Preparation and antibacterial mechanism of cinnamaldehyde/tea polyphenol/polylactic acid coaxial nanofiber films with zinc oxide sol to Shewanella putrefaciens

Impaired cellular barriers and blocked metabolic pathways contribute to inhibition of carvacrol-loaded nanoemulsions stabilized by soy protein isolate / chitooligosaccharide conjugate on S. putrefaciens

In this study, soy isolate protein / chitooligosaccharide (SPI/COS) glycosylated conjugates was prepared and employed as an emulsifier to stabilize carvacrol-loaded nanoemulsions (CNE-SPI/COS). The antibacterial properties and mechanism of CNE-SPI/COS against S. putrefaciens was investigated. The results of microbial growth curves and confocal laser scanning microscopy (CLSM) results showed that CNE-SPI/COS effectively inhibited the growth of S. putrefaciens and the killing effect of CNE-SPI/COS on S. putrefaciens was concentration-dependent. Field emission scanning electron microscopy (FESEM) images showed that CNE-SPI/COS caused folds, shrinkage, rupture and even lysis of S. putrefaciens. The results showed that CNE-SPI/COS inhibited the growth and reproduction of S. putrefaciens mainly through three targets: (i) the reduction of alkaline phosphatase (AKP) activity and protein leakage indicated that CNE-SPI/COS disrupted the integrity of cell wall and cell membrane; (ii) the reduction of intracellular protein and ATP content indicated that CNE-SPI/COS interfered the synthesis of intracellular nutrient and synthesis of energy-supplying substances; (iii) changes in the activities of succinate dehydrogenase, pyruvate kinase, and glucose 6-phosphate dehydrogenase indicated that CNE-SPI/COS impeded the normal cellular metabolic pathways such as the tricarboxylic acid cycle, the glycolytic pathway, and the pentose phosphate pathway, and the decrease in superoxide dismutase activity indicated that CNE-SPI/COS disrupted the defense system against oxidative stress. In conclusion, the encapsulation of carvacrol into the nanoemulsion system can provide theoretical support and methodological guidance for the application of nanoemulsions in microbial decontamination of aquatic products.

Polylactic acid amine-sensitive colorimetric indicator film loaded with eugenol/coumarin derivatives: Towards freshness indication and shelf-life extension of chilled pork

The action of microorganisms can lead to a decrease in food freshness and cause food safety issues. Traditional packaging can only provide a certain antimicrobial effect and cannot indicate the freshness of food, which can no longer meet the needs of consumers. The preparation of intelligent packaging films with antimicrobial effects and freshness indication is an effective solution. In this study, A novel electrospun intelligent food packaging film based on polylactic acid/eugenol/coumarin derivatives (7-(diethylaMino)-2-oxo-2H-chroMene-3-carbaldehyde) has been constructed to achieve the dual functions of antimicrobial and freshness indication for chilled pork. The antimicrobial layer loads eugenol coaxially into the fiber, which could scavenge 82.92 % of DPPH free radicals and effectively inhibit the growth of Escherichia coli and Staphylococcus aureus. The freshness-indicating layer showed fluorescence responsiveness to biogenic amines. The freshness-indicating and antimicrobial fibrous bilayer film turned green in practical application to indicate that the refrigerated pork had spoiled and was effective in extending the shelf life by 4-6 days. This study demonstrated the effectiveness of the bilayer film for preservation and freshness non-destructive testing of chilled pork. It provided a theoretical basis for the general application of film.

Development of poly(lactic acid)/polyvinyl alcohol-based temperature-responsive shell-core nanofibers: Controlled release, biosafety evaluation, and application in raspberry preservation

