Potential of Carvacrol and Thymol in Reducing Biofilm Formation on Technical Surfaces

Polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), and stainless steel (SS) are commonly used in medicine and food production technologies. During contact with microorganisms on the surface of these materials, a microbial biofilm is formed. The biofilm structure is difficult to remove and promotes the development of pathogenic bacteria. For this reason, the inhibition of biofilm formation in medical and food production environments is very important. For this purpose, five naturally occurring compounds were used for antimicrobial screening tests. The two with the best antimicrobial properties were chosen to inhibit the biofilm formation of Staphylococcus aureus and Pseudomonas aeruginosa. After 3 days of exposure, thymol reduced the amount of biofilm of Pseudomonas aeruginosa within the range of 70–77% and 52–75% for Staphylococcus aureus. Carvacrol inhibited the formation of biofilms by up to 74–88% for Pseudomonas aeruginosa and up to 86–100% for Staphylococcus aureus. Those phenols decreased the enzyme activity of the biofilm by up to 40–100%. After 10 days of exposure to thymol, biofilm formation was reduced by 80–100% for Pseudomonas aeruginosa and by about 79–100% for Staphylococcus aureus. Carvacrol reduced the amount of biofilm by up to 91–100% for Pseudomonas aeruginosa and up to 95–100% for Staphylococcus aureus.     

Anti-Pathogenic Properties of the Combination of a T3SS Inhibitory Halogenated Pyrrolidone with C-30 Furanone

Antimicrobial resistance is one of the current public health challenges to be solved. The World Health Organization (WHO) has urgently called for the development of strategies to expand the increasingly limited antimicrobial arsenal. The development of anti-virulence therapies is a viable option to counteract bacterial infections with the possibility of reducing the generation of resistance. Here we report on the chemical structures of pyrrolidones DEXT 1–4 (previously identified as furan derivatives) and their anti-virulence activity on Pseudomonas aeruginosa strains. DEXT 1–4 were shown to inhibit biofilm formation, swarming motility, and secretion of ExoU and ExoT effector proteins. Also, the anti-pathogenic property of DEXT-3 alone or in combination with furanone C-30 (quorum sensing inhibitor) or MBX-1641 (type III secretion system inhibitor) was analyzed in a model of necrosis induced by P. aeruginosa PA14. All treatments reduced necrosis; however, only the combination of C-30 50 µM with DEXT-3 100 µM showed significant inhibition of bacterial growth in the inoculation area and systemic dispersion. In conclusion, pyrrolidones DEXT 1–4 are chemical structures capable of reducing the pathogenicity of P. aeruginosa and with the potential for the development of anti-virulence combination therapies.     

Development of Antimicrobial Laser-Induced Photodynamic Therapy Based on Ethylcellulose/Chitosan Nanocomposite with 5,10,15,20-Tetrakis(m-Hydroxyphenyl)porphyrin

The development of new antimicrobial strategies that act more efficiently than traditional antibiotics is becoming a necessity to combat multidrug-resistant pathogens. Here we report the efficacy of laser-light-irradiated 5,10,15,20-tetrakis(m-hydroxyphenyl)porphyrin (mTHPP) loaded onto an ethylcellulose (EC)/chitosan (Chs) nanocomposite in eradicating multi-drug resistant Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans. Surface loading of the ethylcelllose/chitosan composite with mTHPP was carried out and the resulting nanocomposite was fully characterized. The results indicate that the prepared nanocomposite incorporates mTHPP inside, and that the composite acquired an overall positive charge. The incorporation of mTHPP into the nanocomposite enhanced the photo- and thermal stability. Different laser wavelengths (458; 476; 488; 515; 635 nm), powers (5–70 mW), and exposure times (15–45 min) were investigated in the antimicrobial photodynamic therapy (aPDT) experiments, with the best inhibition observed using 635 nm with the mTHPP EC/Chs nanocomposite for C. albicans (59 ± 0.21%), P. aeruginosa (71.7 ± 1.72%), and S. aureus (74.2 ± 1.26%) with illumination of only 15 min. Utilization of higher doses (70 mW) for longer periods achieved more eradication of microbial growth.     

