NIR-II phototherapy agents with aggregation-induced emission characteristics for tumor imaging and therapy

Nanoparticles Encapsulated in Red Blood Cell Membranes for Near-Infrared Second Window Imaging-Guided Photothermal-Enhanced Immunotherapy on Tumors

Photothermal therapy (PTT), which uses the high thermal conversion ability of photothermal agents to ablate tumor cells at high temperatures, has gained significant attention because it has the advantages of high selectivity and specificity, precise targeting of tumor sites, and low invasiveness and trauma. However, PTT guided by the NIR-I has limitations in tissue penetration depth, resulting in limited imaging monitoring and therapeutic effects on deep-seated tumor tissues. Moreover, nanoparticles are easily cleared by the immune system and difficult to passively target tumor sites during the process of treatment. To address these issues, we prepared nanoparticles using NIR-II dyes IR1048 and DSPE-PEG-OH and further encapsulated them in red blood cell membranes derived from mice. These biomimetic nanoparticles, called RDIR1048, showed reduced clearance by the immune system and had long circulation characteristics. They effectively accumulated at tumor sites, and strong fluorescence could still be observed at the tumor site 96 h after administration. Furthermore, through mouse thermal imaging experiments, we found that RDIR1048 exhibited good PTT ability. When used in combination with an immune checkpoint inhibitor, anti-PD-L1 antibodies, it enhanced the immunogenic cell death of tumor cells caused by PTT and improved the therapeutic effect of immunotherapy, which demonstrated good therapeutic efficacy in the treatment of tumor-bearing mice. This study provides a feasible basis for the future development of NIR-II nanoparticles with long circulation properties.

Layered Double Hydroxides: Recent Progress and Promising Perspectives Toward Biomedical Applications

Layered double hydroxides (LDHs) have been widely studied for biomedical applications due to their excellent properties, such as good biocompatibility, degradability, interlayer ion exchangeability, high loading capacity, pH-responsive release, and large specific surface area. Furthermore, the flexibility in the structural composition and ease of surface modification of LDHs makes it possible to develop specifically functionalized LDHs to meet the needs of different applications. In this review, the recent advances of LDHs for biomedical applications, which include LDH-based drug delivery systems, LDHs for cancer diagnosis and therapy, tissue engineering, coatings, functional membranes, and biosensors, are comprehensively discussed. From these various biomedical research fields, it can be seen that there is great potential and possibility for the use of LDHs in biomedical applications. However, at the same time, it must be recognized that the actual clinical translation of LDHs is still very limited. Therefore, the current limitations of related research on LDHs are discussed by combining limited examples of actual clinical translation with requirements for clinical translation of biomaterials. Finally, an outlook on future research related to LDHs is provided.

Rotor-based image-guided therapy of glioblastoma

Glioblastoma (GBM), deep in the brain, is more challenging to diagnose and treat than other tumors. Such challenges have blocked the development of high-impact therapeutic approaches that combine reliable diagnosis with targeted therapy. Herein, effective cyanine dyes (IRLy) with the near-infrared two region (NIR-II) adsorption and aggregation-induced emission (AIE) have been developed via an "extended conjugation & molecular rotor" strategy for multimodal imaging and phototherapy of deep orthotopic GBM. IRLy was synthesized successfully through a rational molecular rotor modification with stronger penetration, higher signal-to-noise ratio, and a high photothermal conversion efficiency (PCE) up to ∼60%, which can achieve efficient NIR-II photo-response. The multifunctional nanoparticles (Tf-IRLy NPs) were further fabricated to cross the blood-brain barrier (BBB) introducing transferrin (Tf) as a targeting ligand. Tf-IRLy NPs showed high biosafety and good tumor enrichment for GBM in vitro and in vivo, and thus enabled accurate, efficient, and less invasive NIR-II multimodal imaging and photothermal therapy. This versatile Tf-IRLy nanosystem can provide a reference for the efficient, precise and low-invasive multi-synergistic brain targeted photo-theranostics. In addition, the "extended conjugation & molecular rotor" strategy can be used to guide the design of other photothermal agents.

