Quantum-Dot Based Lateral Flow Strip Assays for Biomedical Applications

Semiconductor nanoparticles, also known as quantum dots (QDs) exhibit size-tunable, strong and narrow band-edge luminescence. Due to their unique optical, electronics properties and dimensional similarities with biological molecules, QD could allow an integration of nanotechnology and biology, leading to major advances in clinical diagnostics. Lateral flow strip assays based on gold and latex nanoparticles are commonly used in the detection of various biomolecules, but these methods are usually either qualitative or semi-quantitative in nature. QD based lateral flow strip assay can be used for quantitative detection of multiple biomolecules in a single strip. They have the potential in developing rapid, robust, portable multiplex quantitative detection system for many biomolecules including avian influenza virus. We have been successful in developing high quantum yield (as high as 80%) and narrow size distribution (FWMH is less than 25 nm) water soluble CdSe/ZnS QDs. Such QDs were covalently conjugated with specific proteins/antibodies and were employed in the development of later-flow strip assays. To investigate the suitability of the QD based detection system, different levels of Anti-Hemagglutinin antibodies (anti HA, an antibody which specifically binds to the avian influenza viral protein) were deposited on the specially designed lateral flow membranes. Protein G, which can specifically bind to the antibodies, were covalently conjugated with QDs (Emission Maximum 580 nm) and applied to the strip. The Protein G and anti-HA reaction occurred in less than 5 minutes as observed by exciting the strip under a UV lamp. The photoluminescence from the strips were quantitated using a hand-held optical fiber detection system.