Organic Semiconducting Macromolecular Dyes for NIR-II Photoacoustic Imaging and Photothermal Therapy

Owing to the unique advantages of photoacoustic imaging (PAI) and photothermal therapy (PTT) conducted over the near-infrared-II (NIR-II) window, the development of high-efficiency optical agents with NIR-II light responsiveness is of great significance. Despite the diversity of optical agents developed for NIR-II PAI and PTT, most of them are based on inorganic nanomaterials and small molecular dyes, whose biosafety and photostability need to be further assessed, respectively. Organic semiconducting macromolecular dyes (OSMDs) featuring a large semiconducting backbone are becoming alternative candidates for NIR-II PAI and PTT owing to their reliable biocompatibility, durable photostability, and ideal photothermal conversion capability. This paper reviews the current progress of OSMD-based PAI and PTT in the NIR-II optical window. The three main types of OSMDs with different skeleton architectures are introduced, and their applications for NIR-II PAI (tumor imaging, stem cell tracking, and vasculature imaging) and PTT (tumor ablation) are described. Viable strategies for further improving the NIR-II PAI performance of OSMDs are discussed. Finally, some major issues faced by OSMDs in NIR-II PAI and PTT are raised, and the future development directions of OSMDs are analyzed.     

Building Highly Light-Harvesting Near-Infrared AIEgens Using Triazole-Based Luminescent Core for Improved Intravital Afterglow Imaging

Development of the powerful building block is of great significance to construct materials with advanced properties. Herein, for the first time, a triazole-based luminescent core with balanced twist and conjugation is reported, which is explored to construct a D-A near-infrared (NIR) aggregation-induced emission luminogens (TPT-DCM) with high molar extinction coefficient, good brightness and excellent reactive oxygen species generation rate. These features enable it to function as a nanoprobe with ultralong NIR afterglow luminescence (up to 20 days) and ultrahigh tumor-to-liver signal ratio (up to 187) for in vivo deep-tissue afterglow imaging (with depth reaching 1.6 cm), in combination with chemiluminescence resonance energy transfer aided by active Schaap's dioxetane. Moreover, thanks to the excellent properties of the nanoprobe, the afterglow imaging-guided surgery navigation can be successfully conduced to remove the tumors especially with tiny size of < 1 mm. This is particularly useful to eliminate tumor residuals and prevent the cancer recurrence after surgery.     

Continuous Melt‐Drawing of Highly Aligned Flexible and Stretchable Semiconducting Microfibers for Organic Electronics

A scalable and green approach to manufacture semiconducting microfibers from polymer melts has been demonstrated. The polymer chains are highly aligned along the microfiber's long axis direction and exhibit highly anisotropic optical properties. In addition, the polymer microfibers show good flexibility and stretchability with a yield point around 10% under a reversible stress and can be stretched up to 180% without breaking. These features are desired for future flexible, stretchable, and conformable electronics. The origin of this stretchability is studied with diketopyrrolopyrrole derivatives using different conjugation break spacers and side chains. In addition, stretchable conducting microfibers can be obtained by doping with FeCl₃, which are further evaluated as organic conductors and source/drain electrodes in organic field‐effect transistors.     

Remarkable Suppression of Vibrational Relaxation in Organic Semiconducting Polymers by Introducing a Weak Electron Donor for Improved NIR-II Phototheranostics

