Antibacterial and anti-biofilm activities of probiotic Lactobacillus curvatus BSF206 and Pediococcus pentosaceus AC1-2 against Streptococcus mutans.

Streptococcus mutans (S. mutans) is the most important oral pathogenic bacterial cause of dental caries. Here we investigated the abilities of probiotic lactobacillus strains of Lactobacillus curvatus (L. curvatus) BSF206 and Pediococcus pentosaceus (P. pentosaceus) AC1-2 to control S. mutans. Both probiotic strains are acid and bile salt tolerant and are resistant to hydrogen peroxide and lysozyme to promote their survival within the oral environment. In addition, both strains are highly hydrophobic and are also capable of engaging in electrostatic interactions. These properties enhance abilities of both strains to adhere to gingival epithelial cells and HT-29 for improved colonization of oral tissues, while also enabling these probiotics auto-aggregate and to form aggregates with S. mutans that both may prevent S. mutans from colonizing oral tissues and facilitate the clearance of the cariogenic bacteria from the mouth during swallowing of food and saliva. Furthermore, results presented herein revealed that L. curvatus BSF206 and P. pentosaceus AC1-2 effectively inhibited S. mutans activities (biofilm formation, secretion of extracellular matrix components, synthesis of water-insoluble glucans) and led to downregulation of expression of key S. mutans genes involved in biofilm production (gtfA, gtfB, ftf, brpA). Taken together, these results indicate that L. curvatus BSF206 and P. pentosaceus AC1-2 can inhibit S. mutans biofilm formation as a new strategy for preventing dental caries.

Comparative Effectiveness and Safety of Polyethylene Glycol Electrolyte Solution Versus Lactulose for Treatment of Hepatic Encephalopathy: A Systematic Review and Meta-analysis.

BACKGROUND: Hepatic encephalopathy (HE) is a complex neuropsychiatric syndrome associated with liver failure and/or portal systemic shunting. Polyethylene glycol (PEG) electrolyte solution is a commonly used for catharsis of gut, which has been demonstrated to relieve HE in a number of randomized controlled trials. The aim of this paper was to evaluate the comparative efficacy and safety of PEG with lactulose for current HE treatment. METHODS: PEG electrolyte solution versus lactulose of HE was deeply studied by conducting a systematic search in electronic databases and other sources until December 31, 2020. The PRISMA statement recommended the use of meta-analysis with 95% confidence interval (CI), relative risk (RR), and weighted mean deviation (WMD) as the estimated effect size. A sensitivity analysis was performed comprehensively to present the risk of bias and the source of heterogeneity. RESULTS: A total of 434 patients were involved in 7 randomized studies. It is found that there was a significant advantage of PEG therapy in the increase of clinical efficacy (RR=1.46; 95% CI: 1.26-1.68; P=0.000; I2=0.0%) and the decrease of hospital stay (WMD=-1.78; 95% CI: -2.72 to 0.85; P=0.000; I2=90.1%). There was no significant difference in the incidence of adverse events (RR=0.75; 95% CI: 0.48-1.19; P=0.222>0.05; I2=7.2%) and the level of serum ammonia (WMD=9.02; 95% CI: -14.39 to 32.43; P=0.45>0.05; I2=84.9%) after 24 hours between the 2 groups. CONCLUSIONS: The results prove that PEG has a beneficial effect on the treatment of HE. Compared with lactulose, PEG can lead to more rapid HE resolution during the first 24 hours and shorten the length of stay without increasing the rate of adverse effects.

A rapid and efficient polyethylenimine-based transfection method to prepare lentiviral or retroviral vectors: useful for making iPS cells and transduction of primary cells.

OBJECTIVES: To improve the efficiency, reproducibility and consistency of the PEI-based transfection method that is often used in preparation of recombinant lentiviral or retroviral vectors. RESULTS: The contributions to transfection efficiency of multi-factors including concentration of PEI or DNA, dilution buffer for PEI/DNA, manner to prepare PEI/DNA complexes, influence of serum, incubation time for PEI/DNA complexes, and transfection time were studied. Gentle mixing during the preparation of PEI/DNA transfection complexes is critical for a high transfection efficiency. PEI could be stored at room temperature or 4 °C, and most importantly, multigelation should be avoided. The transfection efficiency of the PEI-based new method in different types of cells, such as 293T, Cos-7, HeLa, HepG2, Hep3B, Huh7 and L02, was also higher than that of the previous method. After optimization, the titer of our lentiviral system or retroviral system produced by PEI-based new method was about 10- or 3-times greater than that produced by PEI-based previous method, respectively. CONCLUSION: We provide a rapid and efficient PEI-based method for preparation of recombinant lentiviral or retroviral vectors which is useful for making iPS cells as well as transduction of primary cell cultures.

