Chitosan derivatives killed bacteria by disrupting the outer and inner membrane

The Phage Holin HolGH15 Exhibits Potential As an Antibacterial Agent to Control Listeria monocytogenes

Listeria monocytogenes is an important foodborne pathogen that is a serious threat to public health security, and new strategies to control this bacterium in food are needed. HolGH15, derived from Staphylococcus aureus phage GH15, has shown antibacterial activity against several bacterial species. In this work, the antilisterial behavior and effectiveness of HolGH15 are further studied. To elucidate its antimicrobial modes against L. monocytogenes, cell integrity and membrane permeabilization assays were performed. When treated with HolGH15, the release of 260-nm-absorbing materials of L. monocytogenes was rapidly increased. HolGH15 triggered a significant increase in fluorescence intensity by flow cytometry. In membrane permeabilization assays, the cytoplasmic β-galactosidase of L. monocytogenes treated with HolGH15 was released via an increase in the permeability of the membrane. HolGH15 caused changes in the structural properties of L. monocytogenes cells resulting in shrinkage, which evoked the release and removal of cellular contents and finally lead to cell death. Electron microscopy observations indicated that HolGH15 exhibited excellent bactericidal potency by permeabilizing the cell membrane, damaging membrane integrity, and inducing cellular content shrinkage or loss. Moreover, HolGH15 (at the final concentration of 240 μg/mL) reduced L. monocytogenes (at the initial concentration of 10⁶ colony-forming unit/mL) to an undetectable level at 4°C. Collectively, HolGH15 has potential as a novel antimicrobial agent against L. monocytogenes in the manufacture and store of food by spraying or soaking, especially at refrigerated temperature.

Antibacterial activities of microwave-assisted synthesized polypyrrole/chitosan and poly (pyrrole-N-(1-naphthyl) ethylenediamine) stimulated by C-dots

Polypyrrole grafted with chitosan (PPy-g-CS) and poly (pyrrole-N-(1-naphthyl) ethylenediamine, a copolymer, (COP) have been synthesized by a one-step microwave procedure with carbon dots(C-Dots) as initiators. The electrostatic interaction between the positively charged polymers and negatively charged microbial cell membranes is widely anticipated to be responsible for cellular lysis. However, Escherichia coli exposed to PPy-g-CS (zeta potential = +46.9 mV) was completely perished after 3 h while COP (zeta potential = +64.1 mV) exhibited no antimicrobial effect. The two polymers were capable of eradicating Staphylococcus aureus, implying the charged effect is the main mechanism of cell death. The two polymers could also chelate calcium and other nutrients as well as form an external barrier to suppress the penetration of essential nutrients to support microbial survival and proliferation. In particular, pyrrole grafted chitosan was reasoned to stack onto the bacterial surface to impede the mass transfer and suppress the bacterial metabolic activity. The binding of chitosan to teichoic acids, essential acids of Gram-positive bacteria, would provoke a sequence of events and lead to bacterial death.

Injectable, self-healing, antibacterial, and hemostatic N,O-carboxymethyl chitosan/oxidized chondroitin sulfate composite hydrogel for wound dressing

Biodegradable and injectable hydrogels derived from natural polysaccharides have attracted extensive attention in biomedical applications due to their minimal invasiveness and ability to accommodate the irregular wound surfaces. In this work, we report the development of an in-situ-injectable, self-healing, antibacterial, hemostatic, and biocompatible hydrogel derived from the hybrid of N,O-carboxymethyl chitosan (N,O-CMC) and oxidized chondroitin sulfate (OCS), which did not require any chemical crosslinking. The N,O-CMC/OCS hydrogel could be readily produced under physiological conditions by varying the N,O-CMC-to-OCS ratio, relying on the Schiff base reaction between the -NH- functional groups of N,O-CMC and the -CHO functional groups of OCS. The results showed that the N,O-CMC2/OCS1 hydrogel had relatively long gelation time (133 s) and stable performances. The viability of NIH/3T3 cells and endothelial cells cultured with the N,O-CMC2/OCS1 hydrogel extract was roughly 85%, which demonstrated its low cell toxicity. Besides, the N,O-CMC2/OCS1 hydrogel revealed excellent antibacterial properties due to the inherent antibacterial ability of N,O-CMC. Importantly, the hydrogel tightly adhered to the biological tissue and demonstrated excellent in vivo hemostatic performance. Our work describing an injectable, self-healing, antibacterial, and hemostatic hydrogel derived from polysaccharides will likely hold good potential in serving as an enabling wound dressing material.

Carbohydrate polymers exhibit great potential as effective elicitors in organic agriculture: A review

Some carbohydrate polymers, usually oligosaccharides or polysaccharides, have great potential as an elicitor of plant defense. However, due to the complexity and diversity of poly- and oligosaccharide structure, the molecular mechanisms and structure-activity relationships of carbohydrate elicitors are still not well understood, which hinders the application of carbohydrate elicitors in agriculture. This review introduces the mechanisms of carbohydrate elicitor perception and signaling in plants. The structure and activity relationships of main poly- and oligosaccharides studied for the control of plant diseases are discussed and summarized. Additionally, the effects of carbohydrate elicitors on the secondary metabolite production are also summarized.

