Haibo Mu

Potent Antibacterial Nanoparticles against Biofilm and Intracellular Bacteria

The chronic infections related to biofilm and intracellular bacteria are always hard to be cured because of their inherent resistance to both antimicrobial agents and host defenses. Herein we develop a facile approach to overcome the above conundrum through phosphatidylcholine-decorated Au nanoparticles loaded with gentamicin (GPA NPs). The nanoparticles were characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS) and ultraviolet−visible (UV−vis) absorption spectra which demonstrated that GPA NPs with a diameter of approximately 180 nm were uniform. The loading manner and release behaviors were also investigated. The generated GPA NPs maintained their antibiotic activities against planktonic bacteria, but more effective to damage established biofilms and inhibited biofilm formation of pathogens including Gram-positive and Gram-negative bacteria. In addition, GPA NPs were observed to be nontoxic to RAW 264.7 cells and readily engulfed by the macrophages, which facilitated the killing of intracellular bacteria in infected macrophages. These results suggested GPA NPs might be a promising antibacterial agent for effective treatment of chronic infections due to microbial biofilm and intracellular bacteria.

Chitosan Coupling Makes Microbial Biofilms Susceptible to Antibiotics

Microbial biofilms, prevalent in nature and inherently resistant to both antimicrobial agents and host defenses, can cause serious problems in the chemical, medical and pharmaceutical industries. Herein we demonstrated that conjugation of an aminoglycoside antibiotic (streptomycin) to chitosan could efficiently damage established biofilms and inhibit biofilm formation. This method was suitable to eradiate biofilms formed by Gram-positive organisms, and it appeared that antibiotic contents, molecular size and positive charges of the conjugate were the key to retain this anti-biofilm activity. Mechanistic insight demonstrated chitosan conjugation rendered streptomycin more accessible into biofilms, thereby available to interact with biofilm bacteria. Thus, this work represent an innovative strategy that antibiotic covalently linked to carbohydrate carriers can overcome antibiotic resistance of microbial biofilms, and might provide a comprehensive solution to combat biofilms in industrial and medical settings.

Antioxidative Properties of Crude Polysaccharides from Inonotus obliquus

The mushroom Inonotus obliquus has been widely used as a folk medicine in Russia, Poland and most of the Baltic countries. In this study, water-soluble and alkali-soluble crude polysaccharides (IOW and IOA) were isolated from I. obliquus, and the carbohydrate-rich fractions IOW-1 and IOA-1 were obtained respectively after deproteination and depigmentation. Their contents, such as neutral carbohydrate, uronic acid and protein, were measured. Their antioxidant properties against chemicals-induced reactive species (ROS) including 1,1′-Diphenyl-2-picrylhydrazyl (DPPH) radical, hydroxyl radical and superoxide anion radical, as well as their protective effects on H2O2-induced PC12 cell death were investigated. Results showed that I. obliquus polysaccharides can scavenge all ROS tested above in a dose-dependent manner. IOA and its product IOA-1 could rescue PC12 cell viability from 38.6% to 79.8% and 83.0% at a concentration of 20μg/mL. Similarly, IOW and its product IOW-1 at the same dose, can also increase cell viability to 84.9% and 88.6% respectively. The antioxidative activities of water-soluble and alkali-soluble polysaccharide constituents from I. obliquus might contribute to diverse medicinal and nutritional values of this mushroom.

Extraction optimization, characterization and immunity activity of polysaccharides from Fructus Jujubae.

The versatile Fructus Jujubae is widely used in Chinese and Korean traditional medicine. In this study, the extraction optimization, characterization and immunostimulatory activities of polysaccharides from Fructus Jujubae were investigated. Based on a four-variable-three-level Box-Behnken statistical design, the optimal extraction parameters were optimized as follows: extraction temperature 90 °C, extraction time 3.23 h, water to raw material ratio 33:1 and extraction 3 times. Under these conditions, the experimental yield of polysaccharides was 6.47 ± 0.26%, which was close to the predicted yield value (6.54%). The crude Fructus Jujubae polysaccharide was further purified by DEAE-cellulose chromatography repeatedly, and two homogenous fractions, designated as RQP1d and RQP2d with molecular weight of 83.8 and 123.0 kDa respectively, were obtained. Their structures were determined by chemical analysis, Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). Finally, preliminary immunological tests indicated that both RQP1d and RQP2d significantly stimulated NO production in RAW264.7 macrophages, and promoted LPS-induced splenocyte proliferation. These data implied Fructus Jujubae polysaccharides had the potential to be explored as novel natural immunostimulant for using in functional foods or medicine.

Chitosan improves anti-biofilm efficacy of gentamicin through facilitating antibiotic penetration.

Antibiotic overuse is one of the major drivers in the generation of antibiotic resistant “super bugs” that can potentially cause serious effects on health. In this study, we reported that the polycationic polysaccharide, chitosan could improve the efficacy of a given antibiotic (gentamicin) to combat bacterial biofilms, the universal lifestyle of microbes in the world. Short- or long-term treatment with the mixture of chitosan and gentamicin resulted in the dispersal of Listeria monocytogenes (L. monocytogenes) biofilms. In this combination, chitosan with a moderate molecular mass (~13 kDa) and high N-deacetylation degree (~88% DD) elicited an optimal anti-biofilm and bactericidal activity. Mechanistic insights indicated that chitosan facilitated the entry of gentamicin into the architecture of L. monocytogenes biofilms. Finally, we showed that this combination was also effective in the eradication of biofilms built by two other Listeria species, Listeria welshimeri and Listeria innocua. Thus, our findings pointed out that chitosan supplementation might overcome the resistance of Listeria biofilms to gentamicin, which might be helpful in prevention of gentamicin overuse in case of combating Listeria biofilms when this specific antibiotic was recommended.

