First-in-human study of PET and optical dual-modality image-guided surgery in glioblastoma using 68Ga-IRDye800CW-BBN

Surgical outcomes of glioblastoma multiforme in low and middle-income countries: current state and future directions

Glioblastoma (GBM) is a highly aggressive and deadly brain tumor. The challenges in managing GBM in low- and middle-income countries (LMICs) have been underexplored. This review provides a review of surgical management techniques, challenges, outcomes, and future directions for GBM treatment in LMICs. A search of academic databases yielded studies from various LMICs, focusing on surgical management techniques and their outcomes. The data were analyzed in the context of socio-economic, cultural, and infrastructural factors. Comparative analyses were performed to highlight disparities between LMICs and high-income countries. GBM management in LMICs faces multi-faceted challenges, including healthcare infrastructure deficiencies, delayed diagnosis, high treatment costs, cultural beliefs, and limited research funding. This adversely affects patient outcomes and survival rates. Surgical excision followed by radiation and chemotherapy remains the standard of care, but LMICs have not significantly benefited from recent advancements in GBM management. Intraoperative neurosurgery ultrasound is identified as an affordable and practical alternative for LMICs. Patient outcomes following GBM surgery in LMICs vary widely, making early detection challenging. Cultural sensitivity and ethical considerations are crucial factors in improving healthcare practices. Surgical management of GBM in LMICs is hindered by complex challenges that require multi-faceted interventions. By addressing socio-economic, cultural, and infrastructural factors, LMICs can improve GBM care and outcomes. Raising awareness and advocating for change are crucial steps in this process.

Early Detection and Noninvasive Staging of Kidney Dysfunction by a PEGylated Conventional Fluorophore via GFR-Sensitive Renal Transport

Noninvasive fluorescence imaging of renal function is a valuable technique for understanding kidney disease progression and the development of renal medicine. This technique requires sensitive imaging probes for reporting renal dysfunction accurately at early stage. Herein, a molecularly engineered imaging probe (800CW-PEG45-COOH) was synthesized by simply PEGylating conventional near-infrared fluorophore IRDye800CW with NH2-PEG45-COOH (molecular weight ∼2100 Da) for early detection and staging of renal dysfunction through noninvasive real-time kidney imaging. 800CW-PEG45-COOH not only cleared through the kidney efficiently (>90% injection dosage at 24 h postinjection) but was also found to be freely filtered by glomeruli without renal tubular reabsorption and secretion. Despite this simple construction strategy, the transport of 800CW-PEG45-COOH within the kidneys was extremely sensitive to the alteration of the glomerular filtration rate (GFR), which enabled it to detect renal dysfunction much earlier than commonly used serum biomarkers and stage kidney function impairments (mild vs severe dysfunction) via imaging-based kidney clearance kinetics. This work not only provides a promising optical imaging probe for the noninvasive evaluation of kidney function but also highlights the utility of PEGylation in enhancing the performance of conventional organic dyes in biomedical applications.

Miniaturized Fab' imaging probe derived from a clinical antibody: Characterization and imaging in CRISPRi-attenuated mammary tumor models

Clinical imaging-assisted oncosurgical navigation requires cancer-specific miniaturized optical imaging probes. We report a near-infrared (NIR) Fab'-based epidermal growth factor receptor (EGFR)-specific probe carrying 3 NIR fluorophores (Fab'-800CW), which retained high-affinity binding to EGFR ectodomain (equilibrium KD E = 1 nM). Fab'-800CW showed a robust 4-times gain of fluorescence intensity (FI) and a 20% lifetime (FLT) increase under the conditions mimicking intracellular degradation. The probe was tested by using triple-negative breast cancer (TNBC) cell lines obtained by applying CRISPR interference (CRISPRi) effect of EGFR-targeting sgRNA and dCas9-KRAB chimera coexpression in MDA-MB-231 cells (WT cells). FI imaging in cell culture proved a 50% EGFR expression attenuation by CRISPRi. FI imaging in animals harboring attenuated or WT TNBC tumors with ex vivo corroboration identified differences between WT and CRISPRi tumors FI at 30 min post injection. Our results suggest the feasibility of EGFR expression imaging using a Fab'-based probe relevant for imaging-guided cancer surgery.

Near-infrared II fluorescence-guided glioblastoma surgery targeting monocarboxylate transporter 4 combined with photothermal therapy

BACKGROUND

Surgery is crucial for glioma treatment, but achieving complete tumour removal remains challenging. We evaluated the effectiveness of a probe targeting monocarboxylate transporter 4 (MCT4) in recognising gliomas, and of near-infrared window II (NIR-II) fluorescent molecular imaging and photothermal therapy as treatment strategies.

METHODS

We combined an MCT4-specific monoclonal antibody with indocyanine green to create the probe. An orthotopic mouse model and a transwell model were used to evaluate its ability to guide tumour resection using NIR-II fluorescence and to penetrate the blood-brain barrier (BBB), respectively. A subcutaneous tumour model was established to confirm photothermal therapy efficacy. Probe specificity was assessed in brain tissue from mice and humans. Finally, probe effectiveness in photothermal therapy was investigated.

FINDINGS

MCT4 was differentially expressed in tumour and normal brain tissue. The designed probe exhibited precise tumour targeting. Tumour imaging was precise, with a signal-to-background (SBR) ratio of 2.8. Residual tumour cells were absent from brain tissue postoperatively (SBR: 6.3). The probe exhibited robust penetration of the BBB. Moreover, the probe increased the tumour temperature to 50 °C within 5 min of laser excitation. Photothermal therapy significantly reduced tumour volume and extended survival time in mice without damage to vital organs.

INTERPRETATION

These findings highlight the potential efficacy of our probe for fluorescence-guided surgery and therapeutic interventions.

FUNDING

Jilin Province Department of Science and Technology (20200403079SF), Department of Finance (2021SCZ06) and Development and Reform Commission (20200601002JC); National Natural Science Foundation of China (92059207, 92359301, 62027901, 81930053, 81227901, U21A20386); and CAS Youth Interdisciplinary Team (JCTD-2021-08).

Lessons learned in application driven imaging agent design for image-guided surgery

To meet the growing demand for intraoperative molecular imaging, the development of compatible imaging agents plays a crucial role. Given the unique requirements of surgical applications compared to diagnostics and therapy, maximizing translational potential necessitates distinctive imaging agent designs. For effective surgical guidance, exogenous signatures are essential and are achievable through a diverse range of imaging labels such as (radio)isotopes, fluorescent dyes, or combinations thereof. To achieve optimal in vivo utility a balanced molecular design of the tracer as a whole is required, which ensures a harmonious effect of the imaging label with the affinity and specificity (e.g., pharmacokinetics) of a pharmacophore/targeting moiety. This review outlines common design strategies and the effects of refinements in the molecular imaging agent design on the agent's pharmacological profile. This includes the optimization of affinity, pharmacokinetics (including serum binding and target mediated background), biological clearance route, the achievable signal intensity, and the effect of dosing hereon.

Targeted Radionuclide Therapy in Glioblastoma

Despite the development of various novel therapies, glioblastoma (GBM) remains a devastating disease, with a median survival of less than 15 months. Recently, targeted radionuclide therapy has shown significant progress in treating solid tumors, with the approval of Lutathera for neuroendocrine tumors and Pluvicto for prostate cancer by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA). This achievement has shed light on the potential of targeted radionuclide therapy for other solid tumors, including GBM. This review presents the current status of targeted radionuclide therapy in GBM, highlighting the commonly used therapeutic radionuclides emitting alpha, beta particles, and Auger electrons that could induce potent molecular and cellular damage to treat GBM. We then explore a range of targeting vectors, including small molecules, peptides, and antibodies, which selectively target antigen-expressing tumor cells with minimal or no binding to healthy tissues. Considering that radiopharmaceuticals for GBM are often administered locoregionally to bypass the blood-brain barrier (BBB), we review prominent delivery methods such as convection-enhanced delivery, local implantation, and stereotactic injections. Finally, we address the challenges of this therapeutic approach for GBM and propose potential solutions.

