Molecular imaging: current status and emerging strategies

Advances in Noninvasive Molecular Imaging Probes for Liver Fibrosis Diagnosis

Liver fibrosis is a wound-healing response to chronic liver injury, which may lead to cirrhosis and cancer. Early-stage fibrosis is reversible, and it is difficult to precisely diagnose with conventional imaging modalities such as magnetic resonance imaging, positron emission tomography, single-photon emission computed tomography, and ultrasound imaging. In contrast, probe-assisted molecular imaging offers a promising noninvasive approach to visualize early fibrosis changes in vivo, thus facilitating early diagnosis and staging liver fibrosis, and even monitoring of the treatment response. Here, the most recent progress in molecular imaging technologies for liver fibrosis is updated. We start by illustrating pathogenesis for liver fibrosis, which includes capillarization of liver sinusoidal endothelial cells, cellular and molecular processes involved in inflammation and fibrogenesis, as well as processes of collagen synthesis, oxidation, and cross-linking. Furthermore, the biological targets used in molecular imaging of liver fibrosis are summarized, which are composed of receptors on hepatic stellate cells, macrophages, and even liver collagen. Notably, the focus is on insights into the advances in imaging modalities developed for liver fibrosis diagnosis and the update in the corresponding contrast agents. In addition, challenges and opportunities for future research and clinical translation of the molecular imaging modalities and the contrast agents are pointed out. We hope that this review would serve as a guide for scientists and students who are interested in liver fibrosis imaging and treatment, and as well expedite the translation of molecular imaging technologies from bench to bedside.

Decorrelation Time Mapping as an Analysis Tool for Nanobubble-Based Contrast Enhanced Ultrasound Imaging

Nanobubbles (NBs; ~100-500 nm diameter) are preclinical ultrasound (US) contrast agents that expand applications of contrast enhanced US (CEUS). Due to their sub-micron size, high particle density, and deformable shell, NBs in pathological states of heightened vascular permeability (e.g. in tumors) extravasate, enabling applications not possible with microbubbles (~1000-10,000 nm diameter). A method that can separate intravascular versus extravascular NB signal is needed as an imaging biomarker for improved tumor detection. We present a demonstration of decorrelation time (DT) mapping for enhanced tumor NB-CEUS imaging. In vitro models validated the sensitivity of DT to agent motion. Prostate cancer mouse models validated in vivo imaging potential and sensitivity to cancerous tissue. Our findings show that DT is inversely related to NB motion, offering enhanced detail of NB dynamics in tumors, and highlighting the heterogeneity of the tumor environment. Average DT was high in tumor regions (~9 s) compared to surrounding normal tissue (~1 s) with higher sensitivity to tumor tissue compared to other mapping techniques. Molecular NB targeting to tumors further extended DT (11 s) over non-targeted NBs (6 s), demonstrating sensitivity to NB adherence. From DT mapping of in vivo NB dynamics we demonstrate the heterogeneity of tumor tissue while quantifying extravascular NB kinetics and delineating intra-tumoral vasculature. This new NB-CEUS-based biomarker can be powerful in molecular US imaging, with improved sensitivity and specificity to diseased tissue and potential for use as an estimator of vascular permeability and the enhanced permeability and retention (EPR) effect in tumors.

Effects of Surface IR783 Density on the In Vivo Behavior and Imaging Performance of Liposomes

Background: Nanoparticles conjugated with fluorescent probes have versatile applications, serving not only for targeted fluorescent imaging but also for evaluating the in vivo profiles of designed nanoparticles. However, the relationship between fluorophore density and nanoparticle behavior remains unexplored. Methods: The IR783-modified liposomes (IR783-sLip) were prepared through a modified ethanol injection and extrusion method. The cellular uptake efficiency of IR783-sLip was characterized by flow cytometry and fluorescence microscope imaging. The effects of IR783 density on liposomal in vivo behavior were investigated by pharmacokinetic studies, biodistribution studies, and in vivo imaging. The constitution of protein corona was analyzed by the Western blot assay. Results: Dense IR783 modification improved cellular uptake of liposomes in vitro but hindered their blood retention and tumor imaging performance in vivo. We found a correlation between IR783 density and protein corona absorption, particularly IgM, which significantly impacted the liposome performance. Meanwhile, we observed that increasing IR783 density did not consistently improve the effectiveness of tumor imaging. Conclusions: Increasing the density of modified IR783 on liposomes is not always beneficial for tumor near-infrared (NIR) imaging yield. It is not advisable to prematurely evaluate novel nanomaterials through fluorescence dye conjugation without carefully optimizing the density of the modifications.

