Physical properties and antibacterial activity of chitosan/acemannan mixed systems

Application of biomimetically synthesized silver nanoparticles as cathode catalyst, quorum-quencher, and anti-biofouling agent for the performance boosting of microbial fuel cell

A microbial fuel cell (MFC) is a cutting-edge bioelectrochemical technology, which demonstrates power and other valuables recovery while treating wastewater by cultivating electroactive microbes. However, rampant biofilm growth over the cathode surface of air cathode MFC exacerbates the oxidation-reduction reaction rate, triggering a dip in the overall performance of MFC. In this sense, biosynthesized silver nanoparticles (AgNPs) have garnered a plethora of potential applications as cathode catalysts as well as anti-biofouling agent for MFCs without harming nature. The MFC equipped with the mixture of aloe vera and algae (@5 mg/cm2) synthesized AgNPs on cathode generated a maximum power density of 66.5 mW/m2 and chemical oxygen demand removal efficiency of 85.2%, which was ca. 5.6 times and 1.2 times higher compared to control MFC operated without any catalyst on cathode. Thus, this investigation paves the way for using eco-amiable, low-cost bioderived organic compounds to assist MFC in achieving high power output and other valuables with minimal reliance on chemicals.

A New Biomaterial Derived from Aloe vera-Acemannan from Basic Studies to Clinical Application

Aloe vera is a kind of herb rich in polysaccharides. Acemannan (AC) is considered to be a natural polysaccharide with good biodegradability and biocompatibility extracted from Aloe vera and has a wide range of applications in the biomedical field due to excellent immunomodulatory, antiviral, antitumor, and tissue regeneration effects. In recent years, clinical case reports on the application of AC as a novel biomedical material in tissue regenerative medicine have emerged; it is mainly used in bone tissue engineering, pulp-dentin complex regeneration engineering, and soft tissue repair, among other operations. In addition, multiple studies have proved that the new composite products formed by the combination of AC and other compounds have excellent biological and physical properties and have broader research prospects. This paper introduces the preparation process, surface structure, and application forms of AC; summarizes the influence of acetyl functional group content in AC on its functions; and provides a detailed review of the functional properties, laboratory studies, clinical cutting-edge applications, and combined applications of AC. Finally, the current application status of AC from basic research to clinical treatment is analyzed and its prospects are discussed.

Recent advances in polysaccharide-based edible coatings for preservation of fruits and vegetables: A review

Harvested fruits and vegetables are prone to decay and quality deterioration during storage. Although traditional packaging and chemical treatments are effective, they are harmful to the environment and human health. Hence, higher requirements for food preservation technology are increasingly proposed. Nontoxic, renewable, degradable, and edible packaging for fruits and vegetables has become a research hotspot in recent years. Chitosan, alginate, cellulose, pectin, starch, and other polysaccharides as coating materials have been widely used. Compared with traditional plastic packaging and chemical treatment, these coatings exhibited a better preservation effect and higher safety. In this paper, the preservation mechanism of fruits and vegetables by edible coatings treatment was described, and the research on edible coatings used in fruits and vegetables was summarized. The effects polysaccharide-based edible coatings on physicochemical quality and antimicrobial effect of fruits and vegetables were reviewed.

Physicochemical features assessment of acemannan-based ternary blended films for biomedical purposes

The exploitation of natural origin macromolecules, as complex physical mixtures or drugs, increases in biomedical or tissue engineering (TE) solutions. Aloe Vera is a highly explored medicinal plant, from which the main polysaccharide is acemannan (ACE). The ACE combination with chitosan and alginate results in interactions that lead to mixed junction zones formation, predicting membrane functionality improvement. This work proposes the development and characterization of ACE-based blended films as a promising strategy to design a nature-derived bioactive platform. The results confirmed that stable complex polyelectrolyte structures were formed through different intermolecular interactions. The films present good dimensional stability, flexibility, an adequate swelling ability with mostly radial water uptake, and a sustainable ACE release to the medium. Positive biological performance of the ACE-based blended films with L929 cells also suggested that they can be applied in TE solutions, with the potential to act as bioactive topical platforms.

Antibacterial polysaccharide-based hydrogel dressing containing plant essential oil for burn wound healing

BACKGROUND

Polysaccharide-based hydrogels have been developed for many years to treat burn wounds. Essential oils extracted from aromatic plants generally exhibit superior biological activity, especially antibacterial properties. Studies have shown that antibacterial hydrogels mixed with essential oils have great potential for burn wound healing. This study aimed to develop an antibacterial polysaccharide-based hydrogel with essential oil for burn skin repair.