With the increasing demand for sustainable and effective food preservation methods, the development of novel smart preservation materials has become a pressing need. A temperature-responsive smart nanofiber material with a shell-core structure, polyvinyl alcohol/poly(N-isopropylacrylamide)/polylactic acid/lemon essential oil (PPPL), was developed by incorporating lemon essential oil as a core-layer preservative and poly(N-isopropylacrylamide) as a temperature-responsive shell layer. Transmission electron microscopy confirmed the shell-core structure of the fibers. When the temperature exceeded the lower critical solution temperature, the water contact angle increased from 56° to 91°, confirming that PPPL was temperature-responsive. Infrared spectroscopy revealed interactions between the core and shell layers, which contributed to the tensile strength of 4.31 MPa and enhanced the material's water vapor barrier properties. Release studies indicated that the fibers effectively regulated lemon essential oil release, achieving a radical scavenging rate of 42 % within 24 h. Analysis of the release kinetics revealed temperature-dependent control and effective inhibition of Staphylococcus aureus and Escherichia coli growth. Additionally, the PPPL fibers exhibited significant natural degradation after three months of incubation and showed no toxicity to zebrafish or BV2 mouse glial cells, confirming their environmental and biological safety. A raspberry preservation experiment further demonstrated that under fluctuating temperature conditions, the nanofiber membrane slowed postharvest deterioration in fruit quality. This coaxial nanofiber material enables the sustained release of antibacterial agents triggered by temperature variations, offers long-term preservation for food storage, and supports the use of electrospinning technology in smart food packaging.

A Tea Polyphenol-Infused Sprayable Thermosensitive Liposomal Hydrogel for Enhanced Anti-Inflammatory and Antibacterial Psoriasis Treatment

Psoriasis is a chronic and recurrent inflammatory disease driven not only by intrinsic factors such as immune system dysregulation but also by external factors, including bacterial infections. In contrast to the control of a single pathogenic pathway, combination therapies addressing both the immune and infectious components of psoriasis pathogenesis may offer a more effective strategy for controlling its progression. In this study, we developed a sprayable hydrogel incorporating tea polyphenol-loaded lauric acid liposomes (TP@LA-Lipo gel) to investigate its anti-inflammatory and antibacterial role in psoriasis. Our results demonstrated that TP@LA-Lipo modulated macrophage activity, reduced the expression of iNOS and TNF-α, and remodeled the immune microenvironment. Meanwhile, TP@LA-Lipo effectively eliminated Staphylococcus aureus and Escherichia coli through membrane disruption, mitigating the provoked inflammatory response. More importantly, TP@LA-Lipo gel, when sprayed onto the psoriasis lesions, provided sustained drug release over three days, enabling deeper penetration through the thickened stratum corneum to reach the inflamed layers beneath. Furthermore, in an imiquimod-induced psoriasis mouse model, TP@LA-Lipo gel effectively restored the damaged skin, alleviated histopathological changes, and reduced the systemic immune response. In summary, these findings indicate that TP@LA-Lipo gel offers a comprehensive strategy for effective disease management and improving the quality of life for psoriasis patients.

Fe3O4-Based Nanospheres with High Photothermal Conversion Efficiency for Dual-Effect and Mild Biofilm Eradication against Periodontitis

Periodontitis, a chronic inflammatory oral disease resulting from plaque biofilms, affects about 743 million individuals worldwide. However, the efficacy of current treatments is hampered by challenges in delivering antibiotics to recalcitrant oral biofilms and bacterial resistance, thereby impeding successful treatment of infectious diseases. To address the issues, an antibacterial photothermal material was designed, comprising a spherical structure of zinc oxide (ZnO) wrapped with triiron tetraoxide (Fe3O4). The outer layer of the material adsorbed epsilon-polylysine (EPL) by electrostatic action, ultimately leading to the fabrication of Fe3O4/ZnO/EPL nanoparticles (FZE NPs). The Fe3O4 core endowed the nanoparticles with efficient photothermal properties, facilitating the dispersion of dense biofilms, which dramatically promoted the adsorption and penetration of ZnO and EPL into the biofilms to effectively kill bacteria in biofilms in vitro with enhanced sterilization ability. Additionally, upon dissolution in aqueous media, EPL acts as a positively charged antimicrobial peptide that adsorbs onto the surface of negatively charged bacterial membranes, thereby effectively modulating inflammatory responses. In order to ascertain the efficacy of FZE NPs, an investigation was conducted into their antimicrobial effects against the periodontitis-associated pathogen Porphyromonas gingivalis (P. gingivalis) in vitro. Furthermore, the antiperiodontitis potential of FZE NPs was evaluated in Sprague-Dawley (SD) rats of ligamentous periodontitis. In addition, toxicity evaluations indicated that the material had an acceptable biosafety profile in vitro and in vivo. In summary, the nanospheres (FZE NPs) represent a promising therapeutic strategy for the treatment of periodontitis.

