Competition assays are suitable for the detection of small molecules. In this detection scheme, the AuNPs-functionalized sensing surface is modified with target analytes. In a sensing event, a sample of free-flowing analytes are premixed with corresponding bioreceptors followed by introduction to the sensing surface. Free-flowing analytes and bound analytes then "compete" for binding with the bioreceptor. Binding of bioreceptor to the bound analyte results in an optical response.
Target: methamphetamine (MA) in urine
Methamphetamine (MA) is a highly addictive stimulant drug. Abuse of this illicit drug can lead to an increased risk of contracting infectious diseases, extreme weight loss, severe dental problems, organ failure, or death.
A known concentration of MA is first functionalized onto the sensing surface. A sample of free-flowing MA with unknown concentration premixed with anti-MA antibodies is then introduced to the sensing surface. Bound MA and free-flowing MA “compete” for the anti-MA antibodies during detection. Binding of anti-MA antibodies to the bound MA results in a refractive index change at the sensing surface and produces an optical response.