A label‐free photonic crystal biosensor for the assessment of iron status using ferritin

Identification of populations at risk of iron deficiency is of critical concern. We present an application of photonic crystal (PC) biosensors as a diagnostic test for ferritin, a biomarker for iron deficiency. PCs are periodic dielectric surface structures designed to reflect a narrow band of wavelengths when illuminated by a broadband light source. Adsorption of biomolecules causes the reflected wavelength to shift to greater values, providing a simple mechanism for label‐free detection using available detection instruments. PC surface was functionalized with silane for immobilization of primary ferritin antibodies, followed by a blocking step to inactivate remnant silane binding sites. Sensitivity was tested using serial dilutions of human liver ferritin (450 kDa) from 5.0 to 0.15 μg/ml; and a secondary antibody to amplify initial signal. Specificity of the assay was verified by evaluating biosensor binding to BSA. The PC sensor gave a concentration‐dependent response for ferritin (R2= 0.986). When compared to commercial ELISA kit, ferritin response provided comparable limits of detection. Antibodies showed high specificity to ferritin. A 40‐minute assay protocol for label‐free detection of ferritin provided dose‐dependent response in the physiologically relevant concentration range for ferritin in serum; a step towards a simple point‐of‐care assay for iron deficiency diagnosis. Grant Funding Source : College of ACES DNS 20/20