Long-term Stable, Binary-phased pH Sensor for Continuous Cell Culture Monitoring
Board Location: #143
Discipline: Technology and Engineering
Subcategory: Biomedical Engineering
Session: 3
Sayre Tillery - University of Oklahoma
Co-Author(s): Jimin Lee, Georgia Institution of Technology, Atlanta, GA. W. Hong Yeo, Georgia Institution of Technology, Atlanta, GA.
This project aims to develop a new bilayer microstructure designed for a pH sensor, optimized for the cell media environment. The microstructure will combine the favorable characteristics of two established electrochemical pH sensor materials: highly sensitive but low-stability iridium oxide (IrOx) and highly stable but low-sensitive polyaniline (PANI) [1, 2]. This bilayer would develop a pH sensor that is sensitive, stable, and well-suited for the challenges of the cell culture media environment. This novel pH sensor would allow for effective cell monitoring which is critical to cell cultivation. The study involved the development of single-layer pH sensors using IrOx and PANI, along with a bilayer pH sensor combining both materials. Single-layer IrOx and PANI deposition was developed by following standard cyclic voltammetry (CV) deposition methods on gold. The PANI/IrOx bilayer was also developed by the CV. After the CV deposition, biocompatible polymers (e.g., Nafion and poly (2-hydroxyethyl methacrylate) (pHEMA)) were drop-coated onto the sensor to enhance stability and reduce cell adhesion.To assess sensitivity, the working electrodes of single-layer PANI, single-layer IrOx, and bilayer PANI/ IrOx were tested against a standard commercial reference electrode in various pH buffers. The sensor repeatability was tested by decreasing pH buffers and then increasing pH buffers. Scanning electron microscope has shown the bilayer as the phased sensor is composed of IrOx -particle-decorated porous PANI. Results from the single-layer IrOx pH sensor were in line with expectations, demonstrating a high sensitivity but poor repeatability due to the later drift [1]. In contrast, PANI exhibited greater stability with limited potential drift in returning pH buffers and a lower sensitivity [2]. The anticipated results of the PANI/IrOx bilayer are expected to combine these results. In the cell culture experiment, the results should indicate a decrease in pH in the media due to acidic waste byproducts from yeast cells.Based on these results, future aspects of the project will involve using these sensors in advanced cell culture media with different cell types. This is crucial because advanced cell culture media may contain reagents or chemicals that could influence the sensor’s performance. If the future results prove promising, this device could be implemented throughout the cell culture to create a 2D mapping of the pH levels within the media, providing valuable insights for cell researchers and biotechnologists.References:[1] J. Yin, et al., “Batch Fabrication of Microminiaturized pH Sensor Integrated With IrOx Film and Solid State Ag/AgCl Electrode for Tap Water Quality Online Detection,” IEEE Sensors Journal, vol. 23, no. 4, pp. 3475-3484, 2023.[2] X. Mei, et al., “Wearable, nanofiber-based microfluidic systems with integrated electrochemical and colorimetric sensing arrays for multiplex sweat analysis,” Chemical Engineering Journal, vol. 454, 2023.
Funder Acknowledgement(s): This project was supported by the Engineering Research Center for Cell Manufacturing Technologies (CMaT) NSF award number EEC-1648035.
Faculty Advisor: W. Hong Yeo, whyeo@gatech.edu
Role: In this project, I was (1) responsible for completing a thorough background review of current pH sensors focusing on their materials and deposition methods, (2) verifying these deposition methods in the single-layer form by fabricating them in the lab, (3) experimenting and combining these single-layer deposition methods to form the bilayer, and (4) test each of these developed pH sensors in a number of different pH buffers. For deposition, I utilized methods like cyclic voltammetry to fabricate these pH sensors by depositing either IrOx, PANI, or IrOx/PANI onto premade gold sensors.