Hakan Çiftçi

Glucose determination based on a two component self-assembled monolayer functionalized surface-enhanced Raman spectroscopy (SERS) probe

In this report, we present a new detection method for blood glucose, using gold nanorod SERS, a surface enhanced Raman scattering probe embedded in two component self-assembled monolayers (SAMs). Gold nanorod particles and a gold coated slide surface were modified with the two component SAMs consisting of 3-mercaptophenylboronic acid (3-MBA) and 1-decanethiol (1–DT). The immobilization of 3-MBA/1-DT surface-functionalized gold nanoparticles onto 3-MBA/1-DT modified gold-coated slide surfaces was achieved by the cooperation of hydrophobic forces. Two component SAM functionalized substrates were used as SERS probes, by means of the boronic acid and the alkyl spacer functional groups that serve as the molecular recognition and penetration agents, respectively. The SERS platform surface was characterized by cyclic voltammetry, contact angle measurements, AFM (atomic force microscopy) and Raman spectroscopy. Optimum values of the parameters such as pH, time and (3-MBA/1-DT) molar ratio were also examined for the glucose determination. The analytical performance was evaluated and linear calibration graphs were obtained in the glucose concentration range of 2–16 mM, which is also in the range of the blood glucose levels, and the detection limit was found to be 0.5 mM. As a result, the SERS platform was also used for the determination of glucose in plasma samples.

Electrochemical determination of iodide by poly(3-aminophenylboronic acid) film electrode at moderately low pH ranges

A new potentiometric sensor for the determination of iodide based on poly(3-aminophenylboronic acid) (PAPBA) film electrode was constructed. Poly(3-Aminophenylboronic acid) films were synthesized electrochemically on platinum electrode by cyclic voltammetry. The effect of film thickness, pH, and preconditioning parameters on the electrode performance were examined. The analytical performance was evaluated and linear calibration graphs were obtained in the concentration range of 10⁻⁶ to 10⁻¹ M iodide ion. The limit of detection was found to be 8×10⁻⁷ M. The response time of the sensor was 5 s and its lifetime is about one week. To check the selectivity of the PAPBA film for iodide ion, potential interferences such as Cl⁻, Br⁻, F⁻, CN⁻, IO₃⁻, Ca2+, and Mg2+ were tested. The PAPBA electrode was also employed as a sensing platform for the determination of iodide ions in commercial table salt.

Development of poly(3-aminophenylboronic acid) modified graphite rod electrode suitable for fluoride determination

Poly(3-aminophenylboronic acid), (PAPBA) film was formed on the graphite rod surface by potential cycling. The PAPBA-modified graphite rod (PAPBA/GR) electrode prepared in this way was used for potentiometric fluoride determination. The linear calibration range was from 5×10(-4) to 5×10(-2)M with the slope of the linear part of the calibration curve of 42.5mV/logC. No interference effect of the most common ions such as sodium, potassium, chloride, nitrate, iodide, calcium, zinc, aluminum, sulfate and sorbitol was observed during electrochemical determination of fluoride. On the other hand, the PAPBA/GR electrode showed not only good sensitivity and selectivity, but also relatively rapid response to changes of analyte concentrations in the range of 20s. The sensor was successfully applied for fluoride determination in real sample - toothpaste.

One step effective removal of Congo Red in chitosan nanoparticles by encapsulation

Chitosan nanoparticles (CNPs) were prepared with ionotropic gelation between chitosan and tripolyphosphate for the removal of Congo Red. The production of chitosan nanoparticles and the dye removal process was carried out in one-step. The removal efficiency of Congo Red by encapsulation within chitosan from the aqueous solution and its storage stability are examined at different pH values. The influence of some parameters such as the initial dye concentration, pH value of the dye solution, electrolyte concentration, tripolyphosphate concentration, mixing time and speed on the encapsulation is examined. Congo Red removal efficiency and encapsulation capacity of chitosan nanoparticles were determined as above 98% and 5107mg Congo Red/g chitosan, respectively.

Electrochemical biosensor based on glucose oxidase encapsulated within enzymatically synthesized poly(1,10-phenanthroline-5,6-dione).

