Near-infrared small molecule coupled with rigidness and flexibility for high-performance multimodal imaging-guided photodynamic and photothermal synergistic therapy

A perylene diimide probe for NIR-II fluorescence imaging guided photothermal and type I/type II photodynamic synergistic therapy

Phototherapy has garnered significant attention in the past decade. Photothermal and photodynamic synergistic therapy combined with NIR fluorescence imaging has been one of the most attractive treatment options because of the deep tissue penetration, high selectivity and excellent therapeutic effect. Benefiting from the superb photometrics and ease of modification, perylene diimide (PDI) and its derivatives have been employed as sensing probes and therapeutic agents in the biological and biomedical research fields, and exhibiting excellent potential. Herein, we reported the development of a novel organic small-molecule phototherapeutic agent, PDI-TN. The absorption of PDI-TN extends into the NIR region, which provides feasibility for NIR phototherapy. PDI-TN overcomes the traditional Aggregation-Caused Quenching (ACQ) effect and exhibits typical characteristics of Aggregation-Induced Emission (AIE). Subsequently, PDI-TN NPs were obtained by using an amphiphilic triblock copolymer F127 to encapsulate PDI-TN. Interestingly, the PDI-TN NPs not only exhibit satisfactory photothermal effects, but also can generate O2•- and 1O2 through type I and type II pathways, respectively. Additionally, the PDI-TN NPs emit strong fluorescence in the NIR-II region, and show outstanding therapeutic potential for in vivo NIR-II fluorescence imaging. To our knowledge, PDI-TN is the first PDI derivative used for NIR-II fluorescence imaging-guided photodynamic and photothermal synergistic therapy, which suggests excellent potential for future biological/biomedical applications.

Side Chain Programming Synchronously Enhances the Photothermal Conversion Efficiency and Photodynamic Activity of A-D-A Photosensitizers

Synchronously improving the photothermal conversion efficiency and photodynamic activity of organic small molecule photosensitizers is crucial for their further wide application in cancer treatment. Recently, the emerging A-D-A photosensitizer-based phototherapy systems have attracted great interest due to their plentiful inherent merits. Herein, we propose a design strategy for A-D-A photosensitizers with synchronously enhanced photothermal conversion and reactive oxygen species (ROS) generation efficiencies. Side chain programming is carried out to design three A-D-A photosensitizers (IDT-H, IDT-Br, IDT-I) containing hexyl, bromohexyl, and iodohexyl side chains, respectively. Theoretical calculations confirm that a bulky iodine atom could weaken the intermolecular π-π stacking and enhance spin-orbit coupling constants of IDT-I. These molecular mechanisms enable IDT-I nanoparticles (NPs) to exhibit 2.4-fold and 1.7-fold higher ROS generation efficiency than that of IDT-H NPs and IDT-Br NPs, respectively, as well as the highest photothermal conversion efficiency. Both the experimental results in vitro and in vivo verify that IDT-I NPs are perfectly qualified for the mission of photothermal and photodynamic synergistic therapy. Therefore, in this contribution, we provide a promising perspective for the design of A-D-A photosensitizers with simultaneously improved photothermal and photodynamic therapy ability.

End Group Engineering for Constructing A-D-A Fused-Ring Photosensitizers with Balanced Phototheranostics Performance

Phototheranostics continues to flourish in cancer treatment. Due to the competitive relationships between these photophysical processes of fluorescence emission, photothermal conversion, and photodynamic action, it is critical to balance them through subtle photosensitizer designs. Herein, it is provided a useful guideline for constructing A-D-A photosensitizers with superior phototheranostics performance. Various cyanoacetate group-modified end groups containing ester side chains of different length are designed to construct a series of A-D-A photosensitizers (F8CA1 ∼ F8CA4) to study the structure-property relationships. It is surprising to find that the photophysical properties of A-D-A photosensitizers can be precisely regulated by these tiny structural changes. The results reveal that the increase in the steric hindrance of ester side chains has positive impacts on their photothermal conversion capabilities, but adverse impacts on the fluorescence emission and photodynamic activities. Notably, these tiny structural changes lead to their different aggregation behavior. The molecule mechanisms are detailedly explained by theoretical calculations. Finally, F8CA2 nanoparticles with more balanced photophysical properties perform well in fluorescence imaging-guided photothermal and type I&II photodynamic synergistic cancer therapy, even under hypoxic conditions. Therefore, this work provides a novel practicable construction strategy for desired A-D-A photosensitizers.

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.

Multifunctional Nanoplatform for NIR-II Imaging-Guided Synergistic Oncotherapy

Tumors are a major public health issue of concern to humans, seriously threatening the safety of people's lives and property. With the increasing demand for early and accurate diagnosis and efficient treatment of tumors, noninvasive optical imaging (including fluorescence imaging and photoacoustic imaging) and tumor synergistic therapies (phototherapy synergistic with chemotherapy, phototherapy synergistic with immunotherapy, etc.) have received increasing attention. In particular, light in the near-infrared second region (NIR-II) has triggered great research interest due to its penetration depth, minimal tissue autofluorescence, and reduced tissue absorption and scattering. Nanomaterials with many advantages, such as high brightness, great photostability, tunable photophysical properties, and excellent biosafety offer unlimited possibilities and are being investigated for NIR-II tumor imaging-guided synergistic oncotherapy. In recent years, many researchers have tried various approaches to investigate nanomaterials, including gold nanomaterials, two-dimensional materials, metal sulfide oxides, polymers, carbon nanomaterials, NIR-II dyes, and other nanomaterials for tumor diagnostic and therapeutic integrated nanoplatform construction. In this paper, the application of multifunctional nanomaterials in tumor NIR-II imaging and collaborative therapy in the past three years is briefly reviewed, and the current research status is summarized and prospected, with a view to contributing to future tumor therapy.

