Emerging Fluorescent Molecular Tracers to Guide Intra-Operative Surgical Decision-Making

Future directions for early detection of fracture related infections

Introduction

Fracture related infection (FRI) refers to pathogens infecting a fracture site and hence impeding fracture healing. It is a significant complication that carries substantial disease burden and socio-economic costs, but has had limited scientific development. Hence, this paper will review the existing strategies for early detection of FRI, in the form of serum markers, molecular diagnostics and imaging modalities, and further discuss potential future directions for improved detection of FRI.

Existing Strategies for Diagnosis of FRI

The Anti-infection Global Expert Committee (AIGEC) developed a consensus definition for FRI in 2017, which includes confirmatory and suggestive criteria for diagnosis of FRI. Existing strategies for diagnosis include clinical, laboratory, histopathological, microbiological and radiological investigations.

Future Directions for Early Detection of FRI

With increasing recognition of FRI, early detection is crucial for early treatment to be enforced. We have identified potential areas for future development in diagnostics for early detection of FRI, which are discussed in this manuscript. They include inflammatory cytokines, serum calcium levels, platelet count, improved management of histopathological and microbiological specimens, metagenomics, wound biomarkers, gut microbiota analysis, and novel imaging technologies.

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.

Molecular and functional insight into anti-EGFR nanobody: Theranostic implications for malignancies

Targeted therapy and imaging are the most popular techniques for the intervention and diagnosis of cancer. A potential therapeutic target for the treatment of cancer is the epidermal growth factor receptor (EGFR), primarily for glioblastoma, lung, and breast cancer. Over-production of ligand, transcriptional up-regulation due to autocrine/paracrine signalling, or point mutations at the genomic locus may contribute to the malfunction of EGFR in malignancies. This exploit makes use of EGFR, an established biomarker for cancer diagnostics and treatment. Despite considerable development in the last several decades in making EGFR inhibitors, they are still not free from limitations like toxicity and a short serum half-life. Nanobodies and antibodies share similar binding properties, but nanobodies have the additional advantage that they can bind to antigenic epitopes deep inside the target that conventional antibodies are unable to access. For targeted therapy, anti-EGFR nanobodies can be conjugated to various molecules such as drugs, peptides, toxins and photosensitizers. These nanobodies can be designed as novel immunoconjugates using the universal modular antibody-based platform technology (UniCAR). Furthermore, Anti-EGFR nanobodies can be expressed in neural stem cells and visualised by effective fluorescent and radioisotope labelling.

Fluorescence visualization for cancer DETECTION: EXPERIENCE and perspectives

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

The application of infrared thermography technology in flap: A perspective from bibliometric and visual analysis

The application of infrared thermography technology (IRT) in flap has become a major focus of research, as it provides a non-invasive, real-time, and quantitative approach for monitoring flap perfusion. In this regard, we conducted a comprehensive visualization and scientometric analysis to systematically summarize and discuss the current state of research in this field. We systematically reviewed publications on the application of IRT in flap procedures from 1999 to 2022, using the Web of Science Core Collection (WoSCC). Through scientometric analysis, we examined annual trends, affiliations, countries, journals, authors, and their relationships, providing insights into current hotspots and future developments in this area. We analysed 522 English studies and found a steady increase in annual publications. The United States and Germany had the highest publication rates, with Beth Israel Deaconess Medical Center and Shanghai Jiaotong University being leading institutions. Notably, Lee BT and Alex Keller emerged as influential authors in this field. Compared to existing techniques, infrared-based technology offers significant advantages for non-invasive monitoring of flap perfusion, including simplicity of operation and objective results. Future trends should focus on interdisciplinary collaborations to develop new infrared devices and achieve intelligent image processing, enabling broader application in various clinical scenarios. This bibliometric study summarizes the progress and landscape of research on 'the Application of infrared thermography technology in flap' over the past two decades, providing valuable insights and serving as a reliable reference to drive further advancements and spark researchers' interest in this field.

How to objectively evaluate the impact of image-guided surgery technologies

PURPOSE

This manuscript aims to provide a better understanding of methods and techniques with which one can better quantify the impact of image-guided surgical technologies.

METHODS

A literature review was conducted with regard to economic and technical methods of medical device evaluation in various countries. Attention was focused on applications related to image-guided interventions that have enabled procedures to be performed in a minimally invasive manner, produced superior clinical outcomes, or have become standard of care.

RESULTS

The review provides examples of successful implementations and adoption of image-guided surgical techniques, mostly in the field of neurosurgery. Failures as well as newly developed technologies still undergoing cost-efficacy analysis are discussed.

CONCLUSION

The field of image-guided surgery has evolved from solely using preoperative images to utilizing highly specific tools and software to provide more information to the interventionalist in real time. While deformations in soft tissue often preclude the use of such instruments outside of neurosurgery, recent developments in optical and radioactive guidance have enabled surgeons to better account for organ motion and provide feedback to the surgeon as tissue is cut. These technologies are currently undergoing value assessments in many countries and hold promise to improve outcomes for patients, surgeons, care teams, payors, and society in general.

The GEM-handle as convenient labeling strategy for bimodal single-domain antibody-based tracers carrying 99mTc and a near-infrared fluorescent dye for intra-operative decision-making

Intra-operative fluorescence imaging has demonstrated its ability to improve tumor lesion identification. However, the limited tissue penetration of the fluorescent signals hinders the detection of deep-lying or occult lesions. Integrating fluorescence imaging with SPECT and/or intra-operative gamma-probing synergistically combines the deep tissue penetration of gamma rays for tumor localization with the precision of fluorescence imaging for precise tumor resection. In this study, we detail the use of a genetically encoded multifunctional handle, henceforth referred to as a GEM-handle, for the development of fluorescent/radioactive bimodal single-domain antibody (sdAb)-based tracers. A sdAb that targets the urokinase plasminogen activator receptor (uPAR) was engineered to carry a GEM-handle containing a carboxy-terminal hexahistidine-tag and cysteine-tag. A two-step labeling strategy was optimized and applied to site-specifically label IRDye800CW and 99mTc to the sdAb. Bimodal labeling of the sdAbs proved straightforward and successful. 99mTc activity was however restricted to 18.5 MBq per nmol fluorescently-labeled sdAb to prevent radiobleaching of IRDye800CW without impeding SPECT/CT imaging. Subsequently, the in vivo biodistribution and tumor-targeting capacity of the bimodal tracer were evaluated in uPAR-positive tumor-bearing mice using SPECT/CT and fluorescence imaging. The bimodal sdAb showed expected renal background signals due to tracer clearance, along with slightly elevated non-specific liver signals. Four hours post-injection, both SPECT/CT and fluorescent images achieved satisfactory tumor uptake and contrast, with significantly higher values observed for the anti-uPAR bimodal sdAb compared to a control non-targeting sdAb. In conclusion, the GEM-handle is a convenient method for designing and producing bimodal sdAb-based tracers with adequate in vivo characteristics.

