Synthesis and characterization of tyramine-based hyaluronan hydrogels

Abstract

Hyaluronan is particularly attractive for tissue engineering and repair because it: (1) is a normal component of the extracellular matrices of most mammalian tissues; (2) contributes to the biological and physical functions of these tissues; and (3) possesses excellent biocompatibility and physiochemical properties. In the present study, we characterize a two-step enzymatic cross-linking chemistry for production of tyramine-based hyaluronan hydrogels using fluorophore-assisted carbohydrate electrophoresis, enzymatic digestion, and spectroscopy including absorbance, fluorescence and (1)H NMR. Substitution on hyaluronan of tyramine and other adducts from unproductive side reactions depends on the molar ratio of tyramine to carbodiimide used during the substitution (step 1) reaction. Results indicate that relatively low tyramine substitution is required to form stable hydrogels, leaving the majority of hyaluronan disaccharides unmodified. Sufficient native HA structure is maintained to allow recognition and binding by b-HABP, a HA binding complex typically found in normal cartilage biology. Hydrogels were formed from tyramine-substituted hyaluronan through a peroxidase-dependent cross-linking (step 2) reaction at hyaluronan concentrations of 2.5 mg/ml and above. Uncross-linked tyramine-substituted hyaluronan was characterized after hyaluronidase SD digestion. Cross-linked hydrogels showed increased resistance to digestion by testicular hyaluronidase and hyaluronidase SD with increasing hyaluronan concentration. Cells directly encapsulated within the hydrogels during hydrogel cross-linking remained metabolically active during 7 days of culture similar to cells cultured in monolayer.

Preparation of carboxymethyl cellulose based microgels for cell encapsulation

“…(1)) and the benzene skeleton vibration (1561 and 1611 cm -1 ). (Figure 2c) showed " of anomeric protons at 4.15 and 4.42 ppm, and sugar ring protons between 3.11 and 3.99 ppm for both macromolecules [28]. The signals at 7.21 and 6.84 ppm of CMC-Ph spectrum were attributed to the aromatic protons of 4-hydroxybenzylamine being grafted with CMC (CMC-g-Ph, 1a and 1b).…”

Diels−Alder Click Cross-Linked Hyaluronic Acid Hydrogels for Tissue Engineering

“…HA derivates are commonly synthesized using EDCI chemistry 31,94,95 . This requires a high excess of reagents with respect to HA (20 -40 molar excess) due to the limited yield of amidation processes in aqueous media 96,97 .…”

The use of dopamine-hyaluronate associate-coated maghemite nanoparticles to label cells

“…This is contrary to information from reports in which the formation of a covalent bond between HA and DPA was assumed according to nuclear magnetic resonance spectra. 18,25,26 Carbodiimides, thus, were not found to be suitable coupling agents to covalently attach DPA to HA. Nevertheless, the reaction between the amine groups of DPA and the carboxyl groups of HA yielded an ionic associate ( Figure 3) as confirmed by elemental analysis; compared with HA, nitrogen content was increased in the DPA-HA associate ( Table 1).…”