Metal-phenolic networks spontaneously reinforced carrageenan-based packaging films with antibacterial and antioxidant properties.

The burdens of microbial food safety and environmental contamination make it necessary to search sustainable, safe, antibacterial and antioxidant active food packaging materials. This contribution proposed the use of copper-ferulic acid networks (CuFA NWs) as antibacterial substances. By immobilizing CuFA NWs into carrageenan matrix, a CuFA network-reinforced carrageenan-based packaging film (Carr/CuFA) was obtained via spontaneously hydrogen bond and electrostatic interaction indicated by ATR-IR and XPS. Interestingly, the addition of CuFA NWs increased the mechanical strength, surface hydrophobicity, and water vapor barrier properties of the carrageenan-based film, and imparted the film with UV-shielding capacity. Importantly, the Carr/CuFAx film exhibited effective antioxidant activity, and antibacterial performance against four foodborne bacteria. As a result, after confirming the safety of Carr/CuFA3 films by releasing, hemolysis and cell viability experiments, the Carr/CuFA3 film exhibited great potential in the safety control and preservation of fresh fruit by using blueberry and cherry as model fruit. In summary, this work provides a feasible candidate for the preservation and contamination control of fresh fruit.

Microenvironment-triggered cascade metal-polyphenolic nanozyme for ROS/NO synergistic hyperglycemic wound healing.

Wound infection of hyperglycemic patient often has extended healing period and increased probability due to the high glucose level. However, achieving precise and safe therapy of the hyperglycemic wound with specific wound microenvironment (WME) remains a major challenge. Herein, a WME-activated smart L-Arg/GOx@TA-Fe (LGTF) nanozymatic system composed of generally recognized as safe (GRAS) compound is engineered. The nanozymatic system combining metal-polyphenol nanozyme (tannic acid-Fe3+, TA-Fe) and natural enzyme (glucose oxidase, GOx) can consume the high-concentration glucose, generating reactive oxygen species (ROS) and nitric oxide (NO) in situ to synergistically disinfect hyperglycemia wound. In addition, glucose consumption and gluconic acid generation can lower glucose level to promote wound healing and reduce the pH of WME to enhance the catalytic activities of the LGTF nanozymatic system. Thereby, low-dose LGTF can perform remarkable synergistic disinfection and healing effect towards hyperglycemic wound. The superior biosafety, high catalytic antibacterial and beneficial WME regulating capacity demonstrate this benign GRAS nanozymatic system is a promising therapeutic agent for hyperglycemic wound.

pH-Responsive Co-Assembled Peptide Hydrogel to Inhibit Drug-Resistant Bacterial Infection and Promote Wound Healing.

Drug-resistant bacterial infection and biofilm formation are the key inhibitors of wound healing, and new strategies are urgently needed to address these issues. In this study, we designed a pH-responsive co-assembled peptide hydrogel to inhibit Methicillin-resistant Staphylococcus aureus (MRSA) infection and promote wound healing. We synthesized a cationic short peptide (Nap-FFKKK) and a co-assembled hydrogel with curcumin at pH ∼ 7.8. The loaded curcumin was continuously released in a weak acid environment (pH ∼ 5.5). The lysine-rich cationic peptide inhibited biofilm formation in MRSA via electrostatic interaction with the negatively charged bacterial cell surface and, thus, provided a reinforcing antibacterial effect with curcumin. In vitro antibacterial experiments showed that the co-assembled system considerably reduced the minimum inhibitory concentration of curcumin against MRSA by 10-fold and promoted wound healing in a mouse model of MRSA-infected wounds. This study provides a simple and promising strategy to treat drug-resistant bacterial infections in wounds.

O-Acetylation of Capsular Polysialic Acid Enables Escherichia coli K1 Escaping from Siglec-Mediated Innate Immunity and Lysosomal Degradation of E. coli-Containing Vacuoles in Macrophage-Like Cells.

