Study on carvacrol and cinnamaldehyde polymeric films: mechanical properties, release kinetics and antibacterial and antibiofilm activities

Surface-Charge Tuned Polymeric Nanoemulsions for Carvacrol Delivery in Interkingdom Biofilms

Biofilms, intricate microbial communities entrenched in extracellular polymeric substance (EPS) matrices, pose formidable challenges in infectious disease treatment, especially in the context of interkingdom biofilms prevalent in the oral environment. This study investigates the potential of carvacrol-loaded biodegradable nanoemulsions (NEs) with systematically varied surface charges─cationic guanidinium (GMT-NE) and anionic carboxylate (CMT-NE). Zeta potentials of +25 mV (GMT-NE) and -33 mV (CMT-NE) underscore successful nanoemulsion fabrication (∼250 nm). Fluorescent labeling and dynamic tracking across three dimensions expose GMT-NE's superior diffusion into oral biofilms, yielding a robust antimicrobial effect with 99.99% killing for both streptococcal and Candida species and marked reductions in bacterial cell viability compared to CMT-NE (∼4-log reduction). Oral mucosa tissue cultures affirm the biocompatibility of both NEs with no morphological or structural changes, showcasing their potential for combating intractable biofilm infections in oral environment. This study advances our understanding of NE surface charges and their interactions within interkingdom biofilms, providing insights crucial for addressing complex infections involving bacteria and fungi in the demanding oral context.

Green synthesized silver nanoparticles from Phoenix dactylifera synergistically interact with bioactive extract of Punica granatum against bacterial virulence and biofilm development

The global rise of antibiotic resistance poses a substantial risk to mankind, underscoring the necessity for alternative antimicrobial options. Developing novel drugs has become challenging in matching the pace at which microbial resistance is evolving. Recently, nanotechnology, coupled with natural compounds, has emerged as a promising solution to combat multidrug-resistant bacteria. In the present study, silver nanoparticles were green-synthesized using aqueous extract of Phoenix dactylifera (variety Ajwa) fruits and characterized by UV-vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) coupled with Energy dispersive X-ray analysis (EDX), Transmission electron microscopy (TEM) and Thermogravimetric-differential thermal analysis (TGA-DTA). The in-vitro synergy of green synthesized P. dactylifera silver nanoparticle (PD-AgNPs) with selected antibiotics and bioactive extract of Punica granatum, i.e., ethyl acetate fraction (PGEF), was investigated using checkerboard assays. The most effective synergistic combination was evaluated against the QS-regulated virulence factors production and biofilm of Pseudomonas aeruginosa PAO1 by spectroscopic assays and electron microscopy. In-vivo anti-infective efficacy was examined in Caenorhabditis elegans N2 worms. PD-AgNPs were characterized as spherical in shape with an average diameter of 28.9 nm. FTIR analysis revealed the presence of functional groups responsible for the decrease and stabilization of PD-AgNPs. The signals produced by TGA-DTA analysis indicated the generation of thermally stable and pure crystallite AgNPs. Key phytocompounds detected in bioactive fractions include gulonic acid, dihydrocaffeic acid 3-O-glucuronide, and various fatty acids. The MIC of PD-AgNPs and PGEF ranged from 32 to 128 μg/mL and 250-500 μg/mL, respectively, against test bacterial strains. In-vitro, PD-AgNPs showed additive interaction with selected antibiotics (FICI 0.625-0.75) and synergy with PGEF (FICI 0.25-0.375). This combination inhibited virulence factors by up to 75 % and biofilm formation by 84.87 % in P. aeruginosa PAO1. Infected C. elegans worms with P. aeruginosa PAO1 had a 92.55 % survival rate when treated with PD-AgNPs and PGEF. The combination also reduced the reactive oxygen species (ROS) level in C. elegans N2 compared to the untreated control. Overall, these findings highlight that biosynthesized PD-AgNPs and bioactive P. granatum extract may be used as a potential therapeutic formulation against MDR bacteria.

Multifunctional packaging film with sustained release behavior triggered by pH microenvironment for efficient preservation of pork

To tackle microbial contamination and spoilage during pork storage, transportation, and sales, a novel packaging film with exogenously driven controlled release behavior was designed through the demand-directed preparation of the emulsion of shellac-encapsulated cinnamaldehyde nano-capsules (SNCs) and the ingenious integration of chitosan (CS) film matrix. Among them, the SNCs were synthesized using the solvent exchange method, allowing controlled release of cinnamaldehyde (CA) in response to volatile alkaline substances present in the meat. The electrostatic interaction between SNCs and CS molecules improved the thermal stability, water resistance, tensile strength, and viscosity of the film-forming solution, while the CA in SNCs enhanced UV resistance and antimicrobial properties of the film. Notably, the CS film with SNC-100 loaded (CSNCs-100 film) achieved 99% inhibition against both E. coli and S. aureus, regulated environmental moisture, and prolonged the freshness duration of pork by an impressive six days.

