1,720,964 research outputs found
Bacteriostatic, silver-doped, zirconia-based thin coatings for temporary fixation devices tuning stem cells' expression of adhesion-relevant genes and proteins
Full text linkTemporary fixation devices must support bone healing, be easily removed without bone tissue overgrowth, and reduce the risk of infection. To match these needs, mechanically and chemically stable thin coatings, based on a zirconia matrix doped with silver (ZrO2-Ag), were sputtered on Ti6Al4V. Coatings with two silver concentrations were produced: a low (0.2 % at Ag) concentration (AL) for bacteriostatic effect and a high (0.5 % at Ag) concentration (AH) for antibacterial properties. Surfaces were characterized for silver content and release, mechanical adhesion, morphology, roughness, wettability, and surface zeta potential, reporting high stability and a continuous Ag release over 28 days. Direct cytocompatibility was shown for human mesenchymal stem cells (hMSC), while antibacterial properties were verified towards Staphylococcus aureus. Results revealed non-toxic and anti-adhesion effects of AL that were deeply investigated towards hMSC by a multi-omics approach. Transcriptomics revealed a down-regulation of cadherins- and integrins-related genes involved in the cell-to-cell and cell-to-substrate adhesion, whereas proteomics confirmed a reduced expression of adhesion proteins (Talin and Ras homolog family member A - RhoA). The OMICS profiles were matched by bioinformatics analysis, confirming a cluster of preserved biological functions strongly related to the cells' adhesion but not to apoptosis. Therefore, AL is a good candidate for bone temporary fixation devices, not interfering with bone healing (cytocompatible), avoiding bone adhesion on the implant surface, and being bacteriostatic
Combining Electrospinning and Photoinduced Reactions to Fabricate Cytocompatible and Antibacterial Ag Nanoparticle-Decorated Polymeric Membranes
No full textComposite nanofibrous membranes hold significant potential for the development of innovative biomedical materials and applications as their properties can be tuned by combining the synergistic effects of the nanofiller and the polymer matrix. Moreover, the nanofibrous structure can further enhance this feature thanks to the extremely high functional surface area. In the present work, a simple and fast method for the preparation of electrospun composite membranes based on cross-linked poly(ethylene oxide) (PEO) nanofibers and silver nanoparticles (Ag NPs) is proposed. For this purpose, a precursor of the Ag NPs (i.e., AgNO3) is introduced into the aqueous solution of PEO in the presence of a suitable photoinitiator and a photo-cross-linker. Electrospinning of the solution is carried out, and the subsequent irradiation of the electrospun mat allows the simultaneous photoinduced cross-linking of PEO and the photoinduced synthesis of Ag NPs. The in situ generation of Ag NPs is confirmed through different characterization techniques (i.e., UV-vis spectroscopy, dynamic light scattering, and scanning electron microscopy). The structural, morphological, and mechanical properties of the resulting electrospun composite nanofibers are analyzed, and the effect of the content of the Ag NP precursor is evaluated. It is demonstrated that PEO fibers are chemically resistant and mechanically robust thanks to cross-linking, while Ag NPs induce significant antibacterial activity to the electrospun materials, which are also shown to be noncytotoxic by using both human fibroblasts and 3D-reconstructed skin equivalents. The proposed PEO-based nanofibrous mats decorated with Ag NPs thus exhibit promising potential as biomedical materials, especially for wound healing applications
Exploring the In Vitro Antibacterial Potential of Specific Probiotic Strains against Oral Pathogens
No full textThe microbiota in the oral cavity has a strict connection to its host. Its imbalance may determine oral diseases and can also have an impact on the systemic health. Probiotic strains may help in the restoration of a balanced condition. For this purpose, we screened the antibacterial and antiadhesive activities of many viable probiotic strains (Lactobacillus acidophilus PBS066, Lactobacillus crispatus LCR030, Lactobacillus gasseri LG050, Lactiplantibacillus plantarum PBS067, Limosilactobacillus reuteri PBS072, Lacticaseibacillus rhamnosus LRH020, Bifidobacterium animalis subsp. lactis BL050, Lacticaseibacillus paracasei LPC 1101, L. paracasei LPC 1082, and L. paracasei LPC 1114) against two main oral pathogens, Streptococcus mutans and Aggregatibacter actinomycetemcomitans, involved in dental caries and periodontal disease development and progression. Considering both the agar overlay preventive and treatment models, seven probiotics determined greater inhibition zones against the tested pathogens. This behavior was further analyzed by the plate count method and scanning electron microscope imaging. L. plantarum PBS067, L. rhamnosus LRH020, L. paracasei LPC 1101, L. paracasei LPC 1082, and L. paracasei LPC 1114 prevent the growth and adhesion of oral pathogens in a strain-specific manner (p < 0.0001). These probiotics might be considered as an alternative effective adjuvant to improve oral and systemic well-being for future personalized treatments
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Washing resistant antibacterial composite coatings on cotton textiles
Full text linkSeveral techniques have been developed to confer antibacterial properties to cotton textiles using silver nanoparticles. However, the antimicrobial performance of such a modified fabric can drastically decrease after a washing treatment. The aim of this work has been to develop antibacterial composite coatings with improved water resistance, deposited on cotton via the co-sputtering technique. The thin coatings, composed of a silica, alumina or zirconia matrix, with well embedded silver nanoclusters, were made to homogenously cover the cotton threads. The amount of silver was modulated, as was the power applied to the target, that is, 3 W for a lower amount and 5 W for a larger amount. The release of silver ions from the coatings into distilled water was very low, even after 14 days (less than 1 ppm) for all the coatings. The coated and uncoated cotton textiles were directly infected with the textile-colonizing pathogens Escherichia coli and Pseudomonas aeruginosa. After 24 h, a count of the colony forming units (CFU) revealed that the textiles coated with either the silver nanocluster/silica or zirconia matrix coatings were effective in preventing the adhesion and proliferation of E. coli bacteria, thereby preserving the textiles from contamination. However, P. aeruginosa was only absent in the case of the silica coatings or when the zirconia and alumina matrix coatings contained a large amount of silver. In all the considered cases, the CFU number was reduced with respect to the uncoated textiles. The durability of all the coatings was verified after ten washing cycles. Finally, coated textiles reported to be cytocompatible towards human fibroblasts and keratinocytes after simulating the release of toxic compounds or by directly seeding cells onto materials’ surface
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