Spray-by-spray in situ cross-linking alginate hydrogels delivering a tea tree oil microemulsion

Chitosan-Oxidized Pullulan Hydrogels Loaded with Essential Clove Oil: Synthesis, Characterization, Antioxidant and Antimicrobial Properties

Emulsion hydrogels are promising materials for encapsulating and stabilizing high amounts of hydrophobic essential oils in hydrophilic matrices. In this work, clove oil-loaded hydrogels (CS/OP-C) are synthesized by combining covalent and physical cross-linking approaches. First, clove oil (CO) was emulsified and stabilized in a chitosan (CS) solution, which was further hardened by Schiff base covalent cross-linking with oxidized pullulan (OP). Second, the hydrogels were subjected to freeze-thaw cycles and, as a result, the clove oil was stabilized in physically cross-linked polymeric walls. Moreover, due to cryogelation, the obtained hydrogels exhibited sponge-like porous interconnected morphology (160-250 µm). By varying the clove oil content in the starting emulsion and the degree of cross-linking, the hydrogels displayed a high water retention capacity (swelling ratios between 1300 and 2000%), excellent elastic properties with fast shape recovery (20 s) after 70% compression, and controlled in vitro clove oil release in simulated skin conditions for 360 h. Furthermore, the prepared clove oil-loaded hydrogels had a strong scavenging activity of 83% and antibacterial and antifungal properties, showing a bacteriostatic effect after 48 and 72 h against S. aureus and E. coli. Our results recommend the new clove oil-embedded emulsion hydrogels as promising future materials for application as wound dressings.

Advanced function, design and application of skin substitutes for skin regeneration

The development of skin substitutes aims to replace, mimic, or improve the functions of human skin, regenerate damaged skin tissue, and replace or enhance skin function. This includes artificial skin, scaffolds or devices designed for treatment, imitation, or improvement of skin function in wounds and injuries. Therefore, tremendous efforts have been made to develop functional skin substitutes. However, there is still few reports systematically discuss the relationship between the advanced function and design requirements. In this paper, we review the classification, functions, and design requirements of artificial skin or skin substitutes. Different manufacturing strategies for skin substitutes such as hydrogels, 3D/4D printing, electrospinning, microfluidics are summarized. This review also introduces currently available skin substitutes in clinical trials and on the market and the related regulatory requirements. Finally, the prospects and challenges of skin substitutes in the field of tissue engineering are discussed.

Multifunctional two-component in-situ hydrogel for esophageal submucosal dissection for mucosa uplift, postoperative wound closure and rapid healing

Endoscopic submucosal dissection (ESD) for gastrointestinal tumors and premalignant lesions needs submucosal fluid cushion (SFC) for mucosal uplift before dissection, and wound care including wound closure and rapid healing postoperatively. Current SFC materials as well as materials and/or methods for post-ESD wound care have single treatment effect and hold corresponding drawbacks, such as easy dispersion, short duration, weak hemostasis and insufficient repair function. Thus, designing materials that can serve as both SFC materials and wound care is highly desired, and remains a challenge. Herein, we report a two-component in-situ hydrogel prepared from maleimide-based oxidized sodium alginate and sulfhydryl carboxymethyl-chitosan, which gelated mainly based on "click" chemistry and Schiff base reaction. The hydrogels showed short gelation time, outstanding tissue adhesion, favorable hemostatic properties, and good biocompatibility. A rat subcutaneous ultrasound model confirmed the ability of suitable mucosal uplift height and durable maintenance time of AM solution. The in vivo/in vitro rabbit liver hemorrhage model demonstrated the effects of hydrogel in rapid hemostasis and prevention of delayed bleeding. The canine esophageal ESD model corroborated that the in-situ hydrogel provided good mucosal uplift and wound closure effects, and significantly accelerated wound healing with accelerating re-epithelization and ECM remodeling post-ESD. The two-component in-situ hydrogels exhibited great potential in gastrointestinal tract ESD.

