Roth, C. M. | bioRxiv Science

bioRxiv2025

Antimicrobial Loaded Graft-Copolymer Nanoparticles for Treatment of Pseudomonas aeruginosa Infections

Nearly 80% of cystic fibrosis patients are affected by persistent lung infections, with Pseudomonas aeruginosa being one of the major culprits. Treatment of P. aeruginosa is further complicated by its ability to form biofilms. Anionic compounds within the biofilm and thick cystic fibrosis mucus interact with cationic antimicrobials, hindering treatment efficacy. In this study, we investigated the treatment of lung infections by delivering antimicrobials via polyelectrolyte surfactants that are composed of an anionic poly(alkylacrylic acid) backbone with grafted polyetheramine pendent chains. When combined with cationic antimicrobials, they self-assemble into nanoparticles via electrostatic interactions. We assessed the role of backbone chemistry and graft density on nanoparticle physical properties and evaluated the antimicrobial activity of these formulations against planktonic and biofilm cultures of P. aeruginosa strains derived from clinical isolates. All synthesized polyelectrolyte surfactants demonstrated high levels of antimicrobial encapsulation, with the extent of drug bound corresponding to the calculated hydrophilic-lipophilic balance values. We observed significantly increased antimicrobial activity against planktonic cultures using nanoformulations containing one of the polyelectrolyte surfactants, PMAA-g-10%J. In contrast, all tested nanoformulations retained, but did not increase, activity against biofilms. By monitoring membrane potentials and nanoparticle uptake, it was found that the nanoparticles directly associate with the bacterial cell membranes, which may enhance drug delivery and underlie the improved activity against the planktonic bacteria. In conclusion, we provide a proof of concept for the design of polyelectrolyte surfactants for the nanoencapsulation and delivery of cationic drug cargoes against P. aeruginosa infections.

bioengineering↗

bioRxiv2022

Pharmacodynamic model of the dynamic response of Pseudomonas aeruginosa biofilms to drug treatments

Chronic infection by gram-negative bacteria such as Pseudomonas aeruginosa is a leading cause of morbidity and mortality in cystic fibrosis patients in whom overabundant mucus and the formation of bacterial biofilms pose barriers to drug delivery and effectiveness. Accurate pharmacokinetic-pharmacodynamic (PK-PD) models of biofilm treatment could be used to guide formulation and administration strategies to better control bacterial lung infections. To this end, we have developed a detailed pharmacodynamic model of P. aeruginosa treatment with the front-line antibiotics, tobramycin and colistin, and validated it on a detailed dataset of killing dynamics. A compartmental model structure was developed in which the key features are diffusion of drug through a boundary layer to the bacteria, concentration dependent interactions with bacteria, and passage of the bacteria through successive transit states before death. The number of transit states employed was greater for tobramycin, which is a ribosomal inhibitor, than for colistin, which disrupts bacterial membranes. For both drugs, the experimentally observed delay in killing of bacteria following drug exposure was replicated and was consistent with the diffusion time, though for tobramycin, there was an additional delay reflected in the model by passage through the transit states. For each drug, the PD model with a single set of parameters described data across a ten-fold range of concentrations and for both continuous and transient exposure protocols. Furthermore, the parameters fit for each drug individually were used to model the response of biofilms to combined treatment with tobramycin and colistin. The ability to predict drug response over a range of administration protocols allows this PD model to be integrated with PK descriptions to describe in vivo antibiotic response dynamics and to predict drug delivery strategies for improved control of bacterial lung infections. Author SummaryBiofilms are self-assembling bacterial communities that adhere to a surface and encase themselves in a protective coating. Biofilm infections are notoriously difficult to treat with conventional antibiotic administrations. To understand better the dynamics of bacterial biofilm killing in response to antibiotic treatment, we developed a mathematical model that integrates several features: drug diffusion through a boundary layer that includes the biofilm casing, concentration dependent cell damage, and passage of the cell through damaged states to eventual death. We validated the model by comparison with an extensive published dataset of biofilm response to treatment with the antibiotics, tobramycin and colistin. The model fits to these datasets were able to capture the observed trends for several antibiotic administration protocols, with model parameters reflecting the differences in mechanism of action between the two drugs. This validated model can be integrated with pharmacokinetic descriptions of drug distribution in the body over time to predict dosing and administration protocols for preclinical and clinical studies.

bioengineering↗