Insights into the development of 99mTc-radioligands for serotonergic receptors imaging: Synthesis, labeling, In vitro, and In vivo studies

Serotonergic (5-hydroxytryptamine; 5-HT) receptors play critical roles in neurological and psychological disorders such as schizophrenia, anxiety, depression, and Alzheimer's diseases. Therefore, it is particularly important to develop novel radioligands or modify the existing ones to identify the serotonergic receptors involved in psychiatric disorders. Among the 16 subtypes of serotonergic systems, only technetium-99m based radiopharmaceuticals have been evaluated for serotonin-1A (5-HT1A), serotonin-2A (5-HT2A), 5-HT1A/7 heterodimers and serotonin receptor neurotransmitter (SERT). This review focuses on recent efforts in the design, synthesis and evaluation of 99mTc-radioligands used for single photon emission computerized tomography (SPECT) imaging of serotonergic (5-HT) receptors. Additionally, the discussion will cover aspects such as chemical structure, in vitro/vivo stability, affinity toward serotonin receptors, blood-brain barrier permeation (BBB), and biodistribution study.

In vivo imaging using surface enhanced spatially offset raman spectroscopy (SESORS): balancing sampling frequency to improve overall image acquisition

In the field of optical imaging, the ability to image tumors at depth with high selectivity and specificity remains a challenge. Surface enhanced resonance Raman scattering (SERRS) nanoparticles (NPs) can be employed as image contrast agents to specifically target cells in vivo; however, this technique typically requires time-intensive point-by-point acquisition of Raman spectra. Here, we combine the use of "spatially offset Raman spectroscopy" (SORS) with that of SERRS in a technique known as "surface enhanced spatially offset resonance Raman spectroscopy" (SESORRS) to image deep-seated tumors in vivo. Additionally, by accounting for the laser spot size, we report an experimental approach for detecting both the bulk tumor, subsequent delineation of tumor margins at high speed, and the identification of a deeper secondary region of interest with fewer measurements than are typically applied. To enhance light collection efficiency, four modifications were made to a previously described custom-built SORS system. Specifically, the following parameters were increased: (i) the numerical aperture (NA) of the lens, from 0.2 to 0.34; (ii) the working distance of the probe, from 9 mm to 40 mm; (iii) the NA of the fiber, from 0.2 to 0.34; and (iv) the fiber diameter, from 100 μm to 400 μm. To calculate the sampling frequency, which refers to the number of data point spectra obtained for each image, we considered the laser spot size of the elliptical beam (6 × 4 mm). Using SERRS contrast agents, we performed in vivo SESORRS imaging on a GL261-Luc mouse model of glioblastoma at four distinct sampling frequencies: par-sampling frequency (12 data points collected), and over-frequency sampling by factors of 2 (35 data points collected), 5 (176 data points collected), and 10 (651 data points collected). In comparison to the previously reported SORS system, the modified SORS instrument showed a 300% improvement in signal-to-noise ratios (SNR). The results demonstrate the ability to acquire distinct Raman spectra from deep-seated glioblastomas in mice through the skull using a low power density (6.5 mW/mm2) and 30-times shorter integration times than a previous report (0.5 s versus 15 s). The ability to map the whole head of the mouse and determine a specific region of interest using as few as 12 spectra (6 s total acquisition time) is achieved. Subsequent use of a higher sampling frequency demonstrates it is possible to delineate the tumor margins in the region of interest with greater certainty. In addition, SESORRS images indicate the emergence of a secondary tumor region deeper within the brain in agreement with MRI and H&E staining. In comparison to traditional Raman imaging approaches, this approach enables improvements in the detection of deep-seated tumors in vivo through depths of several millimeters due to improvements in SNR, spectral resolution, and depth acquisition. This approach offers an opportunity to navigate larger areas of tissues in shorter time frames than previously reported, identify regions of interest, and then image the same area with greater resolution using a higher sampling frequency. Moreover, using a SESORRS approach, we demonstrate that it is possible to detect secondary, deeper-seated lesions through the intact skull.

