Design, Development and Applications of Highly Sensitive Protein-Based Capacitive Biosensors

Abstract: Highly sensitive biosensors were developed for environmental and medical applications. The biosensors were based on bioengineered proteins as biorecognition elements coupled to a highly sensitive capacitive transducer. Heavy metal binding proteins like the metallothionein SmtA, regulatory protein MerR, periplasmic protein MerP and the synthetic phytochelatin EC20 were used for designing, constructing, and characterising biosensors for the determination of various heavy metal ions, i.e. mercury, copper, cadmium, zinc and lead, in a wide concentration range (fM-mM). The developed heavy metal biosensors had a useful storage stability (about two weeks) and could be regenerated using EDTA. The developed and optimised biosensors were assessed in two practical applications, namely monitoring mercury ions in contaminated soil samples, and measuring inducer molecules. The SmtA based biosensor was successfully used to monitor heavy metals in soil samples originating from a contaminated agricultural site in Denmark. The obtained results were compared to those given by a bacterial biosensor, a plant sensor, and the total amount of mercury contained in the soil. Both the protein-based and the bacterial biosensor, proved to accurately monitor the ion content, giving results well in agreement with those shown by the total amount. By using the same sensing principle, biosensors based on lac repressor protein were developed for monitoring of different inducer molecules, e.g. IPTG, ONPG, and lactose, or DNA. The biosensor could differentiate between lac operator DNA contained in linearized plasmid DNA and circular plasmid DNA, and genomic DNA.