The in-vitro evaluation of antibacterial, antifungal and cytotoxic properties of Marrubium vulgare L. essential oil grown in Tunisia

<p>Abstract</p> <p>Background</p> <p>In order to validate its antiseptic and anticancer properties with respect to traditional uses, we have screened for the first time the antimicrobial activity of aerial parts of <it>M. vulgare </it>L. essential oil against different pathogenic microorganisms and the cytotoxic activity against HeLa cell lines.</p> <p>Methods</p> <p>The agar disk diffusion method was used to study the antibacterial activity of <it>M. vulgare </it>essential oil against 12 bacterial and 4 fungi strains. The disc diameters of zone of inhibition (DD), the minimum inhibitory concentrations (MIC) and the concentration inhibiting 50% (IC₅₀) were investigated to characterize the antimicrobial activities of this essential oil. The <it>in vitro </it>cytotoxicity of <it>M. vulgare </it>essential oil was examined using a modified MTT assay; the viability and the IC₅₀were used to evaluate this test.</p> <p>Results</p> <p>The antimicrobial activity of the essential oil was investigated in order to evaluate its efficacy against the different tested microorganisms. The present results results showed a significant activity against microorganisms especially Gram (+) bacteria with inhibition zones and minimal inhibitory concentration values in the range of 6.6-25.2 mm and 1120-2600 μg/ml, respectively, whereas Gram (-) bacteria exhibited a higher resistance. As far as the antifungal activity, among four strains tested, <it>Botrytis cinerea </it>exhibited the strongest activity with inhibition zones of 12.6 mm. However, <it>Fusarium solani, Penicillium digitatum </it>and <it>Aspergillus niger </it>were less sensitive to <it>M. vulgare </it>essential oil. About the citotoxicity assay, this finding indicate the capability of this essential oil to inhibited the proliferation of HeLa cell lines under some conditions with IC₅₀value of 0.258 μg/ml.</p> <p>Conclusion</p> <p>This investigation showed that the <it>M. vulgare </it>essential oil has a potent antimicrobial activity against some Gram (+) pathogenic bacteria and <it>Botrytis cinerea </it>fungi. The present studies confirm the use of this essential oil as anticancer agent. Further research is required to evaluate the practical values of therapeutic applications.</p

ZrO2-doped ZnO-PDMS nanocomposites as protective coatings for the stone materials

ZnO is a semiconductor that has found wide application in the optics and electronics areas. Moreover, it is widely used in different technological areas due to its beneficial qualities (high chemical stability, non-toxicity, high photo-reactivity, and cheapness). Based on its antibacterial activity, recently it has found also application to prevent bio-deterioration of cultural heritage buildings. As many authors suggested, doped ZnO nano-structures exhibit better antibacterial properties than undoped analogues. In the present work, ZnO nanoparticles doped with ZrO2 have been prepared by a sol-gel method in order to enhance the photocatalytic properties as well as the antibacterial activity of ZnO. Then, ZrO2-ZnO-PDMS nanocomposite (PDMS, polydimethylsiloxane used as the binder) was synthesized by in-situ reaction. The resulting nanocomposite has been investigated as a possible protective material for cultural heritage building substrates. The performances of newly prepared coating were evaluated in three different stones (Lecce stone, Carrara Marble and Brick) and compared with Plain PDMS as a reference coating. </p

Multifunctional and Durable Coatings for Stone Protection Based on Gd-Doped Nanocomposites

The development of nanocomposite materials with multifunctional protective features is an urgent need in many fields. However, few works have studied the durability of these materials. Even though TiO2 nanoparticles have been extensively applied for self-cleaning effect, it displays a weak activity under visible light. Hence, in this study, pure and Gd-doped TiO2 nanoparticles (molar ratios of doping ions/Ti are 0.1 and 1) were synthesised, characterised, and then mixed with polydimethylsiloxane (PDMS), used as a binder, in order to produce a homogenised thin film on a very porous stone substrate. To our knowledge, Gd-doped TiO2/PDMS protective coatings are studied for the first time for application on historic structures. The protective coatings developed in this work are intended to reduce the surface wettability of the stone and protect the historic stones from dye pollution and microorganism colonisation. Moreover, in this study, the durability of the developed nanocomposite was deeply studied to evaluate the stability of the coatings. Results confirmed that samples treated with the lowest concentrations of Gd ions (0.1 mol%) showed acceptable chromatic variations, a good repellent feature, acceptable water vapour permeability, good durability, the highest self-cleaning activity, and good inhibitory behaviour against microbial colonisation