Chitosans for Tissue Repair and Organ Three-Dimensional (3D) Bioprinting

Chitosan is a unique natural resourced polysaccharide derived from chitin with special biocompatibility, biodegradability, and antimicrobial activity. During the past three decades, chitosan has gradually become an excellent candidate for various biomedical applications with prominent characteristics. Chitosan molecules can be chemically modified, adapting to all kinds of cells in the body, and endowed with specific biochemical and physiological functions. In this review, the intrinsic/extrinsic properties of chitosan molecules in skin, bone, cartilage, liver tissue repair, and organ three-dimensional (3D) bioprinting have been outlined. Several successful models for large scale-up vascularized and innervated organ 3D bioprinting have been demonstrated. Challenges and perspectives in future complex organ 3D bioprinting areas have been analyzed.

Nanomaterials as Delivery Vehicles and Components of New Strategies to Combat Bacterial Infections: Advantages and Limitations

Life-threatening bacterial infections have been well-controlled by antibiotic therapies and this approach has greatly improved the health and lifespan of human beings. However, the rapid and worldwide emergence of multidrug resistant (MDR) bacteria has forced researchers to find alternative treatments for MDR infections as MDR bacteria can sometimes resist all the present day antibiotic therapies. In this respect, nanomaterials have emerged as innovative antimicrobial agents that can be a potential solution against MDR bacteria. The present review discusses the advantages of nanomaterials as potential medical means and carriers of antibacterial activity, the types of nanomaterials used for antibacterial agents, strategies to tackle toxicity of nanomaterials for clinical applications, and limitations which need extensive studies to overcome. The current progress of using different types of nanomaterials, including new emerging strategies for the single purpose of combating bacterial infections, is also discussed in detail.

Fungal mediated biotransformation reduces toxicity of arsenic to soil dwelling microorganism and plant

Rhizospheric and plant root associated microbes generally play a protective role against arsenic toxicity in rhizosphere. Rhizospheric microbial interaction influences arsenic (As) detoxification/mobilization into crop plants and its level of toxicity and burden. In the present investigation, we have reported a rhizospheric fungi Aspergillus flavus from an As contaminated rice field, which has capability to grow at high As concentration and convert soluble As into As particles. These As particles showed a reduced toxicity to soil dwelling bacteria, fungi, plant and slime mold. It does not disrupt membrane potential, inner/outer membrane integrity and survival of the free N₂ fixating bacteria. In arbuscular mycorrhiza like endophytic fungi Piriformospora indica, these As particles does not influence mycelial growth and plant beneficial parameters such as phosphate solubilizing enzyme rAPase secretion and plant root colonization. Similarly, it does not affect plant growth and chlorophyll content negatively in rice plant. However, these As particles showed a poor absorption and mobilization in plant. These As particle also does not affect attachment process and survival of amoeboid cells in slime mold, Dictyostelium discoideum. This study suggests that the process of conversion of physical and chemical properties of arsenic during transformation, decides the toxicity of arsenic particles in the rhizospheric environment. This phenomenon is of environmental significance, not only in reducing arsenic toxicity but also in the survival of healthy living organism in arsenic-contaminated rhizospheric environment.

Prospective randomized single-blind study of post-operative bleeding after minor oral surgery in patients with cirrhosis

BACKGROUND/AIMS

The management of patients with cirrhosis requiring dental extractions is complicated due to an increased risk of post-operative bleeding. Topical hemostatic agents are usually required to control bleeding in these cases, as an adjunct to systemic measures of hemostasis. The aims of this randomized, prospective, single-blind clinical study are twofold. The primary aim is to compare the hemostatic efficacy of chitosan and surgicel in patients with cirrhosis after a tooth extraction, and the secondary aim is to assess the value of the current setting as a clinical model of post-operative bleeding following minor oral surgery.

MATERIAL AND METHODS

Fifty patients with cirrhosis scheduled for a tooth extraction under local anesthesia were prospectively included in the study in a randomized fashion. Patients were blinded to the treatment group they were in. The cirrhosis classification, bleeding time, trauma score, and corrected bleeding time (during post-operative reviews) were recorded. Statistical evaluations were done.

RESULTS

Study groups had an equal number of teeth extractions (40 teeth each). There were no statistically significant differences between the groups with respect to patient demographics, cirrhosis classification, trauma score, and bleeding time. No side effects were noted.

CONCLUSION

Both Celox and Surgicel are effective for controlling bleeding and are safe after a tooth extraction in patients with cirrhosis.

The Effects of Various Hemostatic Agents on Shear-bond Strength in Primary Teeth: An In Vitro Study

Aims and objectives:

The aim of this study was to determine the effects of chitosan, Ankaferd Blood Stopper® (ABS, Ankaferd Health Products Ltd, Turkey), and ferric sulfate (FS) on the shear-bond strength of the self-etch adhesive to primary tooth dentin.

