New Quaternary Ammonium Derivatives Based on Citrus Pectin.

New citrus pectin derivatives carrying pendant N,N-dimethyl-N-alkyl-N-(2-hydroxy propyl) ammonium chloride groups were achieved via polysaccharide derivatization with a mixture of N,N-dimethyl-N-alkyl amine (alkyl = ethyl, butyl, benzyl, octyl, dodecyl) and epichlorohydrin in aqueous solution. The structural characteristics of the polymers were examined via elemental analysis, conductometric titration, Fourier Transform Infrared spectroscopy (FTIR) and 1D (1H and 13C) nuclear magnetic resonance (NMR). Capillary viscosity measurements allowed for the study of viscometric behavior as well as the determination of viscosity-average molar mass for pristine polysaccharide and intrinsic viscosity ([η]) values for pectin and its derivatives. Dynamic light scattering measurements (DLS) showed that pectin-based polymers formed aggregates in aqueous solution with a unimodal distribution. Critical aggregation concentration (cac) for the hydrophobic pectin derivatives were determined using fluorescence spectroscopy. Atom force microscopy (AFM) images allowed for the investigation of the morphology of polymeric populations obtained in aqueous solution, consisting of flocs and aggregates for crude pectin and its hydrophilic derivatives and well-organized aggregates for lipophilic pectin derivatives. Antimicrobial activity, examined using the disc diffusion method, proved that all polymers were active against Staphylococcus aureus bacterium and Candida albicans yeast.

Novel amphiphilic dextran esters with antimicrobial activity.

New amphiphilic dextran esters were obtained by polysaccharide functionalization with different substituted 1,2,3-triazoles-4-carboxylic acid via in situ activation with N, N'-carbonyldiimidazole. Nitrogen-containing heterocyclic derivatives were achieved by copper(I)-catalyzed cycloaddition reaction between organic azides and ethyl propiolate. Structural characteristics of the compounds were studied by elemental analysis, Fourier transform infrared and nuclear magnetic resonance spectroscopy (1H and 13C-NMR). Thermogravimetric analysis, differential scanning calorimetry and wide-angle X-ray diffraction were used for esters characterization. Properties of polymeric self-associates, formed in aqueous solution, were studied by dynamic light scattering and transmission electron microscopy. The critical aggregation concentration values for dextran esters, determined by fluorescence spectroscopy, were in the range of 4.1-9.5 mg/dL. Antimicrobial activity, investigated for some of the polymers by disc-diffusion method, pointed out that polysaccharide esters were active.

Antimicrobial activity of chemically modified dextran derivatives.

Cationic amphiphilic dextran derivatives with a long alkyl group attached to the reductive end of the polysaccharide chain and quaternary ammonium groups attached as pendent groups to the main dextran backbone were synthesized and tested for their antimicrobial properties against several bacteria and fungi strains. Dependence of antimicrobial activity on both polymer chemical composition (dextran molar mass, length of end alkyl group and chemical structure of ammonium groups) and type of microbes was highlighted by disc-diffusion method (diameter of inhibition zone) and broth microdilution method (minimum inhibitory concentrations). Polymers had antimicrobial activity for all strains studied, except for Pseudomonas aeruginosa ATCC 27853. The best activity against Staphylococcus aureus (Minimun Inhibitory Concentration 60µg/mL) was provided by polymers obtained from dextran with lower molecular mass (Mn=4500), C12H25 or C18H37 end groups, and N,N-dimethyl-N-benzylammonium pendent groups.

Formulation and evaluation of anise-based bioadhesive vaginal gels.

Various formulations of anise-based bioadhesive gels are prepared. Freeze-drying method was successfully employed and superporous scaffolds were obtained. The resulting porous microarchitectures are strongly influenced by the composition of hydrogel formulations and temperature of freezing. Anise-based hydrogels frozen in liquid nitrogen and lyophilized generate regular assembly of polyhedral pores. For Carbopol 934-based hydrogels it was determined G'>G'' for whole tested strain amplitude range indicating solid-like behaviour due to their dense network and entanglement and interaction through hydrogen bonds and van-der Waals forces. For sodium alginate-based hydrogels it was determined G''>G' for whole tested strain amplitude range accompanied by the extended linear viscoelastic region indicating liquid-like behaviour due to the formation of a stable "pseudo-gel" structure. Biocompatibility features of tested hydrogels were evaluated by contact angle measurements and determination of surface tension parameters. It was found that all anise-based hydrogel formulations manifest modest activity against S. aureus and S. lutea and no activity against tested Gram negative bacteria. Carbopol 934-based hydrogels containing anise exhibit antifungal activity against C. albicans, C. glabrata and C. Parapsilosis.