Fluorescence imaging-guided surgery: current status and future directions

Surgery is one of the most important paradigms for tumor therapy, while fluorescence imaging (FI) offers real-time intraoperative guidance, greatly boosting treatment prognosis. The imaging fidelity heavily relies on not only imaging facilities but also probes for imaging-guided surgery (IGS). So far, a great number of IGS probes with emission in visible (400-700 nm) and near-infrared (NIR 700-1700 nm) windows have been developed for pinpointing disease margins intraoperatively. Herein, the state-of-the-art fluorescent probes for IGS are timely updated, with a special focus on the fluorescent probes under clinical examination. For a better demonstration of the superiority of NIR FI over visible FI, both imaging modalities are critically compared regarding signal-to-background ratio, penetration depth, resolution, tissue autofluorescence, photostability, and biocompatibility. Various types of fluorescence IGS have been summarized to demonstrate its importance in the medical field. Furthermore, the most recent progress of fluorescent probes in NIR-I and NIR-II windows is summarized. Finally, an outlook on multimodal imaging, FI beyond NIR-II, efficient tumor targeting, automated IGS, the use of AI and machine learning for designing fluorescent probes, and the fluorescence-guided da Vinci surgical system is given. We hope this review will stimulate interest among researchers in different areas and expedite the translation of fluorescent probes from bench to bedside.

Application of quantum dots in brain diseases and their neurotoxic mechanism

The early-stage diagnosis and therapy of brain diseases pose a persistent challenge in the field of biomedicine. Quantum dots (QDs), nano-luminescent materials known for their small size and fluorescence imaging capabilities, present promising capabilities for diagnosing, monitoring, and treating brain diseases. Although some investigations about QDs have been conducted in clinical trials, the concerns about the toxicity of QDs have continued. In addition, the lack of effective toxicity evaluation methods and systems and the difference between in vivo and in vitro toxicity evaluation hinder QDs application. The primary objective of this paper is to introduce the neurotoxic effects and mechanisms attributable to QDs. First, we elucidate the utilization of QDs in brain disorders. Second, we sketch out three pathways through which QDs traverse into brain tissue. Ultimately, expound upon the adverse consequences of QDs on the brain and the mechanism of neurotoxicity in depth. Finally, we provide a comprehensive summary and outlook on the potential development of quantum dots in neurotoxicity and the difficulties to be overcome.

Synthesis and preclinical evaluation of a novel PET/fluorescence dual-modality probe targeting fibroblast activation protein

Early diagnosis and precise surgical intervention are crucial for cancer patients. We aimed to develop a novel positron emission tomography (PET)/fluorescence dual-modality probe for preoperative diagnosis, intraoperative guidance, and postoperative monitoring of fibroblast activation protein (FAP)-positive tumors. FAPI-FAM was synthesized and labeled with gallium-68. [68Ga]Ga-FAPI-FAM showed favorable in vivo and in vitro characteristics, specific binding affinity, and excellent tumor accumulation in FAP-positive cells and mice xenografts. Excellent tumor-to-background contrast was found owing to high tumor uptake, prolonged retention, and rapid renal clearance of [68Ga]Ga-FAPI-FAM. Moreover, a specific fluorescence signal was detected in FAP-positive tumors during ex vivo fluorescence imaging, demonstrating the feasibility of whole-body tumor detection and intraoperative tumor delineation.

Recent Progress in Peptide-Based Molecular Probes for Disease Bioimaging

Recent strides in molecular pathology have unveiled distinctive alterations at the molecular level throughout the onset and progression of diseases. Enhancing the in vivo visualization of these biomarkers is crucial for advancing disease classification, staging, and treatment strategies. Peptide-based molecular probes (PMPs) have emerged as versatile tools due to their exceptional ability to discern these molecular changes with unparalleled specificity and precision. In this Perspective, we first summarize the methodologies for crafting innovative functional peptides, emphasizing recent advancements in both peptide library technologies and computer-assisted peptide design approaches. Furthermore, we offer an overview of the latest advances in PMPs within the realm of biological imaging, showcasing their varied applications in diagnostic and therapeutic modalities. We also briefly address current challenges and potential future directions in this dynamic field.

Translocator Protein 18 kDa (TSPO): A Promising Molecular Target for Image-Guided Surgery of Solid Cancers

The translocator protein 18-kDa (TSPO) is a mitochondrial membrane protein that is previously identified as the peripheral benzodiazepine receptor (PBR). Furthermore, it plays a significant role in a diverse range of biochemical processes, including steroidogenesis, mitochondrial cholesterol transport, cell survival and death, cell proliferation, and carcinogenesis. Several investigations also reported its roles in various types of cancers, including colorectal, brain, breast, prostate, and lung cancers, as well as melanoma. According to a previous study, the expression of TSPO was upregulated in cancer cells, which corresponds to an aggressive phenotype and/or poor prognosis. Consequently, the potential for crafting diagnostic and prognostic tools with a focus on TSPO holds great potential. In this context, several radioligands designed to target this protein have been identified, and some of the candidates have advanced to clinical trials. In recent years, the use of hybrid probes with radioactive and fluorescence molecules for image-guided surgery has exhibited promising results in animal and human studies. This indicates that the approach can serve as a valuable surgical navigator during cancer surgery. The current hybrid probes are built from various molecular platforms, including small molecules, nanoparticles, and antibodies. Although several TSPO-targeted imaging probes have been developed, their development for image-guided surgery of cancers is still limited. Therefore, this review aims to highlight recent findings on the involvement of TSPO in carcinogenesis, as well as provide a new perspective on the potential application of TSPO-targeted hybrid probes for image-guided surgery.

Unfolded Protein-Based Sandwich AIE Probe Imparts High Fluorescent Contrast for Pan-Cancer Surgical Navigation

Fluorescence imaging-guided navigation for cancer surgery has a promising clinical application. However, pan-cancer encompasses a wide variety of cancer types with significant heterogeneity, resulting in the lack of universal and highly contrasted fluorescent probes for surgical navigation. Here, we developed an aggregation-induced emission (AIE) probe (MI-AIE-TsG, MAT) with dual activation for pan-cancer surgical navigation. MAT weakly activates fluorescence by targeting the SUR1 protein on the endoplasmic reticulum (ER) through the TsG group. Subsequently, the sulfhydryl groups on the unfolded proteins, which are highly enriched in cancer ER, react with the maleimide (MI) of MAT through the thiol-ene click reaction, further enhancing the fluorescence. The formation of a SUR1-MAT-unfolded protein sandwich complex reinforces the restriction of intramolecular motion and eliminates photoinduced electron transfer of MAT, leading to high signal-to-noise (9.2) fluorescence imaging and use for surgical navigation of pan-cancer. The generally high content of unfolded proteins in cancer cells makes MAT imaging generalizable, and it currently has proven feasibility in ovarian, cervical, and breast cancers. Meanwhile, MAT promotes cellular autophagy by hindering protein folding, thereby inhibiting cancer cell proliferation. This generalizable, high-contrast AIE fluorescent probe spans the heterogeneity of pancreatic cancer, enabling precise pancreatic cancer surgery navigation and treatment.