D-A-D organic fluorescent probes for NIR-II fluorescence imaging and efficient photothermal therapy of breast cancer

Near-infrared second region (NIR-II) fluorescent probes are used in the diagnosis of early cancer due to their high tissue penetration. However, there are still few reports on organic small molecule fluorescent probes with NIR-II fluorescence imaging (NIR-II FI) combined with efficient photothermal therapy (PTT). In this study, planar cyclopentadithiophene (CPDT) was incorporated into the twisted structural skeleton (D-A-D), and the strong acceptor TTQ molecule (A) and the donor triphenylamine (D) were introduced to synthesize an organic small molecule (TCT) with enhanced NIR-II fluorescence emission performance. To improve the hydrophilicity of TCT molecules, we used the nanoprecipitation method to coat DSPE-mPEG2000 on the TCT molecules and obtained nanoparticles (TCT-NPs) with a strong absorption band, good water dispersibility, and NIR-II FI ability, which realized NIR-II FI-guided PTT for breast cancer tumors. Due to their effective near-infrared absorption, TCT-NPs exhibit high photothermal conversion efficiency (η = 40.1%) under 660 nm laser irradiation, making them a photothermal therapeutic agent with good performance. Therefore, TCT-NPs have the potential to diagnose, eliminate, and monitor the diffusion of cancer.

Recent Progress on Tumor Microenvironment-Activated NIR-II Phototheranostic Agents with Simultaneous Activation for Diagnosis and Treatment

Malignant tumors seriously threaten human life and well-being. Emerging Near-infrared II (NIR-II, 1000-1700 nm) phototheranostic nanotechnology integrates diagnostic and treatment modalities, offering merits including improved tissue penetration and enhanced spatiotemporal resolution. This remarkable progress has opened promising avenues for advancing tumor theranostic research. The tumor microenvironment (TME) differs from normal tissues, exhibiting distinct attributes such as hypoxia, acidosis, overexpressed hydrogen peroxide, excess glutathione, and other factors. Capitalizing on these attributes, researchers have developed TME-activatable NIR-II phototheranostic agents with diagnostic and therapeutic attributes concurrently. Therefore, developing TME-activatable NIR-II phototheranostic agents with diagnostic and therapeutic activation holds significant research importance. Currently, research on TME-activatable NIR-II phototheranostic agents is still in its preliminary stages. This review examines the recent advances in developing dual-functional NIR-II activatable phototheranostic agents over the past years. It systematically presents NIR-II phototheranostic agents activated by various TME factors such as acidity (pH), hydrogen peroxide (H2 O2 ), glutathione (GSH), hydrogen sulfide (H2 S), enzymes, and their hybrid. This encompasses NIR-II fluorescence and photoacoustic imaging diagnostics, along with therapeutic modalities, including photothermal, photodynamic, chemodynamic, and gas therapies triggered by these TME factors. Lastly, the difficulties and opportunities confronting NIR-II activatable phototheranostic agents in the simultaneous diagnosis and treatment field are highlighted.

Benzobisthiadiazole-Based Small Molecular Near-Infrared-II Fluorophores: From Molecular Engineering to Nanophototheranostics

Organic fluorescent molecules with emission in the second near-infrared (NIR-II) biological window have aroused increasing investigation in cancer phototheranostics. Among these studies, Benzobisthiadiazole (BBT), with high electron affinity, is widely utilized as the electron acceptor in constructing donor-acceptor-donor (D-A-D) structured fluorophores with intensive near-infrared (NIR) absorption and NIR-II fluorescence. Until now, numerous BBT-based NIR-II dyes have been employed in tumor phototheranostics due to their exceptional structure tunability, biocompatibility, and photophysical properties. This review systematically overviews the research progress of BBT-based small molecular NIR-II dyes and focuses on molecule design and bioapplications. First, the molecular engineering strategies to fine-tune the photophysical properties in constructing the high-performance BBT-based NIR-II fluorophores are discussed in detail. Then, their biological applications in optical imaging and phototherapy are highlighted. Finally, the current challenges and future prospects of BBT-based NIR-II fluorescent dyes are also summarized. This review is believed to significantly promote the further progress of BBT-derived NIR-II fluorophores for cancer phototheranostics.

