MULTIDISCIPLINARY RESEARCH ON METHODS AND TECHNOLOGIES ENABLING THE MONITORING OF BACTERIAL BIOFILM GROWTH AND DISINFECTION

Biofilm are dangerous for human health in many situation, from hospital to daily life. As sustainability is one of the topics of highest interest and with an impact at global level, the optimization of disinfection treatments to reduce the environmental impact is needed. Sensing technologies can provide a mean to fulfil these requirements. Hence, sensing methods enabling the detection of biofilm in early stage of formation and able to perform a real-time monitoring are sought for more and more. Due to the need to address these topics to develop know-how on research capable to delivery results in the short to long term, this work was structured to carry out both cutting-edge and application-oriented research. Upon a state of the art analysis, the atomic force microscopy (AFM) has been identified as a promising technology to investigate bacteria biofilms. Mechanical analysis on biofilms at different stages has been performed on P.fluorescens biofilms from 7 days up to 43 days old, revealing that there is a relation between softness of the biofilm and its age. In addition, AFM topography investigation of early-stage P.fluorescens biofilms before and after exposure to silica nanoparticles of 4nm and 100 nm diameter has been performed, showing that an interaction occurs with visible modification in cell morphology. Coupled with AFM studies, a laboratory setup based on a quartz crystal microbalance (QCM) with dissipation module, capable of detecting in real-time both mass and viscoelastic changes of bacteria biofilms, has been created. Experiments conducted, by adopting and optimizing suitable protocols for bacteria growth, have shown that disinfection processes provided by different chemical compounds can be effectively monitored through frequency and dissipation measurements. If QCM-based systems are robust and compact, they can be affected by some issues due to operational conditions that would need to be taken into account in the design of a system based on this technology for practical application.