Cell Membrane Disruption Research Articles

Design, synthesis, and bioactivity investigation of novel cyclic lipopeptide antibiotics targeting top-priority multidrug-resistant gram-negative bacteria

ObjectivesPolymyxins are the last-line therapy for top-priority multidrug-resistant (MDR) gram-negative bacteria. However, polymyxin nephrotoxicity impedes its clinical application. This study aimed to design, synthesize, and identify a novel and promising polymyxin derivative with high efficacy and low toxicity. MethodsTo design polymyxin derivatives, we reduced the hydrophobicity of the two hydrophobic domains (fatty acyl chain and D-Phe6-L-Leu7) and modified the positive charged L-2,4-diaminobutyric acid (Dab) residues. Twenty-five derivatives were synthesized, and their antibacterial activities in vitro and renal cytotoxicities were determined. The nephrotoxicity and pharmacokinetic parameters of compound 12 were examined in rats. Antibacterial efficacy in vivo was evaluated using a mouse systemic infection model. Surface plasmon resonance analysis, compound 12-rifampicin combination therapy, and scanning electron microscopy were used to study the mechanism of action of compound 12. ResultsThis research found a new compound, identified as compound 12, which showed similar or increased antibacterial activity against all tested sensitive and carbapenem-resistant gram-negative bacteria. It exhibited reduced renal cytotoxicity and nephrotoxicity, a favorable pharmacokinetic profile, and maintained or improved antibacterial efficacy in vivo. Importantly, its anti-Pseudomonas aeruginosa activity significantly improved. Compound 12, when combined with rifampicin, enhanced the activity of rifampin against gram-negative bacteria. Compound 12 also showed a high affinity for lipopolysaccharide and disrupted cell membrane integrity. ConclusionReducing the hydrophobicity of the two domains reduced renal cytotoxicity and nephrotoxicity. Shortening the side chain of Dab3 by one carbon maintained or increased its antibacterial activity both in vitro and in vivo. Furthermore, only the length of the side chain of Dab9 could be shortened by one carbon among the Dab1,5 and Dab8,9 residues. The bactericidal effects of compound 12 were related to the disruption of cell membrane integrity. Compound 12 may be a promising candidate for combating sensitive and carbapenem-resistant gram-negative bacterial infections, especially Pseudomonas aeruginosa.

Synergistic antimicrobial action of chlorogenic acid and ultraviolet-A (365 nm) irradiation; mechanisms and effects on DNA integrity

Chlorogenic acid (CGA) is abundant in various plants and notably in coffee beans. This study investigated the bactericidal activity of CGA combined with ultraviolet-A light (UVA, 365 nm) (CGA + UVA) against Escherichia coli DH5α, with the aim of developing novel strategies for food preservation and healthcare. CGA + UVA treatment was superiorin reducing bacterial survival than either treatment alone. At 20 J/cm2 and pH 7, CGA (0.3%) + UVA treatment resulted in only about a 3-log reduction in bacterial survival, whereas at 15 J/cm2 and pH 3, no surviving bacteria could be detected, demostrating that the treatment was more effective at acidic pH. CGA + UVA treatment was also bactericidal in green plum juice, confirming that its low pH-dependent property could be effective in acidic food products. To elucidate the bactericidal mechanism of CGA + UVA treatment, its effects on reactive oxygen species (ROS) generation, membrane integrity, and enzyme activity were measured. ROS generated via the type-1 reaction, such as hydrogen peroxide (H2O2) and hydroxyl radicals (·OH), were mainly detected. CGA + UVA disrupted the bacterial cell membrane, causing the leakage of cellular components, particularly proteins. CGA + UVA treatment also led to deoxyribonucleic acid (DNA) degradation and reduced succinate-coenzyme Q reductase activity by approximately 72 %. Furthermore, CGA + UVA treatment decreased β-lactamase activity and plasmid transforming efficacy with maximal reductions of 68 % and 98 %, respectively, highlighting its potential for increasing antibiotic susceptibility and preventing the spread of antimicrobial resistance. The results demonstrate that CGA + UVA treatment could be used to effectively combat antibiotic-resistant bacteria and prevent the spoilage of preserved foods or food poisoning.