Elucidating Iron Metabolism through Molecular Imaging

Iron is essential for many physiological processes, and the dysregulation of its metabolism is implicated in the pathogenesis of various diseases. Recent advances in iron metabolism research have revealed multiple complex pathways critical for maintaining iron homeostasis. Molecular imaging, an interdisciplinary imaging technique, has shown considerable promise in advancing research on iron metabolism. Here, we comprehensively review the multifaceted roles of iron at the cellular and systemic levels (along with the complex regulatory mechanisms of iron metabolism), elucidate appropriate imaging methods, and summarize their utility and fundamental principles in diagnosing and treating diseases related to iron metabolism. Utilizing molecular imaging technology to deeply understand the complexities of iron metabolism and its critical role in physiological and pathological processes offers new possibilities for early disease diagnosis, treatment monitoring, and the development of novel therapies. Despite technological limitations and the need to ensure the biological relevance and clinical applicability of imaging results, molecular imaging technology's potential to reveal the iron metabolic process is unparalleled, providing new insights into the link between iron metabolism abnormalities and various diseases.

Quantitative pharmacokinetic and biodistribution studies for fluorescent imaging agents

Pharmacokinetics and biodistribution studies are essential for characterizing fluorescent agents in vivo. However, few simple methods based on fluorescence imaging are available that account for tissue optical properties and sample volume differences. We describe a method for simultaneously quantifying mean fluorescence intensity of whole blood and homogenized tissues in glass capillary tubes for two fluorescent agents, ABY-029 and IRDye 680LT, using wide-field imaging and tissue-specific calibration curves. All calibration curves demonstrated a high degree of linearity with mean R2 = 0.99 ± 0.01 and RMSE = 0.12 ± 0.04. However, differences between linear regressions indicate that tissue-specific calibration curves are required for accurate concentration recovery. The lower limit of quantification (LLOQ) for all samples tested was determined to be < 0.3 nM for ABY-029 and < 0.4 nM for IRDye 680LT.

PET-MR Guided, Pre-targeted delivery to HER2(+) Breast Cancer Model

Purpose: HER2(+) metastatic breast cancer (mBC) is one of the most aggressive and lethal cancer types among females. While initially effective, targeted therapeutic approaches with trastuzumab and pertuzumab antibodies and antibody-drug conjugates (ADC) lack long-term efficacy against HER2(+) mBC and can cause severe systemic toxicity due to off-target effects. Therefore, the development of novel targeted delivery platforms that minimize toxicity and increase therapeutic efficacy is critical to the treatment of HER2(+) breast cancer (BC). A pretargeting delivery platform can minimize the non-specific accumulation and off-target toxicity caused by traditional one-step delivery method by separating the single delivery step into a pre-targeting step with high-affinity biomarker binding ligand followed by the subsequent delivery step of therapeutic component with fast clearance. Each delivery component is functionalized with bioorthogonal reactive groups that quickly react in situ , forming cross-linked clusters on the cell surface, which facilitates rapid internalization and intracellular delivery of therapeutics. Procedures: We have successfully developed a click chemistry-based pretargeting platform for HER2(+) BC enabling PET-MR image guidance for reduced radiation dose, high sensitivity, and good soft tissue contrast. Radiolabeled trastuzumab and superparamagnetic iron-oxide carriers (uSPIO) were selected as pretargeting and delivery components, respectively. HER2(+) BT-474 cell line and corresponding xenografts were used for in vitro and in vivo studies. Results: An enhanced tumor accumulation as well as tumor- to-organ accumulation ratio was observed in pretargeted mice up to 24 h post uSPIO injection. A 40% local T 1 decrease in the pretargeted mice tumor was observed within 4 h, and an overall 15% T 1 drop was retained for 24 h post uSPIO injection. Conclusions: Prolonged tumor retention and increased tumor-to-organ accumulation ratio provided a solid foundation for pretargeted image-guided delivery approach for in vivo applications.

