Current Organic Chemistry - Volume 17, Issue 2, 2013

In the last years, there are more and more reports published in prestigious journals addressing the successful application of essential oils for the eradication or prevention of microbial biofilms. Moreover, by combining the unique properties of nanoparticles with the antimicrobial activity of the essential oils, functionalized surfaces with an improved resistance to microbial colonization and biofilm development were obtained. These results may represent an interesting option for the medical field, opening new directions for the design of modified surfaces with desired and controlled anti-biofilm properties.

Staphylococcus (S.) aureus is a versatile human pathogen responsible for both nosocomial and community acquired infections. The ability of this opportunistic pathogen to cause a large spectrum of infections is due to an impressive spectrum of virulence determinants. The coordinated expression of many virulence determinants during the infectious process is regulated by the agr quorum-sensing system (QS). Different studies have shown that agr mutants are less virulent comparatively with their wild counterparts. Thus, the inhibition of quorum sensing genes expression may represent a new strategy of virulence and pathogenicity attenuation of S. aureus clinical strains. The aim of this paper was to review the main types of S. aureus quorum sensing inhibitors (QSI) known until present, focusing on a new strategy of virulence attenuation based on probiotics. It was demonstrated by real-time RT-qPCR that the soluble factors accumulated in the probiotic cultures are inhibiting the QS agr genes expression in S. aureus clinical strains, representing thus an interesting, new anti-microbial strategy for the prevention and therapy of staphylococcal infections.

Nano-sized silver powders coated with sodium oleate (NanoAg@C18) was prepared by a simple wet chemical route and characterized by FT-IR, DTA-TG, TEM, SAED and EDS. The main objective of this research was to successfully employ the NanoAg@C18 for the inhibition of bacterial and fungal biofilms in vitro development on catheter sections with a film-coated surface. The lower value of the relative microbial biomass formed on the surface of the modified prosthetic devices demonstrates the anti-biofilm efficiency of the NanoAg@C18 coating and the potential use of this nanosytem for obtaining improved medical devices.

New dibenzo[b,e]thiepins were synthesized, characterized by elemental analysis, spectral studies (1H-NMR, 13C-NMR, IR) and screened for their microbicidal and antibiofilm properties. The new dibenzo[b,e]thiepins and their sulfones exhibited a broad spectrum of antimicrobial activity (superior for the S-oxidized compounds) being effective at low concentrations against a wide range of infectious microorganisms. The oximes exhibited anti- A. baumanii activity. Some of the compounds exhibited good antibiofilm activity against the Gram-negative, non-fermentative bacilli P. aeruginosa and A. baumanii, and their possible target suggested by molecular modeling being the synthesis of the quorum sensing molecules employed by the Gram-negative microorganisms represented by N-acyl-l-homoserine lactones.

The aims of this research were to obtain improved wound dressings based on collagen (COLL), polysaccharides (dextran= DEX, diethylaminoethyl-cellulose= DEAEC), silica network and usnic acid, as quorum sensing inhibitor. FT-IR, SEM, interaction with eukaryotic cells and a novel protocol to evaluate the antimicrobial activity of the new wound dressing, firstly reported in literature were used for the characterization of fabricated wound dressings. The obtained wound dressings are not cytotoxic, do not influences the mesenchymal stem and exhibit good anti-biofilm properties. Taken together, these results are suggesting that the new systems can be safely used for local applications on the lesional tissues.

Interaction of the single-stranded DNA (ssDNA) aptamers and proteins was investigated on graphene oxide (GO)-based biosensors. GO was applied for biological applications because of its unique properties, which include water dispensability, exclusive selection of ssDNA, and fluorescence-quenching effects. In this study, aptamer-functionalized GO sheets of nanometer-scale thickness and micrometer-scale dimension were developed. Based on a simple mixed-and-measured strategy, platelet-derived growth factors (PDGF), the tumor marker of ovarian cancer, triggered aptamers conformation switched and deliberated aptamers from GO surface according to thermal dynamic analysis. By functionalizing with various aptamers on GO, the strategy could provide designed functions on GO-based biosensors, bioreactors, and other devices.

