Strong Near-infrared Fluorescence Research Articles

Biodegradable ICG-Conjugated Germanium Nanoparticles for In Vivo Near-Infrared Dual-Modality Imaging and Photothermal Therapy.

Theranostics, by integrating diagnosis and therapy on a single platform, enables real-time monitoring of tumors during treatment. To improve the accuracy of tumor diagnosis, the fluorescence and photoacoustic imaging modalities can complement each other to achieve high resolution and a deep penetration depth. Despite the superior performance, the biodegradability of theranostic agents plays a critical role in enhancing nanoparticle excretion and reducing chronic toxicity, which is essential for clinical applications. Herein, we synthesize biocompatible and biodegradable indocyanine green (ICG)-conjugated germanium nanoparticles (GeNPs) and investigate their biodistributions in nude mice and 4T1 tumor models after intravenous injections using near-infrared (NIR) dual-modality fluorescence and photoacoustic imaging. The ICG-conjugated GeNPs have strong NIR absorption due to the NIR-absorbing ICG and Ge in combination, emit strong NIR fluorescence due to the multilayered ICG coatings, and exhibit very low in vitro and in vivo toxicity. After tail vein injections, the ICG-conjugated GeNPs mainly accumulate in the liver and spleen as well as the tumor with the help of the enhanced permeability and retention effect. The tumor's fluorescence signal is much stronger than that of the control group injected with pure ICG solution, as the GeNPs can function as biodegradable carriers for efficiently delivering the ICG molecules to the tumor. Lastly, the ICG-conjugated GeNPs accumulated in the tumor can also be utilized for photothermal treatment under NIR laser irradiation, after which the tumor volume almost diminishes after 14 days. The experimental findings in this work demonstrate that the ICG-conjugated GeNPs are promising theranostic agents with exceptional biodegradability for in vivo NIR dual-modality imaging and photothermal therapy.

A cell membrane-targeted photosensitizer for cancer photodynamic therapy and dynamic ablation process tracking

Photodynamic therapy (PDT) uses photosensitizer (PS) to generate reactive oxygen species (ROS) under light to trigger cell apoptosis in cancer treatment. Organelle-targeted PS can effectively enhance the efficacy of phototherapy by specifically destroying subcellular organelles. The cell membrane, as an important organelle, is the “protective wall” of cells maintaining the integrity and normal life activities of cells. The damage to cell membranes is fatal to cells. However, utilizing functional PS to achieve cell membrane-targeted PDT, and realize real-time and accurate in situ reporting of cell membrane damage and monitoring of the treatment process, are challenging tasks. In this work, we prepared a photosensitizer (2TPAO) with aggregation-induced emission (AIE) characteristics, good water solubility, strong near-infrared fluorescence, and the capability for specific imaging of cell membranes. Moreover, 2TPAO could effectively produce ROS under visible light irradiation and achieve photodynamic ablation of tumor cells and tumors. Meanwhile, during PDT, the fluorescence changes of 2TPAO indicated the destruction of cell membranes, allowing intuitive determination of the phototherapy results. Therefore, 2TPAO is an effective cell membrane-targeted PS for cancer PDT.

Guest-Induced Helical Superstructure from a Gold Nanocluster-Based Supramolecular Organic Framework Enables Efficient Catalysis.

Mimicking hierarchical assembly in nature to exploit atomically precise artificial systems with complex structures and versatile functions remains a long-standing challenge. Herein, we report two single-crystal supramolecular organic frameworks (MSOF-4 and MSOF-5) based on custom-designed atomically precise gold nanoclusters Au11(4-Mpy)3(PPh3)7, showing distinct and intriguing host-guest adaptation behaviors toward 1-/2-bromopropane (BPR) isomers. MSOF-4 exhibits sev topology and cylindrical channels with 4-mercaptopyridine (4-Mpy) ligands matching well with guest 1-BPR. Due to the confinement effect, solid MSOF-4 undergoes significant structural change upon selective adsorption of 1-BPR vapor over 2-BPR, resulting in strong near-infrared fluorescence. Single-crystal X-ray diffraction reveals that Au11(4-Mpy)3(PPh3)7 in MSOF-4 transforms into Au11Br3(PPh3)7 upon ligand exchange with 1-BPR, resulting in 1-BPR@MSOF-6 single crystals with a rarely reported helical assembly structure. Significantly, the double-helical structure of MSOF-6 facilitates efficient catalysis of the electron transfer (ET) reaction, resulting in a nearly 6 times increase of catalytic rates compared with MSOF-4. In sharp contrast, solid MSOF-5 possesses chb topology and cage-type channels with narrow windows, showing excellent selective physical adsorption toward 1-BPR vapor but a nonfluorescent feature upon guest adsorption. Our results demonstrate a powerful strategy for developing advanced assemblies with high-order complexity and engineering their functions in atomic precision.