NIR-II Emissive Superoxide Radical Photogenerator for Photothermal/Photodynamic Therapy against Hypoxic Tumor

Due to the "Achilles' heels" of hypoxia, complicated location in solid tumor, small molecular photosensitizers with second near-infrared window (NIR-II) fluorescence, type-I photodynamic therapy (PDT), and photothermal therapy (PTT) have attracted great attention. However, these photosensitizers are still few but yet challenging. Herein, an "all in one" NIR-II acceptor-donor-acceptor fused-ring photosensitizer, Y6-Th, is presented for the in-depth diagnosis and efficient treatment of cancer. Benefiting from the strong intramolecular charge transfer, promoted highly efficient intersystem crossing, largely p-conjugated fused-ring structure, and reduced planarity, the fabricated nanoparticles (Y6-Th nanoparticles) can emit NIR-II fluorescence with the peak located at 1020 nm, exclusively generate O2•- for type-I PDT, and display excellent PTT performance under an 808 nm laser stimulation. These characteristics make Y6-Th a distinguished NIR-wavelength-triggered phototheranostic agent, which can effectively therapy the hypoxic tumor using NIR-II-fluorescence-guided type-I PDT/PTT. This work provides a valuable guideline for fabricating high-performing NIR-II emissive superoxide radical photogenerators.

Pt-Se-Bonded Nanoprobe for High-Fidelity Detection of Non-small Cell Lung Cancer and Enhancement of NIR II Photothermal Therapy

Non-small cell lung cancer (NSCLC) accounts for a high proportion of lung cancer cases globally, but early detection remains challenging, and insufficient oxygen supply at tumor sites leads to suboptimal treatment outcomes. Therefore, the development of core-shell Au@Pt-Se nanoprobes (Au@Pt-Se NPs) with peptide chains linked through Pt-Se bonds was designed and synthesized for NSCLC biomarker protein calcium-activated neutral protease 2 (CAPN2) and photothermal therapy (PTT) enhancement. The NP can be specifically cleaved by CAPN2, resulting in fluorescence recovery to realize the detection. The Pt-Se bonds exhibit excellent resistance to biologically abundant thiols such as glutathione, thus avoiding "false-positive" results and enabling precise detection of NSCLC. Additionally, the platinum (Pt) shell possesses catalase-like properties that catalyze the generation of oxygen from endogenous hydrogen peroxide within the tumor, thereby reducing hypoxia-inducible factor-1α (HIF-1α) levels and alleviating the hypoxic environment at the tumor site. The Au@Pt-Se NPs exhibit strong absorption bands, enabling the possibility of PTT in the near-infrared II region (NIR II). This study presents an effective approach for the early detection of NSCLC while also serving as an oxygen supplier to alleviate the hypoxic environment and enhance NIR II PTT.

Multifunctional Photothermal Hydrogel in the Second Near-Infrared Window for Localized Tumor Therapy

A copper selenide-embedded gellan gum hydrogel (Cu2-xSe@GG) is designed as an "all-in-one" antitumor agent. The obtained nanocomposite hydrogel exhibits strong near-infrared light absorption and high photothermal conversion efficiency in both the NIR-I and NIR-II biowindows. The photothermal conversion efficiency achieves 58.8% under the irradiation of 0.75 W/cm2 with a 1064 nm laser. Furthermore, the nanocomposite hydrogel has catalase- and peroxidase-mimicking activities, which could alter the tumor microenvironment by reducing hypoxia and/or increasing the production of reactive oxygen species. Moreover, the multifunctional Cu2-xSe@GG nanocomposite hydrogel can also be used as an immune agonist resiquimod (R848) carrier to promote immune regulation and enhance the therapeutic effect. The single-syringe R848/Cu2-xSe@GG treatment achieves synergetic photothermal immunotherapy, showing 97.4% of tumor regression rate from an initial large tumor of 300 mm3.

