tempo and betadex

Wood-based TEMPO-oxidised cellulose nanofibrils (toCNF) are promising materials for biomedical applications. Cyclodextrins have ability to form inclusion complexes with hydrophobic molecules and are considered as a method to bring new functionalities to these materials. Water sorption and mechanical properties are also key properties for biomedical applications such as drug delivery and tissue engineering. In this work, we report the modification with β-cyclodextrin (βCD) of toCNF samples with different carboxyl contents viz. 756 ± 4 µmol/g and 1048 ± 32 µmol/g. The modification was carried out at neutral and acidic pH (2.5) to study the effect of dissociation of the carboxylic acid group. Films processed by casting/evaporation at 40 °C and cryogels processed by freeze-drying were prepared from βCD modified toCNF suspensions and compared with reference samples of unmodified toCNF. The impact of modification on water sorption and mechanical properties was assessed. It was shown that the water sorption behaviour for films is driven by adsorption, with a clear impact of the chemical makeup of the fibres (charge content, pH, and adsorption of cyclodextrin). Modified toCNF cryogels (acidic pH and addition of cyclodextrins) displayed lower mechanical properties linked to the modification of the cell wall porosity structure. Esterification between βCD and toCNF under acidic conditions was performed by freeze-drying, and such cryogels exhibited a lower decrease in mechanical properties in the swollen state. These results are promising for the development of scaffold and films with controlled mechanical properties and added value due to the ability of cyclodextrin to form an inclusion complex with active principle ingredient (API) or growth factor (GF) for biomedical applications.

Topics: Adsorption; beta-Cyclodextrins; Cellulose, Oxidized; Cryogels; Cyclic N-Oxides; Freeze Drying; Nanofibers; Nanostructures; Porosity; Water

This study demonstrated a new enzymatic methodology to graft β-cyclodextrin onto wool. The primary hydroxyl groups in β-cyclodextrin were oxidized to aldehyde groups using laccase/2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), which reacted with the amino groups of wool to form Schiff bases. The effects of treatment conditions (treatment temperature, laccase dosage, TEMPO dosage, treatment time) on the aldehyde and carboxyl contents in β-cyclodextrin were studied. FTIR spectrum of oxidized β-cyclodextrin showed the presence of aldehyde and carboxyl groups. Results of MALDI-TOF mass spectroscopy confirmed the coupling of β-cyclodextrin to tyrosine, which was used as a model compound for wool. ATR-FTIR spectroscopy of the grafted wool confirmed the presence of β-cyclodextrin in grafted wool and the formation of a Schiff base between β-cyclodextrin and wool.

Topics: Aldehydes; Animals; beta-Cyclodextrins; Cyclic N-Oxides; Laccase; Oxidation-Reduction; Trametes; Tyrosine; Wool

Beta-cyclodextrin (beta-CD) was reacted with catalytic amounts of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO), sodium hypochlorite and sodium bromide at 2 degrees C and a pH value of 10 in water. The primary alcohol groups were selectively oxidized into carboxylate groups within a few minutes, and mono- and dicarboxy-beta-cyclodextrin sodium salts were isolated and characterized by 1H, 13C NMR and mass spectroscopy. With this reaction system, the degradation of the cyclodextrin was limited, provided the oxidation was performed at 2 degrees C, at constant pH value of 10, with catalytic amounts of TEMPO and controlled quantities of sodium hypochlorite and sodium bromide for the continuous regeneration of the oxoammonium salt.

Topics: Alcohols; beta-Cyclodextrins; Catalysis; Cyclic N-Oxides; Cyclodextrins; Magnetic Resonance Spectroscopy; Molecular Structure; Oxidation-Reduction