Recent Advances of Organic Near-Infrared II Fluorophores in Optical Properties and Imaging Functions

Rationally manipulating molecular planarity to improve molar absorptivity, NIR-II brightness, and photothermal effect for tumor phototheranostics

The secondary near-infrared region (NIR-II) fluorescence imaging-guided photothermal therapy (PTT) offers a noninvasive and light-controllable treatment option for deep-seated cancers. However, the development of NIR-II photothermal agents (NIR-II PTAs) that possess the desired properties of high molar absorption coefficient (ε), fluorescence quantum yield (QY), and photothermal conversion efficiency (PCE) remain a challenge due to the contradiction between radiative and nonradiative processes. Herein, we propose a novel side-chain heteroatom substitution engineering strategy to simultaneously enhance ε, QY, and PCE by modifying the molecular planarity. Remarkably, by increasing the number of oxygen atoms in the alkyl chains from DTIC, DO1TIC, to DO2TIC, the D-A interaction was enhanced and the molecular planarity was optimized. Theoretical calculations indicated that DO2TIC has a smaller energy gap and closer packing, which may lead to effective regulation of radiative and nonradiative transition processes. Notably, we achieved the excellent ε value of 2.61 × 105 M-1 cm-1 for the NIR-II PTA from DO2TIC, which is attributed to the enhanced molecular planarity. This value surpasses that of most previously developed NIR-II PTAs, resulting in boosted QY and PCE in its nanoparticle state. With these advantages, DO2TIC NPs demonstrated high signal-to-background ratio (SBR = 13.50) imaging of the vascular system and NIR-II imaging-guided PTT for effective tumor elimination using a 1064 nm laser. This study provides a new perspective for developing versatile NIR-II excited phototheranostic systems, enabling potent bioimaging and cancer therapy.

Shedding light on imaging cancer research: Design and synthesis of 1, 8-naphthalimide-based PRMT5-targeted fluorescent ligands

Protein Arginine Methyltransferase 5 (PRMT5) is an important player in breast cancer cell activity, and innovative fluorescent ligands targeting this enzyme offer revolutionary, real-time insights into its role in cancer progression, unlocking new avenues for diagnosis and treatment. This study introduces fluorescence-labeled PRMT5 ligands, highlighting their applications in visualizing PRMT5, monitoring enzymatic activity as well as studying toxicity. Herein, we describe the design, synthesis, and cellular imaging of a series of fluorescent ligands that target PRMT5. These ligands are based on the introduction of strong and selective PRMT5 inhibitors into various fluorophores using varied linkers. Among them, compound 7 at 10 μM was shown to exhibit strong fluorescence signals against MCF-7 cells with IC50 values of 29 nM. These advancements could significantly impact tumor treatment due to their ability to specify the target and visualize PRMT5 activity in real time, particularly in breast cancer research.

Rational Design and Biological Application of Hybrid Fluorophores

Fluorophores are considered powerful tools for not only enabling the visualization of cell structures, substructures, and biological processes, but also making for the quantitative and qualitative measurement of various analytes in living systems. However, most fluorophores do not meet the diverse requirements for biological applications in terms of their photophysical and biological properties. Hybridization is an important strategy in molecular engineering that provides fluorophores with complementarity and multifunctionality. This review summarizes the basic strategies of hybridization with four classes of fluorophores, including xanthene, cyanine, coumarin, and BODIPY with a focus on their structure-property relationship (SPR) and biological applications. This review aims to provide rational hybrid ideas for expanding the reservoir of knowledge regarding fluorophores and promoting the development of newly produced fluorophores for applications in the field of life sciences.

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.

Remodeling the hepatic fibrotic microenvironment with emerging nanotherapeutics: a comprehensive review

