γ-Glutamyltranspeptidase and pH based "AND" logic gate fluorescent probe for orthotopic breast tumor imaging

Xanthene-based NIR organic phototheranostics agents: design strategies and biomedical applications

Fluorescence imaging and phototherapy in the near-infrared window (NIR, 650-1700 nm) have attracted great attention for biomedical applications due to their minimal invasiveness, ultra-low photon scattering and high spatial-temporal precision. Among NIR emitting/absorbing organic dyes, xanthene derivatives with controllable molecular structures and optical properties, excellent fluorescence quantum yields, high molar absorption coefficients and remarkable chemical stability have been extensively studied and explored in the field of biological theranostics. The present study was aimed at providing a comprehensive summary of the progress in the development and design strategies of xanthene derivative fluorophores for advanced biological phototheranostics. This study elucidated several representative controllable strategies, including electronic programming strategies, extension of conjugated backbones, and strategic establishment of activatable fluorophores, which enhance the NIR fluorescence of xanthene backbones. Subsequently, the development of xanthene nanoplatforms based on NIR fluorescence for biological applications was detailed. Overall, this work outlines future efforts and directions for improving NIR xanthene derivatives to meet evolving clinical needs. It is anticipated that this contribution could provide a viable reference for the strategic design of organic NIR fluorophores, thereby enhancing their potential clinical practice in future.

A Triple-Responsive and Dual-NIR Emissive Fluorescence Probe for Precise Cancer Imaging and Therapy by Activating Pyroptosis Pathway

Revealing changes in the tumor microenvironment is crucial for understanding cancer and developing sensitive methods for precise cancer imaging and diagnosis. Intracellular hydrogen peroxide (H2O2) and microenvironmental factors (e.g., viscosity and polarity) are closely linked to various physiological and pathological processes, making them potential biomarkers for cancer. However, a triple-response theranostic probe for precise tumor imaging and therapy has not yet been achieved due to the lack of effective tools. Herein, we present a mitochondria-targeting near-infrared (NIR) fluorescent probe, VPH-5DF, capable of simultaneously monitoring H2O2, viscosity, and polarity through dual NIR channels. The probe specifically detects H2O2 via NIR emission (λem = 650 nm) and shows high sensitivity to microenvironmental viscosity/polarity in the deep NIR channel (λem ≈ 750 nm). Furthermore, the probe not only monitors mitochondrial polarity, viscosity, and fluctuations in endogenous/exogenous H2O2 levels but also distinguishes cancer cells from normal cells through multiple parameters. Additionally, VPH-5DF can be employed to monitor alterations in H2O2 levels, as well as changes in viscosity and polarity, during drug-induced pyroptosis in living cells. After treatment with VPH-5DF, chemotherapy-induced oxidative damage to the mitochondria in tumor cells activated the pyroptosis pathway, leading to a robust antitumor response, as evidenced in xenograft tumor models. Thus, this triple-response theranostic prodrug offers a new platform for precise in vivo cancer diagnosis and anticancer chemotherapy.

Molecular Engineering of Xanthene Dyes with 3D Multimodal-Imaging Ability to Guide Photothermal Therapy

Phototheranostics integrates light-based diagnostic techniques with therapeutic interventions, offering a non-invasive, precise, and swift approach for both disease detection and treatment. The efficacy of this approach hinges on the multimodal imaging potential and photothermal conversion efficiency (PCE) of phototheranostic agents (PTAs). Despite the promise, crafting multifunctional phototheranostic organic small molecules brims with challenges. In this research, four innovative xanthene-derived PTAs are synthesized by fine-tuning the donor-π-acceptor (D-π-A) system to strike a balance between radiative and nonradiative decay. The inherent robust photostability and intense fluorescence of the traditional xanthene core are preserved, meanwhile the addition of highly electron-withdrawing groups boosts the non-radiative decay rate to enhance PCE and photoacoustic imaging capabilities. Remarkably, one of the PTAs, DMBA, demonstrates an exceptional absolute fluorescence quantum yield of 2.46% in PBS, and when encapsulated into nanoparticles, it achieves a high PCE of 79.5%. Consequently, DMBA nanoparticles (DMBA-NPs) are effectively employed in fluorescence, 3D photoacoustic, and photothermal imaging-guiding tumor photothermal therapy. This represents the first instance of a multimodal phototheranostic xanthene agent achieving synergistic fluorescence and photoacoustic imaging for diagnostic purposes. Furthermore, this work paves the way for leveraging xanthene fluorophores as versatile tools in the development of multifunctional reagents.

Progression in Near-Infrared Fluorescence Imaging Technology for Lung Cancer Management

Lung cancer is a major threat to human health and a leading cause of death. Accurate localization of tumors in vivo is crucial for subsequent treatment. In recent years, fluorescent imaging technology has become a focal point in tumor diagnosis and treatment due to its high sensitivity, strong selectivity, non-invasiveness, and multifunctionality. Molecular probes-based fluorescent imaging not only enables real-time in vivo imaging through fluorescence signals but also integrates therapeutic functions, drug screening, and efficacy monitoring to facilitate comprehensive diagnosis and treatment. Among them, near-infrared (NIR) fluorescence imaging is particularly prominent due to its improved in vivo imaging effect. This trend toward multifunctionality is a significant aspect of the future advancement of fluorescent imaging technology. In the past years, great progress has been made in the field of NIR fluorescence imaging for lung cancer management, as well as the emergence of new problems and challenges. This paper generally summarizes the application of NIR fluorescence imaging technology in these areas in the past five years, including the design, detection principles, and clinical applications, with the aim of advancing more efficient NIR fluorescence imaging technologies to enhance the accuracy of tumor diagnosis and treatment.