Exploration of high-efficiency agents for near-infrared-II fluorescence imaging (NIR-II FI) promotes the development of NIR-II FI in life science. Despite the extensive use of organic semiconducting nanomaterials for NIR-II FI, the fluorescence efficiency is barely satisfying, and the molecular guideline to improve the imaging quality has not been clarified yet. This contribution designs self-brightened organic semiconducting polymers (OSPs) for improved NIR-II phototheranostics of cancer. The amplification of NIR-II brightness is realized by incorporating a weak electron-donating unit (5,5′-dibromo-4,4′-didodecyl-2,2′-bithiophene, DDB) into the semiconducting backbone with strong electron donor–acceptor alternated structure, which exhibits 6.3-fold and 25-fold fluorescence enhancement compared with the counterpart OSP at the same optical concentration and mass concentration, respectively. The broadband femtosecond transient absorption spectra experimentally elucidate the DDB doping-induced suppression of vibrational relaxation as the underlying reason for the NIR-II fluorescence amplification. Biocompatible nanoparticles fabricated from the optimal OSP₁₂ exhibit excellent NIR-II phototheranostic performance both in vitro and in vivo. Our research not only reveals the mechanistic insights for fluorescence enhancement of the designed OSPs from the essential view but also highlights an effective molecular methodology to guide the rational design of imaging agents with enhanced NIR-II brightness for improved phototheranostics in living subjects.     

Bio‐Erasable Intermolecular Donor–Acceptor Interaction of Organic Semiconducting Nanoprobes for Activatable NIR‐II Fluorescence Imaging

Activatable second near‐infrared window (NIR‐II; 1.0–1.7 µm) fluorescence probes that uncage deep‐tissue penetrating fluorescence by disease‐related biomarker stimuli hold great promise for detecting diseases with a poor understanding of the pathology at the molecular level with unprecedented resolution. However, currently, very few activatable NIR‐II fluorescence probes are reported mainly due to the lack of a simple yet general design strategy. Herein, a new and fairly generic design strategy using a bio‐erasable intermolecular donor–acceptor interaction to construct activatable NIR‐II fluorescence probes is reported. An organic semiconducting nanoprobe (SPNP) is constructed through blending a biomarker‐sensitive organic semiconducting non‐fullerene acceptor (3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐cyclopentane‐1,3‐dione‐[c]thiophen))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2',3'‐d']‐s‐indaceno[1,2‐b:5,6‐b'] dithiophene) (ITTC) (one of electric acceptors in organic solar cells) with a biomarker‐inert semiconducting polymer donor 5‐(4,8‐bis((2‐ethylhexyl)oxy)‐6‐methylbenzo[1,2‐b:4,5‐b']difuran‐2‐yl)‐10‐methylnaphtho[1,2‐c:5,6‐c']bis([1,2,5]thiadiazole) (PDF) in an amphiphilic‐polymer‐coated single nanoparticle to suppress NIR‐II fluorescence of the donor via a intermolecular donor–acceptor interaction. The acceptor ITTC is found to be specifically degraded by hypochlorite (an important biomarker) to erase its acceptor property, thus erasing the intermolecular donor–acceptor interaction and uncaging NIR‐II fluorescence. Consequently, SPNP exhibits a 17.5‐fold higher fluorescence brightness in the hypochlorite‐abnormal inflammation in vivo than in normal tissues. Our bio‐erasable intermolecular donor–acceptor interaction strategy provides simple yet general guidelines to design various biomarker‐activatable NIR‐II fluorescence probes.     

A Facile Strategy for Achieving Polymeric Afterglow Materials with Wide Color-Tunability and Persistent Near-Infrared Luminescence

Polymer-based room-temperature phosphorescence (RTP) materials show promising applications in anti-counterfeiting. To further realize multiscale and/or multimodal anti-counterfeiting, it is highly desirable to develop polymeric afterglow materials with multiple security features. Herein, a facile strategy is presented to endow polymeric afterglow materials with ultralong lifetime, wide color-tunability, persistent near-infrared (NIR) luminescence, and good water solubility via constructing non-traditional phosphorescence resonance energy transfer (PRET) and two-step sequential resonance energy transfer systems. Specifically, the 1-bromocarbazole derivatives with ultralong blue-color RTP property act as the energy donor while traditional dyes with red/NIR luminescence act as the energy acceptor. By simply regulating the doping composition and concentration of these non-traditional energy transfer systems, persistent and multicolor organic afterglow covering from the visible to NIR region is successfully realized. Notably, compared to the single-step PRET, the two-step sequential resonance energy transfer has the unique advantages of higher transfer efficiency of triplet excitons from the initial donor, a wider range of color-tunability mediated by the intermediary acceptor, and enhanced delayed fluorescence efficiency of the final acceptor. Finally, these water-soluble polymeric afterglow materials with ultralong lifetime, wide color-tunability, and persistent NIR luminescence show great potential applications in advanced anti-counterfeiting and information security technologies.     