Silver Nanoparticles in the Cultural Heritage Conservation

Our cultural heritage is our invaluable social and environmental resource and concern. Moreover, it is a key global economic driver. However, they are subjected to deterioration process and aging. Particularly, microorganisms are nowadays considered harmful agents of biodeterioration of artistic materials due to the fact that their interactions with the material cause not only an esthetical damage due to their visible growth on the surface, but they may affect the interested materials in different ways and at different degrees via mechanical and biochemical processes leading to the formation of pitting, scaling and, in the worst scenario, to the loss of material by its detachment. To protect our shared tangible cultural heritage from biodeterioration and preserve it for future generations, several methods have been developed. Notably, using nanomaterials, with antimicrobial features, has been considered an interesting and economical method to preserve valuable heritage materials. In this chapter, we will present an overview of the decay mechanisms that participate in the deterioration of tangible artworks, in particular microorganisms’ colonization. Next, current works that have been developed to use silver nanoparticles to protect heritage items from microbial colonization and prevent their deterioration have been detailed

Multifunctional and Durable Coatings for Stone Protection Based on Gd-Doped Nanocomposites

The development of nanocomposite materials with multifunctional protective features is an urgent need in many fields. However, few works have studied the durability of these materials. Even though TiO2 nanoparticles have been extensively applied for self-cleaning effect, it displays a weak activity under visible light. Hence, in this study, pure and Gd-doped TiO2 nanoparticles (molar ratios of doping ions/Ti are 0.1 and 1) were synthesised, characterised, and then mixed with polydimethylsiloxane (PDMS), used as a binder, in order to produce a homogenised thin film on a very porous stone substrate. To our knowledge, Gd-doped TiO2/PDMS protective coatings are studied for the first time for application on historic structures. The protective coatings developed in this work are intended to reduce the surface wettability of the stone and protect the historic stones from dye pollution and microorganism colonisation. Moreover, in this study, the durability of the developed nanocomposite was deeply studied to evaluate the stability of the coatings. Results confirmed that samples treated with the lowest concentrations of Gd ions (0.1 mol%) showed acceptable chromatic variations, a good repellent feature, acceptable water vapour permeability, good durability, the highest self-cleaning activity, and good inhibitory behaviour against microbial colonisation

Development and implementation of a systemic approach to characterize an emerging etiologic agent with high economic impact and of biological control methods : application to the case of the brittle leaf disease of the date palm tree (Phoenix dactylifera L.)