Underlying mechanism of the microwave non-thermal effect as additional microbial inactivation on Clostridium sporogenes at pasteurization temperature level

Microwave processing can induce non-thermal effects that can inactivate additional levels of microorganisms at pasteurization temperature level (80–100 °C). The objective of this study was to investigate the mechanism behind the non-thermal effects of microwaves on vegetative cells of Clostridium sporogenes. Cell membrane damage were assessed through nuclear fluorescent dyes and by measuring nuclear acid and protein leakage. The results showed that microwave non-thermal effects and conventional water bath treatment resulted in similar nuclear acid leakage. However, microwave non-thermal effects inflicted more severe damage to the cell membranes of Clostridium sporogenes, resulting in increased protein leakage from both the inner of the cell and the cell membrane (A260 = 0.25 vs. 0.18). Consequently, it can be inferred that the inactivation of additional Clostridium sporogenes by microwave non-thermal effects is primarily attributed to the disruption of cell membranes induced by alternating electromagnetic fields, and this phenomenon is further potentiated at elevated temperatures.

A novel antimicrobial peptide WBp-1 from wheat bran: Purification, characterization and antibacterial potential against Listeria monocytogenes

This study introduces a novel antimicrobial peptide (AMP), WBp-1, isolated from wheat bran and purified via reversed-phase high-performance liquid chromatography. The amino acid sequence, determined as IITGASSGIGKAIAKHFI by LC–MS/MS, was composed predominantly of alkaline and hydrophobic residues. WBp-1 was predicted to be a stable, hydrophobic, cationic peptide with an α-helical structure. Moreover, it displayed significant antibacterial efficacy against Listeria monocytogenes, with a minimum inhibitory concentration of 150 μg/mL. Further mechanistic studies suggest that WBp-1 exerts its bactericidal activity by disrupting cell membrane integrity, impeding peptidoglycan synthesis by binding to penicillin-binding protein 4 via hydrogen bonding, increasing cell permeability, altering membrane potential and fluidity, and altering surface hydrophobicity. Interestingly, WBp-1 showed minimal hemolytic activity and cytotoxicity against LO2 cells, even at 16× MIC. These findings highlight the strong potential of WBp-1 as a novel antibacterial agent and food preservative against Listeria monocytogenes.

Exploring Biosurfactants: Sustainable Solutions for Overcoming Antimicrobial Resistance and Drug Adverse Effects

Antimicrobial resistance (AMR) poses a significant global health threat, necessitating the exploration of alternative strategies to combat microbial pathogens. Biosurfactants, natural compounds produced by microorganisms, have emerged as promising candidates due to their diverse biological activities and sustainable properties. This review aims to provide a comprehensive overview of biosurfactants' potential as sustainable solutions for overcoming AMR and mitigating drug adverse effects. We discuss the mechanisms of action of biosurfactants against microbial pathogens, highlighting their ability to disrupt cell membranes, inhibit biofilm formation, and modulate immune responses. Furthermore, we explore the biocompatibility and eco-friendly nature of biosurfactants, underscoring their advantages over synthetic drugs. However, challenges such as limited scalability and variability in production hinder their widespread adoption in pharmaceutical applications. We propose interdisciplinary research efforts to address these challenges and optimize the use of biosurfactants in combating AMR and minimizing drug adverse effects. Through collaborative initiatives and innovative approaches, biosurfactants hold immense promise as sustainable alternatives to conventional antimicrobial agents, paving the way for a healthier and more resilient future.

