Telomerase has long been considered as a biomarker for cancer diagnosis and a therapeutic target for drug discovery. Detecting telomerase activity in vivo could provide more direct information of tumor progression and response to drug treatment, which, however, is hampered by the lack of an effective probe that can generate an output signal without a tissue penetration depth limit. In this study, using the principle of distance-dependent magnetic resonance tuning, we constructed a telomerase-activated magnetic resonance imaging probe (TAMP) by connecting superparamagnetic ferroferric oxide nanoparticles (SPFONs) and paramagnetic Gd-DOTA (Gd(III) 1,4,7,10tetraazacyclododecane-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) complexes via telomerase-responsive DNA motifs. Upon telomerase-catalyzed extension of the primer in TAMP, Gd-DOTA-conjugated oligonucleotides can be liberated from the surface of SPFONs through a DNA strand displacement reaction, restoring the T 1 signal of the Gd-DOTA for a direct readout of the telomerase activity. Here we show that, by tracking telomerase activity, this probe provides consistent monitoring of tumor growth kinetics during progression and in response to drug treatment and enables in situ screening of telomerase inhibitors in whole-animal models. This study provides an alternative toolkit for cancer diagnosis, treatment response assessment, and anticancer drug screening.

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Telomerase represents an essential molecular machinery for tumor occurrence and progression and a potential therapeutic target for cancer treatment. Sensitive and reliable analysis of telomerase activity is of significant importance for the diagnosis and treatment of cancer. In this study, we developed a telomerase-activated nanoscintillator probe for deep-tissue and background-free imaging of telomerase activity and screening telomerase inhibitors in tumor-bearing living mice models. The probe was constructed by modifying lanthanide-doped nanoscintillators with aptamer-containing DNA anchor strands which hybridized with quencher labelled–oligonucleotide strands and telomerase primers. The X-ray-induced fluorescence of the probe was quenched originally but turned on upon telomerase-catalyzed extension of the primer. Benefiting from exceptional tissue penetrating properties and negligible autofluorescence of X-ray excitation, this probe enabled direct detection of telomerase activity in vivo via fluorescence imaging. Furthermore, with the direct, readable fluorescent signals, the probe enabled the screening of telomerase inhibitors in living cells and whole-animal models in the native states of telomerase. This strategy would inspire the development of low autofluorescence and deep tissue bioimaging probes for disease diagnosis and drug development in high-level living settings.

Using the cross-matched data of Gaia EDR3 and the Two Micron All Sky Survey Point Source Catalog, a sample of RC stars with parallax accuracies better than 20% is identified and used to reveal the nearby spiral pattern traced by old stars. As shown in the overdensity distribution of RC stars, there is an arc-like feature extending from l ∼ 90° to ∼243°, which passes close to the Sun. This feature is probably an arm segment traced by old stars, indicating the galaxy potential in the vicinity of the Sun. With a comparison to the spiral arms depicted by young objects, we found that there are considerable offsets between the two different components of the Galactic spiral arms. The spiral arm traced by RC stars tends to have a larger pitch angle, and hence a more loosely wound pattern.