Department of Biology, Faculty of Science, Gazi University, Ankara, Turkey
Department of Analytical Chemistry, Faculty of Pharmacy, Gazi University, Ankara, Turkey
Turk J Med Sci. 2020 Jun 23;50(4):1157-1167. doi: 10.3906/sag-2002-234.
BACKGROUND/AIM: We aimed to develop a rapid method to enumerate Listeria monocytogenes (L. monocytogenes) utilizing magnetic nanoparticle based preconcentration and surface-enhanced Raman spectroscopy measurements.
Biological activities of magnetic Au-nanoparticles have been observed to have the high biocompatibility, and a sample immunosensor model has been designed to use avidin attached Au-nanoparticles for L. monocytogenes detection. Staphylococcus aureus (S. aureus) and Salmonella typhimurium (S. typhimurium) bacteria cultures were chosen for control studies. Antimicrobial activity studies have been done to identify bio-compatibility and bio-characterization of the Au-nanoparticles in our previous study and capturing efficiencies to bacterial surfaces have been also investigated.
We constructed the calibration graphs in various population density of L. monocytogenes as 2.2 × 101 to 2.2 × 106 cfu/mL and the capture efficiency was found to be 75%. After the optimization procedures, population density of L. monocytogenes and Raman signal intensity showed a good linear correlation (R2 = 0.991) between 102 to 106 cfu/mL L. monocytogenes. The presented sandwich assay provides low detection limits and limit of quantification as 12 cfu/mL and 37 cfu/mL, respectively. We also compared the experimental results with reference plate-counting methods and the practical utility of the proposed assay is demonstrated using milk samples.
It is focused on the enumeration of L. monocytogenes in milk samples and the comparision of results of milk analysis obtained by the proposed SERS method and by plate counting method stay in food agreement. In the present study, all parameters were optimized to select SERS-based immunoassay method for L. monocytogenes bacteria to ensure LOD, selectivity, precision and repeatablity.
背景/目的：本研究旨在开发一种基于磁纳米粒子预浓缩和表面增强拉曼光谱测量的李斯特菌（Listeria monocytogenes，L. monocytogenes）快速计数方法。
观察到磁性 Au 纳米粒子的生物活性具有高生物相容性，并设计了一种样品免疫传感器模型，用于使用连接在亲和素上的 Au 纳米粒子检测李斯特菌。金黄色葡萄球菌（Staphylococcus aureus，S. aureus）和鼠伤寒沙门氏菌（Salmonella typhimurium，S. typhimurium）细菌培养物被选作对照研究。在我们之前的研究中，进行了抗菌活性研究以确定 Au 纳米粒子的生物相容性和生物特性，并且还研究了它们对细菌表面的捕获效率。
我们构建了各种李斯特菌密度的校准曲线，范围为 2.2×101 至 2.2×106 cfu/mL，捕获效率为 75%。经过优化程序，李斯特菌的密度和拉曼信号强度在 102 至 106 cfu/mL 李斯特菌之间显示出良好的线性相关性（R2=0.991）。提出的三明治检测法提供了低检测限和定量限，分别为 12 cfu/mL 和 37 cfu/mL。我们还将实验结果与参考平板计数法进行了比较，并通过对牛奶样品的实际应用证明了所提出的检测方法的实用性。
本研究专注于牛奶样品中李斯特菌的计数，并对通过所提出的 SERS 方法和通过平板计数法获得的牛奶分析结果进行了比较，结果符合食品标准。在本研究中，优化了所有参数，以选择基于 SERS 的免疫分析方法用于李斯特菌细菌，以确保检测限、选择性、精密度和重复性。
