Browsing by Subject "Magnetic Resonance Spectroscopy"

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    Drug delivery system based on cyclodextrin-naproxen inclusion complex incorporated in electrospun polycaprolactone nanofibers
    (Elsevier, 2014) Canbolat, M. F.; Celebioglu A.; Uyar, Tamer
    In this study, we select naproxen (NAP) as a reference drug and electrospun poly (e-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 300. nm, 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.
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    Fast-dissolving, prolonged release, and antibacterial cyclodextrin/limonene-inclusion complex nanofibrous webs via polymer-free electrospinning
    (American Chemical Society, 2016) Aytac Z.; Yildiz, Z. I.; Kayaci-Senirmak, F.; S. Keskin, N. O.; Kusku, S. I.; Durgun, Engin; Tekinay, T.; Uyar, Tamer
    We have proposed a new strategy for preparing free-standing nanofibrous webs from an inclusion complex (IC) of a well-known flavor/fragrance compound (limonene) with three modified cyclodextrins (HPβCD, MβCD, and HPγCD) via electrospinning (CD/limonene-IC-NFs) without using a polymeric matrix. The experimental and computational modeling studies proved that the stoichiometry of the complexes was 1:1 for CD/limonene systems. MβCD/limonene-IC-NF released much more limonene at 37, 50, and 75 °C than HPβCD/limonene-IC-NF and HPγCD/limonene-IC-NF because of the greater amount of preserved limonene. Moreover, MβCD/limonene-IC-NF has released only 25% (w/w) of its limonene, whereas HPβCD/limonene-IC-NF and HPγCD/limonene-IC-NF released 51 and 88% (w/w) of their limonene in 100 days, respectively. CD/limonene-IC-NFs exhibited high antibacterial activity against E. coli and S. aureus. The water solubility of limonene increased significantly and CD/limonene-IC-NFs were dissolved in water in a few seconds. In brief, CD/limonene-IC-NFs with fast-dissolving character enhanced the thermal stability and prolonged the shelf life along with antibacterial properties could be quite applicable in food and oral care applications.
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    High-resolution magic anglespinning ¹H nuclear magnetic resonance spectroscopy metabolomics of hyperfunctioning parathyroid glands
    (Mosby, Inc., 2016) Battini, S.; Imperiale, A.; Taïeb, D.; Elbayed, K.; Cicek, A. E.; Sebag, F.; Brunaud, L.; Namer, Izzie-Jacques
    Background Primary hyperparathyroidism (PHPT) may be related to a single gland disease or multiglandular disease, which requires specific treatments. At present, an operation is the only curative treatment for PHPT. Currently, there are no biomarkers available to identify these 2 entities (single vs. multiple gland disease). The aims of the present study were to compare (1) the tissue metabolomics profiles between PHPT and renal hyperparathyroidism (secondary and tertiary) and (2) single gland disease with multiglandular disease in PHPT using metabolomics analysis. Methods The method used was 1H high-resolution magic angle spinning nuclear magnetic resonance spectroscopy. Forty-three samples from 32 patients suffering from hyperparathyroidism were included in this study. Results Significant differences in the metabolomics profile were assessed according to PHPT and renal hyperparathyroidism. A bicomponent orthogonal partial least square-discriminant analysis showed a clear distinction between PHPT and renal hyperparathyroidism (R2Y = 0.85, Q2 = 0.63). Interestingly, the model also distinguished single gland disease from multiglandular disease (R2Y = 0.96, Q2 = 0.55). A network analysis was also performed using the Algorithm to Determine Expected Metabolite Level Alterations Using Mutual Information (ADEMA). Single gland disease was accurately predicted by ADEMA and was associated with higher levels of phosphorylcholine, choline, glycerophosphocholine, fumarate, succinate, lactate, glucose, glutamine, and ascorbate compared with multiglandular disease. Conclusion This study shows for the first time that 1H high-resolution magic angle spinning nuclear magnetic resonance spectroscopy is a reliable and fast technique to distinguish single gland disease from multiglandular disease in patients with PHPT. The potential use of this method as an intraoperative tool requires specific further studies.
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    Monitoring and correcting spatio-temporal variations of the MR scanner’s static magnetic field
    (Springer, 2006) El-Sharkawy, A. M.; Schär, M.; Bottomley, P. A.; Atalar, Ergin
    The homogeneity and stability of the static magnetic field are of paramount importance to the accuracy of MR procedures that are sensitive to phase errors and magnetic field inhomogeneity. It is shown that intense gradient utilization in clinical horizontal-bore superconducting MR scanners of three different vendors results in main magnetic fields that vary on a long time scale both spatially and temporally by amounts of order 0.8-2.5 ppm. The observed spatial changes have linear and quadratic variations that are strongest along the z direction. It is shown that the effect of such variations is of sufficient magnitude to completely obfuscate thermal phase shifts measured by proton-resonance frequency-shift MR thermometry and certainly affect accuracy. In addition, field variations cause signal loss and line-broadening in MR spectroscopy, as exemplified by a fourfold line-broadening of metabolites over the course of a 45 min human brain study. The field variations are consistent with resistive heating of the magnet structures. It is concluded that correction strategies are required to compensate for these spatial and temporal field drifts for phase-sensitive MR protocols. It is demonstrated that serial field mapping and phased difference imaging correction protocols can substantially compensate for the drift effects observed in the MR thermometry and spectroscopy experiments.
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    Perisylvian GABA levels in schizophrenia and bipolar disorder
    (Elsevier Ireland Ltd, 2017) Atagün, M. İ.; Şıkoglu, M. E.; Soykan, Ç.; Can, S. S.; Ulusoy-Kaymak S.; Çayköylü, A.; Algın O.; Phillips, M. L.; Öngür, D.; Moore, C. M.
    The aim of this study is to measure GABA levels of perisylvian cortices in schizophrenia and bipolar disorder patients, using proton magnetic resonance spectroscopy (1H-MRS). Patients with schizophrenia (n = 25), bipolar I disorder (BD-I; n = 28) and bipolar II disorder (BD-II; n = 20) were compared with healthy controls (n = 30).1H-MRS data was acquired using a Siemens 3 T whole body scanner to quantify right and left perisylvian structures’ (including superior temporal lobes) GABA levels. Right perisylvian GABA values differed significantly between groups [χ2= 9.62, df: 3, p = 0.022]. GABA levels were significantly higher in the schizophrenia group compared with the healthy control group (p = 0.002). Furthermore, Chlorpromazine equivalent doses of antipsychotics correlated with right hemisphere GABA levels (r2= 0.68, p = 0.006, n = 33). GABA levels are elevated in the right hemisphere in patients with schizophrenia in comparison to bipolar disorder and healthy controls. The balance between excitatory and inhibitory controls over the cortical circuits may have direct relationship with GABAergic functions in auditory cortices. In addition, GABA levels may be altered by brain regions of interest, psychotropic medications, and clinical stage in schizophrenia and bipolar disorder. � 2016 Elsevier Ireland Ltd
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    Polymer-free nanofibers from vanillin/cyclodextrin inclusion complexes: high thermal stability, enhanced solubility and antioxidant property
    (Royal Society of Chemistry, 2016) Celebioglu A.; Kayaci-Senirmak, F.; Ipek, S.; Durgun, Engin; Uyar, Tamer
    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.