Biomineral-binding liposomes with dual antibacterial effects for preventing and treating dental caries.

Dental caries is a chronic oral disease that results from the demineralization of dental hard tissues caused by the long-term interaction of various pathogenic factors in the human oral cavity. Although magnolol (Mag) and fluconazole (FLC) have shown promising antibacterial activity against Candida albicans (C. albicans) and Streptococcus mutans (S. mutans), their clinical application is limited due to hydrophobicity. In this study, we constructed biomineral-binding liposomes co-loaded with Mag and FLC (PPi-Mag/FLC-LPs) to overcome the hydrophobicity and achieve a dual antibacterial activity in the acidic microenvironment of caries. PPi-Mag/FLC-LPs were characterized by laser particle size analysis, transmission electron microscopy, and high-performance liquid chromatography (HPLC). The ability of PPi-Mag/FLC-LPs to bind hydroxyapatite was assessed in vitro using fluorescence microscopy and HPLC, while the antibacterial activity was examined by measuring drug effects on the acidogenicity, acid resistance, biofilm formation and survival of C. albicans and S. mutans. The pharmacodynamics of PPi-Mag/FLC-LPs was also evaluated in vivo in a rat model of dental caries. Mag and FLC were released rapidly from PPi-Mag/FLC-LPs in a pH-sensitive manner, and they bound effectively to hydroxyapatite, leading to a better antibacterial effect on C. albicans and S. mutans compared to free drugs or liposomes loaded with a single drug. PPi-Mag/FLC-LPs improved the medicinal properties of Mag and FLC and provided a rapid, pH-sensitive release of both drugs in vitro. PPi-Mag/FLC-LPs displayed good antibacterial activity in vivo, showing promise as a dual-drug delivery system for the prevention and treatment of caries.

Mechanism analyses of high specific filtration resistance of gel and roles of gel elasticity related with membrane fouling in a membrane bioreactor.

In this study, mechanisms and roles of gel elasticity in extremely high specific filtration resistance (SFR) were investigated. It was found that, as compared with cake layer in a membrane bioreactor (MBR), real gel layer in the MBR and agar gel possessed extremely high SFR. Foulant characterization showed that foulants were easy to bind water, and agar gel possessed a network structure. Mechanisms based on Flory-Huggins and Flory-Rehner models were deduced to describe the high SFR of agar gel. Model simulation showed that sum of SFR induced by the mixing chemical potential and the elastic chemical potential change is close to that of the agar gel, suggesting feasibility of the deduced models. Gel elasticity accounted for about 13% of total SFR of agar gel under conditions in this study. This study satisfactorily explained the extremely high SFR of gel, and addressed roles of gel elasticity in gel SFR.

Optimized PEI-based Transfection Method for Transient Transfection and Lentiviral Production.

Polyethyleneimine (PEI), a cationic polymer vehicle, forms a complex with DNA which then can carry anionic nucleic acids into eukaryotic cells. PEI-based transfection is widely used for transient transfection of plasmid DNA. The efficiency of PEI-based transfection is affected by numerous factors, including the way the PEI/DNA complex is prepared, the ratio of PEI to DNA, the concentration of DNA, the storage conditions of PEI solutions, and more. Considering the major influencing factors, PEI-based transfection has been optimized to improve its efficiency, reproducibility, and consistency. This protocol outlines the steps for ordinary transient transfection and lentiviral production using PEI. © 2017 by John Wiley & Sons, Inc.

Quantitative evaluation of the interfacial interactions between a randomly rough sludge floc and membrane surface in a membrane bioreactor based on fractal geometry.