Accumulative Rolling Mg/PLLA Composite Membrane with Lamellar Heterostructure for Enhanced Bacteria Inhibition and Rapid Bone Regeneration

Developing composite materials with optimized mechanics, degradation, and bioactivity for bone regeneration has long been a crucial mission. Herein, a multifunctional Mg/Poly-l-lactic acid (Mg/PLLA) composite membrane based on the "materials plain" concept through the accumulative rolling (AR) method is proposed. Results show that at a rolling ratio of 75%, the comprehensive mechanical properties of the membrane in the rolling direction are self-reinforced significantly (elongation at break ≈53.2%, tensile strength ≈104.0 MPa, Young's modulus ≈2.13 GPa). This enhancement is attributed to the directional arrangement and increased crystallization of PLLA molecular chains, as demonstrated by SAXS and DSC results. Furthermore, the AR composite membrane presents a lamellar heterostructure, which not only avoids the accumulation of Mg microparticles (MgMPs) but also regulates the degradation rate. Through the contribution of bioactive MgMPs and their photothermal effect synergistically, the membrane effectively eliminates bacterial infection and accelerates vascularized bone regeneration both in vitro and in vivo. Notably, the membrane exhibits outstanding rat skull bone regeneration performance in only 4 weeks, surpassing most literature reports. In short, this work develops a composite membrane with a "one stone, four birds" effect, opening an efficient avenue toward high-performance orthopedic materials.

Dual Key-Activated Nir-I/II Fluorescence Probe for Monitoring Photodynamic and Photothermal Synergistic Therapy Efficacy

As cancer markers, hydrogen peroxide (H2 O2 ) and viscosity play an essential role in the development of tumors. Meanwhile, based on the performance of near-infrared (NIR) fluorescence imaging and the high efficiency of photodynamic therapy (PDT) and photothermal therapy (PTT) synergistic therapy, it is urgent to develop a dual-key (H2 O2 and viscosity) activated fluorescence probe for cancer phototherapy. Herein, a NIR-I/II fluorescence probe named BX-B is reported. In the presence of both H2 O2 and viscosity, the fluorescence signal of NIR-I (810 nm) and NIR-II (945 nm) can be released. In the presence of H2 O2 , the PDT and PTT effects are observed. BX-B is used to monitor its therapeutic effects in cancer cells and tumor-bearing mice due to the increased viscosity caused by PDT and PTT. In addition, the tumors of mice treated with BX-B are almost completely ablated after the laser irradiation based on its PDT and PTT synergistic therapy. This work provides a reliable platform for effective cancer treatment and immediate evaluation of therapeutic effects.

Tumor microenvironment-mediated NIR-I-to-NIR-II transformation of Au self-assembly for theranostics

The misdiagnosis of tumors due to insufficient penetration depth or signal interference and damage to normal tissues due to indiscriminate treatment are the biggest challenges in using photothermal agents for clinical translation. To overcome these limitations, a strategy of switching from the near-infrared (NIR)-I region to the NIR-II region was developed based on tumor microenvironment (TME)-mediated gold (Au) self-assembly. Using zeolitic imidazolate framework-8 (ZIF-8) metal-organic framework-coated gold nanorods (AuNRs@ZIF-8) as a model photothermal agent, we demonstrated that only a NIR-I photoacoustic imaging signal was observed in normal tissue because ZIF-8 could prevent the aggregation of AuNRs. However, when ZIF-8 dissociated in the TME, the AuNRs aggregated to activate NIR-II photoacoustic imaging and attenuate the NIR-I signal, thereby allowing an accurate diagnosis of tumors based on signal transformation. Notably, TME-activated NIR-II photothermal therapy could also inhibit tumor growth. Therefore, this TME-activated NIR-I-to-NIR-II switching strategy could improve the accuracy of deep-tumor diagnoses and avoid the injury caused by undifferentiated treatment. STATEMENT OF SIGNIFICANCE: Photothermal agents used for photoacoustic imaging and photothermal therapy have garnered great attention for tumor theranostics. However, always "turned on" near-infrared (NIR)-I laser (700-1000 nm)-responsive photothermal agents face issues of penetration depth and damage to normal tissues. In contrast, tumor microenvironment-activated NIR-II "smart" photothermal agents exhibit deeper penetration depth and tumor selectivity. Therefore, a NIR-I-to-NIR-II switching strategy was developed based on tumor microenvironment-mediated Au self-assembly. This work provides a new strategy for developing tumor microenvironment-activated NIR-II smart photothermal agents.