Lemon Oils Attenuate the Pathogenicity of Pseudomonas aeruginosa by Quorum Sensing Inhibition

The chemical composition of three Citrus limon oils: lemon essential oil (LEO), lemon terpenes (LT) and lemon essence (LE), and their influence in the virulence factors production and motility (swarming and swimming) of two Pseudomonas aeruginosa strains (ATCC 27853 and a multidrug-resistant HT5) were investigated. The main compound, limonene, was also tested in biological assays. Eighty-four compounds, accounting for a relative peak area of 99.23%, 98.58% and 99.64%, were identified by GC/MS. Limonene (59–60%), γ-terpinene (10–11%) and β-pinene (7–15%) were the main compounds. All lemon oils inhibited specific biofilm production and bacterial metabolic activities into biofilm in a dose-dependent manner (20–65%, in the range of 0.1–4 mg mL⁻¹) of both strains. Besides, all samples inhibited about 50% of the elastase activity at 0.1 mg mL⁻¹. Pyocyanin biosynthesis decreases until 64% (0.1–4 mg mL⁻¹) for both strains. Swarming motility of P. aeruginosa ATCC 27853 was completely inhibited by 2 mg mL⁻¹ of lemon oils. Furthermore, a decrease (29–55%, 0.1–4 mg mL⁻¹) in the synthesis of Quorum sensing (QS) signals was observed. The oils showed higher biological activities than limonene. Hence, their ability to control the biofilm of P. aeruginosa and reduce the production of virulence factors regulated by QS makes lemon oils good candidates to be applied as preservatives in the food processing industry.     

Polymeric Nanovectors Incorporated with Ganciclovir and HSV-tk Encoding Plasmid for Gene-Directed Enzyme Prodrug Therapy

In the area of gene-directed enzyme prodrug therapy (GDEPT), using herpes simplex virus thymidine kinase (HSV-tk) paired with prodrug ganciclovir (GCV) for cancer treatment has been extensively studied. It is a process involved with two steps whereby the gene (HSV-tk) is first delivered to malignant cells. Afterward, non-toxic GCV is administered to that site and activated to cytotoxic ganciclovir triphosphate by HSV-tk enzyme expressed exogenously. In this study, we presented a one-step approach that both gene and prodrug were delivered at the same time by incorporating them with polymeric micellar nanovectors. GCV was employed as an initiator in the ring-opening polymerization of ε-caprolactone (ε-CL) to synthesize hydrophobic GCV-poly(caprolactone) (GCV–PCL), which was furthered grafted with hydrophilic chitosan to obtain amphiphilic polymer (GCV–PCL–chitosan) for the fabrication of self-assembled micellar nanoparticles. The synthesized amphiphilic polymer was characterized using Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. Micellar prodrug nanoparticles were analyzed by dynamic light scattering, zeta potential, critical micelle concentration, and transmission electron microscopy. Polymeric prodrug micelles with optimal features incorporated with HSV-tk encoding plasmids were cultivated with HT29 colorectal cancer cells and anticancer effectiveness was determined. Our results showed that prodrug GCV and HSV-tk cDNA encoded plasmid incorporated in GCV–PCL–chitosan polymeric nanocarriers could be delivered in a one-step manner to HT-29 cells and triggered high cytotoxicity.     

