  Selectivity and sensitivity are important figures of merit in the design and
optimization of electrochemical biosensors. The efficiency of the fabricated
immunosensing surface can easily be influenced by several factors, such as
detection limit, non-specific binding, and type of sensing platform. Here, we
demonstrate the effect of macro- and micro-sized planner working electrodes (4
mm and 400 um diameter, respectively) on the electrochemical behavior and the
performance of the developed biosensor to detect human chorionic gonadotropin
(hCG). The fabricated screen-printed sensor was constructed by modifying the
carbon macro- and micro-electrodes with a linker, 1-pyrenebutyric
acid-N-hydroxysuccinimide ester (PANHS) and immobilization of anti-hCG
antibodies to detect specifically the hCG protein. The characterization of the
developed electrodes was performed by cyclic voltammetry (CV) and square wave
voltammetry (SWV). Each immunesensing system has its unique electrochemical
behavior which might be attributed to arrangement of particles on the surface.
However, the smaller surface area of the micro-electrode is found to show
higher sensitivity (1 pg/mL) compared to the macro-electrode sensor with a
lower detection limit of 100 pg/mL. The proposed assay represents a promising
approach that is highly effective for specific detection of an analyte and can
be exploited to target biomarkers for a variety of point-of-care diagnostic
applications.
