Dan Cojoc | Consiglio Nazionale delle Ricerche (CNR) (original) (raw)

Papers by Dan Cojoc

Research paper thumbnail of Corrigendum: Cell Mechanotransduction With Piconewton Forces Applied by Optical Tweezers

Frontiers in Cellular Neuroscience

Research paper thumbnail of Novel Plasmonic Nanocavities for Optical Trapping‐Assisted Biosensing Applications

Advanced Optical Materials

However, due to the intrinsic low optical response of small objects, there has been a clear trade... more However, due to the intrinsic low optical response of small objects, there has been a clear trade-off between the size of a material and its response to light. [5] Recently, plasmonic nanostructures have emerged as leading platforms to enhance the weak optical signals of low dimensional materials including quantum dots (QDs), [6] small molecules, [7,8] and 2D monolayers. [9] The plasmonic enhancement of linear and nonlinear optical processes capitalizes on the near-and far-field properties of metallic (e.g., gold and silver) nanostructures. [10] One of the defining features of plasmonic nanostructures is their potential to confine light into deep subwavelength volumes, which has opened a new door to trap and manipulate dielectric, metallic, and biological nano-objects. [11] Moreover, metallic nanostructures are characterized by their capability to amplify the intensity of optical fields by orders of magnitude. The enhancement of local field intensity is attributed to the resonance of plasmon polaritons arising from the coupling of external electromagnetic fields to the collective oscillations of the conduction electrons. [12] A small perturbation (or change in the refractive index) of the near field zone of plasmonic nanostructures leads to significant shift in the plasmon polariton resonance wavelength, which has important implications for surface-enhanced sensing and spectroscopic applications. [13,14] Thus, for the ad-hoc enhancement of optical Plasmonic nanocavities have proved to confine electromagnetic fields into deep subwavelength volumes, implying their potentials for enhanced optical trapping and sensing of nanoparticles. In this review, the fundamentals and performances of various plasmonic nanocavity geometries are explored with specific emphasis on trapping and detection of small molecules and single nanoparticles. These applications capitalize on the local field intensity, which in turn depends on the size of plasmonic nanocavities. Indeed, properly designed structures provide significant local field intensity and deep trapping potential, leading to manipulation of nano-objects with low laser power. The relationship between optical trappinginduced resonance shift and potential energy of plasmonic nanocavity can be analytically expressed in terms of the intercavity field intensity. Within this framework, recent experimental works on trapping and sensing of single nanoparticles and small molecules with plasmonic nanotweezers are discussed. Furthermore, significant consideration is given to conjugation of optical tweezers with Raman spectroscopy, with the aim of developing innovative biosensors. These devices, which take the advantages of plasmonic nanocavities, will be capable of trapping and detecting nanoparticles at the single molecule level.

Research paper thumbnail of Copper Binding Regulates Cellular Prion Protein Function

Research paper thumbnail of Cell Mechanotransduction With Piconewton Forces Applied by Optical Tweezers

Frontiers in Cellular Neuroscience

Mechanical stresses are always present in the cellular environment and mechanotransduction occurs... more Mechanical stresses are always present in the cellular environment and mechanotransduction occurs in all cells. Although many experimental approaches have been developed to investigate mechanotransduction, the physical properties of the mechanical stimulus have yet to be accurately characterized. Here, we propose a mechanical stimulation method employing an oscillatory optical trap to apply piconewton forces perpendicularly to the cell membrane, for short instants. We show that this stimulation produces membrane indentation and induces cellular calcium transients in mouse neuroblastoma NG108-15 cells dependent of the stimulus strength and the number of force pulses.