Bioprospecting the Antibiofilm and Antimicrobial Activity of Soil and Insect Gut Bacteria

Antimicrobial resistance is a growing concern in public health and current research shows an important role for bacterial biofilms in recurrent or chronic infections. New strategies, therefore, are necessary to overcome antimicrobial resistance, through the development of new therapies that could alter or inhibit biofilm formation. In this sense, antibiofilm natural products are very promising. In this work, a bioprospection of antimicrobial and antibiofilm extracts from Uruguayan soil bacteria and insect gut bacteria was carried out. Extracts from extracellular broths were tested for their ability to inhibit planktonic cell growth and biofilm formation. Genomic analysis of Bacillus cereus ILBB55 was carried out. All extracts were able to inhibit the growth of, at least, one microorganism and several extracts showed MICs lower than 500 µg mL⁻¹ against microorganisms of clinical relevance (Staphylococcus aureus, Pseudomonas aeruginosa, and Enterobacter cloacae). Among the extracts evaluated for biofilm inhibition only ILBB55, from B. cereus, was able to inhibit, S. aureus (99%) and P. aeruginosa (62%) biofilms. Genomic analysis of this strain showed gene clusters similar to other clusters that code for known antimicrobial compounds. Our study revealed that extracts from soil bacteria and insect gut bacteria, especially from B. cereus ILBB55, could be potential candidates for drug discovery to treat infectious diseases and inhibit S. aureus and P. aeruginosa biofilms.     

Response Surface Optimisation of Polydimethylsiloxane (PDMS) on Borosilicate Glass and Stainless Steel (SS316) to Increase Hydrophobicity

Particle deposition on the surface of a drying chamber is the main drawback in the spray drying process, reducing product recovery and affecting the quality of the product. In view of this, the potential application of chemical surface modification to produce a hydrophobic surface that reduces the powder adhesion (biofouling) on the wall of the drying chamber is investigated in this study. A hydrophobic polydimethylsiloxane (PDMS) solution was used in the vertical dipping method at room temperature to determine the optimum coating parameters on borosilicate glass and stainless steel substrates, which were used to mimic the wall surface of the drying chamber, to achieve highly hydrophobic surfaces. A single-factor experiment was used to define the range of the PDMS concentration and treatment duration using the Response Surface Methodology (RSM). The Central Composite Rotatable Design (CCRD) was used to study the effects of the concentration of the PDMS solution (X₁, %) and the treatment duration (X₂, h) on the contact angle of the substrates (°), which reflected the hydrophobicity of the surface. A three-dimensional response surface was constructed to examine the influence of the PDMS concentration and treatment duration on contact angle readings, which serve as an indicator of the surface’s hydrophobic characteristics. Based on the optimisation study, the PDMS coating for the borosilicate glass achieved an optimum contact angle of 99.33° through the combination of a PDMS concentration of X₁ = 1% (w/v) and treatment time of X₂ = 4.94 h, while the PDMS coating for the stainless steel substrate achieved an optimum contact angle of 98.31° with a PDMS concentration of X₁ = 1% (w/v) and treatment time of X₂ = 1 h. Additionally, the infrared spectra identified several new peaks that appeared on the PDMS-treated surfaces, which represented the presence of Si-O-Si, Si-CH₃, CH₂, and CH₃ functional groups for the substrates coated with PDMS. Furthermore, the surface morphology analysis using the Field Emission Scanning Electron Microscopy (FESEM) showed the presence of significant roughness and a uniform nanostructure on the surface of the PDMS-treated substrates, which indicates the reduction in wettability and the potential effect of unwanted biofouling on the spray drying chamber. The application of PDMS and PTFE on the optimally coated substrates successfully reduced the amount of full cream milk particles that adhered to the surface. The low surface energy of the treated surface (19–27 mJ/m²) and the slightly higher surface tension of the full cream milk (54–59 mJ/m²) resulted in a high contact angle (102–103°) and reduced the adhesion work on the treated substrates (41–46 mJ/m²) as compared to the native substrates.     