Dual Activation of Calcium Channels Using Near-Infrared Responsive Conjugated Oligomer Nanoparticles for Precise Regulation of Blood Glucose Homeostasis

The rarity of efficient tools with spatiotemporal resolution and biocompatibility capabilities remains a major challenge for further progress and application of signaling manipulation. Herein, biomimetic conjugated oligomeric nanoparticles (CM-CONs) were developed to precisely modulate blood glucose homeostasis via the two-pronged activation of calcium channels. Under near-infrared (NIR) laser irradiation, CM-CONs efficiently generate local heat and reactive oxygen species (ROS), thereby simultaneously activating thermosensitive transient receptor potential V1 (TRPV1) and ROS-sensitive transient receptor potential A1 (TRPA1) calcium channels in small intestinal endocrine cells. The activation of the channels mediates inward calcium flow and then promotes glucagon-like peptide (GLP-1) secretion. Both in vitro and in vivo studies indicate that CM-CONs effectively regulate glucose homeostasis in diabetic model mice upon NIR light irradiation. This work develops a two-pronged attack strategy for accurately controlling blood glucose homeostasis, holding great prospects in the treatment for diabetes.

Application of exosomes as nanocarriers in cancer therapy

Cancer remains the most common lethal disease in the world. Although the treatment choices for cancer are still limited, significant progress has been made over the past few years. By improving targeted drug therapy, drug delivery systems promoted the therapeutic effects of anti-cancer medications. Exosome is a kind of natural nanoscale delivery system with natural substance transport properties, good biocompatibility, and high tumor targeting, which shows great potential in drug carriers, thereby providing novel strategies for cancer therapy. In this review, we present the formation, distribution, and characteristics of exosomes. Besides, extraction and isolation techniques are discussed. We focus on the recent progress and application of exosomes in cancer therapy in four aspects: exosome-mediated gene therapy, chemotherapy, photothermal therapy, and combination therapy. The current challenges and future developments of exosome-mediated cancer therapy are also discussed. Finally, the latest advances in the application of exosomes as drug delivery carriers in cancer therapy are summarized, which provide practical value and guidance for the development of cancer therapy.

J-Aggregation induced NIR-II fluorescence: an aza-BODIPY luminogen for efficient phototheranostics

The development of organic dyes with emission peaks in the second near-infrared window (NIR-II 1000-1700 nm) is highly desirable for in vivo imaging and imaging-guided phototheranostics. However, the lack of appropriate molecular frameworks and the challenges associated with complex synthesis critically hinder the development of new candidate fluorophores. J-Aggregation is considered as a smart and straightforward way to construct such a therapeutic agent with NIR-II fluorescence imaging properties. Here, we present the design and synthesis of an aza-BODIPY probe (TA). Upon encapsulation within the amphiphilic polymer DSPEG-PEG2000-NH2, TA underwent self-assembly and formed J-aggregates (TAJ NPs), which showed emission at 1020 nm. High spatial resolution and adequate signal-to-noise ratio of the TAJ NPs are demonstrated for noninvasive bioimaging of the vasculature, lymph nodes and bones of mice in the NIR-II region. Moreover, the TAJ NPs exhibited good tumor enrichment efficiency with reduced liver accumulation and significant imaging-guided phototherapy performance against lung cancer cells. Taken together, this work not only introduces a new NIR-II imaging and phototheranostic agent based on J-aggregates, but also provides insight into the development of versatile organic dyes for future clinical implementation.

Mitochondria-Targeting Multimodal Phototheranostics Based on Triphenylphosphonium Cation Modified Amphiphilic Pillararenes and A-D-A Fused-Ring Photosensitizers

Tumor-targeting phototheranostics has gradually developed as a powerful tool for the precise diagnosis and treatment of cancer. However, the designs of tumor-targeting phototheranostics agents with excellent multimodal phototherapy and fluorescence imaging (FLI) capability, as well as very few components, are still scarce and challenging for cancer treatment. Herein, a mitochondria-targeting multimodal phototheranostics system has been constructed by combining a designed amphiphilic pillararene WP5-2PEG-2TPP and the A-D-A fused-ring photosensitizer F8CA5. WP5-2PEG-2TPP is constructed by attaching the triphenylphosphonium cations to our previously reported dual PEG-functionalized amphiphilic pillararene, which can self-assemble into regular spherical nanocarriers with outstanding mitochondria targeting and water solubility. The A-D-A photosensitizer F8CA5 containing two methyl cyanoacetate group modified end groups displays superior photothermal conversion ability and dual type I/II photodynamic activity as well as strong NIR fluorescence emission. Through their strong union, multifunctional mitochondria-targeting phototheranostics agent F8CA5 NPs were obtained to be applied into FLI-guided synergistic photothermal and type I/II photodynamic therapy. As a result, F8CA5 NPs show good mitochondria-targeting and phototherapy effects in various tumor cells. Not only that, they can combat tumor hypoxia, which hinders the efficacy of photodynamic therapy. Therefore, this work provides a creative ideal for the construction of multifunctional tumor-targeting phototheranostic agents with excellent performance.

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.