A dual-emission fluorescent probe with independent polarity and viscosity responses: The synthesis, spectroscopy and bio-imaging applications

Viscosity and polarity are essential parameters that play critical roles in various physiological processes. Thus, dual-emission fluorescent probes that respond to both polarity and viscosity are highly sought-after tools for studying these processes. In addressing this need, a novel fluorescent probe (L), with dual emissions centered at 460 nm and 780 nm, which can sensitively respond to polarity and viscosity respectively, has been developed. Probe (L) is constructed through rational molecular design, utilizing two conjugated synthons connected by a π-bond to form a D-π-A system. The twisted intramolecular charge transfer (TICT) state is dominant in low-viscosity environments, resulting in weak near-infrared (NIR) fluorescence. Conversely, the intramolecular charge transfer (ICT) state is expected to prevail in high-viscosity environments, leading to strong NIR fluorescence. The polarity-sensitive fluorescence centered at 460 nm can be attributed to the emission of the coumarin unit. Moreover, probe (L) exhibits low cytotoxicity and primarily targets mitochondria. By leveraging the dual-emission properties of probe (L), real-time imaging of polarity and viscosity fluctuations within cells has been achieved. Additionally, probe (L) can be used for in situ and in vivo imaging of rheumatoid arthritis (RA) with good imaging resolution.

Engineering a “turn-on” NIR fluorescent sensor-based hydroxyphenyl benzothiazole with a cinnamoyl unit for hydrazine and its environmental and in-vitro applications

Hydrazine (N2H4), a chemical compound widely used in various industrial applications, causes significant environmental and biological hazards. Therefore, it is crucial to develop methodologies for the visualization and real time tracking of N2H4. In this regard, we have constructed a novel near-infrared fluorescent probe (HBT-Cy) that can effectively detect N2H4 in various samples. HBT-Cy contains 2-(2′-hydroxyphenyl)benzothiazole (HBT), cinnamoyl (Cy), and pyridinium (Py) moieties. Importantly, HBT-Cy exhibits a rapid, selective, and highly sensitive response to N2H4. This response results in the release of HBT-Py and the generation of considerable colorimetric changes along with a significant NIR (near infrared) fluorescence signal, peaking at 685 nm. Advantages of this system include turn on NIR fluorescence with large Stokes shift, (approximately 171 nm), low limit of detection (LOD = 0.11 μM) and quantum yield (0.211). The probe with low cytotoxic behavior demonstrates strong NIR fluorescence imaging capabilities to visualize endogenous and exogenous N2H4 in live cells. This mitochondria-targetable probe shows effective subcellular localization. These results suggest that HBT-Cy is a valuable probe for tracking and investigating the behavior of N2H4 in biological systems and environmental samples.

Endogenous CO imaging in bacterial pneumonia with a NIR fluorescent probe

Bacterial pneumonia is a serious respiratory illness that poses a great threat to human life. Rapid and precise diagnosis of bacterial pneumonia is crucial for symptomatic clinical treatment. Endogenous carbon monoxide (CO) is regarded as a significant indicator of bacterial pneumonia; herein, we developed a near-infrared (NIR) probe for fluorescence and photoacoustic (PA) dual-mode imaging of endogenous CO in bacterial pneumonia. NO2-BODIPY could rapidly and specifically react with CO to produce strong NIR fluorescence as well as ratiometric PA signals. NO2-BODIPY has outstanding features including fast response, fluorescence/PA dual mode signals, good specificity, and a low limit of detection (LOD = 20.3 nM), which enables it to image endogenous CO in cells and bacterial pneumonia mice with high sensitivity and high contrast ratio. In particular, NO2-BODIPY has two-photon excited (1340 nm, σ1 = 1671 GM) NIR fluorescence and has been utilized to image endogenous CO in bacterial pneumonia mice with deep tissue penetration. NO2-BODIPY has been demonstrated a good capability of fluorescence/PA dual-mode imaging of CO in bacterial pneumonia mice, providing a precise manner to diagnose bacterial pneumonia.

