Nalan Oya San Keskin

Electrospinning of polymer-free cyclodextrin/geraniol–inclusion complex nanofibers: enhanced shelf-life of geraniol with antibacterial and antioxidant properties

Free-standing nanofibrous webs of cyclodextrin/geraniol–inclusion complex (CD/geraniol–IC-NF) showing antibacterial, antioxidant activity and slow release of geraniol were developed as flavour/fragrance releasing materials via electrospinning. The electrospinning of CD/geraniol–IC-NFs with uniform and bead-free morphology was achieved without using a polymer matrix. Three types of CDs modified with hydroxypropyl and methyl groups (HPβCD, MβCD, and HPγCD) were used to obtain CD/geraniol–IC-NFs. The polymer-free CD/geraniol–IC-NFs allow us to attain much higher geraniol loading (∼11%, w/w) when compared to electrospun polymeric nanofibers containing CD/geraniol–IC (∼5%, w/w). Geraniol has a volatile nature, yet, a significant amount of geraniol (∼60–90%) was preserved in CD/geraniol–IC-NFs due to the complexation, whereas evaporation of geraniol was unavoidable for polymeric nanofibers incorporating geraniol without cyclodextrin. Short-term (3 h) temperature dependent release (37 °C, 50 °C, and 75 °C) and long-term open air (50 days, at RT) release tests revealed that MβCD/geraniol–IC-NF released less geraniol compared to HPβCD/geraniol–IC-NF and HPγCD/geraniol–IC-NF, indicating that much stronger inclusion complexation was formed between MβCD and geraniol. The release of geraniol from CD/geraniol–IC-NFs prevented the colonization of Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria to a great extent, as observed in the antibacterial activity results. It was observed that CD/geraniol–IC-NFs had higher antioxidant activity compared to pure geraniol due to the solubility increase. In brief, the results reported here may open a new door to enhance the performance of essential oils and flavour/fragrances, to preserve volatile compounds from evaporation and to better understand the potential of CD/IC-NFs as carrier systems for guest compounds in the food, cosmetic and household cleaning industries.

Removal of a reactive dye and hexavalent chromium by a reusable bacteria attached electrospun nanofibrous web

A contaminant resistant Lysinibacillus sp. NOSK was isolated from a soil sample and its Reactive Black 5 (RB5) and Cr(VI) removal efficiencies were investigated as a function of changes in the initial pH values, temperature, static/shaking conditions, reactive dye and Cr(VI) concentrations. In this study, an electrospun polysulfone nanofibrous web (PSU-NFW) was found to be effective in attachment of bacterial cells. Bacteria attached PSU-NFWs (bacteria/PSU-NFW) have shown highly efficient removal of RB5, as 99.7 ± 0.9% and 35.8 ± 0.4% for the pristine PSU-NFW. Moreover, the highest Cr(VI) removal efficiencies measured were 98.2 ± 0.6% for bacteria attached PSU-NFW and 32.6 ± 0.6% for the pristine PSU-NFW. Simultaneous removal of RB5 and Cr(VI) were also investigated. Reusability test results indicate that, bacteria/PSU-NFW can be reused for at least 7 cycles with 28.1 ± 0.6% and 66.7 ± 0.8% removal efficiencies for RB5 and Cr(VI), respectively.

Bacteria encapsulated electrospun nanofibrous webs for remediation of methylene blue dye in water

In this study, preparation and application of novel biocomposite materials that were produced by encapsulation of bacterial cells within electrospun nanofibrous webs are described. A commercial strain of Pseudomonas aeruginosa which has methylene blue (MB) dye remediation capability was selected for encapsulation, and polyvinyl alcohol (PVA) and polyethylene oxide (PEO) were selected as the polymer matrices for the electrospinning of bacteria encapsulated nanofibrous webs. Encapsulation of bacterial cells was monitored by scanning electron microscopy (SEM) and fluorescence microscopy, and the viability of encapsulated bacteria was checked by live/dead staining and viable cell counting assay. Both bacteria/PVA and bacteria/PEO webs have shown a great potential for remediation of MB, yet bacteria/PEO web has shown higher removal performances than bacteria/PVA web, which was probably due to the differences in the initial viable bacterial cells for those two samples. The bacteria encapsulated electrospun nanofibrous webs were stored at 4°C for three months and they were found as potentially storable for keeping encapsulated bacterial cells alive. Overall, the results suggest that electrospun nanofibrous webs are suitable platforms for preservation of living bacterial cells and they can be used directly as a starting inoculum for bioremediation of water systems.

