Browsing by Author "Karatas, Erkan"

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Antibacterial Activity and Cytotoxicity of Bioinspired Poly (L-Dopa) Silver Nanostructure-Decorated Titanium Dioxide Nanowires
(Elsevier, 2022) Serginay, Nuray; Dizaji, Araz Norouz; Mazlumoglu, Hayrunnisa; Karatas, Erkan; Yilmaz, Asli; Yilmaz, Mehmet
The combination of silver (Ag) and titanium dioxide (TiO2) nanostructures offer unique advantages in terms of elimination of infection and enhanced antibacterial activity with relatively higher biocompatibility and lower cytotoxicity. Although there have been numerous attempts for the fabrication of these nanocomposite systems, novel, flexible, low-cost, simple, effective, reducing, and stabilizing agent-free strategies are highly required for biomedical applications. Within this context, we report the employment of silver nanostructure decorated TiO2 nanowires (TiO2 NWs) as an ideal antibacterial agent against antibiotic-resistant Gram-negative (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus). Firstly, TiO2 NWs were fabricated via the hydrothermal procedure. Afterward, by utilizing the oxidative polymerization of 3,4-dihydroxyphenyl-L-alanine (L-DOPA), a conformal and thin polymer layer of L-DOPA (PLDP) was created onto the TiO2 NWs (TiO2/PLDP). Lastly, Ag nanostructures were deposited onto the TiO2/PLDP (TiO2/PLDP/Ag NP) via simply reduction of silver ions. Herein, PLDP with its abundant catechol and amine groups played an important role in the reduction of silver ions and the adsorption of Ag nanostructures with high affinity and resultant stability. The size, density, and morphology of Ag nanostructures were manipulated by tuning the initial amount of Ag ions in a well-controlled manner. The resultant colloidal TiO2/PLDP/Ag composite nanosystem provided remarkably high and stable antibacterial activity against both antibiotic-resistant bacteria strains. Minimum Inhibitory Concentration (MIC) values were found to be 125, 250, and > 500 ppm for high, medium and, low deposition of Ag nanostructures, respectively. Similarly, Minimum Bactericidal Concentration (MBC) for these NP systems, MBC values were found to be 250, 500, and > 1000 ppm, respectively. Also, relatively lower cytotoxicity in human lung healthy (MRC5) and cancer (A549) cell lines was detected in a dose-dependent manner in comparison to the citrate-stabilized Ag nanoparticles. The proposed novel TiO2/PLDP/Ag nanosystem will provide unique opportunities in terms of flexibility, low-cost, simplicity with reducing, and stabilizing agent-free strategy and be employed in the removal of biofilms and anti-inflammatory effects.
Characterization and Comparative Investigation of Hydroxyapatite/Carboxymethyl Cellulose (CaHA/CMC) Matrix for Soft Tissue Augmentation in a Rat Model
(American Chemical Society, 2024) Karatas, Erkan; Koc, Kubra; Yilmaz, Mehmet; Aydin, Halil Murat
This study endeavors to develop an injectable subdermal implant material tailored for soft tissue repair and enhancement. The material consists of a ceramic phase of calcium hydroxyapatite (CaHA), which is biocompatible, 20-60 mu m in size, known for its biocompatibility and minimal likelihood of causing foreign body reactions, antigenicity, and minimal inflammatory response, dispersed in a carrier phase composed of carboxymethyl cellulose (CMC), glycerol, and water for injection. The gel formulation underwent comprehensive characterization via various analytical techniques. X-ray diffraction (XRD) was employed to identify crystalline phases and investigate the structural properties of ceramic particles, while thermogravimetric analysis (TGA) was conducted to evaluate the thermal stability and decomposition behavior of the final formulation. Scanning electron microscopy (SEM) was utilized to examine the surface morphology and particle size distribution, confirming the homogeneous dispersion of spherical CaHA particles within the matrix. SEM analysis revealed particle sizes ranging from approximately 20-60 mu m. Elemental analysis confirmed a stoichiometric Ca/P ratio of 1.65 in the hydroxyapatite (HA) structure. Heavy metal content exhibited suitability for surgical implant use without posing toxicity risks. Rheological analysis revealed a storage modulus of 58.6 and 68.9 kPa and a loss modulus of 21.7 and 24.8 kPa at the frequencies of 2 and 5 Hz, respectively. 150 mu L of sterilized CaHA/CMC was injected subcutaneously into rats and compared with a similar product, Crystalys, to assess its effects on soft tissues. Skin tissue samples of rats were collected at specific intervals throughout the study (30, 45, 60, 90 and 120 days), and examined histologically. Results demonstrated that CaHA/CMC gel led to a significant increase in dermal thickness, elastic fibers, and collagen density. Based on the findings, the formulated CaHA/CMC gel was found to be biocompatible, biodegradable, nonimmunogenic, nontoxic, safe, and effective, and represents a promising option for soft tissue repair and augmentation.
