Synthesis and Partial Characterization of Hydrogels Obtained via Glutaraldehyde Crosslinking of Acetylated Chitosan and of Hyaluronan Derivatives

Abstract

Hydrophilic networks based on functionalized hyaluronic acid and on partially acetylated chitosan, respectively, have been obtained. In the case of hyaluronic acid (HA), primary amino functionalities have been introduced along the polysaccharide chains. The ensuing derivatives, i.e., HA-lysine (HA-K), HA-diamino pentane (HA-DAP), and HA-glycine-lysine (HA-GK), have been characterized by high field NMR spectroscopy. NMR 2D-DOSY experiments have allowed us to optimize the purification procedure. Chitosan was made soluble in water by partial acetylation. Cross-linking reactions have been performed using glutaraldehyde. The obtained networks have been qualitatively characterized by means of (13)C CP-MAS NMR technique. The hydrogels have been characterized also in terms of water uptake.

Hyaluronic Acid in the 3^rd Millennium

“…Since glutaraldehyde is toxic, a particular handling is required during the reaction and the purification of the final product [160,161].…”

“…However, some of these present important drawbacks: for example, Ugi condensation -useful to crosslink HA chains through diamide linkages-requires a strongly acidic pH (3), the use formaldehyde, which is carcinogenic, and cyclohexyl isocyanide, which determines a pending undesired cyclohexyl group in the final product [145,160]. HA amidation with 1,1'-carbonyldiimidazole [171] or 2-chloro-1-methylpyridinium iodide [148] as activating agents are performed in DMSO and DMF respectively: hence, HA conversion into TBA salt and longer purification steps are needed.…”

Use of Polyvinyl Alcohol as a Solubility Enhancing Polymer for Poorly Water-Soluble Drug Delivery (Part 2)

“…Diffusion-ordered spectroscopy (DOSY) or sometimes called diffusion-ordered NMR spectroscopy and diffusionordered correlation spectroscopy has been used to determine the drug complexation with cyclodextrins (43), drug release from a hydrogel matrix (44), identification of fake formulations of commercial products (45), and to see interactions of polymers and drugs in solution (46). DOSY is a measure of diffusion and can distinguish different components in a formulation by the rate of diffusion and location on the spectra.…”

Influência da adição de plastificante do processo de reticulação na morfologia, absorção de aguá e propriedades mecânicas de filmes de alginato de sódio

“…A diminuição da taxa de intumescimento com a reticulação foi observada em micropartículas de alginato de sódio reticuladas com glutaraldeído 42 , em polissiloxanos reticulados 43 , em géis de quitosana parcialmente acetilada e glutaraldeído 44 e em membranas de polivinil álcool 45 . Em geral, com a presença de reticulante ocorre maior superposição das cadeias, favorecendo a formação de maior número de pontos de reticulação.…”

“…Este comportamento confirma a reação aparente de reticulação do formaldeído com os grupos hidroxila do sorbitol. Este efeito foi similar à diminuição na absorção de água com o aumento da concentração de reticulante observada em membranas de quitosana/proteína de soja 51 e em géis de quitosana parcialmente acetilada e glutaraldeído 44 . …”