A H2O2-activatable nanoprobe for diagnosing interstitial cystitis and liver ischemia-reperfusion injury via multispectral optoacoustic tomography and NIR-II fluorescent imaging

Fluorescent Probes for Disease Diagnosis

The identification and detection of disease-related biomarkers is essential for early clinical diagnosis, evaluating disease progression, and for the development of therapeutics. Possessing the advantages of high sensitivity and selectivity, fluorescent probes have become effective tools for monitoring disease-related active molecules at the cellular level and in vivo. In this review, we describe current fluorescent probes designed for the detection and quantification of key bioactive molecules associated with common diseases, such as organ damage, inflammation, cancers, cardiovascular diseases, and brain disorders. We emphasize the strategies behind the design of fluorescent probes capable of disease biomarker detection and diagnosis and cover some aspects of combined diagnostic/therapeutic strategies based on regulating disease-related molecules. This review concludes with a discussion of the challenges and outlook for fluorescent probes, highlighting future avenues of research that should enable these probes to achieve accurate detection and identification of disease-related biomarkers for biomedical research and clinical applications.

A near-infrared fluorescent probe for imaging peroxynitrite levels in paw edema mice and drug evaluation

A near-infrared fluorescent probe (TX-P) for detecting peroxynitrite is constructed. The probe has a near-infrared emission (725 nm), large Stokes shift (125 nm) and excellent sensitivity and selectivity. In addition, TX-P can be used to visualize ONOO- in living cells, image ONOO- in paw edema mice and evaluate anti-inflammatory drugs.

Injectable-Hydrogel-Based Tissue Sealant for Hemostasis, Bacteria Inhibition, and Pro-Angiogenesis in Organ Bleeding Wounds and Therapeutic Outcome Monitoring Via NIR-II Optical Imaging

Sudden hemorrhage stemming from internal organ wounds poses a grave and potentially fatal risk if left untreated. Injectable-hydrogel-based tissue sealants featuring multiple actions, including fit-to-shape in situ gelation, rapid hemostasis, pro-angiogenic, anti-bacterial and outcome tracking, are ideal for the management of organ trauma wounds. Herein, an injectable-hydrogel tissue sealant AN@CD-PEG&TQ which consists of four-arm 4-arm poly(ethylene glycol) (PEG-SC) succinimidyl carbonate), AN@CD nanoprobe, and two bioactive peptides (anti-microbial peptide Tet213 and pro-angiogenic peptide QK) is developed. Among them, AN@CD nanoparticles form through host/guest complexation of amino-group-containing β-cyclodextrin and adamantyl group, enabling in situ biomarker (NO)-activatable optoacoustic/NIR-II: Near-infrared second biological window fluorescent imaging. The ample ─NH2 groups on the surface of AN@CD readily engage in rapid cross-linking with succinimidyl ester groups located at the ends of four-arm PEG-SC. This cross-linking expedites the gelation process without necessitating additional initiators or cross-linking agents; thus, significantly enhancing both hydrogel's application convenience and biocompatibility. Bioactive peptides (Tet213 and QK) safeguard against possible bacterial infections, facilitate angiogenesis, and eventually, improve organ wounds healing. This hydrogel-based tissue sealant demonstrates superior therapeutic and bioimaging performance in various mouse models including liver hemorrhage, gastric perforation, and bacterial-infected skin wound mouse models, highlighting its potential as a high-performance wound sealant for organ bleeding wound management.

Shining a light on liver health: advancements in fluorescence-enhanced enzyme biosensors for early disease detection

Early detection of liver diseases holds paramount importance in optimizing treatment outcomes and prognosis, thereby significantly enhancing the likelihood of recovery while mitigating the risk of progression to liver cancer. Liver diseases encompass a spectrum of conditions, each potentially manifesting distinct enzymatic profiles. Monitoring these enzymes in situ facilitates timely intervention and therapeutic management. In recent years, the field of biosensor technology has witnessed remarkable advancement, owing to strides in biomedicine and computational sciences. Biosensors have garnered widespread utility across medical and biological domains, spanning the detection of disease biomarkers, drug release tracking, ion imaging, and fluorescence imaging within living organisms. These applications have markedly enhanced imaging resolution and have the potential to refine disease diagnosis accuracy for clinicians. A pivotal aspect in the successful application of this technology lies in the construction of fluorescence probes adept at swiftly and selectively identifying target enzymes by amalgamating liver disease enzymes with fluorescence probe technology. However, research in this niche area remains relatively scarce. Building upon this foundational understanding, the present review delineates the utilization of biosensors in the early diagnosis of liver disease. Serving as a theoretical framework, this review envisages the development of high-performance biosensors tailored for the early detection of liver cancer. Furthermore, it offers insights into the potential of biosensor technology to progress and broaden its practical applications, thus contributing to the advancement of diagnostic methodologies in liver disease management.

Highly-ordered assembled organic fluorescent materials for high-resolution bio-sensing: a review

Organic fluorescent materials (OFMs) play a crucial role in the development of biosensors, enabling the extraction of biochemical information within cells and organisms, extending to the human body. Concurrently, OFM biosensors contribute significantly to the progress of modern medical and biological research. However, the practical applications of OFM biosensors face challenges, including issues related to low resolution, dispersivity, and stability. To overcome these challenges, scientists have introduced interactive elements to enhance the order of OFMs. Highly-ordered assembled OFMs represent a novel material type applied to biosensors. In comparison to conventional fluorescent materials, highly-ordered assembled OFMs typically exhibit robust anti-diffusion properties, high imaging contrast, and excellent stability. This approach has emerged as a promising method for effectively tracking bio-signals, particularly in the non-invasive monitoring of chronic diseases. This review introduces several highly-ordered assembled OFMs used in biosensors and also discusses various interactions that are responsible for their assembly, such as hydrogen bonding, π-π interaction, dipole-dipole interaction, and ion electrostatic interaction. Furthermore, it delves into the various applications of these biosensors while addressing the drawbacks that currently limit their commercial application. This review aims to provide a theoretical foundation for designing high-performance, highly-ordered assembled OFM biosensors suitable for practical applications. Additionally, it sheds light on the evolving trends in OFM biosensors and their application fields, offering valuable insights into the future of this dynamic research area.