Evaluation of Yield, Chemical Profile, and Antimicrobial Activity of Teucrium polium L. Essential Oil Used in Iranian Folk Medicine

Teucrium polium L. is used to treat many diseases like abdominal pains, indigestion, colds, and reproductive system diseases in Iranian folk medicine. This study was designed to investigate the yield, chemical profile of essential oil, and antibacterial and antifungal activity of this species. The flowering aerial parts of T. polium were collected from the Margh region of Kashan, Iran. The essential oil of the plant was extracted and separated using the Clevenger apparatus and analyzed using gas chromatography-mass spectrometry (GC-MS). The antimicrobial activity of the essential oil against a variety of standard microbial strains was investigated with the Agar well-diffusion method and determination of the lowest growth inhibitory and lethal concentration (MIC and MBC). The results showed that the yield of T. polium essential oil (TPEO) was 0.5778%. Based on the results of GC-MS, 76 compounds (99.3%) were identified in the TPEO, of which α-pinene (9.67%), β-caryophyllene (8.07%), β-pinene (5.04%), nerolidol (4.94%), and oleic acid (4.57%) were the dominant components. The results of antimicrobial tests showed that the TPEO on Staphylococcus aureus created the largest zone of inhibition (~ 14.29 mm). The dominant inhibitory activity of this essential oil was against Gram-negative bacteria Escherichia coli (~ 9.00 mm), which was almost similar to rifampin (~ 11 mm). It seems that the predominance of terpenoid and acidic compounds of the essential oil is one of the possible factors of the anti-bacterial activity of this essential oil. Therefore, the TPEO may be a promising and potential strategy to inhibit some bacterial strains.

Incorporation of cinnamaldehyde, carvacrol, and eugenol into zein films for active food packaging: enhanced mechanical properties, antimicrobial activity, and controlled release

Active packaging with antimicrobial functions to improve the quality and extend the shelf life of food products has gained great interest. Because commercial plastic packaging materials are not biodegradable and cause great environmental problems, plant-derived natural materials have been widely studied for the application of biodegradable packaging materials. Herein, we reported a study of essential oils (EOs)-loaded zein film. Cinnamaldehyde (CIN), carvacrol, and eugenol were added to equip the films with antimicrobial effects, while polyethylene glycol (PEG) and oleic acid (OA) were selected for the improvements of mechanical properties. The results showed that PEG efficiently improves the tensile strength and elongation (%E) of zein films compared to OA, although PEG induced weaker water barrier properties of the films than OA. FTIR spectra confirmed the formation of the hydrogen bonds between zein and PEG/OA. The EO-embedded zein film showed better antimicrobial effects than EO themselves. CIN-embedded films showed the highest antimicrobial effect among the three EOs. The sizes of the inhibition zones against Staphylococcus aureus of PEG-added zein films with 1%, 3%, and 5% CIN were 5.67, 12.67, and 16.67 mm, which were larger than that of pure CIN, with the sizes of 0.00, 3.00, and 4.67 mm, respectively. The developed films demonstrate a gradual release of EOs and show antimicrobial effects up to 96 h, indicating their high potential for the applications as active food packaging.

Antibiofilm Effect of Lavandula multifida Essential Oil: A New Approach for Chronic Infections

Fungal infections are associated with high morbidity and mortality rates, being highly prevalent in patients with underlying health complications such as chronic lung disease, HIV, cancer, and diabetes mellitus. To mitigate these infections, the development of effective antifungals is imperative, with plants standing out as promising sources of bioactive compounds. In the present study, we focus on the antibiofilm potential of Lavandula multifida essential oil (EO) against dermatophyte strains and Candida albicans. The EO was characterized using GC and GC-MS, and its antifungal effect was assessed on both biofilm formation and disruption. Biofilm mass, extracellular matrix, and viability were quantified using crystal violet, safranin, and XTT assays, respectively, and morphological alterations were confirmed using optical and scanning electron microscopy. L. multifida EO showed very high amounts of carvacrol and was very effective in inhibiting and disrupting fungal biofilms. The EO significantly decreased biofilm mass and viability in all tested fungi. In addition, a reduction in dermatophytes' extracellular matrix was observed, particularly during biofilm formation. Morphological alterations were evident in mature biofilms, with a clear decrease in hypha diameter. These promising results support the use of L. multifida EO in the development of effective plant-based antifungal products.

Potential of Essential Oils in the Control of Listeria monocytogenes

Listeria monocytogenes is a foodborne pathogen, the causative agent of listeriosis. Infections typically occur through consumption of foods, such as meats, fisheries, milk, vegetables, and fruits. Today, chemical preservatives are used in foods; however, due to their effects on human health, attention is increasingly turning to natural decontamination practices. One option is the application of essential oils (EOs) with antibacterial features, since EOs are considered by many authorities as being safe. In this review, we aimed to summarize the results of recent research focusing on EOs with antilisterial activity. We review different methods via which the antilisterial effect and the antimicrobial mode of action of EOs or their compounds can be investigated. In the second part of the review, results of those studies from the last 10 years are summarized, in which EOs with antilisterial effects were applied in and on different food matrices. This section only included those studies in which EOs or their pure compounds were tested alone, without combining them with any additional physical or chemical procedure or additive. Tests were performed at different temperatures and, in certain cases, by applying different coating materials. Although certain coatings can enhance the antilisterial effect of an EO, the most effective way is to mix the EO into the food matrix. In conclusion, the application of EOs is justified in the food industry as food preservatives and could help to eliminate this zoonotic bacterium from the food chain.

In Situ Polymerization of Linseed Oil-Based Composite Film: Enhancement of Mechanical and Water Barrier Properties by the Incorporation of Cinnamaldehyde and Organoclay

Linseed oil-based composite films were prepared with cinnamaldehyde (Cin) using a modified clay (organoclay) through in situ polymerization, which is the result of the interaction between Cin and organoclay. The incorporation of organoclay reduces the polymer chain's mobility and, therefore, increases the thermal stability of the composite films. In some experimental conditions, the clay is located both inside and on the surface of the film, thus, affecting the mechanical and thermal properties as well as the surface properties of the composite films. The incorporation of organoclay decreases the water contact angle of the composite film by more than 15%, whatever the amount of cinnamaldehyde. However, the incorporation of cinnamaldehyde has the opposite effect on film surface properties. Indeed, for the water vapor permeability (WVP), the effect of cinnamaldehyde on the film barrier properties is much higher in the presence of organoclay. The incorporation of hydrophobic compounds into the polymer films reduces the water content, which acts as a plasticizer and, therefore, decreases the WVP by more than 17%. Linseed oil has a natural antioxidant activity (~97%) due to the higher content of unsaturated fatty acids, and this activity increased with the amount of organoclay and cinnamaldehyde.

