Tayfun Vural

Carbon nanotube–chitosan modified disposable pencil graphite electrode for Vitamin B12 analysis

A single walled carbon nanotube-chitosan (SWCNT-chitosan) modified disposable pencil graphite electrode (PGE) was used in this study for the electrochemical detection of Vitamin B(12). Electrochemical behaviors of SWCNT-chitosan PGE and chitosan modified PGE were compared by using cyclic voltammetry (CV), square-wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) techniques. SWCNT-chitosan modified electrode was also used for the quantification of Vitamin B(12) in pharmaceutical products. The results show that this electrode system is suitable for sensitive Vitamin B(12) analysis giving good recovery results. The surface morphologies of the SWCNT-chitosan PGE, chitosan modified PGE and unmodified PGE were characterized by using scanning electron microscopy (SEM).

In vitro S. epidermidis and S. aureus adherence to composite and lightweight polypropylene grafts.

BACKGROUND Despite the significant risk of infection, prosthetic graft materials have become indispensable for incisional hernia repair. Composite and lightweight grafts have been developed to overcome adhesion and rigidity. The aim of this study was to evaluate in vitro S. epidermidis and S. aureus adherence to these new generation grafts, which have modified composition and textile properties. MATERIALS AND METHODS In this experimental study, sterile samples of multifilament polypropylene, multifilament lightweight composite, monofilament composite, and monofilament polypropylene grafts were incubated with slime positive S. epidermidis and S. aureus strains for 24 h. The grafts were washed and vortexed in saline. The saline was passaged to blood agar and incubated for 24 h. The colonies were counted. Naïve and incubated graft materials were examined by scanning electron microscopy to reveal both textile properties and biofilm formation. Physicochemical properties were evaluated. Wilcoxon signed ranks test and Friedman test were used for statistical analysis. RESULTS S. epidermidis showed a significantly decreased adherence to monofilament polypropylene graft, and increased adherence to multifilament polypropylene graft (P<0.05). S. aureus showed a significant affinity for monofilament composite graft (P<0.05). SEM studies showed that biofilm formation was present on multifilament polypropylene graft. CONCLUSIONS Both S. epidermidis and S. aureus had significantly less adherence to multifilament lightweight composite than multifilament polypropylene graft. S. epidermidis showed a greater affinity to monofilament composite graft compared with monofilament polypropylene graft. Overall S. epidermidis adherence for multifilament lightweight composite and monofilament composite was less than multifilament polypropylene and higher than monofilament polypropylene. S. epidermidis and S. aureus showed different adherence for each graft. Changes in material composition and textile properties may well influence bacterial adherence.

Comparison of protein- and polysaccharide-based nanoparticles for cancer therapy: synthesis, characterization, drug release, and interaction with a breast cancer cell line

Abstract In this study, human serum albumin (HSA) was used as a protein-based material and poly (3-hydroxybutyrate) (PHB)–carboxymethyl chitosan (CMCh) as a polysaccharide-based material for the production of nanoparticles to be used as nanocarriers in cancer therapy. HSA and PHB–CMCh nanoparticles were prepared and characterized with a Zeta Sizer, Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscope. The effects of the pH value of the suspending medium and the amounts of crosslinker and polymer concentration on nanoparticle size and size distribution were investigated. The anticancer-agent etoposide was used as a model drug and encapsulated in nanoparticles to obtain drug release profiles. The entrapment efficiency of HSA nanoparticles was found to be greater than that of PHB–CMCh nanoparticles. To achieve “active” targeting of cancer cells, the nanoparticles were modified with concanavalin A. In the final step of the study, the interaction of nanoparticles with cancer cells was investigated in cytotoxicity and cellular uptake studies.

Electrochemical immunoassay for detection of prostate specific antigen based on peptide nanotube-gold nanoparticle-polyaniline immobilized pencil graphite electrode

In this work, we developed a disposable amperometric sandwich-type immunoassay to detect prostate specific antigen (PSA). A self-assembled peptide nanotube (PNT), gold nanoparticle (AuNP) and polyaniline (PANI) composite (PANI/AuNP-PNT) were used to modify a pencil graphite electrode (PGE). Anti-PSA (Ab1) was immobilized on the modified electrode (PANI/AuNP-PNT/PGE) to capture PSA. Horseradish peroxidase (HRP) labeled anti-PSA (HRP-Ab2) was used as a tracer antibody. The modified electrodes were characterized with scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). PSA concentration in phosphate buffer (pH=7.4) was determined with electro-catalytic reduction of H2O2 on the modified working electrode by using the chronoamperometric method. Limit of detection was found out to be 0.68ng/mL in a linear range of 1-100ng/mL with a high regression (R2=0.990). To show the practicality of the modified biosensor in real matrixes, it was successfully applied for the detection of PSA in blood serum samples. The proposed method was also compared with enzyme-linked immunosorbent assay (ELISA) and compatible results were obtained. The developed immunoassay exhibited good reproducibility together with high stability and provides an efficient approach to detect PSA cost-effectively compared to traditional methods.

Development of Titania Nanotube-based Electrochemical Immunosensor and Determination of Prostate Specific Antigen

Early diagnosis of cancer is the most important factor that increases the success of treatment. Therefore, the development of new diagnostic tools is a necessity. In this study, a new electrode surface was developed via modification of a disposable titanium electrode with anodic oxidation and coating of gold nanoparticle and chitosan. Titanium electrodes were anodized by several anodization parameters to obtain a nanoporous surface and characterized by scanning electron microscopy. Electrodes anodized in optimum conditions were modified with gold nanoparticles and chitosan for enhancing conductivity and functionalizing the surface of electrode, respectively. To detect prostate specific antigen (PSA), anti-PSA was bound onto the functional electrode surface. Modified electrodes were characterized with scanning electron microscopy and cyclic voltammetry and used for chronoamperometric detection of PSA. Limit of detection (LOD) of the designed electrode was found to be 7.8 ng mL-1 for PSA in a linear range of 0 - 100 ng mL-1.

The effect of the nanofilled adhesive systems on shear bond strength of all-ceramics to dentin

Aim: This study evaluated shear bond strength between three all-ceramic systems to dentin using six different adhesives, of which three of them contain nanofillers. Materials and Methods: Ceramic discs were prepared from each of Ceramco, IPS Empress 2 and Copran Zr. Different dentin surfaces were prepared with adhesives. Adper Single Bond Plus, Nano-bond, Prime & Bond NT (PB), Excite Bond, One Step Plus, Opti Bond Solo Plus were applied to the conditioned dentin surfaces. Ceramic discs were luted to the dentin with resin cement. All specimens were kept in water at 37°C for 1-week and thermal cycled for 500 cycles in 5°C and 55°C. Shearing test was conducted, and statistical analyses were performed using nonparametric tests (α = 0.05). Fractured surfaces of each specimen were inspected with Scanning Electron Microscope. Furthermore, distribution of nanofillers into the nanofilled adhesives was examined by transmission electron microscope. Results: Significant differences were observed in bond strength values of the adhesives (P < 0.05). For each ceramic, PB showed the highest bond strength values. Failure mode was cohesive in nanofilled adhesives resin and mixed failure for the others. Nanofillers were aggregated in some areas for each nanofilled adhesive. Ceramco showed the highest bond strength values while Copran Zr showed the lowest. Conclusion: Nanofilled adhesive systems would suggest for good clinical performance together with all-ceramics system. Furthermore, felspathic ceramics is better than the other all-ceramics systems.