METHODS

Eucalyptus essential oil (EEO), ginger essential oil (GEO) and cumin essential oil (CEO) were employed for the preparation of effective antibacterial hydrogels physically crosslinked by carboxymethyl chitosan (CMC) and carbomer 940 (CBM). Composite hydrogels were prepared and characterized using antimicrobial activity studies, Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, gas chromatography-mass spectrometery, rheological analysis, viscosity, swelling, water loss rate and water vapor transmission rate studies. In addition, the biocompatibility of hydrogels was evaluated in vivo by cytotoxicity and cell migration assays and the burn healing ability of hydrogels was tested in vivo using burn-induced wounds in mice.

RESULTS

The different essential oils exhibited different mixing abilities with the hydrogel matrix (CMC and CBM), which caused varying levels of reduction in essential oil hydrogel viscosity, swelling and water vapor transmission. Among the developed hydrogels, the CBM/CMC/EEO hydrogel exhibited optimal antibacterial activities of 46.26 ± 2.22% and 63.05 ± 0.99% against Staphylococcus aureus and Escherichia coli, respectively, along with cell viability (>92.37%) and migration activity. Furthermore, the CBM/CMC/EEO hydrogel accelerated wound healing in mouse burn models by promoting the recovery of dermis and epidermis as observed using a hematoxylin-eosin and Masson's trichrome staining assay. The findings from an enzyme-linked immunosorbent assay demonstrated that the CBM/CMC/EEO hydrogel could repair wounds through interleukin-6 and tumor necrosis factor-α downregulation and transforming growth factor-β, vascular endothelial growth factor (VEGF) and epidermal growth factor upregulation.

CONCLUSIONS

This study successfully prepared a porous CBM/CMC/EEO hydrogel with high antibacterial activity, favorable swelling, optimal rheological properties, superior water retention and water vapor transmission performance and a significant effect on skin repair in vitro and in vivo. The results indicate that the CBM/CMC/EEO hydrogel has the potential for use as a promising burn dressing material for skin burn repair.

Extraction, Purification, Structural Characteristics, Biological Activities and Pharmacological Applications of Acemannan, a Polysaccharide from Aloe vera: A Review

Aloe vera is a medicinal plant species of the genus Aloe with a long history of usage around the world. Acemannan, considered one of the main bioactive polysaccharides of Aloe vera, possesses immunoregulation, anti-cancer, anti-oxidation, wound healing and bone proliferation promotion, neuroprotection, and intestinal health promotion activities, among others. In this review, recent advancements in the extraction, purification, structural characteristics and biological activities of acemannan from Aloe vera were summarized. Among these advancements, the structural characteristics of purified polysaccharides were reviewed in detail. Meanwhile, the biological activities of acemannan from Aloe vera determined by in vivo, in vitro and clinical experiments are summarized, and possible mechanisms of these bioactivities were discussed. Moreover, the latest research progress on the use of acemannan in dentistry and wound healing was also summarized in details. The structure-activity relationships of acemannan and its medical applications were discussed. Finally, new perspectives for future research work on acemannan were proposed. In conclusion, this review summarizes the extraction, purification, structural characteristics, biological activities and pharmacological applications of acemannan, and provides information for the industrial production and possible applications in dentistry and wound healing in the future.

Acemannan Gels and Aerogels

The procedures to obtain two types of acemannan (AC) physical gels and their respective aerogels are reported. The gelation was induced by the diffusion of an alkali or a non-solvent, then supercritical CO₂ drying technology was used to remove the solvent out and generate the AC aerogels. Fourier-transform infrared spectroscopic analysis indicated that alkali diffusion produced extensive AC deacetylation. Conversely, the non-solvent treatment did not affect the chemical structure of AC. Both types of gels showed syneresis and the drying process induced further volume reduction. Both aerogels were mesoporous nanostructured materials with pore sizes up to 6.4 nm and specific surface areas over 370 m²/g. The AC physical gels and aerogels enable numerous possibilities of applications, joining the unique features of these materials with the functional and bioactive properties of the AC.

Preparation and characterization of N-chitosan as a wound healing accelerator

Chitosan is insoluble in water due to its rigid crystalline structure, which has significantly restricted its application in wound healing. The objective of this study was to synthesize a water-soluble chitosan derivative, N-succinyl-chitosan (NSC), and evaluate its ability to accelerate the wound healing process. NSC was synthesized with succinic anhydride, hydrochloric acid, and alkaline chitosan under optimized conditions, and characterized using Fourier transform infrared, proton nuclear magnetic resonance, and X-ray diffraction spectroscopy; thermal gravimetric analysis; and a solubility test. The cytotoxicity of NSC was investigated in L929 cells, and its antibacterial activity was evaluated by the inhibition zone method and bacterial growth curves analysis. The results showed that the solubility of NSC was substantially improved compared to chitosan, and NSC was non-toxic with good antibacterial properties. An animal wound healing test indicated that NSC could significantly reduce the healing time compared to chitosan. Histopathological examination suggested that the underlying mechanisms of these effects were related to NSC's ability to promote the formation of granulation tissue and enhance epithelialization. Collectively, these results demonstrate the good potential for NSC to be applied as a wound dressing material.

