A high-throughput integrated biofilm-on-chip platform for the investigation of combinatory physiochemical responses to chemical and fluid shear stress

Biofilms are stable microbial structures that form and grow on surfaces in both industrial and biomedical sites. Physiochemical condition plays a key role in the development of biofilm removal strategies. This study presents an integrated, double-layer, high-throughput microfluidic chip for real-time screening of the combinatorial effect of antibiotic concentration and fluid shear stress (FSS), as two main physicochemical parameters, on biofilms. Biofilms of Escherichia coli LF82 and Pseudomonas aeruginosa were tested against gentamicin and Streptomycin to examine the time dependent effects of concentration and FSS on the integrity of the biofilm. A MatLab image analysis method was developed to measure the bacterial surface coverage and total fluorescent intensity of the biofilms after each treatment. The chip consists of two layers. The top layer contains the concentration gradient generator (CGG) capable of diluting the input drug linearly into four concentrations. The bottom layer contains four expanding FSS chambers imposing three different FSSs on cultured biofilms. As the result, 12 combinatorial states of concentration and FSS can be investigated on the biofilm simultaneously. Our results revealed that the E. coli biofilms reduced in both dose and shear intensity dependent manner, whereas the P. aeruginosa biofilms did not. This suggests that the effectiveness of biofilm removal is dependent on bacterial species and the environment. Our experimental system could be used to investigate the physicochemical responses of biofilm or assess the effectiveness of biofilm removal methods.