A Ratiometric Upconversion Nanoprobe for Detection of HNO Based on Luminescence Resonance Energy Transfer

Abstract

Nitroxyl (HNO), produced by nitric oxide (NO) with one-electron reduction and protonation, has recently received substantial interest due to its important roles in various biological functions and pharmacological activities. Research indicates that HNO also has many potential pharmacological applications for different diseases. Therefore, the development of a reliable method for HNO assay in biosystems is highly desired. Ratiometric fluorescent probes show significant advantages over traditional "turn-on" ones, because simultaneous measurement of two emission signals can provide a built-in correction and thus minimize the inaccurate fluorescence signal readouts. As far as we know, there is no ratiometric fluorescent probe for HNO detection based on upconversion nanoparticles (UCNPs). Herein, a ratiometric nanoprobe for HNO assay was constructed based on the luminescence resonance energy transfer (LRET) principle by using UCNPs with a core-shell structure (NaYbF 4 :30%Gd@NaYF 4 :2%Yb:1%Tm) as the energy donor and an organic dye Fl-TP as the potential energy acceptor. The oleate-coated UCNPs (OA-UCNPs) and Fl-TP were assembled through hydrophobic interaction to construct the upconversion nanoprobe (termed as Fl-TP-UCNPs). Because of the ring-closed form, Fl-TP displayed weak absorption and was non-fluorescent, which blocked the LRET process. After reaction with HNO, the triphenylphosphine moiety left and released Fl-HNO with the fluorescent ring-open form. Fl-HNO showed strong absorption in the range of 400～500 nm, which completely overlapped with the blue luminescence of UCNPs and triggered the LRET process between UCNPs and Fl-HNO. Thus, the luminescence from UCNPs around 480 nm decreased and the emission from Fl-HNO around 525 nm increased with a [HNO]-dependent manner. The ratiometric luminescence intensity F 525 nm /F 480 nm showed a good linear relationship (R 2 ＝0.9914) to the logarithm of AS (Angeli's salt, a generally used HNO donor) concentration in the range of 3～ 100 μmol•L -1 and the limit of detection was 23.4 nmol•L -1 . The excellent sensitivity, stability, selectivity and low cytotoxicity endow Fl-TP-UCNPs with the superior capability for HNO assay in vitro and in vivo. We found that Fl-TP-UCNPs probe is appropriate for monitoring HNO in living cells as well as imaging HNO in liver tissues. This probe may be a powerful tool for HNO assay in various physiological processes.

Ratiometric upconversion luminescence nanoprobes from construction to sensing, imaging, and phototherapeutics

“…For convenient mastering, previous studies on ratiometric UCL nanoprobes are appropriately classified and regularly arranged based on specific targets and characters, including temperature (Table 1), 28–84 pH (Table 2), 85–99 inorganic anions, cations, free radicals (Table 3), 100–126 gases, small common molecules, biological small molecules and biomacromolecules (Table 4). 127–162 For a better understanding of construction strategies, the following sections provide principle construction methods and ratiometric dual-signal modes of ratiometric UCL nanoprobes by discussing the state-of-the-art related studies.…”

“…Thus, a unique type of ratiometric UCL nanoprobes can be constructed by plotting a functioning relationship of the “ U / F ” or “ F / U ” ratio vs. target concentration (or the condition). 88–90,93–95,99,106,140,149,155,159,162…”

“…Particularly, FRET (LRET) has been largely involved during the sensing process of ratiometric UCL nanoprobes toward the effective detection of specific targets. 86,88,89,91,93,98,101,105,111,117,118,121,123,126–131,133,135,136,141–143,146,149–152,154,156–159 When UCL emission spectrum of a phosphor (from nanoprobe systems) as the energy donor can efficiently (larger-area) overlap with the absorption spectrum of another component (from nanoprobe systems or modified derivatives in combination with targets) as the energy receptor, NIR light excitation of phosphor donor will induce the receptor to produce luminescence, and meanwhile, UCL intensity of the donor decreases. Generally, the efficiency of FRET or LRET is closely associated with the spatial distance between donors and receptors.…”

“…Ratiometric UCL nanoprobe systems have exhibited great prospects for efficient sensing and detection of various molecules in previous studies, such as gases (CO, 127 NO, 128–130 and O 2 195 ), small molecules (H 2 O 2 , 131–135 N 2 H 2 , 136 HNO, 149 HOCl, 111 and phosgene 158 ), biomolecules (glutathione, 135 uric acid, 137 ascorbic acid, 138,139 cysteine, 140 arginine, 143 spermine, 144 and enzyme substrate 197 ), biomacromolecules (miRNA, 156 cytochrome c , 155 myoglobin, 198 flavin mononucleotide, 201 receptor protein, 201 alkaline phosphatase, 200 thymidine kinase 1, 152 metalloproteinases, 153,154 caspase-3, 159 phospholipase D, 160 and extracellular cancer-specific biomarker PTK-7 157 ), and drug or other molecules (doxorubicin, 141,142 camptothecin, 142 diethyl chlorophosphite, 150,151 dimethoate, 150 furfural, 145 melamine, 163 amaranth, 148 Rose Bengal, 146 perfluorooctane sulfonate, 147 and explosives 199 ) (Table 4). Most of the nanoprobe systems consist of upconverting luminescent materials (lanthanide-doped UCNPs and derivatives) that generally undergo functional modifications with organic molecules, inorganic materials, and organic–inorganic composites to form the core@shell, hollow, porous, complex, hybrid, mixture, assembly, engineering, and multifunctional complicated structures.…”

“…Most of the nanoprobe systems consist of upconverting luminescent materials (lanthanide-doped UCNPs and derivatives) that generally undergo functional modifications with organic molecules, inorganic materials, and organic–inorganic composites to form the core@shell, hollow, porous, complex, hybrid, mixture, assembly, engineering, and multifunctional complicated structures. 127–163,195–201 Major molecule sensing mechanisms are target-induced occurrence or suppression of the LRET (FRET) process, IFE, PET, etc . The sensing process often refers to the interactions of targets with nanoprobe systems, referring to the target-sensitive luminescence, absorption-caused quenching, aggregation-induced quenching, structural decomposition and recombination, target-responsive drug release, spiro-ring closure, opening reactions, surface molecularly imprinted structure regulation, backbone/peptide/enzymatic cleavage, enzyme cascade signal amplification, etc .…”