Selenium-integrated conjugated oligomer nanoparticles with high photothermal conversion efficiency for NIR-II imaging-guided cancer phototheranostics in vivo

Second near-infrared (NIR-II) fluorescence imaging in the range of 1000-1700 nm has great prospects for in vivo imaging and theranostics monitoring. At present, few NIR-II probes with theranostics properties have been developed, especially the high-performance organic theranostics material remains underexploited. Herein, we demonstrate a selenium (Se)-tailoring method to develop high-efficient NIR-II imaging-guided material for in vivo cancer phototheranostics. Via Se-tailoring strategy, conjugated oligomer TPSe-based nanoparticles (TPSe NPs) achieve bright NIR-II emission up to 1400 nm and exhibit a relatively high photothermal conversion efficiency of 60% with good stability. Moreover, the TPSe NPs demonstrate their photothermal ablation of cancer cells in vitro and tumor in vivo with the guidance of NIR-II imaging. It is worth noting that the TPSe NPs have good biocompatibility without obvious side effects. Thus, this work provides new insight into the development of NIR-II theranostics agents.

Engineering of a GSH activatable photosensitizer for enhanced photodynamic therapy through disrupting redox homeostasis

Although disrupted redox homeostasis has emerged as a promising approach for tumor therapy, most existing photosensitizers are not able to simultaneously improve the reactive oxygen species level and reduce the glutathione (GSH) level. Therefore, designing photosensitizers that can achieve these two aspects of this goal is still urgent and challenging. In this work, an organic activatable near-infrared (NIR) photosensitizer, CyI-S-diCF₃, is developed for GSH depletion-assisted enhanced photodynamic therapy. CyI-S-diCF₃, composed of an iodinated heptamethine cyanine skeleton linked with a recognition unit of 3,5-bis(trifluoromethyl)benzenethiol, can specifically react with GSH by nucleophilic substitution, resulting in intracellular GSH depletion and redox imbalance. Moreover, the activated photosensitizer can produce abundant singlet oxygen (¹O₂) under NIR light irradiation, further heightening the cellular oxidative stress. By this unique nature, CyI-S-diCF₃ exhibits excellent toxicity to cancer cells, followed by inducing earlier apoptosis. Thus, our study may propose a new strategy to design an activatable photosensitizer for breaking the redox homeostasis in tumor cells.

Anti-Quenching NIR-II J-Aggregates of Benzo[c]thiophene Fluorophore for Highly Efficient Bioimaging and Phototheranostics

Molecular fluorophores with the second near-infrared (NIR-II) emission hold great potential for deep-tissue bioimaging owing to their excellent biocompatibility and high resolution. Recently, J-aggregates are used to construct long-wavelength NIR-II emitters as their optical bands show remarkable red shifts upon forming water-dispersible nano-aggregates. However, their wide applications in the NIR-II fluorescence imaging are impeded by the limited varieties of J-type backbone and serious fluorescence quenching. Herein, a bright benzo[c]thiophene (BT) J-aggregate fluorophore (BT6) with anti-quenching effect is reported for highly efficient NIR-II bioimaging and phototheranostics. The BT fluorophores are manipulated to have Stokes shift over 400 nm and aggregation-induced emission (AIE) property for conquering the self-quenching issue of the J-type fluorophores. Upon forming BT6 assemblies in an aqueous environment, the absorption over 800 nm and NIR-II emission over 1000 nm are boosted for more than 41 and 26 folds, respectively. In vivo visualization of the whole-body blood vessel and imaging-guided phototherapy results verify that BT6 NPs are excellent agent for NIR-II fluorescence imaging and cancer phototheranostics. This work develops a strategy to construct bright NIR-II J-aggregates with precisely manipulated anti-quenching properties for highly efficient biomedical applications.

End Group Nonplanarization Enhances Phototherapy Efficacy of A-D-A Fused-Ring Photosensitizer for Tumor Phototherapy

Enhancing the phototherapy efficacy of organic photosensitizers through molecular design is a fascinating but challenging task. Herein, we propose a simple design strategy to first realize the generation of superoxide anion radical (O₂^•-) by A-D-A fused-ring photosensitizers. Through replacing one cyano group of traditional end group with an ester group, we designed a novel nonplanar end group (A unit) to synthesize a novel A-D-A photosensitizer F8CA. In a comparison with its counterpart F8CN with the traditional end group, F8CA displays more loose packing and larger spin-orbit coupling constants. The F8CA nanoparticles showed higher photodynamic activities with the generation capability of singlet oxygen (¹O₂), hydroxyl radical (^•OH), and O₂^•-, while F8CN nanoparticles could only generate ¹O₂ and ^•OH. In addition, F8CA nanoparticles still remain high photothermal conversion efficiency (61%). As a result, F8CA nanoparticles perform well in hypoxia-tolerant tumor phototherapy. This study brings an effective design thought for A-D-A photosensitizers.

Reactive oxygen species-powered cancer immunotherapy: Current status and challenges

Reactive oxygen species (ROS) are crucial signaling molecules that can arouse immune system. In recent decades, ROS has emerged as a unique therapeutic strategy for malignant tumors as (i) it can not only directly reduce tumor burden but also trigger immune responses by inducing immunogenic cell death (ICD); and (ii) it can be facilely generated and modulated by radiotherapy, photodynamic therapy, sonodynamic therapy and chemodynamic therapy. The anti-tumor immune responses are, however, mostly downplayed by the immunosuppressive signals and dysfunction of effector immune cells within the tumor microenvironment (TME). The past years have seen fierce developments of various strategies to power ROS-based cancer immunotherapy by e.g. combining with immune checkpoints inhibitors, tumor vaccines, and/or immunoadjuvants, which have shown to potently inhibit primary tumors, metastatic tumors, and tumor relapse with limited immune-related adverse events (irAEs). In this review, we introduce the concept of ROS-powered cancer immunotherapy, highlight the innovative strategies to boost ROS-based cancer immunotherapy, and discuss the challenges in terms of clinical translation and future perspectives.

