Novel multifunctional NIR-II aggregation-induced emission nanoparticles-assisted intraoperative identification and elimination of residual tumor

The Current Status and Future Directions on Nanoparticles for Tumor Molecular Imaging

Molecular imaging is an advanced technology that utilizes specific probes or markers in conjunction with cutting-edge imaging techniques to observe and analyze the localization, distribution, activity, and interactions of biomolecules within living organisms. Tumor molecular imaging, by enabling the visualization and quantification of molecular characteristics of tumor cells, facilitates a deeper and more comprehensive understanding of tumors, providing valuable insights for early diagnosis, treatment monitoring, and cancer biology research. However, the image quality of molecular imaging still requires improvement, and nanotechnology has significantly propelled the advancement of molecular imaging. Currently, nanoparticle-based tumor molecular imaging technologies encompass radionuclide imaging, fluorescence imaging, magnetic resonance imaging, ultrasound imaging, photoacoustic imaging, and multimodal imaging, among others. As our understanding of the tumor microenvironment deepens, the design of nanoparticle probes for tumor molecular imaging has also evolved, offering new perspectives and expanding the applications of tumor molecular imaging. Beyond diagnostics, there is a marked trend towards integrated diagnosis and therapy, with image-guided treatment playing a pivotal role. This includes image-guided surgery, photodynamic therapy, and chemodynamic therapy. Despite continuous advancements and innovative developments in molecular imaging, many of these remain in the experimental stage and require breakthroughs before they can be fully integrated into clinical practice.

NIR-II light in clinical oncology: opportunities and challenges

Novel strategies utilizing light in the second near-infrared region (NIR-II; 900-1,880 nm wavelengths) offer the potential to visualize and treat solid tumours with enhanced precision. Over the past few decades, numerous techniques leveraging NIR-II light have been developed with the aim of precisely eliminating tumours while maximally preserving organ function. During cancer surgery, NIR-II optical imaging enables the visualization of clinically occult lesions and surrounding vital structures with increased sensitivity and resolution, thereby enhancing surgical quality and improving patient prognosis. Furthermore, the use of NIR-II light promises to improve cancer phototherapy by enabling the selective delivery of increased therapeutic energy to tissues at greater depths. Initial clinical studies of NIR-II-based imaging and phototherapy have indicated impressive potential to decrease cancer recurrence, reduce complications and prolong survival. Despite the encouraging results achieved, clinical translation of innovative NIR-II techniques remains challenging and inefficient; multidisciplinary cooperation is necessary to bridge the gap between preclinical research and clinical practice, and thus accelerate the translation of technical advances into clinical benefits. In this Review, we summarize the available clinical data on NIR-II-based imaging and phototherapy, demonstrating the feasibility and utility of integrating these technologies into the treatment of cancer. We also introduce emerging NIR-II-based approaches with substantial potential to further enhance patient outcomes, while also highlighting the challenges associated with imminent clinical studies of these modalities.

A mitochondrion-targeted cyanine agent for NIR-II fluorescence-guided surgery combined with intraoperative photothermal therapy to reduce prostate cancer recurrence

Poorly identified tumor boundaries and nontargeted therapies lead to the high recurrence rates and poor quality of life of prostate cancer patients. Near-infrared-II (NIR-II) fluorescence imaging provides certain advantages, including high resolution and the sensitive detection of tumor boundaries. Herein, a cyanine agent (CY7-4) with significantly greater tumor affinity and blood circulation time than indocyanine green was screened. By binding albumin, the absorbance of CY7-4 in an aqueous solution showed no effects from aggregation, with a peak absorbance at 830 nm and a strong fluorescence emission tail beyond 1000 nm. Due to its extended circulation time (half-life of 2.5 h) and high affinity for tumor cells, this fluorophore was used for primary and metastatic tumor diagnosis and continuous monitoring. Moreover, a high tumor signal-to-noise ratio (up to ~ 10) and excellent preferential mitochondrial accumulation ensured the efficacy of this molecule for photothermal therapy. Therefore, we integrated NIR-II fluorescence-guided surgery and intraoperative photothermal therapy to overcome the shortcomings of a single treatment modality. A significant reduction in recurrence and an improved survival rate were observed, indicating that the concept of intraoperative combination therapy has potential for the precise clinical treatment of prostate cancer.

