Browsing by Subject "Water-solubility"

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    Manganese doped fluorescent paramagnetic nanocrystals for dual-modal imaging
    (Wiley-VCH Verlag, 2014) Sharma, V. K.; Gokyar, S.; Kelestemur, Y.; Erdem, T.; Unal, E.; Demir, Hilmi Volkan
    In this work, dual-modal (fluorescence and magnetic resonance) imaging capabilities of water-soluble, low-toxicity, monodisperse Mn-doped ZnSe nanocrystals (NCs) with a size (6.5 nm) below the optimum kidney cutoff limit (10 nm) are reported. Synthesizing Mn-doped ZnSe NCs with varying Mn2+ concentrations, a systematic investigation of the optical properties of these NCs by using photoluminescence (PL) and time resolved fluorescence are demonstrated. The elemental properties of these NCs using X-ray photoelectron spectroscopy and inductive coupled plasma-mass spectroscopy confirming Mn2+ doping is confined to the core of these NCs are also presented. It is observed that with increasing Mn2+ concentration the PL intensity first increases, reaching a maximum at Mn2+ concentration of 3.2 at% (achieving a PL quantum yield (QY) of 37%), after which it starts to decrease. Here, this high-efficiency sample is demonstrated for applications in dual-modal imaging. These NCs are further made water-soluble by ligand exchange using 3-mercaptopropionic acid, preserving their PL QY as high as 18%. At the same time, these NCs exhibit high relaxivity (≈2.95 mM-1 s-1) to obtain MR contrast at 25°C, 3 T. Therefore, the Mn2+ doping in these water-soluble Cd-free NCs are sufficient to produce contrast for both fluorescence and magnetic resonance imaging techniques.
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    ItemOpen Access
    Menthol/cyclodextrin inclusion complex nanofibers: Enhanced water-solubility and high-temperature stability of menthol
    (Elsevier, 2018) Yildiz, Z. I.; Celebioglu A.; Kilic, M. E.; Durgun, Engin; Uyar, Tamer
    Cyclodextrins are capable of forming non-covalent host-guest inclusion complexation with variety of molecules in order to enhance water-solubility and thermal stability of such hydrophobic and volatile molecules. Menthol, an efficient antibacterial and flavour/fragrance agent, is used in various applications like food, pharmacy, cosmetics, however, its low water-solubility and high volatility somewhat limit its application. In this study, menthol/cyclodextrin-inclusion complex (menthol/CD-IC) was formed in highly concentrated aqueous solution by using hydroxypropyl-β-cyclodextrin (HPβCD) and hydroxypropyl-γ-cyclodextrin (HPγCD). The phase solubility studies and computational modeling studies revealed that menthol and these two CDs (HPβCD and HPγCD) formed stable inclusion complexes with the optimal molar ratio of 1:1 (menthol:CD) and inclusion complex formation enhanced the water-solubility of menthol. The electrospinning of nanofibers (NFs) from highly concentrated aqueous solutions (160%, w/v) of menthol/CD-IC was successfully performed without using additional fiber forming polymer and bead-free and uniform menthol/CD-IC NFs in the form of self-standing and flexible nanofibrous webs were produced. The initial molar ratio (1:1, menthol:CD) of the menthol/CD-IC in the solutions was mostly preserved in the menthol/CD-IC NFs (above 0.70:1.00, menthol:CD). The water-solubility of menthol was enhanced and menthol/CD-IC NFs have shown fast-dissolving character. The slow-release of menthol was achieved for menthol/CD-IC NFs, and the evaporation of menthol was shifted to much higher temperature (up to 275 °C) for menthol/CD-IC NFs which proved the high-temperature stability for menthol due to inclusion complexation.
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    ItemOpen Access
    Thymol/cyclodextrin inclusion complex nanofibrous webs: enhanced water solubility, high thermal stability and antioxidant property of thymol
    (Pergamon Press, 2018) Çelebioğlu, Aslı; Yıldız, Zehra İrem; Uyar, Tamer
    The development of novel nanomaterials that provide an efficient encapsulation and protection for the active food additives is one of the main focuses of current research efforts at food application areas. From this point of view, in this study, nanofibrous webs from inclusion complexes (IC) of modified cyclodextrins (hydroxypropyl-β-cyclodextrin (HPβCD), hydroxypropyl-γ-cyclodextrin (HPγCD) and methyl-β-cyclodextrin (MβCD)) and essential oils compound (i.e. thymol) was produced through electrospinning technique. While pure thymol has a highly volatile nature, the volatility of thymol was effectively suppressed by the inclusion complexation and ~ 88-100% (w/w) of thymol was preserved in electrospun thymol/cyclodextrin inclusion complex nanofibers (Thymol/CD-IC NF). The aqueous solubility enhancement for hydrophobic thymol was demonstrated by phase solubility diagram which also suggested the 1:1 M inclusion complexation between thymol and CD molecules. Besides, Thymol/CD-IC NF displayed quite fast disintegration in water compared to poorly water soluble thymol. By inclusion complexation, high temperature stability for volatile thymol was achieved for Thymol/CD-IC NF samples. The loading of thymol in Thymol/CD-IC NF conferred DPPH radical scavenging ability to these nanofibrous webs. So, the Thymol/CD-IC NF have shown antioxidant activity along with enhanced water solubility and high thermal stability of thymol. In brief, encapsulation of essential oil compounds such as thymol in electrospun CD-IC nanofibers can promote its potential application in food and oral-care products by associating the large surface area of nanofibrous webs along with CD inclusion complexation which provides enhanced water solubility and antioxidant property, and high temperature stability for thymol.