Novel pH-sensitive polysialic acid based polymeric micelles for triggered intracellular release of hydrophobic drug.

Polysialic acid (PSA), a non-immunogenic and biodegradable natural polymer, is prone to hydrolysis under endo-lysosomal pH conditions. Here, we synthesized an intracellular pH-sensitive polysialic acid-ursolic acid conjugate by a condensation reaction. To further test the drug loading capability, we prepared paclitaxel-loaded polysialic acid-based amphiphilic copolymer micelle (PTX-loaded-PSAU) by a nanoprecipitation method. Results showed PTX-loaded-PSAU exhibited well-defined spherical shape and homogeneous distribution. The drug-loading was 4.5% with an entrapment efficiency of 67.5%. PTX released from PTX-loaded-PSAU was 15% and 42% in 72 h under simulated physiological condition (pH 7.4) and mild acidic conditions (pH 5.0), respectively. In addition, In vitro cytotoxicity assay showed that PTX-loaded-PSAU retained anti-tumor (SGC-7901) activity with a cell viability of 53.8% following 72 h incubation, indicating PTX-loaded-PSAU could efficiently release PTX into the tumor cells. These results indicated that the pH-responsive biodegradable PTX-loaded-PSAU possess superior extracellular stability and intracellular drug release ability.

Unveiling the Mode of Action of Two Antibacterial Tanshinone Derivatives

In this study, 2-(N-pyrrolidine-alkyl) tanshinones bearing pyrrolidine groups were synthesized and the antibacterial mechanism was explored. These derivatives selectively elicited antibacterial activity against Gram-positive bacteria. Moreover, their antibacterial activities were time-, concentration-dependent and persistent. It appeared that Fenton-mediated hydroxyl radicals were involved, and the disruption of cell membranes was observed. This study indicates that 2-(N-pyrrolidine-alkyl) tanshinones might be potential candidates as antibacterial agents.

Variation in antioxidant activities of polysaccharides from Fructus Jujubae in South Xinjiang area.

The Fructus Jujubae has been widely used as favorable food and folk medicine in China and Russia. In this study, we compared the carbohydrate constituents and antioxidative effects of Fructus Jujubae polysaccharides from five different production areas in South Xinjiang. Results demonstrated that the average annual temperature (r=0.590) and frost-free period (r=0.779) were well correlated to the uronic acid content, while the neutral carbohydrate content showed negative correlation with precipitation amount (r=-0.567). Antioxidative tests indicated that Fructus Jujubae polysaccharides could scavenge chemicals-induced reactive oxygen species in a dose-dependent manner. In addition, these polysaccharides could rescue H₂O₂-induced HUVEC death. The antioxidative activity of polysaccharides from the Fructus Jujubae might contribute to their diverse medicinal and nutritional values.

Investigation of three lignin complexes with antioxidant and immunological capacities from Inonotus obliquus

Mushroom Inonotus obliquus (I. obliquus), a folk medicine, has been widely used to treat several human malicious tumors since 16th century. In this study, three homogenous biomolecules (designated IOA1, IOA2 and IOA3) were prepared from the alkali extract of I. obliquus. Their molecular weights were measured to be 6.1 × 10(4), 2.9 × 10(4) and 3.5 × 10(4) g/mol respectively and all of them were characterized as lignin-carbohydrate complexes mainly comprised lignin as well as -25% carbohydrates. Antioxidant assays indicated that all of them exhibited pronounced reductive power and strong scavenging activities on DPPH and hydroxyl radicals in vitro. Immunological tests showed that they could also significantly stimulate nitric oxide production and phagocytic activity in RAW 264.7 macrophages. These results implied that the lignin-carbohydrate complexes extracted from I. obliquus might be used as novel natural antioxidants or immunostimulants in functional foods or pharmaceutical candidates.

Characterization of two water-soluble lignin metabolites with antiproliferative activities from Inonotus obliquus.

The chaga mushroom, Inonotus obliquus has long been recognized as a remedy for cancer, gastritis, ulcers, and tuberculosis of the bones since the 16th century. Herein we reported the identification of two homogenous biological macromolecules, designated as IOW-S-1 and IOW-S-2 with anti-tumor activities from the hot-water extract of I. obliquus. Their molecular weights were determined to be 37.9 and 24.5kDa by high performance gel permeation chromatography (HPGPC) respectively. Chemical and spectral analysis indicated that both IOW-S-1 and IOW-S-2 were predominant in lignin, along with ∼20% carbohydrates. Examination of cytotoxicity showed that these two lignin-carbohydrate complexes induced cell death in a concentration dependent manner, while this apoptosis induction was largely cell-cycle independent. Further investigation demonstrated that IOW-S-1 or IOW-S-2 inhibited the activation of the nuclear transcription factor in cancer cells. These findings implied that soluble lignin derivatives were one of bioactive components in I. obliquus, and further provided insights into the understanding of molecular basis for diverse medicinal and nutritional values of this mushroom.