BODIPY-Based Photothermal Agents with Excellent Phototoxic Indices for Cancer Treatment

Here, we report six novel, easily accessible BODIPY-based agents for cancer treatment. In contrast to established photodynamic therapy (PDT) agents, these BODIPY-based compounds show additional photothermal activity and their cytotoxicity is not dependent on the generation of reactive oxygen species (ROS). The agents show high photocytotoxicity upon irradiation with light and low dark toxicity in different cancer cell lines in 2D culture as well as in 3D multicellular tumor spheroids (MCTSs). The ratio of dark to light toxicity (phototoxic index, PI) of these agents reaches striking values exceeding 830,000 after irradiation with energetically low doses of light at 630 nm. The oxygen-dependent mechanism of action (MOA) of established photosensitizers (PSs) hampers effective clinical deployment of these agents. Under hypoxic conditions (0.2% O₂), which are known to limit the efficiency of conventional PSs in solid tumors, photocytotoxicity was induced at the same concentration levels, indicating an oxygen-independent photothermal MOA. With a PI exceeding 360,000 under hypoxic conditions, both PI values are the highest reported to date. We anticipate that small molecule agents with a photothermal MOA, such as the BODIPY-based compounds reported in this work, may overcome this barrier and provide a new avenue to cancer therapy.

Acidity-Activatable Nanoparticles with Glucose Oxidase-Enhanced Photoacoustic Imaging and Photothermal Effect, and Macrophage-Related Immunomodulation for Synergistic Treatment of Biofilm Infection

The pH-responsive theragnostics exhibit great potential for precision diagnosis and treatment of diseases. Herein, acidity-activatable nanoparticles of GB@P based on glucose oxidase (GO) and polyaniline are developed for treatment of biofilm infection. Catalyzed by GO, GB@P triggers the conversion of glucose into gluconic acid and hydrogen peroxide (H₂ O₂ ), enabling an acidic microenvironment-activated simultaneously enhanced photothermal (PT) effect/amplified photoacoustic imaging (PAI). The synergistic effects of the enhanced PT efficacy of GB@P and H₂ O₂ accelerate biofilm eradication because the penetration of H₂ O₂ into biofilm improves the bacterial sensitivity to heat, and the enhanced PT effect destroys the expressions of extracellular DNA and genomic DNA, resulting in biofilm destruction and bacterial death. Importantly, GB@P facilitates the polarization of proinflammatory M1 macrophages that initiates macrophage-related immunity, which enhances the phagocytosis of macrophages and secretion of proinflammatory cytokines, leading to a sustained bactericidal effect and biofilm eradication by the innate immunomodulatory effect. Accordingly, the nanoplatform of GB@P exhibits the synergistic effects on the biofilm eradication and bacterial residuals clearance through a combination of the enhanced PT effect with immunomodulation. This study provides a promising nanoplatform with enhanced PT efficacy and amplified PAI for diagnosis and treatment of biofilm infection.

Injectable Carbon Dots-Based Hydrogel for Combined Photothermal Therapy and Photodynamic Therapy of Cancer

Hydrogel has been widely used in modern biotherapeutics due to its excellent biocompatibility, degradability, and high drug loading capacity. Among them, the construction of a phototherapy system including photosensitizer and hydrogel has aroused great interest in tumor therapy. Unfortunately, complex modifications are necessary to integrate different photosensitizers into the hydrogel. In this work, an injectable hydrogel was proposed by the Schiff base reaction between HA-CHO and carbon dots (CDs), which can realize PTT and PTT simultaneously. Notably, the CDs with rich -NH2 can be used not only as a photosensitizer but also as an efficient cross-linking agent for the Schiff base reaction to form a hydrogel network. The CD@Hydrogel with outstanding biosafety showed a high antitumor effect after 660 nm laser irradiation in in vitro and in vivo experiments. In summary, the CD@Hydrogel can not only realize PTT and PDT synergistic treatment under one light source but also act as a cross-linking agent to react with HA-CHO to form hydrogel, which is simple and efficient, providing a new strategy for cancer phototherapy.

Tumor imaging and photothermal therapy in second near infrared window: A systematic review and meta-analysis

Background

Second near-infrared window (NIR-II, 1000-1700 nm) technology for tumor imaging and photothermal therapy (PTT) is an innovative method for tumor diagnosis and treatment. The NIR-II probe can specifically identify tumor cells, and effectively convert light energy into heat energy under the irradiation of NIR laser, thus achieving the integration of non-invasive tumor diagnosis and treatment. In the present study, we conducted a systematic review and meta-analysis of preclinical investigations to corroborate the efficacy and safety of photothermal therapy.

Methods

Relevant preclinical data were retrieved by searching PubMed, Web of Science, CNKI, WANFANG and VIP information databases. And the acquired data were analyzed by RevMan Version 5.3 software.

Results

According to the inclusion criteria, forty-two articles relating to NIR-II tumor imaging and PTT were recruited for further in-depth analysis. The NIR-II photoacoustic and fluorescence imaging could quickly and accurately identify tumor in mice, manifesting higher signal intensity on tumor site than that of normal tissue. After PTT, the tumor volume of mice decreased miraculously [RR=8.49, 95%CI (4.64, 15.55), P<0.00001], and even disappeared completely [RR=7.01, 95%CI (3.04, 16.13), P<0.00001] with no potential risk of affecting the blood routine.

