A rapid, whole blood immunoassay using metal nanoshells

Using metal nanoshells as an immunoassay substrate, we describe an immunoassay capable of detecting blood borne analyte on the order of minutes. Near infrared resonant gold nanoshells were labeled with antibodies specific to rabbit IgG analyte. The antibody-nanoshell conjugates were detectable via near infrared photometry in solution with saline, serum, and whole blood. Addition of analyte induced aggregation of antibody-nanoshell conjugates, causing a decrease in the original nanoshell near infrared resonance. Aggregation proceeded in a concentration dependent fasion in all three mediums (saline, serum, whole blood), permitting quantitative detection of analyte within 10-30 minutes and sensitivities <1 ng/mL.