High molecular weight polymers and high polymer concentrations are desirable for the electrospinning of nanofibers since polymer chain entanglements and overlapping are important for uniform fiber formation. Hence, the electrospinning of nanofibers from non-polymeric systems such as cyclodextrins (CDs) is quite a challenge since CDs are cyclic oligosaccharides. Nevertheless, in this study, we have successfully achieved the electrospinning of nanofibers from chemically modified CDs without using a carrier polymer matrix. Polymer-free nanofibers were electrospun from three different CD derivatives, hydroxypropyl-β-cyclodextrin (HPβCD), hydroxypropyl-γ-cyclodextrin (HPγCD) and methyl-β-cyclodextrin (MβCD) in three different solvent systems, water, dimethylformamide (DMF) and dimethylacetamide (DMAc). We observed that the electrospinning of these CDs is quite similar to polymeric systems in which the solvent type, the solution concentration and the solution conductivity are some of the key factors for obtaining uniform nanofibers. Dynamic light scattering (DLS) measurements indicated that the presence of considerable CD aggregates and the very high solution viscosity were playing a key role for attaining nanofibers from CD derivatives without the use of any polymeric carrier. The electrospinning of CD solutions containing urea yielded no fibers but only beads or splashes since urea caused a notable destruction of the self-associated CD aggregates in their concentrated solutions. The structural, thermal and mechanical characteristics of the CD nanofibers were also investigated. Although the CD derivatives are amorphous small molecules, interestingly, we observed that these electrospun CD nanofibers/nanowebs have shown some mechanical integrity by which they can be easily handled and folded as a free standing material.

We have demonstrated that cyclodextrin (CD) (a non-polymeric system) can be electrospun into nanofibers by itself; methyl-beta-cyclodextrin (MbetaCD) nanofibers were electrospun and it was observed that the success of the electrospinning of the CD nanofibers strongly depends on (i) type of solvent, (ii) CD solution concentration and (iii) intermolecular interactions between the CD molecules.

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.

a b s t r a c tBeta-cyclodextrin (␤-CD) functionalized cellulose acetate (CA) nanofibers have been successfully prepared by combining electrospinning and "click" reaction. Initially, ␤-CD and electrospun CA nanofibers were modified so as to be azide-␤-CD and propargyl-terminated CA nanofibers, respectively. Then, "click" reaction was performed between modified CD molecules and CA nanofibers to obtain permanent grafting of CDs onto nanofibers surface. It was observed from the SEM image that, while CA nanofibers have smooth surface, there were some irregularities and roughness at nanofibers morphology after the modification. Yet, the fibrous structure was still protected. ATR-FTIR and XPS revealed that, CD molecules were successfully grafted onto surface of CA nanofibers. The adsorption capacity of ␤-CD-functionalized CA (CA-CD) nanofibers was also determined by removing phenanthrene (polycyclic aromatic hydrocarbons, PAH) from its aqueous solution. Our results indicate that CA-CD nanofibers have potential to be used as molecular filters for the purpose of water purification and waste water treatment by integrating the high surface area of nanofibers with inclusion complexation property of CD molecules.

Vanillin/cyclodextrin inclusion complex nanofibers (vanillin/CD-IC NFs) were successfully obtained from three modified CD types (HPβCD, HPγCD and MβCD) in three different solvent systems (water, DMF and DMAc) via an electrospinning technique without using a carrier polymeric matrix. Vanillin/CD-IC NFs with uniform and bead-free fiber morphology were successfully produced and their free-standing nanofibrous webs were obtained. The polymer-free CD/vanillin-IC-NFs allow us to accomplish a much higher vanillin loading (∼12%, w/w) when compared to electrospun polymeric nanofibers containing CD/vanillin-IC (∼5%, w/w). Vanillin has a volatile nature yet, after electrospinning, a significant amount of vanillin was preserved due to complex formation depending on the CD types. Maximum preservation of vanillin was observed for vanillin/MβCD-IC NFs which is up to ∼85% w/w, besides, a considerable amount of vanillin (∼75% w/w) was also preserved for vanillin/HPβCD-IC NFs and vanillin/HPγCD-IC NFs. Phase solubility studies suggested a 1 : 1 molar complexation tendency between guest vanillin and host CD molecules. Molecular modelling studies and experimental findings revealed that vanillin : CD complexation was strongest for MβCD when compared to HPβCD and HPγCD in vanillin/CD-IC NFs. For vanillin/CD-IC NFs, water solubility and the antioxidant property of vanillin was improved significantly owing to inclusion complexation. In brief, polymer-free vanillin/CD-IC NFs are capable of incorporating a much higher loading of vanillin and effectively preserve volatile vanillin. Hence, encapsulation of volatile active agents such as flavor, fragrance and essential oils in electrospun polymer-free CD-IC NFs may have potential for food related applications by integrating the particularly large surface area of NFs with the non-toxic nature of CD and inclusion complexation benefits, such as high temperature stability, improved water solubility and an enhanced antioxidant property, etc.

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.

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.

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.