Comparative Study of Indocyanine Green Fluorescence Imaging in Lung Cancer with Near-Infrared-I/II Windows

BACKGROUND

We compare the application of intravenous indocyanine green (ICG) fluorescence imaging in lung cancer with near-infrared-I (NIR-I) and near-infrared-II (NIR-II) windows.

METHODS

From March to December 2022, we enrolled patients who received an intravenous injection of ICG (5 mg/kg) 1 day before the planned lung cancer surgery. The lung cancer nodules were imaged by NIR-I/II fluorescence imaging systems, and the tumor-to-normal-tissue ratio (TNR) was calculated. In addition, the fluorescence intensity and signal-to-background ratio (SBR) of capillary glass tubes containing ICG covered with different thicknesses of lung tissue were measured by NIR-I/II fluorescence imaging systems.

RESULTS

In this study, 102 patients were enrolled, and the mean age was 59.9 ± 9.2 years. A total of 96 (94.1%) and 98 (96.1%) lung nodules were successfully imaged with NIR-I and NIR-II fluorescence, and the TNR of NIR-II was significantly higher than that of NIR-I (3.9 ± 1.3 versus 2.4 ± 0.6, P < 0.001). In multiple linear regression, solid nodules (P < 0.001) and squamous cell carcinoma (P < 0.001) were independent predictors of a higher TNR of NIR-I/II. When capillary glass tubes were covered with lung tissue whose thickness was more than 2 mm, the fluorescence intensity and the SBR of NIR-II were significantly higher than those of NIR-I.

CONCLUSIONS

We verified the feasibility of NIR-II fluorescence imaging in intravenous ICG lung cancer imaging for the first time. NIR-II fluorescence can improve the TNR and penetration depth of lung cancer with promising clinical prospects.

Fluorescence visualization for cancer DETECTION: EXPERIENCE and perspectives

The current review focuses on the latest advances in the improvement and application of fluorescence imaging technology. Near-infrared (NIR) fluorescence imaging is a promising new technique that uses non-specific fluorescent agents and targeted fluorescent tracers combined with a dedicated camera to better navigate and visualize tumors. Fluorescence-guided surgery (FGS) is used to perform various tasks, helping the surgeon to distinguish lymphatic vessels and nodes from surrounding tissues easily and quickly assess the perfusion of the planned resection area, including intraoperative visualization of metastases. The results of the insertion of fluorescence visualization as an auxiliary method to cancer detection and high-risk metastatic lesions in clinical practice have demonstrated enthusiastic results and huge potential. However, intraoperative fluorescence visualization must not be considered as a main diagnostic or treatment method but as an aid to the surgeon. Thus, fluorescence study does not dispense the diagnostic gold standards of benign or malignant tumors (conventional examination, biopsy, ultrasonography and computed tomography, etc.) and can be done usually during intraoperative treatment. Moreover, as fluorescence surgery and fluorescence diagnostic techniques continue to improve, it is likely that they will evolve towards targeted fluorescence imaging probes that will increasingly target a specific type of cancer cell. The most important point remains the search for highly selective messengers of fluorescent labels, which make it possible to identify tumor cells exclusively in the affected organs and indicate to surgeons the boundaries of their spread and metastasis.

High-precision detection and navigation surgery of colorectal cancer micrometastases

Surgical resection is an effective treatment for colorectal cancer (CRC) patients, whereas occult metastases hinder the curative effect. Currently, there is no effective method to achieve intraoperatively diagnosis of tumor-positive lymph nodes (LNs). Herein, we adopt a near-infrared-II (NIR-II) organic donor-pi-acceptor-pi-donor probe FE-2PEG, which exhibits bright fluorescence over 1100 nm, excellent photostability, blood circulation time, and biocompatibility, to achieve high-performance bioimaging with improved temporal and spatial resolution. Importantly, the FE-2PEG shows efficient passive enrichment in orthotopic CRC, metastatic mesenteric LNs, and peritoneal metastases by enhanced permeability and retention effect. Under NIR-II fluorescence-guided surgery (FGS), the peritoneal micrometastases were resected with a sensitivity of 94.51%, specificity of 86.59%, positive predictive value (PPV) of 96.57%, and negative predictive value of 79.78%. The PPV still achieves 96.07% even for micrometastases less than 3 mm. Pathological staining and NIR-II microscopy imaging proved that FE-2PEG could successfully delineate the boundary between the tumor and normal tissues. Dual-color NIR-II imaging strategy with FE-2PEG (1100 ~ 1300 nm) and PbS@CdS quantum dots (> 1500 nm) successfully protects both blood supply and normal tissues during surgery. The NIR-II-based FGS provides a promising prospect for precise intraoperative diagnosis and minimally invasive surgery of CRC.

