Quantitation: Competition Assays
Competition assays are suitable for the detection of small molecules. In this detection approach, the AuNPs-functionalized sensing surface is modified with target analytes. During a sensing event, a sample containing free-flowing analytes is premixed with corresponding bio-receptors and subsequently introduced to the sensing surface. The free-flowing analytes and the bound analytes then engage in a competitive interaction for binding to the bioreceptor. The binding of bio-receptor to the bound analyte results in an optical response, which can then be used to detect and estimate the concentration of the target analyte in the sample.

定量：競爭檢測法
競爭檢測法適用於小分子的檢測。在這種檢測方式中，帶有金奈米粒子(AuNPs)的感測表面會先與目標分析物進行修飾。檢測時，包含游離分析物的樣品會先與對應的受器混合，然後再引入至感測表面。游離分析物和固定分析物會彼此「競爭」與受器結合，而受體與固定分析物的結合會產生光學反應，可進而偵測並推算樣品中待測物的濃度。

Target: methamphetamine (MA) in urine
Methamphetamine (MA) is a highly addictive stimulant drug. The abuse of this illicit drug can lead to harmful effects on the central nervous system, extreme weight loss, severe dental problems, organ failure, or death.

​​​​​​​目標：尿液中的甲基苯丙胺(MA)
甲基安非他命（MA）是一種高度成癮的興奮劑，濫用這種非法藥物可導致中樞神經系統的危害、體重極度下降、嚴重的口腔問題、器官衰竭或死亡。

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.

​​​​​​​首先將已知濃度的甲基安非他命（MA）固定到感測表面上，然後將含有未知濃度的游離MA的樣本與抗MA抗體預先混合，並引入到感測表面。在檢測過程中，固定的MA和游離的MA將競爭著與抗MA抗體結合，抗MA抗體與固定的MA結合後會導致感測表面的折射率變化，產生光學反應。