341 research outputs found
Electrospun polylactic acid/date palm polyphenol extract nanofibres for tissue engineering applications
In this study, a set of polylactic acid (PLA)/polyphenol extracted from date palm fruit (DP) blends were prepared by electrospinning process to be used as cell culture scaffolds for tissue engineering applications. For this purpose, PLA/DP blends with variable composition were dissolved in dichloromethane/dimethylformamide (70:30, v/v) mixture and then electrospun to obtain the fibres. Contact angle measurements, dynamic mechanical analysis, mechanical tensile and scanning electron microscopy (SEM) tools were used to study the physico-mechanical properties of the electrospun scaffolds. The results revealed that scaffolds became more hydrophilic with addition of DP. Increasing the polyphenol concentration caused the tensile strength and Young's modulus to decrease. The SEM graphs indicated a decrease in fibre diameter with increasing DP content. In addition, it was found that both cell proliferation and cell viability were enhanced with increased DP concentration within the scaffolds. The scratch test shows that there is an enhancement in cell migration through the scratch for PLA/DP scaffolds; again, higher DP content resulted better migration. Our results suggest that improved mechanical properties, decreased fibre diameter and enhanced hydrophilicity with addition of DP improved cell migration and cell adhesion for the scaffolds. Overall, these results demonstrate that DP is a potential natural cell-friendly product for tissue engineering applications such as tissue regeneration or wound healing assays
Glycogen and gold nanoparticle bioconjugates: controlled plasmon resonance via glycogen-induced nanoparticle aggregation
Hybrid nanosystems composed of glycogen biopolymers and gold nanoparticles were prepared by an in situ non-toxic synthetic procedure. Transmission electron microscopy (TEM) and various spectroscopic methods (optical absorption, X-ray photoelectron and photoluminescence spectroscopy) were used for the characterization of the obtained bioconjugates. The gold nanoparticles formed in the presence of glycogen were spherical in shape and approximately 15 nm in diameter. The TEM micrographs show that the nanoparticles aggregated on the surface of the glycogen biomolecules. This effect induced a shift of the surface plasmon resonance band towards higher wavelengths on an increase in gold ion concentration. Effective medium theory calculations were carried out in order to explain the observed redshift of the plasmon band in the absorption spectra of the Au-glycogen colloids. The interactions of the gold nanoparticles with glycogen strongly affected the photoluminescence of the glycogenin protein incorporated into its structure. The Au-glycogen hydrocolloids exhibited good chemical stability in the presence of saline, phosphate buffered saline, alanine, histidine and D-glucose
Synthesis, characterization, and antimicrobial properties of novel double layer nanocomposite electrospun fibers for wound dressing applications
Herein, novel hybrid nanomaterials were developed for wound dressing applications with antimicrobial properties. Electrospinning was used to fabricate a double layer nanocomposite nanofibrous mat consisting of an upper layer of poly(vinyl alcohol) and chitosan loaded with silver nanoparticles (AgNPs) and a lower layer of polyethylene oxide (PEO) or polyvinylpyr- rolidone (PVP) nanofibers loaded with chlorhexidine (as an antiseptic). The top layer containing AgNPs, whose purpose was to protect the wound site against environmental germ invasion, was prepared by reducing silver nitrate to its nanoparticulate form through interaction with chitosan. The lower layer, which would be in direct contact with the injured site, contained the antibi- otic drug needed to avoid wound infections which would otherwise interfere with the healing process. Initially, the upper layer was electrospun, followed sequentially by electrospinning the second layer, creating a bilayer nanofibrous mat. The morphology of the nanofibrous mats was studied by scanning electron microscopy and transmission electron microscopy, showing successful nanofiber production. X-ray diffraction confirmed the reduction of silver nitrate to AgNPs. Fourier transform infrared spectroscopy showed a successful incorporation of the material used in the produced nanofibrous mats. Thermal studies carried out by thermogravi- metric analysis indicated that the PVP–drug-loaded layer had the highest thermal stability in comparison to other fabricated nanofibrous mats. Antimicrobial activities of the as-synthesized nanofibrous mats against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans were determined using disk diffusion method. The results indicated that the PEO–drug-loaded mat had the highest antibacterial activity, warranting further attention for numerous wound-healing applications.QUST-CAS-SPR-14\15-
Reactivity of (1-methoxycarbonylpentadienyl)iron(1+) cations with hydride, methyl, and nitrogen nucleophiles
The reaction of tricarbonyl and (dicarbonyl)triphenylphosphine (1-methoxycarbonyl-pentadientyl)iron(1+) cations 7 and 8 with methyl lithium, NaBH3CN, or potassium phthalimide affords (pentenediyl)iron complexes 9a-c and 11a-b, while reaction with dimethylcuprate, gave (E,Z-diene)iron complexes 10 and 12. Oxidatively induced-reductive elimination of 9a-c gave vinylcyclopropanecarboxylates 17a-c. The optically active vinylcyclopropane (+)-17a, prepared from (1S)-7, undergoes olefin cross-metathesis with excess (+)-18 to yield (+)-19, a C9C16 synthon for the antifungal agent ambruticin. Alternatively reaction of 7 with methanesulfonamide or trimethylsilylazide gave (E,E-diene)iron complexes 14d and e. Huisgen [3 + 2] cyclization of the (azidodienyl)iron complex 14e with alkynes afforded triazoles 25a-e
Effect of synthetic antioxidants on the oxidative stability of biodiesel
Biodiesels were prepared using base catalyzed methanolysis of sunflower, soybean and canola oils.
