ZETA-POTENTIAL OF BONE FROM PARTICLE ELECTROPHORESIS - SOLUTION COMPOSITION AND KINETIC EFFECTS

The morphology of bone may be influenced by many factors, including el ectromechanical ones such as electric potentials, electric fields, or zeta potentials. Stress-generated potential studies in bone and partic le electrophoresis studies using calcium-deficient hydroxyapatite have shown that the zeta potential depends on the composition of the steep ing fluid and steeping time. To better quantify and understand these i n situ potential changes in bovine cortical bone, the effects of alter ations in calcium, phosphate, and fluoride concentrations in Neuman's Fluid (NF), which simulates in vivo bone extracellular fluid, were inv estigated using particle electrophoresis. The zeta potential increased in magnitude with increased calcium concentration in NF in as little as 17 min. Increasing phosphate concentration in NF also increased the zeta potential magnitude. These results provide support for a structu ral model of the bone matrix surface-bone fluid interface, which incor porates the bone surface proper (composed of collagen, mineral, and bo undary regions), stationary layer (in which ions, ionic complexes, and proteins may be adsorbed), and bone extracellular fluid. These result s, coupled with those of previous studies, indicate that the protein p hase probably has an important role in the determination of the physio logic zeta potential; the role of the mineral phase may also be import ant. (C) 1995 John Wiley and Sons, Inc.