Rhabdomyosarcoma: Current Therapy, Challenges, and Future Approaches to Treatment Strategies

Rhabdomyosarcoma is a rare cancer arising in skeletal muscle that typically impacts children and young adults. It is a worldwide challenge in child health as treatment outcomes for metastatic and recurrent disease still pose a major concern for both basic and clinical scientists. The treatment strategies for rhabdomyosarcoma include multi-agent chemotherapies after surgical resection with or without ionization radiotherapy. In this comprehensive review, we first provide a detailed clinical understanding of rhabdomyosarcoma including its classification and subtypes, diagnosis, and treatment strategies. Later, we focus on chemotherapy strategies for this childhood sarcoma and discuss the impact of three mechanisms that are involved in the chemotherapy response including apoptosis, macro-autophagy, and the unfolded protein response. Finally, we discuss in vivo mouse and zebrafish models and in vitro three-dimensional bioengineering models of rhabdomyosarcoma to screen future therapeutic approaches and promote muscle regeneration.

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.

Improving precision surgery: A review of current intraoperative nerve tissue fluorescence imaging

Iatrogenic nerve injury represents one of the most feared surgical complications and remains a major morbidity across many surgical specialties. Currently, no clinically approved technique can directly enhance intraoperative nerve visualization, where intraoperative nerve identification continues to challenge even experienced surgeons. Fluorescence-guided surgery (FGS) has been successfully integrated into clinical medicine to improve safety and efficacy in the surgical arena. A number of tissue- and disease-specific contrast agents are in the clinical translation pipeline for future FGS integration. Within this context, a diverse repertoire of fluorescent tracers have been developed to improve surgeons' intraoperative vision. This review aims to convey the recent developments for nerve-specific FGS and its potential for clinical translation.

Application of near-infrared fluorescence imaging in theranostics of gastrointestinal tumors

Gastrointestinal cancers have become an important cause of cancer-related death in humans. Improving the early diagnosis rate of gastrointestinal tumors and improving the effect of surgical treatment can significantly improve the survival rate of patients. The conventional diagnostic method is high-definition white-light endoscopy, which often leads to missed diagnosis. For surgical treatment, intraoperative tumor localization and post-operative anastomotic state evaluation play important roles in the effect of surgical treatment. As a new imaging method, near-infrared fluorescence imaging (NIRFI) has its unique advantages in the diagnosis and auxiliary surgical treatment of gastrointestinal tumors due to its high sensitivity and the ability to image deep tissues. In this review, we focus on the latest advances of NIRFI technology applied in early diagnosis of gastrointestinal tumors, identification of tumor margins, identification of lymph nodes, and assessment of anastomotic leakage. In addition, we summarize the advances of NIRFI systems such as macro imaging and micro imaging systems, and also clearly describe the application process of NIRFI from system to clinical application, and look into the prospect of NIRFI applied in the theranostics of gastrointestinal tumors.

Synthesis and Biological Evaluation of New Fluorescent Probe BPN-01: A Model Molecule for Fluorescence Image-guided Surgery

Fluorescence image-guided surgery (FIGS) can serve as a tool to achieve successful resection of tumour tissues during surgery, serving as a surgical navigator for surgeons. FIGS relies on the use of fluorescent molecules that can specifically interact with cancer cells. In this work, we developed a new model of fluorescent probe based on benzothiazole-phenylamide moiety featuring the visible fluorophore nitrobenzoxadiazole (NBD), namely BPN-01. This compound was designed and synthesised for potential applications in the tissue biopsy examination and ex-vivo imaging during FIGS of solid cancers. The probe BPN-01 exhibited favourable spectroscopic properties, particularly in nonpolar and alkaline solvents. Moreover, in vitro fluorescence imaging revealed that the probe appeared to recognise and be internalised in the prostate (DU-145) and melanoma (B16-F10) cancer cells, but not in the normal cells (myoblast C2C12). The cytotoxicity studies revealed that probe BPN-01 was not toxic to the B16 cells, suggesting excellent biocompatibility. Furthermore, the computational analysis showed that the calculated binding affinity of the probe to both translocator protein 18 kDa (TSPO) and human epidermal growth factor receptor 2 (HER2) was considerably high. Hence, probe BPN-01 displays promising properties and may be valuable for visualising cancer cells in vitro. Furthermore, ligand 5 can potentially be labelled with NIR fluorophore and radionuclide, and serves as a dual imaging agent for in vivo applications.

Advances in optical molecular imaging for neural visualization

Iatrogenic nerve injury is a significant complication in surgery, which can negatively impact patients' quality of life. Currently, the main clinical neuroimaging methods, such as computed tomography, magnetic resonance imaging, and high-resolution ultrasonography, do not offer precise real-time positioning images for doctors during surgery. The clinical application of optical molecular imaging technology has led to the emergence of new concepts such as optical molecular imaging surgery, targeted surgery, and molecular-guided surgery. These advancements have made it possible to directly visualize surgical target areas, thereby providing a novel method for real-time identification of nerves during surgery planning. Unlike traditional white light imaging, optical molecular imaging technology enables precise positioning and identifies the cation of intraoperative nerves through the presentation of color images. Although a large number of experiments and data support its development, there are few reports on its actual clinical application. This paper summarizes the research results of optical molecular imaging technology and its ability to realize neural visualization. Additionally, it discusses the challenges neural visualization recognition faces and future development opportunities.

Intraoperative Imaging in Hepatopancreatobiliary Surgery

Hepatopancreatobiliary surgery belongs to one of the most complex fields of general surgery. An intricate and vital anatomy is accompanied by difficult distinctions of tumors from fibrosis and inflammation; the identification of precise tumor margins; or small, even disappearing, lesions on currently available imaging. The routine implementation of ultrasound use shifted the possibilities in the operating room, yet more precision is necessary to achieve negative resection margins. Modalities utilizing fluorescent-compatible dyes have proven their role in hepatopancreatobiliary surgery, although this is not yet a routine practice, as there are many limitations. Modalities, such as photoacoustic imaging or 3D holograms, are emerging but are mostly limited to preclinical settings. There is a need to identify and develop an ideal contrast agent capable of differentiating between malignant and benign tissue and to report on the prognostic benefits of implemented intraoperative imaging in order to navigate clinical translation. This review focuses on existing and developing imaging modalities for intraoperative use, tailored to the needs of hepatopancreatobiliary cancers. We will also cover the application of these imaging techniques to theranostics to achieve combined diagnostic and therapeutic potential.