Tea Tree Oil: Properties and the Therapeutic Approach to Acne-A Review

Acne vulgaris is an inflammatory dermatological pathology that affects mostly young people. However, it can also appear in adulthood, mainly in women. It has a high psychosocial impact, not only at the time of active lesions but also due to the consequences of lesions such as scarring and hyperpigmentation. Several factors are involved in the physiopathology of acne and the constant search for active ingredients is a reality, namely phytotherapeutic ingredients. Tea tree oil is an essential oil extracted from Melaleuca alternifolia (Maiden & Betch) Cheel with known antibacterial, anti-inflammatory, and antioxidant properties, making it a candidate for the treatment of acne. This review aims to describe the various properties of tea tree oil that make it a possible ingredient to use in the treatment of acne and to present several human studies that have evaluated the efficacy and safety of using tea tree oil in the treatment of acne. It can be concluded that tea tree oil has good antibacterial, anti-inflammatory, and antioxidant properties that result in a decrease in the number of inflammatory lesions, mainly papules, and pustules. However, given the diversity of study designs, it is not possible to draw concrete conclusions on the efficacy and safety of this oil in the treatment of acne.

Hyaluronic Acid Hydrogel Containing Resveratrol-Loaded Chitosan Nanoparticles as an Adjuvant in Atopic Dermatitis Treatment

Atopic dermatitis (AD) is a common disease-causing skin inflammation, redness, and irritation, which can eventually result in infection that drastically impacts patient quality of life. Resveratrol (Res) is a natural phytochemical famed for its excellent anti-inflammatory and antioxidant activities. However, it is poorly bioavailable. Thus, a drug delivery system is needed to enhance in vivo bioactivity. Herein, we report the preparation of hyaluronic acid (HA) hydrogels containing resveratrol-loaded chitosan (CS) nanoparticles, their physicochemical analysis, and their potential therapeutic effects in the treatment of AD. Positively charged CS nanoparticles prepared by tripolyphosphate (TPP) gelation showed sizes ranging from 120 to around 500 nm and Res encapsulation efficiency as high as 80%. Embedding the nanoparticles in HA retarded their hydrolytic degradation and also slowed resveratrol release. Resveratrol released from nanoparticle-loaded hydrogel counteracted the oxidative damage induced by ROS generation in TNF-α/INF-γ-treated human keratinocytes (HaCaT) used as an AD in vitro model. Moreover, pre-treatment with Res@gel reduced secretion and gene expression of proinflammatory cytokines in HaCaT cells. The physicochemical analysis and in vitro assay confirmed that the formulated hydrogel could be considered an efficient and sustained resveratrol delivery vector in AD treatment.

Exploiting the Physicochemical and Antimicrobial Properties of PHB/PEG and PHB/PEG/ALG-e Blends Loaded with Ag Nanoparticles

Poly(3-hydroxybutyrate) (PHB)-based films containing Poly(ethylene glycol) (PEG), esterified sodium alginate (ALG-e) and polymeric additives loaded with Ag nanoparticles (AgNPs) were obtained by a conventional casting method. AgNPs were produced in aqueous suspension and added to polymeric gels using a phase exchange technique. Composite formation was confirmed by finding the Ag peak in the XRD pattern of PHB. The morphological analysis showed that the inclusion of PEG polymer caused the occurrence of pores over the film surface, which were overshadowed by the addition of ALG-e polymer. The PHB functional groups were dominating the FTIR spectrum, whose bands associated with the crystalline and amorphous regions increased after the addition of PEG and ALG-e polymers. Thermal analysis of the films revealed a decrease in the degradation temperature of PHB containing PEG/AgNPs and PEG/ALG-e/AgNPs, suggesting a catalytic effect. The PHB/PEG/ALG-e/AgNPs film combined the best properties of water vapor permeability and hydrophilicity of the different polymers used. All samples showed good antimicrobial activity in vitro, with the greater inhibitory halo observed for the PEG/PEG/AgNPs against Gram positive S. aureus microorganisms. Thus, the PHB/PEG/ALG-e/AgNPs composite demonstrated here is a promising candidate for skin wound healing treatment.