Sleep deprivation boosts O2·- levels in the brains of mice as visualized by a Golgi apparatus-targeted ratiometric fluorescence nanosensor

Sleep deprivation (SD) is highly prevalent in the modern technological world. Emerging evidence shows that sleep deprivation is associated with oxidative stress. At the organelle level, the Golgi apparatus actively participates in the stress response. In this study, to determine whether SD and Golgi apparatus stress are correlated, we rationally designed and fabricated a novel Golgi apparatus-targeted ratiometric nanoprobe called Golgi dots for O2·- detection. This probe exhibits high sensitivity and selectivity in cells and brain slices of sleep-deprived mice. Golgi dots can be readily synthesized by coprecipitation of Golgi-F127, an amphiphilic polymer F127 modified with a Golgi apparatus targeting moiety, caffeic acid (CA), the responsive unit for O2·-, and red emissive carbon nanodots (CDs), which act as the reference signal. The fluorescence emission spectrum of the developed nanoprobe showed an intense peak at 674 nm, accompanied by a shoulder peak at 485 nm. As O2·- was gradually added, the fluorescence at 485 nm continuously increased; in contrast, the emission intensity at 674 nm assigned to the CDs remained constant, resulting in the ratiometric sensing of O2·-. The present ratiometric nanoprobe showed high selectivity for O2·- monitoring due to the specific recognition of O2·- by CA. Moreover, the Golgi dots exhibited good linearity with respect to the O2·- concentration within 5 to 40 μM, and the limit of detection (LOD) was ~ 0.13 μM. Additionally, the Golgi dots showed low cytotoxicity and an ability to target the Golgi apparatus. Inspired by these excellent properties, we then applied the Golgi dots to successfully monitor exogenous and endogenous O2·- levels within the Golgi apparatus. Importantly, with the help of Golgi dots, we determined that SD substantially elevated O2·- levels in the brain.

Microneedle System with Biomarker-Activatable Chromophore as Both Optical Imaging Probe and Anti-bacterial Agent for Combination Therapy of Bacterial-Infected Wounds and Outcome Monitoring

Wounds infected with bacteria, if left untreated, have the potential to escalate into life-threatening conditions, such as sepsis, which is characterized by widespread inflammation and organ damage. A comprehensive approach to treating bacterial-infected wounds, encompassing the control of bacterial infection, biofilm eradication, and inflammation regulation, holds significant importance. Herein, a microneedle (MN) patch (FM@ST MN) has been developed, with silk fibroin (SF) and tannic acid-based hydrogel serving as the matrix. Encapsulated within the MNs are the AIEgen-based activatable probe (FQ-H2O2) and the NLRP3 inhibitor MCC950, serving as the optical reporter/antibacterial agent and the inflammation regulator, respectively. When applied onto bacterial-infected wounds, the MNs in FM@ST MN penetrate bacterial biofilms and gradually degrade, releasing FQ-H2O2 and MCC950. The released FQ-H2O2 responds to endogenously overexpressed reactive oxygen species (H2O2) at the wound site, generating a chromophore FQ-OH which emits noticeable NIR-II fluorescence and optoacoustic signals, enabling real-time imaging for outcome monitoring; and this chromophore also exhibits potent antibacterial capability due to its dual positive charges and shows negligible antibacterial resistance. However, the NLRP3 inhibitor MCC950, upon release, suppresses the activation of NLRP3 inflammasomes, thereby mitigating the inflammation triggered by bacterial infections and facilitating wound healing. Furthermore, SF in FM@ST MN aids in tissue repair and regeneration by promoting the proliferation of epidermal cells and fibroblasts and collagen synthesis. This MN system, free from antibiotics, holds promise as a solution for treating and monitoring bacterially infected wounds without the associated risk of antimicrobial resistance.

Homo-Dyad with Outer Hydration Layer Approach for Developing NIR-II Chromophore of High Stability and Water-Solubility as Injectable and Sprayable Optical Probe

Dyes with extended conjugate structures are the focus of extensive design and synthesis efforts, aiming to confer unique and improved optical and electronic properties. Such advancements render these dyes applicable across a wide spectrum of uses, ranging from second-window near-infrared (NIR-II) bioimaging to organic photovoltaics. Nevertheless, the inherent benefits of long conjugation are often accompanied by persistent challenges like aggregation, fluorescence quenching, absorption blueshift, and low stability and poor water solubility. Herein, a unique structural design strategy termed "homo-dyad with outer hydration layer" is introduced to address these inherent problems, tailored for the development of imaging probes exhibiting long absorption/emission wavelengths. This approach involves bringing two heptamethine cyanines together through a flexible linker, forming a homo-dyad structure, while strategically attaching four polyethylene glycol (PEG9) chains to the terminal heterocycles. This approach imparts excellent water solubility, biocompatibility, and enhanced chemical, photo-, and spectral stability for the dyes. Utilizing this strategy, a biomarker-activatable probe (HD-FL-4PEG9-N) for NIR-II fluorescent and 3D multispectral optoacoustic tomography imaging is developed, and its effectiveness in disease visualization. It can not only serve as an injectable probe for acute kidney injury imaging due to its high water solubility, but also a sprayable probe for imaging bacterial-infected wounds.

Renal-clearable nanoprobes for optical imaging and early diagnosis of diseases

Optical imaging has played an indispensable role in clinical diagnostics and fundamental biomedical research due to its high sensitivity, high spatiotemporal resolution, cost-effectiveness, and easy accessibility. However, the issues of light scattering and low tissue penetration make them effective only for superficial imaging. To overcome these issues, renal-clearable optical nanoprobes have recently emerged, which are activated by abnormal disease-associated biomarkers and initiate a pharmacokinetic switch by undergoing degradation and eventually releasing signal reporters into urine, for simple imaging and sensitive optical in vitro urinalysis. In this review, we focus on the advancements of renal-clearable organic nanoprobes for optical imaging and remote urinalysis. The versatile design strategies of these nanoprobes are discussed along with their sensing mechanisms toward biomolecules of interest as well as their unique biological applications. Finally, challenges and perspectives are discussed to further advance the next-generation renal-clearable nanoprobes for in vivo imaging and in vitro urinalysis.

