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Öğe A novel biosensing system based on ITO-single use electrode for highly sensitive analysis of VEGF(Taylor & Francis Ltd, 2020) Akgun, Mert; Kemal Sezginturk, MustafaNowadays, breast cancer is one of the riskiest and common cancer types. The early diagnosis of breast cancer is very important just as in other cancer types. Recent investigations demonstrate the biomarkers can be useful for the disease phase. These biomarkers are the very important materials to determine the good or bad diagnostic of the patient. Vascular endothelial growth factor is considered the most powerful mitogen for endothelial cells and also is an important regulator of vascular permeability and angiogenesis. In the frame of this study, it is purposed to design an electrochemical immunosensor system based on indium-tin oxide covered polyethylene terephthalate electrode. Electrochemical impedance spectroscopy, which is a quick and sensitive method, was used for vascular endothelial growth factor determination. Electrochemical impedance spectroscopy and cyclic voltammetry techniques were used in all optimisation processes of the produced biosensor. Scanning electron microscopy images, energy-dispersive X-ray spectra and mapping, atomic force microscopy and infrared spectra were examined to support the optimisation studies and to reveal surface morphology and chemical components. In the electrochemical characterisation studies, repeatability, reproducibility, storage, regeneration, single frequency impedance, square wave voltammetry and Kramer's-Kronig transform studies were performed. The measurements were taken in human serum.Öğe Cinnamaldehyde-poly (lactic acid)/gelatin nanofibers exhibiting antibacterial and antibiofilm activity(Taylor & Francis Ltd, 2024) Akpinar, Zeynep; Ulusoy, Seyhan; Akgun, Mert; Oral, Ayhan; Suner, Salih CanBacterial infections and biofilms are known to impede the wound-healing process. Naturally derived compounds from plants hold promise in inhibiting or preventing bacterial biofilms, with cinnamaldehyde (CA) being recognized for its antibacterial and antibiofilm properties. In this investigation, three-dimensional, antibacterial, and biodegradable nanofibers were synthesized via electrospinning, employing FDA-approved polylactic acid (PLA), gelatin (Gel), and the phytoactive molecule cinnamaldehyde (CA). The cinnamaldehyde content, morphology, and physical as well as biological characteristics of the electrospun PLA-Gel-CA nanofibers were scrutinized using HPLC, SEM, TGA, and FTIR analysis. The antibacterial activity of the PLA-Gel-CA nanofibers against Staphylococcus aureus and Pseudomonas aeruginosa, along with their antibiofilm activity against P. aeruginosa, were evaluated. The average diameters of PLA-Gel-CA nanofibers, specifically PLA-Gel-CA1, PLA-Gel-CA2, and PLA-Gel-CA3, were determined to be 294.9 +/- 46.8 nm, 254 +/- 58.3 nm, and 728.5 +/- 98.3 nm, respectively. PLA-Gel-CA3 nanofibers demonstrated notable antibacterial efficacy against S. aureus (31.0 +/- 1.20 mm) and P. aeruginosa (16.0 +/- 1.20 mm), along with a significant inhibition of P. aeruginosa biofilm formation by 72.2%. These findings indicate the potential of cinnamaldehyde-loaded nanofibers for wound application owing to their antibacterial and antibiofilm activity, as well as their rapid dissolution characteristics.Öğe Geraniol and cinnamaldehyde as natural antibacterial additives for poly(lactic acid) and their plasticizing effects(Walter De Gruyter Gmbh, 2020) Akgun, Mert; Basaran, Ihsan; Suner, Salih C.; Oral, AyhanThe main goal of this study is to prepare antibacterial poly(lactic acid) (PLA) containing cinnamaldehyde and geraniol and to evaluate the antibacterial activity and assess the changes of physical properties of the PLA films. Cinnamaldehyde- and geraniol-incorporated (10%, 20%, 30%, and 50% v/w) PLA films were prepared via solution-casting. While preparing these films, plasticizers were not added to the matrix. Antibacterial activities of these films against Escherichia coli and Staphylococcus aureus were investigated by the disk diffusion method. Thermal degradation characteristics were analyzed via thermogravimetric analysis (TGA), glass transition, crystallization, and melting temperatures, and enthalpies of the films were determined from differential scanning calorimetry (DSC) scans. Tensile strength and elongationat-break values of neat PLA and antibacterial-compound-containing films were evaluated and compared after the mechanical tests. Moreover, the changes in the polymer morphology were observed by SEM analysis, and opacity of the films was determined by UV-vis spectroscopy. Our results showed that both compounds provided antibacterial effect to the PLA, with cinnamaldehyde being more effective than geraniol. Moreover, plasticization effects of the compounds were confirmed by DSC analysis.Öğe Solar light driven photochromic membranes with viologen additives in PVDF/PVP matrix(Frontiers Media Sa, 2024) Tohtayeva, Jahan; Altinisik, Sinem; Akgun, Mert; Nigiz, Filiz Ugur; Koyuncu, SermetThis study explores the synthesis and characterization of photochromic Polyvinylidenefluoride/Polyvinylpyrrolidone (PVDF/PVP)-based membranes, prepared through an in situ thiol-ene click reaction by incorporating viologen derivatives with different counter ions. Viologens are well-known for their light-sensitive properties and ability to change color, making them useful in various optoelectronic applications. The membranes developed in this study exhibit significant improvements in their interactions with light as a result of improved morphology and enhanced ionic conductivity (approximate to 4 x 10-4 S cm-1) with higher porosity (Ra: 11.26-33.76 nm) compared to conventionally prepared membranes. These membranes show the ability to block almost all ultraviolet (UV) and a 90% of visible light after irradiation. Thanks to these properties, the membranes undergo visible color changes when exposed to sunlight, making them suitable for photochromic and thermochromic applications. The findings of this study could contribute to the development of innovative coating materials that enhance energy efficiency, potentially being applied to buildings, automotive windows, and other surfaces.