Research paper thumbnail of ATP Modifies the Proteome of Extracellular Vesicles Released by Microglia and Influences Their Action on Astrocytes

Frontiers in pharmacology, 2017

Extracellular ATP is among molecules promoting microglia activation and inducing the release of e... more Extracellular ATP is among molecules promoting microglia activation and inducing the release of extracellular vesicles (EVs), which are potent mediators of intercellular communication between microglia and the microenvironment. We previously showed that EVs produced under ATP stimulation (ATP-EVs) propagate a robust inflammatory reaction among astrocytes and microglia in vitro and in mice with subclinical neuroinflammation (Verderio et al., 2012). However, the proteome of EVs released upon ATP stimulation has not yet been elucidated. In this study we applied a label free proteomic approach to characterize the proteome of EVs released constitutively and during microglia activation with ATP. We show that ATP drives sorting in EVs of a set of proteins implicated in cell adhesion/extracellular matrix organization, autophagy-lysosomal pathway and cellular metabolism, that may influence the response of recipient astrocytes to EVs. These data provide new clues to molecular mechanisms invol...

Research paper thumbnail of Glia-to-neuron transfer of miRNAs via extracellular vesicles: a new mechanism underlying inflammation-induced synaptic alterations

Acta neuropathologica, Jan 4, 2018

Recent evidence indicates synaptic dysfunction as an early mechanism affected in neuroinflammator... more Recent evidence indicates synaptic dysfunction as an early mechanism affected in neuroinflammatory diseases, such as multiple sclerosis, which are characterized by chronic microglia activation. However, the mode(s) of action of reactive microglia in causing synaptic defects are not fully understood. In this study, we show that inflammatory microglia produce extracellular vesicles (EVs) which are enriched in a set of miRNAs that regulate the expression of key synaptic proteins. Among them, miR-146a-5p, a microglia-specific miRNA not present in hippocampal neurons, controls the expression of presynaptic synaptotagmin1 (Syt1) and postsynaptic neuroligin1 (Nlg1), an adhesion protein which play a crucial role in dendritic spine formation and synaptic stability. Using a Renilla-based sensor, we provide formal proof that inflammatory EVs transfer their miR-146a-5p cargo to neuron. By western blot and immunofluorescence analysis we show that vesicular miR-146a-5p suppresses Syt1 and Nlg1 ex...

Research paper thumbnail of Investigating the effect of cell substrate on cancer cell stiffness by optical tweezers

Journal of Biomechanics

The mechanical properties of cells are influenced by their microenvironment. Here we report cell ... more The mechanical properties of cells are influenced by their microenvironment. Here we report cell stiffness alteration by changing the cell substrate stiffness for isolated cells and cells in contact with other cells. Polydimethylsiloxane (PDMS) is used to prepare soft substrates with three different stiffness values (173, 88 and 17kPa respectively). Breast cancer cells lines, namely HBL-100, MCF-7 and MDA-MB-231 with different level of aggressiveness are cultured on these substrates and their local elasticity is investigated by vertical indentation of the cell membrane. Our preliminary results show an unforeseen behavior of the MDA-MB-231 cells. When cultured on glass substrate as isolated cells, they are less stiff than the other two types of cells, in agreement with the general statement that more aggressive and metastatic cells are softer. However, when connected to other cells the stiffness of MDA-MB-231 cells becomes similar to the other two cell lines. Moreover, the stiffness of MDA-MB-231 cells cultured on soft PDMS substrates is significantly higher than the stiffness of the other cell types, demonstrating thus the strong influence of the environmental conditions on the mechanical properties of the cells.

Research paper thumbnail of Influences of amplitude distribution of illumination beam and lens aberrations on optical-computing accuracy

This paper tries to achieve two goals: studying the influence of certain parameters in Optical Co... more This paper tries to achieve two goals: studying the influence of certain parameters in Optical Computing, and then finding out the possibilities to improve the computation accuracy in Optical Information Processing Systems. A Computer Generated Complex Filter design, taking admissible error of Fourier Transform into account, has been demonstrated as an application of this study.

Research paper thumbnail of Characterization of prion protein function by focal neurite stimulation

Journal of Cell Science, 2016

The cellular prion protein (PrPC) is a ubiquitous glycoprotein, which is highly expressed in the ... more The cellular prion protein (PrPC) is a ubiquitous glycoprotein, which is highly expressed in the brain. This protein, mainly known for its role in neurodegenerative diseases, is involved in several physiological processes including neurite outgrowth. By using a novel focal stimulation technique, we explored the potential function of PrPC, in its soluble form, as a signaling molecule. Thus, soluble recombinant prion proteins (recPrP) encapsulated in micro-vesicles were released by photolysis near the hippocampal growth cones (GC). Local stimulation of wild-type GC with full-length recPrP induced neurite outgrowth and rapid GC turning towards the source. This effect is shown to be concentration dependent. Notably, PrPC knockout GC were insensitive to recPrP stimulation but this property was rescued in PrP knockout GC expressing GFP-PrP. Altogether, our findings indicate that recPrP functions as a signaling molecule and its homophilic interaction with membrane-anchored PrPC may promote...

