Using diffusion coefficients as a means of analyzing the impact of medicinal plant extracts on biofilm growth and structural integrity

Understanding the rate of biofilm growth is essential for providing insight into how biofilm inhibitors work, and allows for examination of how plant extracts impact gene expression within the biofilm structure. In previous work, the diffusion coefficient (D) of polystyrene microspheres was used to quantify biofilm growth rates of Sinorhizobia meliloti within microfluidic devices. In this study, we extended this technology to models of  Staphylococcus aureus biofilm formation to examine the activity of extract 220D-F2, isolated from a medicinal plant (Rubus ulmifolius), on biofilm structural integrity. Here, we discuss how fluorescence microscopy and a particle tracking algorithm in Matlab can be used to measure the D values of microspheres within the biofilms. The study outcomes include development of further insights into the structure of biofilms and the mechanisms by which these inhibitors take effect – all within a microfluidic device that allows experiments to be handled on a small scale.