Maria Massa - Academia.edu (original) (raw)

Papers by Maria Massa

Journal of Endocrinology, 2001

We correlated the changes in glucose-induced insulin secretion with those observed in glucose met... more We correlated the changes in glucose-induced insulin secretion with those observed in glucose metabolism and hexokinase/glucokinase activity in islets from normal sucrose-fed hamsters. Blood glucose and insulin levels were measured in normal male hamsters fed with (S5) or without (C5) 10% sucrose in the drinking water for 5 weeks. Isolated islets (collagenase digestion) from both groups of animals were used to study insulin secretion, (14)CO(2) and (3)H(2)O production from D-[U-(14)C]-glucose and D-[5-(3)H]-glucose respectively, with 3.3 or 16.7 mM glucose in the medium, and hexokinase/glucokinase activity (fluorometric assay) in islet homogenates. Whereas S5 and C5 animals had comparable normal blood glucose levels, S5 showed higher insulin levels than C5 hamsters (2.3+/-0.1 vs 0.6+/-0.03 ng/ml, P<0.001). Islets from S5 hamsters released significantly more insulin than C5 islets in the presence of low and high glucose (3.3 mM glucose: 0.77+/-0.04 vs 0.20+/-0.06 pg/ng DNA/min, P&...

ABSTRACT In order to perform in a more sophisticated manner, structural and dynamics studies of f... more ABSTRACT In order to perform in a more sophisticated manner, structural and dynamics studies of free clusters and molecules, a new experimental method was developed, based on the well known crossed-beam scattering technique combined with modern imaging technologies. This novel method facilitates measurements of differential collision cross-sections and double differential cross-sections and therefore gives valuable information on the dynamics of the colliding species and their structure. The investigation of simple collision systems (Ta+-Ne, N2, CO, C2H2) with this method were performed in the non-adiabatic regime (impulsive collisions) which is a not yet extensively explored region and where the colliding species can be treated as hard bodies. The measurements of the angular dependence of the differential crosssection reveal that the potential energy, which governs the ion-atom interaction, in the specific energy regime, exhibits a Coulombic repulsive behavior of the empirical Universal form. Moreover, the energy loss spectra recorded in ion-molecule collisions, indicate that energy is transferred both in rotational and vibrational degrees of freedom of the molecules. The simple hard-potential model was employed in the theoretical analysis of this inelastic process. By means of this model, we determined the equipotential surface, which characterize the interaction of the colliding species and subsequently the structure of the molecule in the specific collision energy. This novel experimental technique in conjunction with simple theoretical models is a promising new tool for static (structure) and dynamics (fragmentation, energy transfer, reactivity, etc.) studies of gas-phase molecules and clusters.

PubMed, 2016

In this article novel approaches for the improvement of the recorded signal coupled with the feas... more In this article novel approaches for the improvement of the recorded signal coupled with the feasibility of multiple analyte detection, irrespective of the biosensor platform are being presented. The techniques that have been developed address commonly encountered issues that have traditionally hindered the commercialization of biosensors, such as cost, reproducibility and sensitivity and most importantly multianalyte detection. The fluorescence-based detection of copper is being described as an example of the use of Laser Induced Forward Transfer technique (LIFT) for the immobilization of biomolecules with high spatial resolution, in addition to a technique that involves the displacement of a short complementary strand to the immobilized probe molecule for the quantification of analyte binding and the enhancement of the recorded signal.

Journal of Physical Chemistry A, Jul 15, 2005

By use of photodissociation spectroscopy of mass-selected ions, vibrationally resolved electronic... more By use of photodissociation spectroscopy of mass-selected ions, vibrationally resolved electronic spectra of the Sr+ CO2 complex are recorded in two energy regions, 20,780-22,990 and 16,210-17,550 cm(-1), correlating to the Sr+ 5(2)P &amp;amp;amp;amp;amp;amp;amp;lt;-- 5(2)S and 4(2)D &amp;amp;amp;amp;amp;amp;amp;lt;-- 5(2)S transitions, respectively. The spectra are analyzed to obtain the vibrational constants and dissociation energies of the molecular states. The observed spin-orbit splitting indicates a linear complex in agreement with theoretical calculations. The results are compared with similar systems and explained in the framework of electrostatic interactions.

Proceedings of SPIE, Mar 15, 2013

ABSTRACT We review recent advances on the emission of tailored intense THz pulses from 2-color fe... more ABSTRACT We review recent advances on the emission of tailored intense THz pulses from 2-color femtosecond laser filaments in gases. Extended tunability of the THz pulses is achieved via filamentation molding and the use of cleverly engineered metamaterials.

Physical Review A, Mar 21, 2014

We propose a comprehensive physical model explaining the conical character of broadband terahertz... more We propose a comprehensive physical model explaining the conical character of broadband terahertz generation from femtosecond two-color laser-induced air plasma filaments. We show, that, in contrast to other models, emission is always conical, resulting from phase matching of the radiation produced inside the filament combined with a partial back reflection of the generated terahertz field from the filament itself due to the frequency-dependent critical plasma density. The obtained conical angle varies from 2 • to 10 • , depending on the plasma density distribution and filament length. Unlike previously proposed models, our model shows good agreement with our experiments as well as a wide range of experimental findings from the literature.

Optics Express, Aug 19, 2010

We demonstrate the possibility to rotate the polarization of linearly polarized THz pulses via th... more We demonstrate the possibility to rotate the polarization of linearly polarized THz pulses via the accurate control of the 2-color filament surrounding gas pressure. We also show ways to produce elliptically and circularly polarized THz pulses.

