Rapid method for detection of Vibrio cholerae from drinking water with nanomaterials enhancing electrochemical biosensor.

Cholera is a potentially fatal diarrheal disease caused by Vibrio cholerae and is spread to humans from contaminated food and water. In order to prevent spread of epidemic chlorea, the development of novel sensitive, selective, user-friendly, cost-effective and rapid detection systems to detect of V. cholerae are necessary. Therefore, in this study, it was aimed to develop a specific, electrochemical immunoassay with high selectivitiy and sensitivity for detection of V. cholerae from drinking water using in house synthesized Gold Nanoparticles (AuNPs). The synthesized AuNPs were characterized by UV/Vis spectroscopy, Dynamic Light Scattering (DLS) and Atomic Force Microscopy (AFM) and electrochemical techniques were applied to confirm the succesful fabrication of the immunosensor. Also, this study focuses on the development of an antibody sensor for V. cholerae detection using a standard immunoassay without using nanoparticle. To accomplish that, in house spherical synthesized AuNPs at various sizes were synthesized, conjugated with secondary antibody-horseradish peroxidase enzyme (HRP) complex and their possible effect on the lowest detection limit of V. cholerae was investigated in comparison to commercially available AuNPs. The AuNPs-immunosensor on the results enabled the quantification of V. cholerae in a wide concentration range with a high sensitivity limit of detection (1 Colony-Forming Units/Milliliter) and specificity. Although the effect of 33 and 54 nm AuNPs on the process is close to each other, it has been observed that there is a 34% loss of efficiency when the size of the nanoparticle increases. With this study, a novel V. cholerae specific immunosensor was developed and the effects of in house synthesized AuNPs with various diameter on this developed biosensor were investigated in detail.

Systematic Investigation of Cellular Response to Hydroxyl Group Orientation Differences on Gold Glyconanoparticles.

Nanoparticle (NP) surfaces act as the interface as they interact with living systems and play a critical role in defining their cellular response. The nature of these interactions should be well understood to design safer and more effective NPs to be used in a wide range of biomedical applications. At the moment, it is not clear how a subtle change in surface chemistry will affect an NP's behavior in a biological system. Thus, understanding the role of such a small change is critical and may allow one to fine-tune a biological response. In this study, the cellular response to -OH orientation differences generated on gold glyconanoparticles, which are recently considered promising therapeutic agents as they mimic a glycocalyx, is investigated. As model molecules, glucose and mannose (C2 epimer) as monosaccharides and lactose and maltose (galactose and glucose as free units, C4 epimer) as disaccharides were chosen to monitor the cellular response in A549, BEAS-2b, and MDA-MB-231 cells through cellular uptake, cytotoxicity, and cell cycle progression. The three cell lines gave various and remarkable cellular responses to the same subtle -OH differences on gold glyconanoparticles, and it is determined that not only -OH orientation differences but also the number of saccharides on gold glyconanoparticles affect the cellular response. It was shown that mannose (C2 epimer to glucose) was significant with the promise of being a therapeutic agent for lung cancer therapy, whereas the toxicological profile of MDA-MB-231 cells was affected by AuNPs-glucose the most. This study demonstrates that clearly small chemical alterations on a NP surface can result in a significant cellular response. It can be concluded that the -OH orientation at the second and fourth carbon of a carbohydrate ring has a critical role in designing and engineering novel gold glyconanoparticles (consisting of monolayer mono- or disaccharides) for a specific cancer therapy.

Maltose functionalized magnetic core/shell Fe3O4@Au nanoparticles for an efficient l-asparaginase immobilization.

In this study, maltose-functionalized magnetic core/shell nanoparticles (Fe3O4@Au NPs) as a promising carrier matrix for a simple and effective immobilization of l-asparaginase (l-ASNase) were prepared and characterized using imaging techniques including atomic force microscopy (AFM) and transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The results indicate that the NPs are monodispersed with an average diameter of 10 nm and magnetization of 9.0 emu g-1. Under the optimal conditions, 77.2 ±â€¯2.3% of the total l-ASNase was immobilized. It was found that the acid-base tolerance and thermal stability of immobilized l-ASNase were significantly improved in comparison to the free form of the enzyme in solution. For instance, while only 10% of the immobilized enzyme was lost its activity, the free form was lost its activity more than 50% after 3 h incubation at 55 °C. After 13 times recycling, the immobilized l-ASNase retained about 50% of its initial activity. Moreover, the free and immobilized l-ASNase maintained their initial activities about 25 and 64% after 28 days storage at 25 °C, respectively. Km value of immobilized l-ASNase decreased to 1.59 from 2.95 mM as an indication of increased enzyme affinity for the substrate. The results of this study suggest that the maltose-coated magnetic nanoparticles are excellent nanovehicles to carry enzymes for a range of industrial applications.

Surface-Enhanced Raman Scattering to Evaluate Nanomaterial Cytotoxicity on Living Cells.

The increasing number of reports about false positive or negative results from conventional cytotoxicity assays of nanomaterials (NMs) suggests that more reliable NM toxicity assessment methods should be developed. Here, we report a novel approach for nanotoxicity evaluation based on surface-enhanced Raman spectroscopy (SERS). Three model NMs were tested on two model cell lines and the results were validated by WST-1 cytotoxicity assay and annexin V-FITC/propidium iodide (PI) staining as apoptosis-necrosis assay. The localization of nanoparticles (NPs) in the cells and the cellular conditions upon NP incubation were visualized by transmission electron microscopy (TEM) and enhanced dark-field (EDF) microscopy. SERS revealed a broader view on the consequences of cell-NM interactions compared to the conventional cytotoxicity assays where only one aspect of toxicity can be measured by one assay type. The results suggest that SERS can significantly contribute to the cytotoxicity evaluation bypassing NM or assay component-related complications with less effort.