Effect of structure on the interactions between five natural antimicrobial compounds and phospholipids of bacterial cell membrane on model monolayers

Combined application of bacteriophages with a competitive exclusion culture and carvacrol with organic acids can reduce Campylobacter in primary broiler production

For reducing Campylobacter (C.) in the food production chain and thus the risk to the consumer, the combined application of different measures as a multiple-hurdle approach is currently under discussion. This is the first study to investigate possible synergistic activities in vivo, aiming at reducing intestinal C. jejuni counts by administering (i) bacteriophages (phages) in combination with a competitive exclusion (CE) product and (ii) carvacrol combined with organic acids. The combined application of the two selected phages (Fletchervirus phage NCTC 12673 and Firehammervirus phage vB_CcM-LmqsCPL1/1) and the CE product significantly reduced C. jejuni loads by 1.0 log10 in cecal and colonic contents as well as in cloacal swabs at the end of the trial (33 and 34 days post hatch). The proportion of bacterial isolates showing reduced phage susceptibility ranged from 10.9% (isolates from cecal content) to 47.8% (isolates from cloacal swabs 32 days post hatch) for the Fletchervirus phage, while all tested isolates remained susceptible to the Firehammervirus phage. The use of carvacrol combined with an organic acid blend (sorbic acid, benzoic acid, propionic acid, and acetic acid) significantly reduced Campylobacter counts by 1.0 log10 in cloacal swabs on day 30 only.

Tuning the Probe-Bilayer Architecture of Silver Nanoneedle-based Ion Channel Probes

Ion channel probes, as one of the ion channel platforms, provide an appealing opportunity to perform localized detection with a high precision level. These probes come basically in two classes: glass and metal. While the glass-based probes showed the potential to be employed for molecular sensing and chemical imaging, these probes still suffer from limited resolution and lack of control over protein insertion. On the other hand, metal-based nanoneedle probes (gold and silver) have been recently developed to allow reducing probe dimensions to the nanoscale geometry. More specifically, silver probes are preferable owing to their ability to mitigate the channel current decay observed with gold probes and provide a stable DC channel current. However, there are still some challenges related to the probe design and bilayer curvature that render such probes insensitive to small changes in the tip-substrate distance. Herein, we introduce two main pathways to control the probe-bilayer architecture; the first is by altering the probe shape and geometry during the fabrication process of silver probes. The second pathway is by altering the surface characteristics of the silver probe via an electrophoretic deposition process. Our findings reveal that varying the electrochemical etching parameters results in different probe geometries and producing sharper tips with a 2-fold diameter reduction. In addition, the electrophoretic deposition of a cathodic paint on the silver nanoneedle surface led to a miniaturized exposed silver tip that enables the formation of a confined bilayer. We further investigated the characteristics of bilayers supported on both the sharper nanoneedles and the HSR-coated silver probes produced by controlling the etching conditions and electrodeposition process, respectively. We believe this work paves the way to rationally design silver nanoneedle ion channel probes, which are well suited for localized molecular sensing and chemical imaging.

Combinatorial effects between aromatic plant compounds and chlorhexidine digluconate against canine otitis-related Staphylococcus spp

The increasing prevalence of antimicrobial resistance among bacterial pathogens necessitates novel treatment strategies, particularly in veterinary medicine where otitis in dogs is very common in small animals' clinical routines. Considering this challenge, this study explores the efficacy of aromatic plant compounds (APC), including eugenol (EUG), trans-cinnamaldehyde (TC), and geraniol (GER), and their synergistic potential when combined with the antiseptic agent chlorhexidine (CLX), offering insight into alternative therapeutic approaches. The disk diffusion assay revealed differential sensitivity of Staphylococcus spp. strains to the tested compounds, with EUG and GER showing moderate inhibition zones and TC displaying considerably larger inhibition zones. Further analysis through MIC and MBC determinations suggested that EUG required the highest concentrations to inhibit and kill the bacteria, whereas TC and GER were effective at lower concentrations. Combined with CLX, all three plant-derived compounds demonstrated a significant enhancement of antibacterial activity, indicated by reduced MIC values and a predominantly synergistic interaction across the strains tested. GER was the most potent in combination with CLX, presenting the lowest mean FICi values and the highest fold reductions in MIC. This study emphasizes the APC's potential as an adjunct to conventional antimicrobial agents like CLX. The marked synergy observed, especially with GER, suggests that such combinations could be promising alternatives in managing bacterial otitis in dogs, potentially mitigating the impact of antibiotic resistance.

Study of the Membrane Activity of the Synthetic Peptide ∆M3 Against Extended-Spectrum β-lactamase Escherichia coli Isolates

Escherichia coli is the most common microorganism causing nosocomial or community-acquired bacteremia, and extended-spectrum β-lactamase-producing Escherichia coli isolates are identified worldwide with increasing frequency. For this reason, it is necessary to evaluate potential new molecules like antimicrobial peptides. They are recognized for their biological potential which makes them promising candidates in the fight against infections. The goal of this research was to evaluate the potential of the synthetic peptide ΔM3 on several extended-spectrum β-lactamase producing E. coli isolates. The antimicrobial and cytotoxic activity of the peptide was spectrophotometrically determined. Additionally, the capacity of the peptide to interact with the bacterial membrane was monitored by fluorescence microscopy and infrared spectroscopy. The results demonstrated that the synthetic peptide is active against Escherichia coli isolates at concentrations similar to Meropenem. On the other hand, no cytotoxic effect was observed in HaCaT keratinocyte cells even at 10 times the minimal inhibitory concentration. Microscopy results showed a permeabilizing effect of the peptide on the bacteria. The infrared results showed that ΔM3 showed affinity for the lipids of the microorganism's membrane. The results suggest that the ∆M3 interacts with the negatively charged lipids from the E. coli by a disturbing effect on membrane. Finally, the secondary structure experiments of the peptide showed a random structure in solution that did not change during the interaction with the membranes.

A Sigma1 Receptor Agonist Alters Fluidity and Stability of Lipid Monolayers

Interactions between the sigma1 receptor agonist PRE-084 and various lipid monolayers, including dipalmitoylphosphatidylcholine (DPPC), DPP-ethanolamine (DPPE), DPP-glycerol (DPPG), DPP-serine (DPPS), palmitoylsphingomyelin (PSM), and cholesterol (Ch), were investigated to elucidate the effects of PRE-084 on membrane fluidity and stability. Their interactions with sigma1 receptor agonists have potential implications for neuroprotection, antidepressant, analgesic, and cognitive enhancement effects. In this study, we observed that the presence of PRE-084 in the subphase led to increased fluidity in DPPC and DPPE monolayers, whereas decreasing fluidity was observed in DPPG, DPPS, and PSM monolayers. The interaction of PRE-084 with Ch monolayers was found to be distinct from its interaction with other lipids. Fluorescence microscopy images revealed changes in the size and shape of liquid-condensed domains in the presence of PRE-084, supporting the notion of altered membrane fluidity. Our findings provide new insights into the interaction of PRE-084 with lipid monolayers and its potential implications for biological and membrane science.