Assessment of Anti-Inflammatory and Antimicrobial Potential of Ethanolic Extract of Woodfordia fruticosa Flowers: GC-MS Analysis

Currently, the potential utilization of natural plant-derived extracts for medicinal and therapeutic purposes has increased remarkably. The current study, therefore, aimed to assess the antimicrobial and anti-inflammatory activity of modified solvent evaporation-assisted ethanolic extract of Woodfordia fruticosa flowers. For viable use of the extract, qualitative analysis of phytochemicals and their identification was carried out by gas chromatography–mass spectroscopy. Analysis revealed that phenolic (65.62 ± 0.05 mg/g), flavonoid (62.82 ± 0.07 mg/g), and ascorbic acid (52.46 ± 0.1 mg/g) components were present in high amounts, while β-carotene (62.92 ± 0.02 µg/mg) and lycopene (60.42 ± 0.8 µg/mg) were present in lower amounts. The antimicrobial proficiency of modified solvent-assisted extract was evaluated against four pathogenic bacterial and one fungal strain, namely Staphylococcus aureus (MTCC 3160), Klebsiella pneumoniae (MTCC 3384), Pseudomonas aeruginosa (MTCC 2295), and Salmonella typhimurium (MTCC 1254), and Candida albicans (MTCC 183), respectively. The zone of inhibition was comparable to antibiotics streptomycin and amphotericin were used as a positive control for pathogenic bacterial and fungal strains. The extract showed significantly higher (p < 0.05) anti-inflammatory activity during the albumin denaturation assay (43.56–86.59%) and HRBC membrane stabilization assay (43.62–87.69%). The extract showed significantly (p < 0.05) higher DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging assay and the obtained results are comparable with BHA (butylated hydroxyanisole) and BHT (butylated hydroxytoluene) with percentage inhibitions of 82.46%, 83.34%, and 84.23%, respectively. Therefore, the obtained results concluded that ethanolic extract of Woodfordia fruticosa flowers could be utilized as a magnificent source of phenols used for the manufacturing of value-added food products.     

Analysis of Pathogenic Bacterial and Yeast Biofilms Using the Combination of Synchrotron ATR-FTIR Microspectroscopy and Chemometric Approaches

Biofilms are assemblages of microbial cells, extracellular polymeric substances (EPS), and other components extracted from the environment in which they develop. Within biofilms, the spatial distribution of these components can vary. Here we present a fundamental characterization study to show differences between biofilms formed by Gram-positive methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative Pseudomonas aeruginosa, and the yeast-type Candida albicans using synchrotron macro attenuated total reflectance-Fourier transform infrared (ATR-FTIR) microspectroscopy. We were able to characterise the pathogenic biofilms’ heterogeneous distribution, which is challenging to do using traditional techniques. Multivariate analyses revealed that the polysaccharides area (1200–950 cm⁻¹) accounted for the most significant variance between biofilm samples, and other spectral regions corresponding to amides, lipids, and polysaccharides all contributed to sample variation. In general, this study will advance our understanding of microbial biofilms and serve as a model for future research on how to use synchrotron source ATR-FTIR microspectroscopy to analyse their variations and spatial arrangements.     

Characterization of Food Packaging Films with Blackcurrant Fruit Waste as a Source of Antioxidant and Color Sensing Intelligent Material

Chitosan and pectin films were enriched with blackcurrant pomace powder (10 and 20% (w/w)), as bio-based material, to minimize food production losses and to increase the functional properties of produced films aimed at food coatings and wrappers. Water vapor permeability of active films increased up to 25%, moisture content for 27% in pectin-based ones, but water solubility was not significantly modified. Mechanical properties (tensile strength, elongation at break and Young’s modulus) were mainly decreased due to the residual insoluble particles present in blackcurrant waste. FTIR analysis showed no significant changes between the film samples. The degradation temperatures, determined by DSC, were reduced by 18 °C for chitosan-based samples and of 32 °C lower for the pectin-based samples with blackcurrant powder, indicating a disturbance in polymer stability. The antioxidant activity of active films was increased up to 30-fold. Lightness and redness of dry films significantly changed depending on the polymer type. Significant color changes, especially in chitosan film formulations, were observed after exposure to different pH buffers. This effect is further explored in formulations that were used as color change indicators for intelligent biopackaging.     