Probing the relevance of synergistic lipid membrane disruption to the eye irritation of binary mixed nonionic surfactants

Nonionic surfactant aerosols play a crucial role in many industries, but they can cause acute irritation to users’ eyes during spraying. This cytotoxic process is associated with corneal cell necrosis causing cell membrane disruption. Industrial grade surfactants are typically polydisperse mixtures described by their nominal chemical structure but how the polydispersity affects their interactions with cell membrane, remains largely unexplored. A better understanding could benefit product formulations to maximise their efficiency whilst minimising their toxicity to the users. In this study, poly-oxyethylene glycol monododecyl ethers (C12E4, C12E23) were used to form ideal binary surfactant mixtures. The cytotoxicities of mono and polydispersed surfactants towards human corneal epithelial cells were examined, followed by a series of biophysical characterisations of interactions between surfactants and model cell membranes. Notably, to probe the journey of individual C12E4 and C12E23 surfactant molecules across the cell membrane from a binary surfactant mixture, “two-colour” neutron reflection measurements were achieved via Hydrogen/Deuterium substitution. The relative distributions of C12E4 and C12E23 across cell membranes and their nanostructural conformations revealed a synergistic membrane-lytic ability initiated by surfactant mixing, with the more hydrophobic C12E4 exhibiting stronger membrane binding potency than the hydrophilic C12E23. The exact molar ratio of C12E4 against C12E23 in the mixture determined how the mixed surfactant interacted with the cell membrane, and how the process directly impacted cytotoxicity and eye irritation. Thus, the cytotoxicity of polydisperse surfactants is not the same as monodisperse surfactant of the same average structure. This work provides a useful basis for the assessment of surfactant mixing by balancing their efficiency and toxicity.

Antifungal effect of cinnamon essential oil against Penicillium oxalicum on rice noodles.

Plant essential oils have been extensively investigated for their application in food industry due to their broad antimicrobial spectrum and safety. However, rare studies investigated their application in decontaminating rice noodles from fungal contamination. In this study, the cinnamon essential oil was screened out among 12 species of plant essential oils, and its antifungal activity against Penicillium oxalicum isolated from rice noodles was investigated. Our study revealed that cinnamon essential oil inhibited the spore germination in a concentration-dependent manner, and a dosage of 0.025% (v/v) could entirely disable the spore germination. The disruption of the fungal plasma membrane was evidenced by the change of plasma membrane permeability and the leakage of cellular components. The cinnamon essential oil in vapor phase (0.00625% [v/v]) could totally inhibit the growth of fungi inoculated on rice noodles. In addition to the potential application in inactivating fungi germination on rice noodles, this study also demonstrated the feasibility of cinnamon essential as an environmental disinfectant. This study is the first report that cinnamon essential oil has been studied for decontaminating rice noodles from fungal contamination with P. oxalicum, which not only broadens the application field of plant essential oil but also provides an alternative approach for rice noodle preservation.

Novel antimicrobial peptides based on Protegrin-1: In silico and in vitro assessments

The development of antibiotic resistance has caused significant health problems. Antimicrobial peptides (AMPs) are considered next-generation antibiotics. Protegrin-1 (PG-1) is a β-hairpin AMP with a membrane-binding capacity. This study used twelve PG-1 analogs with different amino acid substitutions. Coarse-grained molecular dynamics (MD) simulations were used to assess these analogs, and their physicochemical properties were computed using the Antimicrobial Peptide Database. Three AMPs, PEP-D, PEP-C, and PEP-H, were chosen and synthesized for antibacterial testing. The microbroth dilution technique and hemolytic assays evaluated the antimicrobial efficacy and cellular toxicity. The checkerboard method was used to test the combined activity of AMP and standard antibiotics. Cell membrane permeability and electron microscopy were used to evaluate the mode of action. The chemical stability of the selective AMP, PEP-D, was assessed by a validated HPLC method. PEP-D consists of 16–18 amino acid residues and has a charge of +7 and a hydrophobicity of 44 %, similar to PG-1. It can efficiently inactivate bacteria by disrupting cell membranes and significantly reducing hemolytic activity. Chemical stability studies indicated that AMP was stable at 40 °C for six months under autoclave conditions. This study could introduce the potential therapeutic application of selective AMP as an anti-infective agent.

