Development and application of highly sensitive protein sensor based on spatial conformation of sodium alginate gel-stabilized HE4

To enhance the stability, sensitivity, and selectivity of protein sensors for detecting trace human epididymis protein 4 (HE4), sodium alginate (SA) was employed as a protein carrier in this study. After the gelation of SA, the number of active sites of a protein sensor increased and sensor stability improved, leading to the development of a novel, highly sensitive protein sensor based on the conformation of HE4 immobilized within the SA-gel. The surface of a glassy carbon electrode was modified with SA, where the numerous active sites within SA molecular chains induced and stabilized the spatial conformation of HE4. Under the influence of Ca 2+ , SA contracted to form a gel. Upon the elution of HE4, a three-dimensional cavity structure highly complementary to the spatial conformation of HE4 was formed, resulting in the formation of HE4@SA-gel sensor with excellent selectivity and high sensitivity for HE4. Results demonstrated that changes in the probe molecule signal intensity (Δ i ) were linearly and positively correlated with the logarithm of the HE4 concentration (lg( C , mol/L)) in the range from 1.00 × 10 −13 –3.00 × 10 −9 mol/L, with a limit of detection (LOD) of 2.37 × 10 −14 mol/L (LOD = 3σ/ S ). Comparison results indicated that the prepared HE4@SA-gel sensor exhibited a 12.7-fold increase in sensitivity and an 11.36-fold improvement in selectivity compared with nongelated HE4@SA sensor. When used for detecting HE4 in human serum samples, the prepared HE4@SA-gel sensor achieved a recovery rate of 92.4 %–106.7 %.