Background: Rheumatoid arthritis is the most common inflammatory autoimmune disease
in the world. Recently new targets for its detection were developed as alternatives to classic
biomarkers, including the M-12 peptide, that mimics carbonic anhydrase III. Thus, the application
of this peptide for the development of new detection devices is attractive.
Objective: Our goal was to construct a modified electrode for immobilization of M-12 peptide and
detection of a rheumatoid arthritis biomarker in serum of patients.
Methods: 3-Hydroxybenzoic acid was electropolymerized onto graphite electrodes, and M-12 peptide
was immobilized by adsorption. Negative and positive serum samples for rheumatoid arthritis
were diluted and applied onto the electrode. Detection was carried in potassium ferrocyanide/
ferricyanide solution by differential pulse voltammetry. Atomic force microscopy and scanning
electron microscopy were used to evaluate electrode surfaces.
Results: Cyclic voltammograms indicated the poly(3-hydroxybenzoic acid) formation and increase
of electroactive area. Immobilization of M-12 probe increased current by 1.2 times, and negative
serum addition caused no suitable difference. However, positive serum showed expressive decrease
in the current signal of about 2.2 times, possibly due to steric hindrance when the anti-CA3 antibody
interacts with the M-12 peptide, decreasing the electron transfer. Microscopies images corroborated
with the electrochemical detection, showing evident changes in the morphology of the
Conclusion: The bioelectrode was able to discriminate positive and negative serum samples of
rheumatoid arthritis by a considerable decrease in the current signal value. Morphological analyses
supported the electrochemical results. Thus, the constructed bioelectrode offers a new platform for
detection of rheumatoid arthritis.