Cancer immunotheranostics using bioactive nanocoated photosynthetic bacterial complexes

Developing new modalities that allow multidimensional therapy with optical and immunological regulations is a challenge ahead of pharmacology and drug discovery for effective cancer treatment. To this end, superior purple photosynthetic bacteria, which show unique near-infrared (NIR) fluorescence, strong photothermal conversion ability, and high biocompatibility, were screened from various bacterial strains. To improve the therapeutic performances of screened bacteria, we further designed and developed simple chemical bacterial membrane functionalization with bioactive molecules and polyethylene glycol derivatives. Exploring the physicochemical and physiological properties of the chemically functionalized bacteria complexes achieved excellent tumor targeting and strong anticancer efficacies. The highly biocompatible functional bacteria showed cytotoxic immunological effects, strong NIR fluorescence, and powerful photothermal conversion in the targeted tumor milieu under biologically penetrating NIR light irradiation.

A targeted phototheranostic agent with strong AIE effect and boosted type I ROS generation

Hypoxia and nonspecific killing always hinder the photodynamic therapy of malignant tumors and infectious diseases that both severely threatening human health. Herein, we report a type I photosensitizer (MTOTPy) with aggregation-induced near-infrared (NIR) emission feature and specific identification ability by rational molecular design. Enhanced electron-donating effect and electron-rich anion-π+ structure endow MTOTPy with strong NIR fluorescence and intensive type I reactive oxygen species generation in aggregation. It is demonstrated that MTOTPy can achieve fast identification of tumor cells by targeting mitochondria and specific recognition of Staphylococcus aureus (S. aureus) among other kinds of microbes. Moreover, MTOTPy can kill more than 90% tumor cells and S. aureus upon visible light irradiation at low concentration of 5.0 μM and 0.5 μM, respectively. The work provides a feasible idea for designing photosensitizers to overcome the hypoxic limitation of photodynamic therapy and advance the development of image-guided therapy with high efficiency.

Evaluation of the Utilization of Near-Infrared Fluorescent Contrast Agent ASP5354 for In Vivo Ureteral Identification in Renal Diseases Using Rat Models of Gentamicin-Induced Acute Kidney Injury.

ASP5354 was recently developed as a near-infrared fluorescence (NIRF) contrast agent for intraoperative ureteral identification, and its use has been evaluated in healthy animals. However, the utilization of ASP5354 for ureteral identification has not been evaluated in animals with renal injury. In this study, we assessed the application of ASP5354 for ureteral imaging using rat models of gentamicin-induced mild, moderate, and severe acute kidney injury (AKI), using a clinically available NIRF detection system. NIRF was detected in the abdominal cavity and ureters after laparotomy, and the efficiency of ASP5354 was evaluated based on the NIRF signal intensity over 60 min. After the intravenous injection of ASP5354 into rats with mild or moderate AKI, the ureters were clearly imaged at a high ratio of NIRF intensity in the ureter to that in the tissues around the ureter. Six days after intravenous injection, the use of ASP5354 in rats with moderate AKI did not affect the biochemical kidney functions or histopathological conditions of the kidney tissues, as compared to those with no injection of ASP5354. In rats with severe AKI, ureteral imaging was not effective due to the relatively strong NIRF expression in the tissues around the ureters. These data indicate that ASP5354 holds potential as a contrast agent for intraoperative ureteral identification in patients with limited renal injury.

