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

• Novelty of the work is the use of CeO2–PANI nano-interface.
• CeO2–PANI interface enhances catalytic activity and the surface area of biosensor.
• Higher immobilization of CA on CeO2–PANI nano-interface.
• Rapid electron transfer between CA and GCE due to CeO2–PANI nano-interface.

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 1 s, 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).

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