This study is focused on the investigation of electrocatalytic effect of glucose oxidase (GOx) immobilized on the graphite rod (GR) electrode. The enzyme modified electrode was prepared by encapsulation of immobilized GOx within enzymatically formed poly(1,10-phenanthroline-5,6-dione) (pPD) film. The electrochemical responses of such enzymatic electrode (pPD/GOx/GR) vs. different glucose concentrations were examined chronoamperometrically in acetate-phosphate buffer solution (A-PBS), pH 6.0, under aerobic or anaerobic conditions. Amperometric signals of the pPD/GOx/GR electrode exhibited well-defined hyperbolic dependence upon glucose concentration. Amperometric signals at 100mM of glucose were 41.17 and 32.27 μA under aerobic and anaerobic conditions, respectively. Amperometric signals of the pPD/GOx/GR electrode decreased by 6% within seven days. The pPD/GOx/GR electrode showed excellent selectivity in the presence of dopamine and uric acid. Furthermore it had a good reproducibility and repeatability with standard deviation of 9.4% and 8.0%, respectively.

Ring opening polymerization of 2-aminothiazole with iron(III) chloride

Poly(2-aminothiazole), PAT, was synthesized by the chemical polymerization of 2-aminothiazole, AT, with FeCl3·6H2O in 1,4-dioxane. The effect of temperature, monomer, and initiator concentration and polymerization time on the rate of polymerization was studied. The structural analysis of the polymer was carried out by elemental analysis and 1H-NMR, FTIR, and UV–VIS spectroscopies. Thermal properties were studied by DSC and TGA. Conductivity measurements were carried out by four-probe technique and the number average molecular weight, Mn, of the polymer was determined by cryoscopy.

Preliminary study on heavy metal concentrations of Anatolian Khramulya, Capoeta tinca (Heckel, 1843) from Çamligöze Dam Lake, Sivas, Turkey

The concentrations of heavy metals (Ag, Cd, Co, Cu, Ni, Pb, Zn) were analyzed in muscle, skin and liver of Anatolian Khramulya, Capoeta tinca (Heckel, 1843) from Çamlıgöze Dam Lake located at Central Anatolian region of Turkey. The heavy metal analysis of samples was carried out by using a flame atomic absorption spectrophotometer. Ag, Cd, Co, Pb and Zn were found in all of the examined tissues. Cu and Ni were not determined in all tissues studied. The mean concentrations of heavy metals in all of the examined tissues of Capoeta tinca were as follows: Ag: 0.057 ± 0.038–0.120 ± 0.051, Cd: 0.020 ± 0.004–1.451 ± 0.879, Co: 0.127 ± 0.067–0.205 ± 0.086, Pb: 1.939 ± 0.477–2.604 ± 0.393 and Zn: 0.056 ± 0.014–0.530 ± 0.129 μg/g in Çamlıgöze Dam Lake. According to international criterias and Turkish regulation, heavy metal concentrations especially Cd and Pb in Çamlıgöze Dam Lake were found above the permissible levels for examined tissues of Capoeta tinca. Furthermore, frequent consumption of contaminated fish is able to offer a serious public health risk. Therefore, the concentrations of metals accumulated in the fish, which are commonly consumed by public, should be monitored periodically in Çamlıgöze Dam Lake.

Fabrication and characterization of gold-nanoparticles/chitosan film: a scaffold for L929-fibroblasts

Abstract The objective of the present study was to fabricate a gold nanoparticle crosslinked chitosan (Ch/AuNPs) composite film simple and to evaluate its use as a carrier matrix for L929- fibroblasts. L929- fibroblasts were seeded either onto Ch or Ch/AuNPs scaffolds. The Ch/AuNPs scaffold exhibited a higher cell proliferation and growth rate. The cytotoxicity test determined trypan blue staining indicated that Ch scaffolds devoid of AuNPs expressed almost no toxicity while the Ch/AuNPs composite scaffolds expressed a very limited toxicity only at higher doses. The Ch/AuNPs scaffold promotes cell attachment, growth and proliferation with almost no cytotoxicity.

