Using Exogenous Polymers to Engineer Biofilm Viscoelasticity

Biofilms are increasingly found in applications in which their viscoelasticity influences the outcomes. In this study, the use of exogenous charged polymers as a means of engineering biofilm viscoelasticity is explored. Commercially available, neutral, anionic, and cationic polymers are added to the growth medium at concentrations that do not impact the growth rates of Pseudomonas aeruginosa. Biofilms grown from these media in microfluidic channels are then mechanically tested via microrheology and compared to control systems grown without the presence of polymers. Both anionic and cationic polymers result in stiffening of biofilms, whereas neutral polymers have little to no discernible effect, indicating that charge plays an important role in allowing polymers to incorporate into the biofilm matrix. Increasing the molecular weight of the polymer appears to increase the disruption of the biofilm matrix, reducing biofilm stiffness. The mechanism of enhanced stiffness is attributable to the polymer backbone stiffness, providing increased mechanical rigidity to the biofilm matrix after it is incorporated.