1,720,990 research outputs found
Interferogram Average over Wavelength Reflectance Spectroscopy: A Novel Interferometric Technique For Ultrasensitive Label-Free Biosensing with Porous Silicon
No full textPorous silicon (PSi) is a nanostructured material increasingly exploited for both refractometric and (bio)sensing applications, though currently suffering of restricted real applications due to insufficient sensitivity [1].
Here we report on development, characterization, and application (to both refractometry and biosensing) of a novel ultrasensitive technique for label-free discrimination of bulk and surface refractive index changes (namely, Interferogram Average over Wavelength –IAW– reflectance spectroscopy) using PSi interferometer.
The IAW reflectance spectroscopy relies on the calculation of the average value over wavelength of spectral interferograms, namely IAW value. Interferograms are calculated by subtraction (intensity, wavelength by wavelength) of the reflection spectrum, acquired after infiltration of the analyte within the nanopores of the PSi interferometer, from a reference reflection spectrum.
As to refractometric applications, a minimum bulk refraction index variation of 10-6 RIU was experimentally measured using NaCl aqueous solutions, with a theoretical detection limit (DL) of 10-8 RIU.
As proof-of-concept for label-free biosensing applications, the IAW spectroscopy was used to demonstrate detection of BSA adsorption on PSi surface down to a DL of 20 pM [1] while for a “real” biosensing application, concentrations of TNFα (a protein biomarker of inflammation and sepsis) were experimentally monitored through an aptasensor, reaching a DL of 200 pM. Both these results represent a 1000-fold improvement with respect to the commonly used FFT reflectance spectroscopy [2].
In conclusion, the IAW reflectance spectroscopy envisages bringing PSi optical (bio)sensors at the forefront of ultrasensitive label-free biosensing techniques, with application for point-of-care clinical analysis where low analyte concentrations are required to be detected.
Reference
[1] Mariani, S., Strambini, L. M., Barillaro, G., Anal. Chem. 88, 8502–8509 (2016).
[2] Mariani, S., Pino, L., Strambini, L. M., Tedeschi, L., Barillaro, G., ACS Sens., 1 (12), 1471–1479 (2016)
Towards an in-vitro liver lobule model
No full textIn-vitro culture of liver cells on bio-inspired chips., namely liver-on-chip, to form a 3D hepatic tissue morphologically close to its in-vivo counterpart is rapidly emerging for drug testing applications. This paper reports preliminary results towards fabrication of an in-vitro model of the smallest functional liver unit, which is the hepatic lobule. Simultaneous fabrication of out-of-plane micro-channels interconnected by in-plane nanometric-channels is demonstrated by electrochemical etching of n-type silicon in aqueous (48%) HF: (30%) H2O2=1:1 (by vol.) electrolyte through the synergistic work of back-side illumination, avalanche breakdown, and high oxidizing power chemicals
Design and Development of a Fully Wireless Board Enabling Multiple Electrochemical Sensors Operation and Readout for Salivary Diagnostics Applications
No full textThe increasing interest surrounding point of care diagnostics and the rapid development of portable devices has shifted screening and monitoring of pathologies from dedicated lab spaces to personal homes and clinical offices. Among different biofluids to be analyzed, saliva has emerged as one of the most promising medium, due to the non-invasiveness of its collection and its richness in biomarkers. To satisfy a plethora of emerging needs in the field of salivary diagnostics, dedicated devices need to be built that meet stringent performance requirements while also optimizing for versatility and user friendliness. In this regard, we describe here the development of a customized portable electronic board, capable of performing different electrochemical measurements, including open circuit potentiometry, chronoamperometry and cyclic voltammetry in the context of a salivary diagnostic application. The device is also wirelessly powered to allow for on field deployment and the data gathered via the analysis is sent to a mobile device for further processing and display to users
Interferogram average over wavelength spectroscopy: An ultrasensitive technique for biosensing with porous silicon interferometers
No full textHere we report on a high-sensitivity interferometric technique, namely Interferogram Averaged over Wavelength - IAW-reflectance spectroscopy, enabling sub-nanomolar detection (both nonspecific and specific) of proteins to be accomplished in direct (without any amplification) label-free mode using porous silicon (PSi) interferometers. The IAW reflectance spectroscopy is based on both calculation and elaboration of spectral interferograms. Interferograms are obtained by subtracting (intensity, wavelength by wavelength) reflectance spectra acquired on PSi interferometers in buffer solution after protein injection (at different concentrations) from a reference reflectance spectrum acquired in buffer solution before protein injection. The output signal, namely IAW value, is eventually obtained as the average value, calculated over a given wavelength interval, of each interferogram. Using the IAW technique nonspecific adsorption of Bovine Serum Albumin (BSA) down to 0.15 nM (DL=20 pM) and specific detection of Tumor Necrosis Factor (TNFα) down to 3 nM (DL=0.2 nM) was reliably achieved in direct label-free mode using PSi interferometers. Both the results represent a 10000-fold reduction in DL with respect to the current literature on the use of PSi for direct label-free measurements
Quasi-zero-voltage controlled etching of macropores in n-type silicon
No full textHere, we report an experimental study about the controlled etching of macropores in n-type silicon electrodes at quasi-zero anodic voltage using hydrofluoric acid-based photo-electrochemical etching (P-ECE). This breaks a new ground on the controlled electrochemical dissolution of n-type silicon, for which the use of anodic voltage above the electropolishing peaks (Vps, Jps) has been considered to be a golden rule for the etching control, so far. Remarkably, our experimental results clearly show that it is possible to control the etching of macropores at anodic voltages well below (close to zero Volt) the electropolishing peak and that the use of low anodic voltages is beneficial for the fabrication of regular macropores with large diameter (i.e. 10 μm) and spatial pitch (i.e. 20 μm)
Experimental Assessment of Passive UHF-RFID Sensor Tags for Environment and Kinematic Data
No full textRadio Frequency IDentification (RFID) technology and low power electronic sensors may be combined to build wireless passive sensors which might cover many applications ranging from Internet of Things to Healthcare. This work presents a multi-perspective overview of RFID-based sensor tags and then proceed to experimentally characterize the sensing capabilities of two commercial fully-passive RFID sensor tags for acceleration and relative humidity data acquisition, respectively. Measurements are compared with data acquired through commercial traditional non-RFID wired sensor
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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