Ferrous ion (Fe2+) is an important component of hemoglobin and plays a role in transporting O2 to human tissues. If iron deficiency is present, iron deficiency anemia may occur, so it is critical to develop sensitive and accurate methods to detect Fe2+. Herein, a novel luminescence energy transfer (ET) system has been designed for the sensitive detection of Fe2+ by a single-particle enumeration (SPE) method in the near-infrared (NIR) region through combining NIR-to-NIR β-NaGdF4:Yb,Tm@NaYF4 upconversion nanoparticles (UCNPs) and IR-808 dye. IR-808 dye can quench the luminescence of the UCNPs because of the efficient overlap between the absorption spectrum of IR-808 and the emission spectrum of the UCNPs. When Fe2+ and H2O2 are added to the system, the Fenton reaction produces hydroxyl radicals (˙OH). The generated ˙OH reacts with IR-808 and the structure of IR-808 is destroyed. As a result, the ET process is suppressed, causing recovery of the luminescence of the UCNPs, which is reflected as an increase in the number of luminescent particles. Accurate quantification of Fe2+ is achieved by statistically counting the target concentration-dependent luminescent particles. Under the optimal conditions, the linear detection range of Fe2+ is 5–10 000 nM, which is much wider than the ensemble luminescence spectra measurements in bulk solution. Moreover, this strategy can be applied to detection in serum samples with satisfactory results.
Dual-modal imaging by combining magnetic resonance (MR) and near-infrared (NIR) fluorescence can integrate the advantages of high-resolution anatomical imaging with high sensitivity in vivo fluorescent imaging, which is expected to play a significant role in biomedical researches. Here we report a dual-modality imaging probe (NIR/MR-MSNs) fabricated by conjugating NIR fluorescent heptamethine dyes (IR-808) and MR contrast agents (Gd-DTPA) within highly aminated mesoporous silica nanoparticles (MSNs-NH2). The dual-modality imaging probes NIR/MR-MSNs possess a size of ca. 120 nm. The NIR/MR-MSNs show not only near-infrared fluorescence imaging property with an emission peak at 794 nm, but also highly MR relaxivity of 14.54 mM−1 s−1, which is three times more than Gd-DTPA. In vitro experiment reveals high uptake and retention abilities of the nanoprobes, while cell viability assay demonstrates excellent cytocompatibility of the dual-modality imaging probe. After intratumor injection with the NIR/MR-MSNs, MR imaging shows clear anatomical border of the enhanced tumor region while NIR fluorescence exhibits high sensitive tumor detection ability. These intriguing features suggest that this newly developed dual-modality imaging probes have great potential in biomedical imaging.
Zheng Liu,Feng Ren,Hao Zhang,Qiang Yuan,Zhilin Jiang,Hanghang Liu,Qiao Sun,Zhen Li
Rare-earth nanoparticles (RE NPs) with narrow long wavelength emissions have been recently investigated for their potential application for fluorescence imaging in the second near-infrared window (NIR-II). Previously these RE NPs have a very limited application in the diagnosis and treatment of deep-seated tumors such as brain tumors, due to their weak fluorescence in the range of 1300–1700 nm. Herein, we report a significant enhancement of more than 10 times regular emission of NaNdF 4 nanoparticles at 1340 nm wavelength by coating them with an inert layer of NaLuF 4 , followed by sensitizing with a near-infrared dye (IR-808). We deliver these highly bright nanoparticles into the brain by using focused ultrasound to temporarily open the blood-brain barrier (BBB), and then detect the orthotopic glioblastoma by fluorescence imaging at 1340 nm. The images obtained from long wavelength fluorescence ( i.e. 1340 nm) exhibited better resolution and contrast compared to the short wavelength fluorescence ( i.e. 1060 nm). Our study not only provides insights for enhancing often overlooked emissions of rare-earth nanoparticles for NIR-II fluorescence imaging of deep-seated tumors, but also demonstrates great potential of focused ultrasound based technology in delivering nanotheranostic agents.
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