Imparting bone affinity to glycoproteins through the conjugation of bisphosphonates.
OBJECTIVE
To develop a novel means of conjugating bisphosphonates onto the carbohydrate moieties of glycoproteins to enhance protein affinity to bone.


METHODS
1-Amino-1,1-diphosphonate methane (aminoBP) was conjugated onto the carbohydrate moietites of oxidized fetuin by using 4-(maleimidomethyl)cyclohexane-1-carboxyl-hydrazide (MMCCH). Bone affinity of the resulting conjugates was compared to proteins obtained from another means of conjugation, whereby aminoBP was conjugated onto fetuin's lysine moieties by using succinimidyl-4-(N-maleimidomethyl)-cyclohexane-1-carboxylate (SMCC).


RESULTS
The use of the MMCCH resulted in the conjugation of up to seven aminoBPs per molecule of fetuin. These conjugates gave a 2.6-, 2.0-, 30.5-. and 1.84-fold increased affinity for untreated, ashed, demineralized bone and hydroxyapatite, respectively, as compared to conjugates from the SMCC reaction. Both conjugates exhibited a pH-independent, equally slow degradation in adult bovine serum-containing media.


CONCLUSIONS
The use of the MMCCH chemistry to conjugate aminoBP onto fetuin was feasible. Furthermore, the described processes of conjugation resulted in amino-BP-dependent increase in the glycoprotein's affinity to various bone matrices in a manner that exceeds the affinity produced by the previously established method, which used SMCC.
Gittens
Sébastien A
SA
Faculty of Pharmacy & Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta T6G 2G6, Canada.
Matyas
John R
JR
Zernicke
Ronald F
RF
Uludağ
Hasan
H
D000818:Animals; D001857:Bone Matrix / Q000378:metabolism*; D004164:Diphosphonates / Q000737:chemistry / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D011485:Protein Binding / Q000502:physiology; D051381:Rats
D004164:Diphosphonates; D006023:Glycoproteins