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An enhanced photonic crystal biosensor‐based immunodiagnostic assay for detection of soluble transferrin receptor as a biomarker of iron deficiency (813.7)

Identification of populations at risk for iron deficiency is of critical concern. Studies on the detection of soluble transferrin receptor (sTfR) using a PC biosensor assay are presented. sTfR (85kDa) is a favorable biomarker of iron status as it is less confounded by inflammation related factors. PCs are periodic dielectric surface structures designed to reflect a narrow band of wavelengths when illuminated by a broadband light source. Adsorption and binding of biomolecules on the PC surface elicits a wavelength shift (PWV) measured in nm. The PC surface of 384‐well microplate was functionalized with silane for immobilization of capture antibodies (Ab), followed by a blocking step. sTfR antigen was added before secondary Ab was dispensed in standard and control wells. Secondary Ab was functionalized with iron‐oxide nanoparticles (30 nm) to enhance signal‐to‐noise ratio. Antigen‐Ab interactions were followed using the BIND system. A sTfR standard curve (200‐5 ng/ml) was created and compared against a commercial ELISA kit. Ab selectivity, limit of detection (LOD), and dose‐response were evaluated (two experiments, n=4/sample). The PC biosensor showed a LOD of 28 ng/ml, a linear response ([PWV=0.8 + 8.4(ug/ml)‐1]; R2=0.98) and limited non‐specific binding against BSA. This study demonstrates the feasibility of the PC biosensor as an immunodiagnostic assay for sTfR detection.