The purpose of this study was to investigate how a viral infection affecting the epithelial cells could be influenced by the presence of the opportunistic Staphylococcus aureus soluble mediators. The viral antigens presence, apoptosis and cytokine profiles of HeLa cells infected with HSV-1 and pre-/postreated with different bacterial soluble fractions were evaluated. Soluble bacterial molecules could modulate HeLa cells functions to prevent the development of viral infection, but later stages of viral infection are less affected by bacterial soluble mediators. The in vitro cooperative action of HSV-1 and of S. aureus soluble fractions modulated the immune response of the infected HeLa cells, mainly by triggering the release of pro-inflammatory cytokines.

Control orientation and interparticle spacing of self-assembled nanoparticles can provide versatile functional materials for optical and electronic applications. In this study, we have obtained a glass substratum with tunable optical properties using flowing control and bimolecular competition. The surface of glass was modified from immobilized stretchable gold nanoparticle chains. The long and periodic single-stranded DNA nanotemplates were prepared using Phi29 DNA polymerase molecular machinery according to precise molecular biology regulation. Gold nanoparticle (Au NP) docked at the default sites of the nanotemplates and optical anisotropic absorption were enhanced by approximately 55 % by using tunable, flexible, and oriented one-dimensional metallic nanostructures.

Bacteria commonly communicate with each other by a cell-to-cell signaling mechanism known as quorum sensing, using soluble mediators. Recent studies showed that these molecules target not only bacteria, but also interact with the eukaryotic host. Pseudomonas aeruginosa infection occurs both in acute or chronic states in a variety of respiratory and urinary infections. These infections are often difficult to treat, and numerous therapeutic options, besides antibiotics, have been searched. In this context quorum-sensing inhibitors could represent an attractive potential therapeutic strategy with promising results.

During the last years significant efforts have been made to discover compounds with inhibitory activity of quorum-sensing systems, which could represent an anti-pathogenic strategy, since they will inhibit the coordinated expression of virulence determinants, without interfering with bacterial growth, being less likely to generate resistance. The present study is reviewing the main types of quorum sensing inhibitors known to date, that manifest the potential to be used as anti-virulence drugs for the treatment of infections with multidrug resistant P. aeruginosa strains, and describes a new strategy of virulence attenuation based on organic acids produced by probiotic strains, which have been proved to influence in sub-inhibitory (sI) grown concentrations the QS genes expression in P. aeruginosa multidrug resistant strains, proving that the organic acids secreted by probiotics could act as quorum sensing inhibitors.

The aim of this paper is to review the antimicrobial activity of thiourea derivatives against planktonic and adherent bacterial and fungal strains, as well as to show how nanotechnology could improve the intrinsic antimicrobial activity of the novel substances, by obtaining biocompatible nanocomposites based on magnetite nanoparticles and newly synthesized 2-((4-ethylphenoxy)methyl)-N- (alkylphenylcarbamothioyl) benzamides, which proved increased resistance to microbial colonization or inhibited the development of already existent biofilms, revealing a great potential for biomedical applications.

Three new potent CO2-philic propane derivatives were designed and synthesized. Their structures were characterized by NMR, FTIR, and elemental analysis. Phase behavior of the three compounds was investigated at temperatures ranging from 313 K to 333 K and pressures from 9.1 MPa to 16.1 MPa in supercritical carbon dioxide, the solubility differences were discussed. The experimental solubility data were calculated and correlated by the two density-based models: Bartle and Chrastil, and satisfied agreements were obtained. Additionally, the partial molar volumes V2 for each compound were also estimated in the supercritical phase using the theory developed by Kumar and Johnston.

Present work is dedicated to studies of kinetic regularities of α-ethylacrolein and crotonaldehyde oxidation in methanol, allyl alcohol and glycidol. Kinetic model of the reaction has been designed based on experimental data. Rate constants of hydrogen peroxide disappearance and rate constants of unsaturated acid and its ester formation for both aldehydes in different alcohols at various catalyst concentrations and temperatures have been calculated. The reaction activation parameters have also been calculated. Dependences of ester/ acid ratio on the reaction conditions have been ascertained. Our results indicate the dependence of the reaction rate and the reaction products composition on type of aldehyde and alcohol.

Novel pyrazoles, bipyrazoles and pyrazol-3-ylpyrazolo[3,4-d]pyrimidines were synthesized using the versatil synthon 2-(1Hbenzimidazol- 2-yl)-3,3-bis(methylthio) acrylonitrile (1). Reactions were carried out under silent and ultrasonic conditions. In general, improvement in rates and yields were observed when reactions were carried out under ultrasonic irradiation compared with silent condition. Structures of the products were established on analytical and spectral data.