Cyclodextrin functionalized nanofibers via electrospinning
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Electrospinning is a commonly studied and widely applied technique for generating nanofibers, with a diameter ranging from several tens of nanometers to a few micrometers. The low-cost, simple set-up, relatively high production rate and reproducibility increase the interests on this method in both academia and industry. Electrospun nanofibers are produced from a broad range of materials with extremely high surface area, very light-weight, nano-porous features and distinct physical/mechanical properties. The general talk in this technique focuses on the production of nanofibers from polymer base materials. However, very recent studies demonstrated that, it is also possible to obtain nanofibers from non-polymeric systems. For this novel development in electrospinning researches, we have achieved to generate nanofibers from cyclodextrins (CD) without using a polymeric template. CD are cyclic oligosaccharides consisting of α-(1,4)-linked glucopyranose units. The truncated cone shape structure of CD provides a favorable place for various kinds of organic molecules to form non-covalent host-guest inclusion complexes (IC). The enhancements and progressing at the guest molecules property and situation, creating with the inclusion complexation, make CD applicable in variety of areas including filtration, pharmaceuticals, cosmetics, functional foods, textiles, analytic chemistry etc. In this thesis, we report on the electrospinning of CD nanofibers, represent their functionalization and potential applications. Firstly, we produced CD nanofibers from three different chemically modified CD types (hydroxypropyl-β-cyclodextrin (HPβCD), hydroxypropyl-γ-cyclodextrin (HPγCD) and methyl-β-cyclodextrin (MβCD)). Afterwards, the electrospinning of native CD (α-CD, β-CD and γ-CD) nanofibers was achieved. The molecular entrapment capability of CD nanofibers was shown by capturing toxic volatile organic compounds (VOCs) from the surrounding. As the next step, the polymer-free nanofibers were obtained from the cyclodextrin inclusion complexes (CD-IC) with antibacterial agent, vanillin and essential oils. Here, we have also indicated applicability of CD-IC nanofibers as a result of antibacterial test. The functionalization of the CD nanofibers was continued with the green and one-step synthesis of metal nanoparticles (Ag-NP, Au-NP and Pd-NP) incorporated nanofibers, in which CD were used as reducing, stabilizing agent and fiber template. Even, the antibacterial, SERS and catalyst potential of these CD based nanofibers were demonstrated for the related nanoparticles. Our research is expanded to a new stage by the production of insoluble poly-CD nanofibers. We have worked on different crosslinking agents to attain insoluble poly-CD nanofibers with uniform morphology. After the optimization of poly-CD nanofibers, the most durable polyCD nanowebs were selected for further analysis and evaluation of the filtration performance in liquid environment. Within poly-CD nanofibers, we have eliminated the solubility challenge of CD nanofibers that restrict their usage. So, we assume that, poly-CD nanofibers will lead-up to generation of new advances for practices of CD nanofibers. All studies showed that, the self-assembly and self-aggregation property of CD are the prior requirements for the electrospinnability of these small molecules. To conclude, very intriguing materials were obtained by integrating large surface area of nanofibers with specific host-guest inclusion complexation capability and non-toxic, biocompatible nature of the CD. Moreover, CD molecules, which are generally used in the powder form, were rendered into more applicable nanofibers form that will represent ease during their usage.
KeywordsElectrospinning, Cyclodextrin, Nanofibers, İnclusion Complex, Antibacterial Agent, Vanillin, Essential Oils, Nanoparticles, Silver, Gold, Palladium, Molecular Encapsulation, Antibacterial Activity, SERS, Catalyst, Crosslinking