Boronic acid and diol-containing polymers: how to choose the correct couple to form "strong" hydrogels at physiological pH.

Dynamic covalent hydrogels crosslinked by boronate ester bonds are promising materials for biomedical applications. However, little is known about the impact of the crosslink structure on the mechanical behaviour of the resulting network. Herein, we provide a mechanistic study on boronate ester crosslinking upon mixing hyaluronic acid (HA) backbones modified, on the one hand, with two different arylboronic acids, and on the other hand, with three different saccharide units.

Rheology of partially and totally oxidized red seaweed galactans.

Agarose and κ-carrageenan were oxidized using (2,2,6,6-tetramethylpiperidinyl)oxy (TEMPO) in the presence of NaOCl and NaBr. Products with several degrees of oxidation were structurally characterized. The mechanical spectra were determined: derivatives with a medium to high degree of oxidation give rise to polysaccharides that behave like dilute solutions in water, whereas those with a degree of oxidation close to 20 % keep the gelling properties with a different thermo-rheological response towards pH (6.

Design of Soft Nanocarriers Combining Hyaluronic Acid with Another Functional Polymer for Cancer Therapy and Other Biomedical Applications.

The rapid advancement in medicine requires the search for new drugs, but also for new carrier systems for more efficient and targeted delivery of the bioactive molecules. Among the latter, polymeric nanocarriers have an increasingly growing potential for clinical applications due to their unique physical and chemical characteristics. In this regard, nanosystems based on hyaluronic acid (HA), a polysaccharide which is ubiquitous in the body, have attracted particular interest because of the biocompatibility, biodegradability and nonimmunogenic property provided by HA.

Disaccharides obtained from carrageenans as potential antitumor agents.

Carrageenans are sulfated galactans found in certain red seaweeds with proven biological activities. In this work, we have prepared purified native and degraded κ-, ι-; and λ-carrageenans, including the disaccharides (carrabioses) and disaccharide-alditols (carrabiitols) from seaweed extracts as potential antitumor compounds and identified the active principle of the cytotoxic and potential antitumor properties of these compounds. Both κ and ι-carrageenan, as well as carrageenan oligosaccharides showed cytotoxic effect over LM2 tumor cells.

Gracilariopsis hommersandii, a red seaweed, source of agar and sulfated polysaccharides with unusual structures.

Red seaweed Gracilariopsis hommersandii produces important amounts of non-gelling galactans, which were extracted with hot water (GrC, yield, 37%, viscosity average molecular weight, Mv 109 kDa), comprising agarose and sulfated galactan structures. The alkali modified derivative, GrCTr (Mv 95 kDa), gave a galactose:3,6-anhydrogalactose molar ratio of 1.0:0.

Minor polysaccharidic constituents from the red seaweed Hypnea musciformis. Appearance of a novel branched uronic acid.

Two polysaccharide fractions isolated from Hypnea musciformis after room temperature- and hot water extraction, soluble after KCl precipitation of the more abundant carrageenans, were subfractionated by ion-exchange chromatography eluting with increasing concentrations of NaCl. The lowest NaCl concentration (0.2M) eluted agarans.

DFT/PCM theoretical study of the conversion of methyl 4-O-methyl-α-d-galactopyranoside 6-sulfate and its 2-sulfated derivative into their 3,6-anhydro counterparts.

Modeling of the conversion of methyl 4-O-methyl-α-d-galactopyranoside 6-sulfate (2) and 2,6-disulfate (1) into methyl 3,6-anhydro-4-O-methyl-α-d-galactopyranoside (4) and its 2-sulfate (3), respectively (Scheme 1) has been carried out using DFT at the M06-2X/6-311 + G(d,p)//M06-2X/6-31 + G(d,p) level with the polarizable continuum model (PCM) in water. The three steps necessary for the alkaline transformation of 6-sulfated (and 2,6-disulfated) galactose units into 3,6-anhydro derivatives were evaluated. The final substitution step appears to be the rate limiting, involving an activation energy of ca.

Partial and total C-6 oxidation of gelling carrageenans. Modulation of the antiviral activity with the anionic character.

The optimal conditions for the full C-6 oxidation of κ- and ι-carrageenans using (2,2,6,6-tetramethylpiperidinyl)oxy (TEMPO) in the presence of sodium hypochlorite and sodium bromide were assessed. The fully oxidized products were characterized by NMR spectroscopy. Partially oxidized products were also obtained and analyzed by chemical and spectroscopical methods.

Chemical and rheological characterization of the carrageenans from Hypnea musciformis (Wulfen) Lamoroux.

This work reports a chemical and rheological study of the carrageenans from Hypnea musciformis, a red seaweed commercially known for its production of κ-carrageenan. The polysaccharides were extracted with water both at room temperature and at 90 °C: the yield of the latter was about six times larger than the former. Fractionation with KCl yielded a large proportion (50-67%) of a precipitate with 0.