Semiconducting Nanocomposite with AIEgen‐Triggered Enhanced Photoluminescence and Photodegradation for Dual‐Modality Tumor Imaging and Therapy

Semiconducting polymer nanoparticles (SPNs) have potential in biological applications. While some SPNs have significant photothermal conversion efficiencies (PCEs) as photothermal and photoacoustic agents, other SPNs offer high fluorescence yields as photoluminescent agents. However, the energy balance distribution in SPNs inhibits their successful applications in photoluminescence/photoacoustic (PL/PA) dual‐modality imaging. Additionally, the ultrastability of SPNs in vivo may cause damage to organisms. This work reports nanocomposite semiconducting polymer and tetraphenylethene nanoparticles (STNPs) constructed by semiconducting polymers (SPs) and tetraphenylethene aggregation‐induced emission luminogens (TPE AIEgens). The SP SPC10 endows good photothermal conversion ability, and the AIEgen TPBM supports enhanced photoluminescence of the STNPs. The results show that the STNPs can act as PL/PA dual‐modality imaging agents. The signal‐to‐noise (S/N) ratio in the PL modality reaches 8.7, and the imaging depth in the PA modality is 5.8 mm. The SPC10 in the STNPs can be decomposed under 90 mW cm^?2 white light irradiation in 6 h without any other additional agents. Furthermore, the STNPs are sufficient for the treatment of xenograft 4T1 tumor‐bearing mice based on photothermal therapy. The nanocomposite STNPs achieve optimized dual‐modality PL/PA imaging and the AIEgen‐triggered in situ photodegradation of SPNs. These properties indicate the significant potential of STNPs in clinical diagnosis and noninvasive therapy.     

An NIR‐II Fluorescence/Dual Bioluminescence Multiplexed Imaging for In Vivo Visualizing the Location,Survival, and Differentiation of Transplanted Stem Cells

The in vivo distribution, viability, and differentiation capability of transplanted stem cells are vital for the therapeutic efficacy of stem cell–based therapy. Herein, an NIR‐II fluorescence/dual bioluminescence multiplexed imaging method covering the visible and the second near‐infrared window from 400 to 1700 nm is successfully developed for in vivo monitoring the location, survival, and osteogenic differentiation of transplanted human mesenchymal stem cells (hMSCs) in a calvarial defect mouse model. The exogenous Ag₂S quantum dot–based fluorescence imaging in the second near‐infrared window is applied for visualizing the long‐term biodistribution of transplanted hMSCs. Endogenous red firefly luciferase (RFLuc)‐based bioluminescence imaging (BLI) and the collagen type 1 promoter–driven Gaussia luciferase (GLuc)‐based BLI are employed to report the survival and osteogenic differentiation statuses of the transplanted hMSCs. Meanwhile, by integrating the three imaging channels, multiple dynamic biological behaviors of transplanted hMSCs and the promotion effects of immunosuppression and the bone morphogenetic protein 2 on the survival and osteogenic differentiation of transplanted hMSCs are directly observed. The novel multiplexed imaging method can greatly expand the capability for multifunctional analysis of the fates and therapeutic capabilities of the transplanted stem cells, and aid in the improvement of stem cell–based regeneration therapies and their clinical translation.     

