Browsing by Subject "Glucose"

Now showing 1 - 9 of 9

Open Access
Biocatalytic protein membranes fabricated by electrospinning
(Elsevier B.V., 2016) Kabay, G.; Kaleli, G.; Sultanova, Z.; Ölmez, T. T.; Şeker, U. Ö. Ş.; Mutlu, M.
In this study, a protein-based catalytic membrane was produced by electrospinning. Membrane activity was characterised in terms of response current for various glucose concentrations. We focused on the preparation of a scaffold by converting a globular protein to other structural forms using catastrophic solvents. A scaffolding protein, bovine serum albumin, and an enzyme, glucose oxidase (GOD), were selected as a model natural carrier matrix and a biologically active agent, respectively. Beta-mercaptoethanol (β-ME) was used to convert the globular protein to an amyloid-like form. A structural stabilising agent, 2,2,2-triflouroethanol (TFE), was used to maintain the final α-helical structure of the amyloid-like protein. The TFE:PBS (phosphate-buffered saline) ratio and various electrospinning parameters were analysed to minimise activity loss. Using this approach, we applied electrospinning to an active enzyme to obtain biocatalytic nanofibrous membranes. After optimising the protein electrospinning process, the activities of the protein nanofibrous membranes were monitored. GOD remained active in the new membrane structure. The highest enzyme activity was observed for the membranes prepared with a 1.5:1 (v:v) TFE:PBS solvent ratio. In that particular case, the immobilized enzyme created a current of 0.7 μA and the apparent activity was 2547 ± 132 U/m2.
Open Access
Cellular internalization of therapeutic oligonucleotides by peptide amphiphile nanofibers and nanospheres
(American Chemical Society, 2016-04) Mumcuoglu, D.; S. Ekiz, M.; Gunay, G.; Tekinay, T.; Tekinay, A. B.; Güler, Mustafa O.
Oligonucleotides are promising drug candidates due to the exceptionally high specificity they exhibit toward their target DNA and RNA sequences. However, their poor pharmacokinetic and pharmacodynamic properties, in conjunction with problems associated with their internalization by cells, necessitates their delivery through specialized carrier systems for efficient therapy. Here, we investigate the effects of carrier morphology on the cellular internalization mechanisms of oligonucleotides by using self-assembled fibrous or spherical peptide nanostructures. Size and geometry were both found to be important parameters for the oligonucleotide internalization process; direct penetration was determined to be the major mechanism for the internalization of nanosphere carriers, whereas nanofibers were internalized by clathrin- and dynamin-dependent endocytosis pathways. We further showed that glucose conjugation to carrier nanosystems improved cellular internalization in cancer cells due to the enhanced glucose metabolism associated with oncogenesis, and the internalization of the glucose-conjugated peptide/oligonucleotide complexes was found to be dependent on glucose transporters present on the surface of the cell membrane.
Open Access
Glucose sensors based on electrospun nanofibers: a review
(Springer Verlag, 2016) Senthamizhan, A.; Balusamy, B.; Uyar, Tamer
The worldwide increase in the number of people suffering from diabetes has been the driving force for the development of glucose sensors. The recent past has devised various approaches to formulate glucose sensors using various nanostructure materials. This review presents a combined survey of these various approaches, with emphasis on the current progress in the use of electrospun nanofibers and their composites. Outstanding characteristics of electrospun nanofibers, including high surface area, porosity, flexibility, cost effectiveness, and portable nature, make them a good choice for sensor applications. Particularly, their nature of possessing a high surface area makes them the right fit for large immobilization sites, resulting in increased interaction with analytes. Thus, these electrospun nanofiber-based glucose sensors present a number of advantages, including increased life time, which is greatly needed for practical applications. Taking all these facts into consideration, we have highlighted the latest significant developments in the field of glucose sensors across diverse approaches.
Open Access
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.
Open Access
In situ synthesis of biomolecule encapsulated gold-cross-linked poly(ethylene glycol) nanocomposite as biosensing platform: A model study
(Elsevier BV, 2010) Odaci, D.; Kahveci, M.U.; Sahkulubey, E.L.; Ozdemir, C.; Uyar, Tamer; Timur, S.; Yagci Y.
In situ synthesis of poly(ethylene glycol) (PEG) hydrogels containing gold nanoparticles(AuNPs) and glucose oxidase (GOx) enzyme by photo-induced electron transfer process was reported here and applied in electrochemical glucose biosensing as the model system. Newly designed bionanocomposite matrix by simple one-step fabrication offered a good contact between the active site of the enzyme and AuNPs inside the network that caused the promotion in the electron transfer properties that was evidenced by cyclic voltammetryas well as higher amperometric biosensing responses in comparing with response signals obtained from the matrix without AuNPs. As well as some parameters important in the optimization studies such as optimum pH, enzyme loading and AuNP amount, the analytical characteristics of the biosensor (AuNP/GOx) were examined by the monitoring of chronoamperometric response due to the oxygen consumption through the enzymatic reaction at − 0.7 V under optimized conditions at sodium acetate buffer (50 mM, pH 4.0) and the linear graph was obtained in the range of 0.1–1.0 mM glucose. The detection limit (LOD) of the biosensor was calculated as 0.06 mM by using the signal to noise ratio of 3. Moreover, the presence of AuNPs was visualized by TEM. Finally, the biosensor was applied for glucose analysis for some beverages and obtained data were compared with HPLC as the reference method to test the possible matrix effect due to the nature of the samples.
Open Access
Platinum-palladium loaded polypyrrole film electrodes for the electrooxidation of D-glucose in neutral media
(Elsevier Sequoia SA, Lausanne, Switzerland, 1999) Becerik, İ.; Süzer, Ş.; Kadirgan, F.
