374 research outputs found
Selective Biochemical Manipulation of Twin Neuronal Networks on Microelectrode Arrays
No full textComparability of responses to neuroactive compounds and spatially and temporally resolved delivery of soluble factors are two major key features for pharmacological assays. Here, we describe the fabrication and the use of a device for long-term growth of twin neuronal networks and for their controlled biochemicalstimulation. The device is formed by a PDMS microfl uidic chamber coupled to a fl at Microelectrode Array (MEA), which provides the electrophysiological readout of the pharmacological stimulation. A partial physical barrier divides the chamber in two sub-compartments, where two functionally independent but fl uidically connected neuronal networks can be grown. This platform improves biological comparability between cultures and allows to perform selective and temporally controlled stimulations to neurons, running parallel pharmacological tests on the same device
MODELLING ELECTRONIC AND STRUCTURAL PROPERTIES OF QUANTUM CONFINED METAL-HALIDE PEROVSKITES
No full textThis thesis focusses on the exploration of various theoretical methods to address the interesting questions concerning electronic and optical properties of quantum-confined systems. Chapter 1 serves the purpose of providing a sufficient background for the reader on state-of-the-art knowledge and approaches in order to understand the motivations behind the study of each system: 2D layered halide perovskites (Chapter 2), lead-halide perovskite nanocrystals (Chapter 3) and metal-insulator-metal optical nanocavities (Chapter 4).
In Chapter 4 the fundamentals of quantum mechanics are used to interpret the resonances of optical cavities as Epsilon-near-zero modes (ENZ), allowing us to describe them using the simple formalism of the particle in a box. In the various subparagraphs we use this approach to understand the polarization and coupling behaviours of such modes, eventually designing ENZ crystals.
In Chapter 3 an analytical model is built to calculate completely ab initio the excitonic energies and the exciton binding energies of perovskite nanocrystals. This is accomplished using the state-of-the-art GW correction to the calculations of molecular orbitals energies and the Bethe-Salpeter equation for a precise evaluation of the excited states in real space. This method allows to study the effect of every physical quantity entering the description (e.g. the dielectric environment, exchange and Coulomb interactions...) on the final result, providing useful insight in the physics underlying the optical properties of these nanocrystals.
In Chapter 2, Density Functional Theory is exploited to evaluate the effects of different ligands on the structural and the electronic properties of 2D halide perovskites. In the subparagraphs, various aspects are studied, for example the effects of different binding groups on the band structure, of different ligands on the Raman response and on the phase transition temperatures
A low-noise, modular, and versatile analog front-end intended for processing in vitro neuronal signals detected by microelectrode arrays
No full textThe collection of good quality extracellular neuronal spikes from neuronal cultures coupled to Microelectrode Arrays (MEAs) is
a binding requirement to gather reliable data. Due to physical constraints, low power requirement, or the need of customizability,
commercial recording platforms are not fully adequate for the development of experimental setups integrating MEA technology
with other equipment needed to perform experiments under clima
te controlled conditions, like environmental chambers or cell
culture incubators. To address this issue, we developed a custom MEA interfacing system featuring low noise, low power, and
the capability to be readily integrated inside an incubator-like environment. Two stages, a preamplifier and a filter amplifier, were
designed, implemented on printed circuit boards, and tested. The system is characterized by a low input-referred noise (
<
1
휇
V
RMS), a high channel separation (
>
70 dB), and signal-to-noise ratio values of neuronal recordings comparable to those obtained
with the benchmark commercial MEA system. In addition, the system was successfully integrated with an environmental MEA
chamber, without harming cell cultures during experiments and without being damaged by the high humidity level. The devised
system is of practical value in the development of
in vitro
platforms to study temporally extended neuronal network dynamics by
means of MEAs
The Influence of Neuronal Density and Maturation on Network Activity of Hippocampal Cell Cultures: A Methodological Study
No full textIt is known that cell density influences the maturation process of in vitro neuronal networks. Neuronal cultures plated with different cell densities differ in number of synapses per neuron and thus in single neuron synaptic transmission, which results in a density-dependent neuronal network activity. Although many authors provided detailed information about the effects of cell density on neuronal culture activity, a dedicated report of density and age influence on neuronal hippocampal culture activity has not yet been reported. Therefore, this work aims at providing reference data to researchers that set up an experimental study on hippocampal neuronal cultures, helping in planning and decoding the experiments. In this work, we analysed the effects of both neuronal density and culture age on functional attributes of maturing hippocampal cultures. We characterized the electrophysiological activity of neuronal cultures seeded at three different cell densities, recording their spontaneous electrical activity over maturation by means of MicroElectrode Arrays (MEAs). We had gather data from 86 independent hippocampal cultures to achieve solid statistic results, considering the high culture-to-culture variability. Network activity was evaluated in terms of simple spiking, burst and network burst features. We observed that electrical descriptors were characterized by a functional peak during maturation, followed by a stable phase (for sparse and medium density cultures) or by a decrease phase (for high dense neuronal cultures). Moreover, 900 cells/mm(2) cultures showed characteristics suitable for long lasting experiments (e.g. chronic effect of drug treatments) while 1800 cells/mm(2) cultures should be preferred for experiments that require intense electrical activity (e.g. to evaluate the effect of inhibitory molecules). Finally, cell cultures at 3600 cells/mm(2) are more appropriate for experiments in which time saving is relevant (e.g. drug screenings). These results are intended to be a reference for the planning of in vitro neurophysiological and neuropharmacological experiments with MEAs
