Sensitivity of Xylella fastidiosa subsp. pauca Salento-1 to light at 410 nm.

All over the world, from America to the Mediterranean Sea, the plant pathogen Xylella fastidiosa represents one of the most difficult challenges with many implications at ecological, agricultural, and economic levels. X. fastidiosa is a rod-shaped Gram-negative bacterium belonging to the family of Xanthomonadaceae. It grows at very low rates and infects a wide range of plants thanks to different vectors. Insects, through their stylets, suck a sap rich in nutrients and inject bacteria into xylem vessels. Since, until now, no antimicrobial treatment has been successfully applied to kill X. fastidiosa and/or prevent its diffusion, in this study, antimicrobial blue light (aBL) was explored as a potential anti-Xylella tool. Xylella fastidiosa subsp. pauca Salento-1, chosen as a model strain, showed a certain degree of sensitivity to light at 410 nm. The killing effect was light dose dependent and bacterial concentration dependent. These preliminary results support the potential of blue light in decontamination of agricultural equipment and/or plant surface; however, further investigations are needed for in vivo applications.

Characterization of hierarchical α-MoO3 plates toward resistive heating synthesis: electrochemical activity of α-MoO3/Pt modified electrode toward methanol oxidation at neutral pH.

The growth of MoO3 hierarchical plates was obtained by direct resistive heating of molybdenum foils at ambient pressure in the absence of any catalysts and templates. Plates synthesized after 60 min resistive heating typically grow in an single-crystalline orthorhombic structure that develop preferentially in the [001] direction, and are characterized by high resolution transmission electron microscopy, selected area diffraction pattern and Raman-scattering measurements. They are about 100-200 nm in thickness and a few tens of micrometers in length. As heating time proceeds to 80 min, plates of α-MoO3 form a branched structure. A more attentive look shows that primary plates formed at until 60 min could serve as substrates for the subsequent growth of secondary belts. Moreover, a full electrochemical characterization of α-MoO3 plates on platinum electrodes was done by cyclic voltammetric experiments, at pH 7 in phosphate buffer, to probe the activity of the proposed composite material as anode to methanol electro-oxidation. Reported results indicate that Pt MoO3 modified electrodes are appropriate to develop new an amperometric non-enzymatic sensor for methanol as well as to make anodes suitable to be used in direct methanol fuel cells working at neutral pH.

Development and characterization of a novel bioactive polymer with antibacterial and lysozyme-like activity.

The development and characterization of a novel bioactive polymer based on the immobilization of glucose oxidase enzyme (GOx) in a polyvinyl alcohol (PVA) film showing antibacterial activity is presented. The PVA-GOx composite material was extensively characterized by UV-vis, X-ray Photoelectron (XPS) spectroscopy and by Fourier Transform Infrared (FTIR) spectroscopy to verify the preservation of enzyme structural integrity and activity. The antimicrobial activity of this composite material against Escherichia coli and Vibrio alginolyticus was assessed. Furthermore the lysozyme-like activity of PVA-GOx was highlighted by a standard assay on Petri dishes employing Micrococcus lysodeikticus cell walls. The findings from this study have implications for future investigations related to the employment of PVA-GOx system as a composite material of pharmaceutical and technological interest.

Detection of Anti-Neospora caninum Antibodies on Dairy Cattle Farms in Southern Italy.

Neosporosis is recognized as one of the major causes of bovine abortion worldwide. Canids are the main definitive host for this parasite and the presence of dogs in the farm is an important factor for the Neospora caninum infection in bovines. Since, in the province of Lecce, located in the Apulia region of Southern Italy, there are no studies showing the presence of the infection in farm animals, the objective was to perform a serological evaluation for anti-N. caninum antibodiesin serum from 706 dairy cattle and 21 farm dogs located in 40 farms uniformlydistributed over the territory.The presence of N. caninum infection was confirmed in 90.0% (36/40) of the 40 farms examined. The results obtained on all serum samples by an enzyme-linked immunosorbent assay (ID Screen®Neospora caninum competition ELISA kit) for anti-N. caninum antibodies showed a seropositivity rate of 21.1% (149/706) among dairy cows, with a statistically significant higher percentage of positive subjects in the animals over two years old and a positivity rate of 42.9% (9/21) in tested dogs. The obtained data confirmed the presence of neosporosis even in the Lecce area, where it could therefore represent an important cause of abortion and economic losses.

Airborne concentrations of SARS-CoV-2 in indoor community environments in Italy.

