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    Öğe
    E. coli O157:H7 Detection Using Surface Plasmon Resonance Based Biosensor
    (Hacettepe University, 2023) Eser, Esma; Ekiz, Okan Öner; Ekiz, H. İbrahim
    The detection of foodborne pathogenic bacteria remains a significant challenge, and the need for fast and sensitive detection methods is becoming increasingly important. Escherichia coli is a prevalent bacteria associated with foodborne illness, and this study aimed to evaluate the ability of a surface plasmon resonance (SPR) based biosensor to detect E. coli O157:H7 at low levels in pure culture and artificially contaminated bay leaves (Laurus nobilis) using different injection methods. To develop a biological sensing surface, the sensor surface was functionalized with 3-aminopropyltriethoxysilane (APTES), and polyclonal antibodies were immobilized on the surface for bacteria detection. Bacterial attachment to the antibodies resulted in a change in resonance angle. The biosensor was able to discriminate between cellular concentrations of 103 to 107 CFU/mL and showed potential in detecting different pathogens in various food samples. Before the SPR detection, the sample preparation step was optimized to ensure complex food matrices were suitable for SPR analysis. The results suggest that the SPR based biosensor is a promising tool for the rapid detection of foodborne pathogens in complex food matrices.
  • [ X ]
    Öğe
    Piyasadan Temin Edilen Defne Uçucu Yağlarının Kalite Özelliklerinin Karşılaştırılması ve Antimikrobiyal Özelliklerinin Belirlenmesi
    (2022) Gökşen, Gülden; Eser, Esma; Ekiz, H. İbrahim
    Son yıllarda defne yaprağı bitkisinden elde edilen uçucu yağın gıda, kozmetik, eczacılık, aromaterapi gibi farklı alanlarda kullanılması sonucu, üreticiler daha ucuz maliyetle daha fazla üretim arayışı içerisine girmiştir. Uçucu yağ eldesinde kullanılan yöntemin pahalı olması nedeniyle sabit yağlar veya farklı uçucu yağlar ile karıştırma yapılmaktadır.Bu çalışmada on farklı firmaya ait defneyaprağı uçucu yağı piyasadan temin edilmiştir. Standart olarak hidrodistilasyon yöntemi ile elde edilen defne yaprağı uçucu yağı ile firmalara ait uçucu yağların fiziko-kimyasal özellikleri ve antimikrobiyal aktiviteleri belirlenmiş ve karşılaştırılmıştır. Analiz sonuçlarına göre piyasadan temin edilen uçucu yağlardan bazılarının, standart olarak kullanılan uçucu yağ ile farklı olduğu görülmüştür. Sadece bir firmanın antimikrobiyal aktivite sonuçları benzerlik göstermektedir. Hatta bazı firmaların sabit yağlar/başka uçucu yağlar/çözücü kimyasal maddeler ile karıştırma yaptığı belirlenmiştir. Analiz sonuçları bütün uçucu yağlarda farklılık göstermektedir.
  • Küçük Resim
    Öğe
    Salmonella Detection in Food Using a HEK-hTLR5 Reporter Cell-Based Sensor
    (Mdpi, 2024) Eser, Esma; Felton, Victoria A.; Drolia, Rishi; Bhunia, Arun K.
    The development of a rapid, sensitive, specific method for detecting foodborne pathogens is paramount for supplying safe food to enhance public health safety. Despite the significant improvement in pathogen detection methods, key issues are still associated with rapid methods, such as distinguishing living cells from dead, the pathogenic potential or health risk of the analyte at the time of consumption, the detection limit, and the sample-to-result. Mammalian cell-based assays analyze pathogens' interaction with host cells and are responsive only to live pathogens or active toxins. In this study, a human embryonic kidney (HEK293) cell line expressing Toll-Like Receptor 5 (TLR-5) and chromogenic reporter system (HEK dual hTLR5) was used for the detection of viable Salmonella in a 96-well tissue culture plate. This cell line responds to low concentrations of TLR5 agonist flagellin. Stimulation of TLR5 ligand activates nuclear factor-kB (NF-kappa B)-linked alkaline phosphatase (AP-1) signaling cascade inducing the production of secreted embryonic alkaline phosphatase (SEAP). With the addition of a rho-nitrophenyl phosphate as a substrate, a colored end product representing a positive signal is quantified. The assay's specificity was validated with the top 20 Salmonella enterica serovars and 19 non-Salmonella spp. The performance of the assay was also validated with spiked food samples. The total detection time (sample-to-result), including shortened pre-enrichment (4 h) and selective enrichment (4 h) steps with artificially inoculated outbreak-implicated food samples (chicken, peanut kernel, peanut butter, black pepper, mayonnaise, and peach), was 15 h when inoculated at 1-100 CFU/25 g sample. These results show the potential of HEK-Dual (TM) hTLR5 cell-based functional biosensors for the rapid screening of Salmonella.
  • Küçük Resim
    Öğe
    Utilizing fab fragment-conjugated surface plasmon resonance-based biosensor for detection of Salmonella Enteritidis
    (Wiley, 2024) Eser, Esma; Ekiz, Okan Öner; Ekiz, Halil İbrahim
    Although antibodies, a key element of biorecognition, are frequently used as biosensor probes, the use of these large molecules can lead to adverse effects. Fab fragments can be reduced to allow proper antigen-binding orientation via thiol groups containing Fab sites that can directly penetrate Au sites chemically. In this study, the ability of the surface plasmon resonance (SPR) sensor to detect Salmonella was studied. Tris(2-carboxyethyl)phosphine was used as a reducing agent to obtain half antibody fragments. Sensor surface was immobilized with antibody, and bacteria suspensions were injected from low to high concentrations. Response units were changed by binding first reduced antibody fragments, then bacteria. The biosensor was able to determine the bacterial concentrations between 10(3 )and 10(8) CFU/mL. Based on these results, the half antibody fragmentation method can be generalized for faster, label-free, sensitive, and selective detection of other bacteria species.