Chemical composition, antimicrobial activities and microencapsulation by complex coacervation of tea tree essential oils

A review of advancements in chitosan-essential oil composite films: Better and sustainable food preservation with biodegradable packaging

In response to the environmental pollution caused by non-degradable and non-recyclable plastic packaging films (PPFs) and the resulting health concerns due to the migration of microplastics into food, the development of biodegradable food packaging films has gained great attention. Chitosan has been extensively utilized in the food industry owing to its abundant availability, exceptional biocompatibility, degradability, and antimicrobial properties. Chitosan-essential oil composite films (CEOs) represent a promising avenue to replace conventional PPFs. This review provides an overview of the advancements in CEOs over the past decade, focusing on the effects of essential oils (EOs) on CEOs in terms of antimicrobial activity, antioxidant effect, gas barrier, light barrier, and mechanical properties. It also offers insights into the controlled release of EOs in CEOs and summarizes the application of CEOs in fresh food preservation.

Understanding the Impacts of Molecular and Macromolecular Crowding Agents on Protein-Polymer Complex Coacervates

Complex coacervation refers to the liquid-liquid phase separation (LLPS) process occurring between charged macromolecules. The study of complex coacervation is of great interest due to its implications in the formation of membraneless organelles (MLOs) in living cells. However, the impacts of the crowded intracellular environment on the behavior and interactions of biomolecules involved in MLO formation are not fully understood. To address this knowledge gap, we investigated the effects of crowding on a model protein-polymer complex coacervate system. Specifically, we examined the influence of sucrose as a molecular crowder and polyethylene glycol (PEG) as a macromolecular crowder. Our results reveal that the presence of crowders led to the formation of larger coacervate droplets that remained stable over a 25-day period. While sucrose had a minimal effect on the physical properties of the coacervates, PEG led to the formation of coacervates with distinct characteristics, including higher density, increased protein and polymer content, and a more compact internal structure. These differences in coacervate properties can be attributed to the effects of crowders on individual macromolecules, such as the conformation of model polymers, and nonspecific interactions among model protein molecules. Moreover, our results show that sucrose and PEG have different partition behaviors: sucrose was present in both the coacervate and dilute phases, while PEG was observed to be excluded from the coacervate phase. Collectively, our findings provide insights into the understanding of crowding effects on complex coacervation, shedding light on the formation and properties of coacervates in the context of MLOs.

Preparation of β-ionone microcapsules by gelatin/pectin complex coacervation

β-ionone has a unique violet odor and good biological activity, which is an essential fragrance component and potential anticancer drug. In this paper, β-ionone was encapsulated using complex coacervation of gelatin and pectin, followed by cross-linking with glutaraldehyde. The pH value, wall material concentration, core-wall ratio, homogenization conditions, and curing agent content were investigated in the single-factor experiments. For example, the encapsulation efficiency increased with the homogenization speed, which reached a relatively high value at 13000 r/min for 5 min. The gelatin/pectin ratio (3:1, w/w) and pH value (4.23) significantly affected the size, shape, and encapsulation efficiency of the microcapsule. The fluorescence microscope and SEM were used to characterize the morphology of the microcapsules, in which the microcapsule has a stable morphology, uniform size, and spherical multinuclear structure. FTIR measurements confirmed the electrostatic interactions between gelatin and pectin during complex coacervation. Thermogravimetric analysis (TGA) revealed that the microcapsules could maintain good thermal stability over 260 °C. The release rate of β-ionone microcapsule was only 20.6 % after 30 days at the low temperature of 4 °C. These findings provide an effective carrier to deliver flavors like β-ionone and could be useful in the fields of daily chemicals and textiles.