Beyond traditional light: NIR-II light-activated photosensitizers for cancer therapy

With increasing demand for the accurate and safe treatment of cancer, non-invasive photodynamic therapy (PDT) has received widespread attention. However, most conventional photosensitizers are typically excited by short-wavelength visible light (400-700 nm), thus substantially hindering the penetration of light and the therapeutic effectiveness of the PDT procedure. Fortunately, near-infrared (NIR) light (>700 nm), in particular, light in the second near-infrared region (NIR-II, 1000-1700 nm) has a higher upper radiation limit, greater tissue tolerance, and deeper tissue penetration compared with traditional short-wavelength light excitation, and shows considerable potential in the clinical treatment of cancer. Therefore, it is of paramount importance and clinical value to develop photosensitizers that are excited by NIR-II light. In this review, for the first time we focus completely on recent progress made with various NIR-II photosensitizers for cancer treatment via PDT, and we briefly present the ongoing challenges and prospects of currently developed NIR-II photosensitizers for clinical practice in the near future. We believe that the above topics will inspire broad interest in researchers from interdisciplinary fields that include chemistry, materials science, pharmaceuticals, and clinical medicine, and provide insightful perspectives for exploiting new NIR-II photosensitizers for biomedical applications.

Cholesterol Metabolism Modulation Nanoplatform Improves Photo-Immunotherapeutic Effect in Oral Squamous Cell Carcinoma

Impressive results in cancer treatment have been obtained through immunotherapy. However, abnormally high cholesterol metabolism in the tumor microenvironment (TME) leads to poor immunogenicity or even immunosuppression, which dramatically reduces the clinical response of patients with oral squamous cell carcinoma (OSCC) to immunotherapy. In this study, a cholesterol-modulating nanoplatform (PYT NP) is developed to restore the normal immune microenvironment, significantly inhibiting SQLE (an essential gene for cholesterol biosynthesis in tumor cells) by releasing terbinafine, thereby reducing cholesterol in the TME and suppressing tumor cell proliferation. In addition, the nanoplatform is equipped with a second near-infrared (NIR-II) photosensitizer, Y8, which triggers immunogenic cell death of tumor cells, thereby promoting intra-tumor infiltration and immune activation via the production of damage-associated molecular patterns for photoimmunotherapy. PYT NPs show great promise in stimulating strong cholesterol-modulating anticancer immunity combined with photoimmunotherapy, opening up a new avenue for sensitized OSCC immunotherapy.

Intelligent nanomaterials for cancer therapy: recent progresses and future possibilities

Intelligent nanomedicine is currently one of the most active frontiers in cancer therapy development. Empowered by the recent progresses of nanobiotechnology, a new generation of multifunctional nanotherapeutics and imaging platforms has remarkably improved our capability to cope with the highly heterogeneous and complicated nature of cancer. With rationally designed multifunctionality and programmable assembly of functional subunits, the in vivo behaviors of intelligent nanosystems have become increasingly tunable, making them more efficient in performing sophisticated actions in physiological and pathological microenvironments. In recent years, intelligent nanomaterial-based theranostic platforms have showed great potential in tumor-targeted delivery, biological barrier circumvention, multi-responsive tumor sensing and drug release, as well as convergence with precise medication approaches such as personalized tumor vaccines. On the other hand, the increasing system complexity of anti-cancer nanomedicines also pose significant challenges in characterization, monitoring and clinical use, requesting a more comprehensive and dynamic understanding of nano-bio interactions. This review aims to briefly summarize the recent progresses achieved by intelligent nanomaterials in tumor-targeted drug delivery, tumor immunotherapy and temporospatially specific tumor imaging, as well as important advances of our knowledge on their interaction with biological systems. In the perspective of clinical translation, we have further discussed the major possibilities provided by disease-oriented development of anti-cancer nanomaterials, highlighting the critical importance clinically-oriented system design.

Synergistic Nanomedicine: Photodynamic, Photothermal and Photoimmune Therapy in Hepatocellular Carcinoma: Fulfilling the Myth of Prometheus?

