18.3.4 Electronic Tongue

As per the IUPAC technical report, “The electronic tongue is an analytical instrument

comprising an array of nonspecific, low-selective, chemical sensors with high stability

and cross-sensitivity to different species in solution and an appropriate method of PARC

and/or multivariate calibration for data processing.” A MIP-based electronic tongue for

certain phenols was fabricated using chemometrics and an artificial neural network

(ANN) [51,52]. An electrically conductive hybrid hydrogel was fabricated with a com­

posite of PPy and alginate and for human mesenchymal stem cell (hMSC) culture [51].

The conductive hybrid hydrogels may be used as a smart interface to stimulate stem cells

via the effects of electrical and mechanical signals. The increase in Py and oxidant con­

centration showed a transition in the color of hydrogels from brown to black and a clear

solution obtained after PPy polymerization. In cell culture studies, the results figured out

that conductive hybrid hydrogel swells interacted with hMSCs as the hMSCs derived into

larger and more elongated shapes when other substrates were used. An electrochemical

biosensor using hydrogel-based MIPs for protein detection was used [52]. The coupling of

pattern recognition techniques via principal component analysis (PCA) resulted in un­

ique protein fingerprints for corresponding protein templates, allowing for MIP-based

protein profiling. This PCA-coupled method was efficient for discriminating four proteins

(BHb, Mb, BSA, and Cyt C), confirming that glassy carbon (GC) electrodes modified with

MIP film could be used as a fast sensor to segregate between different kinds of proteins.

18.4 Conclusions and Perspectives

In conclusion, conductive hydrogels seem to be an integral part of bioelectronic devices.

They are the coupling agent between the bionic and abionic constituents, playing the role

of a perfect hinge between the two widely different fields, coupling them together almost

perfectly. Although efforts have been made to design adaptable gel networks with higher

flexibility, better biocompatibility, and simultaneously transducing the signal(s) from

bionic system to abionic sectors for the sake of monitoring the biology, understanding at

molecular level details are lacking. Such understandings will pave the way for eluci­

dating the molecular biology of diseases threatening society today. The ignorance lying in

our complete understanding of nature/biology forbids us to fabricate foolproof devices.

Chemistry can tailor the hydrogels and a more synergistic approach will prove to be a

boon, facilitating the transfer of these devices to the common man of society. Conductive

hydrogels are on the verge of reaching the diagnostics market and contributing to

“theranostics” more efficiently, spreading to other untouched sectors also.

References

1. M. Bresadola, Medicine and science in the life of Luigi Galvani (1737–1798). Brain Research

Bulletin 46 (1998) 367–380.

2. K. Gilmore, A.J. Hodgson, B. Luan, C. Small, G. Wallace, Preparation of hydrogel/con­

ducting polymer composites. Polym Gels Networks 2 (1994) 135–143.

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