Streaming potential and the electromechanical response of physiologically-moist bone

Area of Science:

• Biophysics
• Biomaterials Science
• Orthopedics

Background:

• Electrical signals in bone are generated by mechanical loading.
• Two proposed mechanisms are piezoelectricity and streaming potential.
• Distinguishing between these mechanisms in wet bone is challenging.

Purpose of the Study:

• To investigate the dominant mechanism for electrical signal generation in physiologically moist bone.
• To differentiate between piezoelectricity and streaming potential under bending conditions.
• To provide experimental data supporting the streaming potential theory.

Main Methods:

• Direct measurement of streaming potential by forcing electrolytes through bone discs.
• Measuring potential difference across bone specimens under varying fluid pressure.
• Conducting bending tests on wet bone specimens in controlled electrolyte solutions.

Main Results:

• Both piezoelectricity and streaming potential depend on strain gradient and are proportional to strain rate.
• Specimen mechanical relaxation influences the current-voltage relationship, with a longer time constant than RC decay.
• Direct streaming potential measurements provided data on electrolyte concentration and viscosity effects.
• Bending tests indicated streaming potentials are dominant over piezoelectricity in wet bone.

Conclusions:

• Streaming potential is the predominant mechanism for electrical signal generation in wet bone under bending.
• Experimental evidence supports the role of fluid flow and ion movement in bone's electro-mechanical response.
• Understanding this mechanism is crucial for bone healing and tissue engineering applications.