In this paper, a new method for quantification of interfacial interactions between a randomly rough particle and membrane surface was proposed. It was found that sludge flocs in a membrane bioreactor were of apparent fractal characteristics, and could be modeled by the modified two-variable Weierstrass-Mandelbrot (WM) function. By combining the surface element integration (SEI) method, differential geometry and composite Simpson's rule, the quantitation method for calculating such interfacial interactions was further developed. The correctness and feasibility of the new method were verified. This method was then applied to evaluate the interfacial interactions between a randomly rough particle and membrane surface. It was found that, randomly rough particle possesses stronger interaction strength than regularly rough particle but weaker strength than smooth particle with membrane surface, indicating significant effects of surface morphology and roughness. The proposed method in this study has broad application prospect in membrane fouling study.

Influences of acid-base property of membrane on interfacial interactions related with membrane fouling in a membrane bioreactor based on thermodynamic assessment.

Failure of membrane hydrophobicity in predicting membrane fouling requires a more reliable indicator. In this study, influences of membrane acid base (AB) property on interfacial interactions in two different interaction scenarios in a submerged membrane bioreactor (MBR) were studied according to thermodynamic approaches. It was found that both the polyvinylidene fluoride (PVDF) membrane and foulant samples in the MBR had relatively high electron donor (γ(-)) component and low electron acceptor (γ(+)) component. For both of interaction scenarios, AB interaction was the major component of the total interaction. The results showed that, the total interaction monotonically decreased with membrane γ(-), while was marginally affected by membrane γ(+), suggesting that γ(-) could act as a reliable indicator for membrane fouling prediction. This study suggested that membrane modification for fouling mitigation should orient to improving membrane surface γ(-) component rather than hydrophilicity.

Membrane fouling in a membrane bioreactor: High filtration resistance of gel layer and its underlying mechanism.

A membrane bioreactor (MBR) was continuously operated to investigate mechanisms of fouling caused by the gel layer in this study. Agar was used as a model foulant for gel layer formation, and filtration resistance of gel layers was systematically assessed. The results showed that gel layer possessed unusually high specific filtration resistance (SFR) and high measured porosity as compared with cake layer. Current knowledge cannot explain the contradiction between high filtration resistance and high porosity of gel layer. A new fouling mechanism based on Flory-Huggins theory was then proposed. Filtration resistance of agar gel layer was found to be independent of pH and ionic strength, but linearly increase with gel thickness. The results are accordant with the mechanism deductions. Simulation of the mechanism model showed that the filtration resistance induced by mixing chemical potential variation was comparable to the experimental data of filtration resistance of agar gel layer, indicating that the proposed mechanism is the predominant mechanism responsible for the high filtration resistance of gel layer. The proposed mechanism was further verified from the bound water viewpoint.

Modeling three-dimensional surface morphology of biocake layer in a membrane bioreactor based on fractal geometry.

While the adsorptive fouling in membrane bioreactors (MBRs) is highly dependent of the surface morphology, little progress has been made on modeling biocake layer surface morphology. In this study, a novel method, which combined static light scattering method for fractal dimension (Df) measurement with fractal method represented by the modified two-variable Weierstrass-Mandelbrot function, was proposed to model biocake layer surface in a MBR. Characterization by atomic force microscopy showed that the biocake surface was stochastic, disorder, self-similarity, and with non-integer dimension, illustrating obvious fractal features. Fractal dimension (Df) of sludge suspension experienced a significant change with operation of the MBR. The constructed biocake layer surface by the proposed method was quite close to the real surface, showing the feasibility of the proposed method. It was found that Df was the critical factor affecting surface morphology, while other factors exerted moderate or minor effects on the roughness of biocake layer.

Effects of hydrophilicity/hydrophobicity of membrane on membrane fouling in a submerged membrane bioreactor.

The interfacial interactions between sludge foulants and four different types of membranes were assessed based on a new combined calculation method. Effects of membrane surface hydrophilicity/hydrophobicity on the interfacial interactions were investigated. It was found that, membrane surface hydrophilicity/hydrophobicity was not directly relevant to the interfacial interactions with sludge particles. Increasing membrane surface zeta potential could significantly increase the strength of the electrostatic double layer (EL) interaction and the energy barrier. For membrane with a surface roughness of 300nm, the total interaction was continuously repulsive in the separation distance coverage of 0-4nm in this study. The results suggest that, under conditions in this study, designing membranes with a high zeta potential and certain roughness can significantly mitigate membrane fouling, whereas, the strategy of improving membrane surface hydrophilicity cannot alleviate sludge adhesion in the membrane bioreactor.