Gold–Silver Bimetallic Nanoclusters Protected by Glutathione S-Transferase for Colorimetric Sensing of Oxytetracycline

Abstract

Gold−silver alloy nanoclusters (AuAgNCs) were synthesized, protected by glutathione S-transferase (GST). The asprepared GST-AuAgNCs displayed strong (QY = 15.9%) fluorescence with two emission peaks around 477 and 653 nm under excitation of 395 nm. In this system, both the NC core and the organic shell contributed to the development of a "turn-on" ratiometric fluorescent probe for sensitively and selectively detecting oxytetracycline (OTC). First, the green fluorescence at 477 nm enhanced with the addition of OTC into GST-AuAgNC solution, whereas the red fluorescence at 653 nm remained unchanged. This "turn-on" ratiometric fluorescence may stem from the aggregation-induced emission effect and the reduction of Ag(I). The fluorescence ratio of GST-AuAgNCs displayed good linearity when the concentration of OTC was in the range of 0∼50 μM, and the detection limit was achieved down to 32.66 nM. Second, benefiting from the strong interaction between GST and OTC, the proposed method exhibited good anti-interference toward OTC in comparison with the common ions and natural amino acids. Moreover, the variation of ratiometric fluorescence intensity resulted in the corresponding red-to-green fluorescent color change, which could be employed to establish a simple paperbased analytical method for OTC colorimetric detection. Based on the superiority of high sensitivity and selectivity, as well as good accuracy and biocompatibility, the GST-AuAgNCs were successfully applied for detecting OTC in cells.

Recent advances in aggregation-induced emission (AIE)-based chemosensors for the detection of organic small molecules

“…18). 184 This is due to the reduction of Ag( i ) in B7 's shell structure into Ag(0), and the aggregation of B7 with OTC, which triggers AIE. Consequently, green fluorescence at 477 nm was enhanced over red fluorescence at 653 nm.…”

Metal Nanoclusters in Point-of-Care Sensing and Biosensing Applications

“…The oxytetracycline molecules could decrease the emission at 477 nm but have no apparent effect on emission at 653 nm. This double wavelength emission system is desirable and used in ratiometric detection of the target drug …”

“…This double wavelength emission system is desirable and used in ratiometric detection of the target drug. 546 In addition to the luminescence benefits of bimetallic NCs, combining two atoms is also used for designing other biosensors. 547,548 It has been reported that integrating gold atoms into other NCs can enhance their adsorption ability on the electrode surfaces and improve their stability, detection sensitivity, and charge-transferring ability, which are great benefits in designing electrochemical biosensors.…”

Glutathione S-transferase templated copper nanoclusters as a fluorescent probe for turn-on sensing of chlorotetracycline

“…GST containing tryptophan and tyrosine residues can serve to reduce high-valence metal ions, promoting the fabrication of CuNCs through metal-GST coordination bonds. 27,28 The obtained GST-CuNCs exhibited blue uorescent emission at 400 nm when excited at 325 nm. Meanwhile, the products exhibited exceptional stability under different conditions.…”