Optimization and characterization of a novel tea tree oil-integrated poly (ε-caprolactone)/soy protein isolate electrospun mat as a wound care system

A set of poly (ε-caprolactone)/soy protein isolate (PCL/SPI) mats with different ratios of PCL to SPI was fabricated using the electrospinning method. The mat with PCL to SPI ratio of 95:5 (PS 95:5) had the narrowest nanofibers, the highest percentage of porosity, the lowest swelling ratio, the least vapor transmission, and the slowest degradation rate among the prepared mats. The hemolysis assay indicated that all mats can be considered biocompatible biomaterials. In continue, three different weight ratios of tea tree oil (TTO) were loaded into the PS 95:5 mat. The release profiles illustrated that higher amounts of TTO could be released in an acidic environment. The antioxidant activity of the mats increased by the increase in their TTO content. The cell viability test, cell adhesion images, and live/dead assay of TTO-loaded mats affirmed that all fabricated mats were biocompatible. The scratch wound assay expressed that TTO accelerates the rate of wound closure. The TTO-loaded mats illustrated antibacterial activity against both Escherichia coli and Staphylococcus aureus bacteria. The obtained outcomes revealed that TTO-loaded PCL/SPI mats can be considered promising potential wound dressings.

Polymer-Based Hydrogels Enriched with Essential Oils: A Promising Approach for the Treatment of Infected Wounds

Among the factors that delay the wound healing process in chronic wounds, bacterial infections are a common cause of acute wounds becoming chronic. Various therapeutic agents, such as antibiotics, metallic nanoparticles, and essential oils have been employed to treat infected wounds and also prevent the wounds from bacterial invasion. Essential oils are promising therapeutic agents with excellent wound healing, anti-inflammatory and antimicrobial activities, and good soothing effects. Some essential oils become chemically unstable when exposed to light, heat, oxygen, and moisture. The stability and biological activity of essential oil can be preserved via loading into hydrogels. The polymer-based hydrogels loaded with bioactive agents are regarded as ideal wound dressings with unique features, such as controlled and sustained drug release mechanisms, good antibacterial activity, non-toxicity, excellent cytocompatibility, good porosity, moderate water vapour transmission rate, etc. This review addresses the pre-clinical outcomes of hydrogels loaded with essential oils in the treatment of infected wounds.

One-Pot and Green Preparation of Phyllanthus emblica Extract/Silver Nanoparticles/Polyvinylpyrrolidone Spray-On Dressing

A spray-on wound dressing has many benefits, including easy and quick administration to broad and uneven wounds, better interface with the wound site, adhesion without additional dressing, and multiple applications in a portable package. By limiting direct contact with the wound site, such a design can prevent wound damage during treatment. This study revealed a simple, one-pot synthesis of spray-on wound dressing relying on polyvinylpyrrolidone solution incorporating silver nanoparticles as a broad-spectrum antibacterial agent and wound-healing antioxidant Phyllanthus emblica extract. Silver nanoparticles were synthesized in situ using Phyllanthus emblica extract as a biogenic reducing agent. Polyvinylpyrrolidone was employed as a film-forming agent to create an adhesive hydrogel-based dressing matrix to provide moisture and establish a shielding barrier for the wound bed as well as to regulate the release of fruit extract. In vitro tests revealed that the produced dressing film had a controlled release of the fruit extract, high antioxidant activity, and a good antibacterial action against S. aureus, P. aeruginosa, E. coli, and MRSA. Additionally, a biocompatibility study has shown that both human fibroblasts and keratinocytes are unaffected by the dressing film. Based on established findings, the current spray-on solution might be a potential option for antibacterial wound dressing.

Advances in spray products for skin regeneration

To date, skin wounds are still an issue for healthcare professionals. Although numerous approaches have been developed over the years for skin regeneration, recent advances in regenerative medicine offer very promising strategies for the fabrication of artificial skin substitutes, including 3D bioprinting, electrospinning or spraying, among others. In particular, skin sprays are an innovative technique still under clinical evaluation that show great potential for the delivery of cells and hydrogels to treat acute and chronic wounds. Skin sprays present significant advantages compared to conventional treatments for wound healing, such as the facility of application, the possibility to treat large wound areas, or the homogeneous distribution of the sprayed material. In this article, we review the latest advances in this technology, giving a detailed description of investigational and currently commercially available acellular and cellular skin spray products, used for a variety of diseases and applying different experimental materials. Moreover, as skin sprays products are subjected to different classifications, we also explain the regulatory pathways for their commercialization and include the main clinical trials for different skin diseases and their treatment conditions. Finally, we argue and suggest possible future trends for the biotechnology of skin sprays for a better use in clinical dermatology.

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Skin sprays represent a promising technique for wound healing applications.

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Skin sprays can deliver cells and hydrogels with great facility over large wounds.