Study of Interactions between Saponin Biosurfactant and Model Biological Membranes: Phospholipid Monolayers and Liposomes

The aim of this study was to determine the effect of saponins-rich plant extract on two model biological membranes: phospholipid monolayers and liposomes. The Langmuir monolayer technique was used to study the interactions of model phospholipid membranes with saponins. The π-A isotherms were determined for DPPE (1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine) monolayer with the addition of various concentrations of licorice saponins extracts and subjected to qualitative as well as quantitative analysis. Additionally, relaxation studies of the obtained monolayers were carried out and morphological changes were examined using Brewster angle microscopy. Moreover, changes in the structure of phospholipid vesicles treated with solutions of saponins-rich plant extracts were assessed using the FTIR technique. The size and zeta potential of the liposomes were estimated based on DLS methods. The obtained results indicated that the saponins interact with the phospholipid membrane formed by DPPE molecules and that the stability of the mixed DPPE/saponins monolayer strongly depends on the presence of impurities in saponins. Furthermore, it was found that the plant extract rich in saponins biosurfactant interacts mainly with the hydrophilic part of liposomes.

Effect of partial O-methylation in dehydrodieugenol on its antitrypanosomal activity - correlation with the toxicity using cell membrane models

Biseugenol (1), a neolignan with antiprotozoal activity against Trypanosoma cruzi, was partially methylated, and the compound obtained - methyl biseugenol (2) - had its activity evaluated against the extracellular (trypomastigotes) and intracellular (amastigotes) forms of T. cruzi. It was observed that both compounds 1 and 2 exhibited similar effects against trypomastigotes (IC₅₀ of 11.7 and 16.2 μM, respectively), whereas compound 2 displayed higher activity against amastigotes (IC₅₀ = 8.2 μM) in comparison with biseugenol (IC₅₀ = 15.4 μM). Additionally, reduced toxicity against NCTC cells for compound 2 was observed (CC₅₀ > 200 μM), differently from compound 1 with CC₅₀ = 58.0 μM. Aiming to understand better the molecular mechanism of the biological action of compound 2, the prodrug was incorporated into cellular membrane models constituted of Langmuir monolayers of the lipids dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylethanolamine (DPPE), dipalmitoylphosphatidylserine (DPPS), and dipalmitoylphosphatidylglycerol (DPPG). The lipid-drug interaction was inferred through tensiometry, surface potential, infrared spectroscopy (PM-IRRAS), and Brewster angle microscopy (BAM). The prodrug expanded DPPC and DPPG monolayers and condensed DPPE ones, as well as presented characteristic behaviors regarding the chemical structure of the lipid considering expansion-compression curves, surface potential-area isotherms, and stability of previously compressed monolayers to relevant-biological surface pressures. PM-IRRAS indicated a molecular disorder for DPPC and DPPS alkyl chains in the presence of the drug. BAM revealed the presence of domains in the DPPG and DPPE monolayers, which was probably induced by the prodrug. These data suggest, in general, that the lipid composition modulates the interaction of compound 2, whose results are expected to correlate to its trypanocidal activity, which involves the plasma membrane of T. cruzi as the primary target, i.e., the first barrier that the compound should encounter to interact with the microorganism.

Bactericidal Activity of Carvacrol against Streptococcus pyogenes Involves Alteration of Membrane Fluidity and Integrity through Interaction with Membrane Phospholipids

Background: Carvacrol, a mono-terpenoid phenol found in herbs, such as oregano and thyme, has excellent antibacterial properties against Streptococcus pyogenes. However, its mechanism of bactericidal activity on S. pyogenes has not been elucidated. Objectives: This study investigated the bactericidal mechanism of carvacrol using three strains of S. pyogenes. Methods: Flow cytometry (FCM) experiments were conducted to determine carvacrol’s membrane permeabilization and cytoplasmic membrane depolarization activities. Protoplasts of S. pyogenes were used to investigate carvacrol’s effects on the membrane, followed by gel electrophoresis. The carvacrol-treated protoplasts were examined by transmission electron microscopy (TEM) to observe ultrastructural morphological changes. The fluidity of the cell membrane was measured by steady-state fluorescence anisotropy. Thin-layer chromatographic (TLC) profiling was conducted to study the affinity of carvacrol for membrane phospholipids. Results: Increased membrane permeability and decreased membrane potential from FCM and electron microscopy observations revealed that carvacrol killed the bacteria primarily by disrupting membrane integrity, leading to whole-cell lysis. Ultra-structural morphological changes in the membrane induced by carvacrol over a short period were confirmed using the S. pyogenes protoplast and membrane isolate models in vitro. In addition, changes in the other biophysical properties of the bacterial membrane, including concentration- and time-dependent increased fluidity, were observed. TLC experiments showed that carvacrol preferentially interacts with membrane phosphatidylglycerol (P.G.), phosphatidylethanolamine (P.E.), and cardiolipins (CL). Conclusions: Carvacrol exhibited rapid bactericidal action against S. pyogenes by disrupting the bacterial membrane and increasing permeability, possibly due to affinity with specific membrane phospholipids, such as P.E., P.G., and CL. Therefore, the bactericidal concentration of carvacrol (250 µg/mL) could be used to develop safe and efficacious natural health products for managing streptococcal pharyngitis or therapeutic applications.

Solid and Liquid Surface-Supported Bacterial Membrane Mimetics as a Platform for the Functional and Structural Studies of Antimicrobials

Increasing antibiotic resistance has provoked the urgent need to investigate the interactions of antimicrobials with bacterial membranes. The reasons for emerging antibiotic resistance and innovations in novel therapeutic approaches are highly relevant to the mechanistic interactions between antibiotics and membranes. Due to the dynamic nature, complex compositions, and small sizes of native bacterial membranes, bacterial membrane mimetics have been developed to allow for the in vitro examination of structures, properties, dynamics, and interactions. In this review, three types of model membranes are discussed: monolayers, supported lipid bilayers, and supported asymmetric bilayers; this review highlights their advantages and constraints. From monolayers to asymmetric bilayers, biomimetic bacterial membranes replicate various properties of real bacterial membranes. The typical synthetic methods for fabricating each model membrane are introduced. Depending on the properties of lipids and their biological relevance, various lipid compositions have been used to mimic bacterial membranes. For example, mixtures of phosphatidylethanolamines (PE), phosphatidylglycerols (PG), and cardiolipins (CL) at various molar ratios have been used, approaching actual lipid compositions of Gram-positive bacterial membranes and inner membranes of Gram-negative bacteria. Asymmetric lipid bilayers can be fabricated on solid supports to emulate Gram-negative bacterial outer membranes. To probe the properties of the model bacterial membranes and interactions with antimicrobials, three common characterization techniques, including quartz crystal microbalance with dissipation (QCM-D), surface plasmon resonance (SPR), and neutron reflectometry (NR) are detailed in this review article. Finally, we provide examples showing that the combination of bacterial membrane models and characterization techniques is capable of providing crucial information in the design of new antimicrobials that combat bacterial resistance.

