Cyclodextrin modulation of gallic acid in vitro antibacterial activity

The substitution of large spectrum antibiotics for natural bioactive molecules (especially polyphenolics) for the treatment of wound infections has come into prominence in the pharmaceutical industry. However, the use of such molecules depends on their stability during environmental stress and on their ability to reach the action site without losing biological properties. The application of cyclodextrins as a vehicle for polyphenolics protection has been documented and appears to enhance the properties of bioactive molecules. Therefore, the encapsulation of gallic acid, an antibacterial agent with low stability, by -cyclodextrin, (2-hydroxy) propyl--cyclodextrin and methyl--cyclodextrin, was investigated. Encapsulation by -cyclodextrin was confirmed for pH 3 and 5, with similar stability parameters. The (2-hydroxy) propyl--cyclodextrin and methyl--cyclodextrin interactions with gallic acid were only confirmed at pH 3. Among the three cyclodextrins, better gallic acid encapsulation were observed for (2-hydroxy) propyl--cyclodextrin, followed by -cyclodextrin and methyl--cyclodextrin. The effect of cyclodextrin encapsulation on the gallic acid antibacterial activity was also analysed. The antibacterial activity of the inclusion complexes was investigated here for the first time. According to the results, encapsulation of gallic acid by (2-hydroxy) propyl--cyclodextrin seems to be a viable option for the treatment of skin and soft tissue infections, since this inclusion complex has good stability and antibacterial activity.The authors are grateful for the FCT Strategic Project PEst-OE/EQB/LA0023/2013 and the Project "BioHealth-Biotechnology and Bioengineering approaches to improve health quality", Ref. NORTE-07-0124-FEDER-000027, co-funded by the "Programa Operacional Regional do Norte" (ON.2-O Novo Norte), QREN, FEDER. The authors also acknowledge the project "Consolidating Research Expertise and Resources on Cellular and Molecular Biotechnology at CEB/IBB", Ref. FCOMP-01-0124-FEDER-027462. This work is, also, funded by FEDER funds through the Operational Programme for Competitiveness Factors-COMPETE and National Funds through FCT-Foundation for Science and Technology under the project PEst-C/CTM/UI0264/2011. Additionally, the authors would like to thank the FCT for the grant for E. Pinho (SFRH/BD/62665/2009)

Electromagnetically induced transparency in a plasmonic system comprising of three metal-dielectric-metal parallel slabs: Plasmon- Plasmon interaction

In this paper, electromagnetically induced transparency (EIT) in a system consisting of associated arrays of parallel slabs (metal-dielectric-metal) is studied. The transmission coefficient, the reflection coefficient and the absorption coefficient as function of the incident light frequency by using the transfer matrix method is calculated and numerically discussed. Influence of the thickness of slab and the type of plasmonic metal on the induced transparency has been investigated. It is shown with decreasing the thickness of intermediate slab of length  (dielectric slab), the induced transparency increases due to the strong plasmon–plasmon couplings

Study of slow light in a composite consisting of core-shell cylindrical nanoparticles doped in a dielectric

In this paper, slow light in a composite consisting of core-shell nanoparticles doped in a dielectric is studied. The light-velocity slowing factor as a function of the incident light frequency is discussed and analyzed. The influence of the thickness of shell, the composition of core and shell and the geometrical shape of nanoparticles on the slowing factor is investigated. The effect of the plasmon-exciton on the slow light is addressed too

Applications of a Catch and Release Electrospray Ionization Mass Spectrometry Assay for Carbohydrate Library Screening

Applications of a catch and release electrospray ionization mass spectrometry (CaR-ESI-MS) assay for screening carbohydrate libraries against target proteins are described. Direct ESI-MS measurements were performed on solutions containing a target protein (a single chain antibody, an antigen binding fragment, or a fragment of a bacterial toxin) and a library of carbohydrates containing multiple specific ligands with affinities in the 10³ to 10⁶ M^–1 range. Ligands with moderate affinity (10⁴ to 10⁶ M^–1) were successfully detected from mixtures containing >200 carbohydrates (at concentrations as low as 0.25 μM each). Additionally, the absolute affinities were estimated from the abundance of free and ligand-bound protein ions determined from the ESI mass spectrum. Multiple low affinity ligands (∼10³ M^–1) were successfully detected in mixtures containing >20 carbohydrates (at concentrations of ∼10 μM each). However, identification of specific interactions required the use of the reference protein method to correct the mass spectrum for the occurrence of nonspecific carbohydrate–protein binding during the ESI process. The release of the carbohydrate ligands, as ions, was successfully demonstrated using collision-induced dissociation performed on the deprotonated ions of the protein–carbohydrate complexes. The use of ion mobility separation, performed on deprotonated carbohydrate ions following their release from the complex, allowed for the positive identification of isomeric ligands