Analysis of the Antimicrobial and Anti-Biofilm Activity of Natural Compounds and Their Analogues against Staphylococcus aureus Isolates

(1) Background: Staphylococcus aureus (S. aureus) is one of the most frequent causes of biofilm-associated infections. With the emergence of antibiotic-resistant, especially methicillin-resistant S. aureus (MRSA), there is an urgent need to discover novel inhibitory compounds against this clinically important pathogen. In this study, we evaluated the antimicrobial and anti-biofilm activity of 11 compounds, including phenyl propenes and phenolic aldehydes, eugenol, ferulic acid, sinapic acid, salicylaldehyde, vanillin, cinnamoyl acid, and aldehydes, against drug-resistant S. aureus isolates. (2) Methods: Thirty-two clinical S. aureus isolates were obtained from Alkhidmat Diagnostic Center and Blood Bank, Karachi, Pakistan, and screened for biofilm-forming potential, and susceptibility/resistance against ciprofloxacin, chloramphenicol, ampicillin, amikacin, cephalothin, clindamycin, streptomycin, and gentamicin using the Kirby-Bauer disk diffusion method. Subsequently, 5 representative clinical isolates were selected and used to test the antimicrobial and anti-biofilm potential of 11 compounds using both qualitative and quantitative assays, followed by qPCR analysis to examine the differences in the expression levels of biofilm-forming genes (ica-A, fnb-B, clf-A and cna) in treated (with natural compounds and their derivatives) and untreated isolates. (3) Results: All isolates were found to be multi-drug resistant and dominant biofilm formers. The individual Minimum Inhibitory Concentration (MIC) of natural compounds and their analogues ranged from 0.75−160 mg/mL. Furthermore, the compounds, Salicylaldehyde (SALI), Vanillin (VAN), α-methyl-trans-cinnamaldehyde (A-MT), and trans-4-nitrocinnamic acid (T4N) exhibited significant (15−92%) biofilm inhibition/reduction percentage capacity at the concentration of 1−10 mg/mL. Gene expression analysis showed that salicylaldehyde, α-methyl-trans-cinnamaldehyde, and α-bromo-trans-cinnamaldehyde resulted in a significant (p < 0.05) downregulation of the expression of ica-A, clf-A, and fnb-A genes compared to the untreated resistant isolate. (4) Conclusions: The natural compounds and their analogues used in this study exhibited significant antimicrobial and anti-biofilm activity against S. aureus. Biofilms persist as the main concern in clinical settings. These compounds may serve as potential candidate drug molecules against biofilm forming S. aureus.

"Built to Last": Plant-based Eco-friendly Durable Antibacterial Coatings

The demand for effective and long-term durable antibacterial surfaces has been ever-growing in the past decades. A wide variety of long-lasting antibacterial surfaces developed from release-killing, active-killing, and anti-fouling strategies have demonstrated the desired effectiveness and durability so far. Most of these successful designs were developed from toxic and fossil-based materials, which failed to comply with the green design criteria. Furthermore, the longevity of these surfaces remained an unaddressed challenge. Herein, we present a disruptive paradigm that emphasizes both eco-friendliness and long-lasting antibacterial properties. A bio-based active-killing essential oil, namely carvacrol, and nonfouling carboxybetaine zwitterionic moieties were combined and incorporated into a highly bio-based polyurethane (BPU). The long-lasting active-killing property for this antibacterial BPU coating was enabled through the extended release of the bounded carvacrol via hydrolysis in an aqueous environment and compared to unbound carvacrol by liquid infusion. Also, the release of carvacrol generates zwitterionic moieties to prevent further bacterial attachment at the release site, resulting in a "kill and defend" synergistic antibacterial function in the BPU. The kinetics of the extended-release property were investigated and compared with unbound carvacrol BPU coatings; unbound carvacrol infused into BPU was quickly exhausted after 2 days of immersion in water, while the extended-release surface exhibited a nearly constant release rate of ∼128 ng cm^-2 h^-1 even after 45 days. The in vitro antibacterial efficiency of the BPUs was quantitatively evaluated using the modified ISO standard for cross-laboratory comparison. As a result, approximately 98.9 and 98.7% of Escherichia coli and Staphylococcus aureus were eliminated from the coating surfaces, and only a negligible variance in the antibacterial efficiency was observed after 5 cycles of test. The feasibility for practical application was also demonstrated by challenging the BPU coatings in everyday settings. This "built-to-last" design theory provided insights for future development of greener antibacterial coatings with long-term performance.