Rational design of NIR-II molecule-engineered nanoplatform for preoperative downstaging and imaging-guided surgery of orthotopic hepatic tumor

Orthotopic advanced hepatic tumor resection without precise location and preoperative downstaging may cause clinical postoperative recurrence and metastasis. Early accurate monitoring and tumor size reduction based on the multifunctional diagnostic-therapeutic integration platform could improve real-time imaging-guided resection efficacy. Here, a Near-Infrared II/Photoacoustic Imaging/Magnetic Resonance Imaging (NIR-II/PAI/MRI) organic nanoplatform IRFEP-FA-DOTA-Gd (IFDG) is developed for integrated diagnosis and treatment of orthotopic hepatic tumor. The IFDG is designed rationally based on the core "S-D-A-D-S" NIR-II probe IRFEP modified with folic acid (FA) for active tumor targeting and Gd-DOTA agent for MR imaging. The IFDG exhibits several advantages, including efficient tumor tissue accumulation, good tumor margin imaging effect, and excellent photothermal conversion effect. Therefore, the IFDG could realize accurate long-term monitoring and photothermal therapy non-invasively of the hepatic tumor to reduce its size. Next, the complete resection of the hepatic tumor in situ lesions could be realized by the intraoperative real-time NIR-II imaging guidance. Notably, the preoperative downstaging strategy is confirmed to lower the postoperative recurrence rate of the liver cancer patients under middle and advanced stage effectively with fewer side effects. Overall, the designed nanoplatform demonstrates great potential as a diagnostic-therapeutic integration platform for precise imaging-guided surgical navigation of orthotopic hepatic tumors with a low recurrence rate after surgery, providing a paradigm for diagnosing and treating the advanced tumors in the future clinical translation application.

Synergistic catalysis and detection of hydrogen peroxide based on a 3D-dimensional molybdenum disulfide interspersed carbon nanotubes nanonetwork immobilized chloroperoxidase biosensor

Enzyme-based electrochemical biosensors are promising for a wide range of applications due to their unique specificity and high sensitivity. In this work, we present a novel enzyme bioelectrode for the sensing of hydrogen peroxide (H2O2). The molybdenum disulfide nanoflowers (MoS2) is self-assembled on carboxylated carbon nanotubes (CNT) to form a three-dimensional conductive network (3D-CNT@MoS2), which is modified with 1-ethyl-3-methylimidazolium bromide (ILEMB), and followed by anchoring chloroperoxidase (CPO) onto the nanocomposite (3D-CNT@MoS2/ILEMB) through covalent binding to form a bioconjugate (3D-CNT@MoS2/ILEMB/CPO). The ILEMB modified 3D-CNT@MoS2/ILEMB has good hydrophilicity and conductivity, which not only provides a suitable microenvironment for the immobilization of CPO but also facilitates the direct electron transfer (DET) of CPO at the electrode. The 3D-CNT@MoS2/ILEMB/CPO bioconjugate modified electrode has a high catalytic efficiency for H2O2. Through electroenzymatic synergistic catalysis for H2O2 detection by 3D-CNT@MoS2/ILEMB/CPO-GCE, a wide detection range of 0.2 μmol·L-1 to 997 μmol·L-1 and a low detection limit of 0.097 μmol･L-1 with high sensitivity of 1050 µA·mmol·L-1·cm-2 were achieved. Additionally, the 3D-CNT@MoS2/ILEMB/CPO-GCE displayed exceptional stability, selectivity, and reproducibility. Furthermore, 3D-CNT@MoS2/ILEMB/CPO-GCE is suitable for sensing of H2O2 in human urine s with good recovery, suggesting its potential application for the detection of H2O2 in biomedical field.

Visualization detection of mycotoxin patulin in fruit juices by a small-molecule fluorescent probe

The mycotoxin patulin is a common contaminant in rotten fruits, posing severe food safety risks and threats to human health. Developing a convenient, sensitive and reliable method for patulin detection is of utmost importance but remains challenging. In this study, we have successfully designed and synthesized a small-molecule fluorescent probe, FITC-Lys, which demonstrates good sensitivity in detecting patulin. Upon contact with patulin, the terminal Lys group of the FITC-Lys probe reacts with patulin, resulting in the formation of the fluorescein dimer that subsequently quenches fluorescence. This variation of fluorescence enables the visualization and sensitive detection of patulin. The probe exhibits good sensitivity with a low LOD of 8 ng mL-1 for the fluorescence spectrum method and a LOD of 12 ng mL-1 for the fluorescence imaging method. Moreover, we have validated the probe's capability for patulin detection in apple and pear juices, achieving good recoveries ranging from 98.60% to 103.80%. Notably, the probe FITC-Lys is the first small-molecule fluorescent probe that has proven successful in visualizing patulin in juices derived from decayed apples and pears. Consequently, this probe holds great potential as a practical tool for monitoring patulin in foodstuffs, thereby contributing to enhanced food safety standards.

Carbonic anhydrase inhibitor-decorated semiconducting oligomer nanoparticles for active-targeting NIR-II fluorescence tumor imaging

Second near-infrared window (NIR-II) fluorescence imaging has shown great potential in the field of bioimaging. To achieve a better imaging effect, variety of NIR-II fluorescence probes have been designed and developed. Among them, semiconducting oligomers (SOs) have shown unique advantages including high photostability and quantum yield, making them promise in NIR-II fluorescence imaging. Herein, we design a SO nanoparticle (ASONi) for NIR-II fluorescence imaging of tumor. ASONi is composed of an azido-functionalized semiconducting oligomer as the NIR-II fluorescence emitter, and a benzene sulfonamide-ended DSPE-PEG (DSPE-PEG-CAi) as the stabilizer. Owing to the benzene sulfonamide groups on the surface, ASONi has the capability of targeting the carbonic anhydrase IX (CA IX) of MDA-MB-231 breast cancer cell. Compared with ASON without benzene sulfonamide groups on the surface, ASONi has a 1.4-fold higher uptake for MDA-MB-231 cells and 1.5-fold higher breast tumor accumulation after i.v. injection. The NIR-II fluorescence signal of ASONi can light the tumor up within 4 h, demonstrating its capability of active tumor targeting and NIR-II fluorescence imaging.

Recent theranostic applications of hydrogen peroxide-responsive nanomaterials for multiple diseases

It is well established that hydrogen peroxide (H2O2) is associated with the initiation and progression of many diseases. With the rapid development of nanotechnology, the diagnosis and treatment of those diseases could be realized through a variety of H2O2-responsive nanomaterials. In order to broaden the application prospects of H2O2-responsive nanomaterials and promote their development, understanding and summarizing the design and application fields of such materials has attracted much attention. This review provides a comprehensive summary of the types of H2O2-responsive nanomaterials including organic, inorganic and organic-inorganic hybrids in recent years, and focused on their specific design and applications. Based on the type of disease, such as tumors, bacteria, dental diseases, inflammation, cardiovascular diseases, bone injury and so on, key examples for above disease imaging diagnosis and therapy strategies are introduced. In addition, current challenges and the outlook of H2O2-responsive nanomaterials are also discussed. This review aims to stimulate the potential of H2O2-responsive nanomaterials and provide new application ideas for various functional nanomaterials related to H2O2.

