Fluorescent Graphitic Carbon Nitride-Based Nanozymes with Peroxidase-Like Activities for Ratiometric Biosensing

Abstract

While breakthroughs in peroxidase-like nanozymes for bioanalysis have been made, most of current nanozyme biosensing systems are based on a single signal output. Such sensing systems could be easily influenced by environmental and personal factors. We envision that nanozyme sensing systems with ratiometric signal outputs would provide more reliable and robust sensing performance. Herein, to construct such ratiometric sensing systems, three fluorescent graphitic carbon nitride (C 3 N 4 )-based nanozymes (i.e., C 3 N 4 −Ru, C 3 N 4 −Cu, and C 3 N 4 −hemin) with excellent peroxidase-like activities were prepared. These fluorescent nanozymes emitted a fluorescence at 438 nm when excited at 385 nm. Interestingly, when o-phenylenediamine (OPD) was catalytically oxidized to oxidized OPD (OPDox) in the presence of H 2 O 2 and nanozymes, the OPDox not only emitted an emerging fluorescence at 564 nm but also quenched the fluorescence at 438 nm of the nanozymes. We therefore employed the ratio of the fluorescent intensity at 564 and 438 nm (i.e., F 564 /F 438 ) as the signal output to construct the ratiometric biosensing systems. First, we used the C 3 N 4 −Ru nanozyme to construct the ratiometric H 2 O 2 sensing system, which showed not only the enhanced robustness but also wider linear range and better sensitivity than most reported H 2 O 2 sensors based on nanozymes. Second, with the assistance of glucose oxidase, glucose can be detected by such ratiometric sensing systems. Third, we used three different C 3 N 4 -based nanozymes to construct ratiometric sensor arrays for the detection and discrimination of five phosphates. This study provides new insights for constructing robust nanozyme biosensing systems.

Progress and Trend on the Regulation Methods for Nanozyme Activity and Its Application

“…The ratio of double emission wavelengths is obtained as a response signal that improves the accuracy of the results by the self-calibration of two different emission wavelengths. The Wei group designed the ratiometric sensing systems by using three kinds of fluorescent C 3 N 4 -based nanozymes such as C 3 N 4 -Ru, C 3 N 4 -Cu, and C 3 N 4 -hemins, which possessed excellent peroxidase mimic catalytic activities [97]. The fluorescent intensity at 438 and 564 nm as the signal output was used to construct ratiometric sensor assays for the determination and discrimination of five phosphates, providing more reliable and robust sensing performance.…”

Delicate Balance of Non‐Covalent Forces Govern the Biocompatibility of Graphitic Carbon Nitride towards Genetic Materials

“…[3][4][5][6][7][8][9][10] Additionally, as a metal-free 2D nanomaterial, g-C 3 N 4 and its functionalized composites have been suggested as potent candidates for biomedical applications such as biosensing, cell imaging, photodynamic therapy, cancer therapy and drug delivery among others. [5,[11][12][13][14][15][16][17][18][19][20][21][22][23][24] Even though the essential condition for in-vitro and in-vivo biomedical applications is the minimization of nanotoxicity, nevertheless, there remain serious safety concerns regarding the introduction of g-C 3 N 4 into cellular environments, since very few studies have been performed to assess the toxicity produced by g-C 3 N 4 at the nanoscale and the modes of interaction between biomolecules and g-C 3 N 4 remain elusive. [3,25,26] To realize the needs of the hour, it is thus imperative to gauge the effects of g-C 3 N 4 on genres of biomolecules either through experiments or through "in-silico" methods, the latter evaluating the hazardous effects through computational identification and real-time visualization of various modes of nanomaterial-biomolecule interactions contributing to nanotoxicity.…”

Emerging tri‐s‐triazine‐based graphitic carbon nitride: A potential signal‐transducing nanostructured material for sensor applications

“…To date, most of g‐C 3 N 4 based sensors are in the early stages of development, and few have been deployed in real‐world applications. [ 13 ] The efficiency of g‐C 3 N 4 remains somewhat limited by its poor light‐harvesting ability and low charge mobilities. To modulate its electronic structure, scientists have modified both its composition and morphology through diverse strategies such as doping, [ 14 ] creating defects, [ 15 ] heterojunctions, [ 16 ] and by creating hybrids with other carbon materials.…”