Adsorption and Release Properties of Seven Anticancer Compounds on Hydroxyapatite

Abstract

The adsorbed amounts of seven anticancer compounds on hydroxyapatite (HAp) were compared: fluorouracil (5-FU), cyclophosphamide (CPA), mercaptopurine (6-MP), cytarabine (Ara-C), azacytidine (5-AC), mitoxantrone (MXT), and doxorubicin (DOX). The adsorbed amounts of 5-FU, CPA, 6-MP, Ara-C and 5-AC were very small at several mg/g-HAp. On the contrary, those of MXT and DOX were much larger of 44 and 64 mg/g-HAp, respectively. These larger amounts may be ascribed to higher acidity of MXT and DOX: hydroxyl groups attached to aromatic ring may lead to the higher H⁺-donating ability than the other five compounds, promoting adsorption on HAp with basic character. The desorption rate of DOX in 100 mM phosphate buffered solution (PBS) was more than two times that of MXT, indicating the weaker binding strength of DOX to the surface of HAp. The larger amount and the higher desorption rate of DOX were due to its steric structure and self-association through π–π stacking of the aromatic rings, hydrogen bond or dipole effect of hydroxyl groups of the molecules.