Multivalent Fluorinated Nanorings for On-Cell 19F NMR

The design of imaging agents with a high fluorine content is necessary for overcoming the challenges of low sensitivity in 19F magnetic resonance imaging (MRI)-based molecular imaging. Chemically self-assembled nanorings (CSANs) provide a strategy to increase the fluorine content through multivalent display. We previously reported an 19F NMR-based imaging tracer, in which case a CSAN-compatible epidermal growth factor receptor (EGFR)-targeting protein E1-dimeric dihydrofolate (E1-DD) was bioconjugated to a highly fluorinated peptide. Despite good 19F NMR performance in aqueous solutions, a limited signal was observed in cell-based 19F NMR using this monomeric construct, motivating further design. Here, we design several new E1-DD proteins bioconjugated to peptides of different fluorine contents. Flow cytometry analysis was used to assess the effect of variable fluorinated peptide sequences on the cellular binding characteristics. Structure-optimized protein, RTC-3, displayed an optimal spectral performance with high affinity and specificity for EGFR-overexpressing cells. To further improve the fluorine content, we next engineered monomeric RTC-3 into CSAN, η-RTC-3. With an approximate eightfold increase in the fluorine content, multivalent η-RTC-3 maintained high cellular specificity and optimal 19F NMR spectral behavior. Importantly, the first cell-based 19F NMR spectra of η-RTC-3 were obtained bound to EGFR-expressing A431 cells, showing a significant amplification in the signal. This new design illustrated the potential of multivalent fluorinated CSANs for future 19F MRI molecular imaging applications.

Evaluating the Outcomes and Trainee Performance of a Canadian Medical Imaging Clinician Investigator Program

Purpose: To measure the research productivity of trainees from the University of Toronto's Medical Imaging Clinician Investigator Program (MI-CIP) and comparing it with the research productivity of trainees from MI-non-CIP and General Surgery (GSx) Clinician Investigator Program. Methods: We identified residents who completed an MI-CIP, MI-non-CIP and GSx-CIP from 2006-2016. In each group of trainees, we assessed 3 research productivity outcomes with non-parametric tests before residency and at 7 years post-CIP completion/post-graduation. Research productivity outcomes include the number of total publications, the number of first-author publications, and the publication's average journal impact factor (IF). Results: We identified 11 MI-CIP trainees (male/female: 9 [82%]/2 [18%]), 74 MI-non-CIP trainees (46 [62%]/28 [38%]) and 41 GSx-CIP trainees (23 [56%]/18 [44%]). MI-CIP trainees had statistically significant higher research productivity than MI-non-CIP in all measured outcomes. The median (interquartile range, IQR) number of total publications of MI-CIP vs MI-non-CIP trainees was 5.0 (8.0) vs 1.0 (2.0) before residency and 6.0 (10.0) vs .0 (2.0) at 7 years post-CIP completion/post-graduation. The median (IQR) first-author publications of MI-CIP vs MI-non-CIP trainees was 2.0 (3.0) vs .0 (1.0) before residency and 2.0 (4.0) vs (.0) (1.0) at 7 years post-CIP completion/post-graduation. The median (IQR) average journal IF of MI-CIP vs MI-non-CIP trainees was 3.2 (2.0) vs .3 (2.4) before residency and 3.9 (3.2) vs .0 (2.6) at 7 years post-CIP completion/post-graduation. Between MI-CIP and GSx-CIP trainees, there were no significant differences in research productivity in all measured outcomes. Conclusion: MI-CIP trainees actively conducted research after graduation. These trainees demonstrated early research engagement before residency. The similar research productivity of MI-CIP vs GSx-CIP trainees shows initial success of MI-CIP trainees.

