Solid-state ion-selective electrodes are used as scanning electrochemical microscope (SECM) probes because of their inherent fast response time and ease of miniaturization. In this study, we report the development of a solid-state, low-poly(vinyl chloride), carbon-based calcium ion-selective microelectrode (Ca2+-ISME), 25 μm in diameter, capable of performing an amperometric approach curve and serving as a potentiometric sensor. The Ca2+-ISME has a broad linear response range of 5 μM to 200 mM with a near Nernstian slope of 28 mV/log[aCa2+]. The calculated detection limit for Ca2+-ISME is 1 μM. The selectivity coefficients of this Ca2+-ISME are log KCa2+,A = -5.88, -5.54, and -6.31 for Mg2+, Na+, and K+, respectively. We used this new type of Ca2+-ISME as an SECM probe to quantitatively map the chemical microenvironment produced by a model substrate, bioactive glass (BAG). In acidic conditions (pH 4.5), BAG was found to increase the calcium ion concentration from 0.7 mM ([Ca2+] in artificial saliva) to 1.4 mM at 20 μm above the surface. In addition, a solid-state dual SECM pH probe was used to correlate the release of calcium ions with the change in local pH. Three-dimensional pH and calcium ion distribution mapping were also obtained by using these solid-state probes. The quantitative mapping of pH and Ca2+ above the BAG elucidates the effectiveness of BAG in neutralizing and releasing calcium ions in acidic conditions. (Graph Presented).
ASJC Scopus subject areas
- Analytical Chemistry