Eylem Öztürk

Magnetic chitosan microspheres: preparation and characterization

Abstract In this study, magnetic chitosan microspheres were prepared in a well shaped spherical form with a size range of 100 to 250 μm (size distribution ±15 to ±40 μm, respectively) by the suspension cross-linking technique for use in the application of magnetic carrier technology. The magnetic material (i.e. Fe3O4) used in the preparation of the magnetic chitosan microspheres was prepared by precipitation from FeSO4 and Fe2(SO4)3 solutions in basic medium and then ground to the desired size (i.e. 1–5 μm). The morphological and magnetic properties of the microspheres were characterized by different techniques (i.e. SEM, optical microscopy, magnetometry). The results demonstrated that the stirring rate of the suspension medium and the Fe3O4/chitosan ratio are the most effective parameters for the size/size distribution and the magnetic quality of the microspheres, while the chitosan molecular weight (MW) has no significant effect on these properties for the given MW range (i.e. 150 to 650 kDa). The best magnetic quality of the magnetic chitosan microspheres is around 9.1 emu/g microsphere at 10 kG magnetic field intensity.

Preparation and characterization of polyethyleneglycolmethacrylate (PEGMA)-co-vinylimidazole (VI) microspheres to use in heavy metal removal.

Polyethyleneglycolmethacrylate (PEGMA) and vinylimidazole (VI) were used in order to obtain microspheres of PEGMA-VI copolymers that can be used in heavy metal removal applications. The obtained copolymers were characterized and their use as sorbents in heavy metal removal was investigated. In the first part of the study, PEGMA-VI microspheres were prepared by suspension polymerization method. The obtained swellable microspheres with 10-50 microm average diameter did not have permanent porosity according to the morphological and physicochemical determinations. The sizes of microspheres became smaller with increasing VI and cross-linker ethyleneglycoldimethacrylate (EGDMA) contents and increasing agitation rate. The VI content, EGDMA ratio, pH and ionic strength were determined as the effective parameters on the swelling behavior of PEGMA-VI microspheres. In the second part of the study, Cu(II) ions were used as a model species in order to investigate the usability of the obtained PEGMA-VI microspheres in heavy metal removal. Adsorption capacities under optimum conditions were determined. The Cu(II) ion adsorption capacity increased by increasing the initial Cu(II) ion concentration, and it reached the maximum value (i.e., 30 mg Cu(II)/g PEGMA-VI microspheres) at 400 mg Cu(II)/L initial Cu(II) ion concentration under the determined optimum conditions. Microspheres were found to be reusable after desorption for several times.

Norfloxacin-loaded Chitosan Sponges as Wound Dressing Material

The aim of this study was the preparation and characterization of chitosan sponges including a model antibiotic (i.e., norfloxacin). The chitosan sponges were prepared by a solvent evaporation method. The matrix was also cross-linked during the preparation. The results indicated that the chitosan sponges were in the fibrillar structure. The swelling behavior, norfloxacin loading, in vitro release characteristics, and antibacterial activity were determined. The effects of cross-linker concentration, norfloxacin/chitosan ratio, chitosan molecular weight, and base concentration were investigated. The most effective parameter was found to be the degree of neutralization. It was also observed that the equilibrium swelling ratio decreased with increasing crosslinking density. The norfloxacin release was found to be swelling controlled initially and diffusion controlled at the extended release periods. It was also found that the antibacterial activity was directly proportional to the release rate.

Antimicrobial activity of cefazolin-impregnated mesh grafts.

Background:  The aim of this study is the preparation and characterization of cefazolin‐impregnated meshes (Surgipro; Tyco Healthcare USSC, Norwalk, CT, USA) to be used as antimicrobial devices.

