Activatable near-infrared probes for the detection of specific populations of tumour-infiltrating leukocytes in vivo and in urine

Differential Optical Imaging of Antigen Presentation Machinery Using Molecular Optical Reporters

Detection of antigen presentation is central to understanding immunological processes and developing therapeutics for cancer, infectious diseases, and allergies. However, methods with the ability to dynamically and noninvasively distinguish between major histocompatibility complex class I (MHC-I) and MHC-II antigen presentations remain lacking. Herein, we develop activatable molecular optical reporters (MORs) for real-time differential imaging of antigen presentations in lymph nodes (LNs). These MORs are engineered to passively target LNs and activated through proteolytic cleavage by key enzymes in the MHC-I and MHC-II pathways, the immunoproteasome (iP) and cathepsin S (CTSS), respectively, triggering their chemiluminescent or fluorescent signals. Coupled with minimized signal crosstalk and high sensitivity, MORs delineate the subtle differences in the antigen presentation machinery across various disease models, including cancer and bacterial or viral infection, a feat unattainable for existing imaging methods. After systemic administration, MORs also allow real-time visualization of antigen presentation in the tumor microenvironment. Besides, MORs are validated to have potential for preclinical application in immunotherapeutics screening and clinical application in tissue biopsy. Thus, our study not only presents the first example of real-time, in vivo differential imaging of antigen presentation pathways but also opens new avenues for optical probes in immune contexture analysis.

Multiplex imaging of amyloid-β plaques dynamics in living brains with quinoline-malononitrile-based probes

The dynamic behaviour of amyloid-β (Aβ) plaques in Alzheimer's disease remains poorly understood, and accumulation and distribution of Aβ plaques must be inferred from in vitro pathological changes in brain tissue. In situ detection of Aβ plaques in live imaging is challenging because of the lack of adequate probes. Here we report the design of unimolecular quinoline-malononitrile-based Aβ probes, termed QMFluor integrative framework, that binds in vivo to Aβ plaques, making them detectable via near-infrared fluorescence imaging, magnetic resonance imaging, positron emission tomography and computed tomography. QMFluor probes are permeable to the blood-brain barrier, and, upon systematic injection, enable real-time magnetic resonance imaging and positron emission tomography-computed tomography imaging of the Aβ biodistribution in the hippocampus and cerebral cortex, and accurately differentiate the brains of living Alzheimer's disease mouse models from wild-type controls. We further demonstrate the ability of QMFluor probes to reach the brain after intravenous injection in a large animal model. This strategy expands the toolbox of probes for in vivo visualization of amyloids in Alzheimer's disease pathological analysis, drug screening and clinical applications.

Programmable Manually Powered Microfluidics for Rapid Point-of-Care Diagnosis of Urinary Tract Infection

Point-of-care testing (POCT) for urinary tract infection (UTI) holds significant importance in the field of disease prevention and control, as well as the advancement of personalized precision medicine. However, conventional methods for detecting UTIs continue to face challenges such as time-consuming and labor-intensive detection processes, and reliance on specialized equipment and personnel rendering them unsuitable for point-of-care applications, especially in resource-limited areas. Here, we propose a novel flexible programmable manually powered microfluidic (FPM) for rapid point-of-care diagnosis of UTIs. For the first time, the proposed FPMs was achieved through a combined strategy of laser printing, cutting, and laminating, with the entire process completed in under 15 min at a cost of less than $0.5, which effectively circumvent the traditionally time-consuming and labor-intensive soft lithography techniques. By incorporating a modular structure-based design concept, we successfully developed various types of portable FPMs with functionalities including parallel pumping, simultaneous releasing, quantitative dispensing, sequential releasing, cyclic motion of multiple liquids and concentration gradient generating. As a proof-of-concept demonstration, we initially employed a high-throughput parallel dispensing design to analyze six urinary biochemical markers within 1 min, presenting potential applicability for future at-home testing. We then integrated a manually powered concentration gradient generator with spatial confinement signal enhancement to enable rapid phenotypic antimicrobial susceptibility testing (AST) within three to 5 h, while achieving clinical diagnostic accuracy rates of up to 95.56%. Therefore, our proposed FPMs eliminate the need for external pumps or actuators and could serve as an affordable hand-held POCT tool for UTI diagnosis. Moreover, in resource-poor areas, they have potential utility as robust POCT devices addressing diverse rapid detection needs.

Semiconducting Open-Shell Radicals for Precise Tumor Activatable Phototheranostics

Semiconducting open-shell radicals (SORs) have promising potential for the development of phototheranostic agents, enabling tumor bioimaging and boosting tumorous reactive oxygen species (ROS). Herein, a new class of semiconducting perylene diimide (PDI), designated as PDI(Br)n with various numbers of bromine (Br) atoms modified on PDI's bay/ortho positions is reported. PDI(Br)n is demonstrated to transform into a radical anion, [PDI(Br)n]•-, in a reducing solution, with a typical g-value of 2.0022. Specifically, [PDI(Br)4/6]•- is generated in the weakly reductive tumor-mimicking solution and exhibits high stability in air. Quantum chemical kinetic simulation and ultrafast femtosecond transient absorption spectroscopy indicate that [PDI(Br)6]•- has a low π-π stacking energy (0.35 eV), a fast electron transfer rate (192.4 ps) and energy gap of PDI(Br)6 (ΔES1, T1 = 1.307 eV, ΔES1, T2 = 0.324 eV) respectively, which together result in excited-state charge transfer characters. The PDI(Br)6 nanoparticle radicals, [PDI(Br)6] NPs•-, specifically enable chemodynamic and type-I photodynamic ROS generation in tumors, including superoxide and hydroxyl radicals, which elicit immunogenic cell death effect. Also, [PDI(Br)6] NPs•- facilitate activatable bioimaging-guided therapy due to their photoacoustic signal at 808 nm and NIR-II emission at 1115 nm. The work paves the way for the design of SORs for precise cancer theranostics.

Near-Infrared Chemiluminescent Theranostics

Molecular chemiluminescence probes with near-infrared (NIR) emission offer promising benefits in deciphering complex pathological processes in a living system, as NIR chemiluminescence minimizes autofluorescence, enhances deep-tissue penetration, and improves signal-to-noise ratio. Molecular engineering using single-luminophore design and dual-luminophore design with intramolecular energy transfer provides ways to develop conventional chemiluminophore scaffolds into NIR chemiluminescence probes with ideal chemiluminescence quantum yield and half-life. By virtue of the structural diversity, 1,2-dioxetane-based NIR chemiluminophores with biomarker activity have been developed. This review summarizes the molecular design strategies of NIR chemiluminescence theranostic probes (NCTPs), followed by introducing activatable NCTPs with their biomedical applications for disease theranostics. Lastly, future perspectives and potential challenges of NIR chemiluminescence imaging in preclinical research and clinical translational potential are discussed.

Emerging nanomedicines for macrophage-mediated cancer therapy

Tumor-associated macrophages (TAMs) contribute to tumor progression by promoting angiogenesis, remodeling the tumor extracellular matrix, inducing tumor invasion and metastasis, as well as immune evasion. Due to the high plasticity of TAMs, they can polarize into different phenotypes with distinct functions, which are primarily categorized as the pro-inflammatory, anti-tumor M1 type, and the anti-inflammatory, pro-tumor M2 type. Notably, anti-tumor macrophages not only directly phagocytize tumor cells, but also present tumor-specific antigens and activate adaptive immunity. Therefore, targeted regulation of TAMs to unleash their potential anti-tumor capabilities is crucial for improving the efficacy of cancer immunotherapy. Nanomedicine serves as a promising vehicle and can inherently interact with TAMs, hence, emerging as a new paradigm in cancer immunotherapy. Due to their controllable structures and properties, nanomedicines offer a plethora of advantages over conventional drugs, thus enhancing the balance between efficacy and toxicity. In this review, we provide an overview of the hallmarks of TAMs and discuss nanomedicines for targeting TAMs with a focus on inhibiting recruitment, depleting and reprogramming TAMs, enhancing phagocytosis, engineering macrophages, as well as targeting TAMs for tumor imaging. We also discuss the challenges and clinical potentials of nanomedicines for targeting TAMs, aiming to advance the exploitation of nanomedicine for cancer immunotherapy.