Research paper thumbnail of Probing breast cancer mechanical properties at the sub-cellular level

Research paper thumbnail of Optical trapping and micromanipulation in microchannels with various configurations

Trapping and manipulation of microparticles using optical tweezers is usually performed within a ... more Trapping and manipulation of microparticles using optical tweezers is usually performed within a sample cell formed by two parallel microscope cover slides. In this paper we discuss and demonstrate trapping and manipulation conditions when the cell has more complex configurations like microchannels or capillary tubes. The microchannels are fabricated on the surface of the cover slide by means of lithographic

Research paper thumbnail of Optimization of computer-generated binary holograms using genetic algorithms

Proceedings of Spie the International Society For Optical Engineering, Nov 1, 1999

Research paper thumbnail of Double Optical Correlator by Spatial Filtering by Complementary Fourier Transforms

6Th Congress of the International Commission For Optics Optics As a Key to High Technology, Jul 1, 1993

Research paper thumbnail of Numerical analysis of forces in optical tweezers in the Rayleigh regime

In this work we present a numerical evaluation of the forces in an optical tweezers system, for m... more In this work we present a numerical evaluation of the forces in an optical tweezers system, for metallic nanoparticles in the Rayleigh regime. Initially a Gaussian beam is described in the scalar approximation, and the forces it can apply on Rayleigh dielectric and metallic particles are computed within the point-dipole approach. The method is then extended to dielectric and metallic

Research paper thumbnail of Optical Tweezers for Sample Fixing in Micro-Diffraction Experiments

AIP Conference Proceedings, 2007

In order to manipulate, characterize and measure the micro-diffraction of individual structural e... more In order to manipulate, characterize and measure the micro-diffraction of individual structural elements down to single phospholipid liposomes we have been using optical tweezers (OT) combined with an imaging microscope. We were able to install the OT system at the microfocus beamline ID13 at the ESRF and trap clusters of about 50 multi-lamellar liposomes (< 10 mum large cluster). Further

Research paper thumbnail of Measurement of the optical trapping force on micro-particles immersed in fluids

A strongly focused laser beam through an objective microscope with high NA allows the trapping of... more A strongly focused laser beam through an objective microscope with high NA allows the trapping of dielectric particles with micrometric sizes. The trapping force is proportional to the power of the laser, the relative refractive index (the ratio between the refractive index of the particle and the refractive index of the medium surrounding it) and the trapping geometry (shape of

Research paper thumbnail of Apparatus for determining the internal outline of a duct or cavity, and in particular for determining the internal impression of the auditory canal, a probe for this apparatus, and reflection device for an optical scanning apparatus

Research paper thumbnail of Effect of neighboring cells on cell stiffness measured by optical tweezers indentation

Journal of Biomedical Optics, 2016

We report on the modification of mechanical properties of breast cancer cells when they get in co... more We report on the modification of mechanical properties of breast cancer cells when they get in contact with other neighboring cells of the same type. Optical tweezers vertical indentation was employed to investigate cell mechanics in isolated and contact conditions, by setting up stiffness as a marker. Two human breast cancer cell lines with different aggressiveness [MCF-7 (luminal breast cancer) and MDA-MB-231 (basal-like breast cancer)] and one normal immortalized breast cell line HBL-100 (normal and myoepithelial) were selected. We found that neighboring cells significantly alter cell stiffness: MDA-MB-231 becomes stiffer when in contact, while HBL-100 and MCF-7 exhibit softer character. Cell stiffness was probed at three cellular subregions: central (above nucleus), intermediate (cytoplasm), and near the leading edge. In an isolated condition, all cells showed a significant regional variation in stiffness: higher at the center and fading toward the leading edge. However, the regional variation becomes statistically insignificant when the cells were in contact with other neighboring cells. The proposed approach will contribute to understand the intriguing temporal sequential alterations in cancer cells during interaction with their surrounding microenvironment.