Antibacterial activity of zinc oxide nanoparticles against Shewanella putrefaciens and its application in preservation of large yellow croaker (Pseudosciaena crocea)

Specific spoilage organisms (SSOs) are the key factors affecting the deterioration of large yellow croaker. This study investigated the antibacterial activity and mechanism of Zinc oxide nanoparticles (ZnO-NPs) against Shewanella putrefaciens. The effects of different concentrations of ZnO-NPs (0.5, 1, 2 mg/mL) combined with seawater slurry ice preservation on storage quality and microbial community of large yellow croaker were further investigated. The results showed that ZnO-NPs had a strong antibacterial effect on Shewanella putrefaciens, which destroyed the integrity of the cell membrane, resulting in nucleic acid leakage and increased electrical conductivity. In addition, ZnO-NPs could effectively inhibit the proliferation of microorganisms, slow down the rate of lipid oxidation, delay the rise of pH value and total volatile basic nitrogen, and maintain the color of fish. Among them, 2 mg/mL ZnO-NPs treatment showed the best preservation effect on large yellow croaker. High-throughput sequencing results showed that Pseudoalteromonas and Shewanella became the dominant spoilage bacteria with the extension of storage time. ZnO-NPs significantly reduced the relative abundance of dominant spoilage bacteria and changed the microbial composition of fish. Inhibition of the growth of SSOs was important for delaying spoilage and prolonging the shelf-life of large yellow croaker. Therefore, ZnO-NPs combined with seawater slurry ice preservation could be used as a new storage method, which provides a new idea for food quality and safety control.

Preparation and properties of PCL coaxial electrospinning films with shell loaded with CEO and core coated LEO nanoemulsions

During storage and transportation, the reduction of microbial contamination and management of the exudation of fluids from the fish can effectively mitigate spoilage and degradation of fish fillets. In this work, the coaxial electrospinning films loaded with natural plant preservatives, namely laurel essential oil (LEO) and clove essential oil (CEO), were prepared by the coaxial electrospinning method synergistic with nanoemulsion techniques, and the hydrophilic preservation pads were prepared. The morphology of the film fiber is clear, without beads or damage, with fiber diameters falling within the 230-260 nm range. It has a distinct core-shell structure, exceptional thermal stability, and strong antibacterial and antioxidant properties. The core-shell structure of the fiber subtly regulates the release of preservatives and significantly improves the utilization efficiency. At the same time, the synergistic use of two essential oils can reduce the amount while amplifying their effectiveness. The pads significantly slowed down the increase of key indicators of spoilage, such as total viable count (TVC), pH, thiobarbituric acid reactive substances (TBA), and total volatile base nitrogen (TVB-N), during the storage of the fish fillets. Furthermore, the pads effectively slowed down the decline in water-holding capacity, the deterioration of textural qualities, and the negative changes in the microstructure of the fish muscle. Ultimately, the pads notably delayed the spoilage of fish fillets, extending their shelf life from 5 d to 9 d. The efficient utilization of biological preservatives in this film can provide technical support for the development of food preservation materials.

Excitation of Reactive Oxygen Species and Damage to the Cell Membrane, Protein, and DNA are Important Inhibition Mechanisms of CO2 on Shewanella putrefaciens at 4 °C

To explore whether oxidative stress caused by 100% CO2 is an inhibitory mechanism against Shewanella putrefaciens, the oxidative stress reaction, antioxidant activity, and damage to the cell membrane, protein, and DNA of CO2-incubated S. putrefaciens at 4 °C were evaluated. Research demonstrated that CO2 caused more severe reactive oxygen species (ROS) accumulation. Simultaneously, weaker •OH/H2O2/O2•--scavenging activity and decreased T-VOC and GSH content were also observed. The activities of antioxidant enzymes (SOD, POD, CAT, and GPX) continuously declined, which might be attributed to the CO2-mediated decrease in the pH value. Correspondingly, the cell membrane was damaged with hyperpolarization, increased permeability, and more severe lipid peroxidation. The expression of total and membrane protein decreased, and the synthesis and activity of extracellular protease were inhibited. DNA was also subjected to oxidative damage and expressed at a lower level. All results collaboratively confirmed that ROS excitation and inhibition of antioxidant activity were important inhibition mechanisms of CO2 on S. putrefaciens.

