Yazar "Ipek, Semih Latif" seçeneğine göre listele

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    An impedimetric determination of zearalenone on MIP-modified carboceramic electrode
    (Pergamon-Elsevier Science Ltd, 2024) Kucuk, Dilruba; Uner, Guelcan; Ipek, Semih Latif; Caglayan, Mustafa Oguzhan; Ustundag, Zafer
    Zearalenone (ZEN) is a mycotoxin that poses significant risks to human and animal health due to its mutagenic, immunosuppressive, and carcinogenic properties. This study presents a novel analytical method for detecting ZEN using electrochemical impedance spectroscopy (EIS) combined with a molecularly imprinted polymer (MIP). ZEN, used as the template molecule, was incorporated into polypyrrole on screen-printed electrodes (SPE), and a ZEN-sensitive MIP sensor was created through template removal. The modified sensor surfaces were characterized by EIS and scanning electron microscopy (SEM). An impedimetric MIP sensor for ZEN was developed, offering a detection range from 1 pM to 500 pM. The method's limit of detection (LOD) was established at 1 pM (0.3 pg/mL) with a signal-to-noise ratio of 3 (S/N = 3). The method demonstrated high precision and accuracy, with a maximum relative standard deviation (RSD) of less than 4.4% at a 95% confidence level, and relative error (RE) values ranging from -0.8% to -2.7%. The selectivity of the developed MIP sensor was evaluated using ochratoxin A, ochratoxin B, and aflatoxin B1, with no significant interference observed. ZEN recovery from spiked samples was between 95% and 105%, indicating that the method was successfully applied to grain samples, including corn, rice, and wheat.
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    Assessment of L-methioninase in volatile sulfur compound-rich Cheddar cheese slurries: bacterial community profiling via next-generation sequencing
    (Taylor & Francis Ltd, 2025) Ipek, Semih Latif; Gokturk, Dilek
    In this study, sulfur-containing aroma compounds and the associated shifts in bacterial community composition following the addition of L-methioninase to cheddar cheese slurries were examined. Four distinct slurry formulations were prepared: a control, a methionine-supplemented control, and two experimental groups supplemented with either L-methioninase or Brevibacterium linens. On day 1, Lactococcus and Streptococcus species were dominant across all samples. By day 9, bacterial diversity increased markedly in all formulations. On the first day of fermentation, L-methioninase activity led to the production of 1731.0 +/- 1.09 mu g kg-1 dry matter of methanethiol and 1490.2 +/- 1.31 mu g kg-1 dry matter of dimethyl trisulfide (DMTS). The concentrations of both methanethiol and DMTS increased further on days 4 and 9 of fermentation. These findings suggest that the use of L-methioninase in cheese slurries may represent a promising alternative strategy for the production of enzyme-modified cheese with enhanced sulfur aroma profiles.
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    Bacterial diversity and lysozyme activity of raw buffalo milk: a case study on milk collection tanks from selected farms
    (Taylor & Francis Ltd, 2024) Ipek, Semih Latif
    Approximately 15% of the milk produced in the world comes from buffaloes. In this study, the microbiome and lysozyme activities of buffalo milk in the Tepecik region were investigated. Samples were taken from ten different farms and analyzed. The average lysozyme activities were 59.858 units x 10-3/mL. Taxonomic analyses showed that Lactococcus, Acinetobacter, Moraxella, Streptococcus, Anoxybacillus, Aeromonas generally constituted the dominant bacterial groups. Low lysozyme activities and Staphylococcus aureus and Micrococcus luteus values showed that the milk taken from ten farms was mastitis free. The presence of Acinetobacter, Moraxella, Anoxybacillus and Aeromonas bacteria, which pose a pathogenic risk for milk, indicates that proper sanitation of milking machines are required. Pseudomonas, a psychrophilic bacterium, was not detected in most products, but was detected in very small amounts in some products. This work sheds a light on future studies that covers lysozyme activity measurement combined with DNA sequencing for food safety in dairy industry.
