An Aggregation-Induced Emission Nanosensor for Real-Time Chemiluminescent Sensing of Light-Independent Intracellular Singlet Oxygen

Innovations in aggregation-induced emission materials for theranostics in the musculoskeletal system

Aggregation-induced emission (AIE) offers a promising solution for achieving lower background and more reliable signals in biomedical imaging. AIE materials also exhibiting photostability and resistance to photobleaching. These characters are crucial for monitoring musculoskeletal functions and offering targeted therapies for related diseases. This review compiles research on AIEgens targeting various molecules, cells, or tissues within the musculoskeletal system under physiological or pathological conditions and classifies them according to different clinical applications. A sort of AIEgens is applied in monitoring osteogenic differentiation and bone component analysis. Additionally, AIEgens targeting intra-articular inflammatory or rheumatic related molecules, such as reactive oxygen species, enable early-stage diagnosis and targeted therapies of arthritis. Researchers have also developed novel materials containing AIEgens for joint tissue repair. This review highlights the advantages of these applications while also exploring future demands and development directions in musculoskeletal system imaging and treatment, aiming to promote further design of AIEgens and their clinical applications in musculoskeletal diseases.

Near-infrared AIE chemiluminescence probe for monitoring and evaluating singlet oxygen in vivo

The incorporation a "singlet oxygen (1O2) battery" into photodynamic therapy (PDT) could overcome the deficiency of tumor hypoxia in PDT and enhance its effect. However, real-time monitoring the 1O2 release efficiency of the 1O2 battery still presents a significant challenge in vivo. To address this issue, we have developed a bright aggregation-induced emission (AIE) chemiluminescence (CL) probe (DTLum), which conjugates a luminol unit with a donor-acceptor structured diketopyrrolopyrrole fluorophore, for the specific detection of 1O2. Subsequently, the DTLum nanoparticles (DTLum NPs) were prepared using PEO100-PPO65-PEO100 (Pluronic F127) as the surfactant. The DTLum NPs can detect 1O2 in aqueous solution with a bright near-infrared (NIR) CL signal (651 nm) and great tissue penetration (12.5 mm), making them suitable for the detection of 1O2 both in vitro (quantitative) and in vivo (qualitative). Notably, by utilizing the DTLum NPs, the process of 1O2 release in 1O2 batteries with different release rates can be visually monitored in cells and in vivo. This NIR CL probe provides a powerful platform for real-time monitoring and evaluating the release efficiency of 1O2 battery.

Aggregation Induced Emission Based Luminogenic (AIEgenic) Probes for the Biomarker Detection

Various biomarkers such as proteins play key roles in controlling crucial biochemical processes. The critical concentration of the biomarkers is important to maintain a healthy life. In fact, imbalance in concentration or irregular activity of these can lead to various diseases like Cancer, Alzheimer's etc. Therefore, the disease related biomarkers and their timely detection are key to control the illness. In the literature, a few activity-based probes for the detection of such biomarkers are available. As per the requirement an ideal probe should be very specific to recognize the target analyte and that could be achieved by virtue of having a robust structure and stimuli responsive nature. In this regard, several fluorescent probes are of great choice. Although these fluorescent probes face certain challenges such as aggregation caused quenching, which heavily affects the sensitivity and photostability is another major concern for many fluorescent probes. To overcome these challenges aggregation-induced emissive fluorescent probes found to be an excellent alternative. Aggregation induced emissive luminogens (AIEgens) offer higher signal to noise ratios and found to possess better photostability during sensing and imaging. In the present review we have summarized the development of AIEgenic probes for sensing and imaging of disease related biomarkers. We believe this review could be a guide to design efficient AIEgenic probes for the diagnostics development.