Viscosity-responsive NIR-II fluorescent probe with aggregation-induced emission features for early diagnosis of liver injury

As the primary organ for drug metabolism and detoxification, the liver is susceptible to damage and seriously impaired function. In situ diagnosing and real-time monitoring of liver damage are thus of great significance but remain limited owing to the lack of reliable in vivo visualization protocols with minimal invasion. Herein, we reported for the first time an aggregation-induced emission (AIE) probe, namely DPXBI, emitting light in the second near-infrared window (NIR-II) for early diagnosis liver injury. DPXBI featured by strong intramolecular rotations, excellent aqueous solubility and robust chemical stability, is powerfully sensitive to viscosity alteration affording rapid response and high selectivity, through NIR-Ⅱ fluorescence intensity changes. The prominent viscosity-responsive performance enables DPXBI to accurately monitor both drug-induced liver injury (DILI) and hepatic ischemia-reperfusion injury (HIRI) with excellent image contrast to the background. By using the presented strategy, the detection of liver injury in mouse model can be achieved at least several hours earlier than typical clinical assays. Moreover, DPXBI is able to dynamically track the liver improvement process in vivo in the case of DILI when the hepatotoxicity is alleviated by using hepatoprotective medication. All these results demonstrate that DPXBI is a promising probe for investigating viscosity-associated pathological and physiological processes.

A photo-triggered self-accelerated nanoplatform for multifunctional image-guided combination cancer immunotherapy

Precise and efficient image-guided immunotherapy holds great promise for cancer treatment. Here, we report a self-accelerated nanoplatform combining an aggregation-induced emission luminogen (AIEgen) and a hypoxia-responsive prodrug for multifunctional image-guided combination immunotherapy. The near-infrared AIEgen with methoxy substitution simultaneously possesses boosted fluorescence and photoacoustic (PA) brightness for the strong light absorption ability, as well as amplified type I and type II photodynamic therapy (PDT) properties via enhanced intersystem crossing process. By formulating the high-performance AIEgen with a hypoxia-responsive paclitaxel (PTX) prodrug into nanoparticles, and further camouflaging with macrophage cell membrane, a tumor-targeting theranostic agent is built. The integration of fluorescence and PA imaging helps to delineate tumor site sensitively, providing accurate guidance for tumor treatment. The light-induced PDT effect could consume the local oxygen and lead to severer hypoxia, accelerating the release of PTX drug. As a result, the combination of PDT and PTX chemotherapy induces immunogenic cancer cell death, which could not only elicit strong antitumor immunity to suppress the primary tumor, but also inhibit the growth of distant tumor in 4T1 tumor-bearing female mice. Here, we report a strategy to develop theranostic agents via rational molecular design for boosting antitumor immunotherapy.

Engineered NIR-II fluorophores with ultralong-distance molecular packing for high-contrast deep lesion identification

The limited signal of long-wavelength near-infrared-II (NIR-II, 900-1880 nm) fluorophores and the strong background caused by the diffused photons make high-contrast fluorescence imaging in vivo with deep tissue disturbed still challenging. Here, we develop NIR-II fluorescent small molecules with aggregation-induced emission properties, high brightness, and maximal emission beyond 1200 nm by enhancing electron-donating ability and reducing the donor-acceptor (D-A) distance, to complement the scarce bright long-wavelength emissive organic dyes. The convincing single-crystal evidence of D-A-D molecular structure reveals the strong inhibition of the π-π stacking with ultralong molecular packing distance exceeding 8 Å. The delicately-designed nanofluorophores with bright fluorescent signals extending to 1900 nm match the background-suppressed imaging window, enabling the signal-to-background ratio of the tissue image to reach over 100 with the tissue thickness of ~4-6 mm. In addition, the intraluminal lesions with strong negatively stained can be identified with almost zero background. This method can provide new avenues for future long-wavelength NIR-II molecular design and biomedical imaging of deep and highly scattering tissues.

Aggregation-Induced Emission (AIE), Life and Health

Light has profoundly impacted modern medicine and healthcare, with numerous luminescent agents and imaging techniques currently being used to assess health and treat diseases. As an emerging concept in luminescence, aggregation-induced emission (AIE) has shown great potential in biological applications due to its advantages in terms of brightness, biocompatibility, photostability, and positive correlation with concentration. This review provides a comprehensive summary of AIE luminogens applied in imaging of biological structure and dynamic physiological processes, disease diagnosis and treatment, and detection and monitoring of specific analytes, followed by representative works. Discussions on critical issues and perspectives on future directions are also included. This review aims to stimulate the interest of researchers from different fields, including chemistry, biology, materials science, medicine, etc., thus promoting the development of AIE in the fields of life and health.

Progress in Pluronic F127 Derivatives for Application in Wound Healing and Repair

Pluronic F127 hydrogel biomaterial has garnered considerable attention in wound healing and repair due to its remarkable properties including temperature sensitivity, injectability, biodegradability, and maintain a moist wound environment. This comprehensive review provides an in-depth exploration of the recent advancements in Pluronic F127-derived hydrogels, such as F127-CHO, F127-NH2, and F127-DA, focusing on their applications in the treatment of various types of wounds, ranging from burns and acute wounds to infected wounds, diabetic wounds, cutaneous tumor wounds, and uterine scars. Furthermore, the review meticulously examines the intricate interaction mechanisms employed by these hydrogels within the wound microenvironment. By elucidating the underlying mechanisms, discussing the strengths and weaknesses of Pluronic F127, analyzing the current state of wound healing development, and expanding on the trend of targeting mitochondria and cells with F127 as a nanomaterial. The review enhances our understanding of the therapeutic effects of these hydrogels aims to foster the development of effective and safe wound-healing modalities. The valuable insights provided this review have the potential to inspire novel ideas for clinical treatment and facilitate the advancement of innovative wound management approaches.

Cucurbit[8]uril-based water-dispersible assemblies with enhanced optoacoustic performance for multispectral optoacoustic imaging

Organic small-molecule contrast agents have attracted considerable attention in the field of multispectral optoacoustic imaging, but their weak optoacoustic performance resulted from relatively low extinction coefficient and poor water solubility restrains their widespread applications. Herein, we address these limitations by constructing supramolecular assemblies based on cucurbit[8]uril (CB[8]). Two dixanthene-based chromophores (DXP and DXBTZ) are synthesized as the model guest compounds, and then included in CB[8] to prepare host-guest complexes. The obtained DXP-CB[8] and DXBTZ-CB[8] display red-shifted and increased absorption as well as decreased fluorescence, thereby leading to a substantial enhancement in optoacoustic performance. Biological application potential of DXBTZ-CB[8] is investigated after co-assembly with chondroitin sulfate A (CSA). Benefiting from the excellent optoacoustic property of DXBTZ-CB[8] and the CD44-targeting feature of CSA, the formulated DXBTZ-CB[8]/CSA can effectively detect and diagnose subcutaneous tumors, orthotopic bladder tumors, lymphatic metastasis of tumors and ischemia/reperfusion-induced acute kidney injury in mouse models with multispectral optoacoustic imaging.