Materials and methods:

The occlusal surfaces of 80 extracted human primary teeth (stored in a 0.5% chloramine-T solution at 4oC) were ground flat, exposing the dentin. The teeth were divided into 4 groups: chitosan, ABS, FS, and control. Hemostatic agents were applied to the teeth, and then they were rinsed with distilled water and air dried. In the control group, the teeth were only rinsed with distilled water and slightly air dried. A self-etch adhesive was applied, and the composite cylinder was created on all the samples. Shear-bond strength was tested with a universal testing machine. Failure mode analysis was performed using scanning electron microscopy.

Results:

The study revealed no statistically significant difference between the hemostatic agent and control groups in terms of bond strength ( P >.05). The highest bond strength was observed in the chitosan group. In this group, a statistically significant difference between chitosan and ABS was observed ( P <.05). The adhesive failure was the predominant failure mode in all the groups.

Conclusions:

These findings suggest that chitosan, ABS, and FS have no adverse effects on the bonding of the self-etch adhesive to primary teeth dentin.

Antimicrobial activity of the biopolymer chitosan against Streptococcus iniae

The antimicrobial activity and mode of action of chitosan were evaluated against Streptococcus iniae, a pathogenic Gram-positive bacterium of fish worldwide. Cell proliferation kinetics were examined following exposure to varying concentrations of chitosan. The action of chitosan on S. iniae was also investigated by measuring agglutination activity, conductivity, and extracellular and intracellular bacterial adenosine triphosphate (ATP) levels. Chitosan exhibited antibacterial activity against S. iniae at concentrations of 0.1% and above and was lethal at a concentration of 0.4% and higher. The mechanism of antibacterial activity of chitosan at the inhibitory level of bacterial growth appears to hinge upon the interaction between chitosan and the oppositely charged bacterial surface. This interplay causes agglutination, which was readily observed grossly and microscopically. After interacting with the cell surface via adsorption, an efflux of intracellular ATP was documented, which suggests that chitosan disrupts the bacterial cell causing leakage of cytosolic contents and ultimately cell death. Results suggest chitosan may be worth evaluating as a natural alternative to antibiotic against S. iniae infection of fish.

Enhancement of biocatalyst activity and protection against stressors using a microbial exoskeleton

Whole cell biocatalysts can perform numerous industrially-relevant chemical reactions. While they are less expensive than purified enzymes, whole cells suffer from inherent reaction rate limitations due to transport resistance imposed by the cell membrane. Furthermore, it is desirable to immobilize the biocatalysts to enable ease of separation from the reaction mixture. In this study, we used a layer-by-layer (LbL) self-assembly process to create a microbial exoskeleton which, simultaneously immobilized, protected, and enhanced the reactivity of a whole cell biocatalyst. As a proof of concept, we used Escherichia coli expressing homoprotocatechuate 2,3-dioxygenase (HPCD) as a model biocatalyst and coated it with up to ten alternating layers of poly(diallyldimethylammonium chloride) (PDADMAC) and silica. The microbial exoskeleton also protected the biocatalyst against a variety of external stressors including: desiccation, freeze/thaw, exposure to high temperatures, osmotic shock, as well as against enzymatic attack by lysozyme, and predation by protozoa. While we observed increased permeability of the outer membrane after exoskeleton deposition, this had a moderate effect on the reaction rate (up to two-fold enhancement). When the exoskeleton construction was followed by detergent treatment to permeabilize the cytoplasmic membrane, up to 15-fold enhancement in the reaction rate was reached. With the exoskeleton, we increased in the reaction rate constants as much as 21-fold by running the biocatalyst at elevated temperatures ranging from 40 °C to 60 °C, a supraphysiologic temperature range not accessible by unprotected bacteria.

The effect of halogenation on the antimicrobial activity, antibiofilm activity, cytotoxicity and proteolytic stability of the antimicrobial peptide Jelleine-I

Antimicrobial peptides (AMPs) are believed to be a promising class of antimicrobial agents against bacteria and fungi. To promote the clinical use of AMPs, their antimicrobial activity and susceptibility to protease degradation should be further improved. The antimicrobial peptide Jelleine-I was originally isolated from the royal jelly of honeybees (Apis mellifera) with a short sequence of PFKLSLHL-NH₂ (953.24 Da). Here, a series of halogenated derivatives of the antimicrobial peptide Jelleine-I were designed and synthesized. The results showed that the in vitro antimicrobial activity, antibiofilm activity and in vivo antimicrobial efficacy were enhanced 1-8-fold after halogenation. Additionally, the proteolytic stability of Jelleine-I was improved 10-100-fold by halogenation. Meanwhile, the halogenated derivatives retained negligible hemolytic activity and cytotoxicity. Among these derivatives, the antimicrobial activity and antibiofilm activity of chlorine-Jelleine-I (Cl-J-I), bromine-Jelleine-I (Br-J-I), and iodine-Jelleine-I (I-J-I) were better than those of fluorine-Jelleine-I (F-J-I). The stabilities of Br-J-I and I-J-I against the degradation of enzymes and the serum were better than those of F-J-I and Cl-J-I. In conclusion, this study may offer a useful strategy to enhance antimicrobial efficacy and proteolytic stability by halogenation. The halogenated derivatives Cl-J-I, Br-J-I and I-J-I may be considered as potential antimicrobial agents against microbial infection.

