An antibody-free bio-layer interferometry biosensor for immunoglobulin G1 detection in human serum by using molecularly imprinted polynorepinephrine

Bio-Layer Interferometry (BLI) has emerged as a versatile technique in affinity-based biosensing, analogous to Surface Plasmon Resonance. BLI enables real-time, label-free detection, and quantification of biomolecular interactions between an immobilized receptor and an analyte in solution. The BLI sensor comprises an optical fiber with an internal reference layer at the end and an external biocompatible layer where biological receptors are immobilized and exposed to the solution. We report the first BLI bioassay using a mimetic receptor based on molecularly imprinted polynorepinephrine (MIPNE) for detecting immunoglobulin G isotype 1 in whole, untreated, human serum. Using BLI fiber optics with different chemical linkers, we compared the analytical performance, with a focus on selectivity against other Ig classes and across the four IgG isotypes. The bioassay displayed the ability to detect IgG1 with excellent analytical parameters both in buffer condition (LOD = 0.54 ± 0.01 μg mL^-1, LOQ = 2.09 ± 0.02 μg mL^-1, _avRSD = 5.3%) and in whole serum (%RE = 0.3%, _avRSD = 3%). These findings highlight the potential of integrating PNE-based molecular imprinting technology with BLI platforms for diverse analytical and diagnostic applications.