Showing papers by "Giuseppe Coppola published in 2018"

Label-free sensing of ultralow-weight molecules with all-dielectric metasurfaces supporting bound states in the continuum

Abstract: The realization of an efficient optical sensor based on a photonic crystal metasurface supporting bound states in the continuum is reported. Liquids with different refractive indices, ranging from 1.4000 to 1.4480, are infiltrated in a microfluidic chamber bonded to the sensing dielectric metasurface. A bulk liquid sensitivity of 178 nm/RIU is achieved, while a Q-factor of about 2000 gives a sensor figure of merit up to 445 in air at both visible and infrared excitations. Furthermore, the detection of ultralow-molecular-weight (186 Da) molecules is demonstrated with a record resonance shift of 6 nm per less than a 1 nm thick single molecular layer. The system exploits a normal-to-the-surface optical launching scheme, with excellent interrogation stability and demonstrates alignment-free performances, overcoming the limits of standard photonic crystals and plasmonic resonant configurations.

Air pollution and female fertility: a systematic review of literature

Abstract: Air pollution is a cause of concern for human health. For instance, it is associated with an increased risk for cancer, cardiovascular and respiratory disorders. In vitro and in vivo studies suggested that air pollutants could act as endocrine disruptors, promote oxidative stress and exert genotoxic effect. Whether air pollution affects female infertility is under debate. The aim of the present study was to conduct a systematic review of studies that evaluated the impact of air pollution on female infertility. We systematically searched the MEDLINE (PubMed) and SCOPUS databases to identify all relevant studies published before October 2017. No time or language restrictions were adopted, and queries were limited to human studies. We also hand-searched the reference lists of relevant studies to ensure we did not miss pertinent studies. The risk of bias and quality assessment of the studies identified were performed using the Newcastle-Ottawa Scale. Primary outcomes were conception rate after spontaneous intercourse and live birth rate after in vitro fertilization (IVF) procedures. Secondary outcomes were first trimester miscarriage, stillbirths, infertility, number of oocytes and embryo retrieved. Eleven articles were included in the analysis. We found that in the IVF population, nitrogen dioxide and ozone were associated with a reduced live birth rate while particulate matter of 10 mm was associated with increased miscarriage. Furthermore, in the general population, particulate matter of 2.5 mm and between 2.5 and 10 mm were associated with reduced fecundability, whereas sulfur dioxide, carbon monoxide and nitrogen dioxide might promote miscarriage and stillbirths. The main limitation of our findigns resides in the fact that the desegn of studies included are observational and retrospective. Furthermore, there was a wide heterogenity among studies. Although larger trials are required before drawing definitive conclusions, it seems that air pollution could represent a matter of concern for female infertility.

PDMS-Based Microfluidic Devices for Cell Culture

Abstract: Microfluidic technology has affirmed itself as a powerful tool in medical and biological research by offering the possibility of managing biological samples in tiny channels and chambers. Among the different applications, the use of microfluidics for cell cultures has attracted much interest from scientists worldwide. Traditional cell culture methods need high quantities of samples and reagents that are strongly reduced in miniaturized systems. In addition, the microenvironment is better controlled by scaling down. In this paper, we provide an overview of the aspects related to the design of a novel microfluidic culture chamber, the fabrication approach based on polydimethylsiloxane (PDMS) soft-lithography, and the most critical issues in shrinking the size of the system.

