Structural and conformational differences of acylated hyaluronan modified in protic and aprotic solvent system

Acylated hyaluronan (HA) in aqueous (DMSO/H2O) and nonaqueous (DMSO) solutions was studied by means of nuclear magnetic resonance, differential scanning calorimetry (DSC), mass spectrometry and UV/vis spectroscopy. It has been demonstrated that structural and conformational properties of the acylated hyaluronan derivates are strongly dependent on the nature of reaction solvent. Acylation in DMSO was more selective than that carried out in DMSO/H2O, though in both cases in average a maximum of one acyl chain was detected per HA dimer. The hydrophobic functionalization of hyaluronan induced its interaction with hydrophobic dye as a consequence of acyl chain aggregation. The higher the degree of acylation the more hydrophobic dye was interacting with HA. For concentrated samples, aggregation was more evident in case of acylated HA in aqueous solution. This phenomenon was explained by its different conformational arrangement in solution which was further supported by DSC data indicating an existence of hydrophobic cavities. The formation of self-aggregated assemblies indicates potential applications of this type of HA derivate as drug delivery system.