La Maladie de la Feuille Cassante du Palmier dattier (Phoenix dactylifera L.) constitue un cas d'émergence d'une maladie à fort impact économique causée par un agent étiologique inconnu. Notre stratégie a visé à élaborer une approche sans à priori de l'émergence pouvant être transposée à n'importe quelle situation de ce type. En nous appuyant sur des caractérisations successives des compartiments viraux, bactériens et fongiques de tissus sains et malades, nous avons cherché à mettre en évidence des différences de composition spécifiques et de distribution de ces flores sur 2 campagnes de prélèvements réalisées en 2010 et 2012. Alors que la microscopie électronique à transmission nous a permis de visualiser des structures d'origine virale probable au niveau des chloroplastes du parenchyme chlorophyllien, une étude moléculaire de séquençage de gènes ribosomaux nous a permis de corréler l'apparition de ces structures a de profondes modifications qualitative et quantitative de la microflore endophyte. Ainsi il nous est apparu que la symptomologie de la maladie était corrélée à une modification profonde de la distribution spécifique de la microflore endophyte, visible à la fois au niveau du compartiment fongique et bactérien, suggérant la complète disparition de la pression de sélection exercée par le palmier sain sur sa flore et mise en évidence dans les 2 cas, par un shift d'une répartition de type Poisson vers une répartition normale. Dans le compartiment fongique, une claire déplétion des Pleosporaceae, associées à la plante saine pouvait ainsi être liée à une apparition de nouvelles familles (Trichocomaceae et Mycosphaerellaceae). De même, parmi les bactéries, une disparition des Rhizobium et Ensifer sp associés au compartiment racinaire de la plante saine a ainsi pu être mise en évidence, ces espèces pouvant servir ultérieurement d'indicatrices de bonne santé des palmiers. Dans une deuxième partie de notre travail nous avons cherché à utiliser des éléments de la flore endophyte mais également de substances naturelles dans la lutte biologique contre d'autres pathogènes du palmier. Ainsi, un antagonisme a été mis en évidence entre une souche endophyte d'Arthrobacter agilis et un pathogène majeur, Fusarium oxysporum sp AlbedinisThe Brittle Leaf Disease of the Date Palm Tree (Phoenix dactylifera L.) constitutes a case study of an emerging disease of economic impact caused by a yet uncharacterized etiologic agent. Our strategy was to develop an approach that could be indistinctly transposed to any situation of this type. While basing our investigations on the successive characterization of the diversity of viral, bacterial and fungal endophytic compartments of healthy and diseased Palm trees, we aimed at enlightening differences in species composition but also distribution over two sampling campaigns performed in 2010 and 2012. While transmission electronic microscopy allowed us to visualize structures of probable viral origin affecting chloroplasts of the chlorophyllic cell layer, a molecular approach based on ribosomal gene sequencing allowed us to evidence correlations between the occurrence of such structures and deep modifications of the structure of the palm date tree associated endophytic flora suggesting a strong depletion of the ability of the palm to control its associated endophytes. This was evidenced in both fungal and bacterial compartments by a shift from a Poisson like diversity distribution towards a Gaussian distribution in the flora associated to MFC affected palms. In the fungal compartment, Pleosporaceae, that dominated in healthy palms were replaced by an opportunistic flora of Trichocomaceae and Mycosphaerellaceae. Among bacteria, the disappearance of Rhizobium and Ensifer species, typically associated to the root compartment of healthy palms was enlighten, suggesting that these species could indeed be used as biomarkers of healthy plant status. In a second part of this study, we investigated the potential use of cultivable palm endophytes, but also natural compounds for biocontrol applications. In particular, we evidence the antagonistic potential of Arthrobacter agilis, a palm endophyte, against a major palm date disease agent, Fusarium oxysporum sp. Albedinis

Development and stability studies of sunscreen cream formulations containing three photo-protective filters

The present study aimed to formulate and subsequently evaluate sunscreen cream (W/O/W emulsion) containing three photo-protective filters: benzophenone-3, ethylhexyl methoxycinnamate and titanium dioxide at different percentages. Formulations were stored at 8, 25 and 40 °C for four weeks to investigate their stability. Color, centrifugation, liquefaction, phase separation, pH and Sun Protection Factor (SPF) of sunscreen cream formulations were determined. The microbiological stability of the creams was also evaluated and the organoleptic quality was carried out for 28 days. Interestingly, the combination of 7% Benzophenone-3, 7% Ethylhexyl methoxycinnamate and 6% Titanium dioxide preserved physicochemical properties of the product and was efficient against the development of different spoilage microorganisms as well as aerobic plate counts, Pseudomonas aeruginosa, Staphylococcus aureus, and yeast and mold counts. Furthermore, a good stability was observed for all formulations throughout the experimental period. The newly formulated sunscreen cream was proved to exhibit a number of promising properties and attributes that might open new opportunities for the development of more efficient, safe, and cost-effective skin-care, cosmetic, and pharmaceutical products

Durable Polymer Coatings: A Comparative Study of PDMS-Based Nanocomposites as Protective Coatings for Stone Materials

