Asli Celebioglu

Electrospinning of Polymer-free Nanofibers from Cyclodextrin Inclusion Complexes

The electrospinning of polymer-free nanofibers from highly concentrated (160%, w/v) aqueous solutions of hydroxypropyl-β-cyclodextrin (HPβCD) and its inclusion complexes with triclosan (HPβCD/triclosan-IC) was achieved successfully. The dynamic light scattering (DLS) and rheology measurements indicated that the presence of considerable HPβCD aggregates and the high solution viscosity were the key factors in obtaining electrospun HPβCD and HPβCD/triclosan-IC nanofibers without the use of any polymeric carrier. The HPβCD and HPβCD/triclosan-IC solutions containing 20% (w/w) urea yielded no fibers but only beads and splashes because of the depression of the self-aggregation of the HPβCD. The inclusion complexation of triclosan with HPβCD was studied by isothermal titration calorimetry (ITC) and turbidity measurements. The characteristics of the HPβCD and HPβCD/triclosan-IC nanofibers were investigated by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). It was found that the electrospinning of HPβCD/triclosan-IC solution having a 1:1 molar ratio was optimal for obtaining nanofibers without any uncomplexed guest molecules.

Drug delivery system based on cyclodextrin-naproxen inclusion complex incorporated in electrospun polycaprolactone nanofibers

In this study, we select naproxen (NAP) as a reference drug and electrospun poly (ɛ-caprolactone) (PCL) nanofibers as a fibrous matrix for our drug-delivery system. NAP was complexed with beta-cyclodextrin (βCD) to form inclusion complex (NAP-βCD-IC) and then NAP-βCD-IC was incorporated into PCL nanofibers via electrospinning. The incorporation of NAP without CD-IC into electrospun PCL was also carried out for a comparative study. Our aim is to analyze the release profiles of NAP from PCL/NAP and PCL/NAP-βCD-IC nanofibers and we investigate the effect of CD-IC on the release behavior of NAP from the nanofibrous PCL matrix. The characterization of NAP-βCD-IC and the presence of CD-IC in PCL/NAP-βCD-IC nanofibers were studied by FTIR, XRD, TGA, NMR and SEM. The SEM imaging of the electrospun PCL/NAP and PCL/NAP-βCD-IC nanofibers reveal that the average fiber diameter of these nanofibers is around 300nm, in addition, the aggregates of CD-IC in PCL/NAP-βCD-IC nanofibers is observed. The release study of NAP in buffer solution elucidate that the PCL/NAP-βCD-IC nanofibers have higher release amount of NAP than the PCL/NAP nanofibers due to the solubility enhancement of NAP by CD-IC.

Antibacterial electrospun nanofibers from triclosan/cyclodextrin inclusion complexes.

The electrospinning of nanofibers (NF) from cyclodextrin inclusion complexes (CD-IC) with an antibacterial agent (triclosan) was achieved without using any carrier polymeric matrix. Polymer-free triclosan/CD-IC NF were electrospun from highly concentrated (160% CD, w/w) aqueous triclosan/CD-IC suspension by using two types of chemically modified CD; hydroxypropyl-beta-cyclodextrin (HPβCD) and hydroxypropyl-gamma-cyclodextrin (HPγCD). The morphological characterization of the electrospun triclosan/CD-IC NF by SEM elucidated that the triclosan/HPβCD-IC NF and triclosan/HPγCD-IC NF were bead-free having average fiber diameter of 520 ± 250 nm and 1,100 ± 660 nm, respectively. The presence of triclosan and the formation of triclosan/CD-IC within the fiber structure were confirmed by (1)H-NMR, FTIR, XRD, DSC, and TGA studies. The initial 1:1 molar ratio of the triclosan:CD was kept for triclosan/HPβCD-IC NF after the electrospinning and whereas 0.7:1 molar ratio was observed for triclosan/HPγCD-IC NF and some uncomplexed triclosan was detected suggesting that the complexation efficiency of triclosan with HPγCD was lower than that of HPβCD. The antibacterial properties of triclosan/CD-IC NF were tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. It was observed that triclosan/HPβCD-IC NF and triclosan/HPγCD-IC NF showed better antibacterial activity against both bacteria compared to uncomplexed pure triclosan.