Interaction of a Phospholipid and a Coagulating Protein: Potential Candidate for Bioelectronic Applications

In the present communication, we have investigated the interaction between a biomembrane component 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and a coagulating protein protamine sulfate (PS) using the Langmuir-Blodgett (LB) technique. The π-A isotherm, π-t characteristics, and analysis of isotherm curves suggested that PS strongly interacted with DOPC, affecting the fluidity of the DOPC layer. Electrical characterization indicates that PS as well as the PS-DOPC film showed resistive switching behavior suitable for Write Once Read Many (WORM) memory application. Trap-controlled space charge-limited conduction (SCLC) was the key mechanism behind such observed switching. The presence of DOPC affected the SCLC process, leading to lowering of threshold voltage (V _Th), which is advantageous in terms of lower power consumption.

Synergistic Interaction Between Paired Combinations of Natural Antimicrobials Against Poultry-Borne Pathogens

Natural antimicrobials (NAM) are promising candidates for the successful control of poultry-borne bacteria, carrying potent antimicrobial activity (AMA) against a wide range of multidrug-resistant pathogens. Individual activities of carvacrol, eugenol, trans-cinnamaldehyde, oregano, and thymol, along with the combined activity of paired compounds, were examined using broth microdilution and checkerboard techniques. The characteristic interactions between the compounds were calculated using an improved method, based on combination index (CI) values. The bacteria examined herein were selected due to their known genetic resistance to at least one antibiotic. Our results indicated that thymol was most effective, exhibiting the lowest minimum inhibitory concentration (MIC) value against Salmonella pullorum, Escherichia coli, and Klebsiella pneumoniae, establishing the order of antimicrobial efficacy as: thymol > oregano > carvacrol > trans-cinnamaldehyde > eugenol. In the interaction study, the paired combination of carvacrol and thymol showed synergistic effects and was highly effective in reducing the antibiotic resistance of all the evaluated pathogens. Notably, all CI values were <1.0 in evaluations of S. pullorum, indicating the absence of antagonism between eugenol and thymol (or oregano). In K. pneumoniae, majority of CI values, which had a few concentration points, were smaller than 1.0, indicating a synergistic effect between eugenol and carvacrol (oregano or thymol), and trans-cinnamaldehyde and carvacrol. In E. coli, apart from some concentration points, some CI values were smaller than 1.0, demonstrating a synergistic effect between eugenol and carvacrol, and thymol and carvacrol (eugenol or oregano). It is therefore of great significance to investigate and illuminate the minimal effect concentration of these five components when they are used in combination as feed additives. Moreover, the improved evaluation method of this study provides a precise and extensive means to assess the synergistic effects of NAM.

Infrared Spectroscopic Study of Multi-Component Lipid Systems: A Closer Approximation to Biological Membrane Fluidity

Membranes are essential to cellular organisms, and play several roles in cellular protection as well as in the control and transport of nutrients. One of the most critical membrane properties is fluidity, which has been extensively studied, using mainly single component systems. In this study, we used Fourier transform infrared spectroscopy to evaluate the thermal behavior of multi-component supported lipid bilayers that mimic the membrane composition of tumoral and non-tumoral cell membranes, as well as microorganisms such as Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus. The results showed that, for tumoral and non-tumoral membrane models, the presence of cholesterol induced a loss of cooperativity of the transition. However, in the absence of cholesterol, the transitions of the multi-component lipid systems had sigmoidal curves where the gel and fluid phases are evident and where main transition temperatures were possible to determine. Additionally, the possibility of designing multi-component lipid systems showed the potential to obtain several microorganism models, including changes in the cardiolipin content associated with the resistance mechanism in Staphylococcus aureus. Finally, the potential use of multi-component lipid systems in the determination of the conformational change of the antimicrobial peptide LL-37 was studied. The results showed that LL-37 underwent a conformational change when interacting with Staphylococcus aureus models, instead of with the erythrocyte membrane model. The results showed the versatile applications of multi-component lipid systems studied by Fourier transform infrared spectroscopy.

Hydrophobic Chitosan Nanoparticles Loaded with Carvacrol against Pseudomonas aeruginosa Biofilms

Pseudomonas aeruginosa infections have become more challenging to treat and eradicate due to their ability to form biofilms. This study aimed to produce hydrophobic nanoparticles by grafting 11-carbon and three-carbon alkyl chains to a chitosan polymer as a platform to carry and deliver carvacrol for improving its antibacterial and antibiofilm properties. Carvacrol–chitosan nanoparticles showed ζ potential values of 10.5–14.4 mV, a size of 140.3–166.6 nm, and an encapsulation efficiency of 25.1–68.8%. Hydrophobic nanoparticles reduced 46–53% of the biomass and viable cells (7–25%) within P. aeruginosa biofilms. Diffusion of nanoparticles through the bacterial biofilm showed a higher penetration of nanoparticles created with 11-carbon chain chitosan than those formulated with unmodified chitosan. The interaction of nanoparticles with a 50:50 w/w phospholipid mixture at the air–water interface was studied, and values suggested that viscoelasticity and fluidity properties were modified. The modified nanoparticles significantly reduced viable P. aeruginosa in biofilms (0.078–2.0 log CFU·cm⁻²) and swarming motility (40–60%). Furthermore, the formulated nanoparticles reduced the quorum sensing in Chromobacterium violaceum. This study revealed that modifying the chitosan polarity to synthesize more hydrophobic nanoparticles could be an effective treatment against P. aeruginosa biofilms to decrease its virulence and pathogenicity, mainly by increasing their ability to interact with the membrane phospholipids and penetrate preformed biofilms.

Effect of Essential Oils on Growth Inhibition, Biofilm Formation and Membrane Integrity of Escherichia coli and Staphylococcus aureus

Biofilm as a cellular conformation confers survival properties to microbial populations and favors microbial resistance. Here, we investigated the antimicrobial, antibiofilm, antimotility, antihemolytic activity, and the interaction with synthetic membranes of 15 essential oils (EOs) on E. coli ATCC 25922 and S. aureus ATCC 29213. Antimicrobial activity of EOs was determined through microdilution method; development of the biofilm was assessed using the crystal violet assay and SEM microscopy. Results indicate that Lippia origanoides thymol–carvacrol II chemotype (LTC II) and Thymus vulgaris (TV) exhibited a significant antibacterial activity, with MIC values of 0.45 and 0.75 mg/mL, respectively. The percentage of biofilm formation inhibition was greater than 70% at subinhibitory concentrations (MIC₅₀) for LTC II EO. The results demonstrate that these two oils had significantly reduced the hemolytic effect of S. aureus by 54% and 32%, respectively, and the mobility capacity by swimming in E. coli with percentages of decrease of 55% and 47%, respectively. The results show that LTC II and TV EOs can interact with the hydrophobic core of lipid bilayers and alter the physicochemical properties of membranes. The findings suggest that LTC II and TV oils may potentially be used to aid in the treatment of S. aureus and E. coli infections.