Expanding the horizons of photodynamic therapy: Indium metalated pyridinyl-based trans-A2B2 porphyrin as novel anti-biofilm agents

Modern medicine is exploring new approaches to combat bacterial infections associated with antibiotic-resistant bacteria and biofilms. Among these, antimicrobial photodynamic therapy (aPDT) stands out for its ability to target pathogenic microbes effectively. In this study, we investigated the antimicrobial potential of the newly synthesized indium metalated pyridinyl-based trans-A2B2 porphyrin complexes, 1a,b and 2a,b. The dicationic porphyrins, 1b and 2b, exhibited remarkable aPDT efficacy against both S. aureus and E. coli planktonic forms. Further investigation into the antimicrobial effects of the cationic porphyrins against E. coli and S. aureus biofilms revealed that both complexes (1b and 2b) exhibited high efficacy in aPDT attributed to tert-butyl and thiophene groups that enhance photo-physicochemical properties and bacterial membrane accumulation. Scanning electron microscopy (SEM) showed disruption of cell membranes following light exposure. Our work highlights the potential of aPDT as an effective strategy for managing biofilms. By harnessing the power of these innovative compounds, we contribute to the ongoing battle against microbial threats.

Free Energy Analysis of Peptide-Induced Pore Formation in Lipid Membranes by Bridging Atomistic and Coarse-Grained Simulations.

Antimicrobial peptides (AMPs) are attractive materials for combating the antimicrobial resistance crisis because they can kill target microbes by directly disrupting cell membranes. Although thousands of AMPs have been discovered, their molecular mechanisms of action are still poorly understood. One broad mechanism for membrane disruption is the formation of membrane-spanning hydrophilic pores which can be stabilized by AMPs. In this study, we use molecular dynamics simulations to investigate the thermodynamics of pore formation in model single-component lipid membranes in the presence of one of three AMPs: aurein 1.2, melittin and magainin 2. To overcome the general challenge of modeling long time scale membrane-related behaviors, including AMP binding, clustering, and pore formation, we develop a generalizable methodology for sampling AMP-induced pore formation. This approach involves the long equilibration of peptides around a pore created with a nucleation collective variable by performing coarse-grained simulations, then backmapping equilibrated AMP-membrane configurations to all-atom resolution. We then perform all-atom simulations to resolve free energy profiles for pore formation while accurately modeling the interplay of lipid-peptide-solvent interactions that dictate pore formation free energies. Using this approach, we quantify free energy barriers for pore formation without direct biases on peptides or whole lipids, allowing us to investigate mechanisms of pore formation for these 3 AMPs that are a consequence of unbiased peptide diffusion and clustering. Further analysis of simulation trajectories then relates variations in pore lining by AMPs, AMP-induced lipid disruptions, and salt bridges between AMPs to the observed pore formation free energies and corresponding mechanisms. This methodology and mechanistic analysis have the potential to generalize beyond the AMPs in this study to improve our understanding of pore formation by AMPs and related antimicrobial materials.

Natural agents derived Pickering emulsion enabled by silica nanoparticles with enhanced antibacterial activity against drug-resistant bacteria

The emergence of antibiotic-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) has become a global health challenge due to the overuse of antibiotics. Natural substances including enzymes and essential oils have shown great potential as alternative treatment options. However, the combinational use of these natural agents remains challenging due to the denaturation of enzymes upon direct contact with oil. In this study, we report the design of a Pickering emulsion containing two natural antibacterial agents, lysozyme and tea tree oil, stabilized by fractal silica nanoparticles. In this design, the enzyme activity is kept and the volatility problem of tea tree oil is mitigated. Due to synergistic bacterial cell wall digestion and membrane disruption functions, potent bactericidal efficacy in vitro against drug-resistant bacteria is achieved. The therapeutic potential is further demonstrated in a wound healing model with drug-resistant bacteria infection, better than a synthetic antibiotic, Ampicillin. This study opens new avenues for the development of natural product-based antimicrobial treatments with promising application potential.