Intratumor injected gold molecular clusters for NIR-II imaging and cancer therapy

Surgical resections of solid tumors guided by visual inspection of tumor margins have been performed for over a century to treat cancer. Near-infrared (NIR) fluorescence labeling/imaging of tumor in the NIR-I (800 to 900 nm) range with systemically administrated fluorophore/tumor-targeting antibody conjugates have been introduced to improve tumor margin delineation, tumor removal accuracy, and patient survival. Here, we show Au25 molecular clusters functionalized with phosphorylcholine ligands (AuPC, ~2 nm in size) as a preclinical intratumorally injectable agent for NIR-II/SWIR (1,000 to 3,000 nm) fluorescence imaging-guided tumor resection. The AuPC clusters were found to be uniformly distributed in the 4T1 murine breast cancer tumor upon intratumor (i.t.) injection. The phosphocholine coating afforded highly stealth clusters, allowing a high percentage of AuPC to fill the tumor interstitial fluid space homogeneously. Intra-operative surgical navigation guided by imaging of the NIR-II fluorescence of AuPC allowed for complete and non-excessive tumor resection. The AuPC in tumors were also employed as a photothermal therapy (PTT) agent to uniformly heat up and eradicate tumors. Further, we performed in vivo NIR-IIb (1,500 to 1,700 nm) molecular imaging of the treated tumor using a quantum dot-Annexin V (QD-P3-Anx V) conjugate, revealing cancer cell apoptosis following PTT. The therapeutic functionalities of AuPC clusters combined with rapid renal excretion, high biocompatibility, and safety make them promising for clinical translation.

Lower-grade gliomas surgery guided by GRPR-targeting PET/NIR dual-modality image probe: a prospective and single-arm clinical trial

Purpose: Lower-grade gliomas (LGGs) are a group of infiltrative growing glial brain tumors characterized by intricate intratumoral heterogeneity and subtle visual appearance differences from non-tumor tissue, which can lead to errors in pathologic tissue sampling. Although 5-ALA fluorescence has been an essential method for visualizing gliomas during surgery, its effectiveness is limited in the case of LGGs due to low sensitivity. Therefore, we developed a novel PET/NIR dual-modality image probe targeting gastrin-releasing peptide receptor (GRPR) in glioma cells to enhance tumor visualization and improve the accuracy of sampling. Methods: A prospective, non-randomized, single-center feasibility clinical trial (NCT03407781) was conducted in the referral center from October 21, 2016, to August 17, 2018. Consecutive enrollment included patients suspected of having LGGs and considered suitable candidates for surgical removal. Group 1 comprised ten patients who underwent preoperative 68Ga-IRDye800CW-BBN PET/MRI assessment followed by intraoperative fluorescence-guided surgery. Group 2 included 42 patients who underwent IRDye800CW-BBN fluorescence-guided surgery. The primary endpoints were the predictive value of preoperative PET imaging for intraoperative fluorescence and the sensitivity and specificity of fluorescence-guided sampling. Results: Thirty-nine patients were included in the in-depth analysis of endpoints, with 25 (64.1%) exhibiting visible fluorescence, while 14 (35.9%) did not. The preoperative positive PET uptake exhibited a greater accuracy in predicting intraoperative fluorescence compared to MRI enhancement (100% [10/10] vs. 87.2% [34/39]). A total of 125 samples were harvested during surgery. Compared with pathology, subjective fluorescence intensity showed a sensitivity of 88.6% and a specificity of 88.2% in identifying WHO grade III samples. For WHO grade II samples, the sensitivity and specificity of fluorescence were 54.7% and 88.2%, respectively. Conclusion: This study has demonstrated the feasibility of the novel dual-modality imaging technique for integrated pre- and intraoperative targeted imaging via the same molecular receptor in surgeries for LGGs. The PET/NIR dual-modality probe exhibits promise for preoperative surgical planning in fluorescence-guided surgery and provides greater accuracy in guiding tumor sampling compared to 5-ALA in patients with LGGs.

PET/NIR Fluorescence Bimodal Imaging for Targeted Tumor Detection

Cancer is one of the greatest threats to human health due to late diagnosis and incomplete resection. The bimodal probe combines positron emission tomography (PET) imaging for noninvasive whole-body scanning with intraoperative near-infrared fluorescence (NIRF) surgical guidance for preoperative tumor detection, tumor resection during surgery, and postoperative monitoring. We developed a new PET/NIRF bimodal imaging agent, [68Ga]Ga-DOTA-NPC, covalently coupled to DCDSTCY and DOTA via ethylenediamine and radiolabeled with gallium-68, and investigated it in vitro and in vivo. The probe was found to be preferential for colon cancer cells due to the organic anion-transporting polypeptide1B3 (OATP1B3). PET/NIRF imaging allowed us to confirm [68Ga]Ga-DOTA-NPC as a promising probe for tumor detection, as it provides good biosafety and high-contrast tumor accumulation. Orthotopic and subcutaneous colon tumors were successfully resected under real-time NIRF guidance. [68Ga]Ga-DOTA-NPC provides highly sensitive and unlimited tissue-penetrating PET/NIRF imaging, helping to visualize and differentiate tumors from adjacent tissue.

Resection of positive tissue on methionine-PET is associated with improved survival in glioblastomas

BACKGROUND AND PURPOSE

The volume of excised tumor in contrast-enhanced areas evaluated via magnetic resonance imaging is known to have a strong influence on the survival of patients with glioblastoma (GBM). In this study, we investigated the effect of tumor resection on the survival of patients with GBM in the 11 C-methionine (MET) accumulation area using MET-positron emission tomography (MET-PET).

METHODS

A total of 26 patients (median age, 69 years; 15 males) who had undergone tumor resection and MET-PET before and after surgery, after being newly diagnosed with GBM, were included in the study. MET-PET before and after tumor resection were compared. The association between the decrease in the maximum standardized uptake value (SUV) of the tumor divided by the normal cortical mean SUV (%; ΔT/N), the MET extent of resection (MET-EOR) from the % reduction in the MET accumulation area (%), and residual MET accumulation area (in cm3 ; MET-residual tumor volume [RTV]), as well as the survival time of patients with GBM, were evaluated via univariate analysis.

RESULTS

ΔT/N were positively associated with survival (hazard ratio [HR], 0.98 [95% confidence interval (CI), 0.97-0.99], p = .02). MET-RTV revealed a negative association with survival (HR, 1.02 [95% CI, 1.01-1.04], p = .04). Additionally, MET-EOR showed a strong trend with survival (HR, 0.99 [95% CI, 0.97-1.01], p = .06).

CONCLUSIONS

Surgical resection of MET-accumulated areas in GBM significantly prolongs the survival of patients with GBM. However, a prospective large-scale multicenter study is needed to confirm our findings.

Advances in Intraoperative Glioma Tissue Sampling and Infiltration Assessment

Gliomas are infiltrative brain tumors that often involve functional tissue. While maximal safe resection is critical for maximizing survival, this is challenged by the difficult intraoperative discrimination between tumor-infiltrated and normal structures. Surgical expertise is essential for identifying safe margins, and while the intraoperative pathological review of frozen tissue is possible, this is a time-consuming task. Advances in intraoperative stimulation mapping have aided surgeons in identifying functional structures and, as such, has become the gold standard for this purpose. However, intraoperative margin assessment lacks a similar consensus. Nonetheless, recent advances in intraoperative imaging techniques and tissue examination methods have demonstrated promise for the accurate and efficient assessment of tumor infiltration and margin delineation within the operating room, respectively. In this review, we describe these innovative technologies that neurosurgeons should be aware of.