Protein@Cyanine-Based NIR-II Lymphography Enables the Supersensitive Visualization of Lymphedema and Tumor Lymphatic Metastasis

Visualization of the lymphatic system is clinically indispensable for the diagnosis and/or treatment of lymphatic diseases. Although indocyanine green (ICG) lymphography becomes an alternate imaging modality compared to traditional lymphoscintigraphy, it is still far from ideal due to the insufficient detection depth and low spatiotemporal resolution. Herein, protein@cyanine probes are rationally developed to solve the limitations of the current near-infrared-I (NIR-I) lymphography. The protein@cyanine probes are synthesized following a chlorine-containing dye-labeling strategy based on structure-selectivity (facile covalent binding between the dye and protein with a 1:1 molar ratio). As expected, the probes display exceptional NIR-II imaging ability with much-improved imaging contrast/resolution and controllable pharmacokinetics, superior to the clinical ICG. The protein@cyanine probes locate lymph nodes and delineate lymphatic vessels with super-high sensitivity and signal-to-background ratio, enabling real-time diagnosing lymphatic diseases such as lymphedema and tumor lymphatic metastasis. In particular, the NIR-II lymphography provides an opportunity to discover the disparate morbidity rate of primary lymphedema in different types of mice. Given the fact of lacking clinically transferable NIR-II probes, this work not only provides a promising strategy for enriching of the current library of NIR-II probes, but also promotes the clinical translation of NIR-II lymphography technology.

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.

Non-invasive molecular imaging for precision diagnosis of metastatic lymph nodes: opportunities from preclinical to clinical applications

Lymph node metastasis is an indicator of the invasiveness and aggressiveness of cancer. It is a vital prognostic factor in clinical staging of the disease and therapeutic decision-making. Patients with positive metastatic lymph nodes are likely to develop recurrent disease, distant metastasis, and succumb to death in the coming few years. Lymph node dissection and histological analysis are needed to detect whether regional lymph nodes have been infiltrated by cancer cells and determine the likely outcome of treatment and the patient's chances of survival. However, these procedures are invasive, and tissue biopsies are prone to sampling error. In recent years, advanced molecular imaging with novel imaging probes has provided new technologies that are contributing to comprehensive management of cancer, including non-invasive investigation of lymphatic drainage from tumors, identifying metastatic lymph nodes, and guiding surgeons to operate efficiently in patients with complex lesions. In this review, first, we outline the current status of different molecular imaging modalities applied for lymph node metastasis management. Second, we summarize the multi-functional imaging probes applied with the different imaging modalities as well as applications of cancer lymph node metastasis from preclinical studies to clinical translations. Third, we describe the limitations that must be considered in the field of molecular imaging for improved detection of lymph node metastasis. Finally, we propose future directions for molecular imaging technology that will allow more personalized treatment plans for patients with lymph node metastasis.

NIR-II fluorescence imaging-guided colorectal cancer surgery targeting CEACAM5 by a nanobody

BACKGROUND

Surgery is the cornerstone of colorectal cancer (CRC) treatment, yet complete removal of the tumour remains a challenge. The second near-infrared window (NIR-II, 1000-1700 nm) fluorescent molecular imaging is a novel technique, which has broad application prospects in tumour surgical navigation. We aimed to evaluate the ability of CEACAM5-targeted probe for CRC recognition and the value of NIR-II imaging-guided CRC resection.

METHODS

We constructed the probe 2D5-IRDye800CW by conjugated anti-CEACAM5 nanobody (2D5) with near-infrared fluorescent dye IRDye800CW. The performance and benefits of 2D5-IRDye800CW at NIR-II were confirmed by imaging experiments in mouse vascular and capillary phantom. Then mouse colorectal cancer subcutaneous tumour model (n = 15), orthotopic model (n = 15), and peritoneal metastasis model (n = 10) were constructed to investigate biodistribution of probe and imaging differences between NIR-I and NIR-II in vivo, and then tumour resection was guided by NIR-II fluorescence. Fresh human colorectal cancer specimens were incubated with 2D5-IRDye800CW to verify its specific targeting ability.

