Amalie Kjær Andresen1*,†, Matteo Tollemeto1*,†, Alex Cook2, Claus Sternberg3, Claus Moser4,5, Lars Jelskbak3, Lasse HE Thamdrup 1, Jan Van Hest2, Anja Boisen1 & Line Hagner Nielsen1
1Department of Health Technology, Technical University of Denmark, Kongens Lyngby, 2800, Denmark
2Department of Biomedical Engineering, Institute for Complex Molecular Systems, Eindhoven University of Technology, Eidhoven 5600, MB, The Netherlands
3DTU Bioengineering, Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, 2800, Denmark
4Department of Clinical Microbiology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, 2100, Denmark
5Department of Immunology and Microbiology, Copenhagen University Hospital, Copenhagen, 2100, Denmark
Summary
Bacterial biofilms, such as those found in chronic rhinosinusitis (CRS), present a major treatment challenge due to antibiotic resistance and limited drug penetration caused by the extracellular polymeric substance (EPS). Tobramycin, a cationic antibiotic, is effective but requires localized delivery to avoid systemic toxicity. This study explores pH-responsive polymersomes as a targeted drug delivery platform for tobramycin. These polymersomes, composed of PEG22-p(CL36-g-TMCmid9) with imidazole-functionalized side chains, remain stable at physiological pH but disassemble below pH 6, as found in biofilm microenvironments. Dynamic light scattering (DLS) confirmed structural disintegration in acidic buffer. Drug release assays demonstrated a strong burst release (~90%) at pH 5.3, mimicking biofilm conditions, and moderate release (~45%) at pH 7.4 due to the semipermeable nature of the polymersomes.
The biofilm eradication efficacy of the polymersomes was tested against 72-h mature Pseudomonas aeruginosa biofilms. Tobramycin-loaded nanoparticles significantly reduced live biomass compared to free tobramycin and unloaded particles. At 200 μg/mL, live fraction biomass decreased to 23.0 ± 15.9%, while free drug achieved only modest effects (95.5 ± 7.2% live fraction biomass). Unloaded nanoparticles also exhibited bacteriostatic activity, likely due to their positive surface charge interacting with bacterial membranes at more acidic pH. The enhanced efficacy of the loaded formulation is attributed to on-demand drug release triggered by the acidic biofilm environment. These results highlight the potential of pH-responsive polymersomes for localized CRS therapy, enabling efficient, targeted tobramycin delivery while minimizing off-target toxicity.