Crystalline particles from self-assembled divinyl oligomers

Crosslinkers for polysaccharides and proteins: Synthesis conditions, mechanisms, and crosslinking efficiency, a review

Polysaccharides and proteins are important macromolecules for developing hydrogels devoted to biomedical applications. Chemical hydrogels offer chemical, mechanical, and dimensional stability than physical hydrogels due to the chemical bonds among the chains mediated by crosslinkers. There are many crosslinkers to synthesize polysaccharides and proteins based on hydrogels. In this review, we revisited the crosslinking reaction mechanisms between synthetic or natural crosslinkers and polysaccharides or proteins. The selected synthetic crosslinkers were glutaraldehyde, carbodiimide, boric acid, sodium trimetaphosphate, N,N'-methylene bisacrylamide, and polycarboxylic acid, whereas the selected natural crosslinkers included transglutaminase, tyrosinase, horseradish peroxidase, laccase, sortase A, genipin, vanillin, tannic acid, and phytic acid. No less important are the reactions involving click chemistry and the macromolecular crosslinkers for polysaccharides and proteins. Literature examples of polysaccharides or proteins crosslinked by the different strategies were presented along with the corresponding highlights. The general mechanism involved in chemical crosslinking mediated by gamma and UV radiation was discussed, with particular attention to materials commonly used in digital light processing. The evaluation of crosslinking efficiency by gravimetric measurements, rheology, and spectroscopic techniques was presented. Finally, we presented the challenges and opportunities to create safe chemical hydrogels for biomedical applications.

Assembly of horseradish peroxidase within supported cationic bilayers

The interaction between horseradish peroxidase (HRP) and dioctadecyldimethylammonium bromide (DODAB) bilayers supported on polystyrene microspheres (PSS) or on flat silicon wafers was evaluated from the following techniques: (1) dynamic light-scattering for determining size distributions, zeta-potentials and polydispersities for dispersions; (2) spectrophotometric determination of HRP concentration in supernatants of centrifuged mixtures; (3) in situ ellipsometry for mean thickness of deposited layers on wafers; (4) kinetics of product appearance for oxidation of 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid by H(2) O(2) in presence of free or immobilized enzyme. HRP incorporation (3.0 mg/m(2)) did not alter mean diameter and zeta-potential of PSS/DODAB particles but reduced enzyme activity by 50%, though activity persisted after several rinsing steps. In situ ellipsometry could not detect any HRP layer on top of the DODAB bilayer. HRP insertion in the bilayer core explained all results for both systems. Useful biotechnological applications are anticipated for such assemblies.