Physicochemical,Structural, Thermal and Rheological Properties of Flour and Starch Isolated from Avocado Seeds of Landrace and Hass Cultivars

The objective of this study was to obtain and characterize flours and starches from the avocado seeds of Hass and landrace cultivars. The morphological, physical-chemical, structural, thermal and rheological characteristics were evaluated. The flour yield of the Hass and landrace cultivars was 41.56 to 46.86% (w/w), while for starch, it was 35.47 to 39.57% (w/w) (cv. Hass and landrace, respectively). Scanning electron microscopy (SEM) revealed the presence of oval starch granules and other particles in flour, in contrast to flours, starches showed lower ash, proteins and lipids content. However, the amylose content was higher in starches (42.25–48.2%). Flours showed a higher gelatinization temperature (T_p = 73.17–73.62 °C), and their starches presented greater gelatinization enthalpy (∆H_gel = 11.82–13.43 J/g). All samples showed a B-type diffraction pattern, and the crystallinity was higher in the flours. The rheological analysis (flow curves and viscoelastic tests) evidenced a pseudoplastic (n = 0.28–0.36) behavior in all samples analyzed, but the consistency index (k) was higher in starches. In general, the flours and starches from avocado seeds presented interesting proximal, thermal and functional properties for possible application in food systems, and these findings could contribute to the revaluation of this by-product.     

The Effect of the Liposomal Encapsulated Saffron Extract on the Physicochemical Properties of a Functional Ricotta Cheese

In this study, the encapsulation of saffron extract (SE) was examined at four various concentrations of soy lecithin (0.5%–4% w/v) and constant concentration of SE (0.25% w/v). Particle size and zeta potential of liposomes were in the range of 155.9–208.1 nm and −34.6–43.4 mV, respectively. Encapsulation efficiency was in the range of 50.73%–67.02%, with the stability of nanoliposomes in all treatments being >90%. Encapsulated SE (2% lecithin) was added to ricotta cheese at different concentrations (0%, 0.125%, 1%, and 2% w/v), and physicochemical and textural properties of the cheese were examined. Lecithin concentration significantly (p ≤ 0.05) affected the particle size, zeta potential, stability, and encapsulation efficiency of the manufactured liposomes. In terms of chemical composition and color of the functional cheese, the highest difference was observed between the control cheese and the cheese enriched with 2% liposomal encapsulated SE. Hardness and chewiness increased significantly (p ≤ 0.05) in the cheeses containing encapsulated SE compared to the control cheese. However, there was no significant difference in the case of adhesiveness, cohesiveness, and gumminess among different cheeses. Overall, based on the findings of this research, liposomal encapsulation was an efficient method for the delivery of SE in ricotta cheese as a novel functional food.     

PLA Nanofibers for Microenvironmental-Responsive Quercetin Release in Local Periodontal Treatment

The management of periodontitis remains a vital clinical challenge due to the interplay between the microorganisms of the dental biofilm and the host inflammatory response leading to a degenerative process in the surrounding tissues. Quercetin (QUE), a natural flavonol found in many foods, including apples, onions and tea, has exhibited prolonged and strong antibiofilm and anti-inflammatory effects both in vitro and in vivo. However, its clinical application is limited by its poor stability and water solubility, as well as its low bioavailability. Thus, in the present study, electrospun polylactic acid (PLA) nanofibers loaded with different amounts (5–10% w/w) of QUE were produced to rapidly respond to the acidic microenvironment typical of periodontal pockets during periodontal disease. This strategy demonstrated that PLA-QUE membranes can act as a drug reservoir releasing high QUE concentrations in the presence of oral bacterial infection (pH < 5.5), and thus limiting Pseudomonas aeruginosa PAO1 and Streptococcus mutans biofilm maturation. In addition, released QUE exerts antioxidant and anti-inflammatory effects on P. gingivalis Lipopolysaccharide (LPS)-stimulated human gingival fibroblast (HGFs). The reported results confirmed that PLA-QUE membranes could inhibit subgingival biofilm maturation while reducing interleukin release, thereby limiting host inflammatory response. Overall, this study provided an effective pH-sensitive drug delivery system as a promising strategy for treating periodontitis.     

