β-Galactosidase-Activatable Fluorescent and Photoacoustic Imaging of Tumor Senescence

Abstract

β-Galactosidase (β-gal) is the gold standard marker of cellular senescence, which is linked with various age-related diseases. Therefore, it is essential to develop more excellent probes that can realtime monitor β-gal activity in cellular senescence in vivo. Fluorescent/ photoacoustic (FL/PA) dual-modal imaging possesses excellent sensitivity and spatial resolution. To our knowledge, there has been no tumor-targeted FL/PA probe to image cellular senescence by monitoring the activity of β-gal in vivo. Therefore, we developed a tumor-targeted FL/PA probe (Gal-HCy-Biotin) for β-gal-activatable imaging of tumor senescence. Gal-HCy without tumor-targeted biotin is used as a control probe. Gal-HCy-Biotin is superior to Gal-HCy due to the higher kinetic parameter of Gal-HCy-Biotin than Gal-HCy in vitro. Moreover, biotin could help Gal-HCy-Biotin enter and accumulate in tumor cells with higher FL/PA signal. In detail, Gal-HCy-Biotin or Gal-HCy could image senescent tumor cells with 4.6-fold or 3.5fold FL enhancement and 4.1-fold or 3.3-fold PA enhancement. Gal-HCy-Biotin or Gal-HCy could image tumor senescence with 2.9-fold or 1.7-fold FL enhancement and 3.8-fold or 1.3-fold PA enhancement. We envision that Gal-HCy-Biotin will be applied for FL/PA imaging of tumor senescence in clinic.

Recent Advances in Design Strategies and Imaging Applications of Fluorescent Probes for ATP

“…However, these analytical methods have the disadvantage of low sensitivity. Fluorescence probes, with many advantages such as high sensitivity, excellent spatial and temporal resolution, and real-time in situ imaging, have emerged as crucial tools for the detection and imaging of bio-active substances during medical diagnosis [18][19][20][21][22][23][24][25][26][27][28][29][30][31]. Moreover, near-infrared (NIR) fluorescent probes have long excitation/emission wavelengths that allow deeper tissue penetration while reducing the background fluorescence of proteins and photodamage to biological samples [32][33][34][35][36][37][38][39][40][41][42][43][44].…”

Aptamer Conjugate-Based Ratiometric Fluorescent Probe for Precise Imaging of Therapy-Induced Cancer Senescence

“…Indeed, various activity-based imaging senoprobes have been developed and demonstrated great opportunities for sensing senescent cancer cells in a noninvasive, longitudinal manner. , They can be roughly divided into two types. The first, also the most widely investigated, type of senoprobes is designed in response to a single senescence-associated marker, such as enzymes, ions, and reactive species. − Nevertheless, such single-marker detection design typically suffers from low specificity because currently available markers are senescence-related but not specified. To address this issue, engineering dual-marker activated senoprobes has been emerging as an alternative strategy, in which imaging signals can be switched on only after sequential activation by two senescence-related markers, thereby offering enhanced imaging selectivity compared to the former strategy. − Intriguingly, we have recently found that such dual-marker recognition strategy could distinguish senescence-associated expression of markers from endogenous expression .…”

β-Galactosidase-Activated and Red Light-Induced RNA Modification Strategy for Prolonged NIR Fluorescence/PET Bimodality Imaging

“…As demonstrated in Scheme , we rationally designed and synthesized a β-Gal-activatable NIR FL/PET bimodal probe 68 Ga-NOTA-FCG consisting of three parts: (1) a triaaza triacetic acid chelator NOTA for 68 Ga-labeling; (2) a β-Gal-activated prequenched hemicyanine dye (CyGal) as a photosensitizer; (3) an 1 O 2 -mediated furan group for RNA modification. In β-Gal-positive tumor cells, the d -galactose moiety on CyGal is specifically cleaved by the highly expressed β-Gal in the lysosomes, − producing an enhanced NIR FL signal, which can be combined with the PET signal of 68 Ga for highly sensitive tumor imaging. Moreover, the ability of the responsive probe to produce 1 O 2 under 690 nm laser irradiation is greatly enhanced, which can trigger the covalent cross-linking of the furan group of the probe to the nucleotides of cytoplasmic RNAs, thereby preventing the exocytosis of the probe, resulting in prolonged retention and high-contrast signals.…”