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    Cytotoxic Effect of L-Methioninase from Brevibacterium linens BL2 in Combination with Etoposide against Glioblastoma Cells
    (Mdpi, 2023) Ipek, Semih Latif; Ozdemir, Meryem Damla; Gokturk, Dilek
    L-methioninase degrades methionine, which is essential in methionine-dependent cancer cells, resulting in specific cell death. Normal cells can synthesize their own methionine amino acids even in the absence of exogenous methionine. This selective targeting of cancer cells makes L-methioninase a promising therapeutic candidate for cancer. In this study, L-methioninase was partially purified from Brevibacterium linens BL2. The specific activity of the enzyme was found as 3.055 units/mg. IC50 values (24 h) of the enzyme were 5.792 units/mL for U87MG cell line and 5.215 units/mL for T98G cell line. When L-methioninase and etoposide were used in combination, synergistic cytotoxic and cell migration inhibition effects on U87MG and T98G cells alongside decreased cytotoxic activity on the Mouse Embryonic Fibroblast and HaCaT cells compared to etoposide alone were observed. Additionally, colony numbers of U87MG cells were significantly reduced by L-methioninase and etoposide administration after 21 days of incubation. Furthermore, L-methioninase suppressed the expression levels of survivin and c-Myc while increasing the expression level of Caspase-3 in both glioblastoma cell lines. These effects were enhanced when etoposide was used in combination with etoposide. This investigation reveals that the L-methioninase enzyme not only exhibited cytotoxic effects on U87MG and T98G cells but also enhanced the anti-proliferative effects of etoposide when used in combination while also demonstrating fewer adverse effects on normal cells.
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    Impregnation of Melaleuca Family Essential Oil Nanoemulsions into Pectin:Polyvinyl Alcohol Patches to Provide an Antibacterial Environment for Infected Wounds
    (Wiley-VCH GmbH, 2025) Demir, Didem; Ceylan, Seda; Ipek, Semih Latif; Aslan, Deren; Oezbolat, Veli
    Essential oils have long been utilized in food, cosmetic, and medicinal applications. Recently, their biomedical use for wound healing, skin repair, and tissue regeneration has gained considerable attention. In this study, tea tree oil (TTO) and niaouli oil (NIO) were formulated into aqueous nanoemulsions (NEs) and incorporated into pectin/polyvinyl alcohol (PP) thin films to develop antibacterial wound dressing patches. The NEs were characterized by dynamic light scattering (DLS), and their morphological and chemical structures were also analyzed. The patches' morphology, hydrophilicity, swelling ratio, and mechanical properties were evaluated to assess the effect of NEs on material performance. Antibacterial activity assessed by plate count and agar diffusion methods against six bacteria commonly associated with infected wounds showed significant efficacy of NEs-loaded patches against Gram-negative strains and Escherichia coli. Direct and indirect cytotoxicity tests, using Mouse embryonic fibroblast (MEF) cells, confirmed that NEs incorporation maintained cell viability within acceptable limits and promoted their biocompatibility. These findings suggest that TTO and NIO-based nanoemulsion patches are promising candidates for antibacterial wound dressings.
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    Production of L-asparaginase from Candida utilis by solid-state fermentation: a comprehensive assessment of its antiproliferative potential on glioblastoma cells
    (Springer, 2025) Alkis, Meryem Damla Ozdemir; Ipek, Semih Latif; Tulek, Ahmet; Gunduz, Cennet Pelin Boyaci; Gokturk, Dilek
    L-asparaginase (L-ASNase) is an enzyme that depletes asparagine, a key amino acid for cancer cell survival, producing aspartic acid and ammonia. Beyond its food industry applications, L-ASNase is a clinically important agent against acute lymphoblastic leukemia (ALL). In this study, L-ASNase was produced and purified from Candida utilis via solid-state fermentation. Optimization on wheat bran identified 2 mL inoculation volume, 60% moisture, and a 4-day fermentation period as the optimal conditions, yielding 172.5 U/mL activity. The purified enzyme was tested against glioblastoma (GBM) cell lines, showing IC50 values of 0.4 U/mL for U87MG and 1.8 U/mL for T98G, with minimal toxicity toward normal HaCaT cells. Apoptotic effects were confirmed by DAPI/F-actin and Giemsa staining, while wound healing and clonogenic assays revealed inhibition of cell migration and colony formation. RT-qPCR analysis demonstrated downregulation of the Survivin gene, a key survival regulator. These findings highlight L-ASNase's potent antiproliferative, anti-migratory, and pro-apoptotic effects, underscoring its potential as an adjuvant therapy for GBM.