Prussian blue-encapsulated Fe3O4 nanoparticles for reusable photothermal sterilization of water

Waterborne health issues continue to grow despite the large number of available solutions. Current sterilization techniques to fight with waterborne diseases struggle to meet the demands on cost, efficiency and reach. Effective alternatives are pressingly required. Here we introduce Prussian blue coated ferroferric oxide (Fe₃O₄@PB) composites for water sterilization. The composites exhibit superior photothermal inactivation of bacteria under solar-light irradiation, with nearly complete inactivation of bacterial cells in only 15 min. Even for the mixed bacteria in authentic water matrices, the composites show excellent bacterial inactivation performance. Moreover, the highly magnetized iron core of the Fe₃O₄@PB enables magnetic separation and recycling. Multiple cycle runs reveal that Fe₃O₄@PB composites have exceptional stability and reusability. This work demonstrates a scalable, low-cost, high-efficiency and reusable sterilization method to improve water quality and safety.

Molecular Mechanisms of Chitosan Interactions with Fungi and Plants

Chitosan is a versatile compound with multiple biotechnological applications. This polymer inhibits clinically important human fungal pathogens under the same carbon and nitrogen status as in blood. Chitosan permeabilises their high-fluidity plasma membrane and increases production of intracellular oxygen species (ROS). Conversely, chitosan is compatible with mammalian cell lines as well as with biocontrol fungi (BCF). BCF resistant to chitosan have low-fluidity membranes and high glucan/chitin ratios in their cell walls. Recent studies illustrate molecular and physiological basis of chitosan-root interactions. Chitosan induces auxin accumulation in Arabidopsis roots. This polymer causes overexpression of tryptophan-dependent auxin biosynthesis pathway. It also blocks auxin translocation in roots. Chitosan is a plant defense modulator. Endophytes and fungal pathogens evade plant immunity converting chitin into chitosan. LysM effectors shield chitin and protect fungal cell walls from plant chitinases. These enzymes together with fungal chitin deacetylases, chitosanases and effectors play determinant roles during fungal colonization of plants. This review describes chitosan mode of action (cell and gene targets) in fungi and plants. This knowledge will help to develop chitosan for agrobiotechnological and medical applications.

Chitosan Grafted With β-Cyclodextrin: Synthesis, Characterization, Antimicrobial Activity, and Role as Absorbefacient and Solubilizer

We synthesized chitosan grafted with β-cyclodextrin (CD-g-CS) from mono-6-deoxy-6-(p-toluenesulfonyl)-β-cyclodextrin and chitosan. Two different amounts of immobilized β-cyclodextrin (β-CD) on CD-g-CS (Q_CD: 0.643 × 10³ and 0.6 × 10² μmol/g) were investigated. The results showed that the amino contents of CD-g-CS with Q_CD = 0.643 × 10³ and 0.6 × 10² μmol/g were 6.34 ± 0.072 and 9.41 ± 0.055%, respectively. Agar diffusion bioassay revealed that CD-g-CS (Q_CD = 0.6 × 10² μmol/g) was more active against Staphylococcus xylosus and Escherichia coli than CD-g-CS (Q_CD = 0.643 × 10³ μmol/g). Cell membrane integrity tests and scanning electron microscopy observation revealed that the antimicrobial activity of CD-g-CS was attributed to membrane disruption and cell lysis. Uptake tests showed that CD-g-CS promoted the uptake of doxorubicin hydrochloride by S. xylosus, particularly for CD-g-CS with Q_CD = 0.6 × 10² μmol/g, and the effect was concentration dependent. CD-g-CS (Q_CD = 0.6 × 10² and 0.643 × 10³ μmol/g) also improved the aqueous solubilities of sulfadiazine, sulfamonomethoxine, and sulfamethoxazole. These findings provide a clear understanding of CD-g-CS and are of great importance for reducing the dosage of antibiotics and antibiotic residues in animal-derived foods. The results also provide a reliable, direct, and scientific theoretical basis for its wide application in the livestock industry.

Structure and dynamics of gold nanoparticles decorated with chitosan–gentamicin conjugates: ReaxFF molecular dynamics simulations to disclose drug delivery

Functionalized gold nanoparticles for antibiotic drug delivery: from the nanoscale to the atomic scale.