Cinnamomum: The New Therapeutic Agents for Inhibition of Bacterial and Fungal Biofilm-Associated Infection

Due to the potent antibacterial properties of Cinnamomum and its derivatives, particularly cinnamaldehyde, recent studies have used these compounds to inhibit the growth of the most prevalent bacterial and fungal biofilms. By inhibiting flagella protein synthesis and swarming motility, Cinnamomum could suppress bacterial attachment, colonization, and biofilm formation in an early stage. Furthermore, by downregulation of Cyclic di‐guanosine monophosphate (c‐di‐GMP), biofilm-related genes, and quorum sensing, this compound suppresses intercellular adherence and accumulation of bacterial cells in biofilm and inhibits important bacterial virulence factors. In addition, Cinnamomum could lead to preformed biofilm elimination by enhancing membrane permeability and the disruption of membrane integrity. Moreover, this substance suppresses the Candida species adherence to the oral epithelial cells, leading to the cell wall deformities, damage, and leakages of intracellular material that may contribute to the established Candida’s biofilm elimination. Therefore, by inhibiting biofilm maturation and destroying the external structure of biofilm, Cinnamomum could boost antibiotic treatment success in combination therapy. However, Cinnamomum has several disadvantages, such as poor solubility in aqueous solution, instability, and volatility; thus, the use of different drug-delivery systems may resolve these limitations and should be further considered in future investigations. Overall, Cinnamomum could be a promising agent for inhibiting microbial biofilm-associated infection and could be used as a catheter and other medical materials surface coatings to suppress biofilm formation. Nonetheless, further in vitro toxicology analysis and animal experiments are required to confirm the reported molecular antibiofilm effect of Cinnamomum and its derivative components against microbial biofilm.

Natural Additives Improving Polyurethane Antimicrobial Activity

In recent years, there has been a growing interest in using polymers with antibacterial and antifungal properties; therefore, the present review is focused on the effect of natural compounds on the antibacterial and antifungal properties of polyurethane (PUR). This topic is important because materials and objects made with this polymer can be used as antibacterial and antifungal ones in places where hygiene and sterile conditions are particularly required (e.g., in healthcare, construction industries, cosmetology, pharmacology, or food industries) and thus can become another possibility in comparison to commonly used disinfectants, which mostly show high toxicity to the environment and the human health. The review presents the possibilities of using natural extracts as antibacterial, antifungal, and antiviral additives, which, in contrast to the currently used antibiotics, have a much wider effect. Antibiotics fight bacterial infections by killing bacteria (bactericidal effect) or slowing and stopping their growth (bacteriostatic effect) and effect on different kinds of fungi, but they do not fight viruses; therefore, compounds of natural origin can find wide use as biocidal substances. Fungi grow in almost any environment, and they reproduce easily in dirt and wet spaces; thus, the development of antifungal PUR foams is focused on avoiding fungal infections and inhibiting growth. Polymers are susceptible to microorganism adhesion and, consequently, are treated and modified to inhibit fungal and bacterial growth. The ability of micro-organisms to grow on polyurethanes can cause human health problems during the use and storage of polymers, making it necessary to use additives that eliminate bacteria, viruses, and fungi.

Novel Karaya Gum Derivatives Produced by Alkaline Hydrolysis and Periodate Oxidation for Active Packaging with Cinnamaldehyde

This study aims to produce novel derivatives of karaya gum using chemical modification and then apply them for active packaging with cinnamaldehyde as the main active component. Native karaya gum (NKG) was hydrolyzed using sodium hydroxide to yield hydrolyzed karaya gum (HKG), which then was oxidized using sodium periodate to yield hydrolyzed-oxidized karaya gum (HOKG). For comparison, NKG was also directly oxidized using sodium periodate to produce oxidized karaya gum (OKG). FTIR spectra confirmed the removal of acetyl groups after alkaline hydrolysis and the formation of carbonyl groups with subsequent formation of hemiacetal and acetal structures after periodate oxidation. The alkaline hydrolysis and the periodate oxidation resulted in opposite effects on the hydrophilicity of the gum: hydrolysis increased solubility, moisture uptake, and viscosity, while periodate oxidation decreased these properties. We then produced films from corn starch and these gums (5% $w/w$ gum/starch) and properties of the films were studied. Hydrolysis of KG resulted in higher tensile strength, higher transparency but lower puncture strength and antifungal activity against of the films, while periodate oxidation exerted the opposite effects. The incorporation of 5% cinnamaldehyde ( $w/w$ of starch) exerted strong antifungal and antibacterial effects on the films against Colletotrichum gloeosporioides and Escherichia coli, which are useful in active packaging. The active packages based on the novel derivatives of KG can find applications in the agricultural, food, and pharmaceutical industries.

Carvacrol Arrests the Proliferation of Hypopharyngeal Carcinoma Cells by Suppressing Ornithine Decarboxylase and Hyaluronidase Activities

Carvacrol, a monoterpene known for its pharmacological activities, is present in the essential oil of Origanum majorana, Origanum vulgare, Thymus vulgaris, and Lippia graveolens. It is used in food as a flavoring and preservative agent in cosmetics and medicines because of its useful bioactivities in clinical practice. However, carvacrol was not much explored for its anticancer potential. Targeting enzymes involved in carcinogenesis, such as ornithine decarboxylase (ODC), cyclooxygenase-2 (COX-2), lipoxygenase-5 (LOX-5), and hyaluronidase (HYAL) by monoterpenes are amongst the efficient approaches for cancer prevention and treatment. In this study, the efficacy of carvacrol was investigated against deregulated cancer biomarkers/targets in organ-specific human cancer cell lines (FaDu, K562, and A549) utilizing in vitro, in silico, and in vivo approaches. The efficacy of carvacrol was evaluated on human cancer cell lines using neutral red uptake (NRU), sulpho rhodamine B (SRB), and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assays. The mechanistic study was carried out in cell-based test systems. Further, the potency of carvacrol was confirmed by the quantitative real-time PCR analysis and molecular docking studies. The in vivo anti-tumor potential of carvacrol was performed on mice S-180 model, and the toxicity examination was accomplished through in silico approach. Carvacrol significantly impeded the growth of FaDu, K562, and A549 cell lines with IC₅₀ values ranging from 9.61 ± 0.05 to 81.32 ± 11.83 μM. Further, the efficacy of carvacrol was explored against different cancer targets in FaDu, K562, and A549 cell lines. Carvacrol inhibits the ODC, COX-2, LOX-5, and HYAL activities in FaDu cell line and ODC, COX-2, and HYAL activities in K562 cell line. The results were validated by expression analysis revealing the downregulation of the targeted gene with a significant change in the transcript level of ODC and HYAL in FaDu cell line with a fold change of 1.56 and 1.61, respectively. A non-significant effect of carvacrol was observed on the downstream signaling pathway of PI3K and HIF-1α/vascular endothelial growth factor (VEGF) in FaDu cells. The cell cycle, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and Annexin V-fluorescein isothiocyanate (FITC) experiments demonstrate that carvacrol induces apoptosis of FaDu cells. Further, the potency of carvacrol was also evaluated in vivo on mice S-180 tumor model, wherein it inhibits tumor growth (72%) at 75 mg/kg body weight (bw). ADMET studies predicted carvacrol as a safe molecule. Overall, carvacrol delayed the growth of FaDu, K562, and A549 cell lines by targeting enzymes involved in the carcinogenesis process. The existence of one hydroxyl group at the para position of carvacrol could be responsible for the anti-proliferative activity. Thus, carvacrol could be used as a pharmacophore to develop a safe and effective multi-targeted anti-cancer medicament.

