In Situ Visualizing Carboxylesterase Activity in Type 2 Diabetes Mellitus Using an Activatable Endoplasmic Reticulum Targetable Proximity Labeling Far-Red Fluorescent Probe

Carboxylesterase (CE), an enzyme widely present in organisms, is involved in various physiological and pathological processes. Changes in the levels of CEs in the liver may predict the presence of type 2 diabetes mellitus (T2DM). Here, a novel dicyanoisophorone (DCI)-based proximity-labeled far-red fluorescent probe DCI2F-Ac with endoplasmic reticulum targeting was proposed for real-time monitoring and imaging of the CEs activity. DCI2F-Ac featured very low cytotoxicity and biotoxicity and was highly selective and sensitive for CEs. Compared with traditional CEs probes, DCI2F-Ac was covalently anchored directly to CEs, thus effectively reducing the loss of in situ fluorescent signals due to diffusion. Through the "on-off" fluorescence signal readout, DCI2F-Ac was able to distinguish cell lines and screen for CEs inhibitors. In terms of endoplasmic reticulum (ER) stress, it was found that thapsigargin (Tg) induced upregulation of CEs levels but not tunicamycin (Tm), which was related to the calcium homeostasis of the ER. DCI2F-Ac could efficiently detect downregulated CEs in the livers of T2DM, and the therapeutic efficacy of metformin, acarbose, and a combination of these two drugs was assessed by tracking the fluctuation of CEs levels. The results showed that combining metformin and acarbose could restore CEs levels to near-normal levels with the best antidiabetic effect. Thus, the DCI2F-Ac probe provides a great opportunity to explore the untapped potential of CEs in liver metabolic disorders and drug efficacy assessment.

Installation of high-affinity Siglec-1 ligand on tumor surface for macrophage-engaged tumor suppression

Siglecs that binds cell surface sialoglycans are a family of immunomodulatory receptors, of which, Siglec-7 expressed on natural killer (NK) cells promotes tumor immunoevation while the role of Siglec-1 expressed on macrophages on tumor development remains largely unexplored. Herein, we selectively introduced high affinity sialoside ligands of Siglec-1 and Siglec-7 to tumor cell surface via in vivo Strain-promoted Azide-Alkyne cyclization of ^TCCSiaα2,3-Lactose or ^FITCSiaα2,6-Lactose with 9-azido sialic acid (^AzSia) metabolically installed on tumor cell surface. We found that ^TCCSiaα2,3-Lactose conjugated on tumor surface moderately inhibited tumor growth while ^FITCSiaα2,6-Lactose promote tumor growth. These results suggest high-affinity ligand of Siglec-1 dispalyed on tumors surface provide a new perspective for tumor immunotherapy.

Activatable Dual ROS-Producing Probe for Dual Organelle-Engaged Photodynamic Therapy

Photodynamic therapy (PDT) necessitates approaches capable of increasing antitumor effects while decreasing nonspecific photodamage. We herein report an activatable probe (Glu-PyEB) comprising two distinct photosensitizers with mutually suppressed photodynamics. Activation by tumor-associated γ-glutamyltranspeptidase gives rise to a generator of superoxide radical (O₂^-•) accumulated in lysosomes and a producer of singlet oxygen (¹O₂) enriched in mitochondria. This enables light-irradiation-triggered damage of lysosomes and mitochondria, robust cell death, and tumor retardation in vivo, showing the use of paired photosensitizers subjected to reciprocally suppressed photodynamics for activatable PDT.

A fluorescence-activatable tumor-reporting probe for precise photodynamic therapy

Approaches that could enable precise photodynamic therapy (PDT) are of therapeutic potential. We herein report a trifunctional probe (Glu-RdEB) that could be activated to generate fluorescent rhodamine species to pinpoint tumor foci. The probe contains a γ-glutaminyl moiety cleavable to γ-glutamyl transpeptidase (GGT) overexpressed in multiple tumors, an entity of an ENBS photosensitizer for PDT, and an entity of rhodamine fluorescently quenched by ENBS. Upon activation by tumor-associated GGT, the probe releases highly fluorescent rhodamine that is selectively confined in tumors whereby light irradiation leads to effective tumor regression in mice. These results indicate the feasibility of a fluorescently quenched dye-photosensitizer pair to yield tumor-activatable fluorescence to direct PDT.