Selective Targeting of 4SO4-N-Acetyl-Galactosamine Functionalized Mycobacterium tuberculosis Protein Loaded Chitosan Nanoparticle to Macrophages: Correlation With Activation of Immune System

In the present study, we investigated potential of chitosan-based nanoparticles (CNPs) to deliver loaded therapeutic molecules to pathogen harboring macrophages. We fabricated stable CNPs employing ionic cross-linking method and evaluated their potential to target RAW 264.7 cells. The physicochemical characterization of as-synthesized CNPs was determined using electron microscopy, infrared microscopy and zeta potential measurement. Next, cellular uptake and intracellular localization studies of CNPs were followed in living RAW264.7 cells using confocal microscopy. We found that both Acr-1 loaded (CNP-A) and 4-SO₄-GalNAc ligand harboring (CNP-L) chitosan nanoparticle experience increased cellular uptake by Mycobacterium smegmatis infected RAW cells. Following cellular digestion in model macrophage cell line (RAW), CNPs provide an increased immune response. Further, 4-SO₄-GalNAc bearing CNP-L exhibits high binding affinity as well as antibacterial efficacy toward M. smegmatis. The data of the present study suggest that CNP-based nanoparticle offer a promising delivery strategy to target infected macrophages for prevention and eradication of intracellular pathogens such as M. smegmatis.

Prospective randomized single-blind study of post-operative bleeding after minor oral surgery in patients with cirrhosis

BACKGROUND/AIMS

The management of patients with cirrhosis requiring dental extractions is complicated due to an increased risk of post-operative bleeding. Topical hemostatic agents are usually required to control bleeding in these cases, as an adjunct to systemic measures of hemostasis. The aims of this randomized, prospective, single-blind clinical study are twofold. The primary aim is to compare the hemostatic efficacy of chitosan and surgicel in patients with cirrhosis after a tooth extraction, and the secondary aim is to assess the value of the current setting as a clinical model of post-operative bleeding following minor oral surgery.

MATERIAL AND METHODS

Fifty patients with cirrhosis scheduled for a tooth extraction under local anesthesia were prospectively included in the study in a randomized fashion. Patients were blinded to the treatment group they were in. The cirrhosis classification, bleeding time, trauma score, and corrected bleeding time (during post-operative reviews) were recorded. Statistical evaluations were done.

RESULTS

Study groups had an equal number of teeth extractions (40 teeth each). There were no statistically significant differences between the groups with respect to patient demographics, cirrhosis classification, trauma score, and bleeding time. No side effects were noted.

CONCLUSION

Both Celox and Surgicel are effective for controlling bleeding and are safe after a tooth extraction in patients with cirrhosis.

Recent advances in chitosan polysaccharide and its derivatives in antimicrobial modification of textile materials

Chitosan is partially or completely N-deacetylated derivative of chitin and is chemically composed of β‑(1, 4) linked 2‑amino‑2‑deoxy‑β‑d‑glucopyranose. Biocompatibility, non-toxicity, antifungal activity, water-binding capacity, bioactivity and antimicrobial properties make chitosan particularly attractive substitute for synthetic polymers in different application fields and notably in the textile industry. The presence of reactive amino and hydroxyl groups along the backbone conifer chitosan some interesting properties for use in textile dyeing and finishing. However, the main barrier to the use of chitosan is the lack of water solubility at neutral pH and poor durability on textile surfaces. To overcome this, chitosan has been chemically modified in several ways to obtain a wide range of important derivatives with a broad range of applications. This review is intended to provide a recent overview of chitosan and its derivatives and highlight their role in the development of antimicrobial textiles.

Straw Wine Melanoidins as Potential Multifunctional Agents: Insight into Antioxidant, Antibacterial, and Angiotensin-I-Converting Enzyme Inhibition Effects

Numerous studies provide robust evidence for a protective effect of red wine against many diseases. This bioactivity has been mainly associated with phenolic fractions of wines. However, the health effects of melanoidins in red sweet wines has been ignored. The goal of the present work was to unravel the antioxidant, antimicrobial, and angiotensin-I-converting enzyme (ACE) inhibitory properties of straw sweet wine melanoidins. Results demonstrated that melanoidins have a potential antioxidant activity, determined by 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and Ferric reducing antioxidant power (FRAP) assays. The antimicrobial activity of melanoidins was also tested against Listeria monocytogenes, Salmonella Enteritidis, and Escherichia coli. Minimum inhibitory concentration (MIC) of isolated melanoidins against three bacterial strains ranged from 5 mg mL⁻¹ to 10 mg mL⁻¹. Finally, the ACE inhibitory effect of isolated melanoidins was evaluated, as it is linked with antihypertensive activity. Results showed that they have ACE-inhibitory activity ranging from 58.2 ± 5.4% to 75.3 ± 6.4% at a concentration level of 2 mg mL⁻¹. Furthermore, the chemical properties of isolated melanoidins were determined. Results demonstrated that the skeleton of straw wine melanoidins is mainly composed of carbohydrates, and bear significant numbers of phenolic compounds that may play critical roles in their functional properties. Overall, this study describing the chemical composition and functional properties of melanoidin fractions isolated from a straw wine highlights that they can be exploited as functional agents for multiple purposes. Finally, melanoidins are an unexplored source of bioactive molecules in straw wines except from polyphenols that contribute to the health effects.