Synthesis and Preclinical Fluorescence Imaging of Dually Functionalized Antibody Conjugates Targeting Endothelin Receptor-Positive Tumors

For the past two decades, the emerging role of the endothelin (ET) axis in cancer has been extensively investigated, and its involvement in several mechanisms described as "hallmarks of cancer" has clearly highlighted its potential as a therapeutic target. Despite the growing interest in finding effective anticancer drugs, no breakthrough treatment has successfully made its way to the market. Recently, our team reported the development of a new immuno-positron emission tomography probe targeting the ET A receptor (ETA, one of the ET receptors) that allows the successful detection of ETA+ glioblastoma, paving the way for the elaboration of novel antibody-based strategies. In this study, we describe the synthesis of two PET/NIRF (positron emission tomography/near-infrared fluorescence) dually functionalized imaging agents, directed against ETA or ETB, that could be used to detect ET+ tumors and select patients that will be eligible for fluorescence-guided surgery. Both imaging modalities were brought together using a highly versatile tetrazine platform bearing the IRDye800CW fluorophore and desferrioxamine for 89Zr chelation. This so-called monomolecular multimodal imaging probe was then "clicked", via an inverse-electron-demand Diels-Alder reaction, to antibodies conjugated site-specifically with a trans-cyclooctene group. This approach has led to homogeneous and well-defined constructs that retained their high affinity and high specificity for their respective target, as shown by flow cytometry and NIRF in vivo imaging experiments in nude mice bearing CHO-ETA and CHO-ETB tumors. Ultimately, these bimodal immunoconjugates could be used to improve the outcomes of patients with ET+ tumors.

New hybrid radio-fluorescent probes [131I]-BPF-01 and [131I]-BPF-02 for visualisation of cancer cells: Synthesis and preliminary in vitro and ex vivo evaluations

We synthesised and biologically evaluated two new hybrid probes [131I]BPF-01 and [131I]BPF-02 which were built from three structural entities: benzothiazole-phenyl, fluorescein isothiocyanate (FITC), and iodine-131. These probes were designed for potential applications in assisting surgical procedures of solid cancers. The cytotoxicity study demonstrated that fluorescent probes BPF-01 (31.23 μg/mL) and BPF-02 (250 μg/mL) were relatively not toxic to normal immortalized human keratinocytes (HaCaT) cells, as indicated by the percentage of cell survival above 50 %. Furthermore, both probes displayed low to moderate anticancer activity against the breast cancer cells (MDA-MB-231) and prostate cancer cells (LNCaP and DU-145). The probe BPF-01 apparently showed an accumulation in the tumour tissues, as suggested by ex vivo fluorescence examinations. In addition, the cellular uptake study suggests that hybrid probe [131I]-BPF-01 was potentially accumulated in the MCF-7 cell line with the highest uptake of 16.11 ± 1.52 % after 2 h of incubation, approximately 50-fold higher than the accumulation of iodine-131 (control). The magnetic bead assay suggests that [131I]-BPF-02 and [131I]-BPF-02 showed a promising capability to interact with translocator protein 18 kDa (TSPO). Moreover, the computational data showed that the binding scores for ligands 7-8, BPF-01 and BPF-02, and [131I]-BPF-01 and [131I]-BPF-02 in the TSPO were considerably high. Accordingly, fluorescent probes BPF-01 and BPF-02, and hybrid probes [131I]BPF-01 and [131I]BPF-02 can be further developed for targeting cancer cells during intraoperative tumour surgery.

A translational blueprint for developing intraoperative imaging agents via radiopharmaceutical-guided drug design

Cancer imaging is a rapidly evolving field due to the discovery of novel molecular targets and the availability of corresponding techniques to detect them with high precision, accuracy, and sensitivity. Nuclear medicine is the most widely used molecular imaging modality and has a growing toolkit of clinically used radiopharmaceuticals that enable whole-body tumor visualization, staging, and treatment monitoring for a variety of tumors in a non-invasive manner. The need for similar imaging capabilities in the operating room has led to the emergence of fluorescence-guided surgery (FGS) as a powerful technique that gives surgeons unprecedented ability to distinguish tumors from healthy tissues. While a variety of strategies have been used to develop contrast agents for FGS, the use of radiopharmaceuticals as models brings exceptional translational potential and has increasingly been explored. Here, we review strategies used to convert clinically used radiopharmaceuticals into fluorescent and multimodal counterparts. Unique preclinical and clinical capabilities stemming from radiopharmaceutical-based agent design are also discussed to illustrate the advantages of this approach.

Recent progress on near-infrared fluorescence heptamethine cyanine dye-based molecules and nanoparticles for tumor imaging and treatment

Recenly, near-infrared fluorescence heptamethine cyanine dyes have shown satisfactory values in bioengineering, biology, and pharmacy especially in cancer diagnosis and treatment, owing to their excellent fluorescence property and biocompatibility. In order to achieve broad application prospects, diverse structures, and chemical properties of heptamethine cyanine dyes have been designed to develop novel functional molecules and nanoparticles over the past decade. For fluorescence and photoacoustic tumor imaging properties, heptamethine cyanine dyes are equipped with good photothermal performance and reactive oxygen species production properties under near-infrared light irradiation, thus holding great promise in photodynamic and/or photothermal cancer therapies. This review offers a comprehensive scope of the structures, comparisons, and applications of heptamethine cyanine dyes-based molecules as well as nanoparticles in tumor treatment and imaging in current years. Therefore, this review may drive the development and innovation of heptamethine cyanine dyes, significantly offering opportunities for improving tumor imaging and treatment in a precise noninvasive manner. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Dual probe difference specimen imaging for prostate cancer margin assessment

Significance

Positive margin status due to incomplete removal of tumor tissue during radical prostatectomy for high-risk localized prostate cancer requires reoperation or adjuvant therapy, which increases morbidity and mortality. Adverse effects of prostate cancer treatments commonly include erectile dysfunction, urinary incontinence, and bowel dysfunction, making successful initial curative prostatectomy imperative.

Aim

Current intraoperative tumor margin assessment is largely limited to frozen section analysis, which is a lengthy, labor-intensive process that is obtrusive to the clinical workflow within the operating room (OR). Therefore, a rapid method for prostate cancer margin assessment in the OR could improve outcomes for patients.

Approach

Dual probe difference specimen imaging (DDSI), which uses paired antibody-based probes that are labeled with spectrally distinct fluorophores, was shown herein for prostate cancer margin assessment. The paired antibody-based probes consisted of a targeted probe to prostate-specific membrane antigen (PSMA) and an untargeted probe, which were used as a cocktail to stain resected murine tissue specimens including prostate tumor, adipose, muscle, and normal prostate. Ratiometric images (i.e., DDSI) of the difference between targeted and untargeted probe uptake were calculated and evaluated for accuracy using receiver operator characteristic curve analysis with area under the curve values used to evaluate the utility of the DDSI method to detect PSMA positive prostate cancer.

Results

Targeted and untargeted probe uptake was similar between the high and low PSMA expressing tumor due to nonspecific probe uptake after topical administration. The ratiometric DDSI approach showed substantial contrast difference between the PSMA positive tumors and their respective normal tissues (prostate, adipose, muscle). Furthermore, DDSI showed substantial contrast difference between the high PSMA expressing tumors and the minimally PSMA expressing tumors due to the ratiometric correction for the nonspecific uptake patterns in resected tissues.

Conclusions

Previous work has shown that ratiometic imaging has strong predictive value for breast cancer margin status using topical administration. Translation of the ratiometric DDSI methodology herein from breast to prostate cancers demonstrates it as a robust, ratiometric technique that provides a molecularly specific imaging modality for intraoperative margin detection. Using the validated DDSI protocol on resected prostate cancers permitted rapid and accurate assessment of PSMA status as a surrogate for prostate cancer margin status. Future studies will further evaluate the utility of this technology to quantitatively characterize prostate margin status using PSMA as a biomarker.