Encapsulated Plant-Derived Antimicrobial Reduces Enteric Bacterial Pathogens on Melon Surfaces during Differing Contamination and Sanitization Treatment Scenarios

This study aimed to quantify survival in Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium isolates on melon rind surface samples achieved by sanitizer treatment under three differing melon contamination and sanitization scenarios. Sanitizing treatments consisted of the plant-derived antimicrobial (PDA) essential oil component (EOC) geraniol (0.5 wt.%) entrapped in the polymeric surfactant Pluronic F-127 (GNP), 0.5 wt.% unencapsulated geraniol (UG), 200 mg/L hypochlorous acid at pH 7.0 (HOCl), and a sterile distilled water wash (CON). The experimental contamination and sanitization scenarios tested were: (1) pathogen inoculation preceded by treatment; (2) the pathogen was inoculated onto samples twice with sanitizing treatment applied in between inoculation events; or (3) pathogen inoculation followed by sanitizing treatment. Reductions in the numbers of surviving pathogens were dependent on the sanitizing treatment, the storage period, or the interaction of these effects. GNP treatment provided the greatest reductions in surviving pathogen counts on melon rinds, but these did not regularly statistically differ from those achieved by HOCl or UG treatment. GNP treatment provided the best pathogen control under differing conditions of pre- and/or post-harvest cross-contamination and can be applied to reduce the risk of pathogen transmission on melon rinds.

From plants to antimicrobials: Natural products against bacterial membranes

Bacterial membrane barrier provides a cytoplasmic environment for organelles of bacteria. The membrane is composed of lipid compounds containing phosphatide protein and a minimal amount of sugars, and is responsible for intercellular transfers of chemicals. Several antimicrobials have been found that affect bacterial cytoplasmic membranes. These compounds generally disrupt the organization of the membrane or perforate it. By destroying the membrane, the drugs can permeate and replace the effective macromolecules necessary for cell life. Furthermore, they can disrupt electrical gradients of the cells through impairment of the membrane integrity. In recent years, considering the spread of microbial resistance and the side effects of antibiotics, natural antimicrobial compounds have been studied by researchers extensively. These molecules are the best alternative for controlling bacterial infections and reducing drug resistance due to the lack of severe side effects, low cost of production, and biocompatibility. Better understanding of the natural compounds' mechanisms against bacteria provides improved strategies for antimicrobial therapies. In this review, natural products with antibacterial activities focusing on membrane damaging mechanisms were described. However, further high-quality research studies are needed to confirm the clinical efficacy of these natural products.

Encapsulation of phenolic compounds within nano/microemulsion systems: A review

Phenolic compounds (phenolics) have received great attention in the food, pharmaceutical and nutraceutical industries due to their health-promoting attributes. However, their extensive use is limited mainly due to their poor water dispersibility and instability under both processing conditions and/or gastrointestinal interactions, affecting their bioavailability/bioaccessibility. Therefore, different nanocarriers have been widely used to encapsulate phenolics and overcome the aforementioned challenges. To the best of our knowledge, besides many research studies, no comprehensive review on encapsulation of phenolics by microemulsions (MEs) and nanoemulsions (NEs) has been published so far. The present study was therefore attempted to review the loading of phenolics into MEs and NEs. In addition, the fundamental characteristics of the developed systems such as stability, encapsulation efficiency, cytotoxicity, bioavailability and releasing rate are also discussed. Both MEs and NEs are proved as appropriate vehicles to encapsulate and protect phenolics which may expand their applications in foods, supplements and pharmaceuticals.

Antimicrobial-Loaded Polymeric Micelles Inhibit Enteric Bacterial Pathogens on Spinach Leaf Surfaces During Multiple Simulated Pathogen Contamination Events

Protecting fresh-packed produce microbiological safety against pre- and post-harvest microbial pathogen contamination requires innovative antimicrobial strategies. Although largely ignored in the scientific literature, there exists the potential for gross failure in food safety protection of fresh fruits and vegetables leading to opportunity for multiple produce contamination events to occur during production and post-harvest handling of food crops. The primary objective of this research was to determine the efficacy of plant-derived antimicrobial-loaded nanoparticles to reduce Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium on spinach leaf surfaces whilst simulating multiple pathogen contamination events (pre-harvest and post-harvest). Spinach samples were inoculated with a blend of E. coli O157:H7 and S. Typhimurium, each diluted to ~8.0 log10 CFU/mL. The inoculated samples were then submerged in solutions containing nanoparticles loaded with geraniol (GPN; 0.5 wt.% geraniol), unencapsulated geraniol (UG; 0.5 wt.%), or 200 ppm chlorine (HOCl; pH 7.0), with untreated samples serving for controls. Following antimicrobial treatment application, samples were collected for surviving pathogen enumeration or were placed under refrigeration (5°C) for up to 10 days, with periodic enumeration of pathogen loads. After 3 days of refrigerated storage, all samples were removed, aseptically opened and subjected to a second inoculation with both pathogens. Treatment of spinach surfaces with encapsulated geraniol reduced both pathogens to non-detectable numbers within 7 days of refrigerated storage, even with a second contamination event occurring 3 days after experiment initiation. Similar results were observed with the UG treatment, except that upon recontamination at day 3, a higher pathogen load was detected on UG-treated spinach vs. GPN-treated spinach. These data fill a research gap by providing a novel tool to reduce enteric bacterial pathogens on spinach surfaces despite multiple contamination events, a potential food safety risk for minimally processed edible produce.

Preparation of Fraxetin Long Circulating Liposome and Its Anti-enteritis Effect

This study sought to improve the oral bioavailability and enhance the anti-enteritis effect of fraxetin by incorporating it into long circulating liposomes (F-LC-Lipo). The optimal formulation of F-LC-Lipo was obtained via orthogonal design. The particle size, morphology, encapsulation efficiency, stability, and anti-enteritis effect of F-LC-Lipo were evaluated. The particle size of F-LC-Lipo was 166.65 ± 8.75 nm with entrapment efficiency (EE) of 92.18 ± 0.17%. The release rate in different dissolution media (pH 1.2 HCl, DDW, and pH 7.4 PBS) was significantly higher than that of fraxetin solution. Compared with the free fraxetin solution, F-LC-Lipo increased oral bioavailability of fraxetin by 4.43 times (443%). More importantly, F-LC-Lipo could improve the levels of interleukin-1 beta (IL-1β), IL-6, malondialdehyde (MDA), superoxide dismutase (SOD), tumor necrosis factor-alpha (TNF-α), C-reactive protein (CRP), prostaglandin E2 (PEG2), and IL-10 in rats with enteritis. Overall, these results suggested that LC-Lipo may serve as a potential carrier for improving the solubility and oral bioavailability of fraxetin as well as improving its enteritis effect.