A de novo zwitterionic strategy of ultra-stable chemiluminescent probes: highly selective sensing of singlet oxygen in FDA-approved phototherapy

Singlet oxygen (1O2), as a fundamental hallmark in photodynamic therapy (PDT), enables ground-breaking clinical treatment in ablating tumors and killing germs. However, accurate in vivo monitoring of 1O2 remains a significant challenge in probe design, with primary difficulties arising from inherent photo-induced side reactions with poor selectivity. Herein, we report a generalizable zwitterionic strategy for ultra-stable near-infrared (NIR) chemiluminescent probes that ensure a highly specific [2 + 2] cycloaddition between fragile electron-rich enolether units and 1O2 in both cellular and dynamic in vivo domains. Innovatively, zwitterionic chemiluminescence (CL) probes undergo a conversion into an inert ketone excited state with an extremely short lifetime through conical intersection (CI), thereby affording sufficient photostability and suppressing undesired photoreactions. Remarkably, compared with the well-known commercial 1O2 probe SOSG, the zwitterionic probe QMI exhibited an ultra-high signal-to-noise ratio (SNR, over 40-fold). Of particular significance is that the zwitterionic CL probes demonstrate excellent selectivity, high sensitivity, and outstanding photostability, thereby making a breakthrough in real-time tracking of the FDA-approved 5-ALA-mediated in vivo PDT process in living mice. This innovative zwitterionic strategy paves a new pathway for high-performance NIR chemiluminescent probes and high-fidelity feedback on 1O2 for future biological and medical applications.

Chemiluminescent Conjugated Polymer Nanoparticles for Deep-Tissue Inflammation Imaging and Photodynamic Therapy of Cancer

Deep-tissue optical imaging and photodynamic therapy (PDT) remain a big challenge for the diagnosis and treatment of cancer. Chemiluminescence (CL) has emerged as a promising tool for biological imaging and in vivo therapy. The development of covalent-binding chemiluminescence agents with high stability and high chemiluminescence resonance energy transfer (CRET) efficiency is urgent. Herein, we design and synthesize an unprecedented chemiluminescent conjugated polymer PFV-Luminol, which consists of conjugated polyfluorene vinylene (PFV) main chains and isoluminol-modified side chains. Notably, isoluminol groups with chemiluminescent ability are covalently linked to main chains by amide bonds, which dramatically narrow their distance, greatly improving the CRET efficiency. In the presence of pathologically high levels of various reactive oxygen species (ROS), especially singlet oxygen (1O2), PFV-Luminol emits strong fluorescence and produces more ROS. Furthermore, we construct the PFV-L@PEG-NPs and PFV-L@PEG-FA-NPs nanoparticles by self-assembly of PFV-Luminol and amphiphilic copolymer DSPE-PEG/DSPE-PEG-FA. The chemiluminescent PFV-L@PEG-NPs nanoparticles exhibit excellent capabilities for in vivo imaging in different inflammatory animal models with great tissue penetration and resolution. In addition, PFV-L@PEG-FA-NPs nanoparticles show both sensitive in vivo chemiluminescence imaging and efficient chemiluminescence-mediated PDT for antitumors. This study paves the way for the design of chemiluminescent probes and their applications in the diagnosis and therapy of diseases.

ROS-Responsive Fluorescent Sensor Array for Precise Diagnosis of Cancer via pH-Controlled Multicolor Gold Nanoclusters

Intracellular reactive oxygen species (ROS) are closely associated with cancer cell types. Therefore, ROS-based pattern recognition is a promising strategy for precise diagnosis of cancer, but such a possibility has never been reported yet. Herein, we proposed an ROS-responsive fluorescent sensor array based on pH-controlled histidine-templated gold nanoclusters (AuNCs@His) to distinguish cancer cell types and their proliferation states. In this strategy, three types of AuNCs@His with diverse fluorescence profiles were first synthesized by only adjusting the pH value. Upon the addition of various ROS, fluorescence quenching of three types of AuNCs@His occurred with different degrees, thereby forming unique optical "fingerprints", which were well-clustered into several separated groups without overlap by principal component analysis (PCA). The sensing mechanism was attributable to the oxidation of AuNCs@His by ROS, as revealed by X-ray photoemission spectroscopy, Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, and electrospray ionization mass spectrometry. Based on the ROS-responsive sensing pattern, cancer cell types were successfully differentiated via PCA with 100% accuracy. Additionally, the proposed sensor array exhibited excellent performance in distinguishing the proliferation states of cancer cells, which was supported by the results of the Ki-67 immunohistochemistry assay. Overall, the ROS-responsive fluorescent sensor array can serve as a promising tool for precise diagnosis of cancer, indicating great potential for clinical application.