Morphology, electrokinetic characteristics and the effect on biofilm formation of carrageenan:chitosan polyelectrolyte complexes

Carrageenan:chitosan (CG:CH) polyelectrolyte complexes (PEC) were obtained and the effect of the initial components ratio on formation was studied by dynamic light scattering, atomic force microscopy (AFM) and electrokinetic measurements. Positively charged PEC particles (average ζ-potential 40.2 mV) were formed, provided that the polycation was present in excess in the complex and was stabilized by chitosan amino groups. According to the AFM data, chitosan was located on the surface of the carrageenan fibers. In PEC where carrageenan prevailed, the number of unbound sulfate groups decreased when the chitosan content increased, this resulted in a decrease in the PEC negative surface charge (from -92.4 to -55.6 mV). In this case, AFM showed that chitosan was incorporated into the network structure of carrageenan and breaks it at a CG:CH ratio of 1:0.5 w/w. Complexes with a high content of kappa-CG inhibited biofilm formation by Gram negative and Gram positive microorganisms.

Antibacterial activity of polyphenolic fraction of Kombucha against Vibrio cholerae: targeting cell membrane

The present study was undertaken to determine the mechanism of antibacterial activity of a polyphenolic fraction, composed of mainly catechin and isorhamnetin, previously isolated from Kombucha, a 14-day fermented beverage of sugared black tea, against the enteropathogen Vibrio cholerae N16961. Bacterial growth was found to be seriously impaired by the polyphenolic fraction in a dose-dependent manner. Scanning Electron Microscopy demonstrated morphological alterations in bacterial cells when exposed to the polyphenolic fraction in a concentration-dependent manner. Permeabilization assays confirmed that the fraction disrupted bacterial membrane integrity in both time- and dose-dependent manners, which were proportional to the production of intracellular reactive oxygen species (ROS). Furthermore, each of the polyphenols catechin and isorhamnetin showed the ability to permeate bacterial cell membranes by generating oxidative stress, thereby suggesting their role in the antibacterial potential of Kombucha. Thus, the basic mechanism of antibacterial activity of the Kombucha polyphenolic fraction against V. cholerae involved bacterial membrane permeabilization and morphological changes, which might be due to the generation of intracellular ROS. To the best of our knowledge, this is the first report on the investigation of antibacterial mechanism of Kombucha, which is mostly attributed to its polyphenolic content.

SIGNIFICANCE AND IMPACT OF THE STUDY

The emergence of multidrug-resistant Vibrio cholerae strains has hindered an efficient anti-Vibrio therapy. This study has demonstrated the membrane damage-mediated antibacterial mechanism of Kombucha, a popular fermented beverage of sugared tea, which is mostly attributed to its polyphenolic content. This study also implies the exploitation of Kombucha as a potential new source of bioactive polyphenols against V. cholerae.

Synthesis, characterization, and antifungal evaluation of diethoxyphosphoryl polyaminoethyl chitosan derivatives

Botrytis cinerea, Phytophthora capsici Leonian, and Fusarium solani are important plant pathogenic fungi which can cause great crop losses worldwide, but their control methods are limited. It is necessary to develop efficient and green fungicides from abundant marine resources. Chitosan is a non-toxic, biodegradable, biocompatible marine polysaccharide which has prospective applications in agriculture. In this paper, to increase the antifungal activity of chitosan for application, novel water-soluble functional chitosan derivatives were synthesized by grafting polyaminoethyl and diethoxyphosphoryl groups in accordance with a strategy of improving protonation potential. The derivatives were characterized by FTIR, NMR, XRD, SEM, Gaussian 09 and elemental analysis. The antifungal activities against the three fungi and the cytotoxicity were estimated in vitro. The results showed that the derivatives had better antifungal activities and water solubility than chitosan, and had good biocompatibility. They confirmed that these chitosan derivatives can be developed as antifungal agents for plant protection purposes.

Antibacterial activity and mode of action of totarol against Staphylococcus aureus in carrot juice

Food contaminated with pathogenic bacteria such as Staphylococcus aureus (S. aureus), represents a serious health risk to human beings. Totarol is an antibacterial novel phenolic diterpenes. In present study, the antibacterial activity of totarol against S. aureus was investigated in a food system. The antibacterial activity of totarol was determined by measuring the zones of inhibition and minimum inhibitory concentrations (MICs). The MICs for S. aureus strains were in the range of 2-4 μg/ml. The probable antibacterial mechanism of totarol was the alteration in cell membranes integrity and permeability, which leading to the leakage of cellular materials. The electric conductivity showed a time- and dose-dependent increasing manner, and we utilized totarol to induce the production of cytoplasmic β-galactosidase in S. aureus. Scanning electron microscopy and transmission electron microscopy analysis further confirmed that S. aureus cell membranes were damaged by totarol. The time-kill assay and detection of the kinetics of S. aureus deactivation in situ indicated that totarol has good preservative activities in a food model. Totarol successfully inhibited S. aureus development in carrot juice, at room temperature (25 °C) and in refrigerator (4 °C) respectively. Our works provided not only additional evidences in support of totarol being regarded as a natural antibacterial food preservative but also fundamental understanding on the mode of antibacterial action. It is necessary to consider that totarol will become a promising antibacterial additive for food preservative.

