Effectiveness of Polyelectrolyte Surfactant Nanoparticles in the Eradication of Bacterial Biofilms

Cystic fibrosis (CF), a genetic disease, is characterized by the buildup of thick mucus secretions in the lung. Due to the overproduction of mucus, patients are more susceptible to suffer from chronic bacterial infections, most notably due to Pseudomonas aeruginosa in adult CF patients. P. aeruginosa, a gram-negative species, exists in complex biofilm communities attached to living or abiotic surfaces. Biofilms are intricate bacterial communities with a protective extracellular matrix that contribute to inflammation and the presence of multi-drug resistant strains. The Roth Lab Group has previously developed a polyelectrolyte surfactant (PS) nanoparticle to aid with the controlled drug release and protection of cationic antimicrobials from degradation. Additionally, PS has the ability to penetrate into mucus and biofilm surfaces due to their amphiphilic nature. Polyelectrolyte surfactants are composed of an anionic poly (methacrylic acid) backbone with 10% Jeffamine M-2070 grafted as pendent chains. The anionic backbone encapsulates cationic antimicrobials via electrostatic self-assembly to form a biocompatible nanoparticle. Current cationic antimicrobials subjected to testing as nanoparticles are tobramycin and polymyxin B. Tobramycin is the gold standard antibiotic used against gram-negative species in cystic fibrosis, while polymyxin B is another antibiotic with activity against gram-negative species. To understand the efficacy of these nanoparticles against bacterial biofilms, their minimum biofilm eradication concentrations (MBEC) were analyzed on clinical isolates of P. aeruginosa from CF patients. The MBEC refers to the lowest concentration of an antimicrobial agent required to reduce the biofilm’s cell viability from attached surfaces. The results of the clinical strains treated with both nanoparticles and free antimicrobials shows that polyelectrolyte surfactant nanoparticles have consistently lower MBEC values than their cationic antimicrobial counterpart. The analysis indicates the polyelectrolyte surfactant nanoparticles are more efficient in the eradication of biofilms from attached surfaces. Future studies of polyelectrolyte surfactant nanoparticles include testing nanoparticles of various percent grafts and with additional antimicrobials, like polymyxin E.