Characterisation of pH and Glucose Sensors for use in Cell Culture

Abstract

The long term monitoring of cell cultures, to study their dynamic nature is important, although devices capable of doing this aren’t available. Primiarily the reason for this is the bio-compatability of the devices and this refers to both the devices’ compatibility with the culture as well as its compatibility with the device. Glucose sensors fabricated in electropolymerised poly(phenol) were used for the study. The reproducibility of these devices was checked to assess their viability for large scale deployment. It was found that the intra–batch variation was within the norms of experimental error, although the inter–batch variation was significant. This is a feature that is inherent to hand made devices and some methods to mitigate this are discussed. The surface characterisation of the sensors showed that the polymer and enzyme sit mutually exclusive to each other on the surface. Using cyclic voltammetry, with ferrocyanide as the probe molecule, it was confirmed that the diffusion profile to the surface of the sensor was semi-infinite planar and that the electrochemistry was quasi-reversible. Infra–red and Raman spectroscopy and scanning electrochemical microscopy were used as well to study the films’ morphology. The sensors were not toxic to 3T3 cell cultures, as the yield and cell viability were consistent with those of the control cultures. It was also seen that the initial degradation of the sensors’ response was not entirely due to the loss in enzyme activity. Non-polarised sensors showed a decrease in sensitivity to glucose and a threshold concentration ca. 3 mM below which they showed no response to glucose, when they were removed from the culture. These effects were not seen before the sensors were placed in the culture and in protein free media, they were partially reversed over time.