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer, with high morbidity and mortality, which seriously threatens the health and life expectancy of patients. The traditional methods of treatment by surgical ablation, radiotherapy, chemotherapy, and more recently immunotherapy have not given the expected results in HCC. New integrative combined therapies, such as photothermal, photodynamic, photoimmune therapy (PTT, PDT, PIT), and smart multifunctional platforms loaded with nanodrugs were studied in this review as viable solutions in the synergistic nanomedicine of the future. The main aim was to reveal the latest findings and open additional avenues for accelerating the adoption of innovative approaches for the multi-target management of HCC. High-tech experimental medical applications in the molecular and cellular research of photosensitizers, novel light and laser energy delivery systems and the features of photomedicine integration via PDT, PTT and PIT in immuno-oncology, from bench to bedside, were introspected. Near-infrared PIT as a treatment of HCC has been developed over the past decade based on novel targeted molecules to selectively suppress cancer cells, overcome immune blocking barriers, initiate a cascade of helpful immune responses, and generate distant autoimmune responses that inhibit metastasis and recurrences, through high-tech and intelligent real-time monitoring. The process of putting into effect new targeted molecules and the intelligent, multifunctional solutions for therapy will bring patients new hope for a longer life or even a cure, and the fulfillment of the myth of Prometheus.

Multifunctional AIE Nanosphere-Based "Nanobomb" for Trimodal Imaging-Guided Photothermal/Photodynamic/Pharmacological Therapy of Drug-Resistant Bacterial Infections

Injudicious or inappropriate use of antibiotics has led to the prevalence of drug-resistant bacteria, posing a huge menace to global health. Here, a self-assembled aggregation-induced emission (AIE) nanosphere (AIE-PEG₁₀₀₀ NPs) that simultaneously possesses near-infrared region II (NIR-II) fluorescence emissive, photothermal, and photodynamic properties is prepared using a multifunctional AIE luminogen (AIE-4COOH). The AIE-PEG₁₀₀₀ NPs were encapsulated with teicoplanin (Tei) and ammonium bicarbonate (AB) into lipid nanovesicles to form a laser-activated "nanobomb" (AIE-Tei@AB NVs) for the multimodal theranostics of drug-resistant bacterial infections. In vivo experiments validate that the "nanobomb" enables high-performance NIR-II fluorescence, infrared thermal, and ultrasound (AB decomposition during the photothermal process to produce numerous CO₂/NH₃ bubbles, which is an efficient ultrasound contrast agent) imaging of multidrug-resistant bacteria-infected foci after intravenous administration of AIE-Tei@AB NVs followed by 660 nm laser stimulation. The highly efficient photothermal and photodynamic features of AIE-Tei@AB NVs, combined with the excellent pharmacological property of rapidly released Tei during bubble generation and NV disintegration, collectively promote broad-spectrum eradication of three clinically isolated multidrug-resistant bacteria strains and rapid healing of infected wounds. This multimodal imaging-guided synergistic therapeutic strategy can be extended for the theranostics of superbugs.

In Vivo Precision Evaluation of Lymphatic Function by SWIR Luminescence Imaging with PbS Quantum Dots

Advancements in lymphography technology are essential for comprehensive investigation of the lymphatic system and its function. Here, a shortwave infrared (SWIR) luminescence imaging of lymphatic vessels is proposed in both normal and lymphatic dysfunction in rat models with PbS quantum dots (PbS Qdots). The lymphography with PbS Qdots can clearly and rapidly demonstrate the normal lymphatic morphology in both the tail and hind limb. More importantly, compared to ICG, SWIR luminescence imaging with PbS Qdots can easily identify the dominant lymphatic vessel and node with higher luminescence signal in rats. Moreover, lymphatic pump is identified as segment contracting sections with a size of ≈1 cm in rat by in vivo SWIR lymphograhy, which propose a direct feature for precise evaluation of lymphatic function. Notably, in vivo SWIR luminescence imaging with PbS Qdots also clearly deciphers the in vivo pattern of morphological and function recovery from lymphatic system in rat model. In summary, SWIR luminescence imaging with PbS Qdots can improve the lymphography and thus deepen the understanding of the morphology and structure of the lymphatic system as well as lymphatic function such as lymphatic pump, which will facilitate the diagnosis of lymphatic dysfunction in the future.

