Neutral carrier Na+- and Ca2+-selective microelectrodes for intracellular application

Area of Science:

• Electrochemistry
• Biophysical Chemistry
• Cell Physiology

Background:

• Accurate measurement of intracellular ion concentrations is crucial for understanding cellular processes.
• Development of selective and stable microelectrodes is essential for in vivo and in vitro physiological studies.
• Existing microelectrode technologies face challenges in selectivity and long-term stability.

Purpose of the Study:

• To develop and characterize novel Na+- and Ca2+-selective microelectrodes for intracellular ion activity measurements.
• To evaluate the selectivity, stability, and response time of these microelectrodes.
• To assess their suitability for measuring physiological ion concentrations in cellular environments.

Main Methods:

• Fabrication of Na+-selective microelectrodes using ETH 227 and Ca2+-selective microelectrodes using ETH 1001.
• Determination of selectivity coefficients (kNaK, kNaMg, kNaCa, kCaK, kCaNa, kCaMg) using various methods and ion activity levels.
• Assessment of microelectrode potential stability, resistance, and response time.
• Evaluation of microelectrode performance in mixed ion solutions and across different ion concentration ranges.

Main Results:

• Na+-selective microelectrodes exhibited high selectivity for Na+ over K+ (kNaK: 0.01-0.02) and negligible interference from Mg2+ (kNaMg: ~0.005).
• Ca2+ interference on Na+-selective microelectrodes was observed (kNaCa: ~2), requiring careful handling under specific conditions.
• Ca2+-selective microelectrodes showed good sensitivity in the cytosolic free-Ca2+ range (10(-7)-10(-6) M) with stable potentials after initial equilibration.
• High selectivity for Ca2+ over K+ and Na+ was confirmed (kCaK: 10(-5)-10(-6), kCaNa: 10(-4)-10(-5)), with minimal Mg2+ interference (kCaMg: ~10(-7)).

Conclusions:

• Na+-selective microelectrodes are suitable for intracellular Na+ activity measurements, with potential Ca2+ interference needing consideration.
• Ca2+-selective microelectrodes are effective for measuring cytosolic Ca2+ activity within relevant physiological ranges.
• Both microelectrode types demonstrate stability and fast response, making them valuable tools for cellular ion research.