Browsing by Subject "Whole cell biosensor"

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Open Access
Developing synthetic biology enabled whole cell biosensors
(2017-12) Saraylı, Side Selin Su
Main causative agent for environmental pollution is human activities. Especially with accelerated industrial improvements, many inorganics such as heavy metals or hazardous organic toxic materials are released to the environments via inadequate disposal policies of chemical wastes or accidental spills. These pollutants such as heavy metals could not be degraded easily in the environment. Moreover, tracking heavy metals levels in environmental samples is significant not only for controlling accumulation level of heavy metals in environment but also for human health due to heavy metal accumulation in kidney and liver via food web. Therefore, continuous monitoring of heavy metal pollution is important. For this purpose different kinds of sensor systems including biosensors are widely used. Even these conventional analytic methods are used in a broad range, there are attempts to propose innovative systems with advanced capabilities. Bacterial cells are able to serve as a whole cell biosensor and an analytic device because they naturally have all three layers of conventional sensor systems which are recognition layer, transducer layer and output actuators. Cells can detect changes in the environment and internal conditions via receptors worked as recognition element and placed strictly into membrane or freely in the cytoplasm. Receptors transmit this information into signal transduction pathways which serves as a transducer in the cell. Results of signal transduction pathways such as gene expression, gene repression, differences in concentration of specific molecules are classified as a signal and measured by appropriate device. Here we present our completed whole cell biosensors for urea, uric acid. Additionally we are presenting our results for cloning and expression of transcription factors for heavy metal sensing. As a future aim, we try to develop a fast, reliable and cost effective whole cell biosensor with the intention of sensing many important biomarkers in a conventional blood panel.
Open Access
A theranostic bio-device for biomedical applications
(2019-08) Hacıosmanoğlu, Nedim
Biological systems are programmable by their nature. With using the abilities of these systems, scientists have designed, engineered and repurposed living machines for various tasks including biological sensing, recording of cellular events, drug production and disease treatment. Compared to the current methodology for these tasks, engineering biological systems provide a promising tool for the future of medicine, especially in the case of disease treatment. Type II Diabetes Mellitus (T2DM) is a medical condition which occurs by the deficiency of insulinotropic hormones inside the body, and affects nearly half billion people worldwide. Treatment strategies for this disease includes monitoring patient for blood glucose levels, fine production of insulinotropic hormones and providing dose-controlled treatment for the patients. All these operations increase the cost of the treatment and cause a global problem for both medical professionals and the patients. In this thesis, we propose novel systems for developing theranostic strategies for T2DM by using synthetic biology principles and genetically controlled sense-and-response cascades inside living cells. Proposed systems include a whole-cell glucose biosensor module, which can detect glucose concentrations by using internal glycolysis machinery of a probiotic Escherichia coli (E. coli) bacteria, and a release module, which can controllably secrete therapeutic molecules from the E. coli cell surface. To do that, we engineered an enzyme based biosensor module which takes the pyruvate synthesized as a result of glycolysis and turns that molecule into hydrogen peroxide via SpxB pyruvate oxidase enzyme to later detect that signal with an optimized hydrogen peroxide biosensor. In order to later incorporate this biosensor with a release mechanism, we designed and engineered an Antigen-43 (Ag43) autotransporter based peptide release system. In that system, we used Ag43 autotransporter fused GLP-1 peptide, an insulinotropic hormone for the type II diabetes treatment that is controllably displayed on the cell surface. Another Ag43 fused protein, TEV protease, with a different control mechanism is also cooperated in the system to release GLP-1 from the surface by cutting the peptide from its recognition site. Taking the ability of glucose sensing and the successfully engineered release mechanisms, our proposed system has a huge potential to be used as an alternative system for treatment of the T2DM.