Targeted Bioluminescent Imaging of Pancreatic Ductal Adenocarcinoma Using Nanocarrier-Complexed EGFR-Binding Affibody-Gaussia Luciferase Fusion Protein

In vivo imaging has enabled impressive advances in biological research, both preclinical and clinical, and researchers have an arsenal of imaging methods available. Bioluminescence imaging is an advantageous method for in vivo studies that allows for the simple acquisition of images with low background signals. Researchers have increasingly been looking for ways to improve bioluminescent imaging for in vivo applications, which we sought to achieve by developing a bioluminescent probe that could specifically target cells of interest. We chose pancreatic ductal adenocarcinoma (PDAC) as the disease model because it is the most common type of pancreatic cancer and has an extremely low survival rate. We targeted the epidermal growth factor receptor (EGFR), which is frequently overexpressed in pancreatic cancer cells, using an EGFR-specific affibody to selectively identify PDAC cells and delivered a Gaussia luciferase (GLuc) bioluminescent protein for imaging by engineering a fusion protein with both the affibody and the bioluminescent protein. This fusion protein was then complexed with a G5-PAMAM dendrimer nanocarrier. The dendrimer was used to improve the protein stability in vivo and increase signal strength. Our targeted bioluminescent complex had an enhanced uptake into PDAC cells in vitro and localized to PDAC tumors in vivo in pancreatic cancer xenograft mice. The bioluminescent complexes could delineate the tumor shape, identify multiple masses, and locate metastases. Through this work, an EGFR-targeted bioluminescent-dendrimer complex enabled the straightforward identification and imaging of pancreatic cancer cells in vivo in preclinical models. This argues for the targeted nanocarrier-mediated delivery of bioluminescent proteins as a way to improve in vivo bioluminescent imaging.

Fluorescent imaging using novel conjugated polymeric nanoparticles-affimer probes in complex in vitro models of colorectal cancer

We developed a carcinoembryonic antigen (CEA) conjugated polymer nanoparticle (CPN510-CEA-Af) probe to target CEA-expressing CRC cells in vitro. Its efficacy was evaluated in 2D and 3D cultures of LS174T, LoVo, and HT29 CRC cell lines. CPN510-CEA-Af produced greater fluorescent signal intensity than unconjugated particles in both 2D cells and 3D spheriods, indicating its potential as a probe for image-guided colorectal cancer surgery.

Biotinylated Fluorescent Polymeric Nanoparticles for Enhanced Immunostaining

The performance of fluorescence immunostaining is physically limited by the brightness of organic dyes, whereas fluorescence labeling with multiple dyes per antibody can lead to dye self-quenching. The present work reports a methodology of antibody labeling by biotinylated zwitterionic dye-loaded polymeric nanoparticles (NPs). A rationally designed hydrophobic polymer, poly(ethyl methacrylate) bearing charged, zwitterionic and biotin groups (PEMA-ZI-biotin), enables preparation of small (14 nm) and bright fluorescent biotinylated NPs loaded with large quantities of cationic rhodamine dye with bulky hydrophobic counterion (fluorinated tetraphenylborate). The biotin exposure at the particle surface is confirmed by Förster resonance energy transfer with dye-streptavidin conjugate. Single-particle microscopy validates specific binding to biotinylated surfaces, with particle brightness 21-fold higher than quantum dot-585 (QD-585) at 550 nm excitation. The nanoimmunostaining method, which couples biotinylated antibody (cetuximab) with bright biotinylated zwitterionic NPs through streptavidin, significantly improves fluorescence imaging of target epidermal growth factor receptors (EGFR) on the cell surface compared to a dye-based labeling. Importantly, cetuximab labeled with PEMA-ZI-biotin NPs can differentiate cells with distinct expression levels of EGFR cancer marker. The developed nanoprobes can greatly amplify the signal from labeled antibodies, and thus become a useful tool in the high-sensitivity detection of disease biomarkers.

Comparison of Five Near-Infrared Fluorescent Folate Conjugates in an Ovarian Cancer Model

PURPOSE

Fluorescence imaging (FLI) using targeted near-infrared (NIR) conjugates aids the detection of tumour lesions pre- and intraoperatively. The optimisation of tumour visualisation and contrast is essential and can be achieved through high tumour-specificity and low background signal. However, the choice of fluorophore is recognised to alter biodistribution and clearance of conjugates and is therefore a determining factor in the specificity of target binding. Although ZW800-1, IRDye® 800CW and ICG are the most commonly employed NIR fluorophores in clinical settings, the fluorophore with optimal in vivo characteristics has yet to be determined. Therefore, we aimed to characterise the impact the choice of fluorophore has on the biodistribution, specificity and contrast, by comparing five different NIR fluorophores conjugated to folate, in an ovarian cancer model.

PROCEDURES

ZW800-1, ZW800-1 Forte, IRDye® 800CW, ICG-OSu and an in-house synthesised Cy7 derivative were conjugated to folate through an ethylenediamine linker resulting in conjugates 1-5, respectively. The optical properties of all conjugates were determined by spectroscopy, the specificity was assessed in vitro by flow cytometry and FLI, and the biodistribution was studied in vivo and ex vivo in a subcutaneous Skov-3 ovarian cancer model.

RESULTS

We demonstrated time- and receptor-dependent binding of folate conjugates in vitro and in vivo. Healthy tissue clearance characteristics and tumour-specific signal varied between conjugates 1-5. ZW800-1 Forte (2) revealed the highest contrast in folate receptor alpha (FRα)-positive xenografts and showed statistically significant target specificity. While conjugates 1, 2 and 3 are renally cleared, hepatobiliary excretion and no or very low accumulation in tumours was observed for 4 and 5.

CONCLUSIONS

The choice of fluorophore has a significant impact on the biodistribution and tumour contrast. ZW800-1 Forte (2) exhibited the best properties of those tested, with significant specific fluorescence signal.

Comparison of Near-Infrared Imaging Agents Targeting the PTPmu Tumor Biomarker

PURPOSE

Maximal, safe resection of solid tumors is considered a critical first step in successful cancer treatment. The advent of fluorescence image-guided surgery (FIGS) using non-specific agents has improved patient outcomes, particularly in the case of glioblastoma. Molecularly targeted agents that recognize specific tumor biomarkers have the potential to augment these gains. Identification of the optimal combination of targeting moiety and fluorophore is needed prior to initiating clinical trials.

PROCEDURES

A 20-amino acid peptide (SBK2) recognizing the receptor protein-tyrosine phosphatase mu (PTPmu)-derived tumor-specific biomarker, with or without a linker, was conjugated to three different near-infrared fluorophores: indocyanine green (ICG), IRDye® 800CW, and Tide Fluor™ 8WS. The in vivo specificity, time course, and biodistribution were evaluated for each using mice with heterotopic human glioma tumors that express the PTPmu biomarker to identify component combinations with optimal properties for FIGS.

RESULTS

SBK2 conjugated to ICG demonstrated excellent specificity for gliomas in heterotopic tumors. SBK2-ICG showed significantly higher in vivo tumor labeling compared to the Scram-ICG control from 10 min to 24 h, p < 0.01 at all timepoints, following injection, as well as a significantly higher ex vivo tumor signal at 24 h, p < 0.001. Inserting a six-amino acid linker between the targeting peptide and ICG increased the clearance rate and resulted in significantly higher in vivo tumor signal relative to its linker-containing Scrambled control from 10 min to 8 h, p < 0.05 at all timepoints, after dosing. Agents made with the more hydrophilic IRDye® 800CW and Tide Fluor™ 8WS showed no specific tumor labeling relative to the controls. The IRDye 800CW-conjugated agents cleared within 1 h, while the non-specific fluorescent tumor signal generated by the Tide Fluor 8WS-conjugated agents persists beyond 24 h.