Monitoring the fluctuations of cysteine activity in living cells using a near-infrared fluorescence probe

Cysteine (Cys) is one of the most common cellular biothiols and is closely implicated in numerous diseases such as edema, psoriasis, Parkinson's disease, and liver damage. Therefore, detecting Cys activity in complex living organisms is highly necessary for diagnosing related diseases. This study synthesized a near-infrared (NIR) Cys-special probe (MCyA) by introducing an acrylate group to the MCyOH fluorophore. Consequently, Cys could precisely and quickly “light up” strong NIR fluorescence (711 nm) by transforming MCyA into MCyOH. Additionally, MCyA was applied to systematically detect dynamic fluctuations of Cys activity in living cells under different stimulation. The observations indicated that the endogenous Cys activity was depressed when HepG2 cells were under oxidative stress status; however, a dramatic expansion of Cys levels in HepG2 cells with omeprazole stimulation. In particular, MCyA has been successfully used to image the upregulation of Cys level in HepG2 cells in the presence of methionine (Met). Overall, MCyA would be a novel and practical tool to study Cys-related physiological and pathological processes.

Near-Infrared Fluorescence Imaging of Renal Cell Carcinoma with ASP5354 in a Mouse Model for Intraoperative Guidance.

Renal cell carcinoma is a prevalent disease associated with high morbidity and mortality rates. Partial nephrectomy is a first-line surgical option because it allows the preservation of renal function. Clear differentiation between normal and cancerous tissues is critical for increasing the negative margin rates. This study investigated the capability of the near-infrared (NIR) fluorescent imaging agent ASP5354 for in vivo fluorescence imaging of renal cell carcinoma. ASP5354 at a single dose of 12 nmol (0.037 mg)/kg body weight was intravenously administered to healthy and orthotopic renal cell carcinoma mice under anesthesia. NIR images of the abdominal cavity were obtained using a near-infrared fluorescence (NIRF) camera system. In addition, the cancerous kidneys were harvested, and the NIRF in their sections was measured using an NIRF microscope. Normal renal tissue emitted strong NIRF but the cancer tissue did not. The difference in NIRF intensity between the normal and cancer tissues clearly presented the boundary between the normal and cancer tissues in macro and micro NIRF imaging. ASP5354 can distinguish cancer tissue from normal tissue using NIRF. Thus, ASP5354 is a promising agent for renal cell carcinoma tissue imaging in partial nephrectomy for renal cell carcinoma patients.

Nitrogen-Embedded Quintuple [7]Helicene: A Helicene-Azacorannulene Hybrid with Strong Near-Infrared Fluorescence.

Herein, a nitrogen-embedded quintuple [7]helicene (N-Q7H) with an azapentabenzocorannulene core, which can be considered to be a helicene/azacorannulene hybrid π-system, was synthesized from azapentabenzocorannulene in a three-step process. N-Q7H is the first example of a multiple helicene with an azabuckybowl core. Single-crystal X-ray diffractometry unambiguously confirmed the structure of the propeller-shaped hybrid π-system. Owing to nitrogen-atom doping in the multiple helicenes and effective hybridization between the helicene and azacorannulene, N-Q7H exhibits considerably redshifted absorption and emission (yellow-to-green color change and green-to-near-infrared fluorescence change) relative to the azapentabenzocorannulene core. The broad absorption from the ultraviolet-visible to the NIR region is ascribable to the allowed transition between the highest occupied molecular orbital and the lowest unoccupied molecular orbital after symmetry breaking, as revealed by density functional theory calculations. Compared to previous propeller-shaped multiple helicenes with corannulene or hexabenzocoronene (etc.) as cores, N-Q7H demonstrates a significantly higher NIR fluorescence quantum efficiency of 28%. Additionally, the chiral-resolution and redox properties of N-Q7H were investigated. The excellent photophysical and inherent chiral properties of N-Q7H suggest that azapentabenzocorannulene can be used as an outstanding nitrogen-embedded core to construct novel multiple helicenes with wide application potential, including as NIR fluorescent bio-probes.

Molecular Visualization of Early-Stage Acute Kidney Injury with a DNA Framework Nanodevice.

DNA nanomachines with artificial intelligence have attracted great interest, which may open a new era of precision medicine. However, their in vivo behavior, including early diagnosis and therapeutic effect are limited by their targeting efficiency. Here, a tetrahedral DNA framework (TDF)‐based nanodevice for in vivo near‐infrared (NIR) diagnosis of early‐stage AKI is developed. This nanodevice comprises three functional modules: a size‐tunable TDF nanostructure as kidney‐targeting vehicle, a binding module for the biomarker kidney injury molecule‐1 (Kim‐1), and a NIR signaling module. The cooperation of these modules allows the nanodevice to be selectively accumulated in injured kidney tissues with high Kim‐1 level, generating strong NIR fluorescence; whereas the nanodevice with the proper size can be rapidly cleared in healthy kidneys to minimize the background. By using this nanodevice, the early diagnosis of AKI onset is demonstrated at least 6 h ahead of Kim‐1 urinalysis, or 12 h ahead of blood detection. It is envisioned that this TDF‐based nanodevice may have implications for the early diagnosis of AKI and other kidney diseases.