Nanocrystals for Deep-Tissue In Vivo Luminescence Imaging in the Near-Infrared Region

In vivo imaging technologies have emerged as a powerful tool for both fundamental research and clinical practice. In particular, luminescence imaging in the tissue-transparent near-infrared (NIR, 700-1700 nm) region offers tremendous potential for visualizing biological architectures and pathophysiological events in living subjects with deep tissue penetration and high imaging contrast owing to the reduced light-tissue interactions of absorption, scattering, and autofluorescence. The distinctive quantum effects of nanocrystals have been harnessed to achieve exceptional photophysical properties, establishing them as a promising category of luminescent probes. In this comprehensive review, the interactions between light and biological tissues, as well as the advantages of NIR light for in vivo luminescence imaging, are initially elaborated. Subsequently, we focus on achieving deep tissue penetration and improved imaging contrast by optimizing the performance of nanocrystal fluorophores. The ingenious design strategies of NIR nanocrystal probes are discussed, along with their respective biomedical applications in versatile in vivo luminescence imaging modalities. Finally, thought-provoking reflections on the challenges and prospects for future clinical translation of nanocrystal-based in vivo luminescence imaging in the NIR region are wisely provided.

Nanoparticles for Thrombus Diagnosis and Therapy: Emerging Trends in Thrombus-theranostics

Cardiovascular disease is one of the chief factors that cause ischemic stroke, myocardial infarction, and venous thromboembolism. The elements that speed up thrombosis include nutritional consumption, physical activity, and oxidative stress. Even though the precise etiology and pathophysiology remain difficult topics that primarily rely on traditional medicine. The diagnosis and management of thrombosis are being developed using discrete non-invasive and non-surgical approaches. One of the emerging promising approach is ultrasound and photoacoustic imaging. The advancement of nanomedicines offers concentrated therapy and diagnosis, imparting efficacy and fewer side effects which is more significant than conventional medicine. This study addresses the potential of nanomedicines as theranostic agents for the treatment of thrombosis. In this article, we describe the factors that lead to thrombosis and its consequences, as well as summarize the findings of studies on thrombus formation in preclinical and clinical models and also provide insights on nanoparticles for thrombus imaging and therapy.

A Comprehensive Review of Treatment Strategies for Early Avascular Necrosis

Avascular necrosis (AVN), characterised by compromised blood supply leading to bone necrosis, poses a significant challenge in orthopaedic and rheumatologic practice. This review comprehensively examines early AVN treatment strategies, including aetiology and risk factors, clinical presentation, conservative and surgical approaches, emerging therapies, and rehabilitation. Key findings underscore the importance of early detection, personalised treatment plans, and a multidisciplinary approach involving orthopaedic specialists, rheumatologists, and physical therapists. The implications for clinical practice emphasise individualised care, staying abreast of emerging therapies, and patient education. Recommendations for future management strategies highlight the need for imaging technology advancements, regenerative therapies integration, and ongoing research into genetic and molecular pathways. As the field continues to evolve, translating research findings into clinical practice holds promise for improving outcomes and enhancing the overall quality of life for individuals affected by AVN.

Radiotracers in the Diagnosis of Pain: A Mini Review

The diagnosis and understanding of pain is challenging in clinical practice. Assessing pain relies heavily on self-reporting by patients, rendering it inherently subjective. Traditional clinical imaging methods such as computed tomography and magnetic resonance imaging can only detect anatomical abnormalities, offering limited sensitivity and specificity in identifying pain-causing conditions. Radiotracers play a vital role in molecular imaging that aims to identify abnormal biological processes at the cellular level, even in apparently normal anatomical structures. Therefore, molecular imaging is an important area of research as a prospective diagnostic modality for pain-causing pathophysiology. We present a mini review of the current knowledge base regarding radiotracers for identification of pain in vivo. We also describe radiocaine, a novel positron emission tomography imaging agent for sodium channels that has shown great potential for identifying/labeling pain-producing nerves and producing an objectively measurable pain intensity signal.

