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Öğe Hyaluronic acid (HA)-Gd(III) and HA-Fe(III) microgels as MRI contrast enhancing agents(Elsevier Ltd, 2022) Şahiner, Nurettin; Umut, Evrim; Sağbaş Suner, Selin; Şahiner, Mehtap; Culha, Mustafa; Ayyala, Ramesh S.Hyaluronic acid (HA) was crosslinked with Gd(III) and Fe(III) ions rendering physically crosslinked HA-metal(III) microgels as magnetic resonance imaging (MRI) enhancing contrast agents. These HA-Gd(III) and HA-Fe(III) microgels are injectable with size range, 50–5000 nm in water. The same isoelectric point, pH 1.2 ± 0.1, was measured for both microgels. HA-Gd(III) and HA-Fe(III) microgels are hemo-compatible biomaterials and can be safely used in intravascular applications up to 1000 μg/mL concentration. Furthermore, no significant toxicity was attained as 95 ± 8 and 81 ± 2% cell viability on L929 fibroblast cells at 100 μg/mL of HA-Gd(III) and HA-Fe(III) microgels were measured. Moreover, HA-Gd(III) microgels were found to afford significant contrast improvement capability in MRI with proton relaxivity, r1 = 2.11 mM−1 s−1, comparable with the values reported for Gd(III) labeled functionalized HA gel systems and commercial Gd based contrast agents.Öğe Enhanced enzymatic activity and stability by in situ entrapment of α Glucosidase within super porous p(HEMA) cryogels during synthesis(Elsevier B.V., 2020) Demirci, Şahin; Şahiner, Mehtap; Yılmaz, Selehattin; Karadağ, Erdener; Şahiner, NurettinHere, poly(2-hydroxyethyl methacrylate) (p(HEMA)) cryogel were prepared in the presence 0.48, 0.96, and 1.92 mL of α-Glucosidase enzyme (0.06 Units/mL) solutions to obtain enzyme entrapped superporous p(HEMA) cryogels, donated as α-Glucosidase@p(HEMA)-1, α-Glucosidase@p(HEMA)-2, and α-Glucosidase@p(HEMA)-3, respectively. The enzyme entrapped p(HEMA) cryogels revealed no interruption for hemolysis and coagulation of blood rendering viable biomedical application in blood contacting applications. The α-Glucosidase@p(HEMA)-1 was found to preserve its’ activity% 92.3 ± 1.4 % and higher activity% against free α-Glucosidase enzymes in 15–60℃ temperature, and 4–9 pH range. The Km and Vmax values of α-Glucosidase@p(HEMA)-1 cryogel was calculated as 3.22 mM, and 0.0048 mM/min, respectively versus 1.97 mM, and 0.0032 mM/min, for free enzymes. The α-Glucosidase@p(HEMA)-1 cryogel was found to maintained enzymatic activity more than 50 % after 10 consecutive uses, and also preserved their activity more than 50 % after 10 days of storage at 25 ℃, whereas free α-Glucosidase enzyme maintained only 1.9 ± 0.9 % activity under the same conditions.Öğe Biomedical applications of nanofibers(wiley, 2022) Şahiner, Mehtap; Kurt, Saliha B.; Şahiner, NurettinElectrospinning is one of the most convenient and effective techniques in the production of fibers that employs high voltage. The tunable parameters of the electrospinning technique, e.g. flow rate of the polymer solution, voltage, distance between needle and the collector, and viscosity of polymer solution, allow fibers with different sizes and characteristics to be produced, i.e. micro-to nanosized fibers with different types and extent of porosity. Electrospun fibers are well suited for a broad range of applications including environmental, energy, biotechnology, health care, and biomedical applications. Recently, electrospun fibers have attracted great interest for drug delivery, wound healing, and biosensor applications in the biomedical field. The electrospinning technique is attractive due to its simplicity and low cost and is widely employed in both academia and industry. In this chapter, the utilization of the electrospinning technique in the fabrication of nanofibers from various natural and synthetic polymers and their biomedical applications will be discussed. © 2022 John Wiley & Sons, Inc.