Assessment and Comparison of Three Dimensional Exoscopes for Near-Infrared Fluorescence-Guided Surgery Using Second-Window Indocyanine-Green.

ObjectiveCompared to microscopes, exoscopes have advantages in field-depth, ergonomics, and educational value. Exoscopes are especially well-poised for adaptation into fluorescence-guided surgery (FGS) due to their excitation source, light path, and image processing capabilities. We evaluated the feasibility of near-infrared FGS using a 3-dimensional (3D), 4 K exoscope with near-infrared fluorescence imaging capability. We then compared it to the most sensitive, commercially-available near-infrared exoscope system (3D and 960 p). In-vitro and intraoperative comparisons were performed. MethodsSerial dilutions of indocyanine-green (1–2000 μg/mL) were imaged with the 3D, 4 K Olympus Orbeye (system 1) and the 3D, 960 p VisionSense Iridium (system 2). Near-infrared sensitivity was calculated using signal-to-background ratios (SBRs). In addition, three patients with brain tumors were administered indocyanine-green and imaged with system 1, with two also imaged with system 2 for comparison. ResultsSystems 1 and 2 detected near-infrared fluorescence from indocyanine green concentrations of >250 μg/L and >31.3 μg/L, respectively. Intraoperatively, system 1 visualized strong near-infrared fluorescence from two, strongly gadolinium-enhancing meningiomas (SBR=2.4, 1.7). The high-resolution, bright images were sufficient for the surgeon to appreciate the underlying anatomy in the near-infrared mode. However, system 1 was not able to visualize fluorescence from a weakly-enhancing intraparenchymal metastasis. In contrast, system 2 successfully visualized both the meningioma and the metastasis but lacked high resolution stereopsis. ConclusionThree-dimensional exoscope systems provide an alternative visualization platform for both standard microsurgery and near-infrared fluorescent guided surgery. However, when tumor fluorescence is weak (i.e., low fluorophore uptake, deep tumors), highly sensitive near-infrared visualization systems may be required.

Photo-Enhanced Chemotherapy Performance in Bladder Cancer Treatment via Albumin Coated AIE Aggregates

The implementation of cisplatin-based neoadjuvant chemotherapy (NAC) plays a key role in conjunction with surgical resection in preventing bladder cancer progression and recurrence. However, the significant dose-dependent toxic side effects of NAC are still a major challenge. To solve this problem, we developed a photoenhanced cancer chemotherapy (PECC) strategy based on AIEgen ((E)-3-(2-(2-(5-(4-(diphenylamino)phenyl)thiophen-2-yl)vinyl)-1,1-dimethyl-1H-3λ4-benzo[e]indol-3-yl)propane-1-sulfonate), which is abbreviated as BITT. Multifunctional BITT@BSA-DSP nanoparticles (NPs) were employed with an albumin-based nanocarrier decorated with the cisplatin(IV) prodrug and loaded to produce strong near-infrared fluorescence imaging (NIR FLI), and they exhibited good photoenhancement performance via photodynamic therapy (PDT) and photothermal therapy (PTT). In vitro results demonstrated that BITT@BSA-DSP NPs could be efficiently taken up by bladder cancer cells and reduced to release Pt (II) under reductase, ensuring the chemotherapy effect. Furthermore, both in vitro and in vivo evaluation verified that the integration of NIR FL imaging-guided PECC efficiently promoted the sensitivity of bladder cancer to cisplatin chemotherapy with negligible side effects. This work provides a promising strategy to enhance the sensitivity of multiple cancers to chemotherapy drugs and even achieve effective treatments for drug-resistant cancers.

Mulberry-Leaves-Derived Red-Emissive Carbon Dots for Feeding Silkworms to Produce Brightly Fluorescent Silk.