Novel composite of nano zinc oxide and nano propolis as antibiotic for antibiotic-resistant bacteria: a promising approach

This study proposes an innovative approach to combat the escalating threat of antibiotic resistance in bacteria by introducing a novel ZnO-propolis nanocomposite (ZnO-P NCs). The overuse of antibiotics, particularly during events like the COVID-19 pandemic, has intensified bacterial resistance, necessitating innovative solutions. The study employs a cost-effective and controllable biosynthesis method to produce ZnO nanoparticles (ZnO-NPs), with propolis extract crucially contributing to the reduction and stabilization of Zn2+ ions. A biodegradable nano-propolis matrix is then created by incorporating ZnO-NPs, forming the ZnO-P NCs. Structural stability is confirmed through FT-IR and Zeta potential analysis, while nanoscale properties are validated via TEM, SEM, and XRD analyses. The antimicrobial efficacy of various substances, including propolis, nano propolis, ethanolic propolis extract, ZnO-NPs, and ZnO-P NCs, is assessed against Gram-negative and Gram-positive bacteria, alongside a comparison with 28 antibiotics. Among the bacteria tested, Pseudomonas aeruginosa PAO1 ATCC15692 was more sensitive (40 mm) to the biosynthesized nanocomposite ZnO-P NCs than to ZnO-NPs (38 mm) and nanopropolis (32 mm), while Escherichia coli was resistant to nanopropolis (0 mm) than to ZnO-NPs (31 mm), and ZnO-P NCs (34 mm). The study reveals a synergy effect when combining propolis with green-synthesized ZnO-NPs in the form of ZnO-P NCs, significantly improving their efficiency against all tested bacteria, including antibiotic-resistant strains like E. coli. The nanocomposite outperforms other materials and antibiotics, demonstrating remarkable antibacterial effectiveness. SEM imaging confirms the disruption of bacterial cell membranes by ZnO-NPs and ZnO-P NCs. The study emphasizes the potential applications of ZnO-NPs integrated into biodegradable materials and underscores the significance of the zinc oxide-propolis nanocomposite in countering antimicrobial resistance. Overall, this research offers a comprehensive solution to combat multidrug-resistant bacteria, opening avenues for novel approaches in infection control.

Advancing Antibiotic-Resistant Microbe Combat: Nanocarrier-Based Systems in Combination Therapy Targeting Quorum Sensing.

The increase in antibiotic-resistant bacteria presents a significant risk to worldwide public health, emphasizing the necessity of novel approaches to address infections. Quorum sensing, an essential method of communication among bacteria, controls activities like the formation of biofilms, the production of virulence factors, and the synthesis of secondary metabolites according to the number of individuals in the population. Quorum quenching, which interferes with these processes, emerges as a vital approach to diminish bacterial virulence and prevent biofilm formation. Nanocarriers, characterized by their small size, high surface-area-to-volume ratio, and modifiable surface chemistry, offer a versatile platform for the disruption of bacterial communication by targeting various stages within the quorum sensing pathway. These features allow nanocarriers to infiltrate biofilms, disrupt cell membranes, and inhibit bacterial proliferation, presenting a promising alternative to traditional antibiotics. Integrating nanocarrier-based systems into combination therapies provides a multi-pronged approach to infection control, enhancing both the efficacy and specificity of treatment regimens. Nonetheless, challenges related to the stability, safety, and clinical effectiveness of nanomaterial-based antimicrobial treatments remain. Continued research and development are essential to overcoming these obstacles and fully harnessing the potential of nano-antimicrobial therapies. This review emphasizes the importance of quorum sensing in bacterial behavior and highlights the transformative potential of nanotechnology in advancing antimicrobial treatments, offering innovative solutions to combat antibiotic-resistant pathogens.

