Electrochemical biosensor with ceria-polyaniline core shell nano-interface for the detection of carbonic acid in blood.

The normal physiological concentration of carbonic acid in human blood is in the range of 1.08-1.32 mM. However, if the concentration of carbonic acid rises above 3.45 mM, it may lead to respiratory acidosis. In this context, an electrochemical biosensor with CeO2-PANI (polyaniline) core-shell nano-interface was developed for sensing carbonic acid using carbonic anhydrase (CA). CA was immobilized on CeO2-PANI via chitosan on a glassy carbon electrode (GCE/CeO2-PANI/CA/chitosan). The X-ray diffraction (XRD) patterns confirmed the polycrystalline nature of CeO2 and CeO2-PANI nanoparticles. Field emission scanning electron microscopy (FE-SEM) studies showed the aggregation of spherical nanoparticles with size ranging from 37.6 to 47.8 nm and Field emission transmission electron microscopy (FE-TEM) study confirmed the presence of core-shell structure of CeO2-PANI. Immobilization of CA on CeO2-PANI was confirmed by Fourier transform infrared (FT-IR) spectra. Electrochemical studies were carried out with the help of GCE/CeO2-PANI/CA as a working electrode, Ag/AgCl saturated with 0.1 M KCl as a reference electrode and Pt wire as a counter electrode. This biosensor exhibited sensitivity of 696.49 μA cm(-2) mM(-1) with a linear range of 1.32-2.32 mM. It also showed a fast response time of less than 1s, lowest detection limit of 19.4 μM, Michaelis-Menten constant (KM) of 1.8191 mM and dry stability of 96% up to 18 days. The observed results revealed the potential of the modified working electrode with CeO2-PANI core-shell nano-interface for carbonic acid sensing. The developed biosensor can be applied for the real time clinical diagnosis of diseases such as obstructive pulmonary diseases (COPD).