Antibacterial activity of textiles for wound treatment

Major advances in the development and use of antimicrobial textiles to control bacterial proliferation on wound beds continue. However, wound dressings are, in general, not included in standardized regimens for measuring and monitoring their antimicrobial effectiveness. This work adapts these methods to assess the antibacterial activity of textiles designed for wound healing purposes. Environmental conditions representative of those present at the wound site (i.e., moisture levels, infection, and available nutrients) were evaluated. This work shows that moisture levels were the environmental factor that had the greatest influence on the antimicrobial agent activities tested. These results suggest that it is possible to use the more representative environmental conditions present on the wound bed for in vitro screening of textile antimicrobial activity.

Nanotechnological approaches using curcumin and Withania somnifera: neuroprotection and antimicrobial activities

Tese de Doutoramento em Biologia de Plantas

Evaluation of antibacterial activity of caffeic acid encapsulated by -cyclodextrins

Context: Caffeic acid is described as antibacterial, but this bioactive molecule has some issues regarding solubility and stability to environmental stress. Thus, encapsulation devices are required. Objective: The aim of this work was to study the effect of the caffeic acid encapsulation by cyclodextrins on its antibacterial activity. Materials and methods: The interactions between the caffeic acid and three cyclodextrins (-cyclodextrin (CD), 2-hydroxypropyl--cyclodextrin (HPCD) and methyl--cyclodextrin were study. Results and discussion: The formation of an aqueous soluble inclusion complex was confirmed for CD and HPCD with a 1:1 stoichiometry. The CD/caffeic acid complex showed higher stability than HPCD/caffeic acid. Caffeic acid antibacterial activity was similar at pH 3 and pH 5 against the three bacteria (K. pneumoniae, S. epidermidis and S. aureus). Conclusions: The antibacterial activity of the inclusion complexes was described here for the first time and it was shown that the caffeic acid activity was remarkably enhanced by the cyclodextrins encapsulation.

Antibacterial properties of fibrous stents coated with silver oxide nanocoatings

Stents are rigid and perforated tubular structures, which are inserted into blood vessels in order to prevent or inhibit the constriction of blood flow, restoring the normal blood flow, when blood vessels are clogged, being used in 70% of angioplasties. These medical devices assume great importance in the treatment of cardiovascular diseases (CVD) which are the leading cause of death worldwide. In the European Union CVD account for 40% of deaths and assume an estimated annual cost of 196 billion euros[1]. Stents must possess certain requirements, in order to, adequately, perform its function, such as biocompatibility (so that its use does not c ause damage on the health of its user), mechanical strength, radiopacity (so that it is easy to view), longitudinal flexibility, ease of handling, corrosion resistance and having high strength and high radial expansion ability to recover. Stents can be made of different materials, but metals, particularly stainless steel, are the most common. However, metallic stents present several dRawbacks such as corrosion and restenosis, leading to health complications for the patient, or even death. In order to minimize these disadvantages, new materials, like fibrous materials, have been used [2]. Monofilaments present high potential for stents development because, in addition to its biocompatibility, these materials allow the application of various surface treatments, such as antibacterial coatings. Furthermore, monofilament exhibit excellent mechanical properties, like greater stiffness and good results when subjected to compression, tensile and bending forces, since these forces will be directly supported by the monofilament [3]. To minimize the reaction of the human body and Limit the adhesion of microorganisms to the stent surface, some coatings have been developed, including the use of novel metals with antimicrobial properties, like silver. The main objective of this study was the development of fibrous stents, incorporation of silver oxide nanocoating. For the development of the stent, polyester monofilaments with 0.27mm of diameter were used in braiding technology, with a mandrel diameter of 6mm and a braiding angle of 35⁰. The mechanical behaviour of the stent were evaluated by mechanical testing under longitudinal and radial compression, bending. The results of compressive strength tests are according with value from literature: 1.13 to 2.9 N for radial compression and 0. 16-5.28N to longitudinal compression. From literature is also possible to verify that stents must present 75% of unchanged diameter during the bending test and must possess a porosity between 70% and 80% [4]. The produced polyester stent presents values of 1.29N for radial compression, 0.23N for longitudinal compression, 80% of porosity and 85.5% of unchanged diameter, during bending tests. For the antibacterial functionalization, silver oxide nanocoatings were prepared, through reactive magnetron g, with an Ag target in an Ar +O2 atmosphere. In order to evaluate the nanostructure and morphology of the coatings, d ifferent technique s like X-ray diffraction (XRD), scanning electron microscopy (SEM) and and X- ray photoelectron spectroscopy (XPS were used. From the analyses of XRD it is possible to verify that the peaks corresponds to planes of Ag2 O and MATERIAIS 2015 Porto, 21-23 June, 2015 characterize a cubic phase. The presence of Ag2 O is corroborated by XPS spectrum, where it is possible to observe silver, not only, in oxide state, but a lso in mettalic state, and it is possible to verify the presence of silver clusters, confirmed by SEM analysis. Films’ roughness and topography, parameters influencing the wettability of the surface and microorganism adhesion, were measured by Atomic Force Microscopy (AFM), and it was observed that the roughness is very low (under 10 nm). Coatings’ hydrophobicity and surface tension parameters were determined by contact angle measurement, and it was verified the hydrophobic behavior of the coatings. For antibacterial tests were used Staphylococcus epidermidis strain (IE186) and Staphylococcus aureus(ATCC 6538), and halo inhibition zone tests were realized. Ag+release rates were studied by means of inductively coupled plasma mass spectrometry (ICP -MS). The obtained results suggest that silver oxide coatings do not modify significantly surface properties of the substrate, like hydrophobicity and roughness, and present antimicrobial properties for both bacteria used.

