Electrical immunosensor for detecting fetal red blood cells with potential diagnosis of fetomaternal hemorrhage

Fetomaternal hemorrhage, characterized by the passage of fetal blood into maternal circulation, poses significant risks to both mother and fetus. As it may be diagnosed by quantifying fetal red blood cells in maternal circulation, we developed an immunosensor to detect fetal cells made with a layer-by-layer silk fibroin film and a commercial CD71 monoclonal antibody. Detection was achieved through electrical impedance spectroscopy, allowing discrimination between human umbilical cord blood (UCB) cells and adult peripheral blood (APB) cells from patients and volunteers. Positive samples (UCB) exhibited an average capacitance of 0.34 nF at 1 to 10 Hz, while negative samples (APB) had 0.05 nF. Full agreement was obtained with the detection of fetal red blood cells using flow cytometry. The change in the electrical response was associated with the adsorption of UCB cells on the immunosensor, primarily due to conformational changes in the amide I groups. This reflects the immunoaffinity interactions, as revealed with polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). Cell adsorption was confirmed with optical microscopy images, which indicate possible point-of-care strategies to diagnose FMH with image analysis.