Fabrication and characterization of natural polyphenol and ZnO nanoparticles loaded protein-based biopolymer multifunction electrospun nanofiber films, and application in fruit preservation

To extend the shelf life of sweet cherries (Prunus avium L.) and considering the environmental problems caused by traditional packaging materials, novel Zein/Gelatin-proanthocyanidins-zinc oxide nanoparticles (ZE/GE-PC-ZnO) and Zein/Gelatin-gallic acid-zinc oxide nanoparticles (ZE/GE-GA-ZnO) protein-based composite nanofiber films were prepared by electrospinning. According to the results, ZE/GE-PC-ZnO and ZE/GE-GA-ZnO films' contact angles were higher than those of Zein/Gelatin film by 28.91% and 21.27%, and their antioxidant activities were 5 and 9 times higher, respectively. Moreover, ZE/GE-PC-ZnO film showed good inhibitory activity against B. cinerea. On the eleventh day of the cherry packaging test, compared to unwrapped cherries, the losses of weight and firmness of wrapped fruit were reduced by more than 20% and 60%, respectively. Respiration time was delayed by 5 days, and the peak of ethylene release was decreased by nearly half. In conclusion, these two nanofiber films were viable packaging materials that fulfilled global strategies for green development.

Antibacterial activity of oregano essential oils against Streptococcus mutans in vitro and analysis of active components

BACKGROUND

Streptococcus mutans (S. mutans) is considered the most relevant bacteria during the transition of the non-pathogenic commensal oral microbial community to plaque biofilms that promote the development of dental caries. Oregano (Origanum vulgare L.), is a universally natural flavoring and its essential oil has been demonstrated to have good antibacterial effects. However, the specific antibacterial mechanism of oregano essential oil (OEO) against S. mutans is still not completely understood.

METHODS

In this work, the composition of two different OEOs was determined by GC‒MS. Disk-diffusion method, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined to assess their antimicrobial effect on S. mutans. The inhibition of acid production, hydrophobicity, biofilm formation and real-time PCR for gtfB/C/D, spaP, gbpB, vicR, relA and brpA mRNA expression by S. mutans were assessed to preliminarily investigate the mechanisms of action. Molecular docking was performed to simulate the interactions with the virulence proteins and active constituents. MTT test using immortalized human keratinocytes cells was also performed to investigate cytotoxicity.

RESULTS

Compared with the positive drug Penicillin /streptomycin 100X (DIZ: 34.13 ± 0.85 mm, MIC: 0.78125 μL/mL, MBC: 6.25 μL/mL), the essential oils of Origanum vulgare L. (DIZ: 80 mm, MIC: 0.625μL/mL, MBC:2.5μL/mL) and Origanum heracleoticum L. (DIZ: 39.67 ± 0.81 mm, MIC: 0.625μL/mL, MBC: 1.25μL/mL) could also exhibit similar effects to inhibit the acid production and reduce the hydrophobicity and biofilm formation of S. mutans at 1/2-1MIC concentration. And gene expression of gtfB/C/D, spaP, gbpB, vicR and relA were found to be downregulated. Due to the composition of essential oils from different sources being highly variable, through effective network pharmacology analysis, we found that OEOs contained many effective compounds, like carvacrol and its biosynthetic precursors γ-terpinene and p-cymene, which may directly target several virulence proteins of S. mutans. Besides, no toxic effect was instigated by OEOs at 0.1 μL/mL in the immortalized human keratinocytes cells.

CONCLUSION

The integrated analysis in the present study suggested that OEO might be a potential antibacterial agent for the prevention of dental caries.

Controlled Release of Tea Tree Oil from a Chitosan Matrix Containing Gold Nanoparticles

Chitosan is a biopolymer that, due to its versatile bioactive properties, has applications in several areas, including food, medicine and pharmaceuticals. In the field of tissue engineering, chitosan can be used, for example, as a dressing to treat wounds or dermal damage, such as burns or abrasions. This work deals with the controlled release of tea tree oil from chitosan-based polymeric films and droplets containing gold nanoparticles (AuNP). AuNPs were successfully incorporated into the chitosan matrix using two different approaches. Both solutions were loaded with tea tree oil, and from these solutions, it was possible to obtain drop-cast films and droplets. The controlled release of oil in water was performed both in the films and in the droplets. The addition of AuNP in the controlled release system of melaleuca oil favored a release time of around 25 h. A series of experiments was carried out to investigate the effects of different reaction temperatures and acetic acid concentrations on the formation of AuNPs in the presence of chitosan. For this purpose, images of the AuNP films and droplets were obtained using transmission electron microscopy. In addition, UV-vis spectra were recorded to investigate the release of tea tree oil from the different samples.