Electrochemical vs antibacterial characterization of ZrCN-Ag coatings

Nowadays, antibacterial properties are becoming a viable feature to be introduced in biomaterials due to the possibility of modifying the materials' surface used in medical devices in a micro/nano metric scale. As a result, it is mandatory to understand the mechanisms of the antimicrobial agents currently used and their possible failures. In this work, the antibacterial activity of ZrCNAg films is studied, taking into consideration the ability of silver nanoparticles to be dissolved when embedded into a ceramic matrix. The study focuses on the silver release evaluated by glow discharge optical emission spectroscopy and the effect of the fluid composition on this release. The results revealed a very low silver release of the films, leading to non-antibacterial activity of such materials. The silver release was found to be dependent on the electrolyte composition. NaCl (8.9 g L? 1) showed the lowest spontaneously silver ionization, while introducing the sulfates in Hanks' balanced salt solution (HBSS) such ionization is increased; finally, the proteins incorporated to the (HBSS) showed a reduction of the silver release, which also explains the low ionization in the culture medium (tryptic soy broth) that contains high quantities of proteins.

Prediction of drug targets in human pathogens

The identification of new and druggable targets in bacteria is a critical endeavour in pharmaceutical research of novel antibiotics to fight infectious agents. The rapid emergence of resistant bacteria makes today's antibiotics more and more ineffective, consequently increasing the need for new pharmacological targets and novel classes of antibacterial drugs. A new model that combines the singular value decomposition technique with biological filters comprised of a set of protein properties associated with bacterial drug targets and similarity to protein-coding essential genes of E. coli has been developed to predict potential drug targets in the Enterobacteriaceae family [1]. This model identified 99 potential target proteins amongst the studied bacterial family, exhibiting eight different functions that suggest that the disruption of the activities of these proteins is critical for cells. Out of these candidates, one was selected for target confirmation. To find target modulators, receptor-based pharmacophore hypotheses were built and used in the screening of a virtual library of compounds. Postscreening filters were based on physicochemical and topological similarity to known Gram-negative antibiotics and applied to the retrieved compounds. Screening hits passing all filters were docked into the proteins catalytic groove and 15 of the most promising compounds were purchased from their chemical vendors to be experimentally tested in vitro. To the best of our knowledge, this is the first attempt to rationalize the search of compounds to probe the relevance of this candidate as a new pharmacological target.