Conclusions

PTT guided by NIR-II imaging can effectively diagnose the tumor lesion and eliminate it with the advantages of non-invasive and higher biosafety.

Multimodal molecular imaging in the second near-infrared window

Near-infrared-II (NIR-II) fluorescence imaging has rapidly developed for the noninvasive investigation of physiological and pathological activities in living organisms with high spatiotemporal resolution. However, the penetration depth of fluorescence restricts its ability to provide deep anatomical information. Scientists integrate NIR-II fluorescence imaging with other imaging modes (such as photoacoustic and magnetic resonance imaging) to create multimodal imaging that can acquire detailed anatomical and quantitative information with deeper penetration by using multifunctional probes. This review offers a comprehensive picture of NIR-II-based dual/multimodal imaging probes and highlights advances in bioimaging and therapy. In addition, seminal studies and trends in multimodal imaging probes activated by NIR-II laser are summarized and several key points regarding future clinical translation are elucidated.

A Review on the Modification of Cellulose and Its Applications

The latest advancements in cellulose and its derivatives are the subject of this study. We summarize the characteristics, modifications, applications, and properties of cellulose. Here, we discuss new breakthroughs in modified cellulose that allow for enhanced control. In addition to standard approaches, improvements in different techniques employed for cellulose and its derivatives are the subject of this review. The various strategies for synthetic polymers are also discussed. The recent advancements in polymer production allow for more precise control, and make it possible to make functional celluloses with better physical qualities. For sustainability and environmental preservation, the development of cellulose green processing is the most abundant renewable substance in nature. The discovery of cellulose disintegration opens up new possibilities for sustainable techniques. Based on the review of recent scientific literature, we believe that additional chemical units of cellulose solubility should be used. This evaluation will evaluate the sustainability of biomass and processing the greenness for the long term. It appears not only crucial to dissolution, but also to the greenness of any process.

The principles, design and applications of fused-ring electron acceptors

Fused-ring electron acceptors (FREAs) have a donor-acceptor-donor structure comprising an electron-donating fused-ring core, electron-accepting end groups, π-bridges and side chains. FREAs possess beneficial features, such as feasibility to tailor their structures, high property tunability, strong visible and near-infrared light absorption and excellent n-type semiconducting characteristics. FREAs have initiated a revolution to the field of organic solar cells in recent years. FREA-based organic solar cells have achieved unprecedented efficiencies, over 20%, which breaks the theoretical efficiency limit of traditional fullerene acceptors (~13%), and boast potential operational lifetimes approaching 10 years. Based on the original studies of FREAs, a variety of new structures, mechanisms and applications have flourished. In this Review, we introduce the fundamental principles of FREAs, including their structures and inherent electronic and physical properties. Next, we discuss the way in which the properties of FREAs can be modulated through variations to the electronic structure or molecular packing. We then present the current applications and consider the future areas that may benefit from developments in FREAs. Finally, we conclude with the position of FREA chemistry, reflecting on the challenges and opportunities that may arise in the future of this burgeoning field.

Remote Manipulation of ROS-Sensitive Calcium Channel Using Near-Infrared-Responsive Conjugated Oligomer Nanoparticles for Enhanced Tumor Therapy In Vivo

The regulation of reactive oxygen species (ROS)-sensitive calcium (Ca²⁺) channels is of great significance in the treatment of tumors. Here, a simple ROS generation system is developed to activate ROS-sensitive ion channels for enhancing calcium-cascade-mediated tumor cell death under near-infrared (NIR) light irradiation. Upon irradiation with an 808 nm laser, a low-lethality amount of ROS facilitates plasmid transient potential receptor melastatin-2 (pTRPM2) gene release via cleavage of the Se-Se bonds, which contributed to enhancing the expression of TRPM2 in tumor cells. Meanwhile, ROS could potently activate TRPM2 for Ca²⁺ influx to inhibit early autophagy and to further induce intracellular ROS production, which ultimately led to cell death in TRPM2 expressing tumor cells. Both in vitro and in vivo data show that nanoparticles have an excellent therapeutic effect on cancer upon NIR light. This work presents a simple modality based on NIR light to remotely control the ROS-sensitive ion channel for cancer therapy.

Photovoltaic molecules with ultra-high light energy utilization for near-infrared laser triggered synergetic photodynamic and photothermal therapy

Photovoltaic molecules possess strong absorption in the near-infrared (NIR) region and are suitable for NIR laser-triggered phototherapy. Herein, the star molecule IEICO of organic photovoltaic materials, which has a narrow bandgap and large A-D-A conjugated structure, was prepared into water dispersive nanoparticles (NPs) through a simple self-assembly method. The obtained IEICO NPs showed a strong NIR absorption peak at 800 nm and a high ¹O₂ quantum yield of 11% and photothermal conversion efficiency of 85.4% under 808 nm laser irradiation. The ultra-high light energy utilization efficacy (∼96.4%) of the IEICO NPs enables their excellent phototherapeutic effect on tumors. The present work suggested the huge application potential of organic photovoltaic materials in the biomedical field.

