Quantitatively Visualizing Tumor-Related Protease Activity in Vivo Using a Ratiometric Photoacoustic Probe

Abstract

The abnormal expression of tumor-related proteases plays a critical role in cancer invasion, progression, and metastasis. Therefore, it is considerably meaningful to non-invasively assess the proteases' activity in vivo for both tumor diagnosis and therapeutic evaluation. Herein, we report an activatable probe constructed with a near-infrared dye (Cy5.5) and a quencher (QSY21) covalently linked through a peptide substrate of matrix metalloproteinases-2 (MMP-2) that was chosen as a model for tumor-associated proteases. Upon cleavage with activated MMP-2, this probe emitted an MMP-2-concentration-dependent fluorescence. Quite unexpectedly, owing to the variation in the aggregation state of both the dye and its quencher as a consequence of the cleavage, the responsive probe presented a dramatic MMP-2-concentrationdependent absorption at around 680 nm, while that at around 730 nm was MMP-2 concentration independent. These features allowed detection of MMP-2 activity via both fluorescence and photoacoustic (PA) imaging in vitro, respectively. Moreover, taking the PA signal at 730 nm as an internal reference, the PA signal at 680 nm allowed quantitative detection of MMP-2 expression in breast cancer in vivo. We thus envision that our current approach would offer a useful tool for studying the malignant impacts of versatile tumor-associated proteases in vivo.

Materdicine: Interdiscipline of materials and medicine

“…To address this crucial issue, a NIR fluorophore (Cy5.5) and a quencher (QSY21) were covalently conjugated with a MMP‐2‐cleavable peptide sequence to establish an activatable PA probe (denoted as QC) for quantitative analysis of the MMP‐2 activity in breast cancers (Figure 4A). 59 The self‐assembled QC nanoparticles displayed negligible fluorescence but were promptly activated by MMP‐2 to emit intense fluorescence. Importantly, the intensity of PA signal at 680 nm decreased in a MMP‐2 concentration‐dependent manner (Figure 4B).…”

“…(F) and (G) MMP‐2 expression levels calculated through (F) tumor‐size‐dependent approach, and (G) the ratiometric ratio of ∆PAS 680 /∆PAS 730 . Reproduced with permission 59 . Copyright 2019, American Chemical Society…”

Activatable nanoscale metal-organic framework for ratiometric photoacoustic imaging of hydrogen sulfide and orthotopic colorectal cancer in vivo

“…Nevertheless, PA imaging of numerous physiological and disease processes usually suffers from the serious light scattering of biological tissues as well as undesirable nonspecific signal output, leading to the insufficient sensitivity of PA imaging [14][15][16]. Thus, the development of functional PA probes, especially ratiometric probes with near-infrared (NIR, 650-1,700 nm) light absorption, is highly required to improve the signal to noise ratio of PA imaging [17][18][19][20][21][22]. Ratiometric PA probes can not only offer real-time information upon molecular targetassociated biological and pathological status at molecular level with low background noise, but also significantly eliminate the interference arising from in vivo heterogeneous probe distribution and tissue scattering.…”

Towards Personalized Medicine: Photoacoustic Imaging of Glutathione Enables Companion Diagnosis and Targeted Treatment of Lung Cancer

“…8 Recently, our group and others have expanded the scope of PA imaging through the development of acoustogenic ABS probes. 9,10 Select examples include imaging agents for the detection of metal ion dysregulation, [11][12][13][14] hypoxia, [15][16][17][18] proteases, 19,20 and signaling molecules (e.g., nitric oxide 21,22 and hydrogen sulfide 23 ). In this study we leverage classic principles in physical organic chemistry to guide the development of the first PA imagingbased CDx (PACDx), as well as a matching Gemcitabine-based prodrug (PARx).…”