CONCLUSIONS

The SBK2 PTPmu-targeting peptide conjugated to ICG specifically labels heterotopic human gliomas grown in mice between 10 min and 24 h following injection. Similar molecules constructed with more hydrophilic dyes demonstrated no specificity. These studies present a promising candidate for use in FIGS of PTPmu biomarker-expressing tumors.

Diagnostic and therapeutic potential of protease inhibition

Proteases are enzymes that hydrolyze peptide bonds in proteins and peptides; thus, they control virtually all biological processes. Our understanding of protease function has advanced considerably from nonselective digestive enzymes to highly specialized molecular scissors that orchestrate complex signaling networks through a limited proteolysis. The catalytic activity of proteases is tightly regulated at several levels, ranging from gene expression through trafficking and maturation to posttranslational modifications. However, when this delicate balance is disturbed, many diseases develop, including cancer, inflammatory disorders, diabetes, and neurodegenerative diseases. This new understanding of the role of proteases in pathologic physiology indicates that these enzymes represent excellent molecular targets for the development of therapeutic inhibitors, as well as for the design of chemical probes to visualize their redundant activity. Recently, numerous platform technologies have been developed to identify and optimize protease substrates and inhibitors, which were further used as lead structures for the development of chemical probes and therapeutic drugs. Due to this considerable success, the clinical potential of proteases in therapeutics and diagnostics is rapidly growing and is still not completely explored. Therefore, small molecules that can selectively target aberrant protease activity are emerging in diseases cells. In this review, we describe modern trends in the design of protease drugs as well as small molecule activity-based probes to visualize selected proteases in clinical settings.

Multimodal imaging needle combining optical coherence tomography and fluorescence for imaging of live breast cancer cells labeled with a fluorescent analog of tamoxifen

SIGNIFICANCE

Imaging needles consist of highly miniaturized focusing optics encased within a hypodermic needle. The needles may be inserted tens of millimeters into tissue and have the potential to visualize diseased cells well beyond the penetration depth of optical techniques applied externally. Multimodal imaging needles acquire multiple types of optical signals to differentiate cell types. However, their use has not previously been demonstrated with live cells.

AIM

We demonstrate the ability of a multimodal imaging needle to differentiate cell types through simultaneous optical coherence tomography (OCT) and fluorescence imaging.

APPROACH

We characterize the performance of a multimodal imaging needle. This is paired with a fluorescent analog of the therapeutic drug, tamoxifen, which enables cell-specific fluorescent labeling of estrogen receptor-positive (ER+) breast cancer cells. We perform simultaneous OCT and fluorescence in situ imaging on MCF-7 ER+ breast cancer cells and MDA-MB-231 ER- cells. Images are compared against unlabeled control samples and correlated with standard confocal microscopy images.

RESULTS

We establish the feasibility of imaging live cells with these miniaturized imaging probes by showing clear differentiation between cancerous cells.

CONCLUSIONS

Imaging needles have the potential to aid in the detection of specific cancer cells within solid tissue.

The Use of Indocyanine Green (ICG) and Near-Infrared (NIR) Fluorescence-Guided Imaging in Gastric Cancer Surgery: A Narrative Review

Near-infrared fluorescence imaging with indocyanine green is an emerging technology gaining clinical relevance in the field of oncosurgery. In recent decades, it has also been applied in gastric cancer surgery, spreading among surgeons thanks to the diffusion of minimally invasive approaches and the related development of new optic tools. Its most relevant uses in gastric cancer surgery are sentinel node navigation surgery, lymph node mapping during lymphadenectomy, assessment of vascular anatomy, and assessment of anastomotic perfusion. There is still debate regarding the most effective application, but with relatively no collateral effects and without compromising the operative time, indocyanine green fluorescence imaging carved out a role for itself in gastric resections. This review aims to summarize the current indications and evidence for the use of this tool, including the relevant practical details such as dosages and times of administration.

Emerging applications of nanobodies in cancer therapy

Cancer is a heterogeneous disease, requiring treatment tailored to the unique phenotype of the patient's tumor. Monoclonal antibodies (mAbs) and variants thereof have enabled targeted therapies to selectively target cancer cells. Cancer cell-specific mAbs have been used for image-guided surgery and targeted delivery of radionuclides or toxic agents, improving classical treatment strategies. Cancer cell-specific mAbs can further inhibit tumor cell growth or can stimulate immune-mediated destruction of cancer cells, a feature that has also been achieved through mAb-mediated manipulation of immune cells and pathways. Drawbacks of mAbs and their variants, together with the discovery of camelid heavy chain-only antibodies and the many advantageous features of their variable domains, referred to as V_HHs, single domain antibodies or nanobodies (Nbs), resulted in the exploration of Nbs as an alternative targeting moiety. We therefore review the state-of-the-art as well as novel exploitation strategies of Nbs for targeted cancer therapy.

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.

CD47-targeted optical molecular imaging and near-infrared photoimmunotherapy in the detection and treatment of bladder cancer

Transurethral resection of bladder tumor (TURBT) followed by intravesical therapy remains the most effective strategy for the management of non-muscle-invasive bladder cancer worldwide. TURBT has two purposes: to remove all visible tumors and to obtain tumor specimens for histopathological analysis. However, the detection of flat and small malignant lesions under white-light cystoscopy is extremely challenging, and residual lesions are still the main reason for the high recurrence rate of bladder cancer. We hypothesized that visual enhancement of malignant lesions using targeted optical molecular imaging could potentially highlight residual tumors in the bladder during surgery, and near-infrared photoimmunotherapy (NIR-PIT) could kill exfoliated cancer cells and residual tumors. A mouse model of complete or partial bladder tumor resection was established under the guidance of optical molecular imaging mediated by indocyanine green and anti-CD47-Alexa Fluor 790, respectively. Once the tumor recurred, mouse model received repeated CD47-targeted NIR-PIT. After complete resection, there was no tumor recurrence. Furthermore, the growth rate of recurrent tumor decreased significantly after repeated NIR-PIT. Therefore, CD47-targeted optical molecular imaging can potentially assist urologists to detect and remove all tumors, and repeated NIR-PIT shows the potential to reduce tumor recurrence rates and inhibit the growth of recurrent tumor.

Refined immunoRNases for the efficient targeting and selective killing of tumour cells: A novel strategy

In order to overcome limitations of conventional cancer therapy methods, immunotoxins with the capability of target-specific action have been designed and evaluated pre-clinically, and some of them are in clinical studies. Targeting cancer cells via antibodies specific for tumour-associated surface proteins is a new biomedical approach that could provide the selectivity that is lacking in conventional cancer therapy methods such as radiotherapy and chemotherapy. A successful example of an approved immunotoxin is represented by immunoRNases. ImmunoRNases are fusion proteins in which the toxin has been replaced by a ribonuclease. Conjugation of RNase molecule to monoclonal antibody or antibody fragment was shown to enhance specific cell-killing by several orders of magnitude, both in vitro and in animal models. There are several RNases obtained from different mammalian cells that are expected to be less immunogenic and systemically toxic. In fact, RNases are pro-toxins which become toxic only upon their internalization in target cells mediated by the antibody moiety. The structure and large size of the antibody molecules assembled with the immunoRNases have always been a challenge in the application of immunoRNases as an antitoxin. To overcome this obstacle, we have offered a new strategy for the application of immunoRNases as a promising approach for upgrading immunoRNAses with maximum affinity and high stability in the cell, which can ultimately act as an effective large-scale cancer treatment. In this review, we introduce the optimized antibody-like molecules with small size, approximately 10 kD, which are presumed to significantly enhance RNase activity and be a suitable agent with the potential for anti-cancer functionality. In addition, we also discuss new molecular entities such as monobody, anticalin, nonobody and affilin as refined versions in the development of immunoRNases. These small molecules express their functionality with the suitable small size as well as with low immunogenicity in the cell, as a part of immunoRNases.

