor, and holds 2 international patents. DC’s OM-Lab web page: http://dancojoc.wix.com/om-lab

 

Research Lines

In collaboration with SISSA

Focal stimulation and cell signaling in neurons

It is known that cells in general, and neurons in particular, communicate releasing signaling biomolecules which are intercepted and interpreted by nearby cells. Guidance cues (Ephrin, Netrin, Sempahorin, Slit) is just an example for neurons, but there are many other cellular structures that can be released by cells, as for instance the extracellular vesicles (EV). EV are membrane structures carrying proteins, lipids, and nucleic acids, which are transferred between cells by different mechanisms, such as endocytosis, macropinocytosis, or fusion. On the other hand it is also known that the effect induced by a signaling molecule depends of which cell compartment is reached and of the receptors present on the membrane. Still another important characteristic of cell signaling is the spatial-temporal gradient of the molecules which cannot be implemented by bath administration of molecules, as it is the case of almost all the lab experiments studying such signaling molecules. Our goal is to create experimental likely physiological conditions by means of optical manipulation. We developed an approach in which the molecules loaded into vectors (functionalized beads or nanoparticles, liposomes) or EVs are precisely positioned with respect to the cell by using optical tweezers. In the case of liposomes we use a pulse laser o brake the membrane of the liposome and release the molecules. Focal stimulation by locally releasing active molecules is followed by time lapse phase contrast microscopy to monitor the effect induced to the cell, and fluorescence calcium imaging. This technique allows a quantitative evaluation of the number of molecules reaching the cell, and understand how many molecules are necessary to induce a certain effect. Recently we implemented also time lapse FRET microscopy which allows to monitor the activation of small RhoGTPases as RhoA and CDC42 (Iseppon F. et al, Frontiers Cell Neuroscience 2015). In the future we are interested in developing new vectors allowing a flexible control of the spatial-temporal gradient, and new imaging techniques to monitor different mediators of the signaling pathway playing a role in the cytoskeleton organization.

Mechanotrasduction in neurons

Beside the biochemical stimulation, cells are subject to mechanical stimuli exerted by other cells and the extracellular matrix. In the last two decades cell signaling by mechanical stimuli (mechanotransduction) has been received increasing consideration mainly because of its evidence and implications in cancer cell and neurobiology. We have shown that filopodia and lamellipodia of the growth cones exert forces during the neuronal development (Cojoc et al PlosOne 2007) and we measured them by optical tweezers force microscopy. Recently, in order to further understand the mechanisms of mechanotransduction in neurons we have developed a technique based on optical tweezers and force microscopy in which we apply piconewton forces to specific places of the neuron and monitor the biological effect using techniques similar to the project presented above. In the future we want to implement also quantitative phase microscopy (or digital holographical microscopy) to render the profile of the cell and its dynamics in three dimensions.

Selected publications

Sci. Rep. 6, art. no. 21629 (2016). DOI: 10.1038/srep21629

Glucose is a key driver for GLUT1-mediated nanoparticles internalization in breast cancer cells

Venturelli L, Nappini S, Bulfoni M, Gianfranceschi G, Dal Zilio S, Coceano G, Del Ben F, Turetta M, Scoles G, Vaccari L, Cesselli D, Cojoc D

Front. Cell. Neurosci. 9:333 (2015). DOI: 10.3389/fncel.2015.00333

Cdc42 and RhoA reveal different spatio-temporal dynamics upon local stimulation with Semaphorin-3A

Iseppon F, Napolitano LMR, Torre V and Cojoc D

International Journal of Molecular Sciences 2013, 14, 8963-8984

Cell Signaling Experiments Driven by Optical Manipulation.

Francesco Difato, Giulietta Pinato and Dan Cojoc

Biomedical Optics Express 2012, 3, 991-1005

Toward fast malaria detection by secondary speckle sensing microscopy.

Dan Cojoc, Sara Finaurini, Pavel Livshits, Eran Gur, Alon Shapira, Vicente Mico, and Zeev Zalevsky

 
 

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