Publications

Treating bacterial biofilms remains a major clinical challenge, particularly in uropathogenic infections where the dense extracellular matrix impedes antibiotic access and protects tolerant bacterial populations. In this work, we explored a nanomaterial-based strategy to improve antibiotic responsiveness by combining iron oxide nanoparticles (IONPs) with pulsed laser irradiation to induce vapor nanobubble (VNB)-mediated disruption of a mature flow-grown uropathogenic E. coli CFT073 biofilm. We tested three nanoparticle sizes (70 nm, 130 nm, and 500 nm) and identified IONP500 as the most effective formulation for generating VNBs upon irradiation with 532 nm nanosecond laser pulses, with a VNB threshold of 0.56 J/cm2 per pulse. In the mature biofilm model, the combined IONP500 + ciprofloxacin + laser treatment significantly enhanced antibiotic activity compared with ciprofloxacin alone, increasing dead biomass from approximately 16% to 23%, corresponding to a 39-45% relative increase, as quantified by COMSTAT analysis and one-way ANOVA with Tukey's post-hoc test. The combined treatment also reduced total biofilm biomass and increased biofilm porosity by 55.8% compared with ciprofloxacin alone, supporting a mechanism based on VNB-mediated matrix disruption and improved antibiotic access. Overall, these results support the use of photothermally active, biocompatible IONPs as a promising complementary strategy to enhance the efficacy of conventional antibiotics against persistent biofilm-associated infections.

JTD Keywords: Cells, Ciprofloxacin potentiation, Iron oxide nanoparticles, Laser, Nanoparticles, Photoporation, Photothermal biofilm disruption, Prostate, Resistance, Transurethral resection, Uropathogenic biofilms, Vapor nanobubbles, Vaporization

Abstract Infections caused by biofilm-forming bacteria are a major threat to hospitalized patients and the main cause of chronic obstructive pulmonary disease and cystic fibrosis. There is an urgent necessity for novel therapeutic approaches, since current antibiotic delivery fails to eliminate biofilm-protected bacteria. In this study, ciprofloxacin-loaded poly(lactic-co-glycolic acid) nanoparticles, which were functionalized with DNase I, were fabricated using a green-solvent based method and their antibiofilm activity was assessed against Pseudomonas aeruginosa biofilms. Such nanoparticles constitute a paradigm shift in biofilm treatment, since, besides releasing ciprofloxacin in a controlled fashion, they are able to target and disassemble the biofilm by degrading the extracellular DNA that stabilize the biofilm matrix. These carriers were compared with free-soluble ciprofloxacin, and ciprofloxacin encapsulated in untreated and poly(lysine)-coated nanoparticles. DNase I-activated nanoparticles were not only able to prevent biofilm formation from planktonic bacteria, but they also successfully reduced established biofilm mass, size and living cell density, as observed in a dynamic environment in a flow cell biofilm assay. Moreover, repeated administration over three days of DNase I-coated nanoparticles encapsulating ciprofloxacin was able to reduce by 95% and then eradicate more than 99.8% of established biofilm, outperforming all the other nanoparticle formulations and the free-drug tested in this study. These promising results, together with minimal cytotoxicity as tested on J774 macrophages, allow obtaining novel antimicrobial nanoparticles, as well as provide clues to design the next generation of drug delivery devices to treat persistent bacterial infections.

JTD Keywords: Pseudomonas aeruginosa, Biofilm, Ciprofloxacin, DNase I, Nanoparticles