Liquid Biopsy on Microfluidics: From Existing Endogenous to Emerging Exogenous Biomarkers Analysis

Liquid biopsy is an appealing approach for early diagnosis and assessment of treatment efficacy in cancer. Typically, liquid biopsy involves the detection of endogenous biomarkers, including circulating tumor cells (CTCs), extracellular vesicles (EVs), circulating tumor DNA (ctDNA), circulating tumor RNA (ctRNA), and proteins. The levels of these endogenous biomarkers are higher in cancer patients compared to those in healthy individuals. However, the clinical application of liquid biopsy using endogenous biomarker analysis faces challenges due to its low abundance and poor stability in circulation. Recently, a promising strategy involving the engineering of exogenous probes has been developed to overcome these limitations. These exogenous probes are activated within the tumor microenvironment, generating distinct exogenous markers that can be easily distinguished from background biological signals. Alternatively, these exogenous probes can be labeled with intrinsic endogenous biomarkers in vivo and detected in vitro after metabolic processes. In this review, we primarily focus on microfluidic-based liquid biopsy techniques that allow for the transition from analyzing existing endogenous biomarkers to emerging exogenous ones. First, we introduce common endogenous biomarkers, as well as synthetic exogenous ones. Next, we discuss recent advancements in microfluidic-based liquid biopsy techniques for analyzing both existing endogenous and emerging exogenous biomarkers. Lastly, we provide insights into future directions for liquid biopsy on microfluidic systems.

A Lifetime Nanosensor for In Vivo pH Quantitative Imaging and Monitoring

Non-invasive, in vivo quantitative imaging for long-term biomarker monitoring is crucial for elucidating disease mechanisms, advancing precision medicine, and transforming diagnostics and therapeutic strategies. However, developing chemical sensors for sustained in vivo quantitative monitoring despite sensor concentration fluctuations, excitation variability, and tissue interference remains a major challenge. Here, a long-lifetime nanosensor based on a lanthanide-dye nanocomposite is presented that overcomes these limitations, enabling precise quantitative in vivo pH monitoring. Benefiting from a 64-fold reversible change in the dye's molar extinction coefficient, this nanosensor enables the dynamic tuning of reversible non-radiative energy transfer (RNET) efficiency (6.42%-35.23%) and luminescence lifetime (265-383 µs). This nanosensor enables 4 h of monitoring of gastrointestinal pH dynamics in mice following proton pump inhibitor (PPI) administration, offering new insights into pharmacodynamic effects across different administration routes and dosages and inter-individual variability in drug efficacy. Moreover, coordination with lanthanide nanocrystals induces a significant shift in the dye's pKa, highlighting the importance of nanomaterial interface engineering. This work establishes a versatile platform for in vivo diagnostics and therapeutic monitoring, marking a significant step forward in precision medicine.

Renal-Clearable Molecular Reporters for Near-Infrared Fluorescence Imaging and Urinalysis of Pulmonary Metastatic Tumor

Despite approximately 40% of all patients with cancer developing pulmonary metastases in the course of their disease, it remains a diagnostic challenge in clinical practice. Herein, we propose a fluorogenic probe (CPRG) with gamma-glutamyl transferase (GGT)-triggered signal turn-on for near-infrared fluorescence imaging (NIRF) and urinalysis of orthotopic pulmonary metastatic tumors in living mice. CPRG comprised four key moieties: a GGT-reactive moiety, a hemicyanine-based signal unit, a polyethylene glycol linker, and an active tumor targeting moiety. Such a tailored probe is intrinsically nonfluorescent and only activates its NIRF signals in the presence of GGT. After intratracheal administration into the lungs of living tumor-bearing mice, CPRG can efficiently accumulate in the pulmonary tumors and sensitively turn-on the NIRF signal for real-time imaging. Relying on the high renal clearance efficiency (∼70% ID), it can be rapidly excreted through kidneys for urinalysis and assessed by the chemotherapeutic efficacy of cisplatin. This study not only reports fluorogenic tracers for imaging of pulmonary metastatic tumors but also provides guidelines for the development of molecular probes for companion diagnosis of metastatic cancer.

Recent Advances in Enzyme-Activated Dual-Locked Probes for Biological Applications

Enzymes catalyze reactions involved in diverse physiological, pathological, and pharmacological processes. By employing the optical probe, fluorescence imaging enables non-invasive, real-time detection and assessment of disease states based on enzymatic activity. However, most enzyme-activated probes are single-locked probes that respond to a single biomarker. In comparison to single-locked probes, enzyme-activated dual-locked probes can effectively minimize the occurrence of false-positive signals, circumvent the problem of low specificity associated with biologically active substances, and facilitate precise imaging. This review systematically summarizes the design and application of dual-locked probes in disease diagnosis, with the aim of providing inspiration for researchers in the field.

Unlocking the Power of Photothermal Agents: A Universal Platform for Smart Immune NIR-Agonists for Precise Cancer Therapy

Selective ablation of tumor cells allows safe eradication, thereby minimizing off-target damage, while specifically inducing immunogenic cell death (ICD) rather than commonly non-immunogenic apoptosis of tumor cells enables activation of anti-tumor immune response against residual cancer cells, including metastatic lesions. Herein, we present a general strategy leveraging a novel photothermal agent (PTA) that concomitantly enables precise tumor killing and activation of anti-tumor immunity. The unique PTA scaffold exhibits unexpected inherent endoplasmic reticulum (ER)-targeting capability and potent near-infrared (NIR) photothermal activity, inducing NIR-controlled immunogenic pyroptosis in various tumor cell lines via targeting ER stress in an oxygen-independent manner. Moreover, both ER-targeting and NIR-activity of our scaffold can be modulated on demand by chemical caging/uncaging, allowing quick activation with diverse biological and bioorthogonal molecular triggers. The potency of this universal platform is demonstrated via its application to develop a membrane protein-activatable NIR-agonist that selectively activates ICD in tumor sites while priming anti-tumor immunity, minimizing off-target effects and enhancing efficacy against mouse breast tumors. This versatile approach could lead to customization of various personalized and effective immune NIR-agonists for specific photoimmunotherapy applicable to diverse solid tumors.

Optical-magnetic Imaging for Optimizing Lymphodepletion-TIL Combination Therapy in Breast Cancer

PURPOSE

Lymphodepletion before tumor-infiltrating lymphocytes (TIL) infusion can activate the immune system, enhance the release of homeostatic cytokines, and decrease the number of immunosuppressive cells. This process is crucial for improving the therapeutic efficacy of TIL therapy. However, the challenge of in vivo assessing TILs targeting tumors limits the optimization of lymphodepleting conditioning regimen (LDC).

PROCEDURES

This study aims to employ magnetic particle imaging (MPI) and fluorescence molecular imaging (FMI) to monitor TIL biodistribution in vivo and optimize LDC in triple-negative breast cancer TIL therapy. MPI provides quantitative imaging capabilities without depth limitations, effectively complementing the high sensitivity of FMI. The efficacy of different LDCs in enhancing TIL therapy was assessed using FMI, and MPI quantified the number of TILs accumulated in the 4T1 tumor.

