Fe‐Doped Carbon Dots as NIR‐II Fluorescence Probe for In Vivo Gastric Imaging and pH Detection

Abstract

Carbon dots (CDs) with excellent cytocompatibility, tunable optical properties, and simple synthesis routes are highly desirable for use in optical bioimaging. However, the majority of existing CDs are triggered by ultraviolet/blue light, presenting emissions in the visible/first near‐infrared (NIR‐I) regions, which do not allow deep tissue penetration. Emerging research into CDs with NIR‐II emission in the red region has generated limited designs with poor quantum yield, restricting their in vivo imaging applications due to low penetration depth. Developing novel CDs with NIR‐II emissions and high quantum yield has significant and far‐reaching applications in bioimaging and photodynamic therapy. Here, it is developed for the first time Fe‐doped CDs (Fe‐CDs) exhibiting the excellent linear relationship between 900–1200 nm fluorescence‐emission and pH values, and high quantum yield (QY‐1.27%), which can be used as effective probes for in vivo NIR‐II bioimaging. These findings demonstrate reliable imaging accuracy in tissue as deep as 4 mm, reflecting real‐time pH changes comparable to a standard pH electrode. As an important example application, the Fe‐CDs probe can non‐invasively monitor in vivo gastric pH changes during the digestion process in mice, illustrating its potential applications in aiding imaging‐guided diagnosis of gastric diseases or therapeutic delivery.

Zero-Dimensional Carbon Nanomaterials for Fluorescent Sensing and Imaging

“…Wang developed iron-doped CDs (Fe-CDs) as an effective probe for in vivo NIR-II (900–1200 nm) bioimaging. The probe enables the noninvasive monitoring of gastric pH changes in vivo during digestion in mice, indicating the probe’s application potential for the imaging-guided diagnosis of and therapeutic drug delivery for gastric diseases …”

“…The probe enables the noninvasive monitoring of gastric pH changes in vivo during digestion in mice, indicating the probe's application potential for the imaging-guided diagnosis of and therapeutic drug delivery for gastric diseases. 697 The intrinsic antibacterial mechanism was revealed by Niu et al, who selected iron-doped CDs (Fe-CDs) exhibiting a good antibacterial activity, which can interact with cell membranes, enter bacterial cells through iron transport and infiltration, increase intracellular iron levels, and trigger an increased ROS concentration, leading to the disruption of GSH-dependent antioxidant mechanisms, leakage of the intracellular material, and, ultimately, the inhibition of bacterial growth and death. This result provides important insights into the antibacterial mechanism of Fe-CDs (Figure 19h).…”

Preparation and application of high-brightness red carbon quantum dots for pH and oxidized l-glutathione dual response

“…Compared to blue/green fluorescent CDs, red fluorescent CDs (R-CDs) exhibit a larger penetration depth, lower autofluorescence background, and higher quantum yield. R-CDs have drawn considerable interest because of their potential use in bioimaging, [25][26][27] sensing, 28 optoelectronic conversion, 29 and nanomedicine. [30][31][32] Meanwhile, R-CDs have demonstrated considerable potential for pH sensing because of their sensitivity to pH, good water solubility, and excellent biocompatibility.…”

Molecular‐fusion Synthesis of Bright Green Fluorescent Carbon Dots for Cell Imaging

“…Since the first microscopic discovery of cells by British scientist Robert Hooke in 1665, research on cellular imaging and in vivo imaging has been ongoing for over 300 years [1] . In the 21st century, the development of confocal fluorescence microscopic imaging, has revolutionized biological imaging by enabling the real‐time visualization of biological molecules, cells, and tissues/organs, and various biological processes in three‐dimensions with high sensitivity and resolution [2–4] . At present, fluorescent probes used in imaging primarily consist of organic dyes, rare earth upconversion nanocrystals, and semiconductor quantum dots [5–7] .…”

“…[1] In the 21st century, the development of confocal fluorescence microscopic imaging, has revolutionized biological imaging by enabling the real-time visualization of biological molecules, cells, and tissues/ organs, and various biological processes in three-dimensions with high sensitivity and resolution. [2][3][4] At present, fluorescent probes used in imaging primarily consist of organic dyes, rare earth upconversion nanocrystals, and semiconductor quantum dots. [5][6][7] Organic dyes have limitations such as susceptibility to oxidation and bleaching, specific wavelength excitation requirements, overlapping excitation and emission spectra, low sensitivity, and small Stokes shift.…”