Label-free Electrochemical Immunosensor for Ultrasensitive Detection of KLK4 Using Conjugated Polymer Modified Sensing Platform

In the present research, a label-free impedimetric kallikrein 4 (KLK4) biosensor was fabricated by using a low-cost and disposable indium tin oxide (ITO) electrode and utilized for KLK4 detection in human serum. The ITO electrode was modified first by spin-coating of epoxy-substituted poly(thiophene) (Poly(TEpx)) conjugated polymer and thence anti-KLK4 antibody immobilization via the epoxy ends on the polymer. The specific interaction between the anti-KLK4 antibody present on the working electrode surface and the KLK4 antigen caused increases in the impedimetric response, and the KLK4 antigen was determined in a linear concentration range from 0.025 to 12.5 pg/mL with a detection limit of 7.78 fg/mL. Furthermore, the developed biosensor had acceptable repeatability and reproducibility, long storage stability, and high selectivity to KLK4 antigen. The applicability of the immunosensor was tested in human serum samples and satisfactory results were obtained.