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Many skin spray products have been studied, only a few have been commercialized.

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Numerous clinical trials study spray products for skin diseases like psoriasis.

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Improved spraying devices should be developed for different materials and cells.

Functionalization of mesoporous silica as an effective composite carrier for essential oils with improved sustained release behavior and long-term antibacterial performance

In this work, a novel composite carrier system for loading essential oils was developed by using tetraethyl orthosilicate (TEOS) and (3-aminopropyl) triethoxysilane (APTES) as silica precursors and cetyl trimethyl ammonium bromide (CTAB) as a template, and the resultant aminated mesoporous silica was further chemically modified by polyacrylic acid (PAA). The obtained composite carriers exhibited a high loading capability toward tea tree oil (TTO), and they also significantly improved the release behavior of TTO due to the steric hindrance of silica mesopore and the polymer restriction. Besides, it was found that the release behavior followed the First-Order kinetic model, revealing that the release of TTO was driven by the concentration gradient. In addition, these composite carriers with essential oil-loaded demonstrated remarkable antibacterial performance againstE. coliandS. aureus, and they could retain antibacterial performance even after 50 d. Moreover, the antibacterial mechanism was also elucidated with the assistance of nucleic acid and conductivity measurements. Therefore, this work provides a facile and environmentally friendly approach to preparing effective composite carriers for improving the sustained release of essential oils, and the long-term antibacterial performance of these essential oil-loaded composite carriers makes them tremendously potential for practical applications.

Current Trends in Advanced Alginate-Based Wound Dressings for Chronic Wounds

Chronic wounds represent a major public health issue, with an extremely high cost worldwide. In healthy individuals, the wound healing process takes place in different stages: inflammation, cell proliferation (fibroblasts and keratinocytes of the dermis), and finally remodeling of the extracellular matrix (equilibrium between metalloproteinases and their inhibitors). In chronic wounds, the chronic inflammation favors exudate persistence and bacterial film has a special importance in the dynamics of chronic inflammation in wounds that do not heal. Recent advances in biopolymer-based materials for wound healing highlight the performance of specific alginate forms. An ideal wound dressing should be adherent to the wound surface and not to the wound bed, it should also be non-antigenic, biocompatible, semi-permeable, biodegradable, elastic but resistant, and cost-effective. It has to give protection against bacterial, infectious, mechanical, and thermal agents, to modulate the level of wound moisture, and to entrap and deliver drugs or other molecules This paper explores the roles of alginates in advanced wound-dressing forms with a particular emphasis on hydrogels, nanofibers networks, 3D-scaffolds or sponges entrapping fibroblasts, keratinocytes, or drugs to be released on the wound-bed. The latest research reports are presented and supported with in vitro and in vivo studies from the current literature.

Rosin modified aminated mesoporous silica adsorbed tea tree oil sustained-release system for improve synergistic antibacterial and long-term antibacterial effects

Tea tree oil, a natural antibacterial compound, cannot be used effectively because of its volatile nature. In this work, a biocompatible carrier was prepared and loaded with tea tree essential oil. The carrier was prepared via the electrostatic or chemical action of aminated mesoporous silica and sodium rosin for achieving a low volatilization rate of tea tree essential oil. A synergistic antibacterial effect was observed between sodium rosin and tea tree essential oil. This method utilized the positive charge of the amino group and the condensation reaction with the carboxyl group to achieve physical and chemical interactions with sodium rosin. Fourier Transform Infrared, Brunauer-Emmet-Teller, Zeta potential, SEM, TEM, and TG were performed to characterize the structure and properties of the samples. Compared to the electrostatic effect, the chemically modified system exhibited a longer sustained release, and the sustained release curve followed the Korsmeyer-Peppas release model. Also, the antibacterial properties of the chemically modified system exhibited better minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) respectively, the MIC and MBC forE. coliwere 0.3 mg ml^-1and 0.6 mg ml^-1respectively, forS. aureuswere 0.15 mg ml^-1and 0.3 mg ml^-1respectively. More strikingly, the sample also demonstrated long-term antibacterial performance. Therefore, this work provides a new way for the delivery of volatile antibacterial drugs to achieve sustained-release and long-lasting antibacterial effects.

