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The standard theory regarding the interactions between polyelectrolytes and their counterions is based on long-range electrostatic interactions. However, aromatic counterions may undergo short-range aromatic-aromatic interactions with polyelectrolytes containing aromatic rings so that ion pairs may be formed. The charge of the polymeric aromatic groups and the linear aromatic density of the polyelectrolytes play an important role on the behavior of the systems. Self-aggregation of counterions on the polymer environment can be controlled. [ABSTRACT FROM AUTHOR]

Astaxanthin is a light sensitive molecule which is already approved as a dietary supplement, with a wide range of biological properties in humans and fishes. In this paper, we provide strategies to photostabilize the pigment through its inclusion in easy-to-prepare and scale up formulations, comprising non-toxic excipients. Astaxanthin has been formulated in biocompatible hierarchically assembled structures in order to produce model food to humans and fishes. The structures present increasing complexity in the following order: 1) oily nanodroplets stabilized by phospholipids; 2) chitosan-coated nanoemulsions produced after coating the nanodroplets with chitosan; 3) carrageenan-coated nanoemulsions produced after coating chitosan-coated nanoemulsions with carrageenan; 4) calcium alginate and chitosan tripolyphosphate beads including one of the nanosystems. The sensitivity to UV light of astaxanthin in both the nanosystems and the hydrogels has been evaluated. The nanoformulations produce protection of astaxanthin from photodegradation in the order nanoemulsions > carrageenan-coated nanoemulsions > chitosan-coated nanoemulsions. Chitosan beads furnish higher protection to astaxanthin than alginate beads. In a preliminary assay in fishes, alginate beads of 2–3 mm and 160 μm containing the nutrient were supplied to adult Danio rerio and juvenile Eleginops maclovinus , respectively. Both living species showed high rates of capturing the hydrogels in the water column, corroborating the attractiveness of the formulations as food for fishes. Due to the easy preparation of the formulations (that exclude thermal treatment or the use of toxic solvents), and the flexibility of these hierarchically assembled materials to incorporate other active molecules (proteins, polyunsaturated fatty acids, oligoelements, oral vaccines, antibiotics, antiparasitic, etc.), we postulate these formulations as ideal platforms to create foods for humans and animal species. [ABSTRACT FROM AUTHOR]

Abstract: The importance of the linear aromatic density of polyelectrolytes on the ability to bind and influence the state of aggregation of dyes such as rhodamine 6G is highlighted. The corresponding complexes present different interaction patterns with metal ions such as Cu2+, undergoing different spectroscopic changes. The chemical bases of these changes are discussed. The different polyelectrolytes studied, poly(sodium 4-styrenesulfonate), poly(sodium 4-styrenesulfonate-co-sodium maleate) at two different comonomer compositions (3:1 and 1:1), and poly(sodium acrylate-co-sodium maleate), bear different linear aromatic density and induce different R6G binding patterns, as seen by diafiltration and UV–vis spectroscopy of absorbance and fluorescence. As the linear aromatic density increases, smaller dye aggregates are induced in the systems. Thus, in the presence of a large excess of the polyelectrolyte showing the highest linear aromatic density, the dyes disperse on the polymer domain and no aggregation is detected. The interaction is less sensitive to the cleaving effect produced by the addition of NaCl 0.1M for the complexes that include the polyelectrolytes with the highest linear aromatic density. In the presence of Cu2+, the complexes formed with the polyelectrolytes showing the lowest linear aromatic density tend to cleave, producing the release of the dye from the polymer domain. On the contrary, the complexes formed with the polyelectrolytes showing the highest linear aromatic density effectively retain the dye in the presence of the divalent metal ion. Based on fluorescence changes by the addition of different amounts of Cu2+ to the solution, the potential of the polyelectrolyte/R6G complexes in applications as sensing materials is discussed. [Copyright &y& Elsevier]

The antibacterial activity against Staphylococcus aureus of aerogels fabricated from colloidal suspensions of chitosan/chondroitin sulfate nanocomplexes is analyzed. Upon freeze-drying the colloidal suspensions, the aerogels presented a porous structure made of microsheets and microfibers. The aerogels could, in addition, be loaded with antimicrobial agents. Loaded with the antibiotic erythromycin, the aerogels showed crystalline deposits, affecting the topography of the samples as well as their mechanical properties, showing a decrease on the apparent Young's modulus and hardness at 40% deformation. Loaded with elephant garlic (Allium ampeloprasum L. var. ampeloprasum) extract, the aerogels showed texturization of the microsheets and microfibers, and the higher relative mass allowed an increase on the apparent Young's modulus and hardness at 40% deformation with respect to pristine aerogels. Unloaded aerogels showed activity against Staphylococcus aureus, including a methicillin-resistant strain. The release of erythromycin from the aerogels to an agar environment is governed by equilibrium forces with the polysaccharides, which allow modulating the load of antibiotic and its concomitant diffusion from the material. The diffusion of the active components of the elephant garlic extract did not show a dependence on the polysaccharide content, revealing a week interaction. The elephant garlic extract resulted active against the methicillin-resistant Staphylococcus aureus strain, while resistance was found for the antibiotic, revealing the therapeutic potential of the natural extract. The antimicrobial aerogels may be used for several therapeutic purposes, such as healing of infected chronic wounds. [ABSTRACT FROM AUTHOR]