FINDINGS

2D5-IRDye800CW had an NIR-II fluorescence signal extending to 1600 nm and bound specifically to CEACAM5 with an affinity of 2.29 nM. In vivo imaging, 2D5-IRDye800CW accumulated rapidly in tumour (15 min) and could specifically identify orthotopic colorectal cancer and peritoneal metastases. All tumours were resected under NIR-II fluorescence guidance, even smaller than 2 mm tumours were detected, and NIR-II had a higher tumour-to-background ratio than NIR-I (2.55 ± 0.38, 1.94 ± 0.20, respectively). 2D5-IRDye800CW could precisely identify CEACAM5-positive human colorectal cancer tissue.

INTERPRETATION

2D5-IRDye800CW combined with NIR-II fluorescence has translational potential as an aid to improve R0 surgery of colorectal cancer.

FUNDINGS

This study was supported by Beijing Natural Science Foundation (JQ19027), the National Key Research and Development Program of China (2017YFA0205200), National Natural Science Foundation of China (NSFC) (61971442, 62027901, 81930053, 92059207, 81227901, 82102236), Beijing Natural Science Foundation (L222054), CAS Youth Interdisciplinary Team (JCTD-2021-08), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA16021200), the Zhuhai High-level Health Personnel Team Project (Zhuhai HLHPTP201703), the Fundamental Research Funds for the Central Universities (JKF-YG-22-B005) and Capital Clinical Characteristic Application Research (Z181100001718178). The authors would like to acknowledge the instrumental and technical support of the multi-modal biomedical imaging experimental platform, Institute of Automation, Chinese Academy of Sciences.

Incorporation of Robust NIR-II Fluorescence Brightness and Photothermal Performance in a Single Large π-Conjugated Molecule for Phototheranostics

Second near-infrared (NIR-II, 1000-1700 nm) window fluorescence imaging-guided photothermal therapy probes are promising for precise cancer phototheranostics. However, most of the currently reported probes do not demonstrate high NIR-II fluorescent brightness (molar absorption coefficient (ε) × quantum yield (QY)) and photothermal performance (ε × photothermal conversion efficiency (PCE)) in a single molecule. Herein, a versatile strategy to solve this challenge is reported by fabricating a large π-conjugated molecule (BNDI-Me) with a rigid molecular skeleton and flexible side groups. The proposed BNDI-Me nanoprobe boosts the ε and simultaneously optimizes its QY and PCE. Therefore, high NIR-II fluorescent brightness (ε × QY = 2296 m^-1 cm^-1 ) and strong photothermal performance (ε × PCE = 82 000) are successfully incorporated in a single small molecule, and, to the best of knowledge, either of these two parameters is better than the best currently available fluorescent or photothermal probes. Thus, superior NIR-II imaging effect in vivo and high photothermal tumor inhibition rate (81.2%) at low systemic injection doses are obtained. The work provides further insights into the relationship of photophysical mechanisms and structures, and presents promising molecular design guidelines for the integration of more efficient multiple theranostic functions in a single molecule.

Full-Color-Tunable Nanohydrogels as High-Stability Intracellular Nanothermometers

Full-color-tunable hydrogels with ultrahigh stability can be used in various fields, including intracellular temperature sensing. However, constructing full-color-tunable organic nanohydrogels with excellent biocompatibility and stability for intracellular temperature sensing remains a great challenge. Here, we report a full-color-tunable nanohydrogel with ultrahigh stability as an intracellular nanothermometer. Three types of temperature-sensitive polymers with red, green, and blue fluorescence were synthesized. Through easy mixing of these three polymers with regulation of the mass ratio, these polymers can be encoded to full-color-tunable fluorescent nanohydrogels, including nanohydrogels with white-light emission (NWLEs), with sizes of about 200 nm in aqueous media. Further study suggested that the as-obtained NWLEs exhibited good performance in intracellular temperature sensing because of their ultrahigh stability on their fluorescence properties and morphologies.