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Projeto de investigação
AntiBiofilm features of Glycolipid-functionalized Silicone Catheters towards Healthcare-associated infections prevention
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Bonding antimicrobial rhamnolipids onto medical grade PDMS
Publication . Dardouri, Maïssa; Aljnadi, Israa M.; Deuermeier, Jonas; Santos, Catarina; Costa, Fabiola; Martin, Victor; Fernandes, Maria H.; Gonçalves, Lídia; Bettencourt, Ana; Gomes, Pedro Sousa; Ribeiro, Isabel A. C.; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; DCM - Departamento de Ciência dos Materiais; Elsevier Science B.V., Amsterdam.
In clinic there is a demand to solve the drawback of medical devices multispecies related infections. Consequently, different biomaterial surfaces, such as vascular catheters, urgently need improvement regarding their antifouling/antimicrobial properties. In this work, we covalently functionalized medical grade polydimethylsiloxane (PDMS) with antimicrobial rhamnolipids to investigate the biomaterial surface activity towards mono and dual species biofilms. Preparation of surfaces with “piranha” oxidation, followed by APTES bonding and carbodiimide reaction with rhamnolipids effectively bonded these compounds to PDMS surface as confirmed by FTIR-ATR and XPS analysis. Generated surfaces were active towards S. aureus biofilm formation showing a 4.2 log reduction while with S. epidermidis and C. albicans biofilms a reduction of 1.2 and 1.0 log reduction, respectively, was observed. Regarding dual-species testing the higher biofilm log reduction observed was 1.9. Additionally, biocompatibility was assessed by cytocompatibility towards human fibroblastic cells, low platelet activation and absence of vascular irritation. Our work not only sheds light on using covalently bonded rhamnolipids towards dual species biofilms but also highlights the biocompatibility of the obtained PDMS surfaces.
Drug Delivery from PCL/Chitosan Multilayer Coatings for Metallic Implants
Publication . Soares, I.; Faria, Jaime Moreira Machado; Marques, A. C.; Ribeiro, Isabel A. C.; Baleizão, Carlos; Bettencourt, Ana F.; Ferreira, Isabel; Baptista, Ana Catarina; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); ACS - American Chemical Society
Implant-related infections, mainly caused by Staphylococcus aureus, are a major health concern. Treatment is challenging due to multi-resistant strains and the ability of S. aureus to adhere and form biofilms on bone and implant surfaces. The present work involved the preparation and evaluation of a novel dual polymeric film coating on stainless steel. Chitosan and polycaprolactone (PCL) multilayers, loaded with poly(methyl methacrylate) (PMMA) microspheres encapsulating vancomycin or daptomycin, produced by the dip-coating technique, allowed local antibiotic-controlled delivery for the treatment of implant-related infections. Enhanced adhesion of the film to the metal substrate surface was achieved by mechanical abrasion of its surface. Studies have shown that for both drugs the release occurs by diffusion, but the release profile depends on the type of drug (daptomycin or vancomycin), the pH of the solution, and whether the drug is freestanding (directly incorporated into the films) or encapsulated in PMMA microspheres. Daptomycin freestanding films reached 90% release after 1 day at pH 7.4 and 4 days at pH 5.5. In comparison, films with daptomycin encapsulated microspheres reached 90% release after 2 h at pH 5.5 and 2 days at pH 7.4. Vancomycin encapsulated and freestanding films showed a similar behavior reaching 90% release after 20 h of release at pH 5.5 and 2 and 3 days, respectively, at pH 7.4. Furthermore, daptomycin-loaded films showed activity (assessed by agar diffusion assays) against sensitive (ATCC 25923) and clinically isolated (MRSA) S. aureus strains.
Antimicrobial Glycolipids: Evaluation of their Antimicrobial Activity, Antibiofilm Activity and Mechanisms of Action
Publication . Silva, Luna França Ferreira Pampim; Ribeiro, Isabel; Gonçalves, Lídia
Biofilm formation by pathogenic agents on medical devices is a current issue and the available treatment seems ineffective in fighting these infections, therefore new effective molecules are in high demand. Biosurfactants are new promising compounds, that due to their structure can interact with cellular membrane of microorganisms, interfering with the microbial adhesion in the surface of medical devices to prevent these infections.
The aim of this thesis was to evaluate the antimicrobial and antibiofilm activities and antimicrobial mechanism of biosynthesized mixtures of two glycolipids (i.e. rhamnolipids and sophorolipids). These two were immobilized in the surface of silicone by two methods, either by adsorption or covalent bond by plasma activation of the surface, to prevent microbial adhesion.
Initially, antimicrobial activity was evaluated against different planktonic bacteria and S. aureus ATCC 25923, S. aureus ATCC 6538, clinic MRSA and S. epidermidis ATCC 28319 were the most vulnerable to the studied glycolipids mixtures.
The mechanism of action of both glycolipids including membrane integrity (by propidium iodide uptake) and cellular viability (by resazurin reduction), cells’ surface hydrophobicity and cells’ surface charge modifications were studied. Rhamnolipids were the most active on disturbing membrane integrity, while sophorolipids were the most active on disturbing cellular viability. Both glycolipids increased cell surface hydrophobicity more effectively against S. aureus ATCC 25923, S. aureus ATCC 6538, MRSA and P. aeruginosa ATCC 15442, nevertheless rhamnolipids were more active. Furthermore, both compounds caused a decrease in cell surface charge, however only in a significant way against S. aureus ATCC 25923.
Rhamnolipids adsorbed on the surface of silicone caused a decrease of the hydrophobicity of the material. Furthermore, using crystal violet assay and counting of colony forming units’ methods, it was verified that both glycolipids previously adsorbed on silicone caused a reduction in biofilm formation of sessile bacteria, most effectively against S. aureus ATCC 25923, S. aureus ATCC 6538 and MRSA. However, sophorolipids showed higher activity.
Lastly, plasma treatment on silicone specimens functionalized with rhamnolipids provided good results, showing that this can be a good strategy to create a permanent functionalization to these surfaces.
In conclusion, both glycolipids seem an optimistic approach in preventing biofilm formation on the surface of medical grade silicone, decreasing the risk for the development of these infections.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
3599-PPCDT
Número da atribuição
PTDC/BTM-SAL/29335/2017