RESULTS

TILs preserved viability, phenotypes, and anti-tumor efficacy after being labeled with superparamagnetic iron oxide and fluorescence dye DiR. The dual-modality imaging system effectively discerned variations in LDC treatments that enhanced TIL therapy. Compared to TIL monotherapy, lymphodepletion with TIL therapy improves tumor dual-modality imaging signal intensity, increases the expression of monocyte chemotactic protein-1 in serum and tumor tissue, and enhances the therapeutic effect of TILs.

CONCLUSION

Our results confirm the utility of optical-magnetic dual-modality imaging for tracking the biodistribution of TILs in vivo. With the help of optical-magnetic dual-modality imaging, we successfully optimize TIL combination therapy. Optical-magnetic dual-modality imaging provides a new approach to develop personalized immunotherapy strategies and mine potential therapeutic mechanisms for TIL.

PhotoChem Interplays: Lighting the Way for Drug Delivery and Diagnosis

Light, a non-invasive tool integrated with cutting-edge nanotechnologies, has driven transformative advancements in imaging-based diagnosis and drug delivery for cancer and bacterial treatments. This review discusses recent progress in these areas, beginning with emerging imaging technologies. Unlike traditional photosensors activated by visible light, alternative energy sources such as near-infrared (NIR) light, X-rays, and ultrasound have been extensively investigated to activate various photosensors, achieving high sensitivity, wavelength versatility, and spatial resolution for deep-tissue imaging. Moreover, to address challenges like tissue autofluorescence in real-time fluorescence imaging, afterglow luminescent nanoparticles are being developed by integrating these alternative energy sources for real-time imaging and sensing in deep tissue for precise cancer diagnosis and treatment beyond superficial tissues. In addition to deep tissue imaging, light-responsive nanomedicines are revolutionizing anticancer and antimicrobial phototherapy by enabling spatially and temporally controlled drug release. These smart nanoparticles are engineered to release therapeutic cargo at target sites in response to microenvironmental cues specific to tumors or infections. In anticancer phototherapy, these nanoparticles facilitate controlled drug release via photoisomerization, photothermal, and photodynamic processes. To enhance circulation time and specific targeting, biomimetic nanoparticles, which mimic natural anti-tumor responses by our body, have attracted increasing attention. In antimicrobial phototherapy, research has been focused on the chemical modification of the photosensitizer to enable targeted drug delivery. An intriguing strategy has recently emerged involving the development of "pro-photosensitizers" that are specifically activated within bacterial cells upon light irradiation, offering a high margin of safety. These advancements leverage photochemical reactions and nanotechnology to enhance precision therapy and diagnosis in addressing critical health challenges.

An enzymatic cleavage-triggered minimally invasive nanosensor for urine-based detection of early atherosclerosis

Timely detection of early atherosclerosis (AS) is crucial for improving cardiovascular outcomes, creating a growing demand for diagnostic tools that are simple, sensitive, and cost-effective. Here, we introduce a synthetic nanosensor for early AS detection that leverages the fluorescence and renal clearance properties of carbon quantum dots (CQDs). This nanosensor, designed to respond to the proteolytic activity of AS-associated dysregulated enzymes, entails CQDs as signal reporters to convert AS-associated proteolytic activity to fluorometric readings enabling a sensitive and cost-effective urine-based assay for early AS detection. Our findings demonstrated that the nanosensor provided distinct signals in atherosclerotic versus healthy mice at early AS stages, indicating its diagnostic potential. Moreover, toxicity tests showed no notable adverse effects, supporting its safety for diagnostic applications. This minimally invasive diagnostic approach could facilitate personalized therapy design and continuous efficacy assessment. It is expected that such a modular nanosensor platform can be integrated with simple urine tests to offer cost-effective detection of various diseases.

Aggregation-Mediated Photoacoustic/NIR-II and Photodynamic Properties of pH-Reversible Thiopyrylium Agents: A Computational and Experimental Approach

Aggregation profoundly influences the photophysical properties of molecules. Here, a new series of thiopyrylium-based hemicyanine near-infrared II (NIR-II) fluorophores is developed by meticulously adjusting their aggregation states. Notably, the star molecule HTPA exhibits a remarkable pH-responsive behavior and a significant increase in photoacoustic (PA) intensity when aggregated. Additionally, their behavior and pH reversibility during aggregation formation are systematically investigated, including computational optimization, femtosecond transient absorption spectroscopy, NMR analysis, and single crystal analysis. Finally, an innovative "off " nanoparticle specifically is designed for effective tumor-targeted PA/NIR-II dual-modal imaging and photodynamic therapy by utilizing a pH-responsive polymer. The signal-to-background ratio (SBR) of PA signals significantly increased to 169 in the region of interest (ROI) in the mouse model when irradiated at 1064 nm. These findings not only provide a promising avenue for future studies of NIR-II small molecules but also pave the way for significant advances in the field of integrated cancer diagnosis and therapy.

AND-gated protease-activated nanosensors for programmable detection of anti-tumour immunity

The forward design of biosensors that implement Boolean logic to improve detection precision primarily relies on programming genetic components to control transcriptional responses. However, cell- and gene-free nanomaterials programmed with logical functions may present lower barriers for clinical translation. Here we report the design of activity-based nanosensors that implement AND-gate logic without genetic parts via bi-labile cyclic peptides. These actuate by releasing a reporter if and only if cleaved by a specific pair of proteases. AND-gated nanosensors that detect the concomitant activity of the granzyme B protease secreted by CD8 T cells and matrix metalloproteinases overexpressed by cancer cells identify the unique condition of cytotoxic T cell killing of tumour cells. In preclinical mouse models, AND-gated nanosensors discriminate tumours that are responsive to immune checkpoint blockade therapy from B2m-/- tumours that are resistant to it, minimize signals from tissues without co-localized protease expression including the lungs during acute influenza infection, and release a reporter locally in tissue or distally in the urine for facile detection.

Dual-Locked Fluorescence Probe for Monitoring the Dynamic Transition of Pulmonary Macrophages

Pulmonary macrophages undergo dynamic changes in population, proportion, and polarization during respiratory diseases. Monitoring these changes is critical for understanding their roles in pathology, improving the diagnosis, and guiding drug development. However, current analytic methods based on tissue biopsy are invasive and static, limiting their ability to provide such dynamic information. Herein, we report a dual-locked macrophage-specific renal-clearable probe (DMRPNOCas) for the dynamic monitoring of pulmonary macrophages during influenza A virus (IAV) infection. DMRPNOCas activates fluorescence in the presence of two biomarkers (caspase-1 and NO) only coexpressed by M1 macrophages. To optimize the NO reactivity, the scaffold of DMRPNOCas is screened from the hemicyanine derivatives with an o-phenylenediamine group positioned differently on the indole ring. Notably, the para-substituted o-phenylenediamine demonstrates a higher NO-activated fluorescence compared to its meta-substituted counterpart. This enhancement, as revealed by quantum chemical calculations, is attributed to differential inhibition of twisted intramolecular charge transfer induced by the NO reaction. DMRPNOCas specifically distinguishes M1 macrophages from other leukocytes including T cells, neutrophils, and M2 macrophages, a capability unmatched by single-locked control probes and other reported probes. Consequently, DMRPNOCas enables in vivo dynamic monitoring of pulmonary macrophages, uncovering extensive recruitment and M1 polarization of monocyte-derived macrophages within 48 h of IAV infection. This process is accompanied by a significant reduction in alveolar macrophages. These findings provide new insights into macrophage-mediated pulmonary inflammation and underscore the potential of dual-locked probes for precise diagnosis and monitoring of pathological processes.

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.