Tacrolimus nanoparticles based on chitosan combined with nicotinamide: enhancing percutaneous delivery and treatment efficacy for atopic dermatitis and reducing dose

Background

Topical application of tacrolimus (FK506) was effective in the treatment of atopic dermatitis (AD); however, adverse effects frequently occurred with the increase of FK506 dose during long–term treatment.

Objective

The objective of this project was to develop a hybrid skin targeting system encapsulating FK506 based on nicotinamide (NIC) and chitosan nanoparticles (CS–NPs), ie, FK506–NIC–CS–NPs, which took advantages of both of NIC and CS–NPs to obtain the synergetic effects of percutaneous delivery and treatment efficacy enhancement along with dose reduction.

Methods

The formulation of FK506–NIC–CS–NPs was optimized and characterized. In vitro and in vivo skin permeation studies were performed. AD–like skin lesions were constructed with BALB/c mice by 1–chloro–2, 4–dinitrobenzene (DNCB)–induced, and FK506–NIC–CS–NPs containing different dose of FK506 were topically administered to treat AD–like skin lesions in comparison with Protopic.

Results

NIC was found to significantly increase the FK506 EE to 92.2% by CS–NPs. In comparison with commercial FK506 ointment (Protopic), in vitro and in vivo skin permeation studies demonstrated that NIC–CS–NPs system significantly enhanced FK506 permeation through and into the skin, and deposited more FK506 into the skin. The treatment efficacy on clinical symptoms, histological analysis, and molecular biology of the AD–mice demonstrated that NIC–CS–NPs with ~1/3 dose of FK506 of Protopic was superior to that of Protopic, and NIC–CS–NPs vehicle exhibited the adjuvant therapy and moderate anti–AD effects.

Conclusion

The system of NIC–CS–NPs enhances the permeability of FK506, plays an adjuvant role in anti-AD, reduces the dose of FK506 in treating AD, and is therefore a promising nanoscale system of FK506 for the effective treatment of AD.

Chitosan-based coatings in the prevention of intravascular catheter-associated infections

Central venous access devices play an important role in patients with prolonged intravenous administration requirements. In the last years, the coating of these devices with bactericidal compounds has emerged as a potential tool to prevent bacterial colonization. Our study describes the modification of 3D-printed reservoirs and silicone-based catheters, mimicking central venous access devices, through different approaches including their coating with the well known biocompatible and bactericidal polymer chitosan, with the anionic polysaccharide alginate; also, plasma treated surfaces were included in the study to promote polymer adhesion. The evaluation of the antimicrobial action of those surface modifications compared to that exerted by a model antibiotic (ciprofloxacin) adsorbed on the surface of the devices was carried out. Surface characterization was developed by different methodologies and the bactericidal effects of the different coatings were assayed in an in vitro model of Staphylococcus aureus infection. Our results showed a significant reduction in the reservoir roughness (≤73%) after coating though no changes were observed for coated catheters which was also confirmed by scanning electron microscopy, pointing to the importance of the surface device topography for the successful attachment of the coating and for the subsequent development of bactericidal effects. Furthermore, the single presence of chitosan on the reservoirs was enough to fully inhibit bacterial growth exerting the same efficiency as that showed by the model antibiotic. Importantly, chitosan coating showed low cytotoxicity against human keratinocytes, human lung adenocarcinoma epithelial cells, and murine colon carcinoma cells displaying viability percentages in the range of the control samples (>95%). Chitosan-based coatings are proposed as an effective and promising solution in the prevention of microbial infections associated to medical devices.

Emerging nanotechnology based strategies for diagnosis and therapeutics of urinary tract infections: A review

At present, various diagnostic and therapeutic approaches are available for urinary tract infections. But, still the quest for development of more rapid, accurate and reliable approach is an unending process. The pathogens, especially uropathogens are adapting to new environments and antibiotics day by day rapidly. Therefore, urinary tract infections are evolving as hectic and difficult to eradicate, increasing the economic burden to the society. The technological advances should be able to compete the adaptability characteristics of microorganisms to combat their growth in new environments and thereby preventing their infections. Nanotechnology is at present an extensively developing area of immense scientific interest since it has diverse potential applications in biomedical field. Nanotechnology may be combined with cellular therapy approaches to overcome the limitations caused by conventional therapeutics. Nanoantibiotics and drug delivery using nanotechnology are currently growing areas of research in biomedical field. Recently, various categories of antibacterial nanoparticles and nanocarriers for drug delivery have shown their potential in the treatment of infectious diseases. Nanoparticles, compared to conventional antibiotics, are more beneficial in terms of decreasing toxicity, prevailing over resistance and lessening costs. Nanoparticles present long term therapeutic effects since they are retained in body for relatively longer periods. This review focuses on recent advances in the field of nanotechnology, principally emphasizing diagnostics and therapeutics of urinary tract infections.