Combined Effect of Nitrofurantoin and Plant Surfactant on Bacteria Phospholipid Membrane

Due to the increasing use of antibiotics, measures are being taken to improve their removal from the natural environment. The support of biodegradation with natural surfactants that increase the bioavailability of impurities for microorganisms that degrade them, raises questions about their effect on bacterial cells. In this paper we present analysis of the interaction of nitrofurantoin (NFT) and saponins from the Saponaria officinalis on the environmental bacteria membrane and the model phospholipid membrane mimicking it. A wide perspective of the process is provided with the Langmuir monolayer technique and membrane permeability test with bacteria. The obtained results showed that above critical micelle concentration (CMC), saponin molecules are incorporated into the POPE monolayer, but the NFT impact was ambiguous. What is more, differences in membrane permeability between the cells exposed to NFT in comparison to that of the non-exposed cells were observed above 1.0 CMC for Achromobacter sp. KW1 or above 0.5 CMC for Pseudomonas sp. MChB. In both cases, NFT presence lowered the membrane permeability. Moreover, the Congo red adhesion to the cell membrane also decreased in the presence of a high concentration of surfactants and NFT. The results suggest that saponins are incorporated into the bacteria membrane, but their sugar hydrophilic part remains outside, which modifies the adsorption properties of the cell surface as well as the membrane permeability.

Entrapment of a phage cocktail and cinnamaldehyde on sodium alginate emulsion-based films to fight food contamination by Escherichia coli and Salmonella Enteritidis

Notwithstanding the implementation of good processing practices in food companies and appropriate washing of food products by the consumer, Salmonella and Escherichia coli outbreaks continue to occur. In this study, different combinations of bacteriophages (phages) and cinnamaldehyde (CNMA) were incorporated on sodium alginate emulsion-based films to impart them with antimicrobial activity towards S. Enteritidis and E. coli. Films were prepared by casting and they were characterized in terms of CNMA and/or phages loading, thickness, moisture content, water vapor permeability (WVP), swelling index (SW), chemical interactions by FTIR, surface morphology by SEM and antimicrobial performance. Results showed that phages incorporation was not compromised by CNMA as evidenced by their viability inside the films. Increasing CNMA concentration yielded formulations less heterogeneous and a higher amount of CNMA loaded. Films characterization revealed that, in general, phages incorporation did not introduce significant changes on films parameters while the presence of CNMA increased the roughness, thickness and swelling ability of films. Sodium alginate films incorporated with EC4 and φ135 phages displayed antimicrobial activity against E. coli and S. Enteritidis, respectively, while CNMA empowered the films with activity against both species. Combination of both phages with the higher concentration of CNMA resulted in a synergic antimicrobial effect against E. coli and a facilitative effect against Salmonella. Overall, incorporation of EC4 and φ135 phages together with CNMA on alginate emulsion-based films holds great potential to be further applied in food packaging to prevent food contamination.

Influence of stressing conditions caused by organic acids and salts on tolerance of Listeria monocytogenes to Origanum vulgare L. and Rosmarinus officinalis L. essential oils and damage in bacterial physiological functions

This study evaluated whether the pre-exposure (24, 48 and 72 h) to sublethal conditions caused by acetic acid (AA), lactic acid (LA), sodium chloride (NaCl) or potassium chloride (KCl) could induce increased cross-tolerance to the essential oils from Origanum vulgare L. (OVEO) and Rosmarinus officinalis L. (ROEO) in different Listeria monocytogenes strains. Damage to membrane integrity, membrane potential, enzymatic activity and efflux activity in L. monocytogenes cells pre-exposed (24 h) to AA or NaCl and further treated with OVEO or ROEO (8 and 24 h) were investigated using flow cytometry (FC). Results of minimum inhibitory concentration (MIC) modulation test showed that pre-exposure to sublethal conditions caused by organic acids or salts increased cross-tolerance only to ROEO, since MIC of ROEO increased up to 4.8-fold against pre-exposed cells. Otherwise, MIC of OVEO against these pre-exposed cells was up to ten-fold lower than that observed against not pre-exposed cells, indicating no increase in cross-tolerance. Bacterial survival assays showed that ROEO only decreased the counts over time of cells not pre-exposed to organic acids or salts, while OVEO decreased similarly or more the counts of pre-exposed cells compared to not pre-exposed cells. Results of FC analysis showed that all measured functions in L. monocytogenes cells pre-exposed to AA or NaCl and treated with OVEO or ROEO were affected, although with different intensities. These data indicate that exposure to sublethal conditions imposed by organic acids or salts could result in a phenotype of increased cross-tolerance to ROEO but not to OVEO in L. monocytogenes.

Insights into the Relationships Between Herbicide Activities, Molecular Structure and Membrane Interaction of Cinnamon and Citronella Essential Oils Components

Since the 50’s, the massive and “environmental naïve” use of synthetic chemistry has revolutionized the farming community facing the dramatic growth of demography. However, nowadays, the controversy grows regarding the long-term harmful effects of these products on human health and the environment. In this context, the use of essential oils (EOs) could be an alternative to chemical products and a better understanding of their mode of biological action for new and optimal applications is of importance. Indeed, if the biocidal effects of some EOs or their components have been at least partly elucidated at the molecular level, very little is currently known regarding their mechanism of action as herbicides at the molecular level. Here, we showed that cinnamon and Java citronella essential oils and some of their main components, i.e.,, cinnamaldehyde (CIN), citronellal (CitA), and citronellol (CitO) could act as efficient herbicides when spread on A. thaliana leaves. The individual EO molecules are small amphiphiles, allowing for them to cross the mesh of cell wall and directly interact with the plant plasma membrane (PPM), which is one of the potential cellular targets of EOs. Hence, we investigated and characterized their interaction with biomimetic PPM while using an integrative biophysical approach. If CitO and CitA, maintaining a similar chemical structure, are able to interact with the model membranes without permeabilizing effect, CIN belonging to the phenylpropanoid family, is not. We suggested that different mechanisms of action for the two types of molecules can occur: while the monoterpenes could disturb the lipid organization and/or domain formation, the phenylpropanoid CIN could interact with membrane receptors.

