Use of thermal gradients for control of vortex matter in mesoscopic superconductors.

Usually, the measurements of electronic and magnetic properties of superconducting samples are carried out under a constant temperature bath. On the other hand, thermal gradients induce local variation of the superconducting order parameter, and the vortex dynamics can present interesting behaviors. In this work, we solved the time-dependent Ginzburg-Landau equations simulating samples under two different thermal gradients, and considering two values of the Ginzburg-Landau parameter, [Formula: see text]. We find that both parameters, i.e. [Formula: see text] and thermal gradients, play an important role on the vortex dynamics and on the magnetization behavior of the samples.

Dynamics and heat diffusion of Abrikosov's vortex-antivortex pairs during an annihilation process.

The manipulation and control of vortex states in superconducting systems are of great interest in view of possible applications, for which mesoscopic materials are good candidates. In this work, we studied the annihilation dynamics and the dissipative aspects of an Abrikosov's vortex-antivortex pair in a mesoscopic superconducting system with a concentric hole. The generalized time-dependent Ginzburg-Landau equations were numerically solved. The main result is the appearance of a phase slip-like line due to the elongation of the vortex and antivortex cores. Under specific circumstances, thermal dissipation might be associated with a sizeable relaxation of the order parameter, so that the energy released in the annihilation of a vortex-antivortex pair might become detectable in measurements of the magnetization as a function of time.

Functionalized luminescent nanocrystals on patterned surfaces obtained by radio frequency glow discharges.

In this work a genuine combination of a bottom-up approach, which is based on synthesis and functionalization of emitting nanocrystals (NCs), with a top-down strategy, which relies on a flexible and versatile cold plasma process, is shown. Luminescent semiconducting colloidal NCs consisting of a CdSe core coated with a ZnS shell (CdSe@ZnS) are directly assembled onto micro-patterned substrates previously functionalized by means of glow discharges performed through physical masks. The NC assembly is driven by electrostatic interactions that led to their successful organization into spatially resolved domains. Two distinct protocols are tested, the former using a plasma deposition process combined with an electrostatic layer-by-layer procedure, the latter based on a two-step plasma deposition/treatment process. The procedures are thoroughly monitored with fluorescence microscopy, atomic force microscopy, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy and scanning electron microscopy. The two-step plasma protocol is demonstrated to be more efficient in directing a uniform and specific assembly of luminescent NCs with respect to the hybrid procedure. The presented 'mix and match' approach offers great potential for integrating NCs, with their unique size-dependent properties, into microstructures, providing a universal platform for the fabrication of sensors, biochips, displays and switches.

Covalent immobilization of liposomes on plasma functionalized metallic surfaces.

A method was developed to functionalize biomedical metals with liposomes. The novelty of the method includes the plasma-functionalization of the metal surface with proper chemical groups to be used as anchor sites for the covalent immobilization of the liposomes. Stainless steel (SS-316) disks were processed in radiofrequency glow discharges fed with vapors of acrylic acid to coat them with thin adherent films characterized by surface carboxylic groups, where liposomes were covalently bound through the formation of amide bonds. For this, liposomes decorated with polyethylene glycol molecules bearing terminal amine-groups were prepared. After ensuring that the liposomes remain intact, under the conditions applying for immobilization; different attachment conditions were evaluated (incubation time, concentration of liposome dispersion) for optimization of the technique. Immobilization of calcein-entrapping liposomes was evaluated by monitoring the percent of calcein attached on the surfaces. Best results were obtained when liposome dispersions with 5mg/ml (liposomal lipid) concentration were incubated on each disk for 24h at 37°C. The method is proposed for developing drug-eluting biomedical materials or devices by using liposomes that have appropriate membrane compositions and are loaded with drugs or other bioactive agents.

Biomineralized porous composite scaffolds prepared by chemical synthesis for bone tissue regeneration.

Scaffold design is a key factor in the clinical success of bone tissue engineering grafts. To date, no existing single biomaterial used in bone repair and regeneration fulfils all the requirements for an ideal bone graft. In this study hydroxyapatite/polycaprolactone (HA/PCL) composite scaffolds were prepared by a wet chemical method at room temperature. The physico-chemical properties of the composite materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, while scaffold morphology was investigated by scanning electron microscopy (SEM) with energy-dispersive spectroscopy to validate the process used for synthesis. Finally, the response of bone marrow-derived human mesenchymal stem cells (hMSCs) in terms of cell proliferation and differentiation to the osteoblastic phenotype was evaluated using the Alamar blue assay, SEM and alkaline phosphatase activity. Microstructural analysis indicated that the HA particles were distributed homogeneously within the PCL matrix. The biological results revealed that the HA/PCL composite scaffolds are suitable for the proliferation and differentiation of MSCs in vitro, supporting osteogenesis after 15 days. All the results indicate that these scaffolds meet the requirements of materials for bone tissue engineering and could be used for many clinical applications in orthopaedic and maxillofacial surgery.

Behaviour of SH-SY5Y neuroblastoma cell line grown in different media and on different chemically modified substrates.

Among the parameters that can be tested in experiments on neuronal cell culture the use of different culture media and substrates represents a powerful assay to influence cell adhesion and differentiation. In this work, plasma-enhanced-chemical vapour depositions (PE-CVD) from acrylic acid and allylamine vapours have been performed to deposit coatings bearing oxygen (O)- and nitrogen (N)-containing functional groups on polyethylenetherephtalate (PET) surface. Human neuroblastoma SH-SY5Y cells were grown on plasma modified substrates and in presence of media containing different amount of fetal calf serum (FCS) or in serum-free medium containing cAMP. Our results showed that N-containing substrates improved cell adhesion, while the neurites sprouting was influenced by cell culture media. Interestingly, the presence of carboxylic groups on the modified surface can influence the expression of a differentiation marker, neurofilament-200 (NF-H), in cells grown in serum-containing media.