Preclinical assessment of IRDye800CW-labeled gastrin-releasing peptide receptor-targeting peptide for near infrared-II imaging of brain malignancies

We aimed to develop a new biocompatible gastrin-releasing peptide receptor (GRPR) targeted optical probe, IRDye800-RM26, for fluorescence image-guided surgery (FGS) of brain malignancies in near-infrared window II (NIR-II) imaging. We developed a novel GRPR targeting probe using a nine-amino-acid bombesin antagonist analog RM26 combined with IRDye800CW, and explored the fluorescent probe according to optical properties. Fluorescence imaging characterization in NIR-I/II region was performed in vitro and in vivo. Following simulated NIR-II image-guided surgery, we obtained time-fluorescent intensity curves and time-signal and background ratio curves. Further, we used histological sections of brain from tumor-beating mice model to compare imaging specificity between 5-aminolevulinic acid (5-ALA) and IRDye800-RM26, and evaluated biodistribution and biocompatibility. IRDye800-RM26 had broad emission ranging from 800 to 1200 nm, showing considerable fluorescent intensity in NIR-II region. High-resolution NIR-II imaging of IRDye800-RM26 can enhance the advantages of NIR-I imaging. Dynamic and real time fluorescence imaging in NIR-II region showed that the probe can be used to treat brain malignancies in mice between 12 and 24 h post injection. Its specificity in targeting glioblastoma was superior to 5-ALA. Biodistribution analysis indicated IRDye800-RM26 excretion in the kidney and liver. Histological and blood test analyses did not reveal acute severe toxicities in mice treated with effective dose (40 μg) of the probe for NIR-II imaging. Because of the considerable fluorescent intensity in NIR-II region and high spatial resolution, biocompatible and excretable IRDye800-RM26 holds great potentials for FGS, and is essential for translation into human use.

Pre- and Intraoperative Visualization of GRPR-Expressing Solid Tumors: Preclinical Profiling of Novel Dual-Modality Probes for Nuclear and Fluorescence Imaging

Image-guided surgery using a gastrin-releasing peptide receptor (GRPR)-targeting dual-modality probe could improve the accuracy of the resection of various solid tumors. The aim of this study was to further characterize our four previously developed GRPR-targeting dual-modality probes that vary in linker structures and were labeled with indium-111 and sulfo-cyanine 5. Cell uptake studies with GRPR-positive PC-3 cells and GRPR-negative NCI-H69 cells confirmed receptor specificity. Imaging and biodistribution studies at 4 and 24 h with 20 MBq/1 nmol [111In]In-12-15 were performed in nude mice bearing a PC-3 and NCI-H69 xenograft, and showed that the probe with only a pADA linker in the backbone had the highest tumor-to-organ ratios (T/O) at 24 h after injection (T/O > 5 for, e.g., prostate, muscle and blood). For this probe, a dose optimization study with three doses (0.75, 1.25 and 1.75 nmol; 20 MBq) revealed that the maximum image contrast was achieved with the lowest dose. Subsequently, the probe was successfully used for tumor excision in a simulated image-guided surgery setting. Moreover, it demonstrated binding to tissue sections of human prostate, breast and gastro-intestinal stromal tumors. In summary, our findings demonstrate that the developed dual-modality probe has the potential to aid in the complete surgical removal of GRPR-positive tumors.

Molecular and functional imaging in cancer-targeted therapy: current applications and future directions

Targeted anticancer drugs block cancer cell growth by interfering with specific signaling pathways vital to carcinogenesis and tumor growth rather than harming all rapidly dividing cells as in cytotoxic chemotherapy. The Response Evaluation Criteria in Solid Tumor (RECIST) system has been used to assess tumor response to therapy via changes in the size of target lesions as measured by calipers, conventional anatomically based imaging modalities such as computed tomography (CT), and magnetic resonance imaging (MRI), and other imaging methods. However, RECIST is sometimes inaccurate in assessing the efficacy of targeted therapy drugs because of the poor correlation between tumor size and treatment-induced tumor necrosis or shrinkage. This approach might also result in delayed identification of response when the therapy does confer a reduction in tumor size. Innovative molecular imaging techniques have rapidly gained importance in the dawning era of targeted therapy as they can visualize, characterize, and quantify biological processes at the cellular, subcellular, or even molecular level rather than at the anatomical level. This review summarizes different targeted cell signaling pathways, various molecular imaging techniques, and developed probes. Moreover, the application of molecular imaging for evaluating treatment response and related clinical outcome is also systematically outlined. In the future, more attention should be paid to promoting the clinical translation of molecular imaging in evaluating the sensitivity to targeted therapy with biocompatible probes. In particular, multimodal imaging technologies incorporating advanced artificial intelligence should be developed to comprehensively and accurately assess cancer-targeted therapy, in addition to RECIST-based methods.

In Vivo Evaluation of a Gallium-68-Labeled Tumor-Tracking Cyanine Dye for Positron Emission Tomography/Near-Infrared Fluorescence Carcinoma Imaging, Image-Guided Surgery, and Photothermal Therapy

Positron emission tomography (PET)/near-infrared fluorescence (NIRF) dual-modal imaging presents an enticing prospect for tumor diagnosis and surgical navigation. In this study, we developed a novel probe IR808-DOTA for tumor-targeted PET/NIRF imaging, image-guided surgery, and photothermal therapy. This construct had better water solubility and pharmacokinetics than IR808 and had similar photophysical properties, tumor targeting ability, and photothermal anticancer effect to IR808. By a simple labeling process, IR808-DOTA was labeled with gallium-68 and applied as a PET probe for tumor imaging in MCF-7 tumor xenografted mice. IR808-DOTA itself acted as an NIRF imaging agent in the following surgery for intraoperative navigation to aid surgeons in the delineation of tumor margins and visualizing sentinel lymph nodes to facilitate a more thorough tumor resection. Irradiation by laser, IR808-DOTA could prominently inhibit tumor growth in MCF-7 subcutaneous tumor model mice by directly ablating tumor cells, inhibiting tumor proliferation, and promoting tumor cell apoptosis. In summary, ⁶⁸Ga-DOTA-IR808 could enable a convenient and user-friendly workflow for tumor imaging and guided surgery, and therefore, it may have great prospects for clinical translation as a PET/NIRF dual-modal probe.

The Evolution of Fluorescence-Guided Surgery

There has been continual development of fluorescent agents, imaging systems, and their applications over the past several decades. With the recent FDA approvals of 5-aminolevulinic acid, hexaminolevulinate, and pafolacianine, much of the potential that fluorescence offers for image-guided oncologic surgery is now being actualized. In this article, we review the evolution of fluorescence-guided surgery, highlight the milestones which have contributed to successful clinical translation, and examine the future of targeted fluorescence imaging.

Targeted implementation strategies of precise photodynamic therapy based on clinical and technical demands

With the development of materials science, photodynamic-based treatments have gradually entered clinics. Photodynamic therapy is ideal for cancer treatment due to its non-invasive and spatiotemporal properties and is the first to be widely promoted in clinical practice. However, the shortcomings resulting from the gap between technical and clinical demands, such as phototoxicity, low tissue permeability, and tissue hypoxia, limit its wide applications. This article reviews the available data regarding the pharmacological and clinical factors affecting the efficacy of photodynamic therapy, such as photosensitizers and oxygen supply, disease diagnosis, and other aspects of photodynamic therapy. In addition, the synergistic treatment of photodynamic therapy with surgery and nanotechnology is also discussed, which is expected to provide inspiration for the design of photodynamic therapy strategies.