Synthesis of acylated derivatives of alginate oligosaccharides and evaluation of their potential antibacterial activities against Staphylococcus aureus

Alginate oligosaccharides (AOS) are crucial carbohydrate-based biomaterial used in the synthesis of potential drugs and biological agents, but their antibacterial activities are not significant. In this study, AOS acylated derivatives were synthesized by grafting maleic anhydride (MA) onto AOS at varying ratios. Additionally, their inhibitory effects against Staphylococcus aureus were thoroughly investigated. Characterization of the AOS acylated derivatives (AOS-MA-x, where x = 1, 5, 10, and 20) was conducted using Fourier-transformed infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, and X-ray diffraction, which confirmed the successful synthesis of these derivatives. The bacteriostatic activity of the AOS-MA derivatives was assessed using growth curves and plate coating method, demonstrating significant antibacterial effects against S. aureus, as compared with AOS. Among these derivatives, AOS-MA-20 exhibited the most potent bacteriostatic activity and was selected for further investigation of its inhibitory mechanism. Scanning electron microscopy analysis revealed that treatment with AOS-MA-20 led to the lysis and rupture of S. aureus cells, expelling their intracellular contents. Moreover, AOS-MA-20 disrupted the integrity of cell wall and cell membrane, impacted ATPase activity, and inhibited the formation of biofilm to some extent, ultimately resulting in bacterial death. These findings lay a foundational framework for the development of environmentally friendly antimicrobial agents.

Membranes composed of poly(lactic acid)/poly(ethylene glycol) and Ora-pro-nóbis (Pereskia aculeata Miller) extract for dressing applications

Wounds are considered one of the most critical medical conditions that must be managed appropriately due to the psychological and physical stress they cause for patients, as well as creating a substantial financial burden on patients and global healthcare systems. Nowadays, there is a growing interest in developing nanofiber mats loaded with varying plant extracts to meet the urgent need for advanced wound ressings. This study investigated the development and characterization of poly(lactic acid) (PLA)/ poly(ethylene glycol) (PEG) nanofiber membranes incorporated with Ora-pro-nóbis (OPN; 12.5, 25, and 50 % w/w) by the solution-blow-spinning (SBS) technique. The PLA/PEG and PLA/PEG/OPN nanofiber membranes were characterized by scanning electron microscopy (SEM), thermal properties (TGA and DSC), Fourier transform infrared spectroscopy (FTIR), contact angle measurements and water vapor permeability (WVTR). In addition, the mats were analyzed for swelling properties in vitro cell viability, and fibroblast adhesion (L-929) tests. SEM images showed that smooth and continuous PLA/PEG and PLA/PEG/OPN nanofibers were obtained with a diameter distribution ranging from 171 to 1533 nm. The PLA/PEG and PLA/PEG/OPN nanofiber membranes showed moderate hydrophobicity (~109-120°), possibly preventing secondary injuries during dressing removal. Besides that, PLA/PEG/OPN nanofibers exhibited adequate WVTR, meeting wound healing requirements. Notably, the presence of OPN gave the PLA/PEG membranes better mechanical properties, increasing their tensile strength (TS) from 3.4 MPa (PLA/PEG) to 5.3 MPa (PLA/PEG/OPN), as well as excellent antioxidant properties (Antioxidant activity with approximately 45 % oxidation inhibition). Therefore, the nanofiber mats based on PLA/PEG, especially those incorporated with OPN, are promising options for use as antioxidant dressings to aid skin healing.