Multiwalled Carbon Nanotube-Chitosan Scaffold: Cytotoxic, Apoptoti c, and Necrotic Effects on Chondrocyte Cell Lines

BACKGROUND Carbon nanotubes (CNTs) have been considered highly successful and proficient in terms of their mechanical, thermal and electrical functionalization and biocompatibility. In regards to their significant extent in bone regeneration, it has been determined that CNTs hold the capability to endure clinical applications through bone tissue engineering and orthopedic procedures. In the present study, we report on a composite preparation, involving the use of CNT-chitosan as scaffold for bone repair and regeneration. Through the use of water-soluble tetrazolium salt (WST-1) and double staining methods, the cytotoxic, necrotic, and apoptotic effects of chitosan-multiwalled carbon nanotube nanocomposites on the chondrocyte ATTC cell line have been exhibited. METHODS The chitosan-multiwalled carbon nanotube scaffolds were prepared. Chondrocytes differentiation tool (ATCC) cell line was prepared. WST-1 assay for cytotoxicity studies were performed by using chondrocytes cells in 12.5-200 μL concentration range. The samples of membranes (chitosan- multiwalled carbon nanotube scaffold) were measured at 2 mg/mL and further prepared amongst chitosan- multiwalled carbon nanotube scaffolds which were placed into separate wells. While in the process of incubation, in the four-hour time range, the plates were immediately read in an Elisa microplate Reader. To predict the number of apoptotic and necrotic cells in culture, the technique of double staining with Hoechst dye was performed with PI on the basis of scoring cell nuclei. The mechanical properties such as tensile strength and elongation at break values of the chitosan only and chitosan/CNT scaffolds were evaluated on Texture Analyzer. RESULTS Based on the results of the WST-1 assay procedure, the amount of cell viability was not significantly affected by nanocomposite concentrations and the lowest mortality rate of cells was obtained at a concentration of 12.5 μg/mL, whereas the highest mortality rate was obtained at a rate of 200 μg/mL. In addition, the effects of chitosan-CNT nanocomposites were not found to cytotoxic on chondrocyte cells. The double staining method has been able to determine the apoptotic and necrotic effects of chitosan MWCNT nanocomposites. The apoptotic and necrotic effects of the combined compounds had varied within the concentrations. In a similar manner to the outcome of the control groups, apoptosis was obtained at a percentage of 2.67%. Under a fluorescent inverted microscope, the apoptotic cell nuclei were stained with a stronger blue fluorescence in comparison to non-apoptotic cells, which may have had an effect. We also compared the strain-stress curve measurements results. The results indicated that the mechanical properties of scaffold were not different. Elongation at break values increased by addition of CNT. CONCLUSION CNTs as a biomaterial hold the potential to be used for applications in future regenerative medicine. By using the components of chondrocytes (ATTC) cell lines, the cytotoxicity evaluations were made for the chitosan-multiwalled carbon nanotube scaffold. The chitosan-MWCNT nanocomposites do not seem to induce drastic cytotoxicity to the chondrocyte cells.

Nanoparticle embedded chitosan film for agglomeration free TEM images

Transmission electron microscopy (TEM) is a very useful and commonly used microscopy technique, used especially for the characterization of nanoparticles. However, the identification of the magnetic nanoparticle could be thought problematic in TEM analysis, due to the fact that the magnetic nanoparticles are usually form aggregates on the TEM grid to form bigger particles generating higher stability. This prevents to see exact shape and size of each nanoparticle. In order to overcome this problem, a simple process for the formation of well‐dispersed nanoparticles was conducted, by covering chitosan film on the unmodified copper grid, it was said to result in aggregation‐free TEM images. It is also important to fix the magnetic nanoparticles on the TEM grids, due to possible contamination of TEM filament which is operated under high vacuum conditions. The chitosan film matrix also helps to protect the TEM filament from contact with magnetic nanoparticles during the imaging process. The proposed procedure offers a quick method to fix the nanoparticles in a conventional copper TEM grid and chitosan matrix prevents agglomeration of nanoparticles, and thus getting TEM images showing well‐dispersed individual nanoparticles.