Antibodyantigenic peptide interactions monitored by

This work reports on a complementary use of surface plasmon resonance (SPR) and quartz crystal microbalance with dissipation monitoring
(QCM-D) technologies to study interactions between a peptide antigen and polyclonal antibodies, in an experimental format suitable for diagnostic
assays of autoimmune diseases. In the chosen model, a synthetic peptide from the juxtamembrane region of IA-2 (a type 1 diabetes associated
antigen) was immobilized by an optimized chemical protocol applicable to both BIACORE and QCM-D sensors. A thorough study of the peptide
immobilization was performed to optimize the signal-to-noise ratio using mixed self-assembled monolayers (SAM) on a gold surface. Introduction
of polyethylene glycol (EG6) chains into mixed SAM layers and addition of an anionic surfactant to the human serum reduced non-specific binding
without modifying the viscoelasticity properties of the layer. Under our conditions, the antibody SPR detection limit was determined to be 0.2nM
in diluted human serum. This value is in agreement with the reported rank distribution of IA-2 antibodies in diabetic patient sera. Label-free and
real-time technologies such as SPR and/or QCM-D could be precious tools in future diagnostic assays.