The Effect of pH and Sodium Caseinate on the Aqueous Solubility,Stability, and Crystallinity of Rutin towards Concentrated Colloidally Stable Particles for the Incorporation into Functional Foods

Poor water solubility and low bioavailability of hydrophobic flavonoids such as rutin remain as substantial challenges to their oral delivery via functional foods. In this study, the effect of pH and the addition of a protein (sodium caseinate; NaCas) on the aqueous solubility and stability of rutin was studied, from which an efficient delivery system for the incorporation of rutin into functional food products was developed. The aqueous solubility, chemical stability, crystallinity, and morphology of rutin (0.1–5% w/v) under various pH (1–11) and protein concentrations (0.2–8% w/v) were studied. To manufacture the concentrated colloidally stable rutin–NaCas particles, rutin was dissolved and deprotonated in a NaCas solution at alkaline pH before its subsequent neutralisation at pH 7. The excess water was removed using ultrafiltration to improve the loading capacity. Rutin showed the highest solubility at pH 11, while the addition of NaCas resulted in the improvement of both solubility and chemical stability. Critically, to achieve particles with colloidal stability, the NaCas:rutin ratio (w/w) had to be greater than 2.5 and 40 respectively for the lowest (0.2% w/v) and highest (4 to 8% w/v) concentrations of NaCas. The rutin–NaCas particles in the concentrated formulations were physically stable, with a size in the range of 185 to 230 nm and zeta potential of −36.8 to −38.1 mV, depending on the NaCas:rutin ratio. Encapsulation efficiency and loading capacity of rutin in different systems were 76% to 83% and 2% to 22%, respectively. The concentrated formulation containing 5% w/v NaCas and 2% w/v rutin was chosen as the most efficient delivery system due to the ideal protein:flavonoid ratio (2.5:1), which resulted in the highest loading capacity (22%). Taken together, the findings show that the delivery system developed in this study can be a promising method for the incorporation of a high concentration of hydrophobic flavonoids such as rutin into functional foods.     

Chemical Profile,Antioxidant Capacity,and Antimicrobial Activity of Essential Oils Extracted from Three Different Varieties (Moldoveanca 4, Vis Magic 10, and Alba 7) of Lavandula angustifolia

Chemical composition, antioxidant capacity, and antimicrobial activity of lavender essential oils (LEOs) extracted from three different varieties of Lavandula angustifolia Mill. (1-Moldoveanca 4, 2-Vis magic 10, and 3-Alba 7) have been determined. These plants previously patented in the Republic of Moldova were cultivated in an organic agriculture system in the northeastern part of Romania and then harvested in 3 consecutive years (2017–2019) to obtain the essential oils. From the inflorescences in the complete flowering stage, the LEOs were extracted by hydrodistillation. Then, their composition was analyzed by gas chromatography coupled with mass spectrometry (GC-MS) and by Fourier Transformed Infrared spectroscopy (FT-IR). The major identified constituents are as follows: linalool (1: 32.19–46.83%; 2: 29.93–30.97%; 3: 31.97–33.77%), linalyl acetate (1: 17.70–35.18%; 2: 27.55–37.13%; 3: 28.03–35.32%), and terpinen-4-ol (1: 3.63–7.70%; 2: 3.06–7.16%; 3: 3.10–6.53%). The antioxidant capacity as determined by ABTS and DPPH assays indicates inhibition, with the highest activity obtained for LEO var. Alba 7 from 2019. The in vitro antimicrobial activities of the LEOs and combinations were investigated as well, by using the disk diffusion method and minimum inhibitory concentration (MIC) against the Gram-positive bacterial strain Staphylococcus aureus (ATCC 6538), Gram-negative Pseudomonas aeruginosa (ATCC 27858), Escherichia coli (ATCC 25922), the yeast Candida albicans (ATCC 10231), and clinical isolates. Our results have shown that LEOs obtained from the three studied varieties of L. angustifolia manifest significant bactericidal effects against tested microorganisms (Staphylococcus aureus and Escherichia coli), and antifungal effects against Candida albicans. The mixture of LEOs (Var. Alba 7) and geranium, respectively, in tea tree EOs, in different ratios, showed a significant enhancement of the antibacterial effect against all the studied strains, except Pseudomonas aeruginosa.     