Impact of an educational hands-on project on the antimicrobial, antitumor and anti-inflammatory properties of plants on Portuguese students' awareness, knowledge, and competences

Promoting environmental and health education is crucial to allow students to make conscious decisions based on scientific criteria. The study is based on the outcomes of an Educational Project implemented with Portuguese students and consisted of several activities, exploring pre-existent Scientific Gardens at the School, aiming to investigate the antibacterial, antitumor and anti-inflammatory properties of plant extracts, with posterior incorporation in soaps and creams. A logo and a webpage were also created. The effectiveness of the project was assessed via the application of a questionnaire (pre- and post-test) and observations of the participants in terms of engagement and interaction with all individuals involved in the project. This project increased the knowledge about autochthonous plants and the potential medical properties of the corresponding plant extracts and increased the awareness about the correct design of scientific experiments and the importance of the use of experimental models of disease. The students regarded their experiences as exciting and valuable and believed that the project helped to improve their understanding and increase their interest in these subjects and in science in general. This study emphasizes the importance of raising students’ awareness on the valorization of autochthonous plants and exploitation of their medicinal properties.

Chemical features of Ganoderma polysaccharides with antioxidant, antitumor and antimicrobial activities

Review aricle

PEGylated ofloxacin nanoparticles render strong antibacterial activity against many clinically important human pathogens.

The rise of bacterial resistance against important drugs threatens their clinical utility. Fluoroquinones, one of the most important classes of contemporary antibiotics has also reported to suffer bacterial resistance. Since the general mechanism of bacterial resistance against fluoroquinone antibiotics (e.g. ofloxacin) consists of target mutations resulting in reduced membrane permeability and increased efflux by the bacteria, strategies that could increase bacterial uptake and reduce efflux of the drug would provide effective treatment. In the present study, we have compared the efficiencies of ofloxacin delivered in the form of free drug (OFX) and as nanoparticles on bacterial uptake and antibacterial activity. Although both poly(lactic-co-glycolic acid) (OFX-PLGA) and methoxy poly(ethylene glycol)-b-poly(lactic-co-glycolic acid) (OFX-mPEG-PLGA) nanoformulations presented improved bacterial uptake and antibacterial activity against all the tested human bacterial pathogens, namely, Escherichia coli, Proteus vulgaris, Salmonella typhimurium, Pseudomonas aeruginosa, Klebsiella pneumoniae and Staphylococcus aureus, OFX-mPEG-PLGA showed significantly higher bacterial uptake and antibacterial activity compared to OFX-PLGA. We have also found that mPEG-PLGA nanoencapsulation could significantly inhibit Bacillus subtilis resistance development against OFX.

Propolis: A complex natural product with a plethora of biological activities that can be explored for drug development

The health industry has always used natural products as a rich, promising, and alternative source of drugs that are used in the health system. Propolis, a natural resinous product known for centuries, is a complex product obtained by honey bees from substances collected from parts of different plants, buds, and exudates in different geographic areas. Propolis has been attracting scientific attention since it has many biological and pharmacological properties, which are related to its chemical composition. Several in vitro and in vivo studies have been performed to characterize and understand the diverse bioactivities of propolis and its isolated compounds, as well as to evaluate and validate its potential. Yet, there is a lack of information concerning clinical effectiveness. The goal of this review is to discuss the potential of propolis for the development of new drugs by presenting published data concerning the chemical composition and the biological properties of this natural compound from different geographic origins.