Activatable BODIPY-chromene NIR-II probes with small spectral crosstalk enable high-contrast in vivo bioimaging

Herein, we design a novel "crossbreeding" dye (BC-OH) within the second near-infrared (NIR-II) window based on BODIPY and chromene chromophores. BC-OH can serve as a platform to construct activatable NIR-II probes with small spectral crosstalk, thereby making a breakthrough in imaging in vivo H₂O₂ fluctuation in an APAP-induced liver injury model with high signal-to-background ratio.

Dynamic-Reversible MRI Nanoprobe for Continuous Imaging Redox Homeostasis in Hepatic Ischemia-Reperfusion Injury

Hepatic ischemia-reperfusion (I/R) injury accompanied by oxidative stress is responsible for postoperative liver dysfunction and failure of liver surgery. However, the dynamic non-invasive mapping of redox homeostasis in deep-seated liver during hepatic I/R injury remains a great challenge. Herein, inspired by the intrinsic reversibility of disulfide bond in proteins, a kind of reversible redox-responsive magnetic nanoparticles (RRMNs) is designed for reversible imaging of both oxidant and antioxidant levels (ONOO^-/GSH), based on sulfhydryl coupling/cleaving reaction. We develop a facile strategy to prepare such reversible MRI nanoprobe via one-step surface modification. Owing to the significant change in size during the reversible response, the imaging sensitivity of RRMNs is greatly improved, which enables RRMNs to monitor the tiny change of oxidative stress in liver injury. Notably, such reversible MRI nanoprobe can non-invasively visualize the deep-seated liver tissue slice by slice in living mice. Moreover, this MRI nanoprobe can not only report molecular information about the degree of liver injury but also provide anatomical information about where the pathology occurred. The reversible MRI probe is promising for accurately and facilely monitoring I/R process, accessing injury degree and developing powerful strategy for precise treatment.

Tunable Nanoparticles with Aggregation-Induced Emission Heater for Precise Synergistic Photothermal and Thermodynamic Oral Cancer Therapy of Patient-Derived Tumor Xenograft

The fluorophores in the second near-infrared (NIR-II) biological window (1000 - 1700 nm) show great application prospects in the fields of biology and optical communications. However, both excellent radiative transition and nonradiative transition cannot be achieved simultaneously for the majority of traditional fluorophores. Herein, tunable nanoparticles formulated with aggregation-induced emission (AIE) heater are developed rationally. The system can be implemented via the development of an ideal synergistic system that can not only produce photothermal from nonspecific triggers but also trigger carbon radical release. Once accumulating in tumors and subsequently being irradiated with 808 nm laser, the nanoparticles (NMB@NPs) encapsulated with NMDPA-MT-BBTD (NMB) are splitted due to the photothermal effect of NMB, leading to the decomposition of azo bonds in the nanoparticle matrix to generate carbon radical. Accompanied by second near-infrared (NIR-II) window emission from the NMB, fluorescence image-guided thermodynamic therapy (TDT) and photothermal therapy (PTT) which significantly inhibited the growth of oral cancer and negligible systemic toxicity is achieved synergistically. Taken together, this AIE luminogens-based synergistic photothermal-thermodynamic strategy brings a new insight into the design of superior versatile fluorescent NPs for precise biomedical applications and holds great promise to enhance the therapeutic efficacy of cancer therapy.

Renal-Clearable Probe with Water Solubility and Photostability for Biomarker-Activatable Detection of Acute Kidney Injuries via NIR-II Fluorescence and Optoacoustic Imaging

Acute kidney injuries (AKI) have serious short-term or long-term complications with high morbidity and mortality rate, thus posing great health threats. Developing high-performance NIR-II probes for noninvasive in situ detection of AKI via NIR-II fluorescent and optoacoustic dual-mode imaging is of great significance. Yet NIR-II chromophores often feature long conjugation and hydrophobicity, which prevent them from being renal clearable, thus limiting their applications in the detection and imaging of kidney diseases. To fully exploit the advantageous features of heptamethine cyanine dye, while overcoming its relatively poor photostability, and to strive to design a NIR-II probe for the detection and imaging of AKI with dual-mode imaging, herein, we have developed the probe PEG3-HC-PB, which is renal clearable, water soluble, and biomarker activatable and has good photostability. As for the probe, its fluorescence (900-1200 nm) is quenched due to the existence of the electron-pulling phenylboronic group (responsive element), and it exhibits weak absorption with a peak at 830 nm. Meanwhile, in the presence of the overexpressed H₂O₂ in the renal region in the case of AKI, the phenylboronic group is converted to the phenylhydroxy group, which enhances NIR-II fluorescent emission (900-1200 nm) and absorption (600-900 nm) and eventually produces conspicuous optoacoustic signals and NIR-II fluorescent emission for imaging. This probe enables detection of contrast-agent-induced and ischemia/reperfusion-induced AKI in mice using real-time 3D-MSOT and NIR-II fluorescent dual-mode imaging via response to the biomarker H₂O₂. Hence, this probe can be used as a practicable tool for detecting AKI; additionally, its design strategy could provide insight into the design of other large-conjugation NIR-II probes with multifarious biological applications.

Ultrasensitive Urinary Diagnosis of Organ Injuries Using Time-Resolved Luminescent Lanthanide Nano-bioprobes

Urinary sensing of synthetic biomarkers that are released into urine after specific activation in an in vivo disease environment is an emerging diagnosis strategy to overcome the insensitivity of a previous biomarker assay. However, it remains a great challenge to achieve sensitive and a specific urinary photoluminescence (PL) diagnosis. Herein, we report a novel urinary time-resolved PL (TRPL) diagnosis strategy by exploiting europium complexes of diethylenetriaminepentaacetic acid (Eu-DTPA) as synthetic biomarkers and designing the activatable nanoprobes. Notably, TRPL of Eu-DTPA in the enhancer can eliminate the urinary background PL for ultrasensitive detection. We achieved sensitive urinary TRPL diagnosis of mice kidney and liver injuries by using simple Eu-DTPA and Eu-DTPA-integrated nanoprobes, respectively, which cannot be realized by traditional blood assays. This work demonstrates the exploration of lanthanide nanoprobes for in vivo disease-activated urinary TRPL diagnosis for the first time, which might advance the noninvasive diagnosis of diverse diseases via tailorable nanoprobe designs.