Fluorescence Molecular Targeting of Colon Cancer to Visualize the Invisible

Colorectal cancer (CRC) is a common cause of cancer and cancer-related death. Surgery is the only curative modality. Fluorescence-enhanced visualization of CRC with targeted fluorescent probes that can delineate boundaries and target tumor-specific biomarkers can increase rates of curative resection. Approaches to enhancing visualization of the tumor-to-normal tissue interface are active areas of investigation. Nonspecific dyes are the most-used approach, but tumor-specific targeting agents are progressing in clinical trials. The present narrative review describes the principles of fluorescence targeting of CRC for diagnosis and fluorescence-guided surgery with molecular biomarkers for preclinical or clinical evaluation.

Fundamentals and developments in fluorescence-guided cancer surgery

Fluorescence-guided surgery using tumour-targeted imaging agents has emerged over the past decade as a promising and effective method of intraoperative cancer detection. An impressive number of fluorescently labelled antibodies, peptides, particles and other molecules related to cancer hallmarks have been developed for the illumination of target lesions. New approaches are being implemented to translate these imaging agents into the clinic, although only a few have made it past early-phase clinical trials. For this translational process to succeed, target selection, imaging agents and their related detection systems and clinical implementation have to operate in perfect harmony to enable real-time intraoperative visualization that can benefit patients. Herein, we review key aspects of this imaging cascade and focus on imaging approaches and methods that have helped to shed new light onto the field of intraoperative fluorescence-guided cancer surgery with the singular goal of improving patient outcomes.

Design and Validation of Site-Specifically Labeled Single-Domain Antibody-Based Tracers for in Vivo Fluorescence Imaging and Image-Guided Surgery

Near-infrared fluorescence molecular imaging has become an established preclinical technique to investigate molecular processes in vivo and to study novel therapies. Furthermore, fluorescence molecular imaging is gaining significant interest from clinicians as an intra-operative guidance tool. This technique makes use of targeted fluorescent tracers as contrast agents that recognize specific biomarkers expressed at the site of disease. Single-domain antibodies have shown to possess excellent properties for in vivo imaging in comparison to conventional antibodies. In this chapter, we describe a method for site-specific conjugation of a near-infrared fluorophore to single-domain antibodies by exploiting cysteine-maleimide chemistry. As opposed to random conjugation, site-specific conjugation results in a homogenously labeled fluorescent tracer and avoids inference with antigen binding.

Molecular photoswitches in aqueous environments

Molecular photoswitches enable dynamic control of processes with high spatiotemporal precision, using light as external stimulus, and hence are ideal tools for different research areas spanning from chemical biology to smart materials. Photoswitches are typically organic molecules that feature extended aromatic systems to make them responsive to (visible) light. However, this renders them inherently lipophilic, while water-solubility is of crucial importance to apply photoswitchable organic molecules in biological systems, like in the rapidly emerging field of photopharmacology. Several strategies for solubilizing organic molecules in water are known, but there are not yet clear rules for applying them to photoswitchable molecules. Importantly, rendering photoswitches water-soluble has a serious impact on both their photophysical and biological properties, which must be taken into consideration when designing new systems. Altogether, these aspects pose considerable challenges for successfully applying molecular photoswitches in aqueous systems, and in particular in biologically relevant media. In this review, we focus on fully water-soluble photoswitches, such as those used in biological environments, in both in vitro and in vivo studies. We discuss the design principles and prospects for water-soluble photoswitches to inspire and enable their future applications.

Introducing Fluorescence-Guided Surgery for Pediatric Ewing, Osteo-, and Rhabdomyosarcomas: A Literature Review

Sarcomas are a rare heterogeneous group of malignant neoplasms of mesenchymal origin which represent approximately 13% of all cancers in pediatric patients. The most prevalent pediatric bone sarcomas are osteosarcoma (OS) and Ewing sarcoma (ES). Rhabdomyosarcoma (RMS) is the most frequently occurring pediatric soft tissue sarcoma. The median age of OS and ES is approximately 17 years, so this disease is also commonly seen in adults while non-pleiomorphic RMS is rare in the adult population. The mainstay of all treatment regimens is multimodal treatment containing chemotherapy, surgical resection, and sometimes (neo)adjuvant radiotherapy. A clear resection margin improves both local control and overall survival and should be the goal during surgery with a curative intent. Real-time intraoperative fluorescence-guided imaging could facilitate complete resections by visualizing tumor tissue during surgery. This review evaluates whether non-targeted and targeted fluorescence-guided surgery (FGS) could be beneficial for pediatric OS, ES, and RMS patients. Necessities for clinical implementation, current literature, and the positive as well as negative aspects of non-targeted FGS using the NIR dye Indocyanine Green (ICG) were evaluated. In addition, we provide an overview of targets that could potentially be used for FGS in OS, ES, and RMS. Then, due to the time- and cost-efficient translational perspective, we elaborate on the use of antibody-based tracers as well as their disadvantages and alternatives. Finally, we conclude with recommendations for the experiments needed before FGS can be implemented for pediatric OS, ES, and RMS patients.

Strategy of De Novo Design toward First-In-Class Imaging Agents for Simultaneously Differentiating Glioma Boundary and Grades

The extent of resection and tumor grade are two predominant prognostic factors for glioma. Fluorescent imaging is promising to facilitate accurate resection and simultaneous tumor grading. However, no probe fulfilling this task has been reported. Herein, we proposed a strategy of de novo design toward first-in-class fluorescent probes for simultaneously differentiating glioma boundary and grades. By bioinformatics analysis in combination with experimental validation, platelet-derived growth factor receptor β (PDGFRβ) was revealed as a promising biomarker for glioma imaging and grading. Then, fluorogenic probe PDGFP 1 was designed, guided by the structure-activity relationship study. Finally, the probe was demonstrated to stain glioma cells and tissues in the mice orthotopic glioma model with high selectivity over normal brain cells or tissues. Meanwhile, ex vivo experiments using patient-derived samples indicated that the fluorescence was significantly positively correlated with the tumor grades. This result highlighted the feasibility of the three-step de novo probe design strategy and suggested PDGFP 1 as a promising probe for simultaneously differentiating glioma boundary and grades, showing prospects of clinical translation.