Liver fibrosis could be the last hope for treating liver cancer and remodeling of the hepatic microenvironment has emerged as a strategy to promote the ablation of liver fibrosis. In recent years, especially with the rapid development of nanomedicine, hepatic microenvironment therapy has been widely researched in studies concerning liver cancer and fibrosis. In this comprehensive review, we summarized recent advances in nano therapy-based remodeling of the hepatic microenvironment. Firstly, we discussed novel strategies for regulatory immune suppression caused by capillarization of liver sinusoidal endothelial cells (LSECs) and macrophage polarization. Furthermore, metabolic reprogramming and extracellular matrix (ECM) deposition are caused by the activation of hepatic stellate cells (HSCs). In addition, recent advances in ROS, hypoxia, and impaired vascular remodeling in the hepatic fibrotic microenvironment due to ECM deposition have also been summarized. Finally, emerging nanotherapeutic approaches based on correlated signals were discussed in this review. We have proposed novel strategies such as engineered nanotherapeutics targeting antigen-presenting cells (APCs) or direct targeting T cells in liver fibrotic immunotherapy to be used in preventing liver fibrosis. In summary, this comprehensive review illustrated the opportunities in drug targeting and nanomedicine, and the current challenges to be addressed.

Rational Design of a Self-Assembling High Performance Organic Nanofluorophore for Intraoperative NIR-II Image-Guided Tumor Resection of Oral Cancer

The first line of treatment for most solid tumors is surgical resection of the primary tumor with adequate negative margins. Incomplete tumor resections with positive margins account for over 75% of local recurrences and the development of distant metastases. In cases of oral cavity squamous cell carcinoma (OSCC), the rate of successful tumor removal with adequate margins is just 50-75%. Advanced real-time imaging methods that improve the detection of tumor margins can help improve success rates,overall safety, and reduce the cost. Fluorescence imaging in the second near-infrared (NIR-II) window has the potential to revolutionize the field due to its high spatial resolution, low background signal, and deep tissue penetration properties, but NIR-II dyes with adequate in vivo performance and safety profiles are scarce. A novel NIR-II fluorophore, XW-03-66, with a fluorescence quantum yield (QY) of 6.0% in aqueous media is reported. XW-03-66 self-assembles into nanoparticles (≈80 nm) and has a systemic circulation half-life (t_1/2 ) of 11.3 h. In mouse models of human papillomavirus (HPV)+ and HPV- OSCC, XW-03-66 outperformed indocyanine green (ICG), a clinically available NIR dye, and enabled intraoperative NIR-II image-guided resection of the tumor and adjacent draining lymph node with negative margins. In vitro and in vivo toxicity assessments revealed minimal safety concerns for in vivo applications.

Transmissible H-aggregated NIR-II fluorophore to the tumor cell membrane for enhanced PTT and synergistic therapy of cancer

Photothermal therapy (PTT) combined with second near-infrared (NIR-II) fluorescence imaging (FI) has received increasing attention owing to its capacity for precise diagnosis and real-time monitoring of the therapeutic effects. It is of great clinical value to study organic small molecular fluorophores with both PTT and NIR-II FI functions. In this work, we report a skillfully fluorescent lipid nanosystem, the RR₉ (RGDRRRRRRRRRC) peptide-coated anionic liposome loaded with organic NIR-II fluorophore IR-1061 and chemotherapeutic drug carboplatin, which is named RRIALP-C4. According to the structural interaction between IR-1061 and phospholipid bilayer demonstrated by molecular dynamics simulations, IR-1061 is rationally designed to possess the H-aggregated state versus the free state, thus rendering RRIALP-C4 with the activated dual-channel integrated function of intravital NIR-II FI and NIR-I PTT. Functionalization of RRIALP-C4 with RR₉ peptide endows the specifically targeting capacity for α_vβ₃-overexpressed tumor cells and, more importantly, allows IR-1061 to transfer the H-aggregated state from liposomes to the tumor cell membrane through enhanced membrane fusion, thereby maintaining its PTT effect in tumor tissues. In vivo experiments demonstrate that RRIALP-C4 can effectively visualize tumor tissues and systemic blood vessels with a high sign-to-background ratio (SBR) to realize the synergistic treatment of thermochemotherapy by PTT synergistically with temperature-sensitive drug release. Therefore, the strategy of enhanced PTT through H-aggregation of NIR-II fluorophore in the tumor cell membrane has great potential for developing lipid nanosystems with integrated diagnosis and treatment function.

