A Simple and Low-Cost Electrochemical Immunosensor for Ultrasensitive Determination of Calreticulin Biomarker in Human Serum

An early on time detection of breast cancer significantly affects the treatment process and outcome. Herein, a new label-free impedimetric biosensor is developed to determine the lowest change in the level of calreticulin (CALR), which is a new biomarker of breast carcinoma. The proposed immunosensor is fabricated by using reduced graphene oxide/amino substituted polypyrrole polymer (rGO-PPyNH₂) nanocomposite modified disposable electrode. The anti-CALR antibodies are first attached on the rGO-PPyNH₂ nanocomposite coated electrode through glutaraldehyde crosslinking; the CALR antigens are then immobilized with the addition of CALR antigens to form an immunocomplex on the sensing surface. This immunocomplex induces considerably larger interfacial electron transport resistance (R_ct). The variation in the R_ct has a linear relationship with CALR level in the detection range of 0.025 to 75 pg mL⁻¹, with a detection limit of 10.4 fg mL⁻¹. The suggested biosensor shows high selectivity to CALR, good storage stability (at least 5 weeks) and suitable reproducibility results as shown in quality control chart. The designed immunosensor is utilized to analyze CALR levels in human sera with satisfying results. This immunosensor provides a novel way for the clinical determination of CALR and other cancer biological markers.