Cytotoxicity and Antibacterial Activity of Polyhedral Oligomeric Silsesquioxane Modified Ti3C2Tx MXene Films
(Nature Portfolio, 2025) Akinay, Yuksel; Karatas, Erkan; Ruzgar, Damla; Akbari, Ali; Baskin, Dilges; Cetin, Tayfun; Topuz, Mehmet
Bioactive antimicrobial films play important roles in various fields, such as biodegradable interfaces, tissue regeneration, and biomedical applications where preventing infection, biocompatibility, and immune rejection are important. In the present study, bioactive POSS-doped Ti3C2Tx MXene filled PLA composite film was prepared using the solution casting method for biomedical applications. The contact angle tests were investigated to reveal the usability of the thin films in biomedical applications. The angle decreased from 85.92 degrees degrees in pure PLA thin films to 72.23 degrees on POSS-doped Ti3C2Tx MXene films. The antibacterial performance, cytotoxicity and cell viability assessments of the prepared films have also been thoroughly investigated. Antibacterial tests revealed that the POSS-doped Ti3C2Tx MXene films effectively inhibited the growth of E. coli and S. aureus by 65.93% and 80.63%, respectively, within 4 h. These inhibition rates were observed as 58.32% and 54.97% for E. coli and S. aureus, respectively, after 24 h. Cytotoxicity assessments demonstrated that PMPs consistently showed higher cell viability due to the combination of POSS and Ti3C2Tx MXene. The obtained results suggest that the POSS-doped Ti3C2Tx MXene film is a promising candidate in cases where bacterial inhibition and high biocompatibility are of critical importance.
Functionalized Exosomes for Targeted Therapy in Cancer and Regenerative Medicine: Genetic, Chemical, and Physical Modifications
(BMC, 2025) Gabaran, Salar Ghaffari; Ghasemzadeh, Navid; Rahnama, Maryam; Karatas, Erkan; Akbari, Ali; Rezaie, Jafar
BackgroundExtracellular vesicles (EVs), such as exosomes, have been extensively discovered for their function in various diseases and potential therapeutic properties. In this review, we aimed to describe the therapeutic roles of functionalized exosomes in cancer and regenerative medicine.MethodsIn this review study, we studied numerous articles over the past two decades published on the application of exosomes in different diseases, as well as on perspectives and challenges in this field.ResultsRecent advancements have shown that exosomes can be used as a drug delivery system. However, this approach faces challenges such as low efficiency and non-targeting effects. Different methods, including genetic, chemical, and physical modifications, are used to functionalize exosome surfaces to address these limitations. In some cases, a combination of modification methods has been used to produce smart exosomes. Different therapeutic agents have been inserted on exosome surfaces by different modification methods. These functionalized exosomes can effectively deliver therapeutic agents to target cells. A growing body of evidence shows that functionalized exosomes are promising for cancer therapy and regenerative medicine. They can not only effectively deliver therapeutic agents to cancer cells, inhibiting tumorigenesis, but also efficiently contribute to tissue repair and regeneration by increasing cell proliferation and angiogenesis. In this review, we discuss different modification methods used to functionalize exosomes and related studies. In addition, we describe the application of functionalized exosomes in cancer and regeneration, along with challenges and perspectives.ConclusionsAlthough functionalized exosomes show promising results, further studies are essential for the clinical translation of these exosomes.
