Interaction of Amino Acid and Dipeptide β-Naphthylamide Derivatives with Hyaluronic Acid and Human Serum Albumin Studied by Capillary Electrophoresis Frontal Analysis

Interactions of drug candidates with the biomacromolecules of the synovial fluid affect drug targeting to the articular cartilage as well as clearance from the synovial space upon intra-articular administration. Hyaluronic acid (HA) and human serum albumin (HSA) are two main components existing in the synovial fluid. To this end, we investigated the affinity of seven cationic amino acid and dipeptide β-naphthylamide derivatives towards HA and HSA in order to shed light on possible relationships between physicochemical properties, in particular charge state, and biomacromolecular interactions to increase the joint residence time. Capillary electrophoresis frontal analysis was used for characterization of the binding of the derivatives to hyaluronic acid and HSA at 25 °C in acetate buffer (pH 4.65) and phosphate buffer (pH 7.40), respectively. Linear binding isotherms were observed for the ligand–hyaluronic acid interactions and the obtained binding constants ranged from 43 to 133 M−1. The average fraction of bound ligand towards hyaluronic acid increased with increasing the net charge of the ligands but was less than 67 % for all investigated ligands. The obtained binding constants of the ligands with HSA varied in the range of 103–106 M−1. The interactions of low-molecular weight derivatives with hyaluronic acid were highly dependent on the ligand charge state. This trend was not observed for the interactions with HSA. The obtained affinity data may provide useful information in the design of cartilage adhesive prodrugs with extended residence time in the synovial cavity.