Detecting and Monitoring Hydrogels with Medical Imaging

Hydrogels, water-swollen polymer networks, are being applied to numerous biomedical applications, such as drug delivery and tissue engineering, due to their potential tunable rheologic properties, injectability into tissues, and encapsulation and release of therapeutics. Despite their promise, it is challenging to assess their properties in vivo and crucial information such as hydrogel retention at the site of administration and in situ degradation kinetics are often lacking. To address this, technologies to evaluate and track hydrogels in vivo with various imaging techniques have been developed in recent years, including hydrogels functionalized with contrast generating material that can be imaged with methods such as X-ray computed tomography (CT), magnetic resonance imaging (MRI), optical imaging, and nuclear imaging systems. In this review, we will discuss emerging approaches to label hydrogels for imaging, review the advantages and limitations of these imaging techniques, and highlight examples where such techniques have been implemented in biomedical applications.

Targeting the Urokinase-Type Plasminogen Activator Receptor (uPAR) in Human Diseases With a View to Non-invasive Imaging and Therapeutic Intervention

The interaction between the serine protease urokinase-type plasminogen activator (uPA) and its glycolipid-anchored receptor (uPAR) focalizes plasminogen activation to cell surfaces, thereby regulating extravascular fibrinolysis, cell adhesion, and migration. uPAR belongs to the Ly6/uPAR (LU) gene superfamily and the high-affinity binding site for uPA is assembled by a dynamic association of its three consecutive LU domains. In most human solid cancers, uPAR is expressed at the invasive areas of the tumor-stromal microenvironment. High levels of uPAR in resected tumors or shed to the plasma of cancer patients are robustly associated with poor prognosis and increased risk of relapse and metastasis. Over the years, a plethora of different strategies to inhibit uPA and uPAR function have been designed and investigated in vitro and in vivo in mouse models, but so far none have been implemented in the clinics. In recent years, uPAR-targeting with the intent of cytotoxic eradication of uPAR-expressing cells have nonetheless gained increasing momentum. Another avenue that is currently being explored is non-invasive imaging with specific uPAR-targeted reporter-molecules containing positron emitting radionuclides or near-infrared (NIR) florescence probes with the overarching aim of being able to: (i) localize disease dissemination using positron emission tomography (PET) and (ii) assist fluorescence guided surgery using optical imaging. In this review, we will discuss these advancements with special emphasis on applications using a small 9-mer peptide antagonist that targets uPAR with high affinity.

A first-in-human study of BLZ-100 (tozuleristide) demonstrates tolerability and safety in skin cancer patients

BLZ-100 (tozuleristide) is an intraoperative fluorescent imaging agent that selectively detects malignant tissue and can be used in real time to guide tumor resection. The purpose of this study was to assess the safety, tolerability, and pharmacokinetics of BLZ-100 and to explore the pharmacodynamics of fluorescence imaging of skin tumors. In this first-in-human study, BLZ-100 was administered intravenously to 21 adult patients 2 days before excising known or suspected skin cancers. Doses were 1, 3, 6, 12, and 18 mg, with 3-6 patients/cohort. Fluorescence imaging was conducted before and up to 48 h after dosing. BLZ-100 was well tolerated. There were no serious adverse events, deaths, or discontinuations due to adverse events, and no maximum tolerated dose (MTD) was identified. Headache (n = 2) and nausea (n = 2) were the only BLZ-100 treatment-related adverse events reported for >1 patient. Median time to maximal serum concentration was <0.5 h. Exposure based on maximal serum concentrations increased in a greater than dose-proportional manner. For intermediate dose-levels (3-12 mg), 4 of 5 basal cell carcinomas and 4 of 4 melanomas were considered positive for BLZ-100 fluorescence. BLZ-100 was well tolerated at all dose levels tested and these results support further clinical testing of this imaging agent in surgical oncology settings. Clinicaltrials.gov: NCT02097875.

Evaluation of Two Optical Probes for Imaging the Integrin αvβ6- In Vitro and In Vivo in Tumor-Bearing Mice

PURPOSE

The purpose of this study was to develop and evaluate two α_vβ₆-targeted fluorescent imaging agents. The integrin subtype α_vβ₆ is significantly upregulated in a wide range of epithelial derived cancers, plays a key role in invasion and metastasis, and expression is often located at the invasive edge of tumors. α_vβ₆-targeted fluorescent imaging agents have the potential to guide surgical resection leading to improved patient outcomes. Both imaging agents were based on the bi-PEGylated peptide NH₂-PEG₂₈-A20FMDV2-K16R-PEG₂₈ (1), a peptide that has high affinity and selectivity for the integrin α_vβ₆: (a) 5-FAM-X-PEG₂₈-A20FMDV2-K16R-PEG₂₈ (2), and (b) IRDye800-PEG₂₈-A20FMDV2-K16R-PEG₂₈ (3).

PROCEDURES

Peptides were synthesized using solid-phase peptide synthesis and standard Fmoc chemistry. Affinity for α_vβ₆ was evaluated by ELISA. In vitro binding, internalization, and localization of 2 was monitored using confocal microscopy in DX3puroβ₆ (α_vβ₆+) and DX3puro (α_vβ₆-) cells. The in vivo imaging and ex vivo biodistribution of 3 was evaluated in three preclinical mouse models, DX3puroβ₆/DX3puro and BxPC-3 (α_vβ₆+) tumor xenografts and a BxPC-3 orthotopic pancreatic tumor model.

RESULTS

Peptides were obtained in > 99% purity. IC₅₀ values were 28 nM (2) and 39 nM (3). Rapid α_vβ₆-selective binding and internalization of 2 was observed. Fluorescent intensity (FLI) measurements extracted from the in vivo images and ex vivo biodistribution confirmed uptake and retention of 3 in the α_vβ₆ positive subcutaneous and orthotopic tumors, with negligible uptake in the α_vβ₆-negative tumor. Blocking studies with a known α_vβ₆-targeting peptide demonstrated α_vβ₆-specific binding of 3.

CONCLUSION

Two fluorescence imaging agents were developed. The α_vβ₆-specific uptake, internalization, and endosomal localization of the fluorescence agent 2 demonstrates potential for targeted therapy. The selective uptake and retention of 3 in the α_vβ₆-positive tumors enabled clear delineation of the tumors and surgical resection indicating 3 has the potential to be utilized during image-guided surgery.

Molecular Imaging, How Close to Clinical Precision Medicine in Lung, Brain, Prostate and Breast Cancers

Precision medicine is playing a pivotal role in strategies of cancer therapy. Unlike conventional one-size-fits-all chemotherapy or radiotherapy modalities, precision medicine could customize an individual treatment plan for cancer patients to acquire superior efficacy, while minimizing side effects. Precision medicine in cancer therapy relies on precise and timely tumor biological information. Traditional tissue biopsies, however, are often inadequate in meeting this requirement due to cancer heterogeneity, poor tolerance, and invasiveness. Molecular imaging could detect tumor biology characterization in a noninvasive and visual manner, and provide information about therapeutic targets, treatment response, and pharmacodynamic evaluation. This summates to significant value in guiding cancer precision medicine in aspects of patient screening, treatment monitoring, and estimating prognoses. Although growing clinical evidences support the further application of molecular imaging in precision medicine of cancer, some challenges remain. In this review, we briefly summarize and discuss representative clinical trials of molecular imaging in improving precision medicine of cancer patients, aiming to provide useful references for facilitating further clinical translation of molecular imaging to precision medicine of cancers.