Non-invasive in vivo monitoring of PROTAC-mediated protein degradation using an environment-sensitive reporter

Proteolysis targeting chimeras (PROTACs) represent a groundbreaking therapeutic technology for selectively degrading proteins of interest (POIs). The structural variations in PROTACs unpredictably influence their protein degradation efficiency, which is predominantly assessed by quantifying POIs abundance through western blotting. This approach, however, falls short of enabling non-invasive monitoring of protein degradation within living cells let alone assessing directly the degradation effects in vivo. Herein, we develop an environment-sensitive reporter (ESR) for the quantification of protein degradation events triggered by PROTACs in vivo. By simultaneously integrating POIs targeting ligand and an environment-sensitive fluorophore, the ESR signals exhibit a strong fluorescence correlation with the levels of POIs. This non-invasive monitoring reporter offers a high-throughput and convenient way to screen POIs targeting degraders and predict PROTACs-mediated therapeutic outcomes in mouse models. These properties suggest the potential of ESR strategy as a general modular scheme for non-invasive quantification of protein degradation of cancer-related therapeutic targets.

Molecular probes for in vivo optical imaging of immune cells

Advancing the understanding of the various roles and components of the immune system requires sophisticated methods and technology for the detection of immune cells in their natural states. Recent advancements in the development of molecular probes for optical imaging have paved the way for non-invasive visualization and real-time monitoring of immune responses and functions. Here we discuss recent progress in the development of molecular probes for the selective imaging of specific immune cells. We emphasize the design principles of the probes and their comparative performance when using various optical modalities across disease contexts. We highlight molecular probes for imaging tumour-infiltrating immune cells, and their applications in drug screening and in the prediction of therapeutic outcomes of cancer immunotherapies. We also discuss the use of these probes in visualizing immune cells in atherosclerosis, lung inflammation, allograft rejection and other immune-related conditions, and the translational opportunities and challenges of using optical molecular probes for further understanding of the immune system and disease diagnosis and prognosis.

Bifunctional Nanoassembly Enables Metabolism-Driven Microfluidic Blood Screening Guided by MRI Localization for Cancer Monitoring

Early detection and precise tumor localization are critical for improving treatment outcomes and enabling more targeted and minimally invasive therapies as biotechnology evolves. However, endogenous biomarkers from early lesions face significant challenges, such as short circulation times and blood dilution, which hinder early diagnostic efforts. In this study, we present a multimodal nanosensor specifically engineered to target cancer by responding to CD44 and tumor-associated enzymes within the microenvironment. Following systemic administration, the nanosensor selectively accumulates at the disease site, delivering hexaminolevulinate (HAL) to produce protoporphyrin IX (PpIX) as a synthetic biomarker, thus amplifying disease signals for analysis via a microfluidics-based device. Concurrently, embedded Gd2O3 nanoclusters facilitate tumor visualization through magnetic resonance imaging (MRI). Beyond tumor diagnosis, this innovative methodology supports the multimodal monitoring of drug response through the assessment of blood reporter signals and MRI imaging. This multifunctional system addresses critical limitations in traditional cancer diagnostics, which typically rely on sequential blood biomarker tests, followed by imaging. Our approach enhances diagnostic efficiency, minimizes the need for invasive procedures, and promotes more accurate and personalized cancer care.

Dual-Locked Enzyme-Activatable Fluorescence Probes for Precise Bioimaging

Real-time visualization of endogenous enzymes not only helps reveal the underlying biological principles but also provides pathological information for cancer/disease diagnosis and even treatment guidance. To this end, enzyme-activatable fluorescence probes are frequently fabricated that turn their fluorescence signals "on" exclusively at the enzyme-rich region, thus enabling noninvasive and real-time imaging of enzymes of interest at the molecular level with superior sensitivity and selectivity. However, in a complex biological context, commonly used single enzyme-activatable (i.e., single-locked) probes may suffer from "false positive" signals at healthy tissues and be insufficient to accurately indicate the occurrence of certain diseases. Therefore, dual-locked fluorescence probes have been promoted to address these issues. Using dual enzymes (or an enzyme with another stimulus) as "keys", they permit simultaneous detection of distinct biomarkers, offering significantly enhanced imaging precision toward certain biological events. Considering that recent reviews on these probes remain scarce, we thus provide this review. We summarize the recent progress, particularly highlighting the breakthroughs in the last three years, and discuss the challenges in this field.

Near-Infrared Photothermally Assisted Nanoprobes Boost Signal Amplification for Fluorescence Imaging and Urinalysis of Tumor

Early diagnosis of tumors allows effective treatment of primary cancers through localized therapeutic interventions. However, developing diagnostic tools for sensitive, simple, and early tumor (especially less than 2 mm in diameter) detection remains a challenge. Herein, we presented a biomarker-activatable nanoprobe that enabled a near-infrared (NIR) photothermally amplified signal for fluorescence imaging and urinalysis of tumor. This activatable nanoprobe was constructed by encapsulating renal-clearable NIR ZW800 dyes into a CuS@mSiO2 core-shell nanoparticle with hyaluronic acid. The nanoprobes could accumulate at the tumor site and respond to tumor-associated hyaluronidase, undergoing in situ enzyme-catalyzed decapsulation to release renal-clearable ZW800 dyes for fluorescence imaging and uranalysis of tumor in living mice. Notedly, with the aid of NIR laser irradiation, the photothermal effect of CuS core boosted signal amplification for tumor diagnosis via photothermally enhanced ZW800 release, providing high specificity and sensitivity. On account of the biomarker specificity and the spatiotemporally controlled NIR irradiation, the nanoprobes could selectively activate their NIR fluorescence (NIRF) signal to visualize tumors in living mice and allow for the easy translation of the nanoprobe as artificial urinary biomarker probes for in vitro diagnosis of tumor progression. In 4T1 tumor-bearing mice models, the activatable nanoprobes enabled ultrasensitive detection of tumors (1.9 mm in diameter). This study offers a noninvasive and photothermally signal-amplified approach for early tumor diagnosis via NIRF imaging or simple urine tests.

Recent advances and design strategies for organic afterglow agents to enhance autofluorescence-free imaging performance

Long-lasting afterglow luminescence imaging that detects photons slowly being released from chemical defects has emerged, eliminating the need for real-time photoexcitation and enabling autofluorescence-free in vivo imaging with high signal-to-background ratios (SBRs). Organic afterglow nano-systems are notable for their tunability and design versatility. However, challenges such as unsatisfactory afterglow intensity, short emission wavelengths, limited activatable strategies, and shallow tissue penetration depth hinder their widespread biomedical applications and clinical translation. Such contradiction between promising prospects and insufficient properties has spurred researchers' efforts to improve afterglow performance. In this review, we briefly outline the general composition and mechanisms of organic afterglow luminescence, with a focus on design strategies and an in-depth understanding of the structure-property relationship to advance afterglow luminescence imaging. Furthermore, pending issues and future perspectives are discussed.

Renal Clearable Chiral Manganese Oxide Supraparticles for In Vivo Detection of Metalloproteinase-9 in Early Cancer Diagnosis

In this study, polypeptide TGGGPLGVARGKGGC-induced chiral manganese dioxide supraparticles (MnO2 SPs) are prepared for sensitive quantification of matrix metalloproteinase-9 (MMP-9) in vitro and in vivo. The results show that L-type manganese dioxide supraparticles (L-MnO2 SPs) exhibited twice the affinity for the cancer cell membrane receptor CD47 (cluster of differentiation, integrin-associated protein) than D-type manganese dioxide supraparticles (D-MnO2 SPs) to accumulate at the tumor site after surface modification of the internalizing arginine-glycine-aspartic acid (iRGD) ligand, specifically reacting with the MMP-9, disassembling into ultrasmall nanoparticles (NPs), and efficiently underwent renal clearance. Furthermore, L-MnO2 facilitates the quantification of MMP-9 in mouse tumor xenografts, as demonstrated by circular dichroism (CD) and magnetic resonance imaging (MRI) within 2 h. A strong linear relationship is observed between MMP-9 concentration and both CD and MRI intensity, ranging from 0.01 to 10 ng mL-1. The corresponding limits of detection (LOD) are 0.0054 ng mL-1 for CD and 0.0062 ng mL-1 for MRI, respectively. hese SPs provide a new approach for exploring chiral advanced biosensors for early diagnosis of cancer.

