Destruction of Pseudomonas aeruginosa pre-formed biofilms by cationic polymer micelles bearing silver nanoparticles

Low-biofouling membrane bioreactor: Effects of cis-2-Decenoic acid addition on EPS and biofouling mitigation

Biofouling is inevitable in the membrane process, particularly in membrane bioreactors (MBR) combined with activated sludge processes. Regulating microbial signaling systems with diffusible signal factors such as cis-2-Decenoic acid (CDA) can control biofilm formation without microbial death or growth inhibition. This study assessed the effectiveness of CDA in controlling biofouling in membrane bioreactors (MBRs), essential for wastewater treatment. By modulating microbial signaling, CDA mitigated biofilm formation without hindering microbial growth. Analysis using Confocal Laser Scanning Microscopy (CLSM) revealed structural alterations in the biofilm, reducing biomass and thickness upon CDA application. Moreover, examination of extracellular polymeric substances (EPS) highlighted a decrease in total EPS, particularly effective polysaccharides. In addition, the possibility of shifting from high molecular weight EPS to low molecular weight EPS was revealed through the change in dispersion activity. The 56% extension of MBR operational lifespan resulting from the reduction in EPS is anticipated to offer potential cost savings and improved performance. Despite these results, further investigation is crucial to validate any potential environmental risks associated with CDA and to comprehend its long-term effects at various conditions.

An Overview of Biofilm-Associated Infections and the Role of Phytochemicals and Nanomaterials in Their Control and Prevention

Biofilm formation is considered one of the primary virulence mechanisms in Gram-positive and Gram-negative pathogenic species, particularly those responsible for chronic infections and promoting bacterial survival within the host. In recent years, there has been a growing interest in discovering new compounds capable of inhibiting biofilm formation. This is considered a promising antivirulence strategy that could potentially overcome antibiotic resistance issues. Effective antibiofilm agents should possess distinctive properties. They should be structurally unique, enable easy entry into cells, influence quorum sensing signaling, and synergize with other antibacterial agents. Many of these properties are found in both natural systems that are isolated from plants and in synthetic systems like nanoparticles and nanocomposites. In this review, we discuss the clinical nature of biofilm-associated infections and some of the mechanisms associated with their antibiotic tolerance. We focus on the advantages and efficacy of various natural and synthetic compounds as a new therapeutic approach to control bacterial biofilms and address multidrug resistance in bacteria.

Ciprofloxacin-Loaded Mixed Polymeric Micelles as Antibiofilm Agents

In this work, mixed polymeric micelles (MPMs) based on a cationic poly(2-(dimethylamino)ethyl methacrylate)-b-poly(ε-caprolactone)-b-poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA₂₉-b-PCL₇₀-b-PDMAEMA₂₉) and a non-ionic poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO₉₉-b-PPO₆₇-b-PEO₉₉) triblock copolymers, blended at different molar ratios, were developed. The key physicochemical parameters of MPMs, including size, size distribution, and critical micellar concentration (CMC), were evaluated. The resulting MPMs are nanoscopic with a hydrodynamic diameter of around 35 nm, and the ζ-potential and CMC values strongly depend on the MPM's composition. Ciprofloxacin (CF) was solubilized by the micelles via hydrophobic interaction with the micellar core and electrostatic interaction between the polycationic blocks, and the drug localized it, to some extent, in the micellar corona. The effect of a polymer-to-drug mass ratio on the drug-loading content (DLC) and encapsulation efficiency (EE) of MPMs was assessed. MPMs prepared at a polymer-to-drug mass ratio of 10:1 exhibited very high EE and a prolonged release profile. All micellar systems demonstrated their capability to detach pre-formed Gram-positive and Gram-negative bacterial biofilms and significantly reduced their biomass. The metabolic activity of the biofilm was strongly suppressed by the CF-loaded MPMs indicating the successful drug delivery and release. The cytotoxicity of empty and CF-loaded MPMs was evaluated. The test reveals composition-dependent cell viability without cell destruction or morphological signs of cell death.

Novel β-Hairpin Peptide from Marine Polychaeta with a High Efficacy against Gram-Negative Pathogens

In recent years, new antibiotics targeting multidrug resistant Gram-negative bacteria have become urgently needed. Therefore, antimicrobial peptides are considered to be a novel perspective class of antibacterial agents. In this study, a panel of novel BRICHOS-related β-hairpin antimicrobial peptides were identified in transcriptomes of marine polychaeta species. Two of them—abarenicin from Abarenicola pacifica and UuBRI-21 from Urechis unicinctus—possess strong antibacterial potential in vitro against a wide panel of Gram-negative bacteria including drug-resistant strains. Mechanism of action assays demonstrate that peptides disrupt bacterial and mammalian membrane integrity. Considering the stronger antibacterial potential and a low ability of abarenicin to be bound by components of serum, this peptide was selected for further modification. We conducted an alanine and arginine scanning of abarenicin by replacing individual amino acids and modulating hydrophobicity so as to improve its antibacterial potency and membrane selectivity. This design approach allowed us to obtain the Ap9 analog displaying a high efficacy in vivo in the mice septicemia and neutropenic mice peritonitis models. We demonstrated that abarenicin analogs did not significantly induce bacterial resistance after a four-week selection experiment and acted on different steps of the biofilm formation: (a) killing bacteria at their planktonic stage and preventing biofilm formation and (b) degrading pre-formed biofilm and killing embedded bacteria. The potent antibacterial and antibiofilm activity of the abarenicin analog Ap9 with its high efficacy in vivo against Gram-negative infection in mice models makes this peptide an attractive candidate for further preclinical investigation.