Ultrasmall Semiconducting Polymer Dots with Rapid Clearance for Second Near‐Infrared Photoacoustic Imaging and Photothermal Cancer Therapy

Phototheranostic agents in the second near‐infrared (NIR‐II) window (1000–1700 nm) are emerging as a promising theranostic platform for precision medicine due to enhanced penetration depth and minimized tissue exposure. The development of metabolizable NIR‐II nanoagents for imaging‐guided therapy are essential for noninvasive disease diagnosis and precise ablation of tumors. Herein, metabolizable highly absorbing NIR‐II conjugated polymer dots (Pdots) are reported for the first time for photoacoustic imaging guided photothermal therapy (PTT). The unique design of low‐bandgap D‐A π‐conjugated polymer (DPP‐BTzTD) together with modified nanoreprecipitation conditions allows to fabricate NIR‐II absorbing Pdots with ultrasmall (4 nm) particle size. Extensive experimental tests demonstrate that the constructed Pdots exhibit good biocompatibility, excellent photostability, bright photoacoustic signals, and high photothermal conversion efficiency (53%). In addition, upon tail‐vein intravenous injection of tumor‐bearing mice, Pdots also show high‐efficient tumor ablation capability with rapid excretion from the body. In particular, both in vitro and in vivo assays indicate that the Pdots possess remarkable PTT performance under irradiation with a 1064 nm laser with 0.5 W cm^?2, which is much lower than its maximum permissible exposure limit of 1 W cm^?2. This pilot study thus paves a novel avenue for the development of organic semiconducting nanoagents for future clinical translation.     

A Multiresponsive Metal–Organic Framework: Direct Chemiluminescence,Photoluminescence, and Dual Tunable Sensing Applications

By incorporating an anthracene moiety into a framework, a multiresponsive luminescent metal–organic framework ( 1 ) has been synthesized, which exhibits both direct chemiluminescence (CL) and dual tunable photoluminescence. By utilizing the CL, 1 has been explored as a selective visual sensor for hydrogen peroxide. Moreover, 1 also exhibits tunable fluorescence response toward different analytes. For electron‐rich aromatics, “turn‐on” and “turn‐off” responses can be simply switched by varying the excitation wavelength. For nitroaromatics, 1 exhibits novel linear quantitative quenching response. Density functional theory (DFT) calculations and experiments have been carried out to study the unique fluorescence response. The multiple luminescence properties and dual tunable sensing response indicate that incorporating anthracene moieties into frameworks should be a promising strategy to develop unprecedented luminescent materials with remarkable sensing properties.     

Biocompatible D–A Semiconducting Polymer Nanoparticle with Light‐Harvesting Unit for Highly Effective Photoacoustic Imaging Guided Photothermal Therapy

The development of nanotheranostic agents that integrate diagnosis and therapy for effective personalized precision medicine has obtained tremendous attention in the past few decades. In this report, biocompatible electron donor–acceptor conjugated semiconducting polymer nanoparticles (PPor‐PEG NPs) with light‐harvesting unit is prepared and developed for highly effective photoacoustic imaging guided photothermal therapy. To the best of our knowledge, it is the first time that the concept of light‐harvesting unit is exploited for enhancing the photoacoustic signal and photothermal energy conversion in polymer‐based theranostic agent. Combined with additional merits including donor–acceptor pair to favor electron transfer and fluorescence quenching effect after NP formation, the photothermal conversion efficiency of the PPor‐PEG NPs is determined to be 62.3%, which is the highest value among reported polymer NPs. Moreover, the as‐prepared PPor‐PEG NP not only exhibits a remarkable cell‐killing ability but also achieves 100% tumor elimination, demonstrating its excellent photothermal therapeutic efficacy. Finally, the as‐prepared water‐dispersible PPor‐PEG NPs show good biocompatibility and biosafety, making them a promising candidate for future clinical applications in cancer theranostics.     