Escherichia coli K1 causes bacteremia and meningitis in human neonates. The K1 capsule, an α2,8-linked polysialic acid (PSA) homopolymer, is its essential virulence factor. PSA is usually partially modified by O-acetyl groups. It is known that O-acetylation alters the antigenicity of PSA, but its impact on the interactions between E. coli K1 and host cells is unclear. In this study, a phase variant was obtained by passage of E. coli K1 parent strain, which expressed a capsule with 44% O-acetylation whereas the capsule of the parent strain has only 3%. The variant strain showed significantly reduced adherence and invasion to macrophage-like cells in comparison to the parent strain. Furthermore, we found that O-acetylation of PSA enhanced the modulation of trafficking of E. coli-containing vacuoles (ECV), enabling them to avoid fusing with lysosomes in these cells. Intriguingly, by using quartz crystal microbalance, we demonstrated that the PSA purified from the parent strain interacted with human sialic acid-binding immunoglobulin-like lectins (Siglecs), including Siglec-5, Siglec-7, Siglec-11, and Siglec-14. However, O-acetylated PSA from the variant interacted much less and also suppressed the production of Siglec-mediated proinflammatory cytokines. The adherence of the parent strain to human macrophage-like cells was significantly blocked by monoclonal antibodies against Siglec-11 and Siglec-14. Furthermore, the variant strain caused increased bacteremia and higher lethality in neonatal mice compared to the parent strain. These data elucidate that O-acetylation of K1 capsule enables E. coli to escape from Siglec-mediated innate immunity and lysosomal degradation; therefore, it is a strategy used by E. coli K1 to regulate its virulence. IMPORTANCE Escherichia coli K1 is a leading cause of neonatal meningitis. The mortality and morbidity of this disease remain significantly high despite antibiotic therapy. One major limitation on advances in prevention and therapy for meningitis is an incomplete understanding of its pathogenesis. E. coli K1 is surrounded by PSA, which is observed to have high-frequency variation of O-acetyl modification. Here, we present an in-depth study of the function of O-acetylation in PSA at each stage of host-pathogen interaction. We found that a high level of O-acetylation significantly interfered with Siglec-mediated bacterial adherence to macrophage-like cells, and blunted the proinflammatory response. Furthermore, the O-acetylation of PSA modulated the trafficking of ECVs to prevent them from fusing with lysosomes, enabling them to escape degradation by lysozymes within these cells. Elucidating how subtle modification of the capsule enhances bacterial defenses against host innate immunity will enable the future development of effective drugs or vaccines against infection by E. coli K1.

Immunoregulation and antioxidant activities of a novel acidic polysaccharide from Radix Paeoniae Alba.

Radix Paeoniae Alba is widely used in Chinese traditional medicine to treat various diseases such as gastrointestinal disorders, immunomodulatory, cancer, and other diseases. In this paper, a novel acidic polysaccharide RPAPS purified from Radix Paeoniae Alba was evaluated for its structural features and potential of immunomodulatory and antioxidant activities. RPAPS (molecular weight: 1.0× 105 Da) was mainly composed of α-(1 → 4)-Glcp, α-Arap, α-Galp, α-Rhap, ß-D-Glcp, α-(1 → 6)-linked Glcp and GalA. Immunological tests indicated that RPAPS could improve RAW264.7 phagocytic activity and LPS-induced splenocyte proliferation. For antioxidant activities, RPAPS showed reducing power and DPPH scavenging activity in dose dependent. Moreover, RPAPS could significantly protect the PC12 cells from H2O2 damage. These data implied polysaccharides RPAPS had the potential to be novel natural antioxidative and immunopotentiating agents for using in functional foods or medicine.

Preparation and biological activities of an extracellular polysaccharide from Rhodopseudomonas palustris.

The photosynthetic bacterium, Rhodopseudomonas palustris has been widely used as probiotics in aquaculture, while the molecular basis underlying the probiotic properties of this organism remains largely unknown. In this study, a novel extracellular polysaccharides (RPEPS-30) extracted from the fermentation of Rhodopseudomonas palustris was characterized. Results illustrated that RPEPS-30 was an α-mannan with a molecular weight of 46.82 kDa, which possessed a backbone consisted of 1, 2-linked and 1, 4-linked mannose residues, with side chains composed of 1 → 6 linked and 1 → 2,6 linked mannose residues and substitution at O-6. The in vitro immunomodulatory tests revealed that RPEPS-30 could enhance phagocytic capacity, NO release and mRNA expression of cytokines in macrophages. In addition, RPEPS-30 was shown to promote the growth of resident beneficial gut microbiotasuch as Lactobacillus reuteri, Bacteroides thetaiotaomicron and Akkermansia muciniphila. These findings might help us to partially understand the molecular mechanism concerning the probiotic properties of Rhodopseudomonas palustris, in which the extracellular polysaccharide RPEPS-30 stimulated host immune response and favored the growth of specific benificial micriobiota in the gut.

Protein-Bound ß-glucan from Coriolus Versicolor has Potential for Use Against Obesity.