Research paper thumbnail of Design and fabrication of new optics for X-ray microscopy and material science

J Phys Iv, 2003

The current intense interest in extrême ultraviolet and X-ray microscopy is mainly due to the ava... more The current intense interest in extrême ultraviolet and X-ray microscopy is mainly due to the availability of a nearly ideal optical source for diffractive optics (i.e. a source with low divergence whose wavelength can be tuned over a range of several keV and whose spectrum has a band pass Deltalambda/lambda of less than 10^{-4}). The aim of this paper is to introduce novel X-ray diffractive optics that, beside simple focusing, perform new optical functions. In particular, the intensity of the beam in the space after the optical elements can be redistributed with almost complete freedom. Using our own code we have designed high resolution diffractive elements which focus the monochromatic X-ray beam into multiple spots displaced in a single or more planes along the optical axis. These optical elements have been fabricated by means of e-beam lithography. Their functionality has been tested in two different X-ray microscopes: the scanning and the full-field imaging microscopes using the differential interference contrast method. We report experimental imaging results obtained with phase objects (PMMA and biological samples) and fluorescence measurements with important impact in the material science applications.

Research paper thumbnail of Manipulation of single and multiple low-index particles by means of optical tweezers

Optical Trapping and Optical Micromanipulation Ii, Jul 1, 2005

Higher-order laser beams were demonstrated to enable optical manipulation of low-index-particles.... more Higher-order laser beams were demonstrated to enable optical manipulation of low-index-particles. In this work single-ringed Laguerre-Gaussian beams, obtained by means of phase-only diffractive optical elements, are used to perform manipulation of phospholipid-shelled gas microbubbles in water. Implementation of diffractive optical elements on a programmable spatial light modulator allows to generate also arrays of Laguerre-Gaussian traps. We show manipulation of low-index

Research paper thumbnail of Corrigendum: Cell Mechanotransduction With Piconewton Forces Applied by Optical Tweezers

Frontiers in Cellular Neuroscience

Research paper thumbnail of Novel Plasmonic Nanocavities for Optical Trapping‐Assisted Biosensing Applications

Advanced Optical Materials

However, due to the intrinsic low optical response of small objects, there has been a clear trade... more However, due to the intrinsic low optical response of small objects, there has been a clear trade-off between the size of a material and its response to light. [5] Recently, plasmonic nanostructures have emerged as leading platforms to enhance the weak optical signals of low dimensional materials including quantum dots (QDs), [6] small molecules, [7,8] and 2D monolayers. [9] The plasmonic enhancement of linear and nonlinear optical processes capitalizes on the near-and far-field properties of metallic (e.g., gold and silver) nanostructures. [10] One of the defining features of plasmonic nanostructures is their potential to confine light into deep subwavelength volumes, which has opened a new door to trap and manipulate dielectric, metallic, and biological nano-objects. [11] Moreover, metallic nanostructures are characterized by their capability to amplify the intensity of optical fields by orders of magnitude. The enhancement of local field intensity is attributed to the resonance of plasmon polaritons arising from the coupling of external electromagnetic fields to the collective oscillations of the conduction electrons. [12] A small perturbation (or change in the refractive index) of the near field zone of plasmonic nanostructures leads to significant shift in the plasmon polariton resonance wavelength, which has important implications for surface-enhanced sensing and spectroscopic applications. [13,14] Thus, for the ad-hoc enhancement of optical Plasmonic nanocavities have proved to confine electromagnetic fields into deep subwavelength volumes, implying their potentials for enhanced optical trapping and sensing of nanoparticles. In this review, the fundamentals and performances of various plasmonic nanocavity geometries are explored with specific emphasis on trapping and detection of small molecules and single nanoparticles. These applications capitalize on the local field intensity, which in turn depends on the size of plasmonic nanocavities. Indeed, properly designed structures provide significant local field intensity and deep trapping potential, leading to manipulation of nano-objects with low laser power. The relationship between optical trappinginduced resonance shift and potential energy of plasmonic nanocavity can be analytically expressed in terms of the intercavity field intensity. Within this framework, recent experimental works on trapping and sensing of single nanoparticles and small molecules with plasmonic nanotweezers are discussed. Furthermore, significant consideration is given to conjugation of optical tweezers with Raman spectroscopy, with the aim of developing innovative biosensors. These devices, which take the advantages of plasmonic nanocavities, will be capable of trapping and detecting nanoparticles at the single molecule level.