Potential of Polyamide Nanofibers With Natamycin, Rosemary Extract, and Green Tea Extract in Active Food Packaging Development: Interactions With Food Pathogens and Assessment of Microbial Risks Elimination

Increasing microbial safety and prolonging the shelf life of products is one of the major challenges in the food industry. Active food packaging made from nanofibrous materials enhanced with antimicrobial substances is considered a promising way. In this study, electrospun polyamide (PA) nanofibrous materials functionalized with 2.0 wt% natamycin (NAT), rosemary extract (RE), and green tea extract (GTE), respectively, were prepared as active packaging and tested for the food pathogens Escherichia coli, Listeria monocytogenes, Salmonella enterica, and Staphylococcus aureus. The PAs exhibited: (i) complete retention of bacterial cells reaching 6.0–6.4 log₁₀removal, (ii) antimicrobial activity with 1.6–3.0 log₁₀suppression, and (iii) antibiofilm activity with 1.7–3.0 log₁₀suppression. The PAs prolonged the shelf life of chicken breast; up to 1.9 log₁₀(CFU/g) suppression of total viable colonies and 2.1 log₁₀(CFU/g) suppression of L. monocytogenes were observed after 7 days of storage at 7°C. A beneficial effect on pH and sensory quality was verified. The results confirm microbiological safety and benefits of PA/NAT, PA/RE, and PA/GTE and their potential in developing functional and ecological packaging.

Layer-by-Layer Assembly of Ag@Ti3C2TX and Chitosan on PLLA Substrate to Enhance Antibacterial and Biocompatibility

Poly L-lactic acid (PLLA) is a non-toxic, biocompatible degradable polymer material with excellent mechanical properties after molding. However, it faces challenges in the use of biomedical materials because of its intolerance to bacteria. Here, we use an easy-to-operate method to prepare a composite multilayer membrane: PLLA membrane was used as substrates to assemble positively charged chitosan and negatively charged Ag@MXene on the surface using the Layer-by-layer (LBL) method. The assembly process was detected by Fluorescein Isothiocyanate (FITC)-labelled chitosan and the thickness of the coating multilayer was also detected as 210.0 ± 12.1 nm for P-M membrane and 460.5 ± 26.5 nm for P-Ag@M membrane. The surface self-assembled multilayers exhibited 91.27% and 96.11% growth inhibition ratio against E. coli and S. aureus strains under 808 nm near-infrared (NIR) laser radiation with a synergistic photothermal antibacterial effect. Furthermore, best biocompatibility of P-M and P-Ag@M membranes compare to PLLA membrane motivated us to further explore its application in biomedical materials.

Mechanisms, Anti-Quorum-Sensing Actions, and Clinical Trials of Medicinal Plant Bioactive Compounds against Bacteria: A Comprehensive Review

Bacterial strains have developed an ability to resist antibiotics via numerous mechanisms. Recently, researchers conducted several studies to identify natural bioactive compounds, particularly secondary metabolites of medicinal plants, such as terpenoids, flavonoids, and phenolic acids, as antibacterial agents. These molecules exert several mechanisms of action at different structural, cellular, and molecular levels, which could make them candidates or lead compounds for developing natural antibiotics. Research findings revealed that these bioactive compounds can inhibit the synthesis of DNA and proteins, block oxidative respiration, increase membrane permeability, and decrease membrane integrity. Furthermore, recent investigations showed that some bacterial strains resist these different mechanisms of antibacterial agents. Researchers demonstrated that this resistance to antibiotics is linked to a microbial cell-to-cell communication system called quorum sensing (QS). Consequently, inhibition of QS or quorum quenching is a promising strategy to not only overcome the resistance problems but also to treat infections. In this respect, various bioactive molecules, including terpenoids, flavonoids, and phenolic acids, exhibit numerous anti-QS mechanisms via the inhibition of auto-inducer releases, sequestration of QS-mediated molecules, and deregulation of QS gene expression. However, clinical applications of these molecules have not been fully covered, which limits their use against infectious diseases. Accordingly, the aim of the present work was to discuss the role of the QS system in bacteria and its involvement in virulence and resistance to antibiotics. In addition, the present review summarizes the most recent and relevant literature pertaining to the anti-quorum sensing of secondary metabolites and its relationship to antibacterial activity.