The influence of terpinen-4-ol and eucalyptol - The essential oil components - on fungi and plant sterol monolayers

Antifungal and herbicidal activity of terpenes, being the components of the essential oils, is directly related to the incorporation of these compounds into cellular membranes. Thus, the differences in the lipid composition of various pathogenic membranes may be the factor determining the activity of these molecules. One of the class of lipids, which form the membrane environment are sterols. The aim of this work was to compare the effect of two terpenes: terpinen-4-ol and eucalyptol on the monolayers formed by ergosterol and β - sitosterol, which are the components of fungi and plant membranes, respectively. The modifications in the sterol monolayer properties were investigated in the surface pressure-area measurements and penetration studies as well as in a micrometer scale (Brewster angle microscopy experiments) and in nanoscale (GIXD technique). It was evidenced that although at higher surface pressure the terpene molecules are in part removed from the interface, they are able to substantially modify the condensation, morphology and molecular organization of the sterol film. It was also found that the incorporation of terpenes into sterol films is comparable for both sterols, however, β - sitosterol monolayers properties are affected more strongly than ergosterol films. Finally, the analysis of the results of the studies performed on model membrane systems and the results of antimicrobial studies reported in literature, enabled us to suggest that the activity of terpenes depends on the membrane composition and that the sterol concentration may be important from the point of view of antifungal effect of terpinen-4-ol and eucalyptol.

The cyclic peptide labaditin does not alter the outer membrane integrity of Salmonella enterica serovar Typhimurium

Antimicrobial peptides are a promising class of new antibiotics with the ability to kill bacteria by disrupting their cell membrane, which is especially difficult for Gram-negative bacteria whose cell wall contains an outer layer of lipopolysaccharides (LPS). Here we show that the cyclic decapeptide Labaditin (Lo), with proven activity against the Gram-positive Staphylococcus aureus and Streptococcus mutans, is not able to kill the Gram-negative Salmonella enterica serovar Typhimurium (S.e.s. Typhimurium). We found that Lo induced significant changes in the surface pressure isotherms of Langmuir monolayers representing the Salmonella enterica serovar Typhimurium inner membrane (S.e.s. Typhimurium IM), and caused leakage in large unilamellar vesicles made with this IM lipid composition. On the basis of these results one should expect bactericidal activity against S.e.s. Typhimurium. However, Lo could not interact with a monolayer of LPS, causing no significant changes in either the surface pressure isotherms or in the polarization-modulated infrared reflection absorption spectra (PM-IRRAS). Therefore, the failure of Lo to kill S.e.s. Typhimurium is associated with the lack of interaction with LPS from the outer bacteria membrane. Our approach with distinct monolayer compositions and combined techniques to investigate molecular-level interactions is useful for drug design to fight antibiotic-resistant bacteria.

Thermodynamic Characterization of Mixed Monolayers of a Novel Oxazolidine Derivative and Phospholipids

Oxazolidine derivatives (OxD) are five ring-membered compounds that contain at least one oxygen and nitrogen in their molecular structure. OxD are known due to several therapeutic activities such as anticancer and antibiotic properties. In this paper, we performed a thermodynamic analysis of the mixed films composed by dipalmitoylphosphatidylglycerol (DPPG), dipalmitoylphosphoethanolamine (DPPE), dipalmitoyl phosphatidylcholine (DPPC) or L-α phosphatidylcholine (PC) with a novel oxazolidine derivate (OxD). Relevant thermodynamic parameters such as excess areas (ΔAE), excess free energies (ΔG), and Gibbs free energy of mixing (AG^mix) were derived from the surface pressure data. The topographical analysis was performed using atomic force microscopy. Based on the calculated values of the thermodynamic parameters, we observed that the miscibility of the mixed films was directly dependent on their composition. DPPG/OxD and DPPE/OxD systems present the best-mixed character at low pressures at OxD molar fraction equivalent to 0.25.

Structure Dependence of Pyridine and Benzene Derivatives on Interactions with Model Membranes

Pyridine-based small-molecule drugs, vitamins, and cofactors are vital for many cellular processes, but little is known about their interactions with membrane interfaces. These specific membrane interactions of these small molecules or ions can assist in diffusion across membranes or reach a membrane-bound target. This study explores how minor differences in small molecules (isoniazid, benzhydrazide, isonicotinamide, nicotinamide, picolinamide, and benzamide) can affect their interactions with model membranes. Langmuir monolayer studies of dipalmitoylphosphatidylcholine (DPPC) or dipalmitoylphosphatidylethanolamine (DPPE), in the presence of the molecules listed, show that isoniazid and isonicotinamide affect the DPPE monolayer at lower concentrations than the DPPC monolayer, demonstrating a preference for one phospholipid over the other. The Langmuir monolayer studies also suggest that nitrogen content and stereochemistry of the small molecule can affect the phospholipid monolayers differently. To determine the molecular interactions of the simple N-containing aromatic pyridines with a membrane-like interface, ¹H one-dimensional NMR and ¹H-¹H two-dimensional NMR techniques were utilized to obtain information about the position and orientation of the molecules of interest within aerosol-OT (AOT) reverse micelles. These studies show that all six of the molecules reside near the AOT sulfonate headgroups and ester linkages in similar positions, but nicotinamide and picolinamide tilt at the water-AOT interface to varying degrees. Combined, these studies demonstrate that small structural changes of small N-containing molecules can affect their specific interactions with membrane-like interfaces and specificity toward different membrane components.

Vesicles mimicking normal and cancer cell membranes exhibit differential responses to the cell-penetrating peptide Pep-1

The cell-penetrating peptide (CPP) Pep-1 presents a great potential in drug delivery due to its intrinsic property to cross plasma membrane. However, its mechanism of entry into the cell remains unresolved. In this study, we compare the selectivity of Pep-1 towards vesicles mimicking normal and cancer cell membranes. The interaction was performed in a wide range of peptide-to-lipid molar ratios using infrared (IR), fluorescence, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. At low peptide concentration, fluorescence experiments show that lipid-phosphatidylserine (PS) seems to enable Pep-1 translocation into cancer cell membrane as evidenced by the blue shift of its maximal emission wavelength. DSC data show that Pep-1 induces segregation of lipids. At high peptide concentration, IR data indicate that the interaction of Pep-1 is relatively stronger with normal cell membrane than with cancer cell membrane through the phosphate groups, while the interaction is weaker with normal cell membrane than with cancer cell membrane through the carbonyl groups. TGA and DSC data reveal that vesicles of normal cell membrane are thermally more stable than vesicles of cancer cell membrane. This suggests that the additional lipid PS included in cancer cell membrane has a destabilizing effect on the membrane structure. SEM images reveal that Pep-1 form superstructures including spherical particles and fibrils in the presence of both model membranes. PS seems to enhance peptide transport across cellular membranes. The biophysical techniques in this study provide valuable insights into the properties of CPPs in drug delivery systems.