SCOPE: The prevalence of obesity and related disorders has vastly increased throughout the world and prevention of such circumstances thus represents a major challenge. Here, it has been shown that one protein-bound ß-glucan (PBG) from the edible mushroom Coriolus versicolor can be a potent anti-obesity component. METHODS AND RESULTS: PBG can reduce obesity and metabolic inflammation in mice fed with a high-fat diet (HFD). Gut microbiota analysis reveals that PBG markedly increases the abundance of Akkermansia muciniphila, although it does not rescue HFD-induced change in the Firmicutes to Bacteroidetes ratio. It appears that PBG alters host physiology and creates an intestinal microenvironment favorable for A. muciniphila colonization. Fecal transplants from PBG-treated animals in part reduce obesity in recipient HFD-fed mice. Further, PBG is shown to upregulate expression of a set of genes related to host metabolism in microbiota-depleted mice. CONCLUSION: The data highlight that PBG may exert its anti-obesity effects through a mirobiota-dependent (richness of specific microbiota) and -independent (modulation of host metabolism) manner. The fact that C. versicolor PBGs are approved oral immune boosters in cancers and chronic hepatitis with well-established safety profiles may accelerate PBG as a novel use for obesity treatment.

A photo-controlled hyaluronan-based drug delivery nanosystem for cancer therapy.

In this paper, a novel photo-controlled drug-loaded nanomicelles were self-assembled by the amphiphile of hyaluronan-o-nitrobenzyl-stearyl chain (HA-NB-SC) with doxorubicin (DOX) encapsulated within the hydrophobic core. DOX-loaded HA-NB-SC nanomicelles are ∼139 nm in diameter. CD44-overexpressed HeLa cells can easily take up HA-NB-SC micelles through recognition of HA moiety. DOX-loaded HA-NB-SC nanomicelles could be disassembled upon UV light (365 nm) and consequently, release DOX at desired pathological sites. Furtherly, nitrosobenzaldehyde derivative, photo-induced products of HA-NB-SC and DOX could inhibit the proliferation of HeLa cells together. This strategy may shed some light on delivery of hydrophobic anti-cancer drugs in a controlled manner.

Light controllable chitosan micelles with ROS generation and essential oil release for the treatment of bacterial biofilm.

Bacterial biofilms are widely associated with persistent infections and food contamination. High resistance to conventional antimicrobial agents resulted in an urgent need for novel formulation to eliminate these bacterial communities. Herein we fabricated light controllable chitosan micelles loading with thymol (T-TCP) for elimination of biofilm. Due to the exterior chitosan, T-TCP micelles easily bind to negative biofilm through electrostatic interaction and efficiently deliver the essential oil payloads. Under irradiation, T-TCP micelles generated ROS, which triggered simultaneous thymol release and also resulted in additional ROS-inducing bactericidal effects, both effectively eradicating biofilms of Listeria monocytogenes and Staphylococcus aureus. This formulation provided a platform for other water-insoluble antimicrobials and might be used as a potent and controllable solution to biofilm fighting.

Antidepressant and immunosuppressive activities of two polysaccharides from Poria cocos (Schw.) Wolf.

Pursuit of novel effective antidepressants is an urgent task. Poria cocos (Schw.) Wolf (PCW) is a traditional herb with antidepressant effects. Polysaccharides designated PCWPW and PCWPS were purified from PCW by DEAE-52 cellulose chromatography. Their structures were characterized using physicochemical and spectral methods. Chemical analysis indicated that PCWPW (37,154 Da) and PCWPS (186,209 Da) were mainly composed of mannose, glucose, galactose and fucose. Their antidepressant activities were evaluated by tail suspension test (TST), forced swimming test (FST) with chronic unpredictable mild stress (CUMS) model mice. To investigate the antidepressant mechanism, the neuroprotective and immunomodulation effects were assessed by MTT method. Results showed that PCWPW and PCWPS possess obvious antidepressant effects and can suppress ConA-stimulated T cell proliferation in a dose-dependent manner. In addition, PCWPS could protect the PC12 cells from H2O2-induced damage and suppress LPS-induced B cell proliferation. These findings implied that PCWPW and PCWPS might be a candidate for developing antidepressant or immunosuppressive agents in food and pharmaceutical industries.

A hyaluronan-based nanosystem enables combined anti-inflammation of mTOR gene silencing and pharmacotherapy.

Accompanied by overproduction of oxidants and reduction of pH, inflammation is closely related to many diseases such as cancer, atherosclerosis, and asthma. Besides chemotherapeutic agents, the potential regulative role of autophagy in inflammation is being actively investigated. RNA interference (RNAi)-based gene therapy is widely explored for clinical therapy but seriously restricted by lack of suitable carriers. In this study, we synthesized a hyaluronan-based ROS-sensitive polymer which was expected to release loaded chemical drugs in inflammatory environment and further developed a stable and nontoxic co-delivery nanosystem of siRNA targeting autophagy suppressive gene and chemotherapeutic agents. The in vitro transfection study of this nanosystem revealed improved intracellular accumulation of siRNA and excellent gene silencing efficacy comparable to that of conventional cationic liposome. Moreover, the mRNA expression of inflammatory cytokines was remarkably decreased by our nanosystem. Considering its biocompatibility, transfection efficacy, and anti-inflammatory capability, this co-delivery nanosystem proclaimed to be a promising combined therapeutic strategy for enhanced anti-inflammatory therapy.

