Development and Characterization of Carbonic Anhydrase-Based CO2 Biosensor for Primary Diagnosis of Respiratory Health

It is a global need to realize noninvasive, simple, rapid, selective, inexpensive, and portable assessment methods for diagnosis of diseases. Enzyme-based bio-sensing system, compared with traditional analytical methods, has all such potential attributes. This paper proposes carbonic anhydrase enzyme (CA) (E.C. 4.2.1.1)-based cost-effective, highly selective, and reproducible CO
₂
biosensing system that can measure CO
₂
concentration (ppm level) in expired breath accurately to give valuable information for assessing the respiratory disorders of the subjects. CA is extracted from spinach leaves and immobilized on an electrode assembly. The assembly generates a sensible electrical signal (mV) when brought in contact with the aqueous CO
₂
. The sensor characterizes a linear response from 160-2677 ppm of CO
₂
concentration dissolved in water, good sensitivity (~0.132mV/ppm) with excellent fast response time within 12s. The features include repeatability, shelf life (~5 months), re-usability (~20 times), and selective responsiveness to the CO
₂
molecules in the exhaled breath. The feasibility for the use of the biosensor in a suitable setup for home-based monitoring of CO
₂
in exhaled breath has been proposed and justified. The device showed a good correlation between the results obtained from the sensor and established clinical test.