Nanoparticle Transport in Proximal Tubules with Rhabdomyolysis-Induced Necrosis

Renal-clearable engineered nanoparticles are being explored for their potential to deliver therapeutic agents for kidney disease treatment. A fundamental understanding of how these nanoparticles accumulate in diseased kidneys at the cellular level is essential to enhance their effectiveness and minimize side effects on adjacent healthy tissues. Herein, we report that the accumulation of glutathione-coated, near-infrared emitting gold nanoparticles (GS-AuNPs) correlates strongly with the necrotic stages of injured proximal tubular cells. Using a rhabdomyolysis-induced acute kidney injury (AKI) mouse model, we observed that GS-AuNPs were significantly accumulated in the extracellular lumen of proximal tubular epithelial cells (PTECs) at advanced necrotic stage, where cellular debris and released intracellular contents impeded their clearance. In contrast, during early necrosis, GS-AuNPs were still cleared through the unobstructed lumen. Additionally, intracellular uptake of GS-AuNPs was significantly reduced across all necrotic stages. These findings underscore the need for new strategies to design nanoparticles that can effectively target and be taken up by the diseased tubular cells before extensive necrosis occurs; so that nanoparticle-mediated drug delivery for kidney disease treatment can be achieved with desired efficacy and precision.

Molecular Imaging of Renin Activity using Fluorogenic Nanoprobes for Precision Antihypertensive Therapy

Life-threatening hypertension remains inadequately controlled in clinics due to its heterogeneous renin levels. Rapid stratification of hypertension through renin analysis is crucial for effective personalized treatment, yet an ultrasensitive detection approach is currently lacking. Here, we report activatable renin nanoprobes (ARNs) for non-invasive and ultrasensitive profiling of renin activity and guiding antihypertensive treatment decision through near-infrared fluorescence (NIRF) in vivo imaging and in vitro urinalysis. ARNs are intrinsically non-fluorescent due to NIRF reporter connected to a gold nanocluster through a renin-responsive peptide. In hyperreninemia mouse models, ARNs specifically react with renin to liberate the renal clearable NIRF reporter for accurate renin detection that outperforms the gold standard radioimmunoassay. Such specific and sensitive detection also enables imaging-based high-throughput screening of antihypertensive drugs. In hypertensive rat models, ARNs enable ultrasensitive detection of both plasma and urinary renin, facilitating renin-guided precision treatment and significantly improving hypertension control rate (90 % versus 58 %). Our nanoprobe platform holds great potential for assisting clinicians in rapidly and accurately classifying hypertensive patients and improving outcomes through tailored treatment selection.

Self-Activated Cascade-Tailored Small Molecule for Cancer Therapy, Companion Diagnostics, and "Theranostic Correlation" Evaluation

Companion diagnostics (CDx) have emerged as valuable tools for monitoring biomarkers essential for drug activation and therapeutic response, enabling personalized treatment strategies. However, the current FDA-approved CDx is limited to in vitro testing, making it challenging to assess the real-time drug efficacy. Moreover, evaluation of treatment responses solely based on drug release or activation may disregard tumor heterogeneity. To address these challenges, we have developed a cascade-responsive small molecule Cbl-DEVD-Hcy for simultaneous cancer therapy and the timely evaluation of therapy effectiveness in vivo. Upon cleavage by tumor-cell-overexpressed carboxylesterase, chlorambucil (Cbl) can be released to induce tumor cell apoptosis and activate caspase-3. This activation triggers the production of the near-infrared dye Hcy-NH2, generating both near-infrared fluorescence and photoacoustic signals for monitoring the apoptosis process. The excellent "theranostic correlation" between the imaging signal and therapeutic response, as demonstrated in orthotopic breast tumors, highlights the potential of Cbl-DEVD-Hcy for effective tumor therapy and precise CDx in the body.

Sonodynamic Nano-LYTACs Reverse Tumor Immunosuppressive Microenvironment for Cancer Immunotherapy

Extracellular and transmembrane proteins, which account for the products of approximately 40% of all protein-encoding genes in tumors, play a crucial role in shaping the tumor immunosuppressive microenvironment (TIME). While protein degradation therapy has been applied to membrane proteins of cancer cells, it has rarely been extended to immune cells. We herein report a polymeric nanolysosome targeting chimera (nano-LYTAC) that undergoes membrane protein degradation on M2 macrophages and generates a sonodynamic effect for combinational cancer immunotherapy. Nano-LYTAC is found to have higher degradation efficacy to the interleukin 4 receptor (IL-4R) compared to traditional inhibitors. More importantly, it is revealed that the effect of nano-LYTAC on the function of the M2 macrophage is concentration-dependent: downregulating CD206 expression and interleukin 10 (IL-10) secretion from M2 macrophages at low concentration, while triggering their apoptosis at high concentration. Moreover, nano-LYTAC is found to possess long tumor retention (>48 h), allowing for multiple sonodynamic treatments with a single dose. Such a synergistic sonodynamic immunotherapy mediated by nano-LYTAC effectively reprograms the TIME via inhibiting the functions of M2 macrophages and regulatory T cells (Tregs), as well as promoting the maturation of dendritic cells (DCs) and tumor infiltration of T effector cells (Teffs), completely suppressing tumor growth, inhibiting pulmonary metastasis, and preventing recurrence under preclinical animal models.

A Bicyclic Dioxetane Chemiluminescence Nanoprobe for Peroxynitrite Imaging in Vivo

Peroxynitrite (ONOO-) is a critical biomarker associated with a wide array of diseases including cancer, inflammatory conditions, and neurodegenerative disorders. This study introduces an innovative chemiluminescence nanoprobe (CLNP) based on a bicyclic dioxetane structure, designed for highly sensitive and specific in vivo imaging of ONOO-. Our CLNP demonstrates exceptional capabilities in generating high-contrast imaging of disease lesions, with applications verified across tumor models, acute inflammation, and acute liver injury scenarios. Key findings highlight the probe's rapid response to oxidative species, superior tissue penetration, and high signal-to-noise ratio, underscoring its potential for real-time diagnostic applications. This work represents an important advance in the field of diagnostic imaging using CL probes, offering promising avenues for the early detection and treatment of ONOO--related pathologies.

A Multifunctional Peptide Nucleic Acid/Peptide Copolymer-Based Dual-Mode Biosensor with Macrophage-Hitchhiking for Enhanced Tumor Imaging and Urinalysis

Biosensors are capable of diagnosing tumors through imaging in vivoor liquid biopsy, but they face the challenges of inefficient delivery into tumor sites and the lack of reliable tumor-associated biomarkers. Herein, we constructed a dual-mode biosensor based on a multifunctional peptide nucleic acid (PNA)/peptide copolymer and DNA tetrahedron for tumor imaging and urinalysis. The biosensor could enter the cancer cells to initiate a microRNA-21-specific catalytic hairpin assembly reaction after cleavage by matrix-metalloprotease (MMP) in the tumor microenvironment, and the MMP cleavage product was released into the bloodstream and then was filtered out by the kidney. As PNA was a synthetic DNA analogue that could not be degraded by nucleases and proteases, it could serve as a reliable synthetic biomarker and be easily detected by high-performance liquid chromatography in urine. Importantly, the biosensor was hitchhiked on the macrophage membrane to realize efficient delivery in the depth of tumor utilizing the macrophage ability of actively homing to the tumor site and infiltrating into the tumor. The results indicated that the signal output of the biosensor was improved remarkably and mice with a tumor volume as little as 30-40 mm3 could be reliably discriminated through urine assay. This innovative macrophage-hitchhiking dual-mode biosensor holds a great potential as a non-invasive and convenient tool for tumor diagnosis and tumor progression evaluation.

