Liver injury poses a serious threat to human health and
growing
evidence suggests that it is closely associated with a biomarker (peroxynitrite,
ONOO–). Therefore, considering that the relationship
of ONOO– levels with the occurrence and development
of liver injury disease remains a challenge, an urgent need exists
to develop a reliable and robust tool for its visual rapid diagnosis
and assessment. Herein, a two-photon near-infrared (TP-NIR) ratiometric
fluorescent nanoprobe (NTC) based on a fluorescence resonance
energy transfer (FRET) strategy was designed, synthesized, and characterized,
which had the advantages of good water solubility, low background
interference, deep tissue penetration, and high imaging resolution.
Specially, NTC was constructed by self-assembly of an
alkynyl group of a small-molecule fluorescent probe (NR) via click
chemistry grafting onto azide chitosan (natural polymeric nanomaterial).
NR contained acceptor 1 (NIR fluorophore) and donor 3 (D–π–A structure of naphthalimide derivative fluorophore) with outstanding
TP properties that could be activated by ONOO– for
the ratiometric detection of ONOO–. Furthermore,
in the presence of ONOO–, NTC exhibited
a short response time (∼10 s) and high selectivity and sensitivity
toward ONOO– with an excellent detection limit as
low as 15.3 nM over other reactive oxygen/nitrogen species. Notably, NTC has been successfully employed for ONOO– detection and imaging in living HepG2 cells, liver injury mice tissues,
and mice models with satisfactory results. Thus, the construction
of this NTC nanoprobe can provide a robust molecule tool
for enabling early diagnosis and assessment of liver injury in the
future.
For the early diagnosis and effective evaluation of treatment effects of inflammation, a de novo bioanalytical method is urgently needed to monitor the metabolite nitric oxide (NO) associated with inflammatory diseases. However, developing a reliable detection method with excellent water solubility, biocompatibility, long retention time, and blood circulation is still challenging. In this work, we reported for the first time a de novo host−guest self-assembled nanosensor CTA for the quantitative detection and visualization of NO levels in inflammatory models. CTA mainly consists of two parts: (i) an adamantyl-labeled guest small-molecule RN-adH containing a classical response moiety o-phenylenediamine for a chemicalspecific response toward NO and fluorophore rhodamine B with excellent optical properties as an internal reference for self-calibration and (ii) a remarkable water-soluble and biocompatible supramolecular β-cyclodextrin polymer (Poly-β-CD) host. In the presence of NO, the o-phenylenediamine unit was reacted with NO at a low pH value of ∼7.0, accompanied by changes in the intensity of the two emission peaks corrected for each other and the change in fluorescence color of the CTA solution from fuchsia to pink. Furthermore, CTA was an effective tool for NO detection with a fast response time (∼60 s), high selectivity, and sensitivity (LOD: 22.3 nM). Impressively, the CTA nanosensor has successfully achieved the targeted imaging of NO in living inflammatory RAW 264.7 cells and mice models with satisfactory results, which can provide a powerful molecular tool for the visualization and assessment of the occurrence and development of NO-related inflammatory diseases in complex biosystems.
Carbon monoxide (CO) is a vital endogenous gaseous transmitter molecule involved in the regulation of various physiological and pathological processes in living biosystems. In order to investigate the biological function of CO, many technologies have been developed to monitor the level of endogenous CO in biosystems. Among them, the fluorescence detection technology based on the fluorescent probe has the advantages of high sensitivity, excellent selectivity, simple operation, especially non-invasive damage to biological samples, and the possibility of real-time in situ detection, etc., which is considered to be one of the most effective and applicable detection techniques. Therefore, in the last few years, a lot of work has been carried out on the design, synthesis and in vivo fluorescence imaging studies of CO fluorescent probes. Furthermore, using fluorescent probes to detect the changes in CO concentrations in living cells and tissues as well as in organisms has been one of the hot research topics in recent years. However, it is still a challenge to rationally design CO fluorescent probe with excellent optical performance, structural stability, low background interference, good biocompatibility, and excellent water solubility. Therefore, this review focuses on the research progress of CO fluorescent probes in the detection mechanism and biological applications in recent years. However, this popular and leading topic has rarely been summarized comprehensively to date. Thus, the research progress of CO fluorescent probes in recent years is reviewed in terms of their design concept, detection mechanism, and their biological applications. In addition, the relationship between the structure and performance of the probes was also discussed. More significantly, we hope that more excellent optical properties fluorescent probes for gaseous transmitter molecule CO detection and imaging will overcome the current problems of high biotoxicity and limited water solubility in future.
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