Enhanced biofilm inhibition via EPS-binding liposomes

Treating infectious diseases with current available antimicrobial drugs is extremely difficult due to biofilms that act as barriers and reduce the concentration of antimicrobial agents that reach the bacteria embedded in the biofilms. In this study, we hypothesized that extracellular polymeric substances (EPS)-binding PEGylated liposomes anchor to biofilm matrices and sterically block the communication between bacteria, leading to biofilm inhibition. A 16-mer peptide, which binds to hyaluronic acid as one of the EPS, was covalently conjugated to PEG (polyethylene glycol)-lipid for producing EPS-binding liposomes. The effect of the liposomes on inhibiting or eradicating biofilm formation was investigated, compared to the PEGylated liposomes (bare PEGylated liposomes). Dynamic light scattering (DLS) measurement results showed that the EPS-binding PEGylated liposomes and bare PEGylated liposomes have a particle size of < 200nm and nearly neutral zeta potential. The molecular interaction of EPS extracted from S. aureus biofilm with EPS-binding liposomes and free EPS-binding peptides was determined using isothermal titration calorimetry (ITC) and the result revealed that EPS-binding liposome (Ka ~ 4.82×10⁵) has better affinity than the free EPS-binding peptides (Ka ~ 1.79×10³). The minimal biofilm inhibitory concentration (MBIC) assay showed EPS-binding liposomes have a better biofilm inhibition effect, in a dose-dependent manner, compared to the bare PEGylated liposomes and free EPS-binding peptides. Physical disruption and blocking chemical communication (quorum sensing (QS)) via biofilm binding are likely a key mechanism behind the effectiveness of EPS-binding liposomes in biofilm inhibition although further study is needed.