A new label-free continuous assay with the ensemble of compound 1 and Arg(6) for trypsin and inhibitor screening was successfully developed by taking advantage of the aggregation-induced emission feature of tetraphenylethene compounds. Both CLSM and DLS studies confirm the formation of the aggregation complex of compound 1 and Arg(6) and disassembly after further addition of trypsin.

Gold nanoparticles (Au-NPs) with negative charges aggregate in the presence of Arg(6) due to electrostatic interactions resulting in the red-shift of the plasmon absorption. But, after incubation of Arg(6) with trypsin the aggregation of Au-NPs can be prohibited. Accordingly, a newly designed-Au-NPs based colorimetric assay method for trypsin activity is established. Trypsin with a concentration as low as 1.6 ng mL(-1) can be assayed with this new colorimetric assay. This colorimetric label-free assay for trypsin can be performed in aqueous solution and both Au-NPs and Arg(6) are easily accessible. Thus, this assay method is useful for screening inhibitors of trypsin.