A biomarker-responsive nanoprobe for detecting hepatic ischemia-reperfusion injury via optoacoustic/NIR-II fluorescence imaging

A nanoprobe for detecting hepatic ischemia-reperfusion injury has been developed. Apparent optoacoustic and NIR-II fluorescent signals are given out upon the nanoprobe's response to the in situ biomarker H₂O₂ in the liver in the case of ischemia-reperfusion injury.

The application of optical technology in the diagnosis and therapy of oxidative stress-mediated hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (HIRI) is defined as liver tissue damage and cell death caused by reperfusion during liver transplantation or hepatectomy. Oxidative stress is one of the important mechanisms of HIRI. Studies have shown that the incidence of HIRI is very high, however, the number of patients who can get timely and efficient treatment is small. The reason is not hard to explain that invasive ways of detection and lack of timely of diagnostic methods. Hence, a new detection method is urgently needed in clinic application. Reactive oxygen species (ROS), which are markers of oxidative stress in the liver, could be detected by optical imaging and offer timely and effective non-invasive diagnosis and monitoring. Optical imaging could become the most potential tool of diagnosis of HIRI in the future. In addition, optical technology can also be used in disease treatment. It found that optical therapy has the function of anti-oxidative stress. Consequently, it has possibility to treat HIRI caused by oxidative stress. In this review, we mainly summarized the application and prospect of optical techniques in oxidative stress-induced by HIRI.

Design strategies and applications of smart optical probes in the second near-infrared window

Over the last decade, a series of synergistic advances in the synthesis chemistries and imaging instruments have largely boosted a significant revolution, in which large-scale biomedical applications are now benefiting from optical bioimaging in the second near-infrared window (NIR-II, 1000-1700 nm). The large tissue penetration and limited autofluorescence associated with long-wavelength imaging improve translational potential of NIR-II imaging over common visible-light (400-650 nm) and NIR-I (750-900 nm) imaging, with ongoing profound effects on the studies of precision medicine. Unfortunately, the majority of NIR-II probes are designed as "always-on" luminescent imaging contrasts, continuously generating unspecific signals regardless of whether they reach pathological locations. Thus, in vivo imaging by traditional NIR-II probes usually suffers from weak detect precision due to high background noise. In this context, the advances of optical imaging now enter into an era of precise control of NIR-II photophysical kinetics. Developing NIR-II optical probes that can efficiently activate their luminescent signal in response to biological targets of interest and substantially suppress the background interferences have become a highly prospective research frontier. In this review, the merits and demerits of optical imaging probes from visible-light, NIR-I to NIR-II windows are carefully discussed along with the lens of stimuli-responsive photophysical kinetics. We then highlight the latest development in engineering methods for designing smart NIR-II optical probes. Finally, to appreciate such advances, challenges and prospect in rapidly growing study of smart NIR-II probes are addressed in this review.

Effective design of organic luminogens for near-infrared-II fluorescence imaging and photo-mediated therapy

Due to their electron coupling capability, organic luminescent materials exhibit powerful optoelectronic features that are responsible for their light-harvesting and light-amplification properties. The extensive modification of conjugated systems has shown significant improvement in their photonic properties thus broadening their applicability in photo-mediated imaging and photo-based treatment. Organic luminogens with emission in the near-infrared second region are found attractive not only for their deeper penetrating power but also for accurate visual imaging superiority with higher temporal resolution and spatial resolution suitable for tumor precision treatment. In this review, we underscore the latest development in organic luminogens (conjugated polymers and small molecules), focusing on chemical design, molecular engineering, and their applications in the scope of bioimaging followed by photo-assisted treatment, including photodynamic therapy (PDT), photothermal therapy (PTT), and immunotherapy ablation. Organic luminogens integrated with an aggregation-induced emission feature significantly optimize their physicochemical properties to act as quintessential nanoplatforms for controllable image-guided therapy. In conclusion, we clarify the limitations and challenges and provide insights into how to design organic dyes with improved safety for potential clinical applications.

Norsquaraine endowed with anticancer and antibacterial activities

BACKGROUND

Photodynamic therapy (PDT) is a method for the treatment of cancer. Furthermore, PDT can also be used for the eradication of bacteria. The photo-sensitizing drug, a.k.a photosensitizer, is critical for the success of PDT. Although norsquaraines are analogs of squaraine dyes, they are overlooked as photosensitizers.

METHODS

In this work, synthesis, characterization, bioimaging and in vitro PDT applications of a new norsquaraine dye 1 were described. We also prepared nanoparticles from norsquaraine 1 and Pluronic F127 to obtain 1@F127.

RESULTS

Norsquaraine 1 boosted the generation of reactive oxygen species over a wide range of pH (pH 8.0, 7.0, 6.0, and 2.2.). Furthermore, 1 was internalized by epidermoid laryngeal carcinoma Hep-2 (Hep-2) cells and used for fluorescence imaging. Remarkably, norsquaraine 1 destroyed most of the cancer cells (ca. 77% to 89%) after illumination with red light. Most strikingly, 1 successfully inhibited the growth of Methicillin-resistant Staphylococcus aureus (MRSA) upon illumination. Last but not least, photodynamic sterilization of tomato juice, an acidic beverage, was feasible using 1 as a photo sterilizer. Nano formulation of 1 with Pluronic F127 provided 1@F127 nanoparticles. It is lucid that 1@F127 nanoparticles permeate into Hep-2 cells and boost the generation of ROS upon illumination.

CONCLUSION

Norsquaraine 1 shows superior features as a photosensitizer pertinent to PDT in a wide range of pH. This norsquaraine is endowed with anticancer and antibacterial activities. Which should be further evaluated.