EGF Loaded Chitosan Sponges as Wound Dressing Material

The aim of this study was to prepare and characterize chitosan sponges using epidermal growth factor (EGF) for wound healing. Chitosan sponges were prepared by solvent evaporation (or precipitation) combined with chemical cross-linking techniques. The chitosan polymer was weighed and dissolved in aqueous acetic acid solution (5% v/v) and injected into absolute ethanol containing a cross-linker (ethylene glycol diglycydyl ether). The growth factor (EGF) was loaded into sponges by adding it into the chitosan solution. The EGF loaded chitosan sponges were used in fibroblast cell culture studies to investigate the effects of EGF released on cell proliferation and to determine the effects of the different variables on EGF release; such as, chitosan Mw, cross-linker, the needle injecting the chitosan solution into the precipitation medium, chitosan/EGF ratio and pH of the medium. The swelling of the sponges was higher in the lower molecular weight chitosan, with less cross-linker and using a small diameter injection needle. The swelling increased with decreasing chitosan/EGF ratio and the EGF release rate was increased by increasing the sponge swelling. The cell proliferation (cell growth) increased with increasing swelling ratio.

Bioadhesive Drug Carriers for Postoperative Chemotherapy in Bladder Cancer

Transurethral resection (TUR) is the primary mode of therapy for both diagnosis and treatment of bladder cancer. Due to the recurrency of tumoral tissues after TUR further treatment is necessary which is usually in the form of intravesical chemotherapy or immunotherapy. But these therapies have some disadvantages such as disturbancy to patients, adjustment of the suitable dosage, loss of active agents without using. In this study, an alternative approach was proposed and pharmaco-therapeutic agent delivery systems which will supply the suitable dosage of the agent for a certain time period were designed to solve those problems. For this aim, Mitomycin-C loaded alginate and chitosan carriers were prepared to use as an alternative system in the post-operative chemotherapy in bladder cancer. The carriers were prepared in the form of cylindirical geometries to facilitate the insertion of the carrier in in vivo studies. The effects of some parameters (i.e., polymer MW, cross-linker concentration, Mitomycin-C/polymer ratio etc.) over the morphology, swelling behavior, bioadhesion and in-vitro drug release rate of the carriers were evaluated. The obtained results for chitosan and alginate carriers were concluded comparatively.

Inhibition of Staphylococcus Epidermidis Colonization with Fusidic Acid-Impregnated Catheters

The aim of this study was the preparation and characterization of fusidic acid-impregnated peripheral catheters. In the first part of the study, in vitro drug release studies were performed, and the effect of fusidic acid impregnation on adherence of slime positive Staphylococcus epidermidis to catheters was evaluated as in vitro studies. Fusidic acid-impregnated and naïve catheters were incubated with 108 colony forming unit/mL (cfu/mL) slime positive S. epidermidis during the in vitro experiment. After incubation for 2, 4, 6, 8, 12, 24, 48, and 72 h, the number of colonies were determined in an aliquot and adhered to the catheter. During the in vivo experiment, contaminated naïve and fusidic acid-impregnated catheters (n = 10 rats in both groups) were implanted subcutaneously in the back of the rats. Rats were killed at the end of the seventh day and catheters were removed. Microbiologic assessments from the explanted catheter segments were performed. Fusidic acid impregnation decreased the number of adherent bacteria to the catheters and the number of free bacteria within the liquid medium significantly. There were 3 positive catheter cultures out of 10 in rats implanted with fusidic acid-impregnated catheters, whereas all explanted catheters from naïve group yielded bacterial growth. The mean cfu counts were significantly less in the fusidic acid-impregnated catheter group. In vitro release studies and antibacterial activity studies correlated well. Additionally, morphological evaluations by scanning electron microscopy showed that fewer bacteria were evident on the fusidic acid-impregnated catheters compared with naïve catheters. As a conclusion, catheter impregnation with fusidic acid is effective in preventing colonization in these in vitro and in vivo sets of experiments, with slime-producing S. epidermidis.

On Some Yamabe Type Equations

In this article we investigate the third type boundary value problem for a Yamabe Type Equation. We show that there exists a generalized solution of the considered problem. We also show the uniqueness of the solution of the considered problem in a special case.