Versatile and non-cytotoxic GelMA-xanthan gum biomaterial ink for extrusion-based 3D bioprinting

Extrusion-based 3D bioprinting allows the 3D printing of bioinks, composed of cells and biomaterials, to mimic the complex 3D hierarchical structure of native tissues. Successful 3D bioprinting requires bioinks with specific properties, such as biocompatibility, printability, and biodegradability according to the desired application. In the present work, we aimed at developing a new versatile blend of gelatin methacryloyl-xanthan gum (GelMA-XG) suitable for extrusion-based 3D bioprinting with a straightforward process. To this end, we first optimized the process of gelatin methacryloyl (GelMA) synthesis by investigating the impact of different buffer solutions on the degree of functionalization, swelling degree, and degradation rate. The addition of xanthan gum (XG) enabled further tuning of biodegradability and an improvement of GelMA printability. Specifically, an optimal concentration of XG was found through rheological characterization and printability tests. The optimized blend showed enhanced printability and improved shape fidelity as well as its degradation products turned out to be non-cytotoxic, thus laying the foundation for cell-based applications. In conclusion, our newly developed biomaterial ink is a promising candidate for extrusion-based 3D bioprinting

Evaluation of a sampling method for Xylella fastidiosa detection in olive trees

To assess the presence of the xylem-limited bacterium Xylella fastidiosa subsp. pauca strain CoDiRO in olive trees, a specific sampling method was evaluated. Symptomatic and symptomless plants were randomly selected in four olive orchards located in the province of Lecce (Southern Italy). The crown of each plant was subdivided into a lower and an upper portion; four samples were collected from each layer in the main four cardinal directions. A total of eight samples per plant, composed of one- or two-year-old asymptomatic twigs, were collected next to branches showing leafscorch symptoms. In this preliminary study, the null hypothesis was tested. i.e. there is no difference between the lower and the upper portions of the tree canopy and across the four cardinal directions. Samples (472), collected from 60 plants belonging to 11 different olive cultivars, were tested by qPCR. Out of 236 samples taken from the upper and lower parts of the canopy only 38.1% of lower samples, in contrast to 56.8% taken from the upper crown layer, were positive to the bacterium,. The McNemar test determined that there is a statistically significant difference in the proportion of positive samples between the upper and lower crown (p < 0.001). The Cochran’s Q test was performed to evaluate differences in the four cardinal directions. The null hypothesis suggesting there is no difference across cardinal directions was confirmed (p = 0.097). Based on these preliminary results, it appears that sampling should be directed to the upper part of the canopy. However, further studies are needed to improve the efficiency of the sampling technique

Screening of olive germplasm for resistance to Xylella fastidiosa ST53: the state of the art

While different sources of natural resistance to X. fastidiosa have been described in grapevines and citrus, lack of solid information exists on possible sources of resistance/tolerance in the cultivars that characterize the wide olive germplasm. Preliminary field observations and laboratory analyses of a few cultivars, have shown that differential responses to X. fastidiosa infections exist. To confirm these preliminary findings, a large panel of olive cultivars is being specifically investigated. Currently, the screening procedure relies on field observations looking for symptomless subjects (trees of known cultivars/volunteer seedlings), mechanical inoculations, qualitative and quantitative diagnostic assays (ELISA & qPCR) and, in selected cases, comparative transcriptomic profiling. Field experiments include the planting of the target cultivars/selections in an infected area under high inoculum pressure. All the plots are located in the Apulia Region (Italy) in the demarcated infected area, surrounded by X. fastidiosa heavily affected olive groves. A first experimental plot was established in April 2015 with 10 different cultivars, which was extended in 2016 to 49 cultivars, and will be further enlarged in 2017 with the addition of 40 new accessions. Other plots, comprising newly planted or grafted cultivars (over 260 cvs) have been also established, bringing to over 300 the total number of accessions under evaluation. Cvs Leccino and FS-17®, both expressing interesting traits of resistance, have already been identified

How Close Do We Live to Water? A Global Analysis of Population Distance to Freshwater Bodies

Traditionally, people have inhabited places with ready access to fresh water. Today, over 50% of the global population lives in urban areas, and water can be directed via tens of kilometres of pipelines. Still, however, a large part of the world's population is directly dependent on access to natural freshwater sources. So how are inhabited places related to the location of freshwater bodies today? We present a high-resolution global analysis of how close present-day populations live to surface freshwater. We aim to increase the understanding of the relationship between inhabited places, distance to surface freshwater bodies, and climatic characteristics in different climate zones and administrative regions. Our results show that over 50% of the world's population lives closer than 3 km to a surface freshwater body, and only 10% of the population lives further than 10 km away. There are, however, remarkable differences between administrative regions and climatic zones. Populations in Australia, Asia, and Europe live closest to water. Although populations in arid zones live furthest away from freshwater bodies in absolute terms, relatively speaking they live closest to water considering the limited number of freshwater bodies in those areas. Population distributions in arid zones show statistically significant relationships with a combination of climatic factors and distance to water, whilst in other zones there is no statistically significant relationship with distance to water. Global studies on development and climate adaptation can benefit from an improved understanding of these relationships between human populations and the distance to fresh water

Global Intraurban Intake Fractions for Primary Air Pollutants from Vehicles and Other Distributed Sources

We model intraurban intake fraction (iF) values for distributed ground-level emissions in all 3646 global cities with more than 100,000 inhabitants, encompassing a total population of 2.0 billion. For conserved primary pollutants, population-weighted median, mean, and interquartile range iF values are 26, 39, and 14-52 ppm, respectively, where 1 ppm signifies 1 g inhaled/t emitted. The global mean urban iF reported here is roughly twice as large as previous estimates for cities in the United States and Europe. Intake fractions vary among cities owing to differences in population size, population density, and meteorology. Sorting by size, population-weighted mean iF values are 65, 35, and 15 ppm, respectively, for cities with populations larger than 3, 0.6-3, and 0.1-0.6 million. The 20 worldwide megacities (each &gt;10 million people) have a population-weighted mean iF of 83 ppm. Mean intraurban iF values are greatest in Asia and lowest in land-rich high-income regions. Country-average iF values vary by a factor of 3 among the 10 nations with the largest urban populations

Detection of Xylella fastidiosa: validation and implementation of routine testing methods

Accurate and early detection of Xylella fastidiosa (Xf) is a major challenge due to the wide range of host plants (different matrices/ tissues, rate of host colonization) and the occurrence of symptomless bacterial infections. The recent establishment of this exotic plant pathogenic bacterium in the EU territory and the large panel of EU susceptible host plants increased the need for rapid diagnostic tools suitable for processing large number of samples and from different sources. Although, several approaches are currently available for the detection of Xf in the host plants and vectors, there is a need for harmonized protocols and user-friendly diagnostic tests. In this study, we compared the sensitivity and the reliability of a selected panel of currently available protocols (ELISA, PCR, qPCR), in comparison with novel approaches based on automatized diagnostic platform and on DTBIA and LAMP-based assays. The overall results showed that: (i) although resulting in different diagnostic sensitivity all the approaches tested were able to detect the bacterium in samples from symptomless plants; (ii) Real-time LAMP assay based using crude plant sap can represent a rapid and reliable screening test; (iii) Real-time quantitative PCR assays had the higher diagnostic and analytical sensitivity; (iv) the use of automatized platform allowed to prepare PCR-templates with high and standardized quality for highly reliable diagnostic results; (v) DTBIA had the lowest diagnostic sensitivity, yet representing a useful approach when movement of Xf infected materials is limited due to the phytosanitary regulations