Regenerable Poly(dopamine)-Mediated Gold Nanostructure-Decorated Core-Shell Nanostructures of Magnetite/Polydopamine for Catalytic Dye Removal
(Amer Chemical Soc, 2024) Serginay, Nuray; Bingol, Mehmet Semih; Karatas, Erkan; Yilmaz, Mehmet
In this paper, we present a facile yet effective method for the fabrication of core-shell nanoparticles (NPs) of magnetite (Fe3O4) and polydopamine (Fe3O4@PDA) and their decoration with a tunable amount of gold NPs (AuNPs). For this, Fe3O4 NPs were fabricated through the polyol method and AuNPs were deposited onto Fe3O4@PDA via anchoring of as-prepared citrate-stabilized AuNPs or reduction of Au ions. PDA with its numerous catechol groups enabled the decoration of AuNPs in a well-controlled manner. The resultant Fe3O4@PDA@Au nanosystem exhibited highly efficient catalytic activity in removing crystal violet (CV) and malachite green (MG) as dye molecules. It was noticed that the quantity of deposited AuNPs was the primary determinant of the resulting catalytic activity of the suggested system. Both techniques resulted in NP systems demonstrating distinct catalytic activity with reaction constant values of 0.83 and 1.54 min-1 for removing CV and MG dyes, respectively. The complete dye removals were attained only within 4 min. Furthermore, the core-shell nanosystem was easily regenerated by removing it from the medium via an external magnet and subsequent washing. Even after five cycles, the catalytic system provided satisfying activity in both dyes indicating its high reusability capacity. The combination of AuNPs with distinct characteristics of PDA and magnetic NPs makes this core-shell nanosystem a viable platform for various catalytic and wastewater applications.
A Sensitive Nanocomposite Design Via Polydopamine Mediated Au and Ag Nanoparticles: Voltammetric Assay for Dopamine in Biological Samples
(Elsevier Science SA, 2022) Karatas, Erkan; Ozden, Dilek Sura; Yilmaz, Mehmet; Yazan, Zehra; Piskin, Erhan
In this study, an electrochemical sensor for the sensitive determination of dopamine was developed based on pencil graphite electrodes (PGEs) modified by two different approaches. In the first approach, the polydopamine (PDA)-coated PGEs (PDA@PGE) were decorated with the as-prepared citrate-stabilized gold or silver nanoparticles (cit-AuNPs and cit-AgNPs, respectively). In the second approach, similarly, PDA@PGE was decorated with metallic NPs by reducing silver (r-AgNPs) or gold ions (r-AuNPs). In this process, PDA with its numerous functional groups such as catechol and amine plays an essential role in both the reduction of the metallic ions and the adsorption and stabilization of the NPs. The characterization of the modified electrodes was examined by field-emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, ultraviolet-visible absorption spectra, and cyclic voltammetry. These observations depicted that the density of NPs could be manipulated over time, and 3 h of NPs deposition time was detected as optimal via electrochemical analysis. The PDA@PGEs decorated with AuNPs were also used for the electrochemical analysis of dopamine in calibration and validation studies. In the analysis of dopamine by the square wave voltammetry method, the limit of detection (LOD) and the limit of quantification (LOQ) were 0.53 and 1.77 mu M, respectively. For the differential pulse voltammetry, LOD and LOQ were 0.96 and 3.2 mu M, respectively. We observed that the PDA-coated PGEs decorated with AuNPs provided high accuracy, precision, reproducibility, and reliability. The experimental results were found to be insignificant at a 95% confidence level. The developed sensor was applied for the determination of dopamine in biological fluids.