AND-Gate Logic Förster Resonance Energy Transfer/Magnetic Resonance Tuning Nanoprobe for Programmable Antitumor Immunity Imaging

Simultaneous detection of different biomarkers related to the spatiotemporally dynamic immune events is of particular importance for the accurate evaluation of antitumor immune effects. Here, we have developed an AND-gate logic dual resonance energy transfer nanoprobe (named DRET) for dynamic monitoring of programmed CD8+ T cell activation and tumor cell apoptosis. Immunotherapy-induced granzyme B secretion from CD8+ T cells and the subsequent caspase-3 release from apoptotic tumor cells individually activate one of the tiers of the "AND-gate" logic DRET. The resulting fluorescence recovery and magnetic resonance T1 enhancement can be used for precise immunomodulatory drug screening, early efficacy prediction, and immune stratification. Particularly, not only "Responders" can be distinguished from "Non-responders", but also "Acquired resistance" can be identified from "Maintain responders", providing a novel approach to put forward the accurate evaluation of antitumor immunity.

Dual-Activated Photoacoustic Probe for Reliably Detecting Hydroxyl Radical in Ischemic Cardiovascular Disease in Mouse and Human Samples

Cardiovascular disease (CVD) is a chronic disease characterized by the accumulation of lipids and fibrous tissue within the arterial walls, potentially leading to vascular obstruction and an increased risk of heart disease and stroke. Hydroxyl radicals play a significant role in the formation and progression of CVD as they can instigate lipid peroxidation, resulting in cellular damage and inflammatory responses. However, precisely detecting hydroxyl radicals in CVD lesions presents significant challenges due to their high reactivity and short lifespan. Herein, we present the development and application of a novel activatable optical probe, Cy-OH-LP, designed to detect hydroxyl radicals in lipid-rich environments specifically. Built on the Cy7 molecular skeleton, Cy-OH-LP exhibits near-infrared absorption and fluorescence characteristics, and its specific response to hydroxyl radicals enables a turn-on signal in both photoacoustic and fluorescence spectra. The probe demonstrated excellent selectivity and stability in various tests. Furthermore, Cy-OH-LP was successfully applied in an in vivo model to detect hydroxyl radicals in mouse models, providing a potential tool for diagnosing and monitoring AS. The biosafety of Cy-OH-LP was also verified, showing low cytotoxicity and no significant organ damage in mice. The findings suggest that Cy-OH-LP is a promising tool for the specific detection of hydroxyl radicals in lipid-rich environments, providing new possibilities for research and clinical applications in the field of oxidative stress-related diseases.

Blood-Brain Barrier-Penetrative Fluorescent Anticancer Agents Triggering Paraptosis and Ferroptosis for Glioblastoma Therapy

Currently used drugs for glioblastoma (GBM) treatments are ineffective, primarily due to the significant challenges posed by strong drug resistance, poor blood-brain barrier (BBB) permeability, and the lack of tumor specificity. Here, we report two cationic fluorescent anticancer agents (TriPEX-ClO4 and TriPEX-PF6) capable of BBB penetration for efficient GBM therapy via paraptosis and ferroptosis induction. These aggregation-induced emission (AIE)-active agents specifically target mitochondria, effectively triggering ATF4/JNK/Alix-regulated paraptosis and GPX4-mediated ferroptosis. Specifically, they rapidly induce substantial mitochondria-derived vacuolation, accompanied by reactive oxygen species generation, decreased mitochondrial membrane potential, and intracellular Ca2+ overload, thereby disrupting metabolisms and inducing nonapoptotic cell death. In vivo imaging revealed that TriPEX-ClO4 and TriPEX-PF6 successfully traversed the BBB to target orthotopic glioma and initiated effective synergistic therapy postintravenous injection. Our AIE drugs emerged as the pioneering paraptosis inducers against drug-resistant GBM, significantly extending survival up to 40 days compared to Temozolomide (20 days) in drug-resistant GBM-bearing mice. These compelling results open up new venues for the development of fluorescent anticancer drugs and innovative treatments for brain diseases.

A Tumor-Homing Nanoframework for Synergistic Microwave Tumor Ablation and Provoking Strong Anticancer Immunity Against Metastasis

Microwave thermotherapy (MT) is a clinical local tumor ablation modality, but its applications are limited by its therapeutic efficacy and safety. Therefore, developing sensitizers to optimize the outcomes of MT is in demand in clinical practice. Herein, we engineered a special nanoframework (i.e., FdMI) based on a fucoidan-decorated zirconium metal-organic framework incorporating manganese ions and liquid physisorption for microwave tumor ablation. The monodisperse nanoframework exhibited both microwave thermal effects and microwave dynamic effects, which could effectively kill cancer cells by efficient intracellular drug delivery. Through fucoidan-mediated targeting of P-selectin in the tumor microenvironment (TME), the FdMI effectively accumulated in tumor regions, leading to significant eradication of orthotropic triple-negative breast cancer (TNBC) and aggressive Hepa1-6 liver tumors by the synergistic effects of microwave thermotherapy/dynamic therapy (MT/MDT). The eradication of primary tumors could activate systemic immune responses, which effectively inhibited distant TNBC tumors and lung metastasis of Hepa1-6 liver tumors, respectively. This work not only engineered nanoparticle sensitizers for tumor-targeted synergistic MT/MDT but also demonstrated that nanocarrier-based microwave tumor ablation could stimulate antitumor immunity to effectively inhibit distant and metastatic tumors, demonstrating the high potential for effectively managing advanced malignant tumors.

Facilely Achieving Near-Infrared-II J-Aggregates through Molecular Bending on a Donor-Acceptor Fluorophore for High-Performance Tumor Phototheranostics

Constructing J-aggregated organic dyes represents a promising strategy for obtaining biomedical second near-infrared (NIR-II) emissive materials, as they exhibit red-shifted spectroscopic properties upon assembly into nanoparticles (NPs) in aqueous environments. However, currently available NIR-II J-aggregates primarily rely on specific molecular backbones with intricate design strategies and are susceptible to fluorescence quenching during assembly. A facile approach for constructing bright NIR-II J-aggregates using prevalent donor-acceptor (D-A) molecules is still lacking. In this study, we present a facile method that transforms D-A molecules into J-aggregates by simply bending the molecule through introducing a methyl group, enabling high-performance NIR-II phototheranostics. The TAA-BT-CN molecule exhibits hypsochromic-shift absorption upon forming H-aggregated NPs, while the designed mTAA-BT-CN with a bent structure demonstrates a bathochromic shift of over 100 nm in absorption upon forming J-aggregated NPs, leading to much enhanced NIR-II emission beyond 1100 nm. With respect to its H-aggregated counterpart with the aggregation-caused quenching (ACQ) phenomenon, the J-aggregated mTAA-BT-CN NPs exhibit a 7-fold increase in NIR-II fluorescence owing to their aggregation-induced emission (AIE) property as well as efficient generation of heat and reactive oxygen species under 808 nm light excitation. Finally, the mTAA-BT-CN NPs are employed for whole-body blood vessel imaging using NIR-II technology as well as imaging-guided tumor phototherapies. This study will facilitate the flourishing advancement of J-aggregates based on prevalent D-A-type molecules.

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.