Nowadays, durable protective coatings receive more attention in the field of conservation for several reasons (they are cost effective, time consuming, more resistance, etc.). Hence, this study was focused on producing a multi-functional, durable coating to protect different stone materials, especially, Lecce stone, bricks, and marble. For this purpose, ZrO2-doped-ZnO-PDMS nanocomposites (PDMS, polydimethylsiloxane used as the binder) were synthesized by in situ reaction (doped nanoparticles were inserted into the polymer matrix during the synthesis of PDMS) and the performances of resulting coatings were examined by handling different experimental analyses. In particular, the study aimed to evaluate the durability properties of the coating along with the self-cleaning effect. As a result, the durability of the nanocomposite coating with respect to the well-known PDMS coating was assessed after exposure to two different ageing cycles: solar ageing (300 W, 1000 h) and humid chamber ageing (RH > 80%, T = 22 ± 3 °C, desiccator, 2 years). All the results were in good agreement with each other providing that newly prepared nanocomposite coating can be used as a durable protective coating for different stone materials

Suitability of Gadolinium doped TiO2 nanoparticles to protect heritage building materials from biodeterioration

Heritage buildings possess historical values coming from the attractive architecture and important events taking place around the heritage area. However, they are subjected to degradation process and ageing. Particularly, microorganisms are usually related to harmful biodegradation of artistic materials. Water also is an essential factor of deterioration precisely in porous materials. To protect heritage materials, several methods have been developed. Notably, using nanomaterials to preserve valuable heritage surfaces has been considered as an alternative method. In particular, TiO2 nanoparticles (NPs) have been extensively regarded as one of the most interesting materials. Their interesting features make them a good candidate for photocatalytic application. However, the necessity of using only UV light hinders their practical application. For that reason doping with lanthanide ions, precisely, Gadolinium (Gd) could be an effective method to enhance TiO2 NPs photoactivity. In the present study, pure and Gadolinium doped TiO2 NPs were synthesized by sol-gel method. Prepared NPs were dispersed in a binder at different powder/binder ratios: (0.1, 0.2, 0.5 and 1%w/wTiO2). However, before any application on artefacts, the nanomaterials need to be tested for their biocide efficiency and importantly for being harmless to cultural heritage material. X-ray powder diffractometry (XRPD), UV-Visible and Raman spectroscopies, scanning electron microscopy (SEM), and energydispersive X-ray spectroscopy (EDS) were used to characterize the as-prepared nanopowders. A set of experiments has been performed in order to investigate Gd3+-doped TiO2 nanomaterials as effective photocatalysts, for their photokilling activity against selected Gram positive and Gram negative bacteria and for the chromatic changes induced after their application on Lecce stone surfaces by performing colorimetric measurements

Preparation and characterization of photocatalytic Gd-doped TiO2 nanoparticles for water treatment

In recent years, the photocatalytic process by using TiO2 nanoparticles (NPs) has produced a great interest in wastewater treatment due to its interesting features such as low-cost, environmental compatibility, and especially capacity to eliminate persistent organic compounds as well as microorganisms in water. In the present work, the photocatalytic activity of Gd-doped TiO2 nanopowders, with different doping amount 0.1, 1, and 5 mol% synthesized by the sol-gel method, was studied under UV/Visible irradiation for water treatment application. The Gd-doped TiO2 nanoparticles were investigated for their photocatalytic degradation of methylene blue (MB) dye and antibacterial activities against two bacterial strains namely Stenotrophomonas maltophilia (S. maltophilia) and Micrococcus luteus (M. luteus). MB dye was used as a pollutant model to estimate reactive oxygen species (ROS) generation and to correlate killing action of nanoparticles with the generation of ROS. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Raman spectroscopy were used to characterize the as-synthesized nanomaterials. Photocatalytic, as well as antibacterial tests, showed that doping with an appropriate amount of Gd could reduce the radiative recombination process of photogenerated electron-hole pairs in TiO2 and induce a significant enhancement in photocatalytic and consequently antibacterial activity. The experimental sequence of bactericidal activity and photocatalytic degradation efficiency exhibited by the different gadolinium-doped nanoparticles was the following: 0.1 mol% Gd-doped TiO2 > 1 mol% Gd-doped TiO2 > 5 mol% Gd-doped TiO2 > pure titania