Combining carvacrol and nisin in biodegradable films for antibacterial packaging applications

In this work, the feasibility of antibacterial biopolymeric films containing carvacrol (CRV) and a nisin commercial formulation (Nis) for potential food packaging applications was investigated. As polymer matrix, a commercial biodegradable polymer formulation of Mater-Bi (MB) was chosen due to its significant food packaging applications. CRV and Nis were chosen due to their well-established antibacterial properties and their potential synergistic effect. MB/CRV, MB/Nis, and MB/CRV/Nis systems were produced by melt mixing and compression molding. The mechanical properties of the films were evaluated by tensile tests. Differential scanning calorimetry was assessed aiming at investigating the effect of the two compounds and their mixture on the thermal properties of MB. The release profile of CRV and Nis from the MB-based films was evaluated in water at 4 °C by UV-Vis measurements and it was fitted with a power-law model. The antibacterial activity of MB-based films was tested in vitro against Listeria monocytogenes, Salmonella enteritidis, Escherichia coli, and Staphylococcus aureus. The combination of CRV and Nis strongly affected the properties of the MB-based films and ensured higher antibacterial activity if compared to MB/CRV and MB/Nis systems.

Active compound identification by screening 33 essential oil monomers against Botryosphaeria dothidea from postharvest kiwifruit and its potential action mode

The antifungal activity of postharvest kiwifruit against the pathogen Botryosphaeria dothidea was evaluated for 33 essential oil monomers. The possible mechanism for the known active compounds were further assessed in this study. The results show all the EO components exhibit inhibitory effects on the pathogen to different degrees except for Farnesol. Carbon chain length and C₂-C₃ double bonds had a great effect on the antifungal activities of aldehydes. Of all of these, carvacrol had the strongest antifungal activity with EC₅₀ of 12.58 μL/L and EC₉₀ of 22.08 μL/L. Carvacrol also exhibits significant inhibitory effects on the pathogen, both in vivo and in vitro. Carvacrol evidently alters the hyphal morphology of B. dothidea and severely damages cell membrane and inhibits the formation of lipid components on the membrane. As cell membrane permeability increases, intracellular homeostasis including ion and biomacromolecules were destroyed by carvacrol. Furthermore, carvacrol appears to significantly inhibit mitochondrial activity and respiration rates, resulting in cell death of B. dothidea. Our results provide evidence that carvacrol could be a very useful compound for controlling postharvest rot soft in kiwifruit.

Flexible mats as promising antimicrobial systems via integration of Thymus capitatus (L.) essential oil into PLA

Aim: To develop electrospun mats loaded with Thymus capitatus (L.) essential oil (ThymEO) and to study their morpho-mechanical and antimicrobial properties. Materials & methods: Poly(lactic acid) (PLA) mats containing ThymEO were prepared by electrospinning. The effect of ThymEO on the morpho-mechanical properties of fibers was assayed by scanning electron microscopy and dynamometer measurements. The antimicrobial activity of ThymEO delivered either in liquid or vapor phase was assessed through killing curves and invert Petri dishes method. The cytotoxicity was also investigated. Results: The mechanical properties were enhanced by integrating ThymEO into PLA. Both liquid and vapors of ThymEO released from mats caused reductions of microbial viable cells. Negligible cytotoxicity was demonstrated. Conclusion: PLA/ThymEO delivery systems could be suitable for treating microbial infections.

Nanostructured Oxide-Based Systems for the pH-Triggered Release of Cinnamaldehyde

Cinnamaldehyde is a natural product with antibacterial, antifungal, and anti-inflammatory properties, poorly stable in environmental conditions. Systems for the controlled release of cinnamaldehyde are of great interest to the food and pharmaceutical industries. Here, a new oxide-based construct for the release of cinnamaldehyde catalyzed by acidic pH was obtained by a facile grafting method based on amino-silane linkers and imine chemistry. The grafting procedure led to a loading of ca. 5 molecules/nm2, determined on oxide powders with CHN and TGA measurements. The covalent grafting of cinnamaldehyde, demonstrated by FTIR analyses, preserved the molecule stability, simplifying storage. Release tests were performed at different pH values (between 5.0 and 7.4). Thanks to imine chemistry, a fast cinnamaldehyde (CIN) release was observed in a pH 5.0 environment. Using 1 mg/mL suspensions, CIN concentrations within the range adopted in the food industry were obtained (12.4 ppm). The grafting procedure was also performed on a porous film based on a photocatalytic oxide, demonstrating the versatility of this method, adaptable to both powders and macroscopic materials. By taking advantage of the photoactivity of the oxide, regeneration of the fouled film was achieved upon UV irradiation for 1 h, opening the door to reusable devices for the controlled release of cinnamaldehyde.

Effect of Dehydrothermal Treatment on the Mechanical Properties and Biocompatibility of Plaster of Paris–CaCO3 Hydrogel Loaded With Cinnamaldehyde for Biomedical Purposes

