A Colorimetric and Fluorescent Dual-Signal Sensor for Detecting Lipase Activity Based on Inner Filter Effect

We developed a colorimetric and fluorescence dual-signal sensor for detecting lipase activity based on methyl thioglycolate (MT) functionalized gold nanoparticles (MT-AuNPs) and CdS quantum dots (CdS QDs). It is the first time that was developed a dual-signal sensing strategy for lipase activity based on the inner-filter effect (IFE) between MT-AuNPs and CdS QDs. This probe system (MT-AuNPs + CdS QDs) is sensitive and has selective response to the concentration of the lipase, and MT-AuNPs and CdS QDs played as transducer and fluorescer, respectively. The addition of lipase triggered the accumulation and change of color in CdS QDs and MT-AuNPs solution, it also makes the fluorescence intesity of CdS QDs significantly recover. The limit of detection (LOD) was as low as 0.039 μg mL^-1 for colorimetric detection as well as 0.012 μg mL^-1 for the fluorescence method. This method has been successfully used in the detection of commercial lipases. We believe it would open up a new path for the sensitive and high throughput lipase assay using nanobiosensor.