Detection of Bioavailable Cadmium by Double-Color Fluorescence Based on a Dual-Sensing Bioreporter System

Cadmium (Cd) is carcinogenic to humans and can accumulate in the liver, kidneys, and bones. There is widespread presence of cadmium in the environment as a consequence of anthropogenic activities. It is important to detect cadmium in the environment to prevent further exposure to humans. Previous whole-cell biosensor designs were focused on single-sensing constructs but have had difficulty in distinguishing cadmium from other metal ions such as lead (Pb) and mercury (Hg). We developed a dual-sensing bacterial bioreporter system to detect bioavailable cadmium by employing CadC and CadR as separate metal sensory elements and eGFP and mCherry as fluorescent reporters in one genetic construct. The capability of this dual-sensing biosensor was proved to simultaneously detect bioavailable cadmium and its toxic effects using two sets of sensing systems while still maintaining similar specificity and sensitivity of respective signal-sensing biosensors. The productions of double-color fluorescence were directly proportional to the exposure concentration of cadmium, thereby serving as an effective quantitative biosensor to detect bioavailable cadmium. This novel dual-sensing biosensor was then validated to respond to Cd(II) spiked in environmental water samples. This is the first report of the development of a novel dual-sensing, whole-cell biosensor for simultaneous detection of bioavailable cadmium. The application of two biosensing modules provides versatile biosensing signals and improved performance that can make a significant impact on monitoring high concentration of bioavailable Cd(II) in environmental water to reduce human exposure to the harmful effects of cadmium.

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Influence of the luxR Regulatory Gene Dosage and Expression Level on the Sensitivity of the Whole-Cell Biosensor to Acyl-Homoserine Lactone

Biosensors ◽

10.3390/bios11060166 ◽

2021 ◽

Vol 11 (6) ◽

pp. 166

Author(s):

Sergey Bazhenov ◽

Uliana Novoyatlova ◽

Ekaterina Scheglova ◽

Vadim Fomin ◽

Svetlana Khrulnova ◽

...

Keyword(s):

Gene Dosage ◽

Regulatory Gene ◽

Homoserine Lactone ◽

Threshold Concentration ◽

Expression Level ◽

Whole Cell ◽

Lux Biosensors ◽

Order Of Magnitude ◽

Whole Cell Biosensor ◽

Cell Biosensor

Aliivibrio fischeri LuxR and Aliivibrio logei LuxR1 and LuxR2 regulatory proteins are quorum sensing transcriptional (QS) activators, inducing promoters of luxICDABEG genes in the presence of an autoinducer (3-oxo-hexanoyl-l-homoserine lactone). In the Aliivibrio cells, luxR genes are regulated by HNS, CRP, LitR, etc. Here we investigated the role of the luxR expression level in LuxI/R QS system functionality and improved the whole-cell biosensor for autoinducer detection. Escherichia coli-based bacterial lux-biosensors were used, in which Photorhabdus luminescensluxCDABE genes were controlled by LuxR-dependent promoters and luxR, luxR1, or luxR2 regulatory genes. We varied either the dosage of the regulatory gene in the cells using additional plasmids, or the level of the regulatory gene expression using the lactose operon promoter. It was shown that an increase in expression level, as well as dosage of the regulatory gene in biosensor cells, leads to an increase in sensitivity (the threshold concentration of AI is reduced by one order of magnitude) and to a two to threefold reduction in response time. The best parameters were obtained for a biosensor with an increased dosage of luxRA. fischeri (sensitivity to 3-oxo-hexanoyl-l-homoserine lactone reached 30–100 pM).

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Electron transfer from Proteus vulgaris to a covalently assembled, single walled carbon nanotube electrode functionalised with osmium bipyridine complex: Application to a whole cell biosensor

Biosensors and Bioelectronics ◽

10.1016/j.bios.2010.10.016 ◽

2011 ◽

Vol 26 (5) ◽

pp. 2383-2389 ◽

Cited By ~ 30

Author(s):

Frankie J. Rawson ◽

David J. Garrett ◽

Donal Leech ◽

Alison J. Downard ◽

Keith H.R. Baronian

Keyword(s):

Electron Transfer ◽

Carbon Nanotube ◽

Proteus Vulgaris ◽

Single Walled Carbon Nanotube ◽

Whole Cell ◽

Single Walled Carbon ◽

Whole Cell Biosensor ◽

Cell Biosensor

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Lab-on-a-Chip Whole-Cell Biosensor

Encyclopedia of Nanotechnology ◽

10.1007/978-94-017-9780-1_100449 ◽

2016 ◽

pp. 1731-1731

Keyword(s):

Lab On A Chip ◽

Whole Cell ◽

Whole Cell Biosensor ◽

Cell Biosensor

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Smartphone-Based Whole-Cell Biosensor Platform Utilizing an Immobilization Approach on a Filter Membrane Disk for the Monitoring of Water Toxicants

Sensors ◽

10.3390/s20195486 ◽

2020 ◽

Vol 20 (19) ◽

pp. 5486

Author(s):

Junning Ma ◽

Dorin Harpaz ◽

Yang Liu ◽

Evgeni Eltzov

Keyword(s):

Low Cost ◽

Environmental Water ◽

Medical Diagnostics ◽

Whole Cell ◽

Filter Membrane ◽

Sensing Applications ◽

Bacterial Immobilization ◽

The Stability ◽

Whole Cell Biosensor ◽

Membrane Disk

Bioluminescent bacteria whole-cell biosensors (WCBs) have been widely used in a range of sensing applications in environmental monitoring and medical diagnostics. However, most of them use planktonic bacteria cells that require complicated signal measurement processes and therefore limit the portability of the biosensor device. In this study, a simple and low-cost immobilization method was examined. The bioluminescent bioreporter bacteria was absorbed on a filter membrane disk. Further optimization of the immobilization process was conducted by comparing different surface materials (polyester and parafilm) or by adding glucose and ampicillin. The filter membrane disks with immobilized bacteria cells were stored at −20 °C for three weeks without a compromise in the stability of its biosensing functionality for water toxicants monitoring. Also, the bacterial immobilized disks were integrated with smartphones-based signal detection. Then, they were exposed to water samples with ethanol, chloroform, and H2O2, as common toxicants. The sensitivity of the smartphone-based WCB for the detection of ethanol, chloroform, and H2O2 was 1% (v/v), 0.02% (v/v), and 0.0006% (v/v), respectively. To conclude, this bacterial immobilization approach demonstrated higher sensitivity, portability, and improved storability than the planktonic counterpart. The developed smartphone-based WCB establishes a model for future applications in the detection of environmental water toxicants.

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