A mitochondria-targeted chemiluminescent probe for detection of hydrogen sulfide in cancer cells, human serum and in vivo

Sensitive detection of fluid biomarkers using adamantylidene 1,2-dioxetane based chemiluminescent probes

Body fluid analysis is a crucial non-invasive diagnostic tool that offers valuable insights into the body's physiological state and aids in early disease detection. Traditional methods, however, can be costly, time-consuming, and lack sensitivity. To address these issues, fluorescence imaging technology, employing various fluorescent probes, has emerged as a promising alternative. Yet, background fluorescence from compounds in body fluids can interfere with analytical sensitivity. Chemiluminescent probes, particularly Schaap's adamantylidene 1,2-dioxetane based ones, overcome this challenge by eliminating the need for external excitation and enhancing the signal-to-noise ratio. In this feature article, we summarize recent advancements in the design and application of Schaap's adamantylidene 1,2-dioxetane based chemiluminescent probes for detecting analytes in body fluids such as blood, plasma, urine, and sputum. Our discussion covers contributions from both our own research and the work of others, focusing on the detection of fluid biomarkers for specific diseases. Additionally, we discuss the challenges faced and propose future research directions in designing Schaap's adamantylidene 1,2-dioxetane based probes tailored for body fluid analysis. We hope this review inspires further development of chemiluminescent probes suitable for a wide range of body fluid analyses.

A silicon rhodamine 1,2-dioxetane chemiluminophore for in vivo near-infrared imaging

Near-infrared (NIR) chemiluminescent probes have attracted increasing attention in recent years due to their attractive properties for in vivo imaging. Herein, we developed a NIR chemiluminophore silicon rhodamine (SiRCL-1) based on the intramolecular energy transfer process from excited state benzoate to a silicon rhodamine emitter under aqueous conditions. SiRCL-1 exhibited dual emission peaks at 540 nm and 680 nm with a high signal penetration through tissue at 680 nm (>30 mm) and long-lasting in vivo luminescence (>50 min), demonstrating its significance as a chemiluminescence scaffold for biological application.

Design and Characterization of Novel Naphthalimide Fluorescent Probe for H2S Detection in Human Serum

In this work, a novel fluorescent probe (compound 2) based on the Intramolecular charge transfer (ICT) mechanism was designed and successfully applied to determine H2S in human serum. Fluorophore 1,8-naphthalimide was chosen, while the azide group was the recognition group for H2S determination. By introducing p-toluidine moiety on the imide part of the molecule, a donor-acceptor (D-A) conjugated system was formed. Prepared compound 2 was characterized using 1H, 13C NMR spectroscopy, and elemental analysis. Fluorescence spectra measurements were carried out, and several influences on fluorescence intensity were investigated, including pH, time dependence, selective response, and influence of H2S concentration. Conducted experiments, including the calculated detection limit of the prepared fluorescent probe, which was found to be 0.085 µmol·L- 1, showing that compound 2 could be applied for H2S detection in human serum and could detect low micromolar concentrations of H2S. Finally, compound 2 was successfully applied to detect H2S in a human serum sample, whereby the concentration of H2S was 17.2 µmol·L- 1. The accuracy of the H2S determination was confirmed with the standard addition method.

Phenoxy-1,2-dioxetane-based activatable chemiluminescent probes: tuning of photophysical properties for tracing enzymatic activities in living cells

The use of chemiluminophores for tracing enzymatic activities in live-cell imaging has gained significant attention, making them valuable tools for diagnostic applications. Among various chemiluminophores, the phenoxy-1,2-dioxetane scaffold exhibits significant structural versatility and its activation is governed by the chemically initiated electron exchange luminescence (CIEEL) mechanism. This mechanism can be initiated by enzymatic activity, changes in pH, or other chemical stimuli. The photophysical properties of phenoxy-1,2-dioxetanes can be fine-tuned through the incorporation of different substituents on the phenolic ring and by anchoring them with specific triggers. This review discusses the variations in physicochemical properties, including emission maxima, quantum yield, aqueous solubility, and pKa, as influenced by structural modifications, thereby establishing a comprehensive structure-activity relationship. Furthermore, it categorises the probes based on different enzyme classes, such as hydrolase-sensitive probes, oxidoreductase-responsive probes, and transferase-activatable phenoxy-1,2-dioxetanes, offering a promising platform technology for the early diagnosis of diseases and disorders. The summary section highlights key opportunities and limitations associated with applying phenoxy-1,2-dioxetanes in achieving precise and effective enzyme assays.

