Application of biofilm dispersion-based nanoparticles in cutting off reinfection.

Bacterial biofilms commonly cause chronic and persistent infections in humans. Bacterial biofilms consist of an inner layer of bacteria and an autocrine extracellular polymeric substance (EPS). Biofilm dispersants (abbreviated as dispersants) have proven effective in removing the bacterial physical protection barrier EPS. Dispersants are generally weak or have no bactericidal effect. Bacteria dispersed from within biofilms (abbreviated as dispersed bacteria) may be more invasive, adhesive, and motile than planktonic bacteria, characteristics that increase the probability that dispersed bacteria will recolonize and cause reinfection. The dispersants should be combined with antimicrobials to avoid the risk of severe reinfection. Dispersant-based nanoparticles have the advantage of specific release and intense penetration, providing the prerequisite for further antibacterial agent efficacy and achieving the eradication of biofilms. Dispersant-based nanoparticles delivered antimicrobial agents for the treatment of diseases associated with bacterial biofilm infections are expected to be an effective measure to prevent reinfection caused by dispersed bacteria. KEY POINTS: • Dispersed bacteria harm and the dispersant's dispersion mechanisms are discussed. • The advantages of dispersant-based nanoparticles in bacteria biofilms are discussed. • Dispersant-based nanoparticles for cutting off reinfection in vivo are highlighted.

Influence of algal-extracellular polymeric substances (EPS) on the pristine and combined toxicity of TiO2 NPs and PSNPs in Artemia salina: Eco-corona enhances the toxic effects.

The study on the influence of Natural Organic Matter (NOM) over the individual and combined effects of different nanomaterials on marine species is pertinent. The current study explores the role of Extracellular Polymeric Substances (EPS) in influencing the individual and combined toxic effects of polystyrene nanoplastics (PSNPs) viz. aminated (NH2-PSNPs), carboxylated (COOH-PSNPs), and plain PSNPs and TiO2 NPs in the marine crustacean, Artemia salina. A. salina was interacted with pristine PSNPs, pristine TiO2 NPs, EPS incubated PSNPs, EPS incubated TiO2 NPs, binary mixture of PSNPs and TiO2 NPs, and EPS adsorbed binary mixture of PSNPs and TiO2 NPs for 48 h. The present study proves that, when compared to the pristine toxicity of PSNPs and TiO2 NPs, the coexposure of TiO2 NPs with PSNPs resulted in increased toxicity. The adsorption of algal EPS on the NMs (both in their pristine and combined forms) significantly increased the toxic nature of the NMs against A. salina. It was observed that with an increase in the hydrodynamic diameter of the particles, the mortality, oxidative stress, and ingestion of the NMs by A. salina increased. The uptake of Ti by A. salina from 8 mg/L TiO2 NPs, EPS adsorbed 8 mg/L TiO2 NPs, 8 mg/L TiO2 NPs + NH2-PSNPs and the EPS adsorbed mixture of 8 mg/L TiO2 NPs, 8 mg/L TiO2 NPs + NH2-PSNPs was observed to be 0.043, 0.047, 0.186, and 0.307 mg/g of A. salina. The adsorption of algal EPS on the NMs (both in their pristine and combined forms) significantly increased the toxic nature of the NMs against A. salina. The major outcomes from the current study highlight the role of EPS in exacerbating the toxicity of NMs in marine crustaceans.

The extracellular polymeric substances (EPS) accumulation of Spirulina platensis responding to Cadmium (Cd2+) exposure.

Spirulina platensis can secrete extracellular polymeric substances (EPS) helping to protect damage from stress environment, such as cadmium (Cd2+) exposure. However, the responding mechanism of S. platensis and the secreted EPS to exposure of Cd2+ is still unclear. This research focuses on the effects of Cd2+ on the composition and structure of the EPS and the response mechanism of EPS secretion from S. platensis for Cd2+ exposure. S. platensis can produce 261.37 mg·g-1 EPS when exposing to 20 mg·L-1 CdCl2, which was 2.5 times higher than the control group. The S. platensis EPS with and without Cd2+ treatment presented similar and stable irregularly fibrous structure. The monosaccharides composition of EPS in Cd2+ treated group are similar with control group but with different monosaccharides molar ratios, especially for Rha, Gal, Glc and Glc-UA. And the Cd2+ treatment resulted in a remarkable decline of humic acid and fulvic acid content. The antioxidant ability of S. platensis EPS increased significantly when exposed to 20 mg·L-1 CdCl2, which could be helpful for S. platensis protecting damage from high concentration of Cd2+. The transcriptome analysis showed that sulfur related metabolic pathways were up-regulated significantly, which promoted the synthesis of sulfur-containing amino acids and the secretion of large amounts of EPS.

Impacts of microplastic and seawater acidification on unicellular red algae: Growth response, photosynthesis, antioxidant enzymes, and extracellular polymer substances.

Microplastics (MPs) pollution and seawater acidification have increasingly become huge threats to the ocean ecosystem. Their impacts on microalgae are of great importance, since microalgae are the main primary producers and play a critical role in marine ecosystems. However, the impact of microplastics and acidification on unicellular red algae, which have a unique phycobiliprotein antenna system, remains unclear. Therefore, the impacts of polystyrene-MPs alone and the combined effects of MPs and seawater acidification on the typical unicellular marine red algae Porphyridium purpureum were investigated in the current study. The result showed that, under normal seawater condition, microalgae densities were increased by 17.75-41.67 % compared to the control when microalgae were exposed to small-sized MPs (0.1 µm) at concentrations of 5-100 mg L-1. In addition, the photosystem II and antioxidant enzyme system were not subjected to negative effects. The large-sized MPs (1 µm) boosted microalgae growth at a low concentration of MPs (5 mg L-1). However, it was observed that microalgae growth was significantly inhibited when MPs concentration increased up to 50 and 100 mg L-1, accompanied by the remarkably reduced Fv/Fm value and the elevated levels of SOD, CAT enzymes, phycoerythrin (PE), and extracellular polysaccharide (EPS). Compared to the normal seawater condition, microalgae densities were enhanced by 52.11-332.56 % under seawater acidification, depending on MPs sizes and concentrations, due to the formed CO2-enrichment condition and appropriate pH range. PE content in microalgal cells was significantly enhanced, but SOD and CAT activities as well as EPS content markedly decreased under acidification conditions. Overall, the impacts of seawater acidification were more pronounced than MPs impacts on microalgae growth and physiological responses. These findings will contribute to a substantial understanding of the effects of MPs on marine unicellular red microalgae, especially in future seawater acidification scenarios.