Dual-functionalized hyaluronic acid as a facile modifier to prepare polyanionic collagen

Hyaluronic acid (HA) is a natural polysaccharide possesses outstanding physiological activities. In this work, HA was activated as a novel collagen modifier via the esterification reaction between N-hydroxysuccinimide (NHS) and the carboxyl groups of HA. Both of Fourier transform infrared spectroscopy (FTIR) and 1H- nuclear magnetic resonance (NMR) spectra indicated the successful synthesis of HA-NHS esters. As reflected by FTIR, circular dichroism (CD) and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), collagens modified with HA-NHS ester maintained its intact triplex structure with larger molecular weight. The resultant polyanionic collagen displayed an excellent dissolubility in the neutral water to form a clear solution, due to the significantly lower isoelectric point values (3.8–4.4) compared with that of the native collagen (7.1). In addition, the thermal transition temperature of collagen was significantly increased (16 °C) after modifying with HA-NHS esters. Both of the aggregation morphology and rheological property exhibited high dependence on the NHS/COOH ratio of HA-NHS esters, as reflected by field-emission scanning electron microscopy (FESEM) and rheological test, respectively. The present study offered a novel dual-functional modifier based on the design of HA-NHS ester to obtain water-soluble collagen with desired thermal stability and rheological property, which will significantly widen the application range of collagen, especially in the fields of injectable biodegradable materials and cosmetics.