Development and Validation of a Spike Detection and Classification Algorithm Aimed at Implementation on Hardware Devices
No full textSpike detection algorithm improvement, spike waveform projections with PCA and hierarchical classification
No full textDevelopment of a bench-top device for parallel climate-controlled recordings of neuronal cultures activity with microelectrode arrays
No full textTwo binding requirements for in vitro studies on long-term neuronal networks dynamics are (i) finely controlled environmental conditions to keep neuronal cultures viable and provide reliable data for more than a few hours and (ii) parallel operation on multiple neuronal cultures to shorten experimental time scales and enhance data reproducibility. In order to fulfill these needs with a Microelectrode Arrays (MEA)-based system, we designed a stand-alone device that permits to uninterruptedly monitor neuronal cultures activity over long periods, overcoming drawbacks of existing MEA platforms. We integrated in a single device: (i) a closed chamber housing four MEAs equipped with access for chemical manipulations, (ii) environmental control systems and embedded sensors to reproduce and remotely monitor the standard in vitro culture environment on the lab bench (i.e. in terms of temperature, air CO2 and relative humidity), and (iii) a modular MEA interface analog front-end for reliable and parallel recordings. The system has been proven to assure environmental conditions stable, physiological and homogeneos across different cultures. Prolonged recordings (up to 10 days) of spontaneous and pharmacologically stimulated neuronal culture activity have not shown signs of rundown thanks to the environmental stability and have not required to withdraw the cells from the chamber for culture medium manipulations. This system represents an effective MEA-based solution to elucidate neuronal network phenomena with slow dynamics, such as long-term plasticity, effects of chronic pharmacological stimulations or late-onset pathological mechanisms. Biotechnol. Bioeng. 2015;9999: 1-11. © 2015 Wiley Periodicals, Inc
Per una educazione illuministica. I «Racconti morali» di Giambattista Biffi: le fonti
No full textThe article focuses on Giambattista Biffi (1736-1807), an Enlightenment nobleman and thinker of Cremona, member of the Accademia dei Pugni, and on the analysis of his unpublished autograph Racconti morali ad uso d’un fanciullo, held in the State Library of Cremona. These novellas were written with a pedagogical purpose for Daniele Ala, firstborn of Biffi’s friend marquis Gian Francesco Ala. After considering the family’s background and the historical context in which the novellas were composed – the period of the Habsburg reforms – the author dates them and identifies the press sources, both Italian and foreign, from which Biffi based the plot of the stories. Finally, she analyses the inspiring Enlightenment theory of virtue, seen as social utility for people’s wellbeing and happiness.L’articolo verte sulla figura dell’illuminista cremonese Giambattista Biffi (1736-1807), membro dell’Accademia dei Pugni, e sull’analisi dei suoi Racconti morali ad uso d’un fanciullo, autografi e inediti, conservati nella Biblioteca Statale di Cremona. Sono una decina di novelle scritte con un intento pedagogico per il marchesino Daniele Ala, primogenito del marchese Gian Francesco Ala, amico di Biffi. Dopo aver preso in esame il contesto familiare e quello storico in cui sono stati scritti – il periodo delle riforme asburgiche – e averne proposto una datazione, l’autrice identifica le fonti a stampa, sia italiane che straniere, dalle quali Biffi ricavò la trama delle novelle. Infine ne sottolinea la matrice illuministica che proponeva una educazione alla virtù intesa come utilità sociale, per il benessere e la felicità collettiva
Is ventricular sensing always right, when it is left?
No full textBackground: Ventricular sensing in transvenous cardiac implantable electronic devices (CIEDs) occurs conventionally from the right ventricular (RV) channel, though it evolved from epicardial sensing both in pacemakers and implantable cardioverter-defibrillators (ICDs). Hypothesis: The objective of this study was to observe the reliability of left ventricular (LV) sensing by transvenous leads placed in coronary veins. Methods: LV leads were used for sensing and arrhythmia detection in clinical situations where placement of an RV lead across the tricuspid valve was either not preferred or not feasible, or RV signal was unsuitable for arrhythmia detection, or in the event of sensing failure of an RV lead under advisory in cardiac resynchronization therapy defibrillator (CRTD) recipients. Results: Thirty-seven patients had an IS-1 LV lead connected to the RV port of CIEDs (17 pacemakers, 5 cardiac resynchronization therapy pacemaker [CRTP], 2 ICDs, and 13 CRTDs). Along a median 41 (25-67) months follow-up, lead performance remained stable; there were neither undersensing nor oversensing of non-cardiac signals. VT/VF were correctly detected and terminated by ATP and shocks (one and three patients, respectively); no inappropriate arrhythmia detection. Device reprogramming occurred in four CRTD recipients because of transient counting the QRS (short intervals) when paced in LV-only, and in two with T-wave oversensing. Conclusions: Ventricular sensing by an LV lead is feasible in transvenous devices. Sensing programmability is an unmet need: to fix RV lead sensing issues in cardiac resynchronization therapy (CRT) recipients at no risk of infection (no pocket opening); to avoid interaction with the tricuspid valve; to avoid lead redundancy in the vasculature. Moreover, it will be mandatory owing to the loss of lead interchangeability due to the adoption of DF-4 and quadripolar leads
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