Injectable Self-Healing Adhesive pH-Responsive Hydrogels Accelerate Gastric Hemostasis and Wound Healing

Endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) are well-established therapeutics for gastrointestinal neoplasias, but complications after EMR/ESD, including bleeding and perforation, result in additional treatment morbidity and even threaten the lives of patients. Thus, designing biomaterials to treat gastric bleeding and wound healing after endoscopic treatment is highly desired and remains a challenge. Herein, a series of injectable pH-responsive self-healing adhesive hydrogels based on acryloyl-6-aminocaproic acid (AA) and AA-g-N-hydroxysuccinimide (AA-NHS) were developed, and their great potential as endoscopic sprayable bioadhesive materials to efficiently stop hemorrhage and promote the wound healing process was further demonstrated in a swine gastric hemorrhage/wound model. The hydrogels showed a suitable gelation time, an autonomous and efficient self-healing capacity, hemostatic properties, and good biocompatibility. With the introduction of AA-NHS as a micro-cross-linker, the hydrogels exhibited enhanced adhesive strength. A swine gastric hemorrhage in vivo model demonstrated that the hydrogels showed good hemostatic performance by stopping acute arterial bleeding and preventing delayed bleeding. A gastric wound model indicated that the hydrogels showed excellent treatment effects with significantly enhanced wound healing with type I collagen deposition, α-SMA expression, and blood vessel formation. These injectable self-healing adhesive hydrogels exhibited great potential to treat gastric wounds after endoscopic treatment.

Therapeutic Potential of Melaleuca alternifolia Essential Oil in New Drug Delivery Systems

Medicinal plants produce secondary metabolites with special biological activities, which may be used as new therapeutic alternatives. For instance, tea tree essential oil (TTO) was shown to exert antimicrobial, antifungal, anthelmintic, antiviral, anti-tumor and anti-inflammatory activities. Due to their thermal instability, active principles can be easily degraded by physicochemical processes; therefore, they must be protected to increase their time of action and improve their controlled release. The aim of this review is to discuss formulations incorporating encapsulated TTO as the active ingredient. Micro and nanoencapsulated systems proved to be more thermostable than TTO and to exert better antimicrobial, antifungal, antiparasitic and larvicidal effects. Nanoencapsulation also reduced oil toxicity. Emulsified and hybrid systems developed by various methods showed improved repellent, antibacterial, antifungal and anti-inflammatory activities, thereby proving promising for the pharmaceutical industry. Liposomal formulations produced by hydration of lipid films exhibited constant rate of terpinen-4-ol release. In addition, their incorporation into biomaterials, such as sponges, nanofibers and films, showed great potential for treating infections. Mainly due to the advantages of their incorporation into new drug delivery systems over conventional formulations, there is an interest in the development of systems containing TTO as a pharmaceutical ingredient of plant origin.

Microsponge Based Gel of Tea Tree Oil for Dermatological Microbial Infections

Objective:

Tea Tree Oil (TTO), derived from Melaleuca alternifolia possesses broad spectrum antimicrobial potential. However, its therapeutic utility is impaired due to its high volatility, poor aqueous solubility and low stability in the presence of light, oxygen and temperature. The present study was attempted to investigate Ethyl Cellulose (EC) microsponges (MSs) as topical carriers for TTO to circumvent above mentioned limitations.

Methods:

TTO MSs were prepared using quasi emulsion solvent diffusion technique. The effect of formulation variables on the production yield, entrapment efficiency, particle size and drug release of MSs was investigated. The optimized MSs were dispersed into Carbopol 934 gel and evaluated for drug release, skin irritation, antibacterial activity and photostability.

Results:

Scanning electron microscopy revealed spherical and porous nature of TTO microsponges. The optimized MSs possessed particle size of 36.98 μm, percent entrapment efficiency of 93.12% and percent cumulative drug release of 79.18%, respectively. MS-loaded gels were found nonirritant. In addition, TTO loaded MS gels exhibited good stability. Antimicrobial effect of TTO MS gel showed broader zones of inhibition in comparison to TTO gel.

Conclusion:

The findings of our study suggest that MS loaded gel could prove alternative to conventional antibacterial formulations for dermatological microbial infections.