CaCO3 hydrogel incorporation into Plaster of Paris (POP) formulations decreased the resorption rate of the POP after implantation in the body. Although an inflammatory process is required as part of wound healing, the accumulation and activation of inflammatory cells in the POP–hydrogel CaCO3 implant area needs to be controlled. Therefore, cinnamaldehyde, as an anti-inflammatory agent with a unique α, β-unsaturated aldehyde, was incorporated into the CaCO3 hydrogel. During the incorporation, both the lipophilic and hydrophilic sides of the cinnamaldehyde molecule can influence the physical and mechanical properties of the CaCO3 hydrogel, in which mechanical properties of a tissue engineering scaffold are important to fine tune cellular activity during implantation. On the other hand, as a 3-dimensional polymeric structure, crosslinking is needed for the CaCO3 hydrogel to stabilize and increase its molecular weight for better mechanical strength, and more resistance to heat, wear, and solvent attack. For that purpose, dehydrothermal treatment (DHT) was applied to the crosslink hydrogel system as a favorable crosslinking method to avoid the use of a chemical agent. In this study, 3 groups of hydrogels of CaCO3, namely DHT crosslinked, loaded with cinnamaldehyde, and loaded with cinnamaldehyde followed by DHT crosslinking were developed before being combined with POP in 50 wt%. To evaluate the effect of DHT to the final POP-cinnamaldehyde-loaded CaCO3 hydrogel properties and biocompatibility, scanning electron microscopy, contact angle, surface roughness, hardness, diametral tensile strength, and in vivo biocompatibility studies were conducted. It was observed that cinnamaldehyde with DHT treatment improved the POP–hydrogel CaCO3 properties and had good biocompatibility. Thus, POP-cinnamaldehyde-loaded CaCO3 hydrogel can be a promising bone substitute containing an anti-inflammatory agent.

Natural Plant-Derived Chemical Compounds as Listeria monocytogenes Inhibitors In Vitro and in Food Model Systems

Listeria monocytogenes is a foodborne pathogen, sporadically present in various food product groups. An illness caused by the pathogen, named listeriosis, has high fatality rates. Even though L. monocytogenes is resistant to many environmental factors, e.g., low temperatures, low pH and high salinity, it is susceptible to various natural plant-derived antimicrobials (NPDA), including thymol, carvacrol, eugenol, trans-cinnamaldehyde, carvone S, linalool, citral, (E)-2-hexenal and many others. This review focuses on identifying NPDAs active against L. monocytogenes and their mechanisms of action against the pathogen, as well as on studies that showed antimicrobial action of the compounds against the pathogen in food model systems. Synergistic action of NDPA with other factors, biofilm inhibition and alternative delivery systems (encapsulation and active films) of the compounds tested against L. monocytogenes are also summarized briefly.

Plant-Based Phytochemicals as Possible Alternative to Antibiotics in Combating Bacterial Drug Resistance

The unprecedented use of antibiotics that led to development of resistance affect human health worldwide. Prescription of antibiotics imprudently and irrationally in different diseases progressed with the acquisition and as such development of antibiotic resistant microbes that led to the resurgence of pathogenic strains harboring enhanced armors against existing therapeutics. Compromised the treatment regime of a broad range of antibiotics, rise in resistance has threatened human health and increased the treatment cost of diseases. Diverse on metabolic, genetic and physiological fronts, rapid progression of resistant microbes and the lack of a strategic management plan have led researchers to consider plant-derived substances (PDS) as alternative or in complementing antibiotics against the diseases. Considering the quantitative characteristics of plant constituents that attribute health beneficial effects, analytical procedures for their isolation, characterization and phytochemical testing for elucidating ethnopharmacological effects has being worked out for employment in the treatment of different diseases. With an immense potential to combat bacterial infections, PDSs such as polyphenols, alkaloids and tannins, present a great potential for use, either as antimicrobials or as antibiotic resistance modifiers. The present study focuses on the mechanisms by which PDSs help overcome the surge in resistance, approaches for screening different phytochemicals, methods employed in the identification of bioactive components and their testing and strategies that could be adopted for counteracting the lethal consequences of multidrug resistance.

Design and Characterization of Bioactive Bilayer Films: Release Kinetics of Isopropyl Palmitate

Active packaging incorporating antioxidants and antimicrobials is creating a niche in the market and becoming increasingly important. The main goal of this work was the design of bioactive bilayer films (zein/pullulan) incorporating licorice essential oil. The bilayer films were fully characterized in terms of their chemical, physical, barrier, antioxidant, and antimicrobial properties. Furthermore, the release kinetics of isopropyl palmitate, the major compound of the licorice essential oil, was evaluated by HPLC-DAD (high-performance liquid chromatography coupled to diode-array detector). Scanning Electron Microscopy (SEM) micrographs of cross-sections of the bilayer films clearly show the two layers of the films. Besides presenting the capacity to scavenge free radicals and to inhibit the lipid peroxidation, the developed bilayer films were also able to inhibit the growth of known foodborne pathogens (Enterococcus faecalis and Listeria monocytogenes). The release kinetics profile of isopropyl palmitate from bilayer films incorporating licorice essential oil demonstrated that in 50% ethanol at room temperature, the release was more effective, suggesting that the bilayer films will be more efficient if applied to package semi-fatty food.

Preparation, characterization and antimicrobial activity of polyvinyl alcohol/gum arabic/chitosan composite films incorporated with black pepper essential oil and ginger essential oil

Natural materials have attracted increasing attention in wound dressing and food packaging process, which could overcome the serious environmental issues caused by conventional synthetic materials. Essential oils (EOs) such as black pepper essential oil (BPEO) and ginger essential oil (GEO) have extensively been reported for their nutritional and biomedical properties. In this study, biocomposite films based on polyvinyl alcohol (PVA), gum arabic (GA) and chitosan (CS) incorporated with BPEO and GEO were fabricated by solvent casting method. FTIR, XRD, SEM and DSC were performed with mechanical and antimicrobial properties of PVA/GA/CS films with and without BPEO and GEO. The BPEO-PVA/GA/CS film showed heterogeneous rough surface with cavities containing entrapment of BPEO droplets, whereas, the GEO-PVA/GA/CS film showed heterogeneous rough surface with coarseness due to the incorporation of respective EOs. The BPEO and GEO incorporated PVA/GA/CS films were considerable resistant to breakage and flexible with improved heat stability. The BPEO and GEO incorporated PVA/GA/CS films were significantly inhibited the growth of Bacillus cereus, Staphylococcus aureus, Escherichia coli and Salmonella typhimurium. The obtained results have demonstrated that both BPEO and GEO incorporated PVA/GA/CS films are promising alternatives to wound dressing and food packaging materials.