One-step synthesis of size-tunable Ag nanoparticles incorporated in electrospun PVA/cyclodextrin nanofibers

One-step synthesis of size-tunable silver nanoparticles (Ag-NP) incorporated into electrospun nanofibers was achieved. Initially, in situ reduction of silver salt (AgNO3) to Ag-NP was carried out in aqueous solution of polyvinyl alcohol (PVA). Here, PVA was used as reducing agent and stabilizing polymer as well as electrospinning polymeric matrix for the fabrication of PVA/Ag-NP nanofibers. Afterwards, hydroxypropyl-beta-cyclodextrin (HPβCD) was used as an additional reducing and stabilizing agent in order to control size and uniform dispersion of Ag-NP. The size of Ag-NP was ∼8 nm and some Ag-NP aggregates were observed for PVA/Ag-NP nanofibers, conversely, the size of Ag-NP decreased from ∼8 nm down to ∼2 nm within the fiber matrix without aggregation were attained for PVA/HPβCD nanofibers. The PVA/Ag-NP and PVA/HPβCD/Ag-NP nanofibers exhibited surface enhanced Raman scattering (SERS) effect. Moreover, antibacterial properties of PVA/Ag-NP and PVA/HPβCD/Ag-NP nanofibrous mats were tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria.

Electrospinning of nanofibers from non-polymeric systems: Electrospun nanofibers from native cyclodextrins

Electrospinning of nanofibers from non-polymeric systems is rather challenging, yet in this study, we have successfully performed electrospinning of nanofibers from two of the native cyclodextrins (CDs); α-CD and β-CD. Electrospinning was carried out for highly concentrated solutions of α-CD (120% up to 160%, w/v) and β-CD (120% up to 150%, w/v) in basic aqueous system. At optimal concentration level, the electrospinning of CD solutions yielded bead-free uniform CD nanofibers without using carrier polymeric matrix. Similar to polymeric systems, the electrospinning of CD solutions resulted in different morphologies and average fiber diameters depending on the CD type and CD concentration. The dynamic light scattering (DLS) and rheology measurements were performed in order to examine the electrospinnability of CD solutions. The existence of CD aggregates via hydrogen bonding and very high solution viscosity and viscoelastic solid-like behavior of CD solutions were found to be the key factors for obtaining bead-free nanofibers from CDs. The addition of urea disrupted CD aggregates and lowered the viscosity significantly, and therefore, the urea-added CD solutions yielded beaded fibers and/or beads. Although the as-received CDs in powder form are crystalline, the structural analyses by XRD and HR-TEM indicated that electrospun CD nanofibers have amorphous characteristic without showing any particular orientation or crystalline aggregation of CD molecules.

Highly Fluorescent Pyrene-Functional Polystyrene Copolymer Nanofibers for Enhanced Sensing Performance of TNT.

A pyrene-functional polystyrene copolymer was prepared via 1,3-dipolar cycloaddition reaction (Sharpless-type click recation) between azide-functional styrene copolymer and 1-ethynylpyrene. Subsequently, nanofibers of pyrene-functional polystyrene copolymer were obtained by using electrospinning technique. The nanofibers thus obtained, found to preserve their parent fluorescence nature, confirmed the avoidance of aggregation during fiber formation. The trace detection of trinitrotoluene (TNT) in water with a detection limit of 5 nM was demonstrated, which is much lower than the maximum allowable limit set by the U.S. Environmental Protection Agency. Interestingly, the sensing performance was found to be selective toward TNT in water, even in the presence of higher concentrations of toxic metal pollutants such as Cd(2+), Co(2+), Cu(2+), and Hg(2+). The enhanced sensing performance was found to be due to the enlarged contact area and intrinsic nanoporous fiber morphology. Effortlessly, the visual colorimetric sensing performance can be seen by naked eye with a color change in a response time of few seconds. Furthermore, vapor-phase detection of TNT was studied, and the results are discussed herein. In terms of practical application, electrospun nanofibrous web of pyrene-functional polystyrene copolymer has various salient features including flexibility, reproducibility, and ease of use, and visual outputs increase their value and add to their advantage.

Flexible and highly stable electrospun nanofibrous membrane incorporating gold nanoclusters as an efficient probe for visual colorimetric detection of Hg(II)