Dual-Locked Probe with Activatable Sonoafterglow Luminescence for Precise Imaging of MET-Induced Liver Injury

Metformin (MET) is currently the first-line treatment for type 2 diabetes mellitus (T2DM). However, overdose and long-term use of MET may induce a serious liver injury. What's worse, diagnosis of MET-induced liver injury remains challenging in clinic. Although several probes have been reported for imaging MET-induced liver injury utilizing upregulated hepatic H2S as a biomarker, they are still at risk of nonspecific activation in complex physiological environments and rely on light excitation with limited imaging depth. Herein, we rationally designed and developed a dual-locked probe, DPA-H2S, for precise imaging of MET-induced liver injury by H2S-activated sonoafterglow luminescence. DPA-H2S is a small molecule consisting of a sonosensitizer protoporphyrin IX (PpIX) and an afterglow substrate that is dual-locked with a H2S-responsive 2,4-dinitrobenzene group and a 1O2-responsive electron-rich double bond. When employing DPA-H2S for imaging of MET-induced liver injury in vivo, since the PpIX moiety can produce 1O2 in situ at the liver site under focused ultrasound (US) irradiation, the two locks of DPA-H2S can be specifically activated by the highly upregulated H2S at the liver injury sites and the in situ generated 1O2, respectively. Thus, the sonoafterglow signal of DPA-H2S is significantly turned on, enabling precise imaging of the MET-induced liver injury. In vitro results showed that, through H2S-activated sonoafterglow luminescence, DPA-H2S was capable of imaging H2S with good sensitivity and high selectivity and realized deep tissue imaging (∼20 mm, signal-to-background ratio (SBR) = 3.4). Furthermore, we successfully applied DPA-H2S for precise in vivo imaging of MET-induced liver injury. We anticipate that our dual-locked probe, DPA-H2S, may serve as a promising tool in assisting the diagnosis of MET-induced liver injury in clinics and informing the clinical utilization of MET in the near future.

An Aggregation-Induced Fluorescence Probe for Detection H2S and Its Application in Cell Imaging

Monitoring hydrogen sulfide (H2S) in living organisms is very important because H2S acts as a regulator in many physiological and pathological processes. Upregulation of endogenous H2S concentration has been shown to be closely related to the occurrence and development of tumors, atherosclerosis, neurodegenerative diseases and diabetes. Herin, a novel fluorescent probe HND with aggregation-induced emission was designed. Impressively, HND exhibited a high selectivity, fast response (1 min) and low detection limit (0.61 μM) for H2S in PBS buffer (10 mM, pH = 7.42). Moreover, the reaction mechanism between HND and H2S was conducted by Job's plot, HR-MS, and DFT. In particular, HND was successfully employed to detect H2S in HeLa cells.

Hyper-Responsive Chemiluminescent Probe Reveals Distinct PYRase Activity in Pseudomonas aeruginosa

Pyrrolidone carboxyl peptidase, commonly known as PYRase, is an exopeptidase that catalytically cleaves an N-terminal pyroglutamic acid from peptides or proteins. The diverse functions of PYRases in bacterial enzymology have prompted the development of various bacterial diagnostic techniques. However, the specific physiological role and activity of this enzyme across the bacterial kingdom remain unclear. Here, we present a functional phenoxy-1,2-dioxetane chemiluminescent probe (PyrCL) that can selectively detect PYRase activity in both Gram-positive and Gram-negative bacteria. The probe activation mechanism is based on the cleavage of a pyroglutamyl substrate, followed by a release of the phenoxy-dioxetane luminophore, which then undergoes efficient chemiexcitation to emit a green photon. Probe PyrCL exhibits an effective turn-on response with superior detection capability in terms of response time and sensitivity compared to existing fluorescence probes. The superior detection sensitivity of the chemiluminescent probe enables us to reveal previously undetected PYRase activity in Streptococcus mutans. Furthermore, it enables the discrimination of Pseudomonas aeruginosa from other Gram-negative bacteria in the tested panel, based on their distinct PYRase activity. We expect that probe PyrCL will have great value for PYRase-based bacteria diagnosis with use in basic research and clinical applications.

Hydrogen sulfide (H2S) metabolism: Unraveling cellular regulation, disease implications, and therapeutic prospects for precision medicine

Hydrogen sulfide (H2S), traditionally recognized as a noxious gas with a pungent odor, has emerged as a fascinating metabolite originating from proteinaceous foods. This review provides a comprehensive examination of H2S regulatory metabolism in cell. Dysregulation of cellular processes plays a pivotal role in the pathogenesis of numerous diseases. Recent development explores the chemistry of biosynthesis and degradation of H2S in cells. The consequences of dysregulation causing diseases and the emerging role of hydrogen sulfide (H2S) modulation as a promising therapeutic platform has not been explored much. These disturbances can manifest as oxidative stress, inflammation, and aberrant cellular signaling pathways, contributing to the development and progression of diseases such as cancer, cardiovascular disorders, neurodegenerative diseases, and diabetes. Hydrogen sulfide has gained recognition as a key player in cellular regulation. H2S is involved in numerous physiological processes, including vasodilation, inflammation control, and cytoprotection. Recent advances in research have focused on modulating H2S levels to restore cellular balance and mitigate disease progression. This approach involves both exogenous H2S donors and inhibitors of H2S -producing enzymes. By harnessing the versatile properties of H2S, researchers and clinicians may develop innovative therapies that address the root causes of dysregulation-induced diseases. As our understanding of H2S biology deepens, the potential for precision medicine approaches tailored to specific diseases becomes increasingly exciting, holding the promise of improved patient outcomes and a new era in therapeutics.