title: Carbon-Based Solid-State Calcium Ion-Selective Microelectrode and Scanning Electrochemical Microscopy: A Quantitative Study of pH-Dependent Release of Calcium Ions from Bioactive Glass.
abstract: 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 (Ca(2+)-ISME), 25 μm in diameter, capable of performing an amperometric approach curve and serving as a potentiometric sensor. The Ca(2+)-ISME has a broad linear response range of 5 μM to 200 mM with a near Nernstian slope of 28 mV/log[a(Ca(2+))]. The calculated detection limit for Ca(2+)-ISME is 1 μM. The selectivity coefficients of this Ca(2+)-ISME are log K(Ca(2+),A) = -5.88, -5.54, and -6.31 for Mg(2+), Na(+), and K(+), respectively. We used this new type of Ca(2+)-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 ([Ca(2+)] 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 Ca(2+) above the BAG elucidates the effectiveness of BAG in neutralizing and releasing calcium ions in acidic conditions.
authors: Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States.
authors: Jyothir Ganesh
authors: JG
authors: Ummadi
authors: Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States.
authors: Corey J
authors: CJ
authors: Downs
authors: Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States.
authors: Vrushali S
authors: VS
authors: Joshi
authors: Department of Restorative Dentistry, Oregon Health & Science University , Portland, Oregon 97239, United States.
authors: Jack L
authors: JL
authors: Ferracane
authors: Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States.
authors: Dipankar
authors: D
authors: Koley
mesh_terms: D002118:Calcium / Q000032:analysis*; D002244:Carbon / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D017736:Ion-Selective Electrodes; D008839:Microelectrodes
chemical_list: D002244:Carbon; D002118:Calcium