Colorimetric Biosensor for Detection of Cancer Biomarker by Au Nanoparticle-Decorated Bi₂Se₃ Nanosheets

The colorimetric biosensors have attracted intensive interest; however, their relatively low sensitivity limits their applications in clinic detection. Herein, we develop an effective colorimetric biosensor based on highly catalytic active Au nanoparticle-decorated Bi₂Se₃ (Au/Bi₂Se₃) nanosheets. Au/Bi₂Se₃ nanosheets are facilely synthesized by simply sonicating Au precursor with the as-synthesized Bi₂Se₃ nanosheets in aqueous solution. Because of the low redox potential and typical topological insulating properties, Bi₂Se₃ nanosheets is capable of providing and accumulating electrons on its surface. Such unique properties of Bi₂Se₃ nanosheets contribute to strong synergistic catalytic effects with Au nanoparticles, particularly when Au/Bi₂Se₃ nanosheets are utilized for catalyzing the reduction of 4-nitrophenol (4-NP) by NaBH₄ (K = 386.67 s^-1g^-1). The excellent catalytic activity of Au/Bi₂Se₃ nanosheets can be "switched off" upon treatment of antibody of cancer biomarker such as anticarcinoembryonic antibody (anti-CEA). Addition of the corresponding antigen such as cancer biomarker carcinoembryonic antibody (CEA) can successively help "switch on" the catalytic activity of Au/Bi₂Se₃ nanosheets, where the resuming degree however depends on the antigen concentration. This cancer biomarker depended catalytic behavior therefore allows Au/Bi₂Se₃ nanosheets to be employed as a colorimetric sensor for detection of a particular cancer biomarker, for the reduction of 4-nitrophenol (4-NP) by NaBH₄ itself involves apparent color change. The sensor shows high sensitivity and selectivity for the cancer biomarker, even for a concentration as low as 160 pg/mL for CEA, which fully satisfies the requirement for real clinical applications. The developed colorimetric sensor shows good generality for detection of different types of cancer biomarkers, such as α-fetoprotein (AFP) and prostate-specific antigen (PSA). Furthermore, real clinic sample analyzing result shows that the prepared biosensor is efficient for detection of CEA, providing an alternative method in cancer diagnosis.