In Vivo Fluorescence Imaging-Guided Development of Near-Infrared AIEgens

In vivo fluorescence imaging has received extensive attention due to its distinguished advantages of excellent biosafety, high sensitivity, dual temporal-spatial resolution, real-time monitoring ability, and non-invasiveness. Aggregation-induced emission luminogens (AIEgens) with near-infrared (NIR) absorption and emission wavelengths are ideal candidate for in vivo fluorescence imaging for their large Stokes shift, high brightness and superior photostability. NIR emissive AIEgens provide deep tissue penetration depth as well as low interference from tissue autofluorescence. Here in this review, we summarize the molecular engineering strategies for constructing NIR AIEgens with high performances, including extending π-conjugation system and strengthen donor (D)-acceptor (A) interactions. Then the encapsulation strategies for increasing water solubility and biocompatibility of these NIR AIEgens are highlighted. Finally, the challenges and prospect of fabricating NIR AIEgens for in vivo fluorescence imaging are also discussed. We hope this review would provide some guidelines for further exploration of new NIR AIEgens.

D-A-D organic small molecules with AIE effect for fluorescence imaging guided photothermal therapy

Near infrared (NIR) fluorescent organic molecules as fluorescent probes accurately guide photothermal therapy as a potential antitumor method. However, the aggregation and quenching of organic fluorescent molecules and poor tissue permeability greatly limit their therapeutic effect and clinical transformation. In this paper, with a D-A-D structure as the molecular skeleton, cyclopentadithiophene (CPDT) as the donor (D), diketopyrrolopyrrole (DPP) as the acceptor (A), and long-chain isooctane as the shielding unit, organic fluorescent small molecules with a strong absorption band and bright NIR-II emission were synthesized. Then, tetraphenylethylene (TPE) molecules with typical AIE structure characteristics were introduced on both sides of the organic fluorescent small molecules, and an organic small molecular fluorophore (TDA) with AIE characteristics and the photothermal effect was designed. Through a series of experimental characterization techniques, it is proved that TDA NPs have good biocompatibility and tissue permeability, and can accurately locate the tumor location through NIR-II fluorescence imaging to achieve local photothermal treatment of tumors.

Molecular Oligomerization and Donor Engineering Strategies for Achieving Superior NIR-II Fluorescence Imaging and Thermotherapy under 1064 nm Laser Irradiation

An enormous challenge still exists for designing molecules with the second near-infrared (NIR-II, 1000-1700 nm) window absorption, NIR-II fluorescence emission, and batch-to-batch reproducibility, which is the premise for high-performance NIR-II phototheranostics. Although organic small molecules and polymers have been largely explored for phototheranostics, it is difficult to satisfy the above three elements simultaneously. In this work, molecular oligomerization (the general structure is S-D-A-D'-A-D-S) and donor engineering (changing the donor linker D') strategies are applied to design phototheranostic agents. Such strategies are proved to be efficient in adjusting molecular configuration and energy level, affecting the optical and thermal properties. Three oligomers (O-T, O-DT, and O-Q) are further prepared into water-soluble nanoparticles (NPs). Particularly, the O-T NPs exhibit a higher molar extinction coefficient at 1064 nm (≈4.3-fold of O-DT NPs and ≈4.8-fold of O-Q NPs). Furthermore, the O-T NPs show the highest NIR-II fluorescence brightness and heating capacity (PCE = 73%) among the three NPs under 1064 nm laser irradiation and served as agents for NIR-II imaging guided in vivo photothermal therapy. Overall, by using molecular oligomerization and donor engineering strategies, a powerful example of constructing high-performance NIR-II phototheranostics for clinical translation is given.

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.

Recent Advances of NIR-II Emissive Semiconducting Polymer Dots for In Vivo Tumor Fluorescence Imaging and Theranostics

Accurate diagnosis and treatment of tumors, one of the top global health problems, has always been the research focus of scientists and doctors. Near-infrared (NIR) emissive semiconducting polymers dots (Pdots) have demonstrated bright prospects in field of in vivo tumor fluorescence imaging owing to some of their intrinsic advantages, including good water-dispersibility, facile surface-functionalization, easily tunable optical properties, and good biocompatibility. During recent years, much effort has been devoted to developing Pdots with emission bands located in the second near-infrared (NIR-II, 1000-1700 nm) region, which hold great advantages of higher spatial resolution, better signal-to-background ratios (SBR), and deeper tissue penetration for solid-tumor imaging in comparison with the visible region (400-680 nm) and the first near-infrared (NIR-I, 680-900 nm) window, by virtue of the reduced tissue autofluorescence, minimal photon scattering, and low photon absorption. In this review, we mainly summarize the latest advances of NIR-II emissive semiconducting Pdots for in vivo tumor fluorescence imaging, including molecular engineering to improve the fluorescence quantum yields and surface functionalization to elevate the tumor-targeting capability. We also present several NIR-II theranostic Pdots used for integrated tumor fluorescence diagnosis and photothermal/photodynamic therapy. Finally, we give our perspectives on future developments in this field.