Öğe Hydrolytic nondegradable bioactive rosmarinic acid particles(John Wiley and Sons Ltd, 2021) Şahiner, MehtapRosmarinic acid (RS) is as the nonflavonoid polyphenols in the phenolic acid subgroup was cross-linked with sodium trimetaphosphate (STMP) to obtain (p[RS-co-STMP]) particles with the size distribution of 2.992 ± 659 nm. The zeta potential values of p(RS-co-STMP) particles were measured between pH 2–10, and the isoelectric point was determined as pH 2.66. Fe(II) chelating capability test was done for RS and p(RS-co-STMP). At 800 μmol/ml concentrations, p(RS-co-STMP) particles chelated 95.06 ± 5.18% Fe(II), while RS molecule did not chelate Fe(II), whereas STMP chelated only 41.8 ± 5.9% Fe(II). The effects of RS and p(RS-co-STMP) particles on α-glucosidase enzyme activity were investigated and were found to inhibit the α-glucosidase enzyme by 55.7% and 89.6%, respectively. Furthermore, p(RS-co-STMP) particles were modified with polyethyleneimine as m-p(RS-co-STMP) to improve antimicrobial properties and found effective against both Escherichia coli and Staphylococcus aureus bacteria. The interaction of fibrinogen with RS, p(RS-co-STMP) and m-p(RS-co-STMP) were studied via the change in intensity of corresponding fluorescence spectra. It was found that p(RS-co-STMP) particles interacted lesser with fibrinogen than RS and changed the fluorescence property of fibrinogen protein slightly. On the other hand, m-p(RS-co-STMP) particles did not change the fluorescence intensity of fibrinogen suggesting no influence on the blood clotting.Öğe Chondroitin Sulfate-Based Cryogels for Biomedical Applications(MDPI, 2021) Demirci, Şahin; Şahiner, Mehtap; Ari, Betül; Sunol, Aydın K.; Şahiner, NurettinCryogels attained from natural materials offer exceptional properties in applications such as tissue engineering. Moreover, Halloysite Nanotubes (HNT) at 1:0.5 weight ratio were embedded into CS cryogels to render additional biomedical properties. The hemolysis index of CS cryogel and CS:HNT cryogels was calculated as 0.77 ± 0.41 and 0.81 ± 0.24 and defined as non-hemolytic mate-rials. However, the blood coagulation indices of CS cryogel and CS:HNT cryogels were determined as 76 ± 2% and 68 ± 3%, suggesting a mild blood clotting capability. The maximum% swelling capacity of CS cryogel was measured as 3587 ± 186%, 4014 ± 184%, and 3984 ± 113%, at pH 1.0, pH 7.4 and pH 9.0, respectively, which were reduced to 1961 ± 288%, 2816 ± 192, 2405 ± 73%, respectively, for CS:HNT cryogel. It was found that CS cryogels can hydrolytically be degraded 41 ± 1% (by wt) in 16-day incubation, whereas the CS:HNT cryogels degraded by 30 ± 1 wt %. There is no chelation for HNT and 67.5 ± 1% Cu(II) chelation for linear CS was measured. On the other hand, the CS cryogel and CS:HNT cryogel revealed Cu(II) chelating capabilities of 60.1 ± 12.5%, and 43.2 ± 17.5%, respectively, from 0.1 mg/mL Cu(II) ion stock solution. Additionally, at 0.5 mg/mL CS, CS:HNT, and HNT, the Fe(II) chelation capacity of 99.7 ± 0.6, 86.2 ± 4.7% and only 11.9 ± 4.5% were measured, respectively, while