Polyethylenimine Increases Antibacterial Efficiency of Chlorophyllin

Time-Separated Pulse Release-Activation of an Enzyme from Alginate-Polyethylenimine Hydrogels Using Electrochemically Generated Local pH Changes

β-Glucosidase (EC 3.2.1.21) from sweet almond was encapsulated into pH-responsive alginate-polyethylenimine (alginate-PEI) hydrogel. Then, electrochemically controlled cyclic local pH changes resulting from ascorbate oxidation (acidification) and oxygen reduction (basification) were used for the pulsatile release of the enzyme from the composite hydrogel. Activation of the enzyme was controlled by the very same pH changes used for β-glucosidase release, separating these two processes in time. Importantly, the activity of the enzyme, which had not been released yet, was inhibited due to the buffering effect of PEI present in the gel. Thus, only a portion of the released enzyme was activated. Both enzymatic activity and release were monitored by confocal fluorescence microscopy and regular fluorescent spectroscopy. Namely, commercially available very little or nonfluorescent substrate 4-methylumbelliferyl-β-d-glucopyranoside was hydrolyzed by β-glucosidase to produce a highly fluorescent product 4-methylumbelliferone during the activation phase. At the same time, labeling of the enzyme with rhodamine B isothiocyanate was used for release observation. The proposed work represents an interesting smart release-activation system with potential applications in biomedical field.

The 25-kDa linear polyethylenimine exerts specific antiviral activity against pseudorabies virus through interferencing its adsorption via electrostatic interaction

Pseudorabies virus (PRV) is the causative agent of Aujeszky's disease, which is responsible for enormous economic losses to the global pig industry. Although vaccination has been used to prevent PRV infection, the effectiveness of vaccines has been greatly diminished with the emergence of PRV variants. Therefore, there is an urgent need to develop anti-PRV drugs. Polyethylenimine (PEI) is a cationic polymer and has a wide range of antibacterial and antiviral activities. This study found that a low dose of 1 µg/mL of the 25-kDa linear PEI had significantly specific anti-PRV activity, which became more intense with increasing concentrations. Mechanistic studies revealed that the viral adsorption stage was the major target of PEI without affecting viral entry, replication stages, and direct inactivation effects. Subsequently, we found that cationic polymers PEI and Polybrene interfered with the interaction between viral proteins and cell surface receptors through electrostatic interaction to exert the antiviral function. In conclusion, cationic polymers such as PEI can be a category of options for defense against PRV. Understanding the anti-PRV mechanism also deepens host-virus interactions and reveals new drug targets for anti-PRV.IMPORTANCEPolyethylenimine (PEI) is a cationic polymer that plays an essential role in the host immune response against microbial infections. However, the specific mechanisms of PEI in interfering with pseudorabies virus (PRV) infection remain unclear. Here, we found that 25-kDa linear PEI exerted mechanisms of antiviral activity and the target of its antiviral activity was mainly in the viral adsorption stage. Correspondingly, the study demonstrated that PEI interfered with the virus adsorption stage by electrostatic adsorption. In addition, we found that cationic polymers are a promising novel agent for controlling PRV, and its antiviral mechanism may provide a strategy for the development of antiviral drugs.

Cationic cellulose filter papers modified with ZnO/Ag/GO nanocomposite as point of use gravity-driven filters for bacterial removal from water

The surface modification of filters with large pore sizes for the development of low-cost gravity-driven point-of-use (POU) technologies for water disinfection can be an effective strategy to empower people to access safe water instantly, especially in low- and middle-income countries. In this study, the surface of commercial cellulose filter papers, as cheap and bio-based filters, was modified with polydopamine (PDA), polyethyleneimine (PEI) and ZnO/Ag/GO nanocomposite (ZnO/Ag/GO@PDA/PEI papers) for bacterial removal from water. PDA/PEI incorporation introduced a cationic functional layer, which can entrap negative bacteria and make a stable chemical bond with the nanocomposite. ZnO/Ag/GO exhibited promising synergistic antibacterial activities (30 times stronger than ZnO). As a result, 3 sheets of ZnO/Ag/GO@PDA/PEI papers showed a 99.98% bacterial reduction (E. coli), which met the WHO standards. Moreover, the leached zinc and silver in the filtrate were far below the WHO's limits (380 and 10 ppb, respectively). The results showed that the modified papers could be reused multiple times. After six times of reuse, the flow rate dropped slightly (below 20%) and the bacterial removal efficiency was more than 99.9%. This study is valuable for developing filters for treating bacterial-contaminated water on-site with no need for energy, which is a demand in many countries.