Hepatic Biotransformation of Renal Clearable Gold Nanoparticles for Noninvasive Detection of Liver Glutathione Level via Urinalysis

Renal clearable nanoparticles have been drawing much attention as they can avoid prolonged accumulation in the body by efficiently clearing through the kidneys. While much effort has been made to understand their interactions within the kidneys, it remains unclear whether their transport could be influenced by other organs, such as the liver, which plays a crucial role in metabolizing and eliminating both endogenous and exogenous substances through various biotransformation processes. Here, by utilizing renal clearable IRDye800CW conjugated gold nanocluster (800CW4-GS18-Au25) as a model, we found that although 800CW4-GS18-Au25 strongly resisted serum-protein binding and exhibited minimal accumulation in the liver, its surface was still gradually modified by hepatic glutathione-mediated biotransformation when passing through the liver, resulting in the dissociation of IRDye800CW from Au25 and biotransformation-generated fingerprint message of 800CW4-GS18-Au25 in urine, which allowed us to facilely quantify its urinary biotransformation index (UBI) via urine chromatography analysis. Moreover, we observed the linear correlation between UBI and hepatic glutathione concentration, offering us a noninvasive method for quantitative detection of liver glutathione level through a simple urine test. Our discoveries would broaden the fundamental understanding of in vivo transport of nanoparticles and advance the development of urinary probes for noninvasive biodetection.

Chemistry-Enabled Intercellular Enzymatic Labeling for Monitoring the Immune Effects of Cytotoxic T Lymphocytes In Vivo

Monitoring the effector function of cytotoxic T lymphocytes (CTLs) in vivo remains a great challenge. Here, we develop a chemistry-enabled enzymatic labeling approach to evaluate the tumor-specific immune response of CTLs by precisely monitoring the interaction between CTLs and tumor cells. Staphylococcus aureus sortase A (SrtA) is linked to the CTL surface through bioconjugate chemistry and then catalyzes the transfer of fluorescent-labeled substrate, 5-Tamra-LPETG, to CTLs. Meanwhile, the tumor cells are specifically decorated with N-terminal glycine residues (G5 peptide) through the inherent glycolmetabolism of cathepsin B-specific cleavable triacetylated N-azidoacetyl-d-mannosamine (CB-Ac3ManNAz) and click chemistry. After the infiltration of engineered CTLs into the tumor tissues, the immune-synapse-mediated specific interaction of CTLs and tumor cells leads to the accurate fluorescent labeling of tumor cells through the SrtA-catalyzed 5-Tamra-LPETG transfer. Therefore, the immune effect of CTLs as well as the performance of immune drugs can be determined, providing a novel strategy for pushing ahead immunotherapy.

Dual-Locked Enzyme-Activatable Bioorthogonal Fluorescence Turn-On Imaging of Senescent Cancer Cells

Bioorthogonal pretargeting optical imaging shows the potential for enhanced diagnosis and prognosis. However, the bioorthogonal handles, known for being "always reactive", may engage in reactions at unintended sites with their counterparts, resulting in nonspecific fluorescence activation and diminishing detection specificity. Meanwhile, despite the importance of detecting senescent cancer cells in cancer therapy, current methods mainly rely on common single senescence-associated biomarkers, which lack specificity for differentiating between various types of senescent cells. Herein, we report a dual-locked enzyme-activatable bioorthogonal fluorescence (DEBOF) turn-on imaging approach for the specific detection of senescent cancer cells. A dual-locked bioorthogonal targeting agent (DBTA) and a bioorthogonally activatable fluorescent imaging probe (BAP) are synthesized as the biorthogonal pair. DBTA is a tetrazine derivative dually caged by two enzyme-cleavable moieties, respectively, associated with senescence and cancer, which ensures that its bioorthogonal reactivity ("clickability") is only triggered in the presence of senescent cancer cells. BAP is a fluorophore caged by trans-cyclooctane (TCO), whose fluorescence is only activated upon bioorthogonal reaction between its TCO and the decaged tetrazine of DBTA. As such, the DEBOF imaging approach differentiates senescent cancer cells from nonsenescent cancer cells or other senescent cells, allowing noninvasive tracking of the population fluctuation of senescent cancer cells in the tumor of living mice to guide cancer therapies. This study thus provides a general molecular strategy for biomarker-activatable in vivo bioorthogonal pretargeting imaging with the potential to be applied to other imaging modalities beyond optics.

Dual-Locked Fluorescent Probes Activated by Aminopeptidase N and the Tumor Redox Environment for High-Precision Imaging of Tumor Boundaries

Clear delineation of tumor margins is essential for accurate resection and decreased recurrence rate in the clinic. Fluorescence imaging is emerging as a promising alternative to traditional visual inspection by surgeons for intraoperative imaging. However, traditional probes lack accuracy in tumor diagnosis, making it difficult to depict tumor boundaries accurately. Herein, we proposed an offensive and defensive integration (ODI) strategy based on the "attack systems (invasive peptidase) and defense systems (reductive microenvironment)" of multi-dimensional tumor characteristics to design activatable fluorescent probes for imaging tumor boundaries precisely. Screened out from a series of ODI strategy-based probes, ANQ performed better than traditional probes based on tumor unilateral correlation by distinguishing between tumor cells and normal cells and minimizing false-positive signals from living metabolic organs. To further improve the signal-to-background ratio in vivo, derivatized FANQ, was prepared and successfully applied to distinguish orthotopic hepatocellular carcinoma tissues from adjacent tissues in mice models and clinical samples. This work highlights an innovative strategy to develop activatable probes for rapid diagnosis of tumors and high-precision imaging of tumor boundaries, providing more efficient tools for future clinical applications in intraoperative assisted resection.

A hemicyanine-based near-infrared fluorescent probe with large Stokes shift for non-invasive bioimaging of brown adipose tissue

Brown adipose tissue (BAT), characterized by the presence of numerous mitochondria, plays a key role in metabolism and energy expenditure. Accurately reporting the presence and activation of BAT is beneficial to study obesity, diabetes, and other metabolic disorders. Near-infrared (NIR) fluorescence imaging has the advantages of high sensitivity, non-radioactivity, and simple operation. However, most NIR probes for BAT imaging exhibit small Stokes shifts, which may lead to self-quenching, reducing the signal-to-noise ratio, and introducing cross-talk. Herein, we rationally designed and synthesized a series of hemicyanine-based NIR fluorescent probes HCYBAT-1-3. Among them, HCYBAT-1 demonstrated favorable properties such as near-infrared emission (776 nm), large Stokes shift (139 nm), good biocompatibility and specific mitochondrial targeting (Pearson's colocalization coefficient of 0.87). Meanwhile, HCYBAT-1 was successfully employed to differentiate BAT from white adipose tissue (WAT). Quantitative analysis of NIR fluorescent images showed that HCYBAT-1 could be used for real-time monitoring of BAT activation in mice stimulated by norepinephrine (NE) and cold exposure. Overall, probe HCYBAT-1 showcased its efficacy in non-invasive evaluation of BAT metabolism in vivo with high selectivity and sensitivity.

Imaging-guided companion diagnostics in radiotherapy by monitoring APE1 activity with afterglow and MRI imaging

Companion diagnostics using biomarkers have gained prominence in guiding radiotherapy. However, biopsy-based techniques fail to account for real-time variations in target response and tumor heterogeneity. Herein, we design an activated afterglow/MRI probe as a companion diagnostics tool for dynamically assessing biomarker apurinic/apyrimidinic endonuclease 1(APE1) during radiotherapy in vivo. We employ ultrabright afterglow nanoparticles and ultrasmall FeMnOx nanoparticles as dual contrast agents, significantly broadening signal change range and enhancing the sensitivity of APE1 imaging (limit of detection: 0.0092 U/mL in afterglow imaging and 0.16 U/mL in MRI). We devise longitudinally and transversely subtraction-enhanced imaging (L&T-SEI) strategy to markedly enhance MRI contrast and signal-to-noise ratio between tumor and normal tissue of living female mice. The combined afterglow and MRI facilitate both anatomical and functional imaging of APE1 activity. This probe enables correlation of afterglow and MRI signals with APE1 expression, radiation dosage, intratumor ROS, and DNA damage, enabling early prediction of radiotherapy outcomes (as early as 3 h), significantly preceding tumor size reduction (6 days). By monitoring APE1 levels, this probe allows for early and sensitive detection of liver organ injury, outperforming histopathological analysis. Furthermore, MRI evaluates APE1 expression in radiation-induced abscopal effects provides insights into underlying mechanisms, and supports the development of treatment protocols.