Fluorescent silk has promising applications in dazzling textiles, biological engineering, and medical products, but the natural Bombyx mori silk has almost no fluorescence. Here carbon dots (CDs) made from mulberry leaves are reported, which have a strong near-infrared fluorescence with absolute quantum yield of 73% and a full width at half maximum of 20nm. After feeding with such CDs, silkworms exhibit bright red fluorescence, grow healthily, cocoon normally, and turn to moths finally. The cocoons are pink in daylight and show bright red fluorescence under ultraviolet light. After breaking out of such cocoons, the red-emissive moths can mate and lay fluorescent eggs which would hatch normally. The growth cycle of the second generation of the test silkworm is the same as that of the control group, which means such CDs have excellent biocompatiblility. Dissection and analyses on both the test silkworms and cocoons disclose the metabolic route of the CDs, that is, the fluorescent CDs are absorbed by silkworms from alimentary canals, then transferred to silk glands, and finally to cocoons, while those unabsorbed CDs are excreted with the feces. All experimental results confirm the excellent biocompatibility and fluorescence stability of such CDs.

Novel meso-trifluoromethyl BODIPY-based near-infrared-emitting fluorescent probes for organelle-specific imaging of cellular viscosity

Fluorescent molecular rotors play vital roles in understanding the function of cellular viscosity changes and its abnormal fluctuations are closely associated with many diseases. Despite numerous efforts spent, it remains an urgent and important topic to develop improved viscosity probes with near-infrared fluorescence, high sensitivity and low background. In this manuscript, for the first time, we reported two novel monostyryl boron dipyrromethenes (BODIPYs) bearing a rotatable trifluoromethyl group (CF3) at the meso position and a triphenylphosphonium (4) or morpholine (6) substituent, which could successfully serve as highly sensitive and near-infrared-emitting fluorescent probes for imaging cellular viscosity in mitochondria or lysosome. These probes could be prepared through Knoevenagel condensation under mild conditions and showed negligible emissions in the low viscous solvents. However in high viscous glycerol, strong near-infrared fluorescence at 657 nm appeared, ascribed to the substantially restricted rotation of the CF3 group. Their fluorescence intensity (log I) at 657 nm exhibited a good linear relationship with viscosity (log η) in the whole test range of 1–950 cP. Limit of detection for viscosity of mitochondria-targeting probe 4 was relatively lower than that of lysosome-targeting probe 6. These probes both showed no cytotoxicity and good mitochondrial or lysosomal localization. Interestingly, mitochondria-targeting probe 4 exhibited a remarkable intracellular fluorescence enhancement with viscosity increase induced by LPS or nystatin, which was better than lysosome-targeting probe 6. These two novel BODIPY-based fluorescent rotors provide a new strategy for developing near-infrared-emitting and organelle-specific fluorescent probes for cellular viscosity, which might be useful in exploring the functions of viscosity in various diseases.

Fabrication of semiconducting polymer-blend dots with strong near-infrared fluorescence and afterglow luminescence for bioimaging

Fluorescence imaging at longer wavelength and autofluorescence-free imaging were two main strategies to improve the optical imaging performance of traditional near-infrared (NIR) fluorescence imaging, and the design of corresponding imaging agents were heavily explored recently. Herein, polymer-blend dots (PBdots) with strong fluorescence and afterglow luminescence in both NIR-I (700–900 nm) and NIR-II (900–1700 nm) windows were successfully fabricated by encapsulating two functional semiconducting polymers into one nanoparticle. With efficient intra-particle interactions, the PBdots exhibited an afterglow lifetime of 181 s after 730 nm NIR laser activation, which can be activated in vivo. The obtained PBdots with similar emission intensities in NIR-I and NIR-II regions enable fair comparison between different optical imaging modalities, which provides a clear guidance for the choice of suitable imaging modality for different purpose. As the first imaging agents which integrate NIR-II fluorescence imaging and NIR-I afterglow imaging, the PBdots also provide both high resolution and large signal-to-background ratio for blood vessel, lymph node and tumor imaging in living mice.