Evaluation of the antifungal activity of novel bis-pyrazole carboxamide derivatives and preliminary investigation of the mechanism

To facilitate the development of novel agricultural succinate dehydrogenase inhibitor (SDHI) fungicides, we synthesized three series of derivatives by introducing phenyl pyrazole fragments into the structure of pyrazol-4-yl amides. The results of the bioactivity assay showed that most of the target compounds possessed varying degrees of inhibitory activity against the tested fungi. At a concentration of 100 mg/L, the compound B8 exhibited effective protective activity against S. sclerotiorum in vivo. Molecular docking analysis and succinate dehydrogenase (SDH) inhibition assay indicated that B8 was not a potential SDHI. The preliminary antifungal mechanism of studies showed that B8 induced a large amount of reactive oxygen species (ROS) and severe lipid peroxidation damage in S. sclerotiorum mycelium, resulting in mycelial rupture and disruption of the integrity of the cell membrane and leakage of soluble proteins, soluble sugars and nucleic acids. Further transcriptome analysis showed that compound B8 blocked various metabolic pathways by downregulating the differentially expressed genes (DEGs) catalase, disrupting hydrogen peroxide hydrolysis, accelerating membrane oxidative damage, and upregulating neutral ceramidase, accelerating sphingolipid metabolism to disrupt cell membrane structure and cell proliferation and differentiation, potentially accelerating cell death. The above results indicated that the potential target of these dis-pyrazole carboxamide derivatives may be the cell membrane of pathogenic fungi.

Resensitization to colistin results in rapid and stable recovery of adherence, serum resistance and ompW in Acinetobacter baumannii.

Colistin resistance in Acinetobacter baumannii is an emerging problem that limits antimicrobial therapy options. We isolated two pairs of colistin susceptible and colistin-resistant A. baumannii (K1007/K1006 and K408/K409) from two patients diagnosed with carbapenem-resistant A. baumannii infection. Colistin susceptible isolates were exposed to in vitro colistin induction for 50 generations. The selected cell populations were subjected to DNA and RNA sequencing and phenotypic assays. In the in vitro induction assay, K408 gained colistin resistance on the corresponding day of clinical resistance (K408-G25) and got resensitized to colistin in the consecutive generation (K408-G26). A significant upregulation of ompW, ata, adeFGH genes on K408-G25 was followed by a downregulation upon resensitization to colistin (G26). Despite the upregulation of the ompW gene in transcriptomic analysis, the ompW protein disappeared on K408-G25 and recovered in the resensitized generation (G26). In parallel, disrupted cell membrane integrity recovered in K408-G26. In the K408-G25, downregulation of pbpG and upregulation of pbp1a/pbp3 genes decreased serum-resistance which was reversed in the resensitized generation (G26). The K1007 did not gain colistin resistance amongst 50-generations, however, the generation corresponding to clinical resistance day (K1007-G9) had a similar trend with K408-G25. The clinical colistin-resistant K409 and K1006 had SNPs on pmrA and pmrB genes. In this study, we observed that A. baumannii regulates adhesion, efflux pumps and serum-resistance associated genes as an early response to colistin stress. Besides, the ompW protein disappears in the cell membrane of colistin resistant cells which recovers after resensitization to colistin. The lack of ompW protein in colistin-resistant cells should be taken into consideration for escape mutants in development of antivirulence vaccination or treatment options.

