Abstract In the last decade, hyaluronan (HA, polyanion) and chitosan (CHI, polycation) biopolymer... more Abstract In the last decade, hyaluronan (HA, polyanion) and chitosan (CHI, polycation) biopolymers have been assembled by layer-by-layer (LbL) for the synthesis of antibacterial coatings. As electrostatic interactions are the main driving force for the formation of LbL films, pH and ionic strength (IS) are important critical variables of synthesis. In this context, we used surface fractal analysis of HA/CHI films to characterize the growth process for different bilayers obtained with two pH (5 and 3) and IS values (0 and 0.1 M NaCl). Our results showed that the HA/CHI assembling is mainly affected by changes in the pH than IS. Fractal dimension (Df) of pH 5 series presented values ~2.2, indicating that irregularities from the initial random adsorption process are minimized. However, when pH decreased to 3, Df increases up to ~2.5, suggesting a transition to diffusion-limited aggregation.
2019 International Conference on Manipulation, Automation and Robotics at Small Scales (MARSS), 2019
The shape memory alloys (SMAs) have recently been recognized as reliable basement of the technolo... more The shape memory alloys (SMAs) have recently been recognized as reliable basement of the technology of mechanical nanotools with still non determined minimal size. Among them the intermetallic alloy Ti(NiCu) give promising possibilities to create the reconfigurable micro- and nanostructures with shape memory effect (SME) capable to produce mechanical work on nanoscale. In the present report the review of the basic physical phenomena, which provide the possibility for the application of nanostructured SMA Ti(NiCu) for creating of micro and nanotools is given. The preliminary strained layered composites of SMAs are discussed which provide the multiple reversible actuation of a SMA based tool. Fundamental studies devoted to search for minimal size, at which martensitic phase transition and controllable actuation of SMA based tools take place are described. The technology of SMAs treatment by FIB-CVD gives the possibility to create different kinds of micro and nanotools, like nano- twee...
Microorganism pathogenicity strongly relies on the generation of multicellular assemblies, called... more Microorganism pathogenicity strongly relies on the generation of multicellular assemblies, called biofilms. Understanding their organization can unveil vulnerabilities leading to potential treatments; spatially and temporally-resolved comprehensive experimental characterization can provide new details of biofilm formation, and possibly new targets for disease control. Here, biofilm formation of economically important phytopathogen Xylella fastidiosa was analyzed at single-cell resolution using nanometer-resolution spectro-microscopy techniques, addressing the role of different types of extracellular polymeric substances (EPS) at each stage of the entire bacterial life cycle. Single cell adhesion is caused by unspecific electrostatic interactions through proteins at the cell polar region, where EPS accumulation is required for more firmly-attached, irreversibly adhered cells. Subsequently, bacteria form clusters, which are embedded in secreted loosely-bound EPS, and bridged by up to ...
ABSTRACTWe have recently shown that spatial ordering for epitaxially grown InP dots can be obtain... more ABSTRACTWe have recently shown that spatial ordering for epitaxially grown InP dots can be obtained using the periodic stress field of compositional modulation on the InGaP buffer layer. The aim of this present work is to study the growth of films of GaP by Chemical Beam Epitaxy (CBE), with in-situ monitoring by Reflection High Energy Electron Diffraction (RHEED), on layers of unstressed and stressed GaAs. Complementary, we have studied the role of a buried InP dot array on GaP nucleation in order to obtain three-dimensional structures. In both cases, the topographical characteristics of the samples were investigated by Atomic Force Microscopy (AFM) in non-contact mode. Thus vertically-coupled quantum dots of different materials have been obtained keeping the in-place spatial ordering originated from the composition modulation.
We performed a detailed investigation of the structural and optical properties of multi-layers of... more We performed a detailed investigation of the structural and optical properties of multi-layers of InP/GaAs quantum dots, which present a type II interface arrangement. Transmission electronic microscopy analysis has revealed relatively large dots that coalesce forming so-called quantum posts when the GaAs layer between the InP layers is thin. We observed that the structural properties and morphology affect the resulting radiative lifetime of the carriers in our systems. The carrier lifetimes are relatively long, as expected for type II systems, as compared to those observed for single layer InP/GaAs quantum dots. The interface intermixing effect has been pointed out as a limiting factor for obtaining an effective spatial separation of electrons and holes in the case of single layer InP/GaAs quantum-dot samples. In the present case this effect seems to be less critical due to the particular carrier wavefunction distribution along the structures.
Journal of controlled release : official journal of the Controlled Release Society, Jan 30, 2012
The low efficiency of gene transfer is a recurrent problem in DNA vaccine development and gene th... more The low efficiency of gene transfer is a recurrent problem in DNA vaccine development and gene therapy studies using non-viral vectors such as plasmid DNA (pDNA). This is mainly due to the fact that during their traffic to the target cell's nuclei, plasmid vectors must overcome a series of physical, enzymatic and diffusional barriers. The main objective of this work is the development of recombinant proteins specifically designed for pDNA delivery, which take advantage of molecular motors like dynein, for the transport of cargos from the periphery to the centrosome of mammalian cells. A DNA binding sequence was fused to the N-terminus of the recombinant human dynein light chain LC8. Expression studies indicated that the fusion protein was correctly expressed in soluble form using E. coli BL21(DE3) strain. As expected, gel permeation assays found the purified protein mainly present as dimers, the functional oligomeric state of LC8. Gel retardation assays and atomic force microsc...