New trends in the development of photodynamic inactivation against planktonic microorganisms and their biofilms in food system

The photodynamic inactivation (PDI) is a novel and effective nonthermal inactivation technology. This review provides a comprehensive overview on the bactericidal ability of endogenous photosensitizers (PSs)-mediated and exogenous PSs-mediated PDI against planktonic bacteria and their biofilms, as well as fungi. In general, the PDI exhibited a broad-spectrum ability in inactivating planktonic bacteria and fungi, but its potency was usually weakened in vivo and for eradicating biofilms. On this basis, new strategies have been proposed to strengthen the PDI potency in food system, mainly including the physical and chemical modification of PSs, the combination of PDI with multiple adjuvants, adjusting the working conditions of PDI, improving the targeting ability of PSs, and the emerging aggregation-induced emission luminogens (AIEgens). Meanwhile, the mechanisms of PDI on eradicating mono-/mixed-species biofilms and preserving foods were also summarized. Notably, the PDI-mediated antimicrobial packaging film was proposed and introduced. This review gives a new insight to develop the potent PDI system to combat microbial contamination and hazard in food industry.

Photodynamic Activity of Chlorophyllin and Polyethylenimine on Pseudomonas aeruginosa Planktonic, Biofilm and Persister Cells

Antimicrobial photodynamic inactivation is considered a promising antimicrobial approach that may not develop resistance in the near future. Here, we investigate the influence of the photosensitizer chlorophyllin (CHL) and the cationic permeabilizer polyethylenimine (PEI), exposed to a red light-emitting diode, on the human pathogen Pseudomonas aeruginosa free-living planktonic cells, the sessile biofilm and persister cells. The broth microdilution checkerboard method was used to test antimicrobial susceptibility. As a substrate for biofilms, the Calgary biofilm device was used, and the quantification of the biofilm biomass was carried out using a crystal violet assay. Serine hydroxamate was used for the induction of persisters. Our findings reveal that PEI ameliorates the antimicrobial activity of CHL against P. aeruginosa planktonic and biofilm states, and the concentration required to eradicate the bacteria in the biofilm is more than fourfold that is required to eradicate planktonic cells. Interestingly, the persister cells are more susceptible to CHL/PEI (31.25/100 µg mL-1) than the growing cells by 1.7 ± 0.12 and 0.4 ± 0.1 log10 reduction, respectively, after 15 min of illumination. These data demonstrate that CHL excited with red light together with PEI is promising for the eradication of P. aeruginosa, and the susceptibility of P. aeruginosa to CHL/PEI is influenced by the concentrations and the exposure time.

Short-Term Stability of Electrochemical Properties of Layer-by-Layer Coated Heterogeneous Ion Exchange Membranes

Layer-by-layer adsorption allows the creation of versatile functional coatings for ion exchange membranes, but the stability of the coating and resulting properties of modified membranes in their operation is a frequently asked question. This paper examines the changes in voltammetric curves of layer-by-layer coated cation exchange membranes and pH-metry of desalination chamber with a studied membrane and an auxiliary anion exchange membrane after short-term tests, including over-limiting current modes. The practical operation of the membranes did not affect the voltammetric curves, but enhanced the generation of H⁺ and OH^- ions in a system with polyethylenimine modified membrane in Ca²⁺ containing solution. It is shown that a distinction between the voltammetric curves of the membranes modified and the different polyamines persists during the operation and that, in the case of polyethylenimine, there is an additional zone of growth of potential drop in voltammetric curves and stronger generation of H⁺ and OH^- ions as indicated by pH-metry.