Excitation of Bloch Surface Waves on an Optical Fiber Tip

Abstract: DOI: 10.1002/adom.201800477 to the development of extremely sensitive surface plasmon resonance (SPR) biosensors, which can rely on mature fabrication technologies, standard biofunctionalization protocols, and commercial scale production.[1,3–5] In spite of the excellent performance achieved by state-of-the-art SPR platforms, with reported limits of detection (LODs) approaching 10−7 refractive index units (RIU),[4,6] further improvements are unavoidably limited by the reliance on lossy materials (typically metals). This yields an undesirable resonance broadening, thereby posing an upper bound to the overall figure of merit (FOM).[6] For this reason, there is a strong push to explore alternative, larger-FOM SW implementations.[1,7–11] As a prominent example, Bloch SWs (BSWs) on truncated 1D photonic crystals (1DPCs) represent an attractive alternative to SPPs, as recently demonstrated in several proof-of-principle studies.[9,12–16] In spite of sensitivities to local refractive index (RI) changes lower than SPR platforms, the completely dielectric low-loss structure of a BSW sensor yields sensibly sharper resonances, leading to generally larger FOMs.[13–17] This has recently led to the successful development of label-free biosensors exhibiting competitive performance in practical biomolecular detections.[18–25] Moreover, BSW structures offer further benefits with respect to other SW-based counterparts, such as easy realization and experimental observation, and great flexibility in terms of wavelength range of operation, materials choice, and tailoring of the field distribution for specific sensing applications.[1,9,13–15,17,26–28] While most sensing platforms proposed in the literature rely on bulky prism-coupled planar configurations,[12–26] the integration of BSW structures with optical fibers would bring significant benefits in terms of compactness, light weight, remote sensing capability, biocompatibility, and ease of interrogation. This is especially attractive within the emerging “labon-fiber” technology framework.[29–34] The interest in this topic has started growing within the last two years, as witnessed by theoretical studies of BSW sensors based on the use of D-type fibers,[35] and unclad regions of multimode fibers.[36] A first experimental demonstration on a tapered single-mode fiber has also been provided very recently.[37] Within this context, a more intriguing scenario is represented by the integration of the resonant structure directly on the fiber tip. This would allow exploiting fabrication methodologies typically adopted for photonic biochips, thereby enabling the development of probes The integration of structures supporting Bloch surface waves (BSWs) with optical fibers is highly desirable, since it would enable the development of high-figure-of-merit miniaturized all-fiber optrodes, opening new pathways within the “lab-on-fiber” roadmap. Here, the first experimental demonstration of grating-assisted excitation of BSWs on the tip of single-mode fibers in the near-infrared region is provided. This is attained via fabrication of a 1D diffraction grating on the fiber facet, and subsequent deposition of a 1D photonic crystal. In spite of a resonance broadening due to grating-induced morphological perturbations, the measured Q-factor of 50 is still higher than typical lab-on-tip plasmonic-probe benchmarks. With a view toward biomolecular sensing, a surface sensitivity of 1.22 nm nm−1 of homogeneous overlay deposited over the active region, which is in line with most plasmonic optrodes largely used in connection with optical fibers, is evaluated. The results also highlight the current limitations and the challenges to face for the development of advanced BSW-based fiber-tip platforms for biological sensing applications. Optical Fiber Sensors

Free-Space Schottky Graphene/Silicon Photodetectors Operating at 2 μm

Abstract: This paper presents the design, fabrication, and characterization of Schottky graphene/silicon photodetectors that operate at a wavelength of 2 μm. These graphene/silicon junctions are carefully characterized using electric and optical measurements over the temperature range from 280–315 K. The photodetectors show external responsivity of 0.16 mA/W at room temperature under zero bias conditions, which is in excellent agreement with the theoretical predictions. In addition, the device performance is discussed in terms of the noise equivalent power and operating bandwidth. To the best of our knowledge, these are the first Si-based photodetectors designed for operation in free space at 2 μm. The proposed devices will pave the way toward development of hybrid graphene-Si free-space illuminated photodetectors operating at 2 μm for applications including free-space optical communications, optical coherence tomography and light-based radar systems.

Metabolic enhancers supporting 1-carbon cycle affect sperm functionality: an in vitro comparative study.

Abstract: The sperm plasma membrane is a sensitive target to oxidative stress. The most representative reactive oxygen species (ROS) scavengers in the genital tract, hypotaurine and glutathione, require, for their synthesis, cysteine whose availability is associated with the 1-carbon cycle (1-CC). Human, bovine and ascidian spermatozoa were incubated with compounds supporting the 1-CC (Vitamin B6, Methylcobalamin, 5 Methyl Tetrahydrofolate, Zinc Bisglycinate and N-acetyl-cysteine) (TRT) and compared to the effects induced solely by N-acetyl-cysteine (NAC). In control groups (CNTRL), spermatozoa were incubated with medium alone. After 90 and 180 minutes of incubation, the mitochondrial membrane potential (ΔΨM) in TRT and NAC was significantly (P < 0.01) higher than in CNTRL. At H2DCFDA evaluation, ROS production differed between species whereas, at 2-OH Ethidium, it significantly decreased in bovine TRT group. Intracellular pH (pHi) did not significantly vary in relation to treatment. In ascidian spermatozoa, the NAC supplementation decreased external pH, which in turn brought to a pHi lowering. Buffering seawater with NaHCO3 reversed the beneficial effects of N-acetyl-cysteine supplementation. In conclusion, both fully supporting the 1-CC and treatment with N-acetyl-cysteine alone improved kinetics, ΔΨM and ROS production in mammalian sperm demonstrating for the first time the direct in vitro effects of these compounds on sperm functionality.

Integrable Near-Infrared Photodetectors Based on Hybrid Erbium/Silicon Junctions.

Abstract: This paper presents the design, fabrication, and characterization of Schottky erbium/silicon photodetectors working at 1.55 µm. These erbium/silicon junctions are carefully characterized using both electric and optical measurements at room temperature. A Schottky barrier ΦB of ~673 meV is extrapolated; the photodetectors show external responsivity of 0.55 mA/W at room temperature under an applied reverse bias of 8 V. In addition, the device performance is discussed in terms of normalized noise and noise-equivalent power. The proposed devices will pave the way towards the development of Er-based photodetectors and light sources to be monolithically integrated in the same silicon substrate, and both operating at 1.55 µm.