Antiviral effect of the viroporin inhibitors against Taiwan isolates of infectious bronchitis virus (IBV)

Coronaviruses (CoVs) are significant animal and human pathogens, characterized by being enveloped RNA viruses with positive-sense single-stranded RNA. The Coronaviridae family encompasses four genera, among which gammacoronaviruses pose a major threat to the poultry industry, which infectious bronchitis virus (IBV) being the most prominent of these threats. Particularly, IBV adversely affects broiler growth and egg production, causing substantial losses. The IBV strains currently circulating in Taiwan include the IBV Taiwan-I (TW-I) serotype, IBV Taiwan-II (TW-II) serotype, and vaccine strains. Therefore, ongoing efforts have focused on developing novel vaccines and discovering antiviral agents. The envelope (E) proteins of CoVs accumulate in the endoplasmic reticulum-Golgi intermediate compartment prior to virus budding. These E proteins assemble into viroporins, exhibiting ion channel activity that leads to cell membrane disruption, making them attractive targets for antiviral therapy.In this study, we investigated the E proteins of IBV H-120, as well as IBV serotypes TW-I and TW-II. E protein expression resulted in inhibited bacteria growth, increased permeability of bacteria to β-galactosidase substrates, and blocked protein synthesis of bacteria by hygromycin B (HygB). Furthermore, in the presence of E proteins, HygB also impeded protein translation in DF-1 cells and damaged their membrane integrity. Collectively, these findings confirm the viroporin activity of the E proteins from IBV H-120, IBV serotype TW-I, and IBV serotype TW-II. Next, the viroporin inhibitors, 5-(N,N-hexamethylene) amiloride (HMA) and 4,4’-diisothiocyano stilbene-2,2’-disulphonic acid (DIDS) were used to inhibit the viroporin activities of the E proteins of IBV H-120, IBV serotype TW-I, and IBV serotype TW-II. In chicken embryos and chickens infected with IBV serotypes TW-I and IBV TW-II, no survivors were observed at 6 and 11 days post-infection (dpi), respectively. However, treatments with both DIDS and HMA increased the survival rates in infected chicken embryos and chickens and mitigated histopathological lesions in the trachea and kidney. Additionally, a 3D pentameric structure of the IBV E protein was constructed via homology modeling. As expected, both inhibitors were found to bind to the lipid-facing surface within the transmembrane domain of the E protein, inhibiting ion conduction. Taken together, our findings provide comprehensive evidence supporting the use of viroporin inhibitors as promising antiviral agents against IBV Taiwan isolates.

Gallic Acid Based Polymers for Food Preservation: A Review.

The extensive usage of nonbiodegradable plastic materials for food packaging is a major environmental concern. To address this, researchers focus on developing biocompatible and biodegradable food packaging from natural biopolymers, such as polysaccharides, proteins, and polyesters. These biopolymer-based packaging materials extend the shelf life of food due to their inherent antimicrobial and antioxidant properties. An important additive that enhances these beneficial effects is gallic acid (GA), a naturally occurring phenolic compound. GA exhibits potent antioxidant activity by scavenging free radicals and excellent antimicrobial activity against a wide range of bacteria by disrupting cell membranes. These gallic acid based active packaging solutions have demonstrated remarkable abilities to inhibit lipid oxidation, enzymatic browning, and microbial contamination and even retard the ripening processes in mushrooms, walnuts, strawberries, fresh-cut apples, bananas, fish, pork, and beef. This review focuses on the antioxidant, antibacterial, and food preservation capabilities of GA-incorporated biodegradable food packaging materials as an eco-friendly alternative to conventional plastic packaging.

Metconazole inhibits fungal growth and toxin production in major Fusarium species that cause rice panicle blight

Rice panicle blight (RPB) caused by various Fusarium spp. is an emerging disease in the major rice-growing regions of China. Epidemics of this disease cause significant yield loss and reduce grain quality by contaminating panicles with different Fusarium toxins. However, there is currently no registered fungicide for the control of RPB in China. The 14α-demethylation inhibitor (DMI) fungicide metconazole has been shown to be effective against several Fusarium spp. that cause wheat head blight, wheat crown rot and maize ear rot. In this study, we investigated the specific activity of metconazole against six Fusarium spp. that cause RPB. Metconazole significantly inhibited mycelial growth, conidium formation, germination, germ tube elongation and major toxin production in Fusarium strains collected from major rice-growing regions in China, as well as disrupting cell membrane function by inhibiting ergosterol biosynthesis. Greenhouse experiments indicated a significant reduction in blight occurrence and toxin accumulation in rice panicles treated with metconazole. Overall, our study demonstrated the potential of metconazole for managing RPB and toxin contamination, as well as providing insight into its bioactivities and modes of action of metconazole against distinct Fusarium spp.