A Dual-Locked Activatable Phototheranostic Probe for Biomarker-Regulated Photodynamic and Photothermal Cancer Therapy

Activatable phototheranostics holds promise for precision cancer treatment owing to the "turn-on" signals and therapeutic effects. However, most activatable phototheranostic probes only possess photodynamic therapy (PDT) or photothermal therapy (PTT), which suffer from poor therapeutic efficacy due to deficient cellular oxygen and complex tumor microenvironment. We herein report a dual-locked activatable phototheranostic probe that activates near-infrared fluorescence (NIRF) signals in tumor, triggers PDT in response to a tumor-periphery biomarker, and switches from PDT to PTT upon detecting a tumor-core-hypoxia biomarker. This PDT-PTT auto-regulated probe exhibits complete tumor ablation under the photoirradiation of a single laser source by producing cytotoxic singlet oxygen at the tumor periphery and generating hyperthermia at tumor-core where is too hypoxic for PDT. This dual-locked probe represents a promising molecular design approach toward precise cancer phototheranostics.

Synergistic photothermal-photodynamic-chemotherapy toward breast cancer based on a liposome-coated core-shell AuNS@NMOFs nanocomposite encapsulated with gambogic acid

A multifunctional nanoplatform with core–shell structure was constructed in one-pot for the synergistic photothermal, photodynamic, and chemotherapy against breast cancer. In the presence of gambogic acid (GA) as the heat-shock protein 90 (HSP90) inhibitor and the gold nanostars (AuNS) as the photothermal reagent, the assembly of Zr⁴⁺ with tetrakis (4-carboxyphenyl) porphyrin (TCPP) gave rise to the nanocomposite AuNS@ZrTCPP-GA (AZG), which in turn, further coated with PEGylated liposome (LP) to enhance the stability and biocompatibility, and consequently the antitumor effect of the particle. Upon cellular uptake, the nanoscale metal − organic framework (NMOF) of ZrTCPP in the resulted AuNS@ZrTCPP-GA@LP (AZGL) could be slowly degraded in the weak acidic tumor microenvironment to release AuNS, Zr⁴⁺, TCPP, and GA to exert the synergistic treatment of tumors via the combination of AuNS-mediated mild photothermal therapy (PTT) and TCPP-mediated photodynamic therapy (PDT). The introduction of GA serves to reduce the thermal resistance of the cell to re-sensitize PTT and the constructed nanoplatform demonstrated remarkable anti-tumor activity in vitro and in vivo. Our work highlights a facile strategy to prepare a pH-dissociable nanoplatform for the effective synergistic treatment of breast cancer.

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.

A-DA'D-A Structured Organic Phototheranostics for NIR-II Fluorescence/Photoacoustic Imaging-Guided Photothermal and Photodynamic Synergistic Therapy

Multimodal imaging-guided combinational phototherapies triggered by a single near-infrared (NIR) laser are highly desirable. However, their development is still a big challenge. Herein, we have developed an "acceptor-donor-acceptor'-donor-acceptor" structured organic phototheranostics (Y16-Pr) with strong light-harvesting ability in the NIR region. After being modified with polyethylene glycol (PEG), the obtained biocompatible nanoparticles (Y16-Pr-PEG NPs) could conduct NIR-II fluorescence imaging (FLI) and photoacoustic imaging (PAI) and perform photothermal therapy (PTT) and photodynamic therapy (PDT) simultaneously. Notably, Y16-Pr-PEG NPs showed an impressive photothermal conversion efficiency (PCE) of 82.4% under 808 nm laser irradiation. The irradiated NPs could also produce hydroxyl radicals (•OH) and singlet oxygen (¹O₂) for type I and type II PDT, respectively. In vivo and in vitro experiments revealed that the Y16-Pr-PEG NPs significantly inhibit tumor cell growth without apparent toxic side effects under laser irradiation. Overall, the single-laser-triggered multifunctional phototheranostic Y16-Pr-PEG NPs can achieve NIR-II FLI/PAI-guided synergistic PTT/PDT against tumors.

Near-Infrared Thermally Activated Delayed Fluorescence Nanoparticle: A Metal-Free Photosensitizer for Two-Photon-Activated Photodynamic Therapy at the Cell and Small Animal Levels

Thermally activated delayed fluorescence (TADF) materials with extremely small singlet-triplet energy offsets have opened new horizons for the development of metal-free photosensitizers for photodynamic therapy (PDT) in recent years. However, the exploration of near-infrared (NIR) TADF emitters for efficient two-photon-excited (TPE) PDT is still a formidable challenge, thus it has not been reported yet. In this study, purely organic photosensitizers (PSs) based on the TADF nanoparticles (NIR-TADF NPs) are designed for efficient TPE-PDT, which show excellent singlet oxygen generation ability. Thanks to the intrinsic two-photon excitation and NIR emission characteristics, the NIR-TADF NPs demonstrate promising potential in both single-photon-excited (SPE) and TPE NIR imaging. More importantly, the anti-tumor efficiency and biosafety of TADF-based PSs at the small animal level are confirmed in A549 tumor xenograft models under TPE laser irradiance, which will facilitate the practical biomedical applications of TADF materials. This work not only provides a promising strategy to develop metal-free PSs, but also expands the applied scope of TADF-based nanotherapeutics and advances their possible clinical translation in cancer therapy.