Chemistry, Antimicrobial Mechanisms, and Antibiotic Activities of Cinnamaldehyde against Pathogenic Bacteria in Animal Feeds and Human Foods

Cinnamaldehyde is a major constituent of cinnamon essential oils produced by aromatic cinnamon plants. This compound has been reported to exhibit antimicrobial properties in vitro in laboratory media and in animal feeds and human foods contaminated with disease-causing bacteria including Bacillus cereus, Campylobacter jejuni, Clostridium perfringens, Escherichia coli, Listeria monocytogenes, and Salmonella enterica. This integrated review surveys and interprets our current knowledge of the chemistry, analysis, safety, mechanism of action, and antibiotic activities of cinnamaldehyde in food animal (cattle, lambs, calves, pigs, poultry) diets and in widely consumed liquid (apple, carrot, tomato, and watermelon juices, milk) and solid foods. Solid foods include various fruits (bayberries, blueberries, raspberries, and strawberries), vegetables (carrots, celery, lettuce, spinach, cucumbers, and tomatoes), meats (beef, ham, pork, and frankfurters), poultry (chickens and turkeys), seafood (oysters and shrimp), bread, cheese, eggs, infant formula, and peanut paste. The described findings are not only of fundamental interest but also have practical implications for food safety, nutrition, and animal and human health. The collated information and suggested research needs will hopefully facilitate and guide further studies needed to optimize the use of cinnamaldehyde alone and in combination with other natural antimicrobials and medicinal antibiotics to help prevent and treat food animal and human diseases.

Calorimetric and Spectroscopic Studies of the Effects of the Cell Penetrating Peptide Pep-1 and the Antimicrobial Peptide Combi-2 on Vesicles Mimicking Escherichia coli Membrane

The objective of this study is to measure and compare the effects of the cell penetrating peptide (CPP) Pep-1 and the antimicrobial peptide (AMP) combi-2 on vesicles of membranes mimicking Escherichia coli (E. coli). To characterize the effects of Pep-1 and combi-2 on E. coli membrane vesicles, a combination of five biophysical techniques was employed: fluorescence, infrared, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) techniques. Upon addition of E. coli membranes, tryptophan fluorescence intensity of Pep-1 showed a sudden blue-shift and decreased in a nonconcentration-dependent manner while the intensity of combi-2 decreased in a concentration-dependent manner, most significantly for a very low peptide-to-lipid ratio of 1:40. Complexes of Pep-1 and combi-2 with E. coli membrane mimicking vesicles having shown a significant blue-shift in fluorescence intensity were then prepared and studied in freeze-dried states. IR results indicate that Pep-1 and combi-2 adopt a major 3₁₀-helix structure in the presence of E. coli membrane mimicking vesicles at low peptide concentration. Pep-1 and combi-2 have a similar effect on E. coli membrane mimicking vesicles at low concentration even though combi-2 is in the interfacial region of the bilayer while Pep-1 is located between the interfacial region and the hydrophobic region. Combi-2 at low concentration acts as a CPP. TGA and DSC results reveal that combi-2 has a stabilizing effect on E. coli at any concentration while Pep-1 stabilizes the E. coli membrane only at high concentration. Both peptides show a preferential interaction with one of the anionic lipids leading to clustering in E. coli membrane. SEM images reveal that Pep-1 and combi-2 form superstructures including fibrils in the presence of E. coli membrane mimicking vesicles. Calorimetric and spectroscopic techniques may be used in a complementary way with imaging techniques to gain more insights into peptide-lipid interactions.

Mechanisms of Antimicrobial Action of Cinnamon and Oregano Oils, Cinnamaldehyde, Carvacrol, 2,5-Dihydroxybenzaldehyde, and 2-Hydroxy-5-Methoxybenzaldehyde against Mycobacterium avium subsp. paratuberculosis (Map)

The antimicrobial modes of action of six naturally occurring compounds, cinnamon oil, cinnamaldehyde, oregano oil, carvacrol, 2,5-dihydroxybenzaldehyde, and 2-hydroxy-5-methoxybenzaldehyde, previously found to inhibit the growth of Mycobacterium avium subsp. paratuberculosis (Map) reported to infect food animals and humans and to be present in milk, cheese, and meat, were investigated. The incubation of Map cultures in the presence of all six compounds caused phosphate ions to leak into the extracellular environment in a time- and concentration-dependent manner. Cinnamon oil and cinnamaldehyde decreased the intracellular adenosine triphosphate (ATP) concentration of Map cells, whereas oregano oil and carvacrol caused an initial decrease of intracellular ATP concentration that was restored gradually after incubation at 37 °C for 2 h. Neither 2,5-dihydroxybenzaldehyde nor 2-hydroxy-5-methoxybenzaldehyde had a significant effect on intracellular ATP concentration. None of the compounds tested were found to cause leakage of ATP to the extracellular environment. Monolayer studies involving a Langmuir trough apparatus revealed that all anti-Map compounds, especially the essential oil compounds, altered the molecular packing characteristics of phospholipid molecules of model membranes, causing fluidization. The results of the physicochemical model microbial membrane studies suggest that the destruction of the pathogenic bacteria might be associated with the disruption of the bacterial cell membrane.

Anesthetic Agents of Plant Origin: A Review of Phytochemicals with Anesthetic Activity

The majority of currently used anesthetic agents are derived from or associated with natural products, especially plants, as evidenced by cocaine that was isolated from coca (Erythroxylum coca, Erythroxylaceae) and became a prototype of modern local anesthetics and by thymol and eugenol contained in thyme (Thymus vulgaris, Lamiaceae) and clove (Syzygium aromaticum, Myrtaceae), respectively, both of which are structurally and mechanistically similar to intravenous phenolic anesthetics. This paper reviews different classes of phytochemicals with the anesthetic activity and their characteristic molecular structures that could be lead compounds for anesthetics and anesthesia-related drugs. Phytochemicals in research papers published between 1996 and 2016 were retrieved from the point of view of well-known modes of anesthetic action, that is, the mechanistic interactions with Na⁺ channels, γ-aminobutyric acid type A receptors, N-methyl-d-aspartate receptors and lipid membranes. The searched phytochemicals include terpenoids, alkaloids and flavonoids because they have been frequently reported to possess local anesthetic, general anesthetic, antinociceptive, analgesic or sedative property. Clinical applicability of phytochemicals to local and general anesthesia is discussed by referring to animal in vivo experiments and human pre-clinical trials. This review will give structural suggestions for novel anesthetic agents of plant origin.

