(700c) Multiplexed Detection of Protein Biomarkers Using Recognitive Polymers in a Localized Surface Plasmon Resonance Sensor Array

Synthetic polymers have been designed to differentially bind proteins by incorporating functional groups that form non-covalent interactions with specific residues on protein surfaces. Such recognitive polymers can be synthesized on the surface of nanomaterials to develop receptors with built-in signal transduction. For example, the localized surface plasmon resonance (LSPR) of noble metal nanomaterials is sensitive to changes in local refractive index and can be exploited to detect molecular binding events near the nanomaterial surfaces. In particular, nanomaterials with high aspect ratios, such as gold nanoshells (AuNSs), have enhanced LSPR sensitivity compared to colloidal gold. Here, we synthesized recognitive polymers on AuNSs and take advantage of their enhanced LSPR sensitivity for detecting protein biomarkers of Sjögrenâ??s syndrome.

Crosslinked copolymers of N-isopropylacrylamide (NIPAM) and methacrylic acid (MAA) (poly(NIPAM-co-MAA)) were synthesized on surface modified AuNSs via precipitation polymerization. After synthesis, additional functional groups were introduced into the polymer shell via post-synthesis modifications to generate a set of polymers with varied recognition properties. Absorbance spectra were measured to detect the LSPR response of each polymer-AuNS composite to increasing concentrations of protein biomarkers. Bare AuNSs showed negligible LSPR shifts upon incubation with any protein. On the other hand, recognitive polymer coated AuNSs exhibited concentration dependent red-shifts in LSPR wavelength upon incubation with proteins for which the polymer had a high binding affinity, but no shifts were observed for low affinity polymer-protein combinations. The polymer-AuNS composites that exhibited the most distinctive recognition profiles were combined in a sensor array that enables multiplexed detection of Sjögrenâ??s syndrome biomarkers.