A Highly Sensitive Immunosorbent Assay Based on Biotinylated Graphene Oxide and the Quartz Crystal Microbalance

A high-sensitivity flow-based immunoassay is reported based on a gold-coated quartz crystal microbalance (QCM) chip functionalized directly in the QCM without requiring covalent conjugation steps. Specifically, the irreversible adsorption of a biotinylated graphene oxide-avidin complex followed by loading of a biotinylated capture antibody is applied to avoid more complex conventional surface modification chemistries and enable chip functionalization and sensing all within the QCM instrument. The resulting immunosensors exhibit significantly lower nonspecific protein adsorption and stronger signal for antigen sensing relative to simple avidin-coated sensors. Reproducible quantification of rabbit IgG concentrations ranging from 0.1 ng/mL to 10 μg/mL (6 orders of magnitude) can be achieved depending on the approach used to quantify the binding with simple mass changes used to detect higher concentrations and a horseradish peroxidase-linked detection antibody that converts its substrate to a measurable preci...