Silver colloidal nanoparticles : effect on matrix composition and structure of Candida albicans and Candida glabrata biofilms

Aim : The aim of this study was to assess the effect of different silver nanoparticles (SN) concentrations on the matrix composition and structure of Candida albicans and Candida glabrata biofilms. Methods and Results : Candida biofilms were developed in 6-well microtiter plates during 48 h. After, these biofilms were exposed to 13·5 or 54 μg SN ml−1 for 24 h. Then, extracellular matrices were extracted from biofilms and analysed chemically in terms of proteins, carbohydrates and DNA. To investigate the biofilm structure, scanning electron microscopy (SEM) and epifluorescence microscopy were used. SN interfered with the matrix composition of Candida biofilms tested in terms of protein, carbohydrate and DNA, except for the protein content of C. albicans biofilm. By SEM, Candida biofilms treated with SN revealed structural differences, when compared with the control groups. Further, SN showed a trend of agglomeration within the biofilms. Epifluorescence microscopy images suggest that SN induced damage on cell walls of the Candida isolates tested. Conclusions : In general, irrespective of concentration, SN affected the matrix composition and structure of Candida biofilms and these findings may be related to the mechanisms of biocide action of SN. Significance and Impact of the Study : This study reveals new insights about the behaviour of SN when in contact with Candida biofilms. SN may contribute to the development of therapies to prevent or control Candida infections.We thank David Williams (Cardiff University, Cardiff, UK) for providing strain 324LA/94. The authors also thank CAPES (grant BEX 1221/10-8) and FAPESP (2009/15146-5), Brazil, for supporting Douglas Roberto Monteiro work. The colloidal suspension of silver nanoparticles used herein was prepared and characterized by LIEC-CMDMC and INCTMN/FAPESP-CNPq, Sao Carlos, Brazil

Anti-bacterial activity of inorganic nanomaterials and their antimicrobial peptide conjugates against resistant and non-resistant pathogens

This review details the antimicrobial applications of inorganic nanomaterials of mostly metallic form, and the augmentation of activity by surface conjugation of peptide ligands. The review is subdivided into three main sections, of which the first describes the antimicrobial activity of inorganic nanomaterials against gram-positive, gram-negative and multidrug-resistant bacterial strains. The second section highlights the range of antimicrobial peptides and the drug resistance strategies employed by bacterial species to counter lethality. The final part discusses the role of antimicrobial peptide-decorated inorganic nanomaterials in the fight against bacterial strains that show resistance. General strategies for the preparation of antimicrobial peptides and their conjugation to nanomaterials are discussed, emphasizing the use of elemental and metallic oxide nanomaterials. Importantly, the permeation of antimicrobial peptides through the bacterial membrane is shown to aid the delivery of nanomaterials into bacterial cells. By judicious use of targeting ligands, the nanomaterial becomes able to differentiate between bacterial and mammalian cells and, thus, reduce side effects. Moreover, peptide conjugation to the surface of a nanomaterial will alter surface chemistry in ways that lead to reduction in toxicity and improvements in biocompatibility

Hydrodynamics of stirred tank reactors. A study with laser doppler velocimetry and computational fluid dynamics

Dissertação apresentada para obtenção do grau de Doutor em Engenharia Química, na Faculdade de Engenharia da Universidade do Porto, sob a orientação do Prof. Dr. José Carlos Lope

Antibacterial and Antifungal Thioglycolic Acid-Capped Silver Nanoparticles and Their Application on Wool Fabric as a Durable Antimicrobial Treatment

Currently used silver nanoparticle-based antimicrobial treatments are effective against bacteria and certain fungi but they have limited durability to washing. In this work, the surface of silver nanoparticles was modified with thioglycolic acid (TGA) to further enhance their antimicrobial activities and also to enable their binding to the surface of wool fibre. Silver nanoparticles were characterised by FTIR, UV-vis spectroscopy and TEM. The TGA-capped silver nanoparticles were covalently bonded to wool fibre surface by using 1-ethyl-3-[3-dimethylaminopropyl]-carbodiimide hydrochloride in combination with N-hydroxysuccinimide to provide enhanced durability to multiple washings, which is an issue for the nanosilver-based treatments used in wool textiles. The antimicrobial activities of this treated wool fabric were compared with the wool fabric treated with trisodium citrate (TSC)-capped silver nanoparticles (bonded by a silicone resin). The TGA-capped silver nanoparticle-treated wool fabric not only showed superhydrophilicity and excellent durability to washing but also excellent antibacterial activity along with moderate to excellent antifungal activity. The wool fabric treated with TSC-capped silver nanoparticles showed strong hydrophobicity and antibacterial activity but no antifungal activity. This work demonstrates that silver nanoparticles can be made antifungal by the capping with TGA and also the durability of the treatment to washing can be considerably enhanced