Abstract
Microbial cell-based biosensors, which mostly rely on stress-responsive operons, have been widely developed to monitor environmental pollutants. Biosensors are usually more convenient and inexpensive than traditional instrumental analyses of environmental pollutants. However, the targets of biosensors are restricted by the limited number of genetic operon systems available. In this study, we demonstrated a novel strategy to overcome this limitation by engineering an enhanced green fluorescent protein (eGFP). It has been reported that combining two fragments of split-eGFP can form a native structure. Thus, we engineered new biosensors by inserting metal-binding loops (MBLs) between β-strands 9 and 10 of the eGFP, which then undergoes conformational changes upon interaction between the MBLs and targets, thereby emitting fluorescence. The two designed MLBs based on our previous study were employed as linkers between two fragments of eGFP. As a result, an Escherichia coli biosensor exhibited a fluorescent signal only when interacting with cadmium ions, revealing the prospect of a new biosensor for cadmium detection. Although this study is a starting stage for further developing biosensors, we believe that the proposed strategy can serve as basis to develop new biosensors to target various environmental pollutants.
Highlights
IntroductionEnvironmental pollution has become a major problem in recent years and has been steadily increasing with rapid industrial development, adversely affecting, among other factors, human health
Environmental pollution has become a major problem in recent years and has been steadily increasing with rapid industrial development, adversely affecting, among other factors, human health.Several measures have been developed and applied to reduce environmental pollution
Measuring the total amount of pollutants might lead to overestimation of their risk, as instrumental analysis usually extracts the general concentration of all pollutants from environmental samples but neglects pollutant–environment interactions [3,4]
Summary
Environmental pollution has become a major problem in recent years and has been steadily increasing with rapid industrial development, adversely affecting, among other factors, human health. Several measures have been developed and applied to reduce environmental pollution. Environmental monitoring is typically focused on the quantification of target pollutants in the environment using analytical instruments [1,2]. Typical methods are time-consuming, expensive, and only provide the total amount of pollutants in a region. Measuring the total amount of pollutants might lead to overestimation of their risk, as instrumental analysis usually extracts the general concentration of all pollutants from environmental samples but neglects pollutant–environment interactions [3,4]. The total amount and bioavailable portion of pollutants, especially in soils, have shown divergent results [5,6]. Bioavailability and Sensors 2019, 19, 1846; doi:10.3390/s19081846 www.mdpi.com/journal/sensors
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