Here, we describe the visual colorimetric detection of Hg2+ based on a flexible fluorescent electrospun nanofibrous membrane (NFM). It is an efficient approach, in which we have effectively integrated fluorescent gold nanoclusters (AuNC) into electrospun polyvinyl alcohol nanofibers. Interestingly, the resulting composite nanofibers (AuNC*NFM) are shown to retain the fluorescence properties of AuNC and exhibit red fluorescence under UV light, being cogent criteria for the production of a visual colorimetric sensor. Furthermore, capabilities with regard to the stability of the AuNC*NFM have been under observation for a period of six months, with conditions matching those of typical atmosphere, and the resulting outcome has thrown light on their long-term storability and usability. It is clear, from the fact that the nanofibrous membrane preserves the fluorescence ability up to a temperature of 100 °C, that temperature does not have an effect on the sensing performance in real-time application. The water-insoluble AuNC*NFM have been successfully tailored by cross-linking with glutaraldehyde vapor. Further, the contact mode approach has been taken into consideration for the visual fluorescent response to Hg2+, and the observed change of color indicates the utility of the composite nanofibers for onsite detection of Hg2+ with a detection limit of 1 ppb. The selectivity of the AuNC*NFM hybrid system has been analyzed by its response to other common toxic metal interferences (Pb2+, Mn2+, Cu2+, Ni2+, Zn2+, Cd2+) in water. Several unique features of the hybrid system have been determined, including high stability, self-standing ability, naked-eye detection, selectivity, reproducibility and easy handling – setting a new trend in membrane-based sensor systems.

Molecular entrapment of volatile organic compounds (VOCs) by electrospun cyclodextrin nanofibers

In this paper, we reported the molecular entrapment performance of hydroxypropyl-beta-cyclodextrin (HPβCD) and hydroxypropyl-gamma-cyclodextrin (HPγCD) electrospun nanofibers (NF) for two common volatile organic compounds (VOCs); aniline and benzene. The encapsulation efficiency of CD samples were investigated depending on the various factors such as; CD form (NF and powder), electrospinning solvent (DMF and water), CD (HPβCD and HPγCD) and VOCs (aniline and benzene) types. BET analysis indicated that, electrospun CD NF have higher surface area compared to their powder form. In addition DMA measurement provided information about the mechanical properties of CD NF. The encapsulation capability of CD NF and CD powder was investigated by (1)H-NMR and HPLC techniques. The observed results suggested that, CD NF can entrap higher amount of VOCs from surroundings compared to their powder forms. Besides, molecular entrapment efficiency of CD NF also depends on CD, solvent and VOCs types. The inclusion complexation between CD and VOCs was determined by using TGA technique, from the higher decomposition temperature of VOCs. Finally, our results were fortified by the modeling studies which indicated the complexation efficiency variations between CD and VOC types. Here, the inclusion complexation ability of CD molecules was combined with very high surface area and versatile features of CD NF. So these findings revealed that, electrospun CD NF can serve as useful filtering material for air filtration purposes due to their molecular entrapment capability of VOCs.

Reusable bacteria immobilized electrospun nanofibrous webs for decolorization of methylene blue dye in wastewater treatment

In our study, an electrospun cellulose acetate nanofibrous web (CA-NFW) was found to be quite effective in immobilizing bacterial cells. Here, decolorization of methylene blue (MB) dye in aqueous medium was achieved by using three types of bacteria (Aeromonas eucrenophila, Clavibacter michiganensis and Pseudomonas aeruginosa) immobilized on the CA-NFW. The decolorization time (0–48 h) and different MB dye concentrations (20–500 mg L−1) were studied to elucidate the maximum MB dye removal by the bacteria immobilized CA-NFWs. The effective dye decolorization was achieved within 24 hours and MB dye removal was ∼95%. Interestingly, MB dye decolorization performance of bacteria immobilized CA-NFWs was quite close to that of free bacteria. We have also tested the reusability of bacteria immobilized NFWs after four cycles and ∼45% of the dye decolorization capacity was obtained at the end of the 4th cycle. These results are quite promising and therefore suggest that bacteria immobilized electrospun NFWs could be quite applicable for the decolorization of dyes in wastewater due to their versatility and reusability.

Surface modification of electrospun cellulose acetate nanofibers via RAFT polymerization for DNA adsorption

We report on a facile and robust method by which surface of electrospun cellulose acetate (CA) nanofibers can be chemically modified with cationic polymer brushes for DNA adsorption. The surface of CA nanofibers was functionalized by growing poly[(ar-vinylbenzyl)trimethylammonium chloride)] [poly(VBTAC)] brushes through a multi-step chemical sequence that ensures retention of mechanically robust nanofibers. Initially, the surface of the CA nanofibers was modified with RAFT chain transfer agent. Poly(VBTAC) brushes were then prepared via RAFT-mediated polymerization from the nanofiber surface. DNA adsorption capacity of CA nanofibrous web surface functionalized with cationic poly(VBTAC) brushes was demonstrated. The reusability of these webs was investigated by measuring the adsorption capacity for target DNA in a cyclic manner. In brief, CA nanofibers surface-modified with cationic polymer brushes can be suitable as membrane materials for filtration, purification, and/or separation processes for DNA.