A self-amplifying plasmid based ultrasensitive biosensor for the detection of As(Ⅲ) in water

Due to their advantages such as high sensitivity, good selectivity, low cost, easy preservation and strong environmental adaptability, microbial whole-cell biosensors have broad potential and application prospects in the detection and prevention of environmental pollutants. However, it is often restricted because the sensitivity and the limit of detection (LOD), are not enough to meet the actual detection demand. Here, we developed a novel biosensor signal-amplifier by introducing a replication protein of RepL, which is mainly based on the plasmid copy number inducible system. The new amplifier is applied to develop an As(Ⅲ) microbial sensor. Through the further optimization of regulatory elements, the sensor exhibits fast response, high sensitivity, low LOD and good linearity. The results show that our sensor of pMT012 has a LOD as low as 0.018 ppb, and a fast response with a response time of 10 and 40 min at 5 and 0.5 ppb As(Ⅲ), respectively. The excellent performance of the sensor not only enables us to achieve the detection rapidly and accurately, but also presents great potential applications for rapid determination of As(Ⅲ) acute toxicity of the pollutants. Meanwhile, this new signal-amplifier is universal and can be widely applied to many other biosensors.