Chitosan-coated silver nanoparticles promoted antibacterial,antibiofilm, wound-healing of murine macrophages and antiproliferation of human breast cancer MCF 7 cells

In the present study, environmentally benign silver nanoparticles were synthesized using commercially purchased shrimp-shell chitosan as a capping agent. The synthesized chitosan-silver nanoparticles (Ch-AgNPs) were physico-chemically characterized by UV–Vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HR-TEM) along with energy dispersive X-ray analysis (EDX), DLS and Zeta potential analysis. Ch-Ag NPs were crystalline, uniformly dispersed, and spherically shaped, with particle size between 8 and 48 nm. The average size of Ch-AgNPs was 21 nm. In-vitro anti-biofilm activity of Ch-AgNPs was tested against wound infection-causing pathogenic bacteria such as Staphylococcus aureus (Gram-positive) and Pseudomonas aeruginosa (Gram-negative). Ch-AgNPs displayed anti-biofilm activity in a dose-dependent manner. Light and confocal-laser scanning microscopy confirmed the significant inhibition of biofilm growth of S. aureus (85%) and P. aeruginosa (95%) at 100 μg mL⁻¹ of Ch-AgNPs. Moreover, Ch-AgNPs promoted wound healing by increasing the migration of RAW 264.7 murine macrophages cells at 75 and 100 μg mL⁻¹after 24 h. In addition, in vitro cytotoxicity of Ch-AgNPs against MCF 7 (human breast cancer) cells, depicted the greater inhibition of proliferation of cells (64%) at 100 μg mL^−1.     

Development of Chitosan-Based Surfaces to Prevent Single- and Dual-Species Biofilms of Staphylococcus aureus and Pseudomonas aeruginosa

Implantable medical devices (IMDs) are susceptible to microbial adhesion and biofilm formation, which lead to several clinical complications, including the occurrence of implant-associated infections. Polylactic acid (PLA) and its composites are currently used for the construction of IMDs. In addition, chitosan (CS) is a natural polymer that has been widely used in the medical field due to its antimicrobial and antibiofilm properties, which can be dependent on molecular weight (Mw). The present study aims to evaluate the performance of CS-based surfaces of different Mw to inhibit bacterial biofilm formation. For this purpose, CS-based surfaces were produced by dip-coating and the presence of CS and its derivatives onto PLA films, as well surface homogeneity were confirmed by contact angle measurements, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The antimicrobial activity of the functionalized surfaces was evaluated against single- and dual-species biofilms of Staphylococcus aureus and Pseudomonas aeruginosa. Chitosan-based surfaces were able to inhibit the development of single- and dual-species biofilms by reducing the number of total, viable, culturable, and viable but nonculturable cells up to 79%, 90%, 81%, and 96%, respectively, being their activity dependent on chitosan Mw. The effect of CS-based surfaces on the inhibition of biofilm formation was corroborated by biofilm structure analysis using confocal laser scanning microscopy (CLSM), which revealed a decrease in the biovolume and thickness of the biofilm formed on CS-based surfaces compared to PLA. Overall, these results support the potential of low Mw CS for coating polymeric devices such as IMDs where the two bacteria tested are common colonizers and reduce their biofilm formation.     

