| Plasmonic assays use a phenomena known as plasmon resonance to measure biomolecular interactions in real-time, without the need for molecular labels. Conventional setups typically consist of bulky apparati, and rely on gold chips, micro uidics and sample extraction. These systems are expensive and lack spatial resolution. Therefore, a miniaturized plasmonic biosensor on the end of an optical ber has been developed. This sensor can be used to spatially resolve molecular concentrations, for example in probing hormone excretions levels concentrated locally around immobilized cells. Gold nanoparticles are employed as a cost-eective alternative to metallic chips, which exhibit localized plasmon resonance, and are more sensitive to small molecule interactions than traditional plasmonic assays. An optical model has been developed to quantify sensor response, and shows excellent agreement with measurements of bulk refractive index and protein binding. Nanoparticle surfaces are coated with short chain polyethylene glycols to reduce non-specic adsorption, and optimize the system for targeted capture. Specic interactions are measured between biotin and avidin, a model two-protein system, and then between BSA and AntiBSA, a clinically relevant immunogenic interaction. |
