Characterization of antibiofouling behaviors of PVDF membrane modified by quaternary ammonium compound – combined use of QCM-D, FCM, and CLSM

In this study, we systematically evaluated the antibiofouling behavior of quaternary ammonium compound (QAC) blended polyvinylidene fluoride (PVDF) membrane using quartz crystal microbalance with dissipation monitoring (QCM-D) combined with flow cytometry (FCM) and confocal laser scanning microscopy (CLSM) measurements. QCM-D tests showed that the introduction of QAC reduced bacterial attachment due to the biocidal functions of QAC. FCM indicated that cell integrity of the bacteria in the suspension flowing along QAC-modified membrane surfaces during the QCM-D test was severely affected. CLSM confirmed the significantly lower attachment of bacteria and higher dead/live cell ratio onto the surface of modified membranes after the washing step in QCM-D tests. Both FCM and CLSM results validated the antibacterial behavior of QAC-modified membranes by a contact-killing mechanism, which is in agreement with that of QCM-D tests. In addition, the bacterial cells accumulated on modified membrane surface exhibited higher reversibility compared to the control membrane, indicating ease of membrane cleaning. The results highlight that the combined use of QCM-D, FCM, and CLSM can comprehensively characterize the antibiofouling behavior of membranes.