Dual-emission copper nanoclusters–based ratiometric fluorescent probe for intracellular detection of hydroxyl and superoxide anion species

Abstract

A fluorescent nanoprobe based on copper nanoclusters (CuNCs) has been developed for ratiometric detection of hydroxyl radicals (• OH) and superoxide anion radicals (O 2 •−). Two differently luminescent CuNCs, namely cyan-emissive poly(methacrylic acid)-protected copper nanoclusters (PCuNCs) and orange-emissive bovine serum albumin-protected CuNCs (BCuNCs), were conjugated to obtain a hybrid, dual-emission nanoprobe (PCuNCs-BCuNCs) with the corresponding peaks at 445 nm and 652 nm at an excitation wavelength of 360 nm. In particular, the fluorescence peak at 445 nm gradually enhanced with the incremental addition of • OH and O 2 •−. However, the fluorescence emission at 652 nm was greatly quenched in the presence of • OH, while in case of O 2 •− , the fluorescence intensity remained constant. The differential response of the PCuNCs-BCuNCs towards • OH and O 2 •− formed the basis of ratiometric detection. Under optimal conditions, the PCuNCs-BCuNCs exhibited good sensitivity and linearity towards • OH and O 2 •− with limits of detection of 0.15 μM and 1.8 μM, respectively. Moreover, the nanoprobe exhibited high selectivity for • OH and O 2 •− over other potential ROS interferences. Besides, PCuNCs-BCuNCs were eventually applied for qualitative and quantitative ratiometric assessment of intracellular • OH and O 2 •− in L-132 cells. Therefore, this strategy unveils a new potential for copper nanocluster-based sensing of ROS.

Microwave-assisted synthesis of green fluorescent copper nanoclusters: a novel approach for sensing of hydroxyl radicals and pyrophosphate ions via a “turn-off–on” mechanism

“…The correlation coefficient (R 2 ) is fairly good (R 2 = 0.993), favorable to attain an impressive LOD of 0.68 nM for PPi. The analytical efficiency of the coffee-Tryp-CuNCs-based fluorescence sensor is compared to the reported approaches [38][39][40][41][42][43][44][45][46][47][48][49][50][51] for detecting of OH and PPi, as shown in Tables 1 and 2.…”

The Multifarious Applications of Copper Nanoclusters in Biosensing and Bioimaging and Their Translational Role in Early Disease Detection

“…Nonetheless, fluorescent sensors dependent on the single-color emission signals are subjected to interference with the analyte. Ratiometric fluorescent probes also possess robust anti-interference abilities since they offer innate auto-adjustment for more reliable quantification by computing the intensity ratio of two fluorescent signals [ 56 , 57 ]. To date, various fluorescent nanomaterial probes have been utilized to construct efficient ratiometric sensing platforms, including semiconductor QDs [ 58 , 59 , 60 ], carbon dots [ 17 , 61 ], organic polymers, metal nanoclusters and small molecules.…”

Multichannel Fluorescence Microscopy: Advantages of Going beyond a Single Emission

“…However, as explained in Section 2, it is advantageous to use a single probe with multiple emissions. This strategy has been followed to characterize intracellular pH, ion concentration, or reactive oxygen species (ROS) production using ratiometric sensors based on fluorescent organic compounds, [42,44,68] luminescent particles, [69][70][71][72][73][74] and hybrid structures. [75][76][77][78][79] In addition, targeting ability can be achieved by combining the sensor with a specific cellular label or tagging molecule, whose emission can also be used for ratiometric sensing.…”