Essential Oils-Loaded Electrospun Biopolymers: A Future Perspective for Active Food Packaging

The growth of global food demand combined with the increased appeal to access different foods from every corner of the globe is forcing the food industry to look for alternative technologies to increase the shelf life. Essential oils (EOs) as naturally occurring functional ingredients have shown great prospects in active food packaging. EOs can inhibit the growth of superficial food pathogens, modify nutritious values without affecting the sensory qualities of food, and prolong the shelf life when used in food packaging as an active ingredient. Since 2016, various reports have demonstrated that combinations of electrospun fibers and encapsulated EOs could offer promising results when used as food packaging. Such electrospun platforms have encapsulated either pure EOs or their complexation with other antibacterial agents to prolong the shelf life of food products through sustained release of active ingredients. This paper presents a comprehensive review of the essential oil-loaded electrospun fibers that have been applied as active food packaging material.

Development of galangal essential oil-based microemulsion gel for transdermal delivery of flurbiprofen: simultaneous permeability evaluation of flurbiprofen and 1,8-cineole

Flurbiprofen (FP) is one of the most potent nonsteroidal anti-inflammatory drugs with very low bioavailability of approximately 12% following transdermal administration, compared to that after oral administration. This study aimed to deliver FP as a microemulsion (ME) gel by transdermal administration. Galangal essential oil (GEO) was extracted from Rhizoma Alpiniae Officinarum and identified by GC-MS. The most abundant constituent was determined to be 1,8-cineole (52.06%). Compared to azone, GEO was proved to exert significantly higher (p < .01) penetration enhancement effect and significantly (p < .001) lower skin cell toxicity. The formulation (FP-GEO-ME gel) was prepared using GEO as an oil phase and a penetration enhancer. Compared to that of FP solution, the enhancement ratio (ER) of FP-GEO-ME gel was 4.06. In addition, more than 25% 1,8-cineole permeated through the rat skin. In vivo pharmacokinetic studies revealed that the AUC_0-t of FP after transdermal administration of FP-GEO-ME gel was higher by approximately 4.56-fold than that of marketed FP cataplasms. The relative bioavailability of FP and 1,8-cineole after transdermal administration compared to oral administration of FP-GEO-ME were determined to be 96.58% and 85.49%, respectively. FP-GEO-ME gel significantly inhibited carrageenan-induced hind-paw edema and decreased PGE2 levels in rat serum. GEO-ME gel also exhibited significant anti-inflammatory effects at 2 h after the therapy (p < .05). The synergistic effects of FP and GEO were expected for the application of FP-GEO-ME gel. In conclusion, GEO-ME gel may be a promising formulation for transdermal administration of anti-inflammatory hydrophobic drugs, such as FP.

Quality by Design Approach Using Multiple Linear and Logistic Regression Modeling Enables Microemulsion Scale Up

The development of pharmaceutical nanoformulations has accelerated over the past decade. However, the nano-sized drug carriers continue to meet substantial regulatory and clinical translation challenges. In order to address some of these key challenges in early development, we adopted a quality by design approach to develop robust predictive mathematical models for microemulsion formulation, manufacturing, and scale-up. The presented approach combined risk management, design of experiments, multiple linear regression (MLR), and logistic regression to identify a design space in which microemulsion colloidal properties were dependent solely upon microemulsion composition, thus facilitating scale-up operations. Developed MLR models predicted microemulsion diameter, polydispersity index (PDI), and diameter change over 30 days storage, while logistic regression models predicted the probability of a microemulsion passing quality control testing. A stable microemulsion formulation was identified and successfully scaled up tenfold to 1L without impacting droplet diameter, PDI, or stability.

Antibacterial properties of nanofibers containing chrysanthemum essential oil and their application as beef packaging