Enzyme-responsive, multi-lock optical probes for molecular imaging and disease theranostics

Optical imaging is an indispensable tool for non-invasive visualization of biomolecules in living organisms, thereby offering a sensitive approach for disease diagnosis and image-guided disease treatment. Single-lock activatable optical probes (SOPs) that specifically switch on optical signals in the presence of biomarkers-of-interest have shown both higher detection sensitivity and imaging quality as compared to conventional "always-on" optical probes. However, such SOPs can still show "false-positive" results in disease diagnosis due to non-specific biomarker expression in healthy tissues. By contrast, multi-lock activatable optical probes (MOPs) that simultaneously detect multiple biomarkers-of-interest could improve detection specificity towards certain biomolecular events or pathological conditions. In this Review, we discuss the recent advancements of enzyme-responsive MOPs, with a focus on their biomedical applications. The higher detection specificity of MOPs could in turn enhance disease diagnosis accuracy and improve treatment efficacy in image-guided disease therapy with minimal toxicity in the surrounding healthy tissues. Finally, we discuss the current challenges and suggest future applications of MOPs.

Advances and Perspectives of Responsive Probes for Measuring γ-Glutamyl Transpeptidase

Gamma-glutamyltransferase (GGT) is a plasma-membrane-bound enzyme that is involved in the γ-glutamyl cycle, like metabolism of glutathione (GSH). This enzyme plays an important role in protecting cells from oxidative stress, thus being tested as a key biomarker for several medical conditions, such as liver injury, carcinogenesis, and tumor progression. For measuring GGT activity, a number of bioanalytical methods have emerged, such as chromatography, colorimetric, electrochemical, and luminescence analyses. Among these approaches, probes that can specifically respond to GGT are contributing significantly to measuring its activity in vitro and in vivo. This review thus aims to highlight the recent advances in the development of responsive probes for GGT measurement and their practical applications. Responsive probes for fluorescence analysis, including "off-on", near-infrared (NIR), two-photon, and ratiometric fluorescence response probes, are initially summarized, followed by discussing the advances in the development of other probes, such as bioluminescence, chemiluminescence, photoacoustic, Raman, magnetic resonance imaging (MRI), and positron emission tomography (PET). The practical applications of the responsive probes in cancer diagnosis and treatment monitoring and GGT inhibitor screening are then highlighted. Based on this information, the advantages, challenges, and prospects of responsive probe technology for GGT measurement are analyzed.

Molecular Engineering of Sulfone-Xanthone Chromophore for Enhanced Fluorescence Navigation

Enriching the palette of high-performance fluorescent dyes is vital to support the frontier of biomedical imaging. Although various rhodamine skeletons remain the premier type of small-molecule fluorophores due to the apparent high brightness and flexible modifiability, they still suffer from the inherent defect of small Stokes shift due to the nonideal fluorescence imaging signal-to-background ratio. Especially, the rising class of fluorescent dyes, sulfone-substituted xanthone, exhibits great potential, but low chemical stability is also pointed out as the problem. Molecular engineering of sulfone-xanthone to obtain a large Stokes shift and high stability is highly desired, but it is still scarce. Herein, we present the combination modification method for optimizing the performance of sulfone-xanthone. These redesigned fluorescent skeletons owned greatly improved stability and Stokes shift compared with the parent sulfone-rhodamine. To the proof of bioimaging capacity, annexin protein-targeted peptide LS301 was introduced to the most promising dyes, J-S-ARh, to form the tumor-targeted fluorescent probe, J-S-LS301. The resulting probe, J-S-LS301, can be an outstanding fluorescence tool for the orthotopic transplantation tumor model of hepatocellular carcinoma imaging and on-site pathological analysis. In summary, the combination method could serve as a basis for rational optimization of sulfone-xanthone. Overall, the chemistry reported here broadens the scope of accessible sulfone-xanthone functionality and, in turn, enables to facilitate the translation of biomedical research toward the clinical domain.

Recent progress in the development of small-molecule double-locked logic gate fluorescence probes

Various bioactive substances are simultaneously involved in physiological processes, and research on the synergistic effect of them can promote the study of pathological mechanisms. To achieve this purpose, several small-molecule double-locked logic gate fluorescence probes have been developed recently. They overcome many shortcomings of the traditional "single-signal" fluorescent probes, with fluorescence that can be activated by two analytes of interest order-independently or order-dependently with one output. In this review, we summarize recently published small-molecule double-locked logic gate probes for the optical detection of two bioactive substances in living systems. We envision that this review will attract significant attention from researchers to exploit more powerful functional double-locked logic gate probes.

Rational Design of pH-Independent and High-Fidelity Near-Infrared Tunable Fluorescent Probes for Tracking Leucine Aminopeptidase In Vivo

Accurate detection of target analytes and generation of high-fidelity fluorescence signals are particularly critical in life sciences and clinical diagnostics. However, the majority of current NIR-I fluorescent probes are vulnerable to pH effects resulting in signal distortion. In this work, a series of fluorescence-tunable and pH-independent probes are reported by combining optically tunable groups of unsymmetric Si-rhodamines and introducing the methoxy instead of the spiro ring on the benzene ring at position 9. To validate the concept, the leucine aminopeptidase response site was introduced into Si-2,6OMe-NH2 with the best optical properties to synthesize Si-LAP for monitoring the intrahepatic LAP in vivo. Therefore, the design approach may provide a new and practical strategy for designing innovative functional fluorescent probes and generating high-stability and high-fidelity fluorescent signals.