Current Advances in Photoactive Agents for Cancer Imaging and Therapy

Photoactive agents are promising complements for both early diagnosis and targeted treatment of cancer. The dual combination of diagnostics and therapeutics is known as theranostics. Photoactive theranostic agents are activated by a specific wavelength of light and emit another wavelength, which can be detected for imaging tumors, used to generate reactive oxygen species for ablating tumors, or both. Photodynamic therapy (PDT) combines photosensitizer (PS) accumulation and site-directed light irradiation for simultaneous imaging diagnostics and spatially targeted therapy. Although utilized since the early 1900s, advances in the fields of cancer biology, materials science, and nanomedicine have expanded photoactive agents to modern medical treatments. In this review we summarize the origins of PDT and the subsequent generations of PSs and analyze seminal research contributions that have provided insight into rational PS design, such as photophysics, modes of cell death, tumor-targeting mechanisms, and light dosing regimens. We highlight optimizable parameters that, with further exploration, can expand clinical applications of photoactive agents to revolutionize cancer diagnostics and treatment.

Design, Synthesis, and Utility of Defined Molecular Scaffolds

A growing theme in chemistry is the joining of multiple organic molecular building blocks to create functional molecules. Diverse derivatizable structures—here termed “scaffolds” comprised of “hubs”—provide the foundation for systematic covalent organization of a rich variety of building blocks. This review encompasses 30 tri- or tetra-armed molecular hubs (e.g., triazine, lysine, arenes, dyes) that are used directly or in combination to give linear, cyclic, or branched scaffolds. Each scaffold is categorized by graph theory into one of 31 trees to express the molecular connectivity and overall architecture. Rational chemistry with exacting numbers of derivatizable sites is emphasized. The incorporation of water-solubilization motifs, robust or self-immolative linkers, enzymatically cleavable groups and functional appendages affords immense (and often late-stage) diversification of the scaffolds. Altogether, 107 target molecules are reviewed along with 19 syntheses to illustrate the distinctive chemistries for creating and derivatizing scaffolds. The review covers the history of the field up through 2020, briefly touching on statistically derivatized carriers employed in immunology as counterpoints to the rationally assembled and derivatized scaffolds here, although most citations are from the past two decades. The scaffolds are used widely in fields ranging from pure chemistry to artificial photosynthesis and biomedical sciences.

Metal-Based G-Quadruplex Binders for Cancer Theranostics

The ability of fluorescent small molecules, such as metal complexes, to selectively recognize G-quadruplex (G4) structures has opened a route to develop new probes for the visualization of these DNA structures in cells. The main goal of this review is to update the most recent research efforts towards the development of novel cancer theranostic agents using this type of metal-based probes that specifically recognize G4 structures. This encompassed a comprehensive overview of the most significant progress in the field, namely based on complexes with Cu, Pt, and Ru that are among the most studied metals to obtain this class of molecules. It is also discussed the potential interest of obtaining G4-binders with medical radiometals (e.g., 99mTc, 111In, 64Cu, 195mPt) suitable for diagnostic and/or therapeutic applications within nuclear medicine modalities, in order to enable their theranostic potential.

Antibody-Based Targeted Interventions for the Diagnosis and Treatment of Skin Cancers

BACKGROUND

Cutaneous malignancies most commonly arise from skin epidermal cells. These cancers may rapidly progress from benign to a metastatic phase. Surgical resection represents the gold standard therapeutic treatment of non-metastatic skin cancer while chemo- and/or radiotherapy are often used against metastatic tumors. However, these therapeutic treatments are limited by the development of resistance and toxic side effects, resulting from the passive accumulation of cytotoxic drugs within healthy cells.

OBJECTIVE

This review aims to elucidate how the use of monoclonal Antibodies (mAbs) targeting specific Tumor Associated Antigens (TAAs) is paving the way to improved treatment. These mAbs are used as therapeutic or diagnostic carriers that can specifically deliver cytotoxic molecules, fluorophores or radiolabels to cancer cells that overexpress specific target antigens.

RESULTS

mAbs raised against TAAs are widely in use for e.g. differential diagnosis, prognosis and therapy of skin cancers. Antibody-Drug Conjugates (ADCs) particularly show remarkable potential. The safest ADCs reported to date use non-toxic photo-activatable Photosensitizers (PSs), allowing targeted Photodynamic Therapy (PDT) resulting in targeted delivery of PS into cancer cells and selective killing after light activation without harming the normal cell population. The use of near-infrared-emitting PSs enables both diagnostic and therapeutic applications upon light activation at the specific wavelengths.

CONCLUSION

Antibody-based approaches are presenting an array of opportunities to complement and improve current methods employed for skin cancer diagnosis and treatment.

Translation of c-Met Targeted Image-Guided Surgery Solutions in Oral Cavity Cancer-Initial Proof of Concept Data

Simple Summary

Translation of tumor-specific fluorescent tracers is crucial in the realization intraoperative of tumor identification during fluorescence-guided surgery. Ex vivo assessment of surgical specimens after topical tracer application has the potential to reveal the suitability of a potential surgical target prior to in vivo use in patients. In this study, the c-Met receptor was identified as a possible candidate for fluorescence-guided surgery in oral cavity cancer. Freshly excised tumor specimens obtained from ten patients with squamous cell carcinoma of the tongue were incubated with EMI-137 and imaged with a clinical-grade Cy5 prototype fluorescence camera. In total, 9/10 tumors were fluorescently illuminated, while non-visualization could be linked to non-superficial tumor localization. Immunohistochemistry revealed c-Met expression in all ten specimens. Tumor assessment was improved via video representation of the tumor-to-background ratio.

Abstract

Intraoperative tumor identification (extension/margins/metastases) via receptor-specific targeting is one of the ultimate promises of fluorescence-guided surgery. The translation of fluorescent tracers that enable tumor visualization forms a critical component in the realization of this approach. Ex vivo assessment of surgical specimens after topical tracer application could help provide an intermediate step between preclinical evaluation and first-in-human trials. Here, the suitability of the c-Met receptor as a potential surgical target in oral cavity cancer was explored via topical ex vivo application of the fluorescent tracer EMI-137. Freshly excised tumor specimens obtained from ten patients with squamous cell carcinoma of the tongue were incubated with EMI-137 and imaged with a clinical-grade Cy5 prototype fluorescence camera. In-house developed image processing software allowed video-rate assessment of the tumor-to-background ratio (TBR). Fluorescence imaging results were related to standard pathological evaluation and c-MET immunohistochemistry. After incubation with EMI-137, 9/10 tumors were fluorescently illuminated. Immunohistochemistry revealed c-Met expression in all ten specimens. Non-visualization could be linked to a more deeply situated lesion. Tumor assessment was improved via video representation of the TBR (median TBR: 2.5 (range 1.8–3.1)). Ex vivo evaluation of tumor specimens suggests that c-Met is a possible candidate for fluorescence-guided surgery in oral cavity cancer.