Red pepper peptide coatings control Staphylococcus epidermidis adhesion and biofilm formation

Medical devices (indwelling) have greatly improved healthcare. Nevertheless, infections related to the use of these apparatuses continue to be a major clinical concern. Biofilms form on surfaces after bacterial adhesion, and they function as bacterial reservoirs and as resistance and tolerance factors against antibiotics and the host immune response. Technological strategies to control biofilms and bacterial adhesion, such as the use of surface coatings, are being explored more frequently, and natural peptides may promote their development. In this study, we purified and identified antibiofilm peptides from Capsicum baccatum (red pepper) using chromatography-tandem mass spectrometry, MALDI-MS, MS/MS and bioinformatics. These peptides strongly controlled biofilm formation by Staphylococcus epidermidis, the most prevalent pathogen in device-related infections, without any antibiotic activity. Furthermore, natural peptide-coated surfaces dislayed effective antiadhesive proprieties and showed no cytotoxic effects against different representative human cell lines. Finally, we determined the lead peptide predicted by Mascot and identified CSP37, which may be useful as a prime structure for the design of new antibiofilm agents. Together, these results shed light on natural Capsicum peptides as a possible antiadhesive coat to prevent medical device colonization.

Fungicides Films of Low-Density Polyethylene (LDPE)/Inclusion Complexes (Carvacrol and Cinnamaldehyde) Against Botrytis Cinerea

Low density polyethylene (LDPE) films were prepared with the incorporation of natural agents (carvacrol and trans-cinnamaldehyde) by the melting process. The co-precipitation method was used successfully to complex the carvacrol or trans-cinnamaldehyde with β-cyclodextrin (β-CD). The active compounds encapsulated in β-CD achieved ca. 90% encapsulation efficiency (E.E.). The inclusion complex studied by scanning electron microscopy (SEM) found particles of different sizes, ca. 4 μm. The active compounds were added directly (1 and 5 wt %) into the polymer matrix, yielding LDPE + carvacrol and LDPE + cinnamaldehyde films. The active compounds encapsulated in β-cyclodextrin (β-CD) were added to LDPE, yielding LDPE + β-CD-carvacrol and LDPE + β-CD-cinnamaldehyde films. The incorporation of carvacrol and trans-cinnamaldehyde, and their corresponding inclusion complexes with β-cyclodextrin, did not affect the thermal properties of LDPE. The microcapsules distributed in all polymer matrices had sizes of 5–20 μm as shown by scanning electron microscopy (SEM). In terms of mechanical properties, the polymers showed a slight decrease of Young’s modulus (12%) and yield stress compared (14%) to neat LDPE. This could be due to the essential oil acting as a plasticizer in the polymer matrix. The LDPE + carvacrol and LDPE + cinnamaldehyde films had the capacity to inhibit fungi by 99% compared to neat LDPE. The effectiveness against fungi of LDPE+β-CD + active agent was slower than by the direct incorporation of the essential oil in the LDPE in the same amount of active agent. The biocidal properties were related to the gradual release of active compound from the polymer. The results confirm the applicability of carvacrol, trans-cinnamaldehyde, and their corresponding inclusion complexes in active packaging, as well as their use in the food delivery industry.

Essential oils of Origanum compactum increase membrane permeability, disturb cell membrane integrity, and suppress quorum-sensing phenotype in bacteria

The aim of this study was to investigate antibacterial activity of Origanum compactum essential oils collected at three phenological stages on Escherichia coli and Bacillus subtilis. The antibacterial activity was evaluated using the agar-well diffusion assay. The MIC and MBC values were determined using the micro-dilution assay. The investigation of the antibacterial action was carried out by the evaluation of the effect of O. compactum essential oils on the antibacterial kinetic growth, the integrity of cell membrane and permeability of the cell membrane. The anti-quorum sensing activity was tested by the inhibition of the biofilm formation. The findings of this study showed that O. compactum essential oil has potent antibacterial activities against E. coli and B. subtilis. The lowest inhibition value against B. subtilis was obtained with O. compactum essential oil at the post-flowering stage (MIC = MBC = 0.0312% (v/v)). The antibacterial mechanisms of O. compactum essential oils are related to the disturbing of the cell membrane integrity and the increasing of the membrane permeability, which leads to the leakage of genetic materials (DNA and RNA). Moreover, O. compactum essential oils inhibited the formation of the biofilms, a phenotype that has been known to be quorum sensing regulated.

Bacterial Inactivation by Using Plastic Materials Activated with Combinations of Natural Antimicrobials

Natural antimicrobials have gained interest as possible inhibitors of biofilm formation. The aim of the present study was to determine the efficacy of antimicrobials derived from essential oils (carvacrol, thymol) plus bacteriocin AS-48 immobilized on two plastic supports (low density polyethylene and polyethylene–polyamide films) on bacterial inactivation. The polyethylene–polyamide vacuum-packaging plastic film activated with a combination of thymol plus enterocin AS-48 was the most effective in reducing the concentrations of viable planktonic and sessile cells for Listeria innocua, Lactobacillus fructivorans, Bacillus coagulans, and Bacillus licheniformis. Results from the study highlight the potential of polyethylene–polyamide film activated with thymol plus enterocin AS-48 for reducing the viable cell concentrations of spoilage Gram-positive bacteria and Listeria in both planktonic and sessile states.