Microwave-Mediated Synthesis of Near-Infrared-Emitting Silver Ion-Modified Gold Nanoclusters for Ratiometric Sensing of Hydrosulfide in Environmental Water and Hydrogen Sulfide in Live Cells

Abstract

Protein-stabilized gold nanoclusters (AuNCs) are intensively used in nanoscale biological systems and biosensors. However, protein-stabilized AuNCs that exhibit an emission peak at the first near-infrared (NIR) window (700–900 nm) have rarely been explored. Herein, we present a rapid microwave synthetic approach for developing NIR-emissive AuNCs (named NIR750-AuNCs) through pH-mediated NaBH4 reduction of HAuCl4 in the presence of lysozyme as a template. The NIR750-AuNCs exhibited emission peaks at 750 nm with luminescence lifetimes of 1.0 μs and quantum yields (QY) of 4.9%. The incorporation of Ag­(I) into NIR750-AuNCs [named NIR750-AuNCs@Ag­(I)] efficiently enhanced their QY (13.7%) and luminescence lifetime (1.9 μs) due to the coordination of the Ag­(I) ions with electron-rich residues of the lysozyme shell that mediates the ligand-to-metal–metal charge transfer (LMMCT) process. Additionally, this coordination reaction enables NIR750-AuNCs@Ag­(I) to exhibit excellent resistance to photobleaching. The lysozyme shell allowed the conjugation of NIR750-AuNCs@Ag­(I) with FITC molecules. As a result, the as-made FITC/NIR750-AuNCs@Ag­(I) display two well-resolved emission peaks at 525 and 750 nm with almost equal intensities. These outstanding features allowed the use of FITC/NIR750-AuNCs@Ag­(I) for ratiometric sensing of 5–25 μM NaHS in environmental samples with an excellent reproducibility (relative standard deviation of intensity ratio (<2.5%), satisfactory selectivity, and acceptable recovery (94.4%–101.9%). The sensing mechanism of FITC/NIR750-AuNCs@Ag­(I) is attributable to HS–-triggered removal of Ag­(I) from the electron-rich residues of the lysozyme shell. Also, FITC/NIR750-AuNCs@Ag­(I) were implemented for ratiometric imaging of exogenous and endogenous H2S in live cells. This work demonstrates the synthesis of protein-stabilized AuNCs with an emission maximum of 750 nm, paving the road to designing NIR-emitting AuNCs.

Preparation and evaluation of bismuth sulfide and magnetite‐based theranostic nanohybrid as drug carrier and dual MRI/CT contrast agent

“…[ 33 ] NaOH was used for denaturation and biomineralization of the BSA. [ 33,35 ] (II) Preparation of the magnetite/bismuth hybrid nanoparticle, Bi 2 S 3 @BSA‐Fe 3 O 4 : In this step, Fe 3 O 4 nanoparticles were synthesized via co‐precipitation method in the presence of pre‐synthesized Bi 2 S 3 @BSA nanoparticles. Nano sized magnetite was synthesized to form the magnetite/bismuth hybrid nanoparticle, Bi 2 S 3 @BSA‐Fe 3 O 4 .…”

Gold nanocluster composites: preparation strategies, optical and catalytic properties, and applications

“…16 For example, composites composed of AuNCs and other fluorescent materials show ratiometric fluorescence, which is suitable for the fluorescence detection. 17 When clustered AuNCs were confined on metal-organic frameworks, the fluorescence lifetime and intensity of the composites were significantly increased owing to the restricted intramolecular rotation of AuNCs. 18 AuNC composites have attracted increasing attention owing to the advantages of their various properties.…”

N-Cholyl d-Penicilamine Micelles Templated Red Light-Emitting Silver Nanoclusters: Fluorometric Sensor for S2– Ions and Bioimaging Application Using Zebrafish Model

“…In these contacts, the NCPA-templated AgNCs were used as fluorescent probes for the sensing of sulfide (S 2– ) ions. Among the various anions, the S 2– ion is one of the environmentally important toxins that are released as side products of several human industrial activities, such as tanneries, cosmetics, petroleum and coal industries, pulp manufacturing and food processing plants. − The discharge of S 2– ions beyond the pollution limits affect the ecological environment and pollute the groundwater leading to various diseases such as Alzheimer’s, Down’s syndrome, diabetes, and liver cirrhosis. , Recently, fluorescent MNCs have been used as a probe material for the sensing of sulfide ions. − Literature reports showing that red and NIR emitting noble-metal NCs are extensively used as potential fluorescent probes for bioimaging applications, because of their distinct advantages, such as reduced auto fluorescence background, penetration depth in vivo, with reduced damage to tissue cells and higher resolution. , Since the synthesized red-emitting NCPA-templated AgNCs possess good water solubility, high photostability, and a large Stokes shift, here we have demonstrated the cellular and molecular level of toxicity and live bioimaging studies using zebrafish ( Danio rerio ) as an in vivo vertebrate model system. Zebrafish has played a growing role in scientific research in the last few decades.…”