Research on topological effect of natural small molecule and high-performance antibacterial air filtration application by electrospinning

The application of natural small molecule (NSM) in electrospun fibers is the key to achieving powerful functionality and sustainable development. However, the lack of understanding regarding the mechanism for loading NSM hinders the advancement of high-performance functional fibers. This work clarified the loading mechanism of NSM in polymer solution by comparing the different behaviors of curcumin (Cur), phloretin (PL), and tea polyphenols (TP) blended ethyl cellulose (EC) solutions. We found that TP may lead to the folding of polymer chains due to its strongest hydrogen bond, which in turn promoted the dispersion of TP along the polymer chain. Therefore, TP could achieve good electrospinnability at the highest loading capacity (16 times the Cur and 4 times the PL). Finally, chitosan was introduced into EC/TP to prepare tree-like nanofibers, achieving high-performance antibacterial air filtration. The filtration efficiency for 0.3 μm NaCl particles, pressure drop, and quality factor were 99.991 %, 85.5 Pa, and 0.1089 Pa-1, respectively. The bacteriostatic rates against Escherichia coli and Staphylococcus aureus were all 99.99 %. This work will promote the application of NSM and the developments of multifunctional electrospun fibers and high-performance air filters.

Chestnut Shell Polyphenols Inhibit the Growth of Three Food-Spoilage Bacteria by Regulating Key Enzymes of Metabolism

The microbial contamination of food poses a threat to human health. Chestnut shells, which are byproducts of chestnut processing, contain polyphenols that exert various physiological effects, and thus have the potential to be used in food preservation. This study investigates the bacteriostatic effect and mechanism(s) of the action of chestnut shell polyphenols (CSPs) on three food-spoilage bacteria, namely Bacillus subtilis, Pseudomonas fragi, and Escherichia coli. To this end, the effect of CSPs on the ultrastructure of each bacterium was determined using scanning electron microscopy and transmission electron microscopy. Moreover, gene expression was analyzed using RT-qPCR. Subsequent molecular docking analysis was employed to elucidate the mechanism of action employed by CSPs via the inhibition of key enzymes. Ultrastructure analysis showed that CSPs damaged the bacterial cell wall and increased permeability. At 0.313 mg/mL, CSPs significantly increased the activity of alkaline phosphatase and lactate dehydrogenase, as well as protein leakage (p < 0.05), whereas the activity of the tricarboxylic acid (TCA) cycle enzymes, isocitrate dehydrogenase and α-ketoglutarate dehydrogenase, were inhibited (p < 0.05). The expression levels of the TCA-related genes gltA, icd, sucA, atpA, citA, odhA, IS178_RS16090, and IS178_RS16290 are also significantly downregulated by CSP treatment (p < 0.05). Moreover, CSPs inhibit respiration and energy metabolism, including ATPase activity and adenosine triphosphate (ATP) synthesis (p < 0.05). Molecular docking determined that proanthocyanidins B1 and C1, the main components of CSPs, are responsible for the antibacterial activity. Therefore, as natural antibacterial substances, CSPs have considerable potential for development and application as natural food preservatives.

Inhibition of Salmonella Enteritidis by Essential Oil Components and the Effect of Storage on the Quality of Chicken

This research investigates the antibacterial potential of plant essential oil components including thymol, carvacrol, citral, cinnamaldehyde, limonene, and β-pinene against Salmonella Enteritidis (S. Enteritidis). Through the determination of minimum inhibitory concentration, three kinds of natural antibacterial agents with the best inhibitory effect on S. Enteritidis were determined, namely thymol (128 μg/mL), carvacrol (256 μg/mL), and cinnamaldehyde (128 μg/mL). Physical, chemical, microbial, and sensory characteristics were regularly monitored on days 0, 2, 4, and 6. The findings of this study reveal that both thymol at MIC of 128 μg/mL and carvacrol at MIC of 256 μg/mL not only maintained the sensory quality of chicken, but also decreased the pH, moisture content, and TVB-N value. Additionally, thymol, carvacrol and cinnamaldehyde successfully inhibited the formation of S. Enteritidis biofilm, thereby minimizing the number of S. Enteritidis and the total aerobic plate count in chicken. Hence, thymol, carvacrol, and cinnamaldehyde have more effective inhibitory activities against S. Enteritidis, which can effectively prevent the spoilage of chicken and reduce the loss of its functional components.