Production and characterisation of antioxidant and antibacterial polymeric nanoparticles loaded with Oenocarpus bataua phenolic extract

SummaryOne recent trend in the food industry is using natural antioxidants and antimicrobials as additives for developing multi‐functional packaging. In this study, phenolic compounds from patawa (PEP), a neglected Amazon palm tree, were extracted and encapsulated in nanoparticles based on acetylated cashew gum polysaccharide (acCGP) and chitosan (CS) using a nanoprecipitation technique. The primary objective was to evaluate the antioxidant activity and antibacterial properties of PEP and acCGP/CS@PEP. Results from HPLC‐MS showed that PEP is mainly composed of epicatechin, naringenin and rutin. acCGP/CS@PEP nanoparticles showed a spheric and smooth microstructure, observed with 40.1% PEP encapsulation into the nanoparticles. The main encapsulated phenolics were luteolin, quercetin and epicatechin. Also, FTIR spectroscopy, X‐ray diffraction and differential scanning calorimetry analyses evidenced the success of PEP encapsulation. Results from antioxidant activity evidenced that acCGP/CS@PEP has a DPPH scavenging activity 45‐fold higher than the unencapsulated PEP, a 5‐fold higher ferric reducing power and 20‐fold higher antioxidant potential against ABTS. Similarly, acCGP/CS@PEP had higher antibacterial activity against Escherichia coli (MIC = 2.24 mg mL−1), Salmonella enteritis (MIC = 4.48 mg mL−1) and Staphylococcus aureus (MIC = 4.48 mg mL−1). Analysis by SEM evidenced that acCGP/CS@PEP had a potent destructive effect with disruption of the bacterial cell membrane and liberation of cytoplasmic content. These findings demonstrated that PEP could be efficiently encapsulated in acCGP/CS nanoparticles, and this strategy could improve the efficiency of PEP as a bioactive compound for developing active packaging.

Marine biofouling mitigation of PDMS-based network coating with cross-linked contact- and release-active organoalkoxysilane

Poly (dimethylsiloxane) (PDMS) elastomer is one of key polymer resins for fouling release (FR) coatings, but it shows extremely poor antifouling (AF) activity in seawater since bacteria and diatoms could readily attach to surface. Modifying PDMS-based coatings via incorporating antifouling additives is effective for enhancing overall FR and AF activity. In this work, we prepared a well-defined organoalkoxysilane coating additive with quaternary ammonium and benzoisothiazolinone pendent groups, and the synthesized copolymers were covalently conjugated onto PDMS network in a one-pot reaction. AF and FR activities of the modified PDMS coatings were studied against soft fouling microorganisms. When microorganisms come into contact the coating surface, contact-active action mode works, quaternary ammonium groups could cause bacteria cell membrane disruption and microalgae photosynthesize inhibition via positive charge. Unexpectedly, a surprisingly lasting antimicrobial efficiency could be still observed in the neighboring coating, even the top-surface was completely covered with bacteria biofilm. Chemically conjugated benzoisothiazolinone could be sustainably released via side-group hydrolysis, thus, repelling and preventing the planktonic foulings from approaching the coating surface via release-active action mode. The modified PDMS coating with dual antifouling action modes could inhibit the biofilm formation at solid-liquid-air three-phase contact line, and could find valuable applications in marine transportation, water treatment and other antifouling fields.