In situ forming hydrogels of new amino hyaluronic acid/benzoyl-cysteine derivatives as potential scaffolds for cartilage regeneration

A new chemical strategy is described to link ethylenediamino (EDA) groups to primary hydroxyl groups of hyaluronic acid (HA) and the obtained derivatives have been characterized by 1H-NMR and 13C-NMR analyses. Such HA–EDA derivatives have been exploited to control the functionalization degree in benzoyl-cysteine (BC) groups, chosen as moieties able to allow both self-assembling in aqueous media and an oxidative crosslinking. In particular, the kinetics of oxidation of thiol groups in HA–EDA–BC derivatives has been studied in Dulbecco's Phosphate Buffer Solution (DPBS) pH 7.4 by colorimetric assays and rheological measurements. Mechanical properties of chemical hydrogels obtained after oxidative crosslinking have been evaluated by using two different concentration values (1 and 1.5% w/v) of HA–EDA–BC. These hydrogels show a dense interconnected fibrillar structure similar to the extracellular matrix of soft tissue and a resistance to chemical and enzymatic hydrolysis. Therefore, the potential suitability of HA–EDA–BC hydrogels as scaffolds for cartilage regeneration has been preliminarily assessed using primary human chondrocytes and evaluating their viability and ability to produce extracellular collagen.