Choline metabolism and its implications in cancer

Choline, a quintessential quaternary ammonium compound, plays a cardinal role in several pivotal biological mechanisms, chiefly in safeguarding cell membrane integrity, orchestrating methylation reactions, and synthesizing vital neurotransmitters. This systematic review meticulously dissects the complex interplay between choline metabolism and its profound implications in oncology. The exposition is stratified into three salient dimensions: Initially, we delve into the intricacies of choline metabolism, accentuating its indispensability in cellular physiology, the enzymatic labyrinth governing its flux, and the pivotal cellular import mechanisms. Subsequently, we elucidate the contemporary comprehension of choline metabolism in the cancer paradigm, traversing its influence from inception to the intricate metamorphosis during oncogenic progression, further compounded by dysregulated enzyme activities and aberrant signaling cascades. Conclusively, we illuminate the burgeoning potential of choline-centric metabolic imaging modalities, notably magnetic resonance spectroscopy (MRS) and positron emission tomography (PET), as avant-garde tools for cancer diagnostics and therapeutic trajectory monitoring. Synoptically, the nuanced perturbations in choline metabolism in neoplastic entities unfurl critical insights, potentially heralding paradigm shifts in diagnostic and therapeutic oncological stratagems. A deeper foray into this realm is anticipated to fortify our molecular understanding and refine intervention modalities in cancer theranostics.

The Role of Molecular Imaging in Personalized Medicine

The concept of personalized medicine refers to the tailoring of medical treatment to each patient's unique characteristics. Scientific advancements have led to a better understanding of how a person's unique molecular and genetic profile makes them susceptible to certain diseases. It provides individualized medical treatments that will be safe and effective for each patient. Molecular imaging modalities play an essential role in this aspect. They are used widely in screening, detection and diagnosis, treatment, assessing disease heterogeneity and progression planning, molecular characteristics, and long-term follow-up. In contrast to conventional imaging approaches, molecular imaging techniques approach images as the knowledge that can be processed, allowing for the collection of relevant knowledge in addition to the evaluation of enormous patient groups. This review presents the fundamental role of molecular imaging modalities in personalized medicine.

Recent Advances in the Development of Pyrimidine-based CNS Agents

BACKGROUND

In the past few decades, considerable progress has been made in CNS drug discovery, and various new CNS agents have been developed. Pyrimidine is an important scaffold in the area of medicinal chemistry. Recently, pyrimidine-containing compounds have been successfully designed as potent CNS agents. Substantial research has been carried out on pyrimidine-bearing compounds to treat different disorders of CNS in various animal models.

METHODS

Utilizing various databases, including Google Scholar, PubMed, Science Direct, and Web of Science, the literature review was conducted. The specifics of significant articles were discussed with an emphasis on the potency of pyrimidines derivatives possessing CNS activity.

RESULTS

Recent papers indicating pyrimidine derivatives with CNS activity were incorporated into the manuscript. (46) to (50) papers included different pyrimidine derivatives as 5-HT agonist/antagonists, (62) to (67) as adenosine agonist/antagonist, (70) to (75) as anticonvulsant agents, (80) to (83) as cannabinoid receptor agonists, (102) to (103) as nicotinic and (110) as muscarinic receptor agonists. The remaining papers (113) to (114) represented pyrimidine-based molecular imaging agents.

CONCLUSION

Pyrimidine and its derivatives have been studied in detail to evaluate their efficacy in overcoming multiple central nervous system disorders. The article covers the current updates on pyrimidine-based compounds as potent CNS and molecular imaging agents and will definitely provide a better platform for the development of potent pyrimidine-based CNS drugs in the near future.

Recent Advancements in the Design and Development of Near Infrared (NIR) Emitting Fluorescent Probes for Sensing and their Bio-Imaging Applications

Fluorescent bio-imaging will be the future in the medical diagnostic for visualising inner