A Glutathione Activatable Photosensitizer for Combined Photodynamic and Gas Therapy under Red Light Irradiation

Although photodynamic therapy (PDT) is a promising approach for cancer therapy, most existing photosensitizers lack selectivity for tumor cells and the overexpressed glutathione (GSH) in tumor cells reduces the PDT efficiency. Therefore, designing photosensitizers that can be selectively activated within tumor cells and combine PDT with other therapeutic modalities represents a route for precise and efficient anticancer treatment. Herein, an organic activatable photosensitizer, CyI-DNBS, bearing 2,4-dinitrobenzenesulfonate (DNBS) as the cage group is reported. CyI-DNBS can be uptaken by cancer cells after which the cage group is selectively removed by the intracellular GSH, resulting in the generation of SO₂ for gas therapy. The reaction also releases the activated photosensitizer, CyI-OH, that can produce singlet oxygen (¹ O₂ ) under red light irradiation. Therefore, CyI-DNBS targets cancer cells for both photodynamic and SO₂ gas therapy treatments. The activatable photosensitizer provides a new approach for PDT and SO₂ gas synergistic therapy and demonstrates excellent anticancer effect in vivo.

Carrier-Free Delivery of Ultrasmall π-Conjugated Oligomer Nanoparticles with Photothermal Conversion over 80% for Cancer Theranostics

High-performance photothermal theranostics is urgently desired for cancer therapy because of their good controllability and noninvasive features. The relatively low photothermal conversion efficiency is still at the drawbacks because of the absence of efficient extraneous carriers. Herein, a carrier-free nanomedicine is developed to in vivo self-deliver organic photothermal agents for efficient cancer phototheranostics. By a facile self-assembly strategy, the near-infrared (NIR)-absorbing conjugated oligomer IDIC-4F is fabricated into a carrier-free nanoparticle (DCF-P), showing ultrasmall size of nearly 4.0 nm with a nearly 100% of drug loading capacity. Notably, DCF-P achieves a superhigh photothermal conversion efficiency of 80.5% that is far greater than that of IDIC-4F-loaded nanomicelle DCF-M (57.3%). With the guidance of NIR fluorescence and photoacoustic dual-imaging, it is verified that DCF-P could well achieve tumor-preferential accumulation and retention at 4 h postinjection, and meanwhile shows highly efficient in vivo tumor elimination with good biosafety. This study thus contributes a novel concept for designing ultrasmall nanoparticle characteristics of preferential accumulation in tumors, and also provides a strategy for creating high-performance carrier-free nanomedicine via highly ordered molecular stacking.

PdAu-based nanotheranostic agent for photothermal initiation and oxygen-independent free radicals generation

Due to a rapid proliferation of tumor cells leading to high oxygen consumption, solid tumors generally have the characteristics of hypoxia, which greatly limits the effect of photodynamic therapy sensitivity...

One-pot synthesis of multifunctional radiolabeled upconversion nanorods for enhanced multimodal imaging performance

We report on the synthesis of radiolabeled NaYF4: Yb/Er/Gd(18/2/60mol%) upconversion nanorods (UCNRs) by one-pot solvothermal process. The synthesized UCNRs were transferred to water by using poly(maleic anhydride-alt-1-octadecene)-mPEG 5000 (C18PMH-PEG). Subsequently...

Advances in FePt-involved nano-system design and application for bioeffect and biosafety

The rapid development and wide application of nanomaterial-involved theranostic agents have drawn surging attention for improving the living standard of humankind and healthcare conditions. In this review, recent developments in the design, synthesis, biocompatibility evaluation and potential nanomedicine applications of FePt-involved nano-systems are summarized, especially for cancer theranostic and biological molecule detection. The in vivo multi-model imaging capability is discussed in detail, including magnetic resonance imaging and computed tomography. Furthermore, we highlight the significant achievements of various FePt-involved nanotherapeutics for cancer treatment, such as drug delivery, chemodynamic therapy, photodynamic therapy, radiotherapy and immunotherapy. In addition, a series of FePt-involved nanocomposites are also applied for biological molecule detection, such as H₂O₂, glucose and naked-eye detection of cancer cells. Ultimately, we also summarize the challenges and prospects of FePt-involved nano-systems in nanocatalytic medicine. This review is expected to give a general pattern for the development of FePt-involved nano-systems in the field of nanocatalytic medicine and analytical determination.

Thermally Activated Delayed Fluorescence Material: An Emerging Class of Metal-Free Luminophores for Biomedical Applications

The development of simple, efficient, and biocompatible organic luminescent molecules is of great significance to the clinical transformation of biomaterials. In recent years, purely organic thermally activated delayed fluorescence (TADF) materials with an extremely small single-triplet energy gap (ΔEST ) have been considered as the most promising new-generation electroluminescence emitters, which is an enormous breakthrough in organic optoelectronics. By merits of the unique photophysical properties, high structure flexibility, and reduced health risks, such metal-free TADF luminophores have attracted tremendous attention in biomedical fields, including conventional fluorescence imaging, time-resolved imaging and sensing, and photodynamic therapy. However, there is currently no systematic summary of the TADF materials for biomedical applications, which is presented in this review. Besides a brief introduction of the major developments of TADF material, the typical TADF mechanisms and fundamental principles on design strategies of TADF molecules and nanomaterials are subsequently described. Importantly, a specific emphasis is placed on the discussion of TADF materials for various biomedical applications. Finally, the authors make a forecast of the remaining challenges and future developments. This review provides insightful perspectives and clear prospects towards the rapid development of TADF materials in biomedicine, which will be highly valuable to exploit new luminescent materials.

