Flexible Ion-Selective Ca2+ and pH Microsensors to Study Biofilm/Biomaterials Interface in Real-Time

Abstract

Solid-state potentiometric sensors have an inherent advantage of miniaturization. We developed a 125 µm diameter solid-state fast response ion-selective pH and Ca2+ wire-sensors. These flexible microsensors were applied to quantify the real-time change in pH and Ca2+ concentration at hard-to-reach biofilm-biomaterials interface while live biofilms were growing on the Ca2+ releasing smart biomaterials. These smart biomaterials or substrates used in these studies were bioactive glass (BAG) containing resin dental composites that are capable of releasing metal ions (Ca2+) at pH less than 5.5.The newly developed solid-state pH microsensors showed a near-Nernstian response (50 mV/pH) with a fast response time of <500 ms. Similarly, the solid-state Ca2+ microsensors showed a near-Nernstian slope of 28 mV/log[Ca2+] with a linear range of 10 µM to 1 mM along-with response time of less than 0.5 s. Both the pH and Ca2+sensors were then used inside a micro incubator set-up to quantify the real-time pH change at the biofilm-biomaterials interface due to bacterial (S. mutans) metabolism and the corresponding Ca2+ release from the (BAG) containing resins. Our systematic study showed that the lactic acid produced by Streptococcus mutans (Sm) biofilm when exposed to 30 mM sucrose, in BHI/MOPS media at 37°C, caused a pH shift from 7.0 to 5.7 at the biofilm-biomaterial interface. Recent findings of the effect of Ca2+ ions on bacterial growth and metabolism on different compositions of BAG-resin composites will be presented in the conference. This work is supported by the National Institute of Dental and Craniofacial Research (NIDCR) (Grant # R01DE027999).