Disposable electropolymerized molecularly imprinted electrochemical sensor for determination of breast cancer biomarker CA 15-3 in human serum samples

Initially, a printed electrode was fabricated in a paper substrate using carbon nanotube ink, graphite pencil and silver nanoparticle ink. For that the electrode was modified with gold nanoparticles and a molecularly imprintedpolymer (MIP) using CA 15-3 as target molecule. The Atomic Force Microscopy (AFM) images exhibited the change in the morphology after each electrode modification. The roughness increasedafter the electropolymerization, and decreased after the extraction procedure. Next, slightly increased again associated to the interaction of CA 15-3 and the imprinted sites. Finally, the Fourier Transform Infrared Spectroscopy (FTIR) results suggested the extraction/rebinding of CA 15-3 in the MIP sensor and also indicated that the NIP sample do not have specific cavities for the CA 15-3. In short, under optimized conditions, the CNE/AuNP is incubated with CA 15-3 (40 U mL^-1) for 2 h at 4 °C. Then the electropolymerization was carried out in the potential range of -0.2 to 1.0 V during 20 cycles at scan rate of 50 mV s^-1 using a solution containing 15 mM of oPD. After electropolymerization, the sensor was washed with oxalic acid solution for 2 h, leading to the formation of imprinted cavities. The rebinding process was subsequently constructed for 1 h at 4 °C using CA 15-3 solution. The reproducibility and interference studies showed that the sensor can be reproducible and specific for CA 15-3. Then the sensor was applied in determination of CA 15-3 in samples of serum and saliva. The use in serum presented good recovery, but the application in saliva was not satisfactory. Therefore, the sensor CNE/AuNP/MIP could be used in the determination of CA 15-3 in serum samples.