Sensing and imaging of exosomal CD26 secreted from cancer cells and 3D colorectal tumor model using a novel near-infrared fluorogenic probe

Cancer-derived exosomes or their specific components hold great promise for early diagnosis and precise staging of cancers. This work aimed to construct a novel enzyme-activatable fluorescent substrate for real-time detection and in situ imaging of a key exosomal surface protein CD26 in various biological systems, as well as to reveal the relevance of exosomal CD26 to the tumorigenesis. For these purposes, a group of Gly-Pro amides deriving from several near-infrared fluorophores were designed on the basis of the unique prolyl-cleaving dipeptidease activity of CD26, while molecular docking simulations were applied to assess the possibility of the designed amides as CD26 specific substrates. Following virtual screening and experimental validation, it was observed that GP-ACM displayed the best combination of high sensitivity and excellent specificity to CD26. The sensing and imaging ability of GP-ACM towards CD26 were examined in a range of biological systems, such as living cells, in situ tissues, and the exosomes secreted from cancer cells. Under physiological conditions, GP-ACM can be readily hydrolyzed by CD26 to release the fluorescent product ACM. The fluorescent product emits strong near-infrared fluorescence signals around 660 nm, which can be easily captured by the devices equipped with a fluorescence detector. GP-ACM prolyl-cleaving reaction shows excellent specificity and rapid response towards CD26, while its fluorescent product ACM displays good chemical stability and outstanding photostability. With the help of GP-ACM, CD26 in living cells, tissues and the tumor-secreted exosomes can be real-time monitored and in-situ imaged, while further investigations reveal that the exosomal CD26 activities are abnormally elevated with the progression of colon tumor. Collectively, the present study offers a practical optical assay for real-time monitoring CD26 activities in multiple complex biological systems including the exosomes secreted by tumor cells. The simplicity and effectiveness of this assay hold great potential for facilitating fundamental researches and clinical diagnosis of exosomal CD26 associated diseases.

Second window ICG predicts gross-total resection and progression-free survival during brain metastasis surgery.

Metastases are the most common intracranial malignancies and complete resection can provide relief of neurological symptoms and reduce recurrence. The authors' prospective pilot study in 2017 demonstrated promising results for the application of high-dose, delayed imaging of indocyanine green (ICG), known as second window ICG (SWIG), in patients undergoing surgery for brain metastases. In this prospective cohort study, the authors evaluated intraoperative imaging and clinical outcomes of treatment using SWIG. Patients were prospectively enrolled in an approved study of high-dose, delayed ICG (SWIG) and received 5 mg/kg (2014-2018) or 2.5 mg/kg (2018-2019) ICG 24 hours preoperatively. Intraoperatively, near-infrared (NIR) imaging was performed using a dedicated NIR exoscope. NIR images were analyzed and the signal-to-background ratio (SBR) was calculated to quantify fluorescence. Residual fluorescence on the postresection NIR view was compared and correlated to the residual gadolinium enhancement on postoperative MRI. Patient survival and predictive factors were analyzed. In total, 51 intracranial metastases were surgically treated in 47 patients in this cohort. All 51 metastatic tumors demonstrated strong NIR fluorescence (mean SBR 4.9). In tumors ≤ 10 mm from the cortical surface, SWIG with 5 mg/kg ICG produced enhanced transdural tumor visibility (91.3%) compared to 2.5 mg/kg (52.9%; p = 0.0047). Neoplastic margin detection using NIR fluorescence compared to white light improved sensitivity, albeit lowered specificity; however, increasing the SBR cutoff for positive fluorescence significantly improved specificity without sacrificing sensitivity, increasing the overall accuracy from 57.5% to 72.5%. A lack of residual NIR fluorescence after resection was closely correlated with a lack of residual enhancement on postoperative MRI (p = 0.007). Among the 16 patients in whom tumor recurred at the site of surgery, postoperative MRI successfully predicted 8 cases, whereas the postresection NIR view predicted 12 cases. Progression-free survival rate at 12 months was greater for patients without residual NIR fluorescence (38%) than for those without residual enhancement on postoperative MRI (29%). The current study demonstrates the clinical benefits of the SWIG technique in surgery for patients with brain metastases. Specifically, this technique allows for dose-dependent, transdural localization of neoplasms and improved sensitivity in neoplastic margin detection. Postresection residual fluorescence can be a powerful tool to evaluate extent of resection in conjunction with MRI, and it may guide decisions on brain metastasis management.