D-A Type NIR-II Organic Molecules: Strategies for the Enhancement Fluorescence Brightness and Applications in NIR-II Fluorescence Imaging-Navigated Photothermal Therapy

NIR-II fluorescence imaging (NIR-II FI) and photothermal therapy (PTT) have received broad attentions in precise tumor diagnosis and effective treatment attributed to high-resolution and deep tissue imaging, negligible invasivity, and high-efficiency treatment. Although many fluorescent molecules have been designed and conducted for NIR-II FI and PTT, it is still an enormous challenge for researchers to pioneer some rational design guidelines to improve fluorescence brightness. Organic D-A-type molecules, including small molecules and conjugated polymers, can be designed and developed to improve fluorescence brightness due to their tunable and easy functionalized chemical structures, allowing molecules tailored photophysical properties. In this review, some approaches to the development and design strategies of D-A type small molecules and conjugated polymers for the enhancement of fluorescence brightness are systemically introduced. Meanwhile, some applications of PTT and PTT-based combination therapy (such as PDT, chemotherapy, or gas therapy) assisted by NIR-II FI-based single or multiimaging technologies are classified and represented in detail as well. Finally, the current issues and challenges of NIR-II organic molecules in NIR-II FI-navigated PTT are summarized and discussed, which gives some guidelines for the future development direction of NIR-II organic molecules for NIR-II FI-navigated PTT.

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.

A Small-Molecule Based Organic Nanoparticle for Photothermal Therapy and Near-Infrared-IIb Imaging

Near-infrared window IIb (NIR-IIb, 1500-1700 nm) fluorescence imaging demonstrates attractive properties including low scattering, low absorption, and deep tissue penetration, and photothermal therapy (PTT) is also a promising modality for cancer treatment. However, until now, there is no report on theranostic systems based on small organic molecules combining fluorescence imaging in the NIR-IIb and PTT, highlighting the challenge and strong need for development of such agents. Herein, we report a novel small molecule NIR-IIb dye IT-TQF with a D-A-D structure, which exhibited high fluorescence intensity in the NIR-IIb window. To further translate IT-TQF into an effective theranostic agent, IT-TQF was encapsulated into DSPE-PEG₂₀₀₀ to construct IT-TQF NPs. The physical and photochemical properties of the nanoprobe were investigated in vitro, and the in vivo NIR-IIb imaging and PTT performance were evaluated in normal, subcutaneous, orthotopic, and metastatic tumor mice models. IT-TQF NP-based NIR-IIb imaging demonstrated high spatial resolution and high tissue penetration depth, and small normal blood vessels (55.3 μm) were successfully imaged in the NIR-IIb window. Subcutaneous, orthotopic, and metastatic tumors were all clearly delineated. A high tumor signal-to-background ratio (SBR) of 9.42 was achieved for orthotopic osteosarcoma models, and the erosions of bone tissue caused by tumor cells were precisely visualized. Moreover, NIR-II image-guided surgery was successfully performed to completely remove the orthotopic tumor. Importantly, IT-TQF NPs displayed high PTT efficacy (photothermal conversion efficiency: 47%) for effective treatment of tumor mice. In conclusion, IT-TQF NPs are a novel and promising phototheranostic agent in the NIR-IIb window, and the nanoprobe has high potential for a broad range of biomedical applications.

Organic fluorescent nanoprobes with NIR-IIb characteristics for deep learning

Illumination of biological events with near-infrared II sub-channel (NIR-IIb, 1500-1700 nm) enhances the transparency of biological tissues, which is very attractive for deep imaging. Due to the long-wavelength, which reduces optical damage, suppresses autofluorescence, and obviates light scattering, NIR-IIb nanoprobes afford deep tissue penetration with unprecedented spatiotemporal resolution. Hence, NIR-IIb imaging facilitates deep learning and decipherment of biological proceedings in living organisms with astounding high clarity. In comparison to its predecessors in the visible-near-infrared spectrum, imaging in the NIR-IIb has shown great potential for tissue imaging and extrapolating imaging applications for clinical studies. However, the use of organic fluorescent nanoprobes (OFNPs) in the NIR-IIb region is still rare since it is in its early stages. Thus, herein we aim to survey the recent development of different organic fluorescent nanomaterials with NIR-IIb characteristics, their unique photophysical properties, and their utilization in deep imaging in animal models. Further, practical researches on organic fluorescent nanoprobes with NIR-IIb emission and their transition to clinical applications are highlighted.