Research paper thumbnail of Copper Binding Regulates Cellular Prion Protein Function

Research paper thumbnail of Cell Mechanotransduction With Piconewton Forces Applied by Optical Tweezers

Frontiers in Cellular Neuroscience

Mechanical stresses are always present in the cellular environment and mechanotransduction occurs... more Mechanical stresses are always present in the cellular environment and mechanotransduction occurs in all cells. Although many experimental approaches have been developed to investigate mechanotransduction, the physical properties of the mechanical stimulus have yet to be accurately characterized. Here, we propose a mechanical stimulation method employing an oscillatory optical trap to apply piconewton forces perpendicularly to the cell membrane, for short instants. We show that this stimulation produces membrane indentation and induces cellular calcium transients in mouse neuroblastoma NG108-15 cells dependent of the stimulus strength and the number of force pulses.

Research paper thumbnail of ATP Modifies the Proteome of Extracellular Vesicles Released by Microglia and Influences Their Action on Astrocytes

Frontiers in pharmacology, 2017

Extracellular ATP is among molecules promoting microglia activation and inducing the release of e... more Extracellular ATP is among molecules promoting microglia activation and inducing the release of extracellular vesicles (EVs), which are potent mediators of intercellular communication between microglia and the microenvironment. We previously showed that EVs produced under ATP stimulation (ATP-EVs) propagate a robust inflammatory reaction among astrocytes and microglia in vitro and in mice with subclinical neuroinflammation (Verderio et al., 2012). However, the proteome of EVs released upon ATP stimulation has not yet been elucidated. In this study we applied a label free proteomic approach to characterize the proteome of EVs released constitutively and during microglia activation with ATP. We show that ATP drives sorting in EVs of a set of proteins implicated in cell adhesion/extracellular matrix organization, autophagy-lysosomal pathway and cellular metabolism, that may influence the response of recipient astrocytes to EVs. These data provide new clues to molecular mechanisms invol...

Research paper thumbnail of Glia-to-neuron transfer of miRNAs via extracellular vesicles: a new mechanism underlying inflammation-induced synaptic alterations

Acta neuropathologica, Jan 4, 2018

Recent evidence indicates synaptic dysfunction as an early mechanism affected in neuroinflammator... more Recent evidence indicates synaptic dysfunction as an early mechanism affected in neuroinflammatory diseases, such as multiple sclerosis, which are characterized by chronic microglia activation. However, the mode(s) of action of reactive microglia in causing synaptic defects are not fully understood. In this study, we show that inflammatory microglia produce extracellular vesicles (EVs) which are enriched in a set of miRNAs that regulate the expression of key synaptic proteins. Among them, miR-146a-5p, a microglia-specific miRNA not present in hippocampal neurons, controls the expression of presynaptic synaptotagmin1 (Syt1) and postsynaptic neuroligin1 (Nlg1), an adhesion protein which play a crucial role in dendritic spine formation and synaptic stability. Using a Renilla-based sensor, we provide formal proof that inflammatory EVs transfer their miR-146a-5p cargo to neuron. By western blot and immunofluorescence analysis we show that vesicular miR-146a-5p suppresses Syt1 and Nlg1 ex...

