Research home

Dan Cojoc

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:


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

(2018) Frontiers in Cellular Neuroscience, 12, art. no. 130.

Cell mechanotransduction with piconewton forces applied by optical tweezers

Falleroni, F., Torre, V., Cojoc, D.

(2018) Applied Optics, 57 (1), A242.

Single-shot, dual-mode, water-immersion microscopy platform for biological applications

Picazo-Bueno, J.Á., Cojoc, D., Iseppon, F., Torre, V., Micó, V.

Front Cell Neurosci. 2017 Dec 18;11:402.

Actin Waves Do Not Boost Neurite Outgrowth in the Early Stages of Neuron Maturation

Mortal S, Iseppon F, Perissinotto A, D'Este E, Cojoc D, Napolitano LMR, Torre V.

(2017) J Biol Methods;4(1):e65.

Combining FRET and optical tweezers to study RhoGTPases spatio-temporal dynamics upon local stimulation

Iseppon, F., Napolitano, LM., Torre, V., Cojoc, D. 

Sci. Rep. 6, art. no. 21629 (2016).

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.

BioTechniques 60 (1), 35-41 (2016).

A new approach to follow a single extracellular vesicle–cell interaction using optical tweezers

Prada I, Amin L, Furlan R, Legname G, Verderio C, Cojoc D.

Nanotechnology 27 (6), art. no. 065102 (2016).

Investigation into local cell mechanics by atomic force microscopy mapping and optical tweezer vertical indentation

Coceano G, Yousafzai MS, Ma W, Ndoye F, Venturelli L, Hussain I, Bonin S, Niemela J, Scoles G, Cojoc D, Ferrari E.

Front. Cell. Neurosci. 9:333 (2015).

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.

Microelectronic Engineering 2013, 107, 6-9;

Highly IR-transparent microfluidic chip with surface-modified BaF 2 optical windows for Infrared microspectroscopy of living cells.

E. Mitri, A. Pozzato, G. Coceano, D. Cojoc, L. Vaccari, M. Tormen, G. Grenci.

Int J Mol Sci. 2013 Apr 25;14(5):8963-84.

Cell signaling experiments driven by optical manipulation

Difato F, Pinato G, Cojoc D.

Scientific Reports 2012, 2, 675

Less than 5 Netrin-1 molecules initiate attraction but 200 Sema3A molecules are necessary for repulsion.

Giulietta Pinato, Dan Cojoc, Linh Thuy Lien, Alessio Ansuini, Jelena Ban, Elisa D’Este & Vincent Torre.

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.

Chapter Book (Ch. 6 pp. 183-213) in Synchrotron Radiation and Structural Proteomics, Eds. E. Pechkova and C. Riekel, Pan Stanford Publishing Pte. Ltd., Singapore, (2012), eBook ISBN: 9789814267939.

Optical Tweezers for Touchless Sample Manipulation in Synchrotron Radiation Experiments.

Silvia C. Santucci, Heinz Amenitsch, Dan Cojoc, and Christian Riekel

Chapter Book in Nanoscopy and Multidimensional Optical Fluorescence Microscopy; Editor: A. Diaspro, CRC Press, (2010).

Optical Tweezers Microscopy: applying and measuring piconewton forces in cell biology

F. Difato, E. Ferrari, R. Shahapure, V. Torre and D. Cojoc


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