A Biomarker-Responsive Nanosystem with Colon-Targeted Delivery for Ulcerative Colitis's Detection and Treatment with Optoacoustic/NIR-II Fluorescence Imaging

Ulcerative colitis (UC) is a prevalent idiopathic inflammatory disease which causes such complications as intestinal perforation, obstruction, and bleeding, and thus deleteriously impacting people's normal work and quality of life. Hence, accurate diagnosis of UC is crucial in terms of planning optimal treatment plan. Herein, a pH/reactive oxygen species (ROS) dual-responsive nanosystem (BM@EP) is developed for UC's detection and therapy. BM@EP is composed of a chromophore-drug dyad and the enteric coating. The chromophore-drug dyad (BOD-XT-DHM) is synthesized by linking the chromophore (BOD-XT-BOH) and a flavonoid drug (dihydromyricetin DHM) through boronate ester bond. The enteric coating includes Eudragit S100 and poly(lactic-co-glycolic acid) (PLGA), the former is commonly employed as a pH-dependent polymer coating excipient so as to attain colon-targeted delivery, and the latter has been widely used as an excipient for the controlled-extended release. After oral administration, BM@EP delivers the dyad (BOD-XT-DHM) into the colon and releases the dyad molecules by being triggered by the alkaline pH in t colon, thereafter upon being stimulated by overexpressed H₂ O₂ in the inflamed colon, the boronate bond in the dyad is broken down and correspondingly the drug DHM is released for UC therapy, simultaneously the chromophore is released for near-infrared second window (NIR-II) fluorescence and optoacoustic imaging for UC diagnosis and recovery evaluation.

NIR-II AIEgens with Photodynamic Effect for Advanced Theranostics

Phototheranostics that concurrently integrates accurate diagnosis (e.g., fluorescence and photoacoustic (PA) imaging) and in situ therapy (e.g., photodynamic therapy (PDT) and photothermal therapy (PTT)) into one platform represents an attractive approach for accelerating personalized and precision medicine. The second near-infrared window (NIR-II, 1000-1700 nm) has attracted considerable attention from both the scientific community and clinical doctors for improved penetration depth and excellent spatial resolution. NIR-II agents with a PDT property as well as other functions are recently emerging as a powerful tool for boosting the phototheranostic outcome. In this minireview, we summarize the recent advances of photodynamic NIR-II aggregation-induced emission luminogens (AIEgens) for biomedical applications. The molecular design strategies for tuning the electronic bandgaps and photophysical energy transformation processes are discussed. We also highlight the biomedical applications, such as image-guided therapy of both subcutaneous and orthotopic tumors, and multifunctional theranostics in combination with other treatment methods, including chemotherapy and immunotherapy; and the precise treatment of both tumor and bacterial infection. This review aims to provide guidance for PDT agents with long-wavelength emissions to improve the imaging precision and treatment efficacy. We hope it will provide a comprehensive understanding about the chemical structure-photophysical property-biomedical application relationship of NIR-II luminogens.

A Renal-Clearable PEGylated Semiconducting Oligomer for the NIR-II Fluorescence Imaging of Tumor

Second near-infrared window fluorescence imaging (NIR-II FI) has attracted tremendous attention in bioimaging. Until now, most probes for NIR-II FI are nanomaterials that are metabolized via hepatobiliary metabolism. Such a metabolic pathway may take several months, causing long-term toxicity. Herein, we design and synthesize a renal-clearable PEGylated semiconducting oligomer (PSO) for the NIR-II FI of tumor. PSO is composed of a semiconducting oligomer (SO) backbone as an NIR-II fluorescence reporter and four poly(ethylene glycol) (PEG) side chains as water-soluble enhancers. PSO can emit an NIR-II fluorescence signal with the maximum emission at 1000 nm under the excitation of 808 nm light. PSO shows good biocompatibility and can be partially cleared out of body via renal clearance. PSO can be utilized for the NIR-II FI of tumor as it can effectively accumulate into tumor.

Water-Dispersible Activatable Nanoprobe for Detecting Cadmium-Ion-Induced Oxidative Stress in Edible Crops via Near-Infrared Second-Window Fluorescence Imaging

Edible crops are important in terms of food security and sustainable agriculture. Heavy-metal-ion contamination of water/soil has deleterious impacts on the growth of edible crops. Among the heavy metals, cadmium (Cd) is toxic to plants, people, and animals, as it is widely used in industry; it has become the most important metal ion in the soil/water pollution. Once the toxic Cd ion enters edible crops via the water/soil in which the crops grow, it will induce oxidative stress (overproduction of reactive oxygen species with H₂O₂ being the most abundant) in the crops, and strong oxidative stress leads to the crops' growth depression or inhibition. Hence, it is of great significance to accurately monitor the oxidative stress induced by Cd ions in edible crops, as the monitoring results could be employed for the early warning of Cd-ion pollution in water/soil. Herein, we design an activatable nanoprobe that can detect Cd-ion-induced oxidative stress in edible crops via near-infrared second-window (NIR-II) fluorescence imaging. The molecular probe IXD-B contains the diphenylamine-modified xanthene group acting as the electron-donating unit, bis(methylenemalononitrile)indan as the electron-accepting unit, and the methenephenylboronic acid group as the recognition moiety for H₂O₂ and the fluorescence quencher. The probe molecules being encapsulated by the amphiphilic DSPE-PEG2000 render the water-dispersible nanoprobe (IXD-B@DSPE-PEG2000). When the nanoprobe enters the edible crops, it can be activated by the overexpressed H₂O₂ therein and consequently emit strong NIR-II fluorescence signals for visualizing and tracking the oxidative stress in edible crops induced by Cd ions.

Reactive Species-Activatable AIEgens for Biomedical Applications

Precision medicine requires highly sensitive and specific diagnostic strategies with high spatiotemporal resolution. Accurate detection and monitoring of endogenously generated biomarkers at the very early disease stage is of extensive importance for precise diagnosis and treatment. Aggregation-induced emission luminogens (AIEgens) have emerged as a new type of excellent optical agents, which show great promise for numerous biomedical applications. In this review, we highlight the recent advances of AIE-based probes for detecting reactive species (including reactive oxygen species (ROS), reactive nitrogen species (RNS), reactive sulfur species (RSS), and reactive carbonyl species (RCS)) and related biomedical applications. The molecular design strategies for increasing the sensitivity, tuning the response wavelength, and realizing afterglow imaging are summarized, and theranostic applications in reactive species-related major diseases such as cancer, inflammation, and vascular diseases are reviewed. The challenges and outlooks for the reactive species-activatable AIE systems for disease diagnostics and therapeutics are also discussed. This review aims to offer guidance for designing AIE-based specifically activatable optical agents for biomedical applications, as well as providing a comprehensive understanding about the structure-property application relationships. We hope it will inspire more interesting researches about reactive species-activatable probes and advance clinical translations.

