A high sensitive microwave sensor to monitor bacterial and biofilm growth

Bacterial biofilms have a significant economic and health impact in many different domains. In such films, the extracellular matrix prevents the diffusion of biocides, so antibiotic treatments require a concentration 500 to 1000 times higher than that used to eliminate the same bacteria when present as planktonic stage. Early detection of biofilms is therefore essential for effective eradication. In this paper, we present the development of a real-time and label-free radiofrequency biosensor dedicated to the monitoring of bacteria and biofilm growth. Its principle relies on an open-ended coaxial probe sensitive to the variation of the electrical conductivity of the probed medium in the microwave range. As shown, between 0.3 and 1 GHz, the high sensitivity of the method (2.3 × 104 CFU/mL) highlights the biofilm growing at the early stage of its formation. To demonstrate experimentally such effects, two model bacteria, Vibrio natriegens and P. aeruginosa, are considered. The proposed method should therefore be considered as a promising technique for biofilm monitoring in batch bioreactors or flow cells experiments.