Optimization of One-Step gold Surface dressing with PEO-probe conjugates for high sensitivity SPR detection of biomolecules

Nowadays, Surface Plasmon Resonance (SPR) has become a powerful tool for studying biomolecular interactions1. SPR allows to transduce a biorecongnition event occurring at the interface between a metal and dielectric medium into a quantitative signal. In this context, grating-based metallic surfaces have been recently described. These surfaces exhibit excellent coupling with surface plamson polaritons, allowing to bypass the conventional prism-coupling2 geometry so that miniaturization and integration into microfuidic andopto-electronic systems becomes easier. Besides the construction geometry, a sensor ecacy also depends on the quality of the sensing surface chemistry, which relies on a) the sens- ing probe, b) the chemistry for its surface anchorage, c) the strategy for minimizing non-specic interactions with non-analyte compounds present in physiological samples. When a surface with non-fouling properties is pursued, a hydrophilic layer is commonly inserted between the probe and the metal. In this case, multi-step procedures for surface functionalisation are generally needed in which the non-fouling lm is added rst, followed by covalent attachment of the probe. However, multi-step procedures are often tedious and not always reproducible. A single step functionalisation strategy would be advisable3, in which the coupling ecacy would not be in uenced by the environment, thus allowing reproducibility among functionalized replicas. In this work we describe the synthesis and use of model PEO derivatives that fulll the above requirements and we characterize their surface dressing process with the nal purpose to provide a general protocol for obtaining functional surface replicas with reproducible properties. Bi-functional PEO (5KDa) derivatives carrying at one end a thiol and at the other end a methoxy or a biotin group were synthesized. An optimized dressing protocol for both at surfaces and sinusoidal gratings was developed through a kinetic study of the surface coat-ing process. The results of sensing experiments using the optimally biotin-PEO functionalized gratings are also shown.