NIR-II bioimaging of small molecule fluorophores: From basic research to clinical applications

Due to the low autofluorescence and deep-photo penetration, the second near-infrared region fluorescence imaging technology (NIR-II, 1000-2000 nm) has been widely utilized in basic scientific research and preclinical practice throughout the past decade. The most attractive candidates for clinical translation are organic NIR-II fluorophores with a small-molecule framework, owing to their low toxicity, high synthetic repeatability, and simplicity of chemical modification. In order to enhance the translation of small molecule applications in NIR-II bioimaging, NIR-II fluorescence imaging technology has evolved from its usage in cells to the diagnosis of diseases in large animals and even humans. Although several examples of NIR-II fluorescence imaging have been used in preclinical studies, there are still many challenges that need to be addressed before they can finally be used in clinical settings. In this paper, we reviewed the evolution of the chemical structures and photophysical properties of small-molecule fluorophores, with an emphasis on their biomedical applications ranging from small animals to humans. We also explored the potential of small-molecule fluorophores.

A nitrobenzoxadiazole-based near-infrared fluorescent probe for the specific imaging of H2S in inflammatory and tumor mice

As a common gaseous signaling molecule, hydrogen sulfide (H₂S) plays a vital role in physiology and pathology. The development of fluorescent probes for detecting H₂S has attracted widespread attention. However, most of the reported fluorescent probes with nitrobenzoxadiazole (NBD) as the recognition group have been widely used to simultaneously detect biothiols and H₂S, instead of specifically detecting H₂S. Herein, a novel NBD-based near-infrared (NIR) fluorescent probe named CX-N for the detection of H₂S is synthesized. The selectivity of CX-N for H₂S is significantly higher than that for biothiols and other potential interferences. After reacting with H₂S, CX-N shows a significant increase in NIR fluorescence (75-fold), large Stokes shift (155 nm) and fast response (4 min). And the possible response mechanism of CX-N to H₂S is given and confirmed by HPLC and HRMS. Based on the low cytotoxicity of CX-N, it has been used for H₂S imaging in live cells and zebrafish. More importantly, CX-N has also been successfully applied for the real-time imaging of H₂S in inflammatory and tumor mice based on its NIR emission, which provides a reliable platform for the specific recognition of H₂S in complex biological systems.

Cyclodextrin-Confined Supramolecular Lanthanide Photoswitch

The utilization of azobenzene-based photoisomerization cannot only control the morphology of supramolecular assemblies, but can also regulate many biological processes. However, the design of azobenzene-involved nanoconstructs with switchable photoluminescence remains challenging because of the light-quenching ability of azobenzene. Herein, an azobenzene-derived multicomponent nanosystem is reported and its function as a supramolecular lanthanide photoswitch is explored. The metal chelation between lanthanide ions (Ln³⁺  = Eu³⁺ and Tb³⁺ ) and 2,6-pyridinedicarboxylic acid is utilized as the light-emitting center but its inherent fluorescence emission is completely suppressed via the disordered motion of the adjoining azophenyl unit. Interestingly, the hydrophobic cavity of α-cyclodextrin can provide a confined microenvironment to immobilize the molecular conformation of trans-azobenzene, thus leading to the recovery of characteristic lanthanide luminescence both in aqueous solution and the hydrogel state. Also, the luminescence can be reversibly turned off when the cis-azobenzene is expelled from the cavity of α-cyclodextrin upon alternating light irradiation. This mutual cooperation arising from host-guest complexation and metal-ligand coordination confers the desired photoswitchable luminescence abilities on the commonly used azobenzenes, which may hold great promise in the creation of more advanced light-responsive smart materials.

Polymeric agents for activatable fluorescence, self-luminescence and photoacoustic imaging

Numerous polymeric agents have been widely applied in biology and medicine by virtue of the facile chemical modification, feasible nano-engineering approaches and fine-tuned pharmacokinetics. To endow polymeric imaging agents with ability to monitor and measure subtle molecular or cellular alterations at diseased sites, activatable polymeric probes that can elicit signal changes in response to biomolecular interactions or the analytes of interest have to be developed. Herein, this review aims to provide a systemic interpretation and summarization of the design methodology and imaging utility of recently emerged activatable polymeric probes. An introduction of activatable probes allowing for precise imaging and classification of polymeric imaging agents is reported first. Then, we give a detailed discussion of the contemporary design approaches toward activatable polymeric probes in diverse imaging modes for the detection of various stimuli and their imaging applications. Finally, current challenges and future advances are discussed and highlighted.

AIE-active luminogens as highly efficient free-radical ROS photogenerator for image-guided photodynamic therapy

Image-guided photodynamic therapy (PDT) can realize highly precise and effective therapy via the integration of imaging and therapy, and has created high requirements for photosensitizers. However, the PDT modality usually utilizes conventional type II photosensitizers, resulting in unsatisfactory imaging and therapeutic outcomes due to aggregation-caused quenching (ACQ), "always on" fluorescence and strong oxygen dependence. Herein, we report the type I-based aggregation-induced emission (AIE) photosensitizer TCM-CPS with low oxygen dependence, near-infrared (NIR) emission and "off-on" fluorescence; in particular, it produces more reactive oxygen species (ROS) than commercially available Chlorin e6 and Rose Bengal. In the rational design of the AIE-based photosensitizer TCM-CPS, the strongly electron-donating carbazole unit and π-thiophene bridge distinctly extend the emission wavelength and decrease the autofluorescence interference in bio-imaging, and the hydrophilic pyridinium salt group guarantees good molecular dispersion and maintains the fluorescence-off state in the aqueous system to decrease the initial fluorescence background. Moreover, the strong donor-π-acceptor (D-π-A) character in TCM-CPS greatly separates the HOMO-LUMO distribution, enhancing the ROS generation, and TCM-CPS was constructed as a type I photosensitizer with the assistance of strong intramolecular charge transfer in the electron-rich anion-π+ structure. Based on its favorable hydrophilicity and photosensitivity, TCM-CPS was found to be a highly efficient free-radical ROS photogenerator for both visualizing cells using light-up NIR fluorescence and efficiently killing cancer cells upon light irradiation. The positively charged TCM-CPS could quickly bind to bacteria via electrostatic interactions to provide a light-up signal and kill bacteria at a low concentration. In the PDT treatment of bacteria-infected mice, the mice exhibited accelerated wound healing with low wound infection. Thus, the AIE-based type I photosensitizer TCM-CPS has great potential to replace commercially available photosensitizers in the image-guided PDT modality for the treatment of cancer and bacterial infection.

Rational design of stable heptamethine cyanines and development of a biomarker-activatable probe for detecting acute lung/kidney injuries via NIR-II fluorescence imaging

Heptamethine cyanines exhibiting high photo- and chemostability have been developed. And an activatable probe was developed for H2O2 to visualize acute lung and kidney injuries via NIR-II fluorescence imaging.