Abstract In the last decade, hyaluronan (HA, polyanion) and chitosan (CHI, polycation) biopolymer... more Abstract In the last decade, hyaluronan (HA, polyanion) and chitosan (CHI, polycation) biopolymers have been assembled by layer-by-layer (LbL) for the synthesis of antibacterial coatings. As electrostatic interactions are the main driving force for the formation of LbL films, pH and ionic strength (IS) are important critical variables of synthesis. In this context, we used surface fractal analysis of HA/CHI films to characterize the growth process for different bilayers obtained with two pH (5 and 3) and IS values (0 and 0.1 M NaCl). Our results showed that the HA/CHI assembling is mainly affected by changes in the pH than IS. Fractal dimension (Df) of pH 5 series presented values ~2.2, indicating that irregularities from the initial random adsorption process are minimized. However, when pH decreased to 3, Df increases up to ~2.5, suggesting a transition to diffusion-limited aggregation.
2019 International Conference on Manipulation, Automation and Robotics at Small Scales (MARSS), 2019
The shape memory alloys (SMAs) have recently been recognized as reliable basement of the technolo... more The shape memory alloys (SMAs) have recently been recognized as reliable basement of the technology of mechanical nanotools with still non determined minimal size. Among them the intermetallic alloy Ti(NiCu) give promising possibilities to create the reconfigurable micro- and nanostructures with shape memory effect (SME) capable to produce mechanical work on nanoscale. In the present report the review of the basic physical phenomena, which provide the possibility for the application of nanostructured SMA Ti(NiCu) for creating of micro and nanotools is given. The preliminary strained layered composites of SMAs are discussed which provide the multiple reversible actuation of a SMA based tool. Fundamental studies devoted to search for minimal size, at which martensitic phase transition and controllable actuation of SMA based tools take place are described. The technology of SMAs treatment by FIB-CVD gives the possibility to create different kinds of micro and nanotools, like nano- twee...
Microorganism pathogenicity strongly relies on the generation of multicellular assemblies, called... more Microorganism pathogenicity strongly relies on the generation of multicellular assemblies, called biofilms. Understanding their organization can unveil vulnerabilities leading to potential treatments; spatially and temporally-resolved comprehensive experimental characterization can provide new details of biofilm formation, and possibly new targets for disease control. Here, biofilm formation of economically important phytopathogen Xylella fastidiosa was analyzed at single-cell resolution using nanometer-resolution spectro-microscopy techniques, addressing the role of different types of extracellular polymeric substances (EPS) at each stage of the entire bacterial life cycle. Single cell adhesion is caused by unspecific electrostatic interactions through proteins at the cell polar region, where EPS accumulation is required for more firmly-attached, irreversibly adhered cells. Subsequently, bacteria form clusters, which are embedded in secreted loosely-bound EPS, and bridged by up to ...
ABSTRACTWe have recently shown that spatial ordering for epitaxially grown InP dots can be obtain... more ABSTRACTWe have recently shown that spatial ordering for epitaxially grown InP dots can be obtained using the periodic stress field of compositional modulation on the InGaP buffer layer. The aim of this present work is to study the growth of films of GaP by Chemical Beam Epitaxy (CBE), with in-situ monitoring by Reflection High Energy Electron Diffraction (RHEED), on layers of unstressed and stressed GaAs. Complementary, we have studied the role of a buried InP dot array on GaP nucleation in order to obtain three-dimensional structures. In both cases, the topographical characteristics of the samples were investigated by Atomic Force Microscopy (AFM) in non-contact mode. Thus vertically-coupled quantum dots of different materials have been obtained keeping the in-place spatial ordering originated from the composition modulation.
We performed a detailed investigation of the structural and optical properties of multi-layers of... more We performed a detailed investigation of the structural and optical properties of multi-layers of InP/GaAs quantum dots, which present a type II interface arrangement. Transmission electronic microscopy analysis has revealed relatively large dots that coalesce forming so-called quantum posts when the GaAs layer between the InP layers is thin. We observed that the structural properties and morphology affect the resulting radiative lifetime of the carriers in our systems. The carrier lifetimes are relatively long, as expected for type II systems, as compared to those observed for single layer InP/GaAs quantum dots. The interface intermixing effect has been pointed out as a limiting factor for obtaining an effective spatial separation of electrons and holes in the case of single layer InP/GaAs quantum-dot samples. In the present case this effect seems to be less critical due to the particular carrier wavefunction distribution along the structures.
Journal of controlled release : official journal of the Controlled Release Society, Jan 30, 2012
The low efficiency of gene transfer is a recurrent problem in DNA vaccine development and gene th... more The low efficiency of gene transfer is a recurrent problem in DNA vaccine development and gene therapy studies using non-viral vectors such as plasmid DNA (pDNA). This is mainly due to the fact that during their traffic to the target cell's nuclei, plasmid vectors must overcome a series of physical, enzymatic and diffusional barriers. The main objective of this work is the development of recombinant proteins specifically designed for pDNA delivery, which take advantage of molecular motors like dynein, for the transport of cargos from the periphery to the centrosome of mammalian cells. A DNA binding sequence was fused to the N-terminus of the recombinant human dynein light chain LC8. Expression studies indicated that the fusion protein was correctly expressed in soluble form using E. coli BL21(DE3) strain. As expected, gel permeation assays found the purified protein mainly present as dimers, the functional oligomeric state of LC8. Gel retardation assays and atomic force microsc...
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Papers by Monica Cotta