no Fe(II) was chelated by linear CS chelated Fe(II). As the adjustable and con-trollable swelling properties of cryogels are important parameters in biomedical applications, the swelling properties of CS cryogels, at different solution pHs, e.g., at the solution pHs of 1.0, 7.4 and 9.0, were measured as 3587 ± 186%, 4014 ± 184%, and 3984 ± 113%, respectively, and the maximum selling% values of CS:HNT cryogels were determined as 1961 ± 288%, 2816 ± 192, 2405 ± 73%, re-spectively, at the same conditions. Alpha glucosidase enzyme interactions were investigated and found that CS-based cryogels can stimulate this enzyme at any CS formulation.Öğe Rod-like L-Aspartic acid-Cu(II) metal organic frameworks; Synthesis, characterization and biomedical properties(Elsevier B.V., 2021) Gizer, Görkem; Şahiner, Mehtap; Yıldırım, Yıldız; Demirci, Şahin; Can, Mehmet; Şahiner, NurettinL-aspartic acid (L-AA) based MOFs were prepared from acetate, chloride, nitrate, and sulfate salts of Cu(II) ions as L-AA-Cu(II)-A,-C,-N,-S, respectively with 96.7 2.4, 89.8 3.1, 92.1 1.5, 74.6 5.2 m2/g, surface areas. L-AA- Cu(II)-MOFs in the same order induced 0.43 0.25%, 0.94 0.24%, 0.91 0.40%, 1.18 0.10% hemolysis, all being <2%, and blood clotting indices of ~90% and can be considered nonhemolytic and non-coagulative at 1 μg/mL concentration. L-AA-Cu(II)-A MOFs exhibited 86.3 0.2, and 92.4 0.6% α-Glucosidase inhibitory ac- tivities at 1.0 and 10.0 μg/mL concentrations, respectively. Moreover, L-AA-Cu(II)-S MOFs had effective anti- microbial activities against E. coli (ATCC-8739), and S. aureus (ATCC-6538) with MIC values of 0.63 mg/mL and 1.25 mg/mL for C. albicans (ATCC-10231). L-AA-Cu(II) MOFs synthesized herein with hemocompatible, antimi- crobial and antidiabetic properties prompt interesting possibilities for both industrial and biomedical applicationsÖğe Biodiverse Properties of Tannic Acid-Based Fibers(Springer, 2021) Şahiner, Mehtap; Kurt, Saliha B.; Şahiner, NurettinTannic acid (TA) is a plant-based polyphenolic molecule with enticing anti-oxidant, anti-bacterial, antiinflammatory and anti-cancer features, making it a valuable material in bio-medicinal applications. To establish whether TA-based fibers are useful tools in potential medical textiles, e.g., as wound dressing material for prophylaxis against infections and diseases, TA fibers were prepared and employed in biological assays. TA fibers were prepared with 55 weight% TA in ethanol-DI water mixture and fabricated by the electrospinning technique. Bare TA-based fibers were examined and were 1.2 +/- 0.1 % non-hemolytic and had 8.7 +/- 1.7 blood clotting index up to 2 mg/ml concentration. Degradation of bare TA-based fibers was completed in 5 minutes; however, degradation of crosslinked TA-based fibers were 98.3 +/- 2.3 % and 83.1 +/- 5.4 % for TA-Ibu and TA in 168 hours. Anti-oxidant activity of TA-based fibers was investigated by TEAC, total phenol content (TPC) and total flavonoid content (TFC) assays. Bare TA fibers possessed the highest anti-oxidant activity of 5.7 +/- 0.5 mM trolox equivalent/g, 168.0 +/- 2.0 gallic acid equivalent mu g/ml and 193.0 +/- 17.0 quercetin equivalent mu g/ml. Anti-bacterial activity was investigated by the disc diffusion method and the highest inhibition zone diameter was measured as 3.5 +/- 0.2 cm against S. aureus (gram +) bacteria; however, the same fiber was detected as producing 2.2 +/- 0.5 cm zone diameter for E. coli (gram -) bacteria.