This study was aimed to develop novel antibacterial packaging materials in order to reduce the microbial contamination of food surface. Chrysanthemum essential oil (CHEO) was successfully incorporated into chitosan nanofibers (CS/NF) through electrospinning which was demonstrated by SEM and AFM analysis. The antibacterial mechanism of CHEO against Listeria monocytogenes (L. monocytogenes) was explored as well. The cell membrane permeability of L. monocytogenes appeared to be increased by CHEO. In addition, respiratory metabolism of L. monocytogenes was inhibited by CHEO through the inhibition of the Embden-Meyerhof-Parnas (EMP) pathway. The presence of CHEO had a negative effect on the activity of hexokinase, phosphofructokinase and pyruvate kinase in L. monocytogenes cells. Release efficiency study indicated that the CHEO could be released slowly from CHEO/CS/NF to achieve long-lasting antibacterial effect. The antibacterial application of the CHEO nanofibers against L. monocytogenes was tested on beef, with an inhibition rate of 99.91%, 99.97%, and 99.95% at the temperature of 4 °C, 12 °C and 25 °C, respectively, after 7 days of storage. Beef parameters like thiobarbituric acid reactive substances (TBARS), pH values, and texture at different storage temperatures (4 °C, 12 °C and 25 °C) were evaluated as well. Due to the presence of antioxidant components in CHEO released from CHEO/CS/NF, the TBARS value in treated beef was 0.135 MDA/kg lower (P < 0.05) than the untreated sample at 4 °C after 12 days. PH value assay indicated that PH value of beef sample packed with CHEO/CS/NF (6.43) was lower than unpacked sample (7.05) at 4 °C after 10 days of storage. These obtained results all illustrated the fact that CHEO/CS/NF could prolong the shelf-life of beef, suggesting a potential application in food packaging.

Plasma-treated poly(ethylene oxide) nanofibers containing tea tree oil/beta-cyclodextrin inclusion complex for antibacterial packaging

This work describes the effect of cold nitrogen plasma to enhance the antibacterial activity of poly(ethylene oxide) (PEO) nanofibers containing antibacterial agent. Beta-cyclodextrin (β-CD) and tea tree oil (TTO) were used as a host-guest to form water-soluble inclusion complex. The encapsulation efficiency of TTO in inclusion complex could reach 73.23% at 60°C. As antibacterial agent, the inclusion complex was encapsulated into PEO matrix by electrospun. After plasma treatment, the release efficiency of antibacterial agent from PEO nanofibers was improved. As a result, the antibacterial activity of PEO nanofibers was enhanced accordingly. The plasma-treated nanofiber membranes achieved the highest antibacterial activity against Escherichia coli O157:H7, which was tested on the beef for 7d, with inhibition efficiently of 99.99% whether at 4°C or 12°C. The plasma-treated PEO nanofiber membranes containing TTO/β-CD inclusion complex (TTO/β-CD-IC) can prolong the shelf-life of beef, suggesting it has potential application in active food packaging.

Encapsulation of tea tree oil by amorphous beta-cyclodextrin powder

An innovative method to encapsulate tea tree oil (TTO) by direct complexation with solid amorphous beta-cyclodextrin (β-CD) was investigated. A β-CD to TTO ratio of 90.5:9.5 (104.9mg TTO/g β-CD) was used in all complexation methods. The encapsulation was performed by direct mixing, and direct mixing was followed by the addition of water (13-17% moisture content, MC) or absolute ethanol (1:1, 1:2, 1:3 and 1:4 TTO:ethanol). The direct mixing method complexed the lowest amount of TTO (60.77mg TTO/g β-CD). Powder recrystallized using 17% MC included 99.63mg of TTO/g β-CD. The addition of ethanol at 1:2 and 1:3 TTO:ethanol ratios resulted in the inclusion of 94.3 and 98.45mg of TTO/g β-CD respectively, which was similar to that of TTO encapsulated in the conventional paste method (95.56mg TTO/g β-CD), suggesting an effective solid encapsulation method. The XRD and DSC results indicated that the amorphous TTO-β-CD complex was crystallized by the addition of water and ethanol.

Alginate hydrogels coated with chitosan for wound dressing

In this work, a coating of chitosan onto alginate hydrogels was realized using the water-soluble hydrochloride form of chitosan (CH-Cl), with the dual purpose of imparting antibacterial activity and delaying the release of hydrophilic molecules from the alginate matrix. Alginate hydrogels with different calcium contents were prepared by the internal setting method and coated by immersion in a CH-Cl solution. Structural analysis by cryo-scanning electron microscopy was carried out to highlight morphological alterations due to the coating layer. Tests in vitro with human mesenchymal stromal cells (MSC) were assessed to check the absence of toxicity of CH-Cl. Swelling, stability in physiological solution and release characteristics using rhodamine B as the hydrophilic model drug were compared to those of relative uncoated hydrogels. Finally, antibacterial activity against Escherichia coli was tested. Results show that alginate hydrogels coated with chitosan hydrochloride described here can be proposed as a novel medicated dressing by associating intrinsic antimicrobial activity with improved sustained release characteristics.