1,720,957 research outputs found
Electrically Triggered Release of a Small Molecule Drug from a Polyelectrolyte Multilayer Coating
No full textAvailable in PMC 2011 December 14.Electrically triggered drug delivery represents an attractive option for actively and remotely controlling the release of a therapeutic from an implantable device (e.g., a “pharmacy-on-a-chip”). Here we report the fabrication of nanoscale thin films that can release precise quantities of a small molecule drug in response to application of a small, anodic electric potential of at least +0.5 V versus Ag/AgCl. Films containing negatively charged Prussian Blue (PB) nanoparticles and positively charged gentamicin, a small hydrophilic antibiotic, were fabricated using layer-by-layer (LbL) assembly. When oxidized, the PB nanoparticles shift from negatively charged to neutral, inducing dissolution of the film. Films with thicknesses in the range 100−500 nm corresponding to drug loadings of 1−4 μg/cm2 were characterized. We demonstrate control over the drug dosage by tuning the film thickness as well as the magnitude of the applied voltage. Drug release kinetics ranging from triggered burst release to on/off, or pulsatile release, were achieved by applying different electric potential profiles. Finally, the in vitro efficacy of the released drug was confirmed against Staphylococcus aureus bacteria. Given the versatility of an external electrical stimulus and the ability of the LbL assembly to conformally coat a variety of substrates regardless of size, shape, or chemical composition, we maintain that electrically controlled release of a drug from an LbL-coated surface could have applications in both implantable medical devices and transdermal drug delivery systems.National Science Foundation (U.S.). Materials Research Science and Engineering Centers (Program) (award number DMR – 0819762)National Institute on Aging (grant number 5R01AG029601-03)National Institute of Dental and Craniofacial Research (U.S.) (grant number 5R01AG029601-03
The effectiveness of the controlled release of gentamicin from polyelectrolyte multilayers in the treatment of Staphylococcus aureus infection in a rabbit bone model
Get PDFWhile the infection rate of orthopedic implants is low, the required treatment, which can involve six weeks of antibiotic therapy and two additional surgical operations, is life threatening and expensive, and thus motivates the development of a one-stage re-implantation procedure. Polyelectrolyte multilayers incorporating gentamicin were fabricated using the layer-by-layer deposition process for use as a device coating to address an existing bone infection in a direct implant exchange operation. The films eluted about 70% of their payload in vitro during the first three days and subsequently continued to release drug for more than four additional weeks, reaching a total average release of over 550 μg/cm[superscript 2]. The coatings were demonstrated to be bactericidal against Staphylococcus aureus, and degradation products were generally nontoxic towards MC3T3-E1 murine preosteoblasts. Film-coated titanium implants were compared to uncoated implants in an in vivo S. aureus bone infection model. After a direct exchange procedure, the antimicrobial-coated devices yielded bone homogenates with a significantly lower degree of infection than uncoated devices at both day four (p < 0.004) and day seven (p < 0.03). This study has demonstrated that a self-assembled ultrathin film coating is capable of effectively treating an experimental bone infection in vivo and lays the foundation for development of a multi-therapeutic film for optimized, synergistic treatment of pain, infection, and osteomyelitis.National Institutes of Health (U.S.) (National Institute on Aging Grant 5R01AG029601-03
Controlled release of gentamicin from polyelectrolyte multilayers to treat implant-related infection
Get PDFThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 186-203).Polyelectrolyte multilayered (PEM) coatings were fabricated to incorporate and release the small, hydrophilic antibiotic gentamicin from implant surfaces for infection control. The use of a cationic hydrolytically cleavable poly(p-amino ester) rendered these films biodegradable, yielding both diffusion-based and surface-erosion based release of this therapeutic. The Layer-by- Layer (LbL) assembly platform was used to create conformal, micron scale reservoirs with highly tunable drug release. Film release profiles were engineered through film architecture design and post-processing crosslinking techniques. Delivery of gentamicin was sustained for weeks, which is a significant improvement from previous gentamicin-releasing LbL systems. To gain better insight on the mechanisms of release and aid in rational film design, a theoretical treatment of the physical system was performed. These results include an analytical mathematical model describing the release of drug per surface area of film as a function of time as well as a computational model that simulates the time-dependent concentration profiles in these LbL systems. These erodible, antibiotic coatings were demonstrated to be bactericidal against Staphylococcus aureus, an infectious microorganism that is highly relevant to implant-related infections. Film degradation products were generally nontoxic toward MC3T3-E1 osteoprogenitor cells. A reproducible in vivo rabbit bone infection model was developed to test the PEM coatings against sterile, uncoated placebos; subsequent in vivo experimentation demonstrated the proof-of-principle that an antibiotic-eluting LbL film can efficaciously treat a pre-existing implant-related infection. One further application was studied which combined the release-based mechanism of these erodible films with a permanent, contact-killing LbL film. This combination has the treatment benefit of an initial burst release of antibiotic, prevents biofilm formation, and reduces the probability of developing antibiotic resistance due to the prolonged presence of sublethal concentrations of gentamicin.by Joshua Seth Moskowitz.Ph.D
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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