Necrosis binding of Ac-Lys0(IRDye800CW)-Tyr3-octreotate: a consequence from cyanine-labeling of small molecules

Background

There is a growing body of nuclear contrast agents that are repurposed for fluorescence-guided surgery. New contrast agents are obtained by substituting the radioactive tag with, or adding a fluorescent cyanine to the molecular structure of antibodies or peptides. This enables intra-operative fluorescent detection of cancerous tissue, leading to more complete tumor resection. However, these fluorescent cyanines can have a remarkable influence on pharmacokinetics and tumor uptake, especially when labeled to smaller targeting vectors such as peptides. Here we demonstrate the effect of cyanine-mediated dead cell-binding of Ac-Lys⁰(IRDye800CW)-Tyr³-octreotate (800CW-TATE) and how this can be used as an advantage for fluorescence-guided surgery.

Results

Binding of 800CW-TATE could be blocked with DOTA⁰-Tyr³-octreotate (DOTA-TATE) on cultured SSTR₂-positive U2OS cells and was absent in SSTR₂ negative U2OS cells. However, strong binding was observed to dead cells, which could not be blocked with DOTA-TATE and was also present in dead SSTR₂ negative cells. No SSTR₂-mediated binding was observed in frozen tumor sections, possibly due to disruption of the cells in the process of sectioning the tissue before exposure to the contrast agent. DOTA-TATE blocking resulted in an incomplete reduction of 61.5 ± 5.8% fluorescence uptake by NCI-H69-tumors in mice. Near-infrared imaging and dead cell staining on paraffin sections from resected tumors revealed that fluorescence uptake persisted in necrotic regions upon blocking with DOTA-TATE.

Conclusion

This study shows that labeling peptides with cyanines can result in dead cell binding. This does not hamper the ultimate purpose of fluorescence-guided surgery, as necrotic tissue appears in most solid tumors. Hence, the necrosis binding can increase the overall tumor uptake. Moreover, necrotic tissue should be removed as much as possible: it cannot be salvaged, causes inflammation, and is tumorigenic. However, when performing binding experiments to cells with disrupted membrane integrity, which is routinely done with nuclear probes, this dead cell-binding can resemble non-specific binding. This study will benefit the development of fluorescent contrast agents.

Supplementary information

The online version contains supplementary material available at 10.1186/s13550-021-00789-4.

Comparison of methods for separating fluorescently labelled placental extracellular vesicles from free stain

The field of extracellular vesicles (EVs) is relatively new and the methods for EV isolation and quantification are still maturing. For example, there is no consensus on how to separate free stain from labelled EVs. Here we report a comparison of the recovery of labelled EVs following separation from free stain using ultracentrifugation, diafiltration with different devices and a charged size exclusion chromatography column. Of the methods we tested, the charged size exclusion column provided the greatest recovery of labelled EVs.

En Bloc Tumor Resection, Optical Molecular Imaging, and the Potential Synergy of the Combination of the Two Techniques in Bladder Cancer

Although transurethral resection of bladder tumor is the golden standard for the treatment of non-muscle invasive bladder cancer, this surgical procedure still has some serious drawbacks. For example, piecemeal resection of tumor tissue results in exfoliated tumor cells dissemination and implantation, and fragmented tumor specimens make it difficult for pathologists to accurately assess the pathological stage and histologic grade. En bloc tumor resection follows the basic principle of oncological surgery and provides an intact tumor specimen containing detrusor muscle for pathologists to make accurate histopathological assessment. However, there is no robust clinical evidence that en bloc tumor resection is superior to conventional resection in terms of oncological outcomes. Considering the high recurrence rate, small or occult tumor lesions may be overlooked and incomplete tumor resection may occur during white light cystoscopy-assisted transurethral resection. Molecular fluorescent tracers have the ability to bind tumor cells with high sensitivity and specificity. Optical molecular imaging mediated by it can detect small or occult malignant lesions while minimizing the occurrence of false-positive results. Meanwhile, optical molecular imaging can provide dynamic and real-time image guidance in the surgical procedure, which helps urologists to accurately determine the boundary and depth of tumor invasion, so as to perform complete and high-quality transurethral tumor resection. Integrating the advantages of these two technologies, optical molecular imaging-assisted en bloc tumor resection shows the potential to improve the positive detection rate of small or occult tumor lesions and the quality of transurethral resection, resulting in high recurrence-free and progression-free survival rates.

Dive into Single, Seek Out Multiple: Probing Cancer Metastases via Single-Cell Sequencing and Imaging Techniques

Metastasis is the cause of most cancer deaths and continues to be the biggest challenge in clinical practice and laboratory investigation. The challenge is largely due to the intrinsic heterogeneity of primary and metastatic tumor populations and the complex interactions among cancer cells and cells in the tumor microenvironment. Therefore, it is important to determine the genotype and phenotype of individual cells so that the metastasis-driving events can be precisely identified, understood, and targeted in future therapies. Single-cell sequencing techniques have allowed the direct comparison of the genomic and transcriptomic changes among different stages of metastatic samples. Single-cell imaging approaches have enabled the live visualization of the heterogeneous behaviors of malignant and non-malignant cells in the tumor microenvironment. By applying these technologies, we are achieving a spatiotemporal precision understanding of cancer metastases and clinical therapeutic translations.

Recent Advances in Organelle-Targeted Fluorescent Probes

Recent advances in fluorescence imaging techniques and super-resolution microscopy have extended the applications of fluorescent probes in studying various cellular processes at the molecular level. Specifically, organelle-targeted probes have been commonly used to detect cellular metabolites and transient chemical messengers with high precision and have become invaluable tools to study biochemical pathways. Moreover, several recent studies reported various labeling strategies and novel chemical scaffolds to enhance target specificity and responsiveness. In this review, we will survey the most recent reports of organelle-targeted fluorescent probes and assess their general strategies and structural features on the basis of their target organelles. We will discuss the advantages of the currently used probes and the potential challenges in their application as well as future directions.

Spatial Organization of the Transport of Interstitial Fluid and Lymph in Rat Liver (Scanning Electron Microscopy of Injection Replicas)

Using the method of scanning electron microscopy of injection replicas, we studied the movement of a new injection mass between the blood microcirculation system, interstitial space, lymphatic system, and bile transport system in rat liver under normal conditions and 3 days after the occlusion of the common bile duct. The casts of the perisinusoidal spaces of Disse's after injection of the injection mass through the portal vein and common bile duct were obtained. Their direct transition not only in "leakages" structurally related to lymphatic capillaries in interlobular spaces, but also in perivascular spaces around the portal and hepatic veins. The flow of the injection mass through the perivascular spaces leads to the formation of peculiar "sheaths" around hepatic veins and components of the portal complex. The proposed approach allows effective visualization of the structural basis of interaction of various compartments of the fluid microcirculation in the liver under normal and pathological conditions.