Research paper thumbnail of Investigating the effect of cell substrate on cancer cell stiffness by optical tweezers

Journal of Biomechanics

The mechanical properties of cells are influenced by their microenvironment. Here we report cell ... more The mechanical properties of cells are influenced by their microenvironment. Here we report cell stiffness alteration by changing the cell substrate stiffness for isolated cells and cells in contact with other cells. Polydimethylsiloxane (PDMS) is used to prepare soft substrates with three different stiffness values (173, 88 and 17kPa respectively). Breast cancer cells lines, namely HBL-100, MCF-7 and MDA-MB-231 with different level of aggressiveness are cultured on these substrates and their local elasticity is investigated by vertical indentation of the cell membrane. Our preliminary results show an unforeseen behavior of the MDA-MB-231 cells. When cultured on glass substrate as isolated cells, they are less stiff than the other two types of cells, in agreement with the general statement that more aggressive and metastatic cells are softer. However, when connected to other cells the stiffness of MDA-MB-231 cells becomes similar to the other two cell lines. Moreover, the stiffness of MDA-MB-231 cells cultured on soft PDMS substrates is significantly higher than the stiffness of the other cell types, demonstrating thus the strong influence of the environmental conditions on the mechanical properties of the cells.

Research paper thumbnail of Influences of amplitude distribution of illumination beam and lens aberrations on optical-computing accuracy

This paper tries to achieve two goals: studying the influence of certain parameters in Optical Co... more This paper tries to achieve two goals: studying the influence of certain parameters in Optical Computing, and then finding out the possibilities to improve the computation accuracy in Optical Information Processing Systems. A Computer Generated Complex Filter design, taking admissible error of Fourier Transform into account, has been demonstrated as an application of this study.

Research paper thumbnail of Characterization of prion protein function by focal neurite stimulation

Journal of Cell Science, 2016

The cellular prion protein (PrPC) is a ubiquitous glycoprotein, which is highly expressed in the ... more The cellular prion protein (PrPC) is a ubiquitous glycoprotein, which is highly expressed in the brain. This protein, mainly known for its role in neurodegenerative diseases, is involved in several physiological processes including neurite outgrowth. By using a novel focal stimulation technique, we explored the potential function of PrPC, in its soluble form, as a signaling molecule. Thus, soluble recombinant prion proteins (recPrP) encapsulated in micro-vesicles were released by photolysis near the hippocampal growth cones (GC). Local stimulation of wild-type GC with full-length recPrP induced neurite outgrowth and rapid GC turning towards the source. This effect is shown to be concentration dependent. Notably, PrPC knockout GC were insensitive to recPrP stimulation but this property was rescued in PrP knockout GC expressing GFP-PrP. Altogether, our findings indicate that recPrP functions as a signaling molecule and its homophilic interaction with membrane-anchored PrPC may promote...

Research paper thumbnail of Probing breast cancer mechanical properties at the sub-cellular level

Research paper thumbnail of Optical trapping and micromanipulation in microchannels with various configurations

Trapping and manipulation of microparticles using optical tweezers is usually performed within a ... more Trapping and manipulation of microparticles using optical tweezers is usually performed within a sample cell formed by two parallel microscope cover slides. In this paper we discuss and demonstrate trapping and manipulation conditions when the cell has more complex configurations like microchannels or capillary tubes. The microchannels are fabricated on the surface of the cover slide by means of lithographic

Research paper thumbnail of Optimization of computer-generated binary holograms using genetic algorithms

Proceedings of Spie the International Society For Optical Engineering, Nov 1, 1999

Research paper thumbnail of Double Optical Correlator by Spatial Filtering by Complementary Fourier Transforms

6Th Congress of the International Commission For Optics Optics As a Key to High Technology, Jul 1, 1993

Research paper thumbnail of Numerical analysis of forces in optical tweezers in the Rayleigh regime

In this work we present a numerical evaluation of the forces in an optical tweezers system, for m... more In this work we present a numerical evaluation of the forces in an optical tweezers system, for metallic nanoparticles in the Rayleigh regime. Initially a Gaussian beam is described in the scalar approximation, and the forces it can apply on Rayleigh dielectric and metallic particles are computed within the point-dipole approach. The method is then extended to dielectric and metallic

Research paper thumbnail of Optical Tweezers for Sample Fixing in Micro-Diffraction Experiments