Targeting mTORC1 Activity to Improve Efficacy of Radioligand Therapy in Cancer

Radioligand therapy (RLT) represents an effective strategy to treat malignancy by cancer-selective delivery of radioactivity following systemic application. Despite recent therapeutic successes, cancer radioresistance and insufficient delivery of the radioactive ligands, as well as cytotoxicity to healthy organs, significantly impairs clinical efficacy. To improve disease management while minimizing toxicity, in recent years, the combination of RLT with molecular targeted therapies against cancer signaling networks showed encouraging outcomes. Characterization of the key deregulated oncogenic signaling pathways revealed their convergence to activate the mammalian target of rapamycin (mTOR), in which signaling plays an essential role in the regulation of cancer growth and survival. Therapeutic interference with hyperactivated mTOR pathways was extensively studied and led to the development of mTOR inhibitors for clinical applications. In this review, we outline the regulation and oncogenic role of mTOR signaling, as well as recapitulate and discuss mTOR complex 1 (mTORC1) inhibition to improve the efficacy of RLT in cancer.

Synthesis and Evaluation of Two Long-Acting SSTR2 Antagonists for Radionuclide Therapy of Neuroendocrine Tumors

Somatostatin receptor subtype 2 (SSTR2) has become an essential target for radionuclide therapy of neuroendocrine tumors (NETs). JR11 was introduced as a promising antagonist peptide to target SSTR2. However, due to its rapid blood clearance, a better pharmacokinetic profile is necessary for more effective treatment. Therefore, two JR11 analogs (8a and 8b), each carrying an albumin binding domain, were designed to prolong the blood residence time of JR11. Both compounds were labeled with lutetium-177 and evaluated via in vitro assays, followed by in vivo SPECT/CT imaging and ex vivo biodistribution studies. [177Lu]Lu-8a and [177Lu]Lu-8b were obtained with high radiochemical purity (>97%) and demonstrated excellent stability in PBS and mouse serum (>95%). [177Lu]Lu-8a showed better affinity towards human albumin compared to [177Lu]Lu-8b. Further, 8a and 8b exhibited binding affinities 30- and 48-fold lower, respectively, than that of the parent peptide JR11, along with high cell uptake and low internalization rate. SPECT/CT imaging verified high tumor accumulation for [177Lu]Lu-8a and [177Lu]Lu-JR11 at 4, 24, 48, and 72 h post-injection, but no tumor uptake was observed for [177Lu]Lu-8b. Ex vivo biodistribution studies revealed high and increasing tumor uptake for [177Lu]Lu-8a. However, its extended blood circulation led to an unfavorable biodistribution profile for radionuclide therapy.

PET/NIR-II fluorescence imaging and image-guided surgery of glioblastoma using a folate receptor α-targeted dual-modal nanoprobe

PURPOSE

The surgery of glioblastoma (GBM) requires a maximal resection of the tumor when it is safe and feasible. The infiltrating growth property of the GBM makes it a challenge for neurosurgeons to identify the tumor tissue even with the assistance of the surgical microscope. This highlights the urgent requirement for imaging techniques that can differentiate tumor tissues during surgery in real time. Fluorescence image-guided surgery of GBM has been investigated using several non-specific fluorescent probes that emit light in the visible and the first near-infrared window (NIR-I, 700-900 nm), which limit the detection accuracy because of the non-specific targeting mechanism and spectral characteristics. Targeted NIR-II (1000-1700 nm) fluorescent probes for GBM are thus highly desired. The folate receptor (FR) has been reported to be upregulated in GBM, which renders it to be a promising target for specific tumor imaging.

METHODS

In this study, the folic acid (FA) that can target the FR was conjugated with the clinically approved indocyanine green (ICG) dye and DOTA chelator for radiolabeling with ⁶⁴Cu to achieve targeted positron emission tomography (PET) and fluorescence imaging of GBM.

RESULTS

Surprisingly it was found that the resulted bioconjugate, DOTA-FA-ICG and non-radioactive ^natCu-DOTA-FA-ICG, were both self-assembled into nanoparticles with NIR-II emission signal. The radiolabeled DOTA-FA-ICG, ⁶⁴Cu-DOTA-FA-ICG, was found to specifically accumulate in the orthotopic GBM models using in vivo PET, NIR-II, and NIR-I fluorescence imaging. The best time window of fluorescence imaging was demonstrated to be 24 h after DOTA-FA-ICG injection. NIR-II fluorescence image-guided surgery was successfully conducted in the orthotopic GBM models using DOTA-FA-ICG. All the fluorescent tissue was removed and proved to be GBM by the H&E examination.

CONCLUSION

Overall, our study demonstrates that the probes, ⁶⁴Cu-DOTA-FA-ICG and DOTA-FA-ICG, hold promise for preoperative PET examination and intraoperative NIR-II fluorescence image-guided surgery of GBM, respectively.

Design, Synthesis and In Vivo Fluorescence Imaging Study of a Cytochrome P450 1B1 Targeted NIR Probe Containing a Chelator Moiety

Cytochrome P450 (CYP) 1B1 has been found to be overexpressed specifically in tumor tissues at early stage, which makes it a potential cancer biomarker for molecular imaging of cancer. Multimodal imaging combines different imaging modalities and offers more comprehensive information. Thus, imaging probes bearing more than one kind of signal fragment have been extensively explored and displayed great promise. Herein, we developed a near infrared (NIR) probe with a chelator moiety targeting CYP1B1 by conjugating α-naphthoflavone (ANF) derivatives with both a NIR dye and a chelator for potential application in bimodal imaging. Enzymatic inhibitory studies demonstrated inhibitory activity against CYP1B1 and selectivity among CYP1 were successfully retained after chemical modification. Cell-based saturation study indicated nanomolar range binding affinity between the probe and CYP1B1 overexpressed cancer cells. In vitro competitive binding assay monitored by confocal microscopy revealed that the probe could specifically accumulate in tumor cells. In vivo and ex vivo imaging studies demonstrated the probe could effectively lighten up the tumor tissues as early as 2 hours post injection. Besides, the fluorescence was significantly blocked by co-injection of CYP1B1 inhibitor, which indicated the probe accumulation in tumor sites was due to specific binding towards CYP1B1.

Refining Glioblastoma Surgery through the Use of Intra-Operative Fluorescence Imaging Agents

Glioblastoma (GBM) is the most aggressive adult brain tumour with a dismal 2-year survival rate of 26-33%. Maximal safe resection plays a crucial role in improving patient progression-free survival (PFS). Neurosurgeons have the significant challenge of delineating normal tissue from brain tumour to achieve the optimal extent of resection (EOR), with 5-Aminolevulinic Acid (5-ALA) the only clinically approved intra-operative fluorophore for GBM. This review aims to highlight the requirement for improved intra-operative imaging techniques, focusing on fluorescence-guided imaging (FGS) and the use of novel dyes with the potential to overcome the limitations of current FGS. The review was performed based on articles found in PubMed an.d Google Scholar, as well as articles identified in searched bibliographies between 2001 and 2022. Key words for searches included 'Glioblastoma' + 'Fluorophore'+ 'Novel' + 'Fluorescence Guided Surgery'. Current literature has favoured the approach of using targeted fluorophores to achieve specific accumulation in the tumour microenvironment, with biological conjugates leading the way. These conjugates target specific parts overexpressed in the tumour. The positive results in breast, ovarian and colorectal tissue are promising and may, therefore, be applied to intracranial neoplasms. Therefore, this design has the potential to produce favourable results in GBM by reducing the residual tumour, which translates to decreased tumour recurrence, morbidity and ultimately, mortality in GBM patients. Several preclinical studies have shown positive results with targeted dyes in distinguishing GBM cells from normal brain parenchyma, and targeted dyes in the Near-Infrared (NIR) emission range offer promising results, which may be valuable future alternatives.

