Abstract
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.
Highlights
Over the past two decades, whole-cell biosensors (WCBs) have been widely used in the environmental, health-care, and agriculture sensing fields [1,2,3,4,5,6,7]
The results show that the bioluminescent bacteria that was adsorbed on the filter membrane disks demonstrated the highest sensitivity to 2% (v/v) ethanol, with 4 to 11 times higher sensitivity than the other two surface materials (Figure 5A)
The smartphone-based light signal detection was obtained with lower sensitivity when compared to the light signal detected by the microplate-reader
Summary
Over the past two decades, whole-cell biosensors (WCBs) have been widely used in the environmental, health-care, and agriculture sensing fields [1,2,3,4,5,6,7]. Sensors 2020, 20, 5486 fixing approach that is used in WCBs biosensor platforms These environmental toxicity monitoring assays that are conducted in the form of planktonic cells still present several drawbacks, including lower portability and storability, due to the requirement to regrow the bioreporter cells for each test. Various surfaces (e.g., polystyrene and nylon mesh) have been examined and used for the immobilization of bacterial cells in WCBs for environmental monitoring or bioremediation applications [12,24,25]. The integration of a WCB on a filter membrane disk with portable signal detection can further expand the access and use of the sensing platform in low-resource regions. In this study, the feasibility of integrating smartphone-based signal detection with WCB that utilizes a filter membrane disk with immobilized bioluminescent bacteria was examined for the monitoring of water toxicity. WCB device could enable improved sensing potential with a wide application range in the field of environmental monitoring
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