AIP Conference Proceedings, 2007

In order to manipulate, characterize and measure the micro-diffraction of individual structural e... more In order to manipulate, characterize and measure the micro-diffraction of individual structural elements down to single phospholipid liposomes we have been using optical tweezers (OT) combined with an imaging microscope. We were able to install the OT system at the microfocus beamline ID13 at the ESRF and trap clusters of about 50 multi-lamellar liposomes (< 10 mum large cluster). Further

Research paper thumbnail of Measurement of the optical trapping force on micro-particles immersed in fluids

A strongly focused laser beam through an objective microscope with high NA allows the trapping of... more A strongly focused laser beam through an objective microscope with high NA allows the trapping of dielectric particles with micrometric sizes. The trapping force is proportional to the power of the laser, the relative refractive index (the ratio between the refractive index of the particle and the refractive index of the medium surrounding it) and the trapping geometry (shape of

Research paper thumbnail of Apparatus for determining the internal outline of a duct or cavity, and in particular for determining the internal impression of the auditory canal, a probe for this apparatus, and reflection device for an optical scanning apparatus

Research paper thumbnail of Effect of neighboring cells on cell stiffness measured by optical tweezers indentation

Journal of Biomedical Optics, 2016

We report on the modification of mechanical properties of breast cancer cells when they get in co... more We report on the modification of mechanical properties of breast cancer cells when they get in contact with other neighboring cells of the same type. Optical tweezers vertical indentation was employed to investigate cell mechanics in isolated and contact conditions, by setting up stiffness as a marker. Two human breast cancer cell lines with different aggressiveness [MCF-7 (luminal breast cancer) and MDA-MB-231 (basal-like breast cancer)] and one normal immortalized breast cell line HBL-100 (normal and myoepithelial) were selected. We found that neighboring cells significantly alter cell stiffness: MDA-MB-231 becomes stiffer when in contact, while HBL-100 and MCF-7 exhibit softer character. Cell stiffness was probed at three cellular subregions: central (above nucleus), intermediate (cytoplasm), and near the leading edge. In an isolated condition, all cells showed a significant regional variation in stiffness: higher at the center and fading toward the leading edge. However, the regional variation becomes statistically insignificant when the cells were in contact with other neighboring cells. The proposed approach will contribute to understand the intriguing temporal sequential alterations in cancer cells during interaction with their surrounding microenvironment.

Research paper thumbnail of Design and fabrication of new optics for X-ray microscopy and material science

J Phys Iv, 2003

The current intense interest in extrême ultraviolet and X-ray microscopy is mainly due to the ava... more The current intense interest in extrême ultraviolet and X-ray microscopy is mainly due to the availability of a nearly ideal optical source for diffractive optics (i.e. a source with low divergence whose wavelength can be tuned over a range of several keV and whose spectrum has a band pass Deltalambda/lambda of less than 10^{-4}). The aim of this paper is to introduce novel X-ray diffractive optics that, beside simple focusing, perform new optical functions. In particular, the intensity of the beam in the space after the optical elements can be redistributed with almost complete freedom. Using our own code we have designed high resolution diffractive elements which focus the monochromatic X-ray beam into multiple spots displaced in a single or more planes along the optical axis. These optical elements have been fabricated by means of e-beam lithography. Their functionality has been tested in two different X-ray microscopes: the scanning and the full-field imaging microscopes using the differential interference contrast method. We report experimental imaging results obtained with phase objects (PMMA and biological samples) and fluorescence measurements with important impact in the material science applications.

Research paper thumbnail of Manipulation of single and multiple low-index particles by means of optical tweezers

Optical Trapping and Optical Micromanipulation Ii, Jul 1, 2005

Higher-order laser beams were demonstrated to enable optical manipulation of low-index-particles.... more Higher-order laser beams were demonstrated to enable optical manipulation of low-index-particles. In this work single-ringed Laguerre-Gaussian beams, obtained by means of phase-only diffractive optical elements, are used to perform manipulation of phospholipid-shelled gas microbubbles in water. Implementation of diffractive optical elements on a programmable spatial light modulator allows to generate also arrays of Laguerre-Gaussian traps. We show manipulation of low-index