A recombinant Escherichia coli biosensor for detecting polycyclic aromatic hydrocarbons in gas and aqueous phases.

Recombinant microbial biosensors are known to be simple, cheap, and very efficient monitoring tools for detecting various environmental pollutants in the field. However, although various recombinant microbial biosensors have been developed for aqueous-phase samples, very few are applicable to the gas phase. Here, we report a recombinant Escherichia coli biosensor that can be used to monitor polycyclic aromatic hydrocarbons (PAHs) in both gas and aqueous phases by color development. Among the PAHs, naphthalene and salicylate are often used as model compounds, since they are less toxic than other options and they are widely used in various applications. Here, recombinant E. coli cells carrying nahR (encoding the NahR regulatory protein for naphthalene degradation)::lac Z fusion genes were constructed and suspended (for aqueous measurements) or co-immobilized (for gaseous measurements) with chlorophenol red-ß-D-galactopyranoside (CPRG). Biosensing was then performed by ß-galactosidase, which hydrolyzed CPRG as a substrate, developing detectable red color with the naked eye. The system showed selective responses to salicylate and naphthalene. Importantly, its response to naphthalene was much more sensitive (about 10(5)-fold) in the gas phase compared to the aqueous phase. Thus, this system could potentially be used for the instrument-free, color-change-based monitoring of gaseous pollutants.

Conformable surface acoustic wave biosensor for E-coli fabricated on PEN plastic film.

Over the last decades, great effort has gone into developing new biosensor technologies for applications in different fields such as disease diagnosis and detection of pollutants in water and food. Global developments in robotic, IoT technologies and in healthcare sensors require new flexible sensor technologies that are low cost and built from sustainable and reusable or recyclable materials. One of the most promising technologies is based on the development of surface acoustic wave (SAW) flexible biosensors, which are highly reproducible, reliable and wirelessly controllable. This work presents for the first time a novel aluminum nitride (AlN)-based conformable SAW immunosensor fabricated on recyclable polyethylene naphthalate. We apply it to the detection of E.Coli using a faster and innovative functionalization method that exploit Protein-A/antibody affinity. A higher sensitivity (Limit of detection-LoD, 6.54*105 CFU/ml) of the Lamb wave traveling on the polymeric device has been obtained in comparison with SAWs traveling on AlN on silicon substrate (LoD, 1.04*106 CFU/ml). Implementation of a finite element method allowed for the estimation of the single E.Coli mass of approximately 9*10-13 g. This work demonstrates the high biosensing potential of flexible polymeric SAW devices for bacteria contamination control in food chain, water and smart packaging.