The adsorption of polyelectrolytes on hydroxyapatite crystals

The adsorption of two polyelectrolytes, poly-L-Glutamate and poly-l-Asparta te, on hydroxyapatite (HAP) crystals was studied both experimentally and th eoretically. Langmuir adsorption isotherms were obtained for both these mol ecules, with binding constants K = 6 x 10(6) and 3 x 10(6) M-1, respectivel y, at 37.0 degrees C, pH 7.4, and 0.15 M ionic strength. A theoretical anal ysis of the data, based on a model proposed by Hesselink, suggested a "trai n-loop" type of adsorption with non-electrostatic energy terms 3.51 and 4.7 6 (kT) for poly-L-Glu and poly-L-Asp, respectively. (C) 1999 Academic Press .