Modified polymer films with metal particles incorporated into the films by electrodeposition are known as possible electrocatalysts for various electrode reactions such as fuel cell applications. This work presents some results concerning the electrooxidation of D-glucose at modified polymer film electrodes prepared on a platinum substrate. This reaction has a great deal of interest in view of its applications to detection systems (glucose sensor), fuel cells (pacemakers) and electroorganic systhesis. The modified polymer film electrodes contain platinum and/or palladium particles dispersed in the polypyrrole film by electrodeposition in neutral media. Addition of palladium to platinum modifies the electrocatalytic behaviour of the electrode drastically. The modification is thought to involve minimization of the poisoning of the catalyst, hence increasing its electrode activity.
Open Access
Presentation of functional groups on self-assembled supramolecular peptide nanofibers mimicking glycosaminoglycans for directed mesenchymal stem cell differentiation
(Royal Society of Chemistry, 2017) Yasa, Oncay; Uysal, Ozge; Ekiz, Melis Sardan; Güler, Mustafa O.; Tekinay, Ayse B.
Organizational complexity and functional diversity of the extracellular matrix regulate cellular behaviors. The extracellular matrix is composed of various proteins in the form of proteoglycans, glycoproteins, and nanofibers whose types and combinations change depending on the tissue type. Proteoglycans, which are proteins that are covalently attached to glycosaminoglycans, contribute to the complexity of the microenvironment of the cells. The sulfation degree of the glycosaminoglycans is an important and distinct feature at specific developmental stages and tissue types. Peptide amphiphile nanofibers can mimic natural glycosaminoglycans and/or proteoglycans, and they form a synthetic nanofibrous microenvironment where cells can proliferate and differentiate towards different lineages. In this study, peptide nanofibers were used to provide varying degrees of sulfonation mimicking the natural glycosaminoglycans by forming a microenvironment for the survival and differentiation of stem cells. The effects of glucose, carboxylate, and sulfonate groups on the peptide nanofibers were investigated by considering the changes in the differentiation profiles of rat mesenchymal stem cells in the absence of any specific differentiation inducers in the culture medium. The results showed that a higher sulfonate-to-glucose ratio is associated with adipogenic differentiation and a higher carboxylate-to-glucose ratio is associated with osteochondrogenic differentiation of the rat mesenchymal stem cells. Overall, these results demonstrate that supramolecular peptide nanosystems can be used to understand the fine-tunings of the extracellular matrix such as sulfation profile on specific cell types. © 2017 The Royal Society of Chemistry.
Open Access
Spatial organization of functional groups on bioactive supramolecular glycopeptide nanofibers for differentiation of mesenchymal stem cells (MSCs) to brown adipogenesis
(American Chemical Society, 2016-12) Caliskan, O. S.; Sardan, Ekiz M.; Tekinay, A. B.; Güler, Mustafa O.
Spatial organization of bioactive moieties in biological materials has significant impact on the function and efficiency of these systems. Here, we demonstrate the effect of spatial organization of functional groups including carboxylate, amine, and glucose functionalities by using self-assembled peptide amphiphile (PA) nanofibers as a bioactive scaffold. We show that presentation of bioactive groups on glycopeptide nanofibers affects mesenchymal stem cells (MSCs) in a distinct manner by means of adhesion, proliferation, and differentiation. Strikingly, when the glutamic acid is present in the glycopeptide backbone, the PA nanofibers specifically induced differentiation of MSCs into brown adipocytes in the absence of any differentiation medium as shown by lipid droplet accumulation and adipogenic gene marker expression analyses. This effect was not evident in the other glycopeptide nanofibers, which displayed the same functional groups but with different spatial organization. Brown adipocytes are attractive targets for obesity treatment and are found in trace amounts in adults, which also makes this specific glycopeptide nanofiber system an attractive tool to study molecular pathways of brown adipocyte formation.
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Synthesis of silica-based nanomaterials and their applications in fluorescent, biological and chemical sensing
(2018-06) Beyazkılıç, Pınar
This thesis describes development of nanoparticle-based liquid sensors and coatings for droplet-based bioassays. Liquid sensors were produced from mesostructured (2-50 nm) hybrid silica nanoparticles. Detection of trace trinitrotoluene (TNT) and dopamine in aqueous phase was shown based on uorescence of nanoparticles. Silica nanoparticles were synthesized using a facile one-pot solgel method. Pyrene molecules were hybridized with hydrophobic parts of cetyltrimethylammonium micelles followed by silica growth around micelles. Nanoparticles showed good dispersibility and colloidal stability in water. Pyrene exhibited bright and highly stable emission. Pyrene emission exhibited a rapid, sensitive and visual uorescence quenching against TNT and dopamine. For droplet-based assays, robust superhydrophilic patterned superhydrophobic coatings were developed. Biomolecular adsorption and droplet mixing were shown on coatings which were prepared using sol-gel method followed by ultraviolet/ ozone (UV/O) treatment. Droplet-based biomolecular detection platforms were developed using superhydrophilic patterned superhydrophobic surfaces. Bene tting from con nement and evaporation-induced shrinkage of droplets on wetted patterns, sensitive glucose and DNA detection was demonstrated. Glucose was detected based on enhancement of polydopamine (PDA) emission by hydrogen peroxide (H2O2) produced in glucose oxidation reaction. Detection in evaporating droplets resulted with bright uorescence and high sensitivity for analyte molecules. This was due to droplet evaporation which concentrated molecules and increased reaction rates. Surfaces and nanoparticles developed in this thesis hold great potential for biological and chemical analysis with low sample volumes owing to their simple production, sensitive detection responses and versatility.