Preparation, characterization, and evaluation of 3,6-O-N-acetylethylenediamine modified chitosan as potential antimicrobial wound dressing material

This work aims to prepare 3,6-O-N-acetylethylenediamine modified chitosan (AEDMCS) and evaluate its potential use as an antimicrobial wound dressing material. UV, FTIR, and ¹H NMR results demonstrated N-acetylethylenediamine groups were successfully grafted to C3OH and C6OH on polysaccharide skeletons. TGA, XRD, and solubility tests indicated that as compared with chitosan, AEDMCS had diminished thermostability, decreased crystallinity, and greatly improved solubility. AEDMCS, with degrees of deacetylation and substitution being respectively 90.3% and 0.72, exhibited higher antibacterial activity than chitosan against six bacteria generally causing wound infections. Meanwhile, AEDMCS had permissible hemolysis and cytotoxicity and low BSA adsorption even at a AEDMCS concentration of 25mg/mL. Acute toxicity tests showed AEDMCS was nontoxic. Moreover, the wound healing property was preliminarily evaluated, illustrating that AEDMCS enhanced wound healing rates as expected and had no significant differences as compared with chitosan. These results suggested AEDMCS might be a potential material used as antibacterial wound dressings.

Single Continuous Near-Infrared Laser-Triggered Photodynamic and Photothermal Ablation of Antibiotic-Resistant Bacteria Using Effective Targeted Copper Sulfide Nanoclusters

The emergence of antibiotic-resistant bacterial strains has made conventional antibiotic therapies less efficient. The development of a novel nanoantibiotic approach for efficiently ablating such bacterial infections is becoming crucial. Herein, a collection of poly(5-(2-ethyl acrylate)-4-methylthiazole-g-butyl)/copper sulfide nanoclusters (PATA-C4@CuS) was synthesized for efficient capture and effective ablation of levofloxacin-resistant Gram-negative and Gram-positive bacteria upon tissue-penetrable near-infrared (NIR) laser irradiation. In this work, we took advantage of the excellent photothermal and photodynamic properties of copper sulfide nanoparticles (CuSNPs) upon NIR laser irradiation and thiazole derivative as a membrane-targeting cationic ligand toward bacteria. The conjugated nanoclusters could anchor the bacteria to trigger the bacterial aggregation quickly and efficiently kill them. These conjugated nanoclusters could significantly inhibit levofloxacin-resistant Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Bacillus amyloliquefaciens at 5.5 μg/mL under NIR laser irradiation (980 nm, 1.5 W cm^-2, 5 min), which suggested that the heat and reactive oxygen species (ROS) generated from the irradiated CuSNPs attached to bacteria were effective in eliminating and preventing the regrowth of the bacteria. Importantly, the conjugated nanoclusters could promote healing in bacteria-infected rat wounds without nonspecific damage to normal tissue. These findings highlight the promise of the highly versatile multifunctional nanoantibiotics in bacterial infection.

Mechanisms of Antimicrobial Action of Cinnamon and Oregano Oils, Cinnamaldehyde, Carvacrol, 2,5-Dihydroxybenzaldehyde, and 2-Hydroxy-5-Methoxybenzaldehyde against Mycobacterium avium subsp. paratuberculosis (Map)

The antimicrobial modes of action of six naturally occurring compounds, cinnamon oil, cinnamaldehyde, oregano oil, carvacrol, 2,5-dihydroxybenzaldehyde, and 2-hydroxy-5-methoxybenzaldehyde, previously found to inhibit the growth of Mycobacterium avium subsp. paratuberculosis (Map) reported to infect food animals and humans and to be present in milk, cheese, and meat, were investigated. The incubation of Map cultures in the presence of all six compounds caused phosphate ions to leak into the extracellular environment in a time- and concentration-dependent manner. Cinnamon oil and cinnamaldehyde decreased the intracellular adenosine triphosphate (ATP) concentration of Map cells, whereas oregano oil and carvacrol caused an initial decrease of intracellular ATP concentration that was restored gradually after incubation at 37 °C for 2 h. Neither 2,5-dihydroxybenzaldehyde nor 2-hydroxy-5-methoxybenzaldehyde had a significant effect on intracellular ATP concentration. None of the compounds tested were found to cause leakage of ATP to the extracellular environment. Monolayer studies involving a Langmuir trough apparatus revealed that all anti-Map compounds, especially the essential oil compounds, altered the molecular packing characteristics of phospholipid molecules of model membranes, causing fluidization. The results of the physicochemical model microbial membrane studies suggest that the destruction of the pathogenic bacteria might be associated with the disruption of the bacterial cell membrane.