Use of quantum dots as mass and fluorescence labels in microarray biosensing

In this work, we demonstrate the efficacy of a Quantum Dot (QD) mass label strategy to enhance sensitivity in an interferometric technique called interferometric reflectance imaging sensor (IRIS). This biomass detection platform confers the advantage of absolute mass quantification and lower cost, easily implementable equipment. We discuss the advantages of this label when used in parallel with fluorescence detection. QDs represent a unique opportunity to improve sensitivity in both mass-label detection methods due to their large detectable mass, as well as in fluorescence detection, as they fluoresce without quenching. Streptavidin-conjugated QDs (SA-QDs) have been investigated as such a dual-role probe because of their large shape and mass, their 655 nm emission peak for fluorescent detection platforms, and their robust insensitivity to photobleaching and quenching. In particular we explored their dual role in a microarrays immunoassay designed to detect antibodies against p-lactoglobulin, a common milk allergen. The SA-QDs formed a large detectable monolayer of 6.2 ng/mm(2) in the saturation conditions, a mass signal corroborated by previous studies by Platt et al. [1].