Electrochemistry Communications, Mar 1, 2016

Abstract The development of an amperometric biosensor for herbicide detection, using bacterial re... more Abstract The development of an amperometric biosensor for herbicide detection, using bacterial reaction centers (RC) as biorecognition element, is presented. RC immobilization on gold screen printed electrodes was achieved by LIFT, a powerful physisorption-based immobilization technique that enhances the intimate contact between the protein and the electrode surface. As a result, stable photocurrents driven by direct electron transfer at the donor side were observed, both in the presence and in the absence of a quinone substrate in solution. The addition of quinone UQ0 increased the photocurrents, while the UQ0-free system showed higher sensitivity to the herbicide terbutryn, a model inhibitor, acting as photocurrent attenuator. In spite of its simple design, the performances achieved by our mediatorless device are comparable or superior to those reported for analogous RC-based photoelectrochemical cells, in terms of both terbutryn sensing and photocurrent generation.

Langmuir, Jan 17, 2017

In this paper we present the immobilization of thiol-modified aptamers on alkyne-or alkenetermina... more In this paper we present the immobilization of thiol-modified aptamers on alkyne-or alkeneterminated silicon nitride surfaces, by laser-induced click chemistry reactions. The aptamers are printed onto the surface by Laser Induced Forward Transfer (LIFT), which also induces the covalent bonding of the aptamers by thiol-ene or thiol-yne reactions that occur upon UV irradiation of the thiol-modified aptamers with ns laser pulses. This combination of LIFT and laser-induced click chemistry allows the creation of high-resolution patterns without the need of masks. While the click chemistry already takes place during the printing process (single-step process) by the laser pulse used for the printing process, further irradiation of the LIFT-printed aptamers by laser pulses (two-step process), leads to a further increase of the immobilization efficiency.

Optics Letters, Jul 12, 2010

We investigate the emission of terahertz (THz) radiation from two laser filaments in air. An incr... more We investigate the emission of terahertz (THz) radiation from two laser filaments in air. An increase by 1 order of magnitude of the overall THz power is found when the two filaments are coherently linked on-axis, leading to a single longer concatenated filament. The observed enhancement is found to be the same for the cases of single-color and two-color filamentation approaches.

Applied Spectroscopy, Nov 1, 2013

Terahertz time-domain spectroscopy (THz-TDS) has been applied for the detection and discriminatio... more Terahertz time-domain spectroscopy (THz-TDS) has been applied for the detection and discrimination of harmful chemical residues in honey. Three antibiotics (sulfapyridine, sulfathiazole, and tetracycline) and two acaricides (coumaphos and amitraz) were characterized in the THz frequency regime between 0.5 THz and 6.0 THz. All chemical substances present distinct absorption peaks. THz transmission measurements of honey mixtures with antibiotics have been performed, revealing that antibiotic residues are traceable in highly absorptive food products, such as honey, at concentrations down to 1% weight percentage, thanks to their THz fingerprints. Moreover, multiple antibiotics were identified in their mixture with honey, pointing out the potential of the technique to be used in the near future as a fast, real-time technique for detecting and discriminating multi-residues strictly related to food safety issues.

Photonic integrated circuits (PICs) are one of the key enablers for beyond 5G networks. A novel g... more Photonic integrated circuits (PICs) are one of the key enablers for beyond 5G networks. A novel generation of fully integrated photonic-enabled transceivers operating seamlessly in W-D-and THz-bands is developed within the EU funded project TERAWAY. Photonic integration technology enables key photonic functionalities on a single PIC including photonic up/down conversion. For efficient down-conversion at the photonic integrated receiver, we develop the first waveguide-fed photoconductive antenna for THz communications. Finally, we report on the experimental implementation of a fully photonic-enabled link operating across W-D-and THz-bands.

Gas-plasma strings from 2-color femtosecond laser filaments constitute one of the most convenient... more Gas-plasma strings from 2-color femtosecond laser filaments constitute one of the most convenient and promising sources of pulsed terahertz (THz) radiation. It is one of the approaches that allow one to achieve at the same time ultrabroadband THz spectra and very high amplitudes of THz electric fields. Such sources present major advantages for applications of sensing, spectroscopy, imaging, and nonlinear optics. In view of the numerous applications an understanding of the spatial distribution of the terahertz radiation, from this source, is crucial. One of the first works towards this direction [1], revealed a highly directional THz radiation while a more recent publication [2] proposes a donut-shape spatial pattern. The most recent results reported by Kim et.al. [3], propose an off-axis phase matched emission from the filament due to interference effect between the different point sources across the filament, resulting thus in a donut-shape profile. A simple theoretical model was also proposed in [3], which is though insufficient to explain all observations.

Journal of Sensors, Feb 17, 2019

Immunosensor sensitivity and stability depend on a number of parameters such as the orientation, ... more Immunosensor sensitivity and stability depend on a number of parameters such as the orientation, the surface density, and the antigen-binding efficiency of antibodies following their immobilization onto functionalized surfaces. A number of techniques have been developed to improve the performance of an immunosensor that targets one or both of the parameters mentioned above. Herein, two widely employed techniques are compared for the first time, which do not require any complex engineering of neither the antibodies nor the surfaces onto which the former get immobilized. To optimize the different surface functionalization protocols and compare their efficiency, a model antibody-antigen system was employed that resembles the complex matrices immunosensors are frequently faced with in real conditions. The obtained results reveal that protein A/G is much more efficient in increasing antibody loading onto the surfaces in comparison to boronate ester chemistry. Despite the fact, therefore, that both contribute towards the orientation-specific immobilization of antibodies and hence enhance their antigen-binding efficiency, it is the increased antibody surface density attained with the use of protein A/G that plays a critical role in achieving maximal antigen recognition.