Ti 3 C 2 T X Mxene-Functionalized Hydroxyapatite/Halloysite Nanotube Filled Poly- (Lactic Acid) Coatings on Magnesium: in Vitro and Antibacterial Applications
(Keai Publishing Ltd, 2024) Topuz, Mehmet; Akinay, Yuksel; Karatas, Erkan; Cetin, Tayfun
Magnesium (Mg) stands out in temporary biomaterial applications due to its biocompatibility, biodegradability, and low Young's modulus. However, controlling its corrosion through next-generation polymer-based functional coatings is crucial due to the rapid degradation behavior of Mg. In this study, the function of 2D lamellar Ti3 C2 Tx (MXene) in Hydroxyapatite (HA) and Halloysite nanotube (HNT) hybrid coatings in biodegradable poly- (lactic acid) (PLA) was investigated. The morphological and structural characterizations of the coatings on Mg were revealed through HRTEM, XPS, SEM-EDX, XRD, FTIR, and contact angle analyses/tests. Electrochemical in vitro corrosion tests (OCP, PDS, and EIS-Nyquist) were conducted for evaluate corrosion resistance under simulated body fluid (SBF) conditions. The bioactivity of the coatings in SBF have been revealed in accordance with the ISO 23,317 standard. Finally, antibacterial disk diffusion tests were conducted to investigate the functional effect of MXene in coatings. It has been determined that the presence of MXene in the coating increased not only surface wettability (131 degrees, 85 degrees, 77 degrees, and 74 degrees for uncoated, pH, PHH, and PHH/MXene coatings, respectively) but also increased corrosion resistance (1857.850, 42.357, 1.593, and 0.085 x 10-6 , A/cm2 for uncoated, pH, PHH, and PHH/MXene coatings, respectively). It has been proven that the in vitro bioactivity of PLA-HA coatings is further enhanced by adding HNT and MXene, along with SEM morphologies after SBF. Finally, 2D lamellar MXene-filled coating exhibits antibacterial behavior against both E. coli and S. aureus bacteria. (c) 2024 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ ) Peer review under responsibility of Chongqing University
Ti2ntx Mxene and Carbon Quantum Dots Modified Chitosan Scaffold for Potential Wound Healing: in Vitro Assessment of Cytotoxicity, Hemocompatibility, Antioxidant, and Antibacterial Properties
(Wiley-V CH Verlag GmbH, 2025) Karatas, Erkan; Topuz, Mehmet; Akinay, Yuksel
The development of multifunctional scaffolds capable of simultaneously promoting tissue regeneration, preventing infection, and maintaining hemocompatibility remains a key challenge in wound healing applications. Here, bio-functional porous chitosan scaffolds are developed by combining Ti2NTx MXene and carbon quantum dots (CQDs) for wound healing applications. Scaffold containing Ti2NTx and CQDs achieves 94.73% inhibition against Staphylococcus aureus and 76.13% against Escherichia coli. Hemocompatibility assays showed low hemolysis rates (0.98% for CS-CQDs-MXene), well below the 5% ASTM threshold, indicating excellent blood compatibility. Cytocompatibility studies using L929 fibroblast cells demonstrated high cell viability (>80%) and significant proliferation (125.58% at 72 h for CS-CQDs-MXene), with the scaffold promoting 46.32% wound closure in a 24-h scratch assay, outperforming CS (27.08%) and CS-CQDs (38.22%). CS-CQDs-MXene exhibited superior antioxidant activity across multiple assays, including 2,2 diphenyl-1-picrylhydrazyl (DPPH;39.5 mg TE/g), ferric reducing antioxidant power (FRAP:43.8 mg TE/g), total antioxidant capacity (TAC: 1.12 +/- 0.08 mmol TE/g), and metal chelating activity (MCA:17.76 +/- 0.36 mg EDTAE/g), indicating its capacity to scavenge free radicals and regulate redox balance in wound environments. These findings highlight the CS-CQDs-MXene scaffold as a promising multifunctional platform for wound healing, offering superior antibacterial activity, biocompatibility, and regenerative potential for advanced biomedical applications.
Ti3C2Tx MXene/Halloysite Nanotube Functionalized Films for Antibacterial Applications
(Taylor & Francis Ltd, 2025) Topuz, Mehmet; Karatas, Erkan; Ruzgar, Damla; Akinay, Yuksel; Cetin, Tayfun
In the study, chitosan (CS)-based Ti3C2Tx MXene/Halloysite nanotube (HNT) films were successfully synthesized using the solution casting method. The prepared films were characterized morphologically and structurally. To measure the surface wettability of the films for potential biological applications, contact angles were measured in simulated body fluid. The bacterial viability and antibacterial properties on Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria were evaluated by CFU counting, and statistical analyses were performed using ANOVA. The HNT particles with a size of about 30-40 nm were homogeneously anchored onto MXene layers without partial agglomerations. The presence of micropores and functional end groups in the prepared films contributes to their antibacterial effect. The incorporation of HNT into the chitosan MXene film provided a hydrophilic character by decreasing the contact angle from 82.26 degrees to 49.47 degrees. Antibacterial evaluation revealed that the film exhibited high inhibition for E. coli (34.63%) and S. aureus (63%) due to the synergistic effect between HNT and MXene. These findings highlight the potential of the developed film as an antibacterial material for biomedical applications.