Kinetic control over supramolecular hydrogelation and anticancer properties of taxol.

We reported a kinetic control over supramolecular hydrogelation and more importantly over the anticancer properties of taxol.

Inulin based glutathione-responsive delivery system for colon cancer treatment.

Colorectal cancer is one of the most common types of tumor in the world. Here we developed a lipoic acid esterified polysaccharide (inulin) delivery system for tanshinone IIA to treat colorectal cancer in vitro. The release of tanshinone IIA in the system was highly responsive to glutathione, which is commonly abundant in cancer cells. In addition, this drug delivery system was proliferative to Bifidobacterium longum, the common inhabitant of human intestine. Thus, this strategy might be useful to improve colon cancer therapy efficacy of anticancer drugs and meanwhile promote the growth of beneficial commensal flora in the gut.

A novel photocleavable heparin derivative with light controllable anticoagulant activity.

Heparin (HP) has enormous potential for clinical medication applications owing to its anticoagulant activity. However, the strong anticoagulant capacity of HP also leads to some side effects. Herein, a photocaged derivative (HP-DMNB) of HP was synthesized for light control of its anticoagulant activity. The synthesized HP-DMNB was characterized by NMR and FTIR analysis, which confirmed the successful modification of HP with the photocleavable 4,5-dimethoxyl-2-nitrobenzyl (DMNB) groups. After the modification, the molecular weight of HP-DMNB (DS = 0.34%) changed from 61 to 71 kDa. Anticoagulant activity analysis showed that HP-DMNB had a reduced anticoagulant capacity compared with commercial HP, while its anticoagulant activity will regain after releasing the free carboxyl groups of HP under UV light. In addition, HP-DMNB and its UV irradiated products were observed to possess good biocompatibility through the MTT assays and live-dead assays with HaCaT cells, which may have impacts on the clinical medication applications of HP.

Synthesis, characterization and anticancer activity of tanshinone I grafted low molecular chitosan.

In this study, we synthesized a novel water-soluble low molecular chitosan (LMC) derivative through Vilsmeier reaction and reductive amination reaction. The derivative was characterized by UV-visible spectroscopy, 1H NMR, FTIR and SEM techniques. The results showed that the derivative effectively reduced the cell viability rate, inhibited cell metastasis, induced cell apoptosis and dissipated mitochondrial membrane potential (ΔΨm). Moreover, the antitumor activity was strengthened with the increase of the degree of substitution of tanshinone I (TanI). These findings provided important support for developing new water-soluble antitumor agent and expand the scope of application of LMC.

Autophagy promotes DNA-protein crosslink clearance.

Toxic DNA-protein crosslinks (DPCs) can result from exposure to radiation or chemotherapeutic agents. DPCs can also accumulate during aging or stress. However, the cellular mechanisms underlying clearance of DPCs remain largely unknown. Here, we have identified an important role of autophagy in the processing of DPCs induced by three representative agents: formaldehyde, a chemical used widely in industry; UV light; and camptothecin, a cytotoxic anticancer drug. Autophagy inhibitors, 3-methyladenine (3-MA) or chloroquine (CQ), promoted the accumulation of DPCs in damaged cells and injured organs. siRNA-mediated silencing of Atg5 or Atg7, two essential components for the formation of the autophagosome, gave similar results. In contrast, the autophagy inducer rapamycin (RAP) attenuated DPCs in vitro and in vivo. Our findings reveal the importance of autophagy in controlling the level of DPCs, and may open up a new avenue for understanding the formation and clearance of this detrimental DNA adduct.

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.

Structural characterization and biological activities of two α-glucans from radix paeoniae alba.

Radix Paeoniae Alba is widely used in Chinese traditional medicine to treat various diseases such as gastrointestinal disorders, cancer, and other diseases. In this study, two polysaccharides RPAPW1 and RPAPW2 were isolated from Radix Paeoniae Alba by DEAE-52 cellulose chromatography and G-25 sephadex. According to physicochemical methods, NMR and methylation analysis, RPAPW1 and RPAPW2 were established to be α-glucans consisting of predominant 4-linked α- Glc residues branched at O-6 and contained trace amount of protein and uronic acid. Immunological tests indicated that RPAPW1, RPAPW2 and could promote splenocyte proliferation and RAW264.7 phagocytic activity. In vitro, RPAPW1 and RPAPW2 elicited a week reducing power, DPPH scavenging activity and could not protect the PC12 cells from H2O2 damage. These data implied polysaccharides RPAPW1 and RPAPW2 had the potential to be a natural immunopotentiating and antioxidant supplement for preparing functional foods and nutraceuticals.

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.

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.