Disordering Effects of Digitonin on Phospholipid Monolayers

Digitonin, a steroidal saponin obtained from the foxglove plant (Digitalis purpurea), displays a wide spectrum of biological properties and is often used as a model in mechanistic investigations of the biological activity of saponins. In the present study, Langmuir monolayers of zwitterionic (DPPC, DMPE, POPC, POPE, DSPC, DSPE, and DPPE) and ionic (DPPS and DPPG) phospholipids were employed in order to better understand the effect of digitonin on the lipid organization. For this purpose, a combination of surface pressure relaxation, infrared reflection absorption spectroscopy (IRRAS), and fluorescence microscopy measurements was used. The observed increase in surface pressure (Π) suggests that digitonin can adsorb at the air/water interface, both bare and covered with the uncompressed phospholipid monolayers. However, the detailed analysis of IRRAS and fluorescence microscopy data shows that digitonin interacts with the lipid monolayers in a very selective way, and both the headgroup and the lipid tails affect this interaction. Nevertheless, it should be noted that in no case did digitonin cause any disruptive effects on the monolayers. The DPPE and DPPS monolayers get disordered by penetration with digitonin, despite an increase in surface pressure, leading to an unprecedented LC-LE transition. Interestingly, saponin could be easily squeezed out of these monolayers by mechanical compression.

Membrane fatty acid composition as a determinant of Listeria monocytogenes sensitivity to trans-cinnamaldehyde

trans-Cinnamaldehyde, the major compound of cinnamon essential oil, is a potentially interesting natural antimicrobial food preservative. Although a number of studies have addressed its mode of action, the factors that determine bacterial sensitivity or tolerance to trans-cinnamaldehyde are poorly understood. We report the detailed characterization of a Listeria monocytogenes Scott A trans-cinnamaldehyde hypersensitive mutant defective in IlvE, which catalyzes the reversible transamination of branched-chain amino acids to the corresponding short-chain α-ketoacids. This mutant showed an 8.4 fold extended lag phase during growth in sublethal concentrations (4 mM), and faster inactivation in lethal concentrations of trans-cinnamaldehyde (6 mM). trans-Cinnamaldehyde hypersensitivity could be corrected by genetic complementation with the ilvE gene and supplementation with branched-chain α-ketoacids. Whole-cell fatty acid analyses revealed an almost complete loss of anteiso branched-chain fatty acids (BCFAs), which was compensated by elevated levels of unbranched saturated fatty acids and iso-BCFAs. Sub-inhibitory concentrations of trans-cinnamaldehyde induced membrane fatty acid adaptations predicted to reduce membrane fluidity, possibly as a response to counteract the membrane fluidizing effect of trans-cinnamaldehyde. These results demonstrate the role of IlvE in BCFA production and the role of membrane composition as an important determinant of trans-cinnamaldehyde sensitivity in L. monocytogenes.

Physiological, Biochemical, and Biophysical Characterization of the Lung-Lavaged Spontaneously-Breathing Rabbit as a Model for Respiratory Distress Syndrome

Nasal continuous positive airway pressure (nCPAP) is a widely accepted technique of non-invasive respiratory support in spontaneously-breathing premature infants with respiratory distress syndrome (RDS). Surfactant administration techniques compatible with nCPAP ventilation strategy are actively investigated. Our aim is to set up and validate a respiratory distress animal model that can be managed on nCPAP suitable for surfactant administration techniques studies. Surfactant depletion was induced by bronchoalveolar lavages (BALs) on 18 adult rabbits. Full depletion was assessed by surfactant component analysis on the BALs samples. Animals were randomized into two groups: Control group (nCPAP only) and InSurE group, consisting of a bolus of surfactant (Poractant alfa, 200 mg/kg) followed by nCPAP. Arterial blood gases were monitored until animal sacrifice, 3 hours post treatment. Lung mechanics were evaluated just before and after BALs, at the time of treatment, and at the end of the procedure. Surfactant phospholipids and protein analysis as well as surface tension measurements on sequential BALs confirmed the efficacy of the surfactant depletion procedure. The InSurE group showed a significant improvement of blood oxygenation and lung mechanics. On the contrary, no signs of recovery were appreciated in animals treated with just nCPAP. The surfactant-depleted adult rabbit RDS model proved to be a valuable and efficient preclinical tool for mimicking the clinical scenario of preterm infants affected by mild/moderate RDS who spontaneously breathe and do not require mechanical ventilation. This population is of particular interest as potential target for the non-invasive administration of surfactant.

Influence of Lipid Core Material on Physicochemical Characteristics of an Ursolic Acid-Loaded Nanostructured Lipid Carrier: An Attempt To Enhance Anticancer Activity

The impact of saturation and unsaturation in the fatty acyl hydrocarbon chain on the physicochemical properties of nanostructured lipid carriers (NLCs) was investigated to develop novel delivery systems loaded with an anticancer drug, ursolic acid (UA). Aqueous NLC dispersions were prepared by a high-pressure homogenization-ultrasonication technique with Tween 80 as a stabilizer. Mutual miscibility of the components at the air-water interface was assessed by surface pressure-area measurements, where attractive interactions were recorded between the lipid mixtures and UA, irrespective of the extent of saturation or unsaturation in fatty acyl chains. NLCs were characterized by combined dynamic light scattering, transmission electron microscopy (TEM), atomic force microscopy (AFM), differential scanning calorimetry, drug encapsulation efficiency, drug payload, in vitro drug release, and in vitro cytotoxicity studies. The saturated lipid-based NLCs were larger than unsaturated lipids. TEM and AFM images revealed the spherical and smooth surface morphology of NLCs. The encapsulation efficiency and drug payload were higher for unsaturated lipid blends. In vitro release studies indicate that the nature of the lipid matrix affects both the rate and release pattern. All UA-loaded formulations exhibited superior anticancer activity compared to that of free UA against human leukemic cell line K562 and melanoma cell line B16.

Antibacterial Activity and Membrane-Disruptive Mechanism of 3-p-trans-Coumaroyl-2-hydroxyquinic Acid, a Novel Phenolic Compound from Pine Needles of Cedrus deodara, against Staphylococcus aureus

Recently, we reported that a novel phenolic compound isolated from Cedrus deodara, 3-p-trans-coumaroyl-2-hydroxyquinic acid (CHQA), exhibits a potent antioxidant activity. The present study aimed to evaluate the antibacterial activity of CHQA against eleven food-borne pathogens and to elucidate its mechanism of action against Staphylococcus aureus. The results from minimum inhibitory concentration (MIC) determinations showed that CHQA exhibited moderate inhibitory effects on all of the tested pathogens with MIC values ranging from 2.5-10 mg/mL. Membrane potential measurements and flow cytometric analysis demonstrated that CHQA damaged the cytoplasmic membrane of S. aureus, causing a significant membrane hyperpolarization with a loss of membrane integrity. Moreover, CHQA induced an increase in membrane fluidity and conformational changes in membrane protein of S. aureus, suggesting that CHQA probably acts on the cell membrane by interactions with membrane lipid and protein. Transmission electron microscopic observations further confirmed that CHQA disrupted the cell membrane of S. aureus and caused severe morphological changes, which even led to leakage of intracellular constituents. These findings indicated that CHQA could have the potential to serve as a natural antibacterial agent to control and prevent the growth of pathogens in food and in food-processing environments.