Rancimat oxidative stability measurements showed that the induction period (IP) for neat canola biodiesel
conformed to EN 14214, the European specification for biodiesel (IP > 6 h). Stability was enhanced
when 0.5 wt.% of the synthetic antioxidants di-tert-butylhydroquinone (DTBHQ) or poly(1,2-dihydro-
2,2,4-trimethylquinoline) (Orox PK) was added. Soybean-based biodiesel spiked with 0.5 wt.% DTBHQ
also reached this specification. Orox PK improved the stability of sunflower biodiesel but the 3 h induction
period specified by ASTM D-6751 could not be reached. Curiously, canola biodiesel was destabilized
on adding the antioxidant Naugard P (tris(nonylphenyl) phosphite).The Institutional Research
Development Programme (IRDP) and the THRIP program
of the Department of Trade and Industry and the National Research
Foundation of South Africa, Ltd as well as Xyris Technology.http://www.elsevier.com/locate/fuelai201
Variants of the EAAT2 Glutamate Transporter Gene Promoter Are Associated with Cerebral Palsy in Preterm Infants
© 2017, The Author(s). Preterm delivery is associated with neurodevelopmental impairment caused by environmental and genetic factors. Dysfunction of the excitatory amino acid transporter 2 (EAAT2) and the resultant impaired glutamate uptake can lead to neurological disorders. In this study, we investigated the role of single nucleotide polymorphisms (SNPs; g.-200CCloseSPigtSPiA and g.-181ACloseSPigtSPiC) in the EAAT2 promoter in susceptibility to brain injury and neurodisability in very preterm infants born at or before 32-week gestation. DNA isolated from newborns’ dried blood spots were used for pyrosequencing to detect both SNPs. Association between EAAT2 genotypes and cerebral palsy, cystic periventricular leukomalacia and a low developmental score was then assessed. The two SNPs were concordant in 89.4% of infants resulting in three common genotypes all carrying two C and two A alleles in different combinations. However, in 10.6% of cases, non-concordance was found, generating six additional rare genotypes. The A alleles at both loci appeared to be detrimental and consequently, the risk of developing cerebral palsy increased four- and sixfold for each additional detrimental allele at -200 and -181bp, respectively. The two SNPs altered the regulation of the EAAT2 promoter activity and glutamate homeostasis. This study highlights the significance of glutamate in the pathogenesis of preterm brain injury and subsequent development of cerebral palsy and neurodevelopmental disabilities. Furthermore, the described EAAT2 SNPs may be an early biomarker of vulnerability to neurodisability and may aid the development of targeted treatment strategies
Ambivalence toward men: comparing sexism among Polish, South African and British university students
This study extends the literature on attitudes toward gender roles by exploring whether the nature of sexism (i.e., benevolence and hostility directed at men) differs among university students from two under-researched countries, Poland (n = 190) and South Africa (n = 188), in a comparison with students in the United Kingdom (n = 166). Based on empirical literature applying Ambivalent Sexism Theory, and in the light of the socio-political context, it was hypothesized that: (1) both hostile and benevolent attitudes toward men in Poland would be more liberal than in South Africa and more conservative than in the United Kingdom, and (2), women would exhibit more hostile but less benevolent attitudes than men in relatively more conservative South Africa. The Ambivalence to Men Inventory was used to measure the two types of sexist attitudes about men. Findings supported the first hypothesis for hostile attitudes and partially for benevolent attitudes. South African and Polish students were more benevolent and hostile to men than British students, and students from South Africa were more hostile than those from Poland. Moreover, as predicted, a significant country-by-gender interaction revealed that South African women had more hostile and less benevolent attitudes to men than South African men. No such gender gap was present in the case of hostile attitudes in Poland and benevolent attitudes in the United Kingdom. Findings are discussed in terms of Ambivalent Sexism Theory and the countries’ socio-cultural context
A framework for mixing methods in quantitative measurement development, validation, and revision: A case study
A framework for quantitative measurement development, validation, and revision that incorporates both qualitative and quantitative methods is introduced. It extends and adapts Adcock and Collier’s work, and thus, facilitates understanding of quantitative measurement development, validation, and revision as an integrated and cyclical set of procedures best achieved through mixed methods research. It also offers a systematic guide concerning how these procedures may be undertaken through detailing key “stages,” “levels,” and practical “tasks.” A case study illustrates how qualitative and quantitative methods may be mixed through the use of the proposed framework in the cross-cultural content- and construct-related validation and subsequent revision of a quantitative measure.The contribution of this article to mixed methods research literature is briefly discussed
Evaluation of AllergiSense smartphone tools for adrenaline injection training
© 2015 IEEE. Anaphylaxis is an increasingly prevalent life-threatening allergic condition that requires people with anaphylaxis and their caregivers to be trained in the avoidance of allergen triggers and in the administration of adrenaline auto-injectors. The prompt and correct administration of auto-injectors in the event of an anaphylactic reaction is a significant challenge in the management of anaphylaxis. Unfortunately, many people do not know how to use auto-injectors and either fail to use them or fail to use them correctly. This is due in part to deficiencies in training and also to the lack of a system encouraging continuous practice with feedback. Assistive smartphone healthcare technologies have demonstrated potential to support the management of chronic conditions such as diabetes and cardiovascular disease, but there have been deficiencies in their evaluation and there has been a lack of application to anaphylaxis. This paper describes AllergiSense, a smartphone app and sensing system for anaphylaxis management, and presents the results of a randomized, controlled, pre-post evaluation of AllergiSense injection training and feedback tools with healthy participants. Participants whose training was supplemented with AllergiSense injection feedback achieved significantly better practiced injections with 90.5% performing correct injections compared to only 28.6% in the paper-only control group. In addition, the results provide insights into possible self-efficacy failings in traditional training and the benefits of embedding self-efficacy theory into the technology design process
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