Dual-Labelling Strategies for Nuclear and Fluorescence Molecular Imaging: Current Status and Future Perspectives

Molecular imaging offers the possibility to investigate biological and biochemical processes non-invasively and to obtain information on both anatomy and dysfunctions. Based on the data obtained, a fundamental understanding of various disease processes can be derived and treatment strategies can be planned. In this context, methods that combine several modalities in one probe are increasingly being used. Due to the comparably high sensitivity and provided complementary information, the combination of nuclear and optical probes has taken on a special significance. In this review article, dual-labelled systems for bimodal nuclear and optical imaging based on both modular ligands and nanomaterials are discussed. Particular attention is paid to radiometal-labelled molecules for single-photon emission computed tomography (SPECT) and positron emission tomography (PET) and metal complexes combined with fluorescent dyes for optical imaging. The clinical potential of such probes, especially for fluorescence-guided surgery, is assessed.

Targeted Dual-Modal PET/SPECT-NIR Imaging: From Building Blocks and Construction Strategies to Applications

Molecular imaging is an emerging non-invasive method to qualitatively and quantitively visualize and characterize biological processes. Among the imaging modalities, PET/SPECT and near-infrared (NIR) imaging provide synergistic properties that result in deep tissue penetration and up to cell-level resolution. Dual-modal PET/SPECT-NIR agents are commonly combined with a targeting ligand (e.g., antibody or small molecule) to engage biomolecules overexpressed in cancer, thereby enabling selective multimodal visualization of primary and metastatic tumors. The use of such agents for (i) preoperative patient selection and surgical planning and (ii) intraoperative FGS could improve surgical workflow and patient outcomes. However, the development of targeted dual-modal agents is a chemical challenge and a topic of ongoing research. In this review, we define key design considerations of targeted dual-modal imaging from a topological perspective, list targeted dual-modal probes disclosed in the last decade, review recent progress in the field of NIR fluorescent probe development, and highlight future directions in this rapidly developing field.

NIR-I Dye-Based Probe: A New Window for Bimodal Tumor Theranostics

Near-infrared (NIR, 650-1700 nm) bioimaging has emerged as a powerful strategy in tumor diagnosis. In particular, NIR-I fluorescence imaging (650-950 nm) has drawn more attention, benefiting from the high quantum yield and good biocompatibility. Since their biomedical applications are slightly limited by their relatively low penetration depth, NIR-I fluorescence imaging probes have been under extensive development in recent years. This review summarizes the particular application of the NIR-I fluorescent dye-contained bimodal probes, with emphasis on related nanoprobes. These probes have enabled us to overcome the drawbacks of individual imaging modalities as well as achieve synergistic imaging. Meanwhile, the application of these NIR-I fluorescence-based bimodal probes for cancer theranostics is highlighted.

Dual Probes for Positron Emission Tomography (PET) and Fluorescence Imaging (FI) of Cancer

Dual probes that possess positron emission tomography (PET) and fluorescence imaging (FI) capabilities are precision medicine tools that can be used to improve patient care and outcomes. Detecting tumor lesions using PET, an extremely sensitive technique, coupled with fluorescence-guided surgical resection of said tumor lesions can maximize the removal of cancerous tissue. The development of novel molecular probes is important for targeting different biomarkers as every individual case of cancer has different characteristics. This short review will discuss some aspects of dual PET/FI probes and explore the recently reported examples.

Site-Specific, Platform-Based Conjugation Strategy for the Synthesis of Dual-Labeled Immunoconjugates for Bimodal PET/NIRF Imaging of HER2-Positive Tumors

Because positron emission tomography (PET) and optical imaging are very complementary, the combination of these two imaging modalities is very enticing in the oncology field. Such bimodal imaging generally relies on imaging agents bearing two different imaging reporters. In the bioconjugation field, this is mainly performed by successive random conjugations of the two reporters on the protein vector, but these random conjugations can alter the vector properties. In this study, we aimed at abrogating the heterogeneity of the bimodal imaging immunoconjugate and mitigating the impact of multiple random conjugations. A trivalent platform bearing a DFO chelator for ⁸⁹Zr labeling, a NIR fluorophore, IRDye800CW, and a bioconjugation handle was synthesized. This bimodal probe was site-specifically grafted to trastuzumab via glycan engineering. This new bimodal immunoconjugate was then investigated in terms of radiochemistry, in vitro and in vivo, and compared to the clinically relevant random equivalent. In vitro and in vivo, our strategy provides several improvements over the current clinical standard. The combination of site-specific conjugation with the monomolecular platform reduced the heterogeneity of the final immunoconjugate, improved the resistance of the fluorophore toward radiobleaching, and reduced the nonspecific uptake in the spleen and liver compared to the standard random immunoconjugate. To conclude, the strategy developed is very promising for the synthesis of better defined dual-labeled immunoconjugates, although there is still room for improvement. Importantly, this conjugation strategy is highly modular and could be used for the synthesis of a wide range of dual-labeled immunoconjugates.

A Naked Eye-Invisible Ratiometric Fluorescent Microneedle Tattoo for Real-Time Monitoring of Inflammatory Skin Conditions

The field of portable healthcare monitoring devices has an urgent need for the development of real-time, noninvasive sensing and detection methods for various physiological analytes. Currently, transdermal sensing techniques are severely limited in scope (i.e., measurement of heart rate or sweat composition), or else tend to be invasive, often needing to be performed in a clinical setting. This study proposes a minimally invasive alternative strategy, consisting of using dissolving polymeric microneedles to deliver naked eye-invisible functional fluorescent ratiometric microneedle tattoos directly to the skin for real-time monitoring and quantification of physiological and pathological parameters. Reactive oxygen species are overexpressed in the skin in association with various pathological conditions. Here, one demonstrates for the first time the microneedle-based delivery to the skin of active fluorescent sensors in the form of an invisible, ratiometric microneedle tattoo capable of sensing reactive oxygen species in a reconstructed human-based skin disease model, as well as an in vivo model of UV-induced dermal inflammation. One also elaborates a universal ratiometric quantification concept coupled with a custom-built, multiwavelength portable fluorescence detection system. Fully realized, this approach presents an opportunity for the minimally invasive monitoring of a broad range of physiological parameters through the skin.

Intraoperative fluorescence molecular imaging accelerates the coming of precision surgery in China

Purpose

China has the largest cancer population globally. Surgery is the main choice for most solid cancer patients. Intraoperative fluorescence molecular imaging (FMI) has shown its great potential in assisting surgeons in achieving precise resection. We summarized the typical applications of intraoperative FMI and several new trends to promote the development of precision surgery.

Methods

The academic database and NIH clinical trial platform were systematically evaluated. We focused on the clinical application of intraoperative FMI in China. Special emphasis was placed on a series of typical studies with new technologies or high-level evidence. The emerging strategy of combining FMI with other modalities was also discussed.

Results

The clinical applications of clinically approved indocyanine green (ICG), methylene blue (MB), or fluorescein are on the rise in different surgical departments. Intraoperative FMI has achieved precise lesion detection, sentinel lymph node mapping, and lymphangiography for many cancers. Nerve imaging is also exploring to reduce iatrogenic injuries. Through different administration routes, these fluorescent imaging agents provided encouraging results in surgical navigation. Meanwhile, designing new cancer-specific fluorescent tracers is expected to be a promising trend to further improve the surgical outcome.

Conclusions

Intraoperative FMI is in a rapid development in China. In-depth understanding of cancer-related molecular mechanisms is necessary to achieve precision surgery. Molecular-targeted fluorescent agents and multi-modal imaging techniques might play crucial roles in the era of precision surgery.

PET/Fluorescence Imaging: An Overview of the Chemical Strategies to Build Dual Imaging Tools

Molecular imaging is a biomedical research discipline that has quickly emerged to afford the observation, characterization, monitoring, and quantification of biomarkers and biological processes in living organism. It covers a large array of imaging techniques, each of which provides anatomical, functional, or metabolic information. Multimodality, as the combination of two or more of these techniques, has proven to be one of the best options to boost their individual properties, hence offering unprecedented tools for human health. In this review, we will focus on the combination of positron emission tomography and fluorescence imaging from the specific perspective of the chemical synthesis of dual imaging agents. Based on a detailed analysis of the literature, this review aims at giving a comprehensive overview of the chemical strategies implemented to build adequate imaging tools considering radiohalogens and radiometals as positron emitters, fluorescent dyes mostly emitting in the NIR window and all types of targeting vectors.