COVID-19 pandemic raised a debate regarding the role of airborne transmission. Information regarding virus-laden aerosol concentrations is still scarce in community indoors and what are the risks for general public and the efficiency of restriction policies. This work investigates, for the first time in Italy, the presence of SARS-CoV-2 RNA in air samples collected in different community indoors (one train station, two food markets, one canteen, one shopping centre, one hair salon, and one pharmacy) in three Italian cities: metropolitan city of Venice (NE of Italy), Bologna (central Italy), and Lecce (SE of Italy). Air samples were collected during the maximum spread of the second wave of pandemic in Italy (November and December 2020). All collected samples tested negative for the presence of SARS-CoV-2, using both real-time RT-PCR and ddPCR, and no significant differences were observed comparing samples taken with and without customers. Modelling average concentrations, using influx of customers' data and local epidemiological information, indicated low values (i.e. < 0.8 copies m-3 when cotton facemasks are used and even lower for surgical facemasks). The results, even if with some limitations, suggest that the restrictive policies enforced could effectively reduce the risk of airborne transmissions in the community indoor investigated, providing that physical distance is respected.

A review on measurements of SARS-CoV-2 genetic material in air in outdoor and indoor environments: Implication for airborne transmission.

Airborne transmission of SARS-CoV-2 has been object of debate in the scientific community since the beginning of COVID-19 pandemic. This mechanism of transmission could arise from virus-laden aerosol released by infected individuals and it is influenced by several factors. Among these, the concentration and size distribution of virus-laden particles play an important role. The knowledge regarding aerosol transmission increases as new evidence is collected in different studies, even if it is not yet available a standard protocol regarding air sampling and analysis, which can create difficulties in the interpretation and application of results. This work reports a systematic review of current knowledge gained by 73 published papers on experimental determination of SARS-CoV-2 RNA in air comparing different environments: outdoors, indoor hospitals and healthcare settings, and public community indoors. Selected papers furnished 77 datasets: outdoor studies (9/77, 11.7%) and indoor studies (68/77. 88.3%). The indoor datasets in hospitals were the vast majority (58/68, 85.3%), and the remaining (10/68, 14.7%) were classified as community indoors. The fraction of studies having positive samples, as well as positivity rates (i.e. ratios between positive and total samples) are significantly larger in hospitals compared to the other typologies of sites. Contamination of surfaces was more frequent (in indoor datasets) compared to contamination of air samples; however, the average positivity rate was lower compared to that of air. Concentrations of SARS-CoV-2 RNA in air were highly variables and, on average, lower in outdoors compared to indoors. Among indoors, concentrations in community indoors appear to be lower than those in hospitals and healthcare settings.

Mediator-free amperometric glucose biosensor based on glucose oxidase entrapped in poly(vinyl alcohol) matrix.

A simple and novel amperometric biosensor for glucose detection is proposed. It is based on the immobilization of glucose oxidase (GOx) in a poly(vinyl alcohol) (PVA) matrix directly drop casted on a platinum electrode surface (Pt/GOx-PVA). Glucose was determined in the absence of a mediator used to transfer electrons between the electrode and the enzyme. The correlation between peak current (i(p)) and scan rate has been verified and the effect of pH solution has been checked. Glucose detection has been performed amperometrically at -400 mV by using pulsed amperometric detection (PAD). Under the selected optimal conditions, the biosensor showed low detection limit (10 µM), wide dynamic range (0.1-37 mM) and high sensitivity. The biosensor amperometric response revealed it to be specific to glucose without significant interference from other sugars and electroactive species coexisting with glucose in biological fluids. Response stability was another interesting feature of the developed system as it was almost completely recovered when the biosensor was left in opportune storage conditions (i.e., a response decrease of only 13% after 35 days in air at room temperature). Finally, X-Ray Photoelectron Spectroscopy (XPS) characterization revealed a homogeneous film deposited on the Pt substrate whose structure is also preserved under operative conditions.

Chemical characterization of red cells from the black sea urchin Arbacia lixula by X-ray photoelectron spectroscopy.

Red spherula cells (RSC) from sea urchin coelomic fluid have attracted great interest for their specific and intriguing properties, such as for example antimicrobial activities and immune response, that probably tie in with their red characteristic pigments. Although to date different studies have been reported aimed to chemically characterize their pigments extracted from the cells, few data are available about the chemical characterization of the cell surface. In this work, a systematic chemical characterization of the RSC surface by X-ray photoelectron spectroscopy (XPS) analysis is described. The results were compared with data on colorless cells from the same coelomic fluid sample. Our observations evidenced that the two cell types were characterized by the presence of different chemical functional groups. In particular, the colorless cells are dominated by the presence of alkyl, alcohol, amide, and carboxyl groups in accordance with other similar cell types, enriched in Na+ and Cl- ions. Traces of elements like S (sulphonates) and P (phosphates) are also present. On the other hand, the RSC in addition to the alkyl groups show a reduction in the content of amide groups, accompanied by the anomalous presence of keto-enolic groups that probably can be associated with the presence of quinones/hydro-quinones from red pigments. A chemical enrichment in elements such as Cl- and Mg2+ and sulphate groups (-R-O-SO3 -), as well as the presence of sulphides and phosphates traces, is evident. The absence of carbonate groups is also observed in both cell populations, confirming the absence of sodium and magnesium carbonate salts. No traces of toxic elements (i.e., heavy metals) have been revealed.

