Real-Time and Label-Free Monitoring of Biomolecular Interactions within Complex Biological Media Using a Silica Colloidal Crystal Film

A method capable of real-time and label-free monitoring of biomolecular interactions within whole blood, without any sample separation and label process, is described. This was accomplished using silica colloidal crystal (SCC) films, three-dimensionally ordered silica particle arrays whose interference effect is a function of their optical thickness, as interference-sensitive substrates. Interactions between immunoglobulin G (IgG) and protein A from Staphylococcus aureus (SPA) conjugates with changes in the optical thickness of SCC films were monitored spectroscopically. Successful detection of IgG was achieved in the buffer and whole blood. This system constitutes a simple label-free analysis showing great potential in monitoring interactions between biomolecules in complex biological media.