Significant Enhancement of Photothermal and Photoacoustic Efficiencies for Semiconducting Polymer Nanoparticles through Simply Molecular Engineering

Semiconducting polymer nanoparticles (SP NPs) are employed as efficient nanoagents for “all‐in‐one” theranostic nanoplatforms with dual photoacoustic imaging (PAI) and photothermal therapy (PTT) functions based on their photothermal conversion effect. However, the mechanisms of tuning the PTT efficiency are still elusive, though several SP NPs with high photothermal efficiency are reported. Herein, two donor–acceptor (D–A) SP NPs PTIGSVS and PIIGSVS with the same donor unit but different acceptor units are designed and synthesized. Through tuning the acceptor unit, PTIGSVS shows more planar backbone structure, stronger D–A strength, redshifted absorption, enhanced extinction efficient, weakened emission properties, and more efficient nonradiative decay in comparison to the polymeric analogue PIIGSVS . Thus, PTIGSVS NPs present much higher photothermal conversion efficiencies (74%) than PIIGSVS NPs (11%), resulting in significantly enhanced in vitro and in vivo PAI and PTT performance. This contribution demonstrates that PTIGSVS NPs are superior PA/PTT agents for effective cancer theranostic and shed light on understanding the relationship between molecular structures and photothermal effect of CPs.     

Unadulterated Organic Nanoparticles with Small Sizes for Robust Tumor Imaging and Photothermal Treatment

Phototheranostics integrating optical imaging and phototherapy have attracted massive attention in the context of precise tumor therapy. However, most of the reported phototheranostic systems have large sizes and complex structures due to either the extraneous carriers or cargos. Herein, the organic nanoparticles (terrylenediimide (TDI) NPs) are obtained from a TDI-based single component in the absence of additives. The as-prepared TDI NPs possess favorable small sizes of less than 20 nm, good photothermal stability, and high photothermal conversion efficiency. Especially, TDI NPs have the capacity for rapid and lasting tumor imaging, and effective photothermal therapy of cervical cancer upon irradiation. This work provides an alternative method to prepare multifunctional nanomaterials with simple structures, and sheds light on the potential applications of dye molecules as intrinsic theranostic agents.     

Nanoscale Metal‐Organic Frameworks: Synthesis,Biocompatibility, Imaging Applications,and Thermal and Dynamic Therapy of Tumors

Nanoscale metal‐organic frameworks (NMOFs) have attracted increasing attention for biomedical applications due to their large specific surface area, good biocompatibility, adjustable structures, and diverse functions. By choosing appropriate metal ions and ligands, NMOFs can be synthesized and regulated to assist the diagnosis and treatment of cancer, acting as imaging agents, drug carriers, and cancer therapeutic agents. This review summarizes the recent advances of NMOFs in synthesis, biocompatibility, imaging, and applications in cancer therapies. Among these, the term “biocompatibility” is used to outline their various biological characteristics, and it is mainly discussed from the aspects of size and surface properties of NMOFs. The imaging section mainly emphasizes the application advantages of NMOFs as imaging agents in magnetic resonance, computed tomography, and fluorescence imaging. The applications of NMOFs in four cancer therapies, including phototherapy, radiotherapy, microwave therapy, and ultrasonic therapy, are addressed, especially for thermal and dynamic therapy. Finally, the prospects and challenges of NMOFs in imaging and cancer therapies are also discussed.     

All‐Organic,Temporally Pure White Afterglow in Amorphous Films Using Complementary Blue and Greenish‐Yellow Ultralong Room Temperature Phosphors

Organic molecules exhibiting afterglow emission (lifetime longer than 0.1 s) under ambient conditions have sparked tremendous attention in recent years as a sustainable energy source with potential applications in displays, lighting, and bioimaging. However, white afterglow organic materials with color purity during the entire period of delayed emission, after the cessation of excitation source, are yet to be achieved due to the different excited state lifetimes of its primary or complementary components. Herein, a remarkable, ambient “temporally pure white afterglow,” which lasts for over 7 s, by coorganizing complementary blue and greenish‐yellow organic room temperature phosphors with similar ultralong lifetimes and efficiency, in an amorphous polymer film is demonstrated. One of the most efficient blue afterglow room temperature phosphors is also reported, with an ultralong lifetime up to 2.26 s and maximum quantum efficiency of 36.8%, from purely organic triazatruxenes en route to the realization of this white afterglow. Further, broad and complementary absorption features of the coorganized phosphors in the visible region facilitates an excitation‐dependent dynamic color‐tuning of the afterglow from sky‐blue to greenish‐yellow.     