Contributos para a elucidação do modo de ação de própolis português: o caso do própolis do Pereiro

Dissertação de mestrado em Genética Molecular

Antibacterial Ag/a-C nanocomposite coatings: The influence of nano-galvanic a-C and Ag couples on Ag ionization rates

Biofilm formation has been pointed as a major concern in different industrial applications, namely on biomedical implants and surgical instruments, which has prompted the development of new strategies for production of efficient antimicrobial surfaces. In this work, nano âgalvanic couples were created to enhance the antibacterial properties of silver, by embedding it into amorphous carbon (a-C) matrix. The developed Ag/a-C nanocomposite coatings, deposited by magnetron sputtering, revealed an outstanding antibacterial activity against S.epidermidis, promoting a total reduction in biofilm formation with no bacteria counts in all dilution. The open circuit potential (OCP) tests in 0.9% NaCl confirmed that a-C shows a positive \OCP\ value, in contrast to Ag coating, thus enhancing the ionization of biocidal Ag+ due to the nano-galvanic couple activation. This result was confirmed by the inductively coupled plasma-optical emission spectroscopy (ICP-OES), which revealed a higher Ag ionization rate in the nanocomposite coating in comparison with the Ag coating. The surface of Ag/a-C and Ag coatings immersed in 0.9% NaCl were monitored by scanning electron microscopy (SEM) over a period of 24 hours, being found that the Ag ionization determined by ICP-OES was accompanied by an Ag nanoparticles coalescence and agglomeration in Ag/a-C coating.

Anti-inflammatory and antinociceptive activities of Bauhinia monandra leaf lectin

A galactose-specific lectin from Bauhinia monandra leaves (BmoLL) have been purified through ammonium sulphate fractionation followed by guar gel affinity chromatography column. This study aimed to evaluate the potential anti-inflammatory and antinociceptive activity of pure BmoLL in mice. Anti-inflammatory activity was evaluated by 1% carrageenan-induced inflammation in mice treated with BmoLL. Acetic acid-induced abdominal writhing and hot plate methods evaluated antinociceptive activity. BmoLL significantly inhibited the carrageenan-induced paw edema by 47% (30 mg/kg) and 60.5% (60 mg/kg); acetylsalicylic acid (ASA, 100 mg/kg) showed inhibition of 70.5%, in comparison to controls. Leukocyte migration, an immune response to the inflammation process, was significantly reduced in presence of BmoLL; in mice treated with \ASA\ the decrease in leukocyte migration was similar to 15 mg/kg of the lectin. BmoLL at doses of 15, 30 and 60 mg/kg significantly reduced the number of animal contortions by 43.1, 50.1 and 71.3%, respectively.BmoLL leukocyte migration was significantly reduced; in mice treated with \ASA\ the decrease in leukocyte migration was similar to 15 mg/kg of the lectin. BmoLL at doses of 15, 30 and 60 mg/kg significantly reduced the number of animal contortions by 43.1, 50.1 and 71.3%, respectively. The lectin (30 and 60 mg/kg) showed a significant effect in the hot plate assay. BmoLL anti-inflammatory and antinociceptive effects were dose-dependent. The search for new and natural compounds, with minimal side effects, to control pain and inflammation, is constantly increasing. BmoLL has great potential as a natural anti-inflamatory product that can be explored for pharmacological purposes.

Laccase immobilization on bacterial nanocellulose membranes: antimicrobial, kinetic and stability properties

This work studied the physical immobilization of a commercial laccase on bacterial nanocellulose (BNC) aiming to identify the laccase antibacterial properties suitable for wound dressings. Physico-chemical analysis demonstrates that the BNC structure is manly formed by pure crystalline I cellulose. The pH optimum and activation energy of free laccase depends on the substrate employed corresponding to pH 6, 7, 3 and 57, 22, 48 kJ mol1 for 2,6-dimethylphenol (DMP), catechol and 2,2 -azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), respectively. The Michaelis-Menten constant (Km) value for the immobilized laccase (0.77 mM) was found to be almost double of that of the free enzyme (0.42 mM). However, the specific activities of immobilized and free laccase are similar suggesting that the cage-like structure of BNC allows entrapped laccase to maintain some flexibility and favour substrate accessibility. The results clearly show the antimicrobial effect of laccase in Gram-positive (92%) and Gram-negative (26%) bacteria and cytotoxicity acceptable for wound dressing applications.