Synthesis of fluorescent α-chymotrypsin A-functionalized gold nanoclusters and their application to blot-based technology for Hg2+ detection

Blot-based technology is widely used in biomedical research, serving as a remarkably efficient platform for biomolecule recognition and detection. In this report, highly fluorescent gold nanoclusters have been synthesized under mild conditions by using a proteolytic enzyme, alpha-chymotrypsin A (CTRA), as both the stabilizing and reducing agents. The synthesized AuNCs@CTRA was characterized by various techniques including UV-vis absorption, fluorescence, X-ray photoelectron spectroscopy and TEM. The fluorescent AuNCs@CTRA is fairly stable and responsive to mercury ions with high selectivity and sensitivity. These protein capped nanoclusters were electrophoresed on an SDS-PAGE gel and transferred to a cellulose membrane. Mercury ions can specifically quench the red fluorescent AuNCs@CTRA band and selectively stop the green band formation on the membrane through inhibition of the peroxidase mimic activity of AuNCs@CTRA toward the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) substrate in a concentration dependent manner. Therefore, using a blot-technology based system, we demonstrated the operation of the AuNCs@CTRA-cellulose hybrid material for mercury ion visual sensing that can be dually read out under UV light (fluorometric) and the naked eye (colorimetric). This approach also has potential for use in other blot-technology based applications.