Towards Complete Tumor Resection: Novel Dual-Modality Probes for Improved Image-Guided Surgery of GRPR-Expressing Prostate Cancer

Nuclear and optical dual-modality probes can be of great assistance in prostate cancer localization, providing the means for both preoperative nuclear imaging and intraoperative surgical guidance. We developed a series of probes based on the backbone of the established GRPR-targeting radiotracer NeoB. The inverse electron demand of the Diels–Alder reaction was used to integrate the sulfo-cyanine 5 dye. Indium-111 radiolabeling, stability studies and a competition binding assay were carried out. Pilot biodistribution and imaging studies were performed in PC-3 tumor-bearing mice, using the best two dual-labeled probes. The dual-modality probes were radiolabeled with a high yield (>92%), were proven to be hydrophilic and demonstrated high stability in mouse serum (>94% intact labeled ligand at 4 h). The binding affinity for the GRPR was in the nanomolar range (21.9–118.7 nM). SPECT/CT images at 2 h p.i. clearly visualized the tumor xenograft and biodistribution studies, after scanning confirmed the high tumor uptake (8.47 ± 0.46%ID/g and 6.90 ± 0.81%ID/g for probe [111In]In-12 and [111In]In-15, respectively). Receptor specificity was illustrated with blocking studies, and co-localization of the radioactive and fluorescent signal was verified by ex vivo fluorescent imaging. Although optimal tumor-to-blood and tumor-to-kidney ratios might not yet have been reached due to the prolonged blood circulation, our probes are promising candidates for the preoperative and intraoperative visualization of GRPR-positive prostate cancer.

Development and Preclinical Evaluation of a Near-Infrared Fluorescence Probe Based on Tailored Hepatitis B Core Particles for Imaging-Guided Surgery in Breast Cancer

PURPOSE

Tumor-free surgical margin is crucial but challenging in breast-conserving surgery (BCS). Fluorescence imaging is a promising strategy for surgical navigation that can reliably assist the surgeon with visualization Of the tumor in real-time. Notably, finding an optimized fluorescent probe has been a challenging research topic. Herein, we developed a novel near-infrared (NIR) fluorescent probe based on tailored Hepatitis B Core virus-like protein (HBc VLP) and presented the preclinical imaging-guided surgery.

METHODS

The RGD-HBc₁₆₀ VLP was synthesized by genetic engineering followed encapsulation of ICG via disassembly-reassembly. The applicability of the probe was tested for cell and tissue binding capacities through cell-based plate assays, xenograft mice model, and MMTV-PyVT mammary tumor transgenic mice. Subsequently, the efficacy of RGD-HBc₁₆₀/ICG-guided surgery was evaluated in an infiltrative tumor-bearing mouse model. The protein-induced body's immune response was further assessed.

RESULTS

The prepared RGD-HBc₁₆₀/ICG showed outstanding integrin α_vβ₃ targeting ability in vitro and in vivo. After intravenous administration of probe, the fluorescence guidance facilitated more complete tumor resection and improved overall survival Of the infiltrative tumor-bearing mice. The probe also showed the excellent capability to differentiate between benign and malignant breast tissues in the mammary tumor transgenic mice. Interestingly, the ingenious tailoring of HBc VLP could not only endow its tumor-targeting ability towards integrin α_vβ₃ but also significantly reduce the humoral and cellular immune response.

CONCLUSION

The RGD-HBc₁₆₀/ICG holds promise as an effective tool to delineate tumor margin. These results have translational potential to achieve margin-negative resection and improve the stratification of patients for a potentially curative.

Activatable molecular probes for fluorescence-guided surgery, endoscopy and tissue biopsy

The real-time, dynamic optical visualization of lesions and margins ensures not only complete resection of the malignant tissues but also better preservation of the vital organs/tissues during surgical procedures. Most imaging probes with an "always-on" signal encounter high background noise due to their non-specific accumulation in normal tissues. By contrast, activatable molecular probes only "turn on" their signals upon reaction with the targeted biomolecules that are overexpressed in malignant cells, offering high target-to-background ratios with high specificity and sensitivity. This review summarizes the recent progress of activatable molecular probes in surgical imaging and diagnosis. The design principle and mechanism of activatable molecular probes are discussed, followed by specific emphasis on applications ranging from fluorescence-guided surgery to endoscopy and tissue biopsy. Finally, potential challenges and perspectives in the field of activatable molecular probe-enabled surgical imaging are discussed.

Near-infrared window II fluorescence image-guided surgery of high-grade gliomas prolongs the progression-free survival of patients

OBJECTIVE

This translational study aims to investigate the clinical benefits of indocyanine green (ICG) based near-infrared window II (NIR-II) fluorescence image-guided surgery (FGS) on high-grade glioma (HGG) patients.

METHODS

Patients were randomly assigned to receive FGS or traditional white light image-guided surgery (WLS). The detection rate of NIR-II fluorescence was observed. Complete resection rate, progression-free survival (PFS), overall survival (OS), and neurological status were compared. Tissue samples were obtained from the FGS group, with the diagnosis based on the surgeons and the fluorescence recorded for comparison of diagnostic capability. Patients with WHO grade III gliomas or glioblastomas (GBM) were analyzed separately.

RESULTS

15 GBM and 4 WHO grade III glioma patients in the FGS group and 18 GBM and 4 WHO grade III glioma patients in the WLS group were enrolled. The detection rate of NIR-II fluorescence was 100% for GBM. The complete resection rate was significantly increased by the FGS for GBM (FGS, 100% [95% CI 73.41-100] vs. WLS, 50% [95% CI 29.03-70.97], P = 0.0036). The PFS and OS of the FGS group were also significantly prolonged (Median PFS: FGS, 9.0 months vs. WLS, 7.0 months, P < 0.0001; Median OS: FGS, 19.0 months vs. WLS, 15.5 months, P = 0.0002). No recurrence was observed in WHO grade III glioma patients.

CONCLUSIONS

NIR-II FGS achieves much better complete resection rate of GBM than conventional WLS, leading to greatly improved survival of GBM patients.

SIGNIFICANCE

NIR-II FGS is a highly promising technique worthy of exploring more clinical applications.

Targeted optical fluorescence imaging: a meta-narrative review and future perspectives

Purpose

The aim of this review is to give an overview of the current status of targeted optical fluorescence imaging in the field of oncology, cardiovascular, infectious and inflammatory diseases to further promote clinical translation.

Methods

A meta-narrative approach was taken to systematically describe the relevant literature. Consecutively, each field was assigned a developmental stage regarding the clinical implementation of optical fluorescence imaging.

Results

Optical fluorescence imaging is leaning towards clinical implementation in gastrointestinal and head and neck cancers, closely followed by pulmonary, neuro, breast and gynaecological oncology. In cardiovascular and infectious disease, optical imaging is in a less advanced/proof of concept stage.

Conclusion

Targeted optical fluorescence imaging is rapidly evolving and expanding into the clinic, especially in the field of oncology. However, the imaging modality still has to overcome some major challenges before it can be part of the standard of care in the clinic, such as the provision of pivotal trial data. Intensive multidisciplinary (pre-)clinical joined forces are essential to overcome the delivery of such compelling phase III registration trial data and subsequent regulatory approval and reimbursement hurdles to advance clinical implementation of targeted optical fluorescence imaging as part of standard practice.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-021-05504-y.