Encapsulation of Living Bacteria in Electrospun Cyclodextrin Ultrathin Fibers for Bioremediation of Heavy Metals and Reactive Dye from Wastewater

Cyclodextrins (CD) are cyclic oligosaccharides produced from the enzymatic degradation of starch as a white powder form; on the other hand, they can be transformed into ultrathin electrospun fiber form by electrospinning technique. The electrospun cyclodextrin fibers (CD-F) can be quite attractive materials to encapsulate bacteria for bioremediation purposes. For instance, CD-F not only serve as a carrier matrix but also it serves as a feeding source for the encapsulated bacteria. In the present study, we demonstrate a facile approach by encapsulation of bacteria into CD-F matrix for wastewater treatment application. The natural and non-toxic properties of CD-F render a better bacterial viability for fibrous biocomposite. The encapsulated bacteria in CD-F exhibit cell viability for more than 7days at 4°C storage condition. Furthermore, we have tested the bioremediation capability of bacteria/CD-F biocomposite for the treatment of heavy metals (Nickel(II) and Chromium(VI)) and textile dye (Reactive Black 5, RB5). The bacteria/CD-F biocomposite has shown removal efficiency of Ni(II), Cr(VI) and RB5 as 70±0.2%, 58±1.4% and 82±0.8, respectively. As anticipated, the pollutants removal capabilities of the bacteria/CD-F was higher compare to free bacteria since bacteria can use CD as an extra carbon source which promotes their growth rate. This study demonstrates that CD-F are suitable platforms for the encapsulation of bacterial cells to develop novel biocomposites that have bioremediation capabilities for wastewater treatment.

Green Synthesis of Silver Nanoparticles Using Cyanobacteria and Evaluation of their Photocatalytic and Antimicrobial Activity

Nowadays, green and efficient synthetic strategies have been gaining great interest for the synthesis of nanoparticles. In this study, the biosynthesis of silver nanoparticles and its photocatalytic activity for photodegradation of organic dye and antimicrobial property was studied. The initial syntheses of Ag nanoparticles were characterized by UV–Vis spectrophotometer and showed the surface plasmon resonance band at 430-450 nm. Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) study showed evidence that proteins are possible reducing agents. The structure of AgNPs was determined by Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). SEM and TEM studies revealed the synthesized AgNPs to be spherical. The AgNPs exhibited photocatalytic activity for photodegradation of organic dye such as Methylene Blue. Approximately 18% degradations of methylene blue within 4 h was observed with biosynthesized Ag nanoparticles in the photocatalytic degradation process.

Synthesis and in vitro antimicrobial characterization of Boron-PVA Electrospun nanofibers

Abstract Polyvinyl alcohol (PVA) electrospun nanofibers and boric acid (BA) complexes of these nanofibers were synthesized with and without using TritonX-100(TX-100) as a water soluble surfactant (PVA, PVA/BA, PVA/TX-100, PVA/TX-100/BA). The electrospun nanofibers were characterized by SEM, FTIR and TGA. Preliminary results showed that certain amount of boric acid decreased the number of Stapylococcus aureus from 6,8x107(CFU/mL) to 3x107(CFU/mL). In the preparation of polymer, boric acid was used as a crosslinker and antimicrobial agent whereas TX-100 was used as surfactant. The viscosity and conductivity measurements indicated that the BA increased viscosity but decreased conductivity. In contrast, TX-100 increased conductivity without considerable effect on viscosity, which affects the production and resulting nanofiber properties such as diameter and bead formation. The antimicrobial activities of the nanofibers were assayed in vitro by Gram-negative (E. coli) and Gram-positive(S. aureus) bacteria. It was observed that PVA/TX-100/BA showed better antibacterial activity against S.aureus bacteria compared to PVA and PVA/TX-100 nanofibers.