NIR-II Organic Nanotheranostics for Precision Oncotherapy

Precision oncotherapy can remove tumors without causing any apparent iatrogenic damage or irreversible side effects to normal tissues. Second near-infrared (NIR-II) nanotheranostics can simultaneously perform diagnostic and therapeutic modalities in a single nanoplatform, which exhibits prominent perspectives in tumor precision treatment. Among all NIR-II nanotheranostics, NIR-II organic nanotheranostics have shown an exceptional promise for translation in clinical tumor treatment than NIR-II inorganic nanotheranostics in virtue of their good biocompatibility, excellent reproducibility, desirable excretion, and high biosafety. In this review, recent progress of NIR-II organic nanotheranostics with the integration of tumor diagnosis and therapy is systematically summarized, focusing on the theranostic modes and performances. Furthermore, the current status quo, problems, and challenges are discussed, aiming to provide a certain guiding significance for the future development of NIR-II organic nanotheranostics for precision oncotherapy.

Conjugated Polymers: Optical Toolbox for Bioimaging and Cancer Therapy

Conjugated polymers (CPs) are capable of coordinating the electron coupling phenomenon to bestow powerful optoelectronic features. The light-harvesting and light-amplifying properties of CPs are extensively used in figuring out the biomedical issues with special emphasis on accurate diagnosis, effective treatment, and precise theranostics. This review summarizes the recent progress of CP materials in bioimaging, cancer therapeutics, and introduces the design strategies by rationally tuning the optical properties. The recent advances of CPs in bioimaging applications are first summarized and the challenges to clear the future directions of CPs in the respective area are discussed. In the following sections, the focus is on the burgeoning applications of CPs in phototherapy of the tumor, and illustrates the underlying photo-transforming mechanism for further molecular designing. Besides, the recent progress in the CPs-assistant drug therapy, mainly including drug delivery, gene therapeutic, the optical-activated reversion of tumor resistance, and synergistic therapy has also been discussed elaborately. In the end, the potential challenges and future developments of CPs on cancer diagnosis and therapy are also illuminated for the improvement of optical functionalization and the promotion of clinical translation.

Photochemical Synthesis of Nonplanar Small Molecules with Ultrafast Nonradiative Decay for Highly Efficient Phototheranostics

There has been much recent progress in the development of photothermal agents (PTAs) for biomedical and energy applications. Synthesis of organic PTAs typically involves noble metal catalysts and high temperatures. On the other hand, photochemical synthesis, as an alternative and green chemical technology, has obvious merits such as low cost, energy efficiency, and high yields. However, photochemical reactions have rarely been employed for the synthesis of PTAs. Herein, a facile and high-yield photochemical reaction is exploited for synthesizing nonplanar small molecules (NSMs) containing strong Michler's base donors and a tricyanoquinodimethane acceptor as high-performance PTAs. The synthesized NSMs show interesting photophysical properties including good absorption for photons of over 1000 nm wavelength, high near-infrared extinction coefficients, and excellent photothermal performance. Upon assembling the NSMs into nanoparticles (NSMN), they exhibit good biocompatibility, high photostability, and excellent photothermal conversion efficiency of 75%. Excited-state dynamic studies reveal that the NSMN has ultrafast nonradiative decay after photoexcitation. With these unique properties, the NSMN achieves efficient in vivo photoacoustic imaging and photothermal tumor ablation. This work demonstrates the superior potential of photochemical reactions for the synthesis of high-performance molecular PTAs.

A Diradicaloid Small Molecular Nanotheranostic with Strong Near-Infrared Absorbance for Effective Cancer Photoacoustic Imaging and Photothermal Therapy

Organic small molecule-based phototheranostics hold great promise for clinical translation by virtue of their distinct chemical structure, easy reproducibility, and high purity. However, reported molecular agents typically have relatively low optical absorbances, particularly over the near-infrared (NIR) region, and this limits their phototheranostic performance. Herein, we first exploit a diradicaloid molecular structure for enhancing NIR absorption to facilitate efficient photoacoustic imaging (PAI)-guided photothermal therapy (PTT). The donor-acceptor interaction in the diradicaloid molecule (DRM) leads to strong charge transfer resulting on obvious diradical characteristics, which is beneficial for NIR absorption. The DRM possesses excellent light-harvesting ability, with a mass extinction coefficient of ∼220 L g^-1 cm^-1, which is much higher than those (∼5-100 L g^-1 cm^-1) of typical organic molecules. After assembling into nanoparticles, they show good water dispersibility, good photostability, and impressive performance for PAI-guided PTT in vitro and in vivo. The impressive in vitro and in vivo performances show that developing small molecules with diradicaloid structures can be an effective approach for enhancing NIR harvesting capability for biomedical applications.

Coupling molecular rigidity and flexibility on fused backbones for NIR-II photothermal conversion

Great attention is being increasingly paid to photothermal conversion in the near-infrared (NIR)-II window (1000-1350 nm), where deeper tissue penetration is favored. To date, only a limited number of organic photothermal polymers and relevant theory have been exploited to direct the molecular design of polymers with highly efficient photothermal conversion, specifically in the NIR-II window. This work proposes a fused backbone structure locked via an intramolecular hydrogen bonding interaction and double bond, which favors molecular planarity and rigidity in the ground state and molecular flexibility in the excited state. Following this proposal, a particular class of NIR-II photothermal polymers are prepared. Their remarkable photothermal conversion efficiency is in good agreement with our strategy of coupling polymeric rigidity and flexibility, which accounts for the improved light absorption on going from the ground state to the excited state and nonradiative emission on going from the excited state to the ground state. It is envisioned that such a concept of coupling polymeric rigidity and flexibility will offer great inspiration for developing NIR-II photothermal polymers with the use of other chromophores.