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    Recombinant Expression of L-methioninase from Brevibacterium linens and Evaluation of its Anticarcinogenic Properties against MiaPaCa-2 Cells
    (Bentham Science Publ Ltd, 2025) Ipek, Semih Latif; Alkis, Meryem Damla Ozdemir; Tulek, Ahmet; Gokturk, Dilek
    Introduction This study aimed to investigate the anti-carcinogenic effects of recombinant L-methioninase (rBlmet) on the pancreatic cancer cell line MiaPaCa-2.Methods In this study, rBlmet was initially cloned, expressed, and purified. To increase enzyme activity, the His-tags on the enzyme were removed using thrombin. rBlmet was then applied to MiaPaCa-2 cells, and the cell viability of MiaPaCa-2 cells was evaluated by neutral red assay after rBlmet treatment. The combined effect of etoposide with rBlmet against MiaPaCa-2 cells was also evaluated for 12 and 24 hours using a neutral red assay. Furthermore, cell morphology was evaluated by Giemsa and DAPI/F-actin staining methods. Survivin and caspase-3 gene expression levels were measured by RT-qPCR.Results and Discussion The specific activity of the enzyme increased after His-tag elimination to 5.62 mu mol/mg per minute. rBlmet showed a significant cytotoxic effect on the MiaPaCa-2 cell line. The IC50 value (24 h) of rBlmet for MiaPaCa-2 cells was 3.02 U/mL. In addition, rBlmet increased the cytotoxic effect of etoposide on the MiaPaCa-2 cell line, while it showed less effect on HaCat, which is a normal human cell line. Furthermore, rBlmet increased caspase-3 expression and downregulated survivin gene expression in MiaPaCa-2 cell lines.It successfully inhibited the growth of Mia-PaCa-2 cells by exploiting exogenous methionine amino acid in the growth medium. This study revealed promising results. However, further studies are needed on additional pancreatic cancer cell lines and in vivo models.Conclusion Based on these findings, it can be concluded that rBlmet not only has great potential to treat pancreatic cancer in the future but can also be used as an adjuvant to enhance the effectiveness ofchemotherapeutic agents like etoposide.
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    Skin in the game: a review of computational models of the skin
    (BMC, 2025) Ceylan, Seda; Demir, Didem; Harris, Cayla; Ipek, Semih Latif; Vavourakis, Vasileios; Manca, Marco; Dubrac, Sandrine; Bauer, Roman
    With the vast advances in computing technology, computational (or in silico) modelling has emerged as a transformative tool in dermatology. These findings can provide novel insights into complex biological processes and aid in the development of innovative therapeutic and regenerative strategies for the skin. Modelling combines experimental data and knowledge across multiple disciplines, serving as a common framework to elucidate the workings of the skin. From a biomedical perspective, the mechanisms of skin diseases can be studied by simulating cellular interactions and signalling pathways. Computational investigations of these mechanisms can be categorised into two distinct approaches: data-driven and model-based. Data-driven approaches allow the diagnosis of skin diseases on the basis of data collection via imaging or feedback from portable sensors, often yielding performance exceeding that of their human counterparts. Model-based methods are well suited to address topics such as skin cell biology and biomechanics, contributing to wound healing and skin cancer research. Furthermore, such modelling has found utility in the development of virtual skin models and skin-on-chip devices, enabling the prediction of skin responses to various substances, including cosmetics and drugs. In the realm of dermatological surgery, computational tools have been instrumental in optimizing surgical planning and improving clinical outcomes. While significant advancements have been made, challenges such as data availability, model validation, and interdisciplinary collaboration persist. This review highlights the current state-of-the-art in computational modeling in dermatology, identifies key challenges, and outlines its prospects.
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    Topical delivery of Niaouli essential oil nanoemulsion via Chitosan: Polyvinyl alcohol patches: A promising antimicrobial strategy for potential biomedical applications
    (Elsevier, 2026) Demir, Didem; Ipek, Semih Latif; Kahraman, Oskay; Dagli, Sibel; Ceylan, Seda
    Niaouli essential oil (NEO), selected as a bioactive compound, is a volatile oil known for its antiviral, antifungal, antibacterial, and antioxidant activities. To overcome the limitations associated with direct use of NEO, nanoemulsion formulations were developed, aiming for stability, long-term release, and controlled use. In this study, NEO nanoemulsions (NEO-NEs) were prepared, incorporated into a polymeric matrix, and evaluated for their potential use as antimicrobial patches. Three different oil-in-water emulsion formulations were produced, and the droplet size analyses were performed. Thin polymeric films were produced as carrier matrices for the optimal NEO-NEs formulation. Polymer matrices based on chitosan (CS) and polyvinyl alcohol (PVA) were physicochemically characterized in the presence of different volumes of NEO-NEs (10, 20, and 30 mu L). The sample containing 20 mu L of NEO-NEs exhibited a homogeneous morphology and achieved a swelling ratio of approximately 300 times its initial weight without compromising structural stability. Both direct and indirect cytotoxicity tests demonstrated that the NEO-NEs additive had no adverse effect on the biocompatibility. GC-MS analysis identified the main components of NEO, revealing a rich terpenoid composition that exhibited timedependent antioxidant activity. Release studies showed a controlled, stable, and sustained release profile over 48 h. Microbiological evaluations showed high antifungal activity, particularly against Candida albicans. Overall, the findings of this study highlight the significant potential of NEO-incorporated polymeric adhesive patches for the prevention of fungal infections.