Novel chitosan/diclofenac coatings on medical grade stainless steel for hip replacement applications

Corrosion resistance, biocompatibility, improved osteointegration, as well the prevention of inflammation and pain are the most desired characteristics of hip replacement implants. In this study we introduce a novel multi-layered coating on AISI 316LVM stainless steel that shows promise with regard to all mentioned characteristics. The coating is prepared from alternating layers of the biocompatible polysaccharide chitosan and the non-steroid anti-inflammatory drug (NSAID), diclofenac. Electrochemical methods were employed to characterize the corrosion behavior of coated and uncoated samples in physiological solution. It is shown that these coatings improve corrosion resistance. It was also found that these coatings release the incorporated drug in controlled, multi-mechanism manner. Adding additional layers on top of the as-prepared samples, has potential for further tailoring of the release profile and increasing the drug dose. Biocompatibility was proven on human-derived osteoblasts in several experiments. Only viable cells were found on the sample surface after incubation of the samples with the same cell line. This novel coating could prove important for prolongation of the application potential of steel-based hip replacements, which are these days often replaced by more expensive ceramic or other metal alloys.

Development of chitosan/β-glycerophosphate/glycerol hydrogel as a thermosensitive coupling agent

This work develops a dual-function thermosensitive hydrogel to prevent overheating, a side effect of focused ultrasound therapy. The proposed hydrogel has the components of chitosan, β-glycerophosphate, and glycerol. Its thermosensitive sol-to-gel transition gives an instant signal of overheating without the need of any awkward sensing device. Impacts of varying component concentrations on the sol-to-gel temperature, rate, and degree of transparency are also investigated. Chemical structures and ultrasonic coefficients after heating are obtained with a Fourier transform infrared spectroscopy and ultrasonic measurement, respectively. Optimized formula of the proposed hydrogel is 0.5% chitosan, 5% β-glycerophosphate, and 25% glycerol. This hydrogel has a high acoustic impedance (Z=1.8 Mrayl) close to that of human skin, high ultrasonic transmission (T=99%, which is normalized to water) from 25 to 55°C, and low attenuation coefficient (α=4.0Np/m). These properties assure the success of dual functions of the hydrogel developed in this work.

Comparison the efficacy of herbal mouthwash with chlorhexidine on gingival index of intubated patients in Intensive Care Unit

Background:

Intubated patients in Intensive Care Unit (ICU) are not able to take care of their mouth health, so they are at risk of bacterial colonization and dental plaques formation that can lead to systemic diseases such as pneumonia and gingivitis.

Aims:

In randomized, double-blind clinical study, the efficacy of natural herbal mouthwash containing Salvadora persica ethanol extract and Aloe vera gel was compared with chlorhexidine on gingival index (GI) of intubated patients in ICU.

Materials and Methods:

Seventy-six intubated patients (18–64 years old with mean age 40.35 ± 13.2) in ICU were admitted to this study. The patients were randomly divided into two groups: (1) Herbal mouthwash and (2) chlorhexidine solution. Before the intervention, the GIs was measured by modified GI device into two groups. The mouth was rinsed by mouthwashes every 2–3 h for 4 days. 2 h after the last intervention, GIs were determined.

Results:

Along with mechanical methods, herbal mouthwash in reducing GI was statistically significant than that of chlorhexidine (P < 0.05).

Conclusion:

The results of this study introduce a new botanical extract mouthwash with dominant healing effects on GI (1.5 ± 0.6) higher than that of synthetic mouthwash, chlorhexidine (2.31 ± 0.73).

Organic-inorganic hybrid nanoparticles for bacterial inhibition: synthesis and characterization of doped and undoped ONPs with Ag/Au NPs

Organic nanoparticles (ONPs) of lipoic acid and its doped derivatives ONPs/Ag and ONPs/Au were prepared and characterized by UV-Visible, EDS, and TEM analysis. The antibacterial properties of the ONPs ONPs/Ag and ONPs/Au were tested against bacterial strains (Staphylococcus aureus, Bacillus cereus, Escherichia coli and Salmonella typhi). Minimal Inhibitory Concentration (MIC) and bacterial growth inhibition tests show that ONPs/Ag are more effective in limiting bacterial growth than other NPs, particularly, for Gram positive than for Gram-negative ones. The order of bacterial cell growth inhibition was ONPs/Ag > ONPs > ONPs/Au. The morphology of the cell membrane for the treated bacteria was analyzed by SEM. The nature of bond formation of LA with Ag or Au was analyzed by molecular orbital and density of state (DOS) using DFT.