功能性近红外光谱脑成像噪声源及去噪方法综述

综述了功能性近红外光谱脑成像噪声源及去噪方法。从成像原理、噪声来源和发生机制等方面分析并给出了抑制噪声的方法和操作,详细分析了干扰的组成成分及特性,给出了有效去除方法和提高近红外光谱脑成像分析建模过程中的信号质量算法。这些方法能对近红外光谱脑成像数据的分析和处理提供指导。总结了3种会影响近红外光谱脑成像信号的噪声源：电气噪声、实验设计和操作误差、生理伪影,给出了2种实用去噪算法,并阐述了成像技术的发展趋势。     

Naturally and Elastically Bent Organic Polymorphs for Multifunctional Optical Applications

Recently, mechanically bendable organic single crystals have been widely studied as emerging flexible materials. However, only a very small percentage of organic crystals have been found to be elastic or plastic. In this study, crystal engineering is employed as a powerful strategy to improve the probability of constructing flexible organic crystals. Based on an organic compound, two polymorphs Cry‐ R and Cry‐ O with bright red and orange emissions, respectively, are obtained. Cry‐ R , being brittle inherently, can form a naturally bent crystal with an optical waveguide as efficient as the straight crystal. The other polymorph Cry‐ O can be elastically bent, almost into a loop, and displays an optical waveguide and amplified spontaneous emission in both the straight and bent state, demonstrating its multifunctional applications in flexible optical devices. In addition, the Y‐shaped crystals of Cry‐ O obtained by natural growth are found to transduce single emitted light through the two branches and thus generate dual output signals simultaneously, which further highlights the utility of “crystal flexibility”. The results not only suggest a guideline to modify the mechanical compliance by crystal engineering but also provide a model of flexible organic crystals for multifunctional optical applications.     

Achieving Color-Tunable and Time-Dependent Organic Long Persistent Luminescence via Phosphorescence Energy Transfer for Advanced Anti-Counterfeiting

Organic ultralong room-temperature phosphorescence (RTP) materials have promising applications in anti-counterfeiting. To improve the encryption level, the exploration of organic materials with tunable solid-state long persistent luminescence is in urgent need. Herein, a series of organic ultralong RTP polymeric systems are prepared by doping versatile indolocarbazole isomers into the poly(vinyl alcohol) (PVA) matrix. Notably, the doping film 11,12-ICz@PVA exhibits excellent RTP property with an ultralong lifetime of 2.04 s and a high phosphorescence quantum yield of 44.1%. Theoretical calculations reveal that this excellent RTP property can be attributed to the strong electrostatic attraction resulting from the synergistic double hydrogen-bond between the isomer 11,12-ICz and PVA matrix. More impressively, color-tunable and time-dependent long persistent luminescence is successfully achieved through efficient phosphorescence energy transfer between the indolocarbazole isomers with ultralong blue RTP emissions and commercially available fluorescent dyes with emission colors ranging from green to red doped into the PVA matrix. Besides, diversified encryption patterns are fabricated to demonstrate the promising applications of these water-soluble doping PVA systems with tunable solid-state persistent luminescence in advanced anti-counterfeiting technology.     

数字太阳敏感器成像建模与仿真

为了仿真太阳光的成像情况,基于标量衍射理论、辐射度学建立了包括光学系统模型和光电转换模型在内的完整的数字太阳敏感器成像模型。该模型适用于视场范围内任意角度入射的太阳光。同时,该模型所包含的从太阳辐射到成像面上像元灰度的能量转换体系完整准确。将太阳辐射作为模型输入进行了数值仿真,并与基于太阳模拟器的地面实验结果进行了对比分析。结果表明,该成像模型能比较准确地模拟太阳光的成像情况。该研究为后续的基于太阳敏感器的太阳光和杂散光成像仿真和对比研究提供了基础。