Near-Infrared Fluorescence Tumor-Targeted Imaging in Lung Cancer: A Systematic Review

Lung cancer is the most common cancer type worldwide, with non-small cell lung cancer (NSCLC) being the most common subtype. Non-disseminated NSCLC is mainly treated with surgical resection. The intraoperative detection of lung cancer can be challenging, since small and deeply located pulmonary nodules can be invisible under white light. Due to the increasing use of minimally invasive surgical techniques, tactile information is often reduced. Therefore, several intraoperative imaging techniques have been tested to localize pulmonary nodules, of which near-infrared (NIR) fluorescence is an emerging modality. In this systematic review, the available literature on fluorescence imaging of lung cancers is presented, which shows that NIR fluorescence-guided lung surgery has the potential to identify the tumor during surgery, detect additional lesions and prevent tumor-positive resection margins.

Two-Photon Nanoprobe for NIR-II Imaging of Tumour and Biosafety Evaluation

How to develop near-infrared second window (NIR-II, 1000-1700 nm) fluorescent nanoprobes with a uniform size, strong fluorescence signal and good biosafety owns great clinical requirement. Herein we reported that a two photon fluorescent nanoprobe was developed via encapsulating NIR-II-fluorescent molecules into DSPE-PEG, which was effectively endocytosized by cancer cells, and achieved strong NIR-II fluorescence imaging in cancer cells and cancer cell-beard mice models. Prepared NIR-II-fluorescent nanoprobe exhibited rapid metabolism and excellent biocompatibility. In conclusion, the prepared two photon nanoprobe owns good biosafety, and clinical translational prospect in NIR-II fluorescent imaging of tumour in vivo in near future.

Thiadiazoloquinoxaline derivatives-based NIR-II organic molecules for NIR-II fluorescence imaging and photothermal therapy

NIR-II FI have emerged as a promising imaging tool for in vivo precise diagnosis and visualization towards various diseases, ascribed to its merits of attenuated light scattering and tissue absorption...

Second near-infrared (NIR-II) imaging: a novel diagnostic technique for brain diseases

Imaging in the second near-infrared II (NIR-II) window, a kind of biomedical imaging technology with characteristics of high sensitivity, high resolution, and real-time imaging, is commonly used in the diagnosis of brain diseases. Compared with the conventional visible light (400-750 nm) and NIR-I (750-900 nm) imaging, the NIR-II has a longer wavelength of 1000-1700 nm. Notably, the superiorities of NIR-II can minimize the light scattering and autofluorescence of biological tissue with the depth of brain tissue penetration up to 7.4 mm. Herein, we summarized the main principles of NIR-II in animal models of traumatic brain injury, cerebrovascular visualization, brain tumor, inflammation, and stroke. Simultaneously, we encapsulated the in vivo process of NIR-II probes and their in vivo and in vitro toxic effects. We further dissected its limitations and following optimization measures.

Thienothiadiazole-Based NIR-II Dyes with D-A-D Structure for NIR-II Fluorescence Imaging Systems

Fluorescence imaging (FI) in the second near-infrared optical window (NIR-II, 1000-1700 nm) has received increasing focus due to its capacity of high spatiotemporal resolution, rapid real-time imaging, and deep penetration depth. In addition, D-A-D-based organic small molecules have also attracted wide attention due to their designed chemical structure and rapid renal metabolism. However, most of the fluorescent cores were based on benzobisthiadiazole (BBTD) and 6,7-diphenyl-[1,2,5]thiadiazolo[3,4-g]quinoxaline (TTQ). The design and development of fluorescent core still remain challenging. Therefore, two NIR-II dyes based on the acceptor 4,6-di(2-thienyl)thieno[3,4-c][1,2,5]thiadiazole (TTDT) were designed and developed with donors tributyl(5-(9,9-dioctyl-9H-fluoren-2-yl)thiophen-2-yl)stannane (TF) and (5-(9,9'-spirobi[fluoren]-2-yl)thiophen-2-yl)tributylstannane (TSF) by the Stille coupling reaction, respectively. Subsequently, the corresponding nanoparticles were prepared, and then TTDT-TF-based nanoparticles with superior photostability and strong NIR-II fluorescence signals were chosen for NIR-II FI. More importantly, the in vivo experiments suggested that TTDT-TF NPs exhibited significant accumulation at tumor sites and high signal-to-background ratio (SBR). The above results indicated that the two D-A-D-type fluorophores based on TTDT have potential for NIR-II FI with superior imaging quality and imaging-guided surgery or therapy.