Phosphate Modified Screen Printed Electrodes by LIFT Treatment for Glucose Detection.

The design of new materials as active layers is important for electrochemical sensor and biosensor development. Among the techniques for the modification and functionalization of electrodes, the laser induced forward transfer (LIFT) has emerged as a powerful physisorption method for the deposition of various materials (even labile materials like enzymes) that results in intimate and stable contact with target surface. In this work, Pt, Au, and glassy carbon screen printed electrodes (SPEs) treated by LIFT with phosphate buffer have been characterized by scanning electron microscopy and atomic force microscopy to reveal a flattening effect of all surfaces. The electrochemical characterization by cyclic voltammetry shows significant differences depending on the electrode material. The electroactivity of Au is reduced while that of glassy carbon and Pt is greatly enhanced. In particular, the electrochemical behavior of a phosphate LIFT treated Pt showed a marked enrichment of hydrogen adsorbed layer, suggesting an elevated electrocatalytic activity towards glucose oxidation. When Pt electrodes modified in this way were used as an effective glucose sensor, a 1⁻10 mM linear response and a 10 µM detection limit were obtained. A possible role of phosphate that was securely immobilized on a Pt surface, as evidenced by XPS analysis, enhancing the glucose electrooxidation is discussed.

A novel nonenzymatic amperometric hydrogen peroxide sensor based on CuO@Cu2O nanowires embedded into poly(vinyl alcohol).

A new, very simple, rapid and inexpensive nonenzymatic amperometric sensor for hydrogen peroxide (H2O2) detection is proposed. It is based on the immobilization of cupric/cuprous oxide core shell nanowires (CuO@Cu2O-NWs) in a poly(vinyl alcohol) (PVA) matrix directly drop casted on a glassy carbon electrode surface to make a CuO@Cu2O core shell like NWs PVA embedded (CuO@Cu2O-NWs/PVA) sensor. CuO nanowires with mean diameters of 120-170nm and length in the range 2-5µm were grown by a simple catalyst-free thermal oxidation process based on resistive heating of pure copper wires at ambient conditions. The oxidation process of the copper wire surface led to the formation of a three layered structure: a thick Cu2O bottom layer, a CuO thin intermediate layer and CuO nanowires. CuO nanowires were carefully scratched from Cu2O layer with a sharp knife, dispersed into ethanol and sonicated. Then, the NWs were embedded in PVA matrix. The morphological and spectroscopic characterization of synthesized CuO-NWs and CuO@Cu2O-NWs/PVA were performed by transmission electron microscopy (TEM), selected area diffraction pattern (SAD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. Moreover a complete electrochemical characterization of these new CuO@Cu2O-NWs/PVA modified glassy carbon electrodes was performed by Cyclic Voltammetry (CV) and Cronoamperometry (CA) in phosphate buffer (pH=7; I=0.2) to investigate the sensing properties of this material against H2O2. The electrochemical performances of proposed sensors as high sensitivity, fast response, reproducibility and selectivity make them suitable for the quantitative determination of hydrogen peroxide substrate in batch analysis.

Te oxide nanowires as advanced materials for amperometric nonenzymatic hydrogen peroxide sensing.

A new nonenzymatic platinum Te oxide nanowires modified electrode (Pt/TeO2-NWs) for amperometric detection of hydrogen peroxide (H2O2) is proposed. The modified electrode has been developed by direct drop casting, with TeO2 nanowires (TeO2-NWs), synthesized by thermal evaporation of Te(0) in an oxygen atmosphere. The morphological and spectroscopic characterization of the TeO2-NWs as synthesized on Pt foil was performed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. XPS and XRD analyses are especially involved to gain information on the chemical environment of TeO2-NWs in contact with Pt surface. Moreover electrochemical characterization of these new modified Pt/TeO2-NWs modified electrodes was performed by Cyclic Voltammetry (CV) and Cronoamperometry (CA) in phosphate buffer (pH=7; I=0.2) to investigate the sensing properties of this material against H2O2. The proposed sensor exhibits a wide linear and dynamic range from 2 µM to 16 mM (R(2)=0.9998) and the detection limit is estimated to be 0.6 µM (S/N=3). Moreover, this sensor shows a rapid amperometric response time of less than 5s and possessed good reproducibility. These results indicate that Pt/TeO2-NWs composite is suitable to be used as material for sensing applications.