Development of Granzyme B-targeted Smart Positron Emission Tomography Probes for Monitoring Tumor Early Response to Immunotherapy

Granzyme B is an immune-related biomarker that closely correlates with cytotoxic T lymphocytes (CTLs), and hence detecting the expression level of granzyme B can provide a dependable scheme for clinical immune response assessment. In this study, two positron emission tomography (PET) probes [18F]SF-M-14 and [18F]SF-H-14 targeting granzyme B are designed based on the intramolecular cyclization scaffold SF. [18F]SF-M-14 and [18F]SF-H-14 can respond to granzyme B and glutathione (GSH) to conduct intramolecular cyclization and self-assemble into nanoaggregates to enhance the retention of probe at the target site. Both probes are prepared with high radiochemical purity (>98%) and high stability in PBS and mouse serum. In 4T1 cells cocultured with T lymphocytes, [18F]SF-M-14 and [18F]SF-H-14 reach the maximum uptake of 6.71 ± 0.29 and 3.47 ± 0.09% ID/mg at 0.5 h, respectively, but they remain below 1.95 ± 0.22 and 1.47 ± 0.21% ID/mg in 4T1 cells without coculture of T lymphocytes. In vivo PET imaging shows that the tumor uptake in 4T1-tumor-bearing mice after immunotherapy is significantly higher (3.5 times) than that in the untreated group. The maximum tumor uptake of [18F]SF-M-14 and [18F]SF-H-14 in the mice treated with BEC was 4.08 ± 0.16 and 3.43 ± 0.12% ID/g, respectively, while that in the untreated mice was 1.04 ± 0.79 and 1.41 ± 0.11% ID/g, respectively. These results indicate that both probes have great potential in the early evaluation of clinical immunotherapy efficacy.

Aqueous Grown Quantum Dots with Robust Near-Infrared Fluorescence for Integrated Traumatic Brain Injury Diagnosis and Surgical Monitoring

Surgical intervention is the most common first-line treatment for severe traumatic brain injuries (TBIs) associated with high intracranial pressure, while the complexity of these surgical procedures often results in complications. Surgeons often struggle to comprehensively evaluate the TBI status, making it difficult to select the optimal intervention strategy. Here, we introduce a fluorescence imaging-based technology that uses high-quality silver indium selenide-based quantum dots (QDs) for integrated TBI diagnosis and surgical guidance. These engineered, poly(ethylene glycol)-capped QDs emit in the near-infrared region, are resistant to phagocytosis, and importantly, are ultrastable after the epitaxial growth of an aluminum-doped zinc sulfide shell in the aqueous phase that renders the QDs resistant to long-term light irradiation and complex physiological environments. We found that intravenous injection of QDs enabled both the precise diagnosis of TBI in a mouse model and, more importantly, the comprehensive evaluation of the TBI status before, during, and after an operation to distinguish intracranial from superficial hemorrhages, provide real-time monitoring of the secondary hemorrhage, and guide the decision making on the evacuation of intracranial hematomas. This QD-based diagnostic and monitoring system could ultimately complement existing clinical tools for treating TBI, which may help surgeons improve patient outcomes and avoid unnecessary procedures.

Smart Molecular Imaging and Theranostic Probes by Enzymatic Molecular In Situ Self-Assembly

Enzymatic molecular in situ self-assembly (E-MISA) that enables the synthesis of high-order nanostructures from synthetic small molecules inside a living subject has emerged as a promising strategy for molecular imaging and theranostics. This strategy leverages the catalytic activity of an enzyme to trigger probe substrate conversion and assembly in situ, permitting prolonging retention and congregating many molecules of probes in the targeted cells or tissues. Enhanced imaging signals or therapeutic functions can be achieved by responding to a specific enzyme. This E-MISA strategy has been successfully applied for the development of enzyme-activated smart molecular imaging or theranostic probes for in vivo applications. In this Perspective, we discuss the general principle of controlling in situ self-assembly of synthetic small molecules by an enzyme and then discuss the applications for the construction of "smart" imaging and theranostic probes against cancers and bacteria. Finally, we discuss the current challenges and perspectives in utilizing the E-MISA strategy for disease diagnoses and therapies, particularly for clinical translation.

Sucrose-Powered Liposome Nanosensors for Urinary Glucometer-Based Monitoring of Cancer

Timely detection of early-stage cancer holds immense potential in enhancing prognostic outcomes. There is an increasing desire for versatile tools to enable simple, sensitive, and cost-effective cancer detection. By exploiting the extraintestinal metabolic inertness and efficiency renal clearance of sucrose, we designed a liposome nanosensor using sucrose as a messenger to convert tumor-specific esterase activity into glucose meter readout, enabling economical and sensitive urinalysis for cancer detection in point-of-care testing (POCT). Our results demonstrate that the nanosensors exhibited significant signal differences between tumor-bearing and healthy mice in both orthotopic and metastatic tumor models. Additionally, efficient elimination of the nanosensors through the hepatobiliary pathway was observed with no significant toxicity. Such a non-invasive diagnostic modality significantly assists in personalized pharmacological treatment and follow-up efficacy assessment. We envision that this modular liposome nanosensor platform might be applied for economically detecting diverse diseases via a simple urinary test.

Leveraging Long-Distance Singlet-Oxygen Transfer for Bienzyme-Locked Afterglow Imaging of Intratumoral Granule Enzymes

Dual-locked activatable optical probes, leveraging the orthogonal effects of two biomarkers, hold great promise for the specific imaging of biological processes. However, their design approaches are limited to a short-distance energy or charge transfer mechanism, while the signal readout relies on fluorescence, which inevitably suffers from tissue autofluorescence. Herein, we report a long-distance singlet oxygen transfer approach to develop a bienzyme-locked activatable afterglow probe (BAAP) that emits long-lasting self-luminescence without real-time light excitation for the dynamic imaging of an intratumoral granule enzyme. Composed of an immuno-biomarker-activatable singlet oxygen (1O2) donor and a cancer-biomarker-activatable 1O2 acceptor, BAAP is initially nonafterglow. Only in the presence of both immune and cancer biomarkers can 1O2 be generated by the activated donor and subsequently diffuse toward the activated acceptor, resulting in bright near-infrared afterglow with a high signal-to-background ratio and specificity toward an intratumoral granule enzyme. Thus, BAAP allows for real-time tracking of tumor-infiltrating cytotoxic T lymphocytes, enabling the evaluation of cancer immunotherapy and the differentiation of tumor from local inflammation with superb sensitivity and specificity, which are unachievable by single-locked probes. Thus, this study not only presents the first dual-locked afterglow probe but also proposes a new design way toward dual-locked probes via reactive oxygen species transfer processes.

Near-infrared AIEgens for sulfatase imaging in breast cancer in vivo

Aggregation-induced emission luminogens (AIEgens) enable highly sensitive and in situ visualization of sulfatase to benefit the early diagnosis of breast cancer (BC), but current sulfatase AIEgens always emit visible light (<650 nm). Herein, a near-infrared (NIR) AIEgen QMT-SFA is developed for sulfatase imaging in vivo. Hydrophilic QMT-SFA is cleaved by sulfatase to yield hydrophobic QMT-OH, which subsequently aggregates into nanoparticles to turn the AIE fluorescence "on", enabling sensitive sulfatase imaging in 4T1 cells and mouse models.