Stress-generated potentials in bone: effects of bone fluid composition and kinetics

Area of Science:

• Biophysics
• Biomaterials Science
• Orthopedics

Background:

• Stress-generated potentials (SGPs) are attributed to electrokinetic phenomena at the bone's internal surfaces.
• SGPs are proportional to the zeta potential of the bone surface-bone fluid interface.
• The labile nature of this interface may explain inconsistencies in SGP polarity observations.

Purpose of the Study:

• To investigate the influence of steeping fluid composition on SGPs.
• To determine if the bone surface-bone fluid interface is labile and affects SGP polarity.
• To explore the implications for understanding bone electrokinetics and remodeling.

Main Methods:

• Examined 87 bone samples from 15 animals using four-point bending tests.
• Assessed SGPs after steeping in various solutions (distilled water, constant ionic strength) for up to 65 hours.
• Analyzed the effects of calcium and fluoride ions on SGP sign and magnitude.

Main Results:

• Concentration-dependent inversions in SGP polarity were observed with calcium and fluoride.
• A new steady state for SGPs was reached within approximately 18 hours.
• Fluoride's effect on SGP sign was reversible, while calcium's was not explicitly stated as reversible.
• The zeta potential at the bone interface demonstrated significant changes in both magnitude and sign.

Conclusions:

• The bone surface-bone fluid interface is labile and its properties can be altered by the surrounding fluid.
• Changes in ion concentration, particularly fluoride, can reverse SGP polarity.
• Sample preparation is critical for accurately studying the bone-fluid interface in vivo.
• These findings support the role of SGPs in bone remodeling processes.