Chemical Composition and Antimicrobial and Antioxidant Activities of Essential Oil of Sunflower (Helianthus annuus L.) Receptacle

Sunflower (Helianthus annuus L.) contains active ingredients, such as flavonoids, alkaloids and tannins. Nevertheless, few studies have focused on essential oil from the receptacle of sunflower (SEO). In this work, we investigated the chemical composition and antimicrobial and antioxidant activities of SEO. The yield of SEO was about 0.42% (v/w) by hydrodistillation. A total of 68 volatile components of SEO were putatively identified by gas chromatography–mass spectrometry (GC-MS). The main constituents of SEO were α-pinene (26.00%), verbenone (7.40%), terpinolene (1.69%) and α-terpineol (1.27%). The minimum inhibitory concentration (MIC) of SEO against P. aeruginosa and S. aureus was 0.2 mg/mL. The MIC of SEO against S. cerevisiae was 3.2 mg/mL. The MIC of SEO against E. coli and Candida albicans was 6.4 mg/mL. The results showed that SEO had high antibacterial and antifungal activities. Three different analytical assays (DPPH, ABTS and iron ion reducing ability) were used to determine the antioxidant activities. The results showed that SEO had antioxidant activities. To summarize, the results in this study demonstrate the possibility for the development and application of SEO in potential natural preservatives and medicines due to its excellent antimicrobial and antioxidant activities.     

Oregano and Thyme Essential Oils Encapsulated in Chitosan Nanoparticles as Effective Antimicrobial Agents against Foodborne Pathogens

The use of natural compounds with biocidal activity to fight the growth of bacteria responsible for foodborne illness is one of the main research challenges in the food sector. This study reports the preparation and physicochemical characterization of chitosan nanoparticles loaded with Thymus capitatus (Th-CNPs) and Origanum vulgare (Or-CNPs) essential oils. The nanosystems were obtained by ionotropic gelation technique with high encapsulation efficiency (80–83%) and loading capacity (26–27%). Nanoparticles showed a spherical shape, bimodal particle size distribution, and good stability (zeta potential values > 40 mV). The treatment of the nanosuspensions at different temperatures (4 and 40 °C) and storage times (7, 15, 21, and 30 days) did not affect their physicochemical parameters and highlights their reservoir ability for essential oils also under stressful conditions. Both Or-CNPs and Th-CNPs exhibited an enhanced bactericidal activity against foodborne pathogens (S. aureus, E. coli, L. monocytogenes) than pure essential oils. These ecofriendly nanosystems could represent a valid alternative to synthetic preservatives and be of interest for health and food safety.     

Improving Vesicular Integrity and Antioxidant Activity of Novel Mixed Soy Lecithin-Based Liposomes Containing Squalene and Their Stability against UV Light

In order to improve the membrane lipophilicity and the affinity towards the environment of lipid bilayers, squalene (SQ) could be conjugated to phospholipids in the formation of liposomes. The effect of membrane composition and concentrations on the degradation of liposomes prepared via the extrusion method was investigated. Liposomes were prepared using a mixture of SQ, cholesterol (CH) and Tween80 (TW80). Based on the optimal conditions, liposome batches were prepared in the absence and presence of SQ. Their physicochemical and stability behavior were evaluated as a function of liposome constituent. From the optimization study, the liposomal formulation containing 5% (w/w) mixed soy lecithin (ML), 0.5% (w/w) SQ, 0.3% (w/w) CH and 0.75% (w/w) TW80 had optimal physicochemical properties and displayed a unilamellar structure. Liposome prepared using the optimal formulation had a low particle size (158.31 ± 2.96 nm) and acceptable %increase in the particle size (15.09% ± 3.76%) and %trolox equivalent antioxidant capacity (%TEAC) loss (35.69% ± 0.72%) against UV light treatment (280–320 nm) for 6 h. The interesting outcome of this research was the association of naturally occurring substance SQ for size reduction without the extra input of energy or mechanical procedures, and improvement of vesicle stability and antioxidant activity of ML-based liposome. This study also demonstrated that the presence of SQ in the membrane might increase the acyl chain dynamics and decrease the viscosity of the dispersion, thereby limiting long-term stability of the liposome.