A Precipitation-Enhanced Emission (PEE) Strategy for Increasing the Brightness and Reducing the Liver Retention of NIR-II Fluorophores

The lack of organic fluorophores with high quantum yields (QYs) and low liver retention in the second near-infrared (NIR-II) window has become a bottleneck in the bioimaging field. An approach to address these problems is proposed by encapsulating phosphorylated fluorescent dyes into biodegradable calcium phosphate nanoparticles. First, an NIR-II molecule, LJ-2P, is designed with increased water solubility by introducing two phosphate groups. Meanwhile, LJ-2P co-precipitates with calcium ions to form LJ-2P nanoparticles (NPs). The QYs of LJ-2P NPs in aqueous solution is increased by 36.57-fold to 5.12% compared with that of LJ-2P. This unique phenomenon is named as precipitation-enhanced emission (PEE), whose detailed mechanism is explored by femtosecond transient absorption. It is demonstrated that co-precipitation of LJ-2P with calcium ions changes the micro-environment, which restricts the molecular rotation and reduces the interaction of water molecules, especially the excited-state proton transfer. In addition, due to the pH-sensitive nature, more than 80% of the LJ-2P NPs are metabolized in the liver within 24 h. Based on the excellent optical properties and good biocompatibility, high-contrast vascular visualization and breast tumor detecting are achieved. This strategy can apply to other NIR-II fluorophores to achieve high QYs and low liver retention.

Recent advances in NIR-II fluorescence based theranostic approaches for glioma

Gliomas are among the most common malignant tumors in the central nervous system and lead to poor life expectancy. However, the effective treatment of gliomas remains a considerable challenge. The recent development of near infrared (NIR) II (1000-1700 nm) theranostic agents has led to powerful strategies in diagnosis, targeted delivery of drugs, and accurate therapy. Because of the high capacity of NIR-II light in deep tissue penetration, improved spatiotemporal resolution can be achieved to facilitate the in vivo detection of gliomas via fluorescence imaging, and high contrast fluorescence imaging guided surgery can be realized. In addition to the precise imaging of tumors, drug delivery nano-platforms with NIR-II agents also allow the delivery process to be monitored in real-time. In addition, the combination of targeted drug delivery, photodynamic therapy, and photothermal therapy in the NIR region significantly improves the therapeutic effect against gliomas. Thus, this mini-review summarizes the recent developments in NIR-II fluorescence-based theranostic agents for glioma treatment.

Lateral Heterostructured Vis-NIR Photodetectors with Multimodal Detection for Rapid and Precise Classification of Glioma

Precise diagnosis of the boundary and grade of tumors is especially important for surgical dissection. Recently, visible and near-infrared (Vis-NIR) absorption differences of tumors are demonstrated for a precise tumor diagnosis. Here, a template-assisted sequential printing strategy is investigated to construct lateral heterostructured Vis-NIR photodetectors, relying on the up-conversion nanoparticles (UCNPs)/perovskite arrays. Under the sequential printing process, the synergistic effect and co-confinement are demonstrated to induce the UCNPs to cover both sides of the perovskite microwire. The side-wrapped lateral heterogeneous UCNPs/perovskite structure exhibits more satisfactory responsiveness to Vis-NIR light than the common fully wrapped structure, due to sufficient visible-light-harvesting ability. The Vis-NIR photodetectors with R reaching 150 mA W^-1 at 980 nm and 1084 A W^-1 at 450 nm are employed for the rapid classification of glioma. The detection accuracy rate of 99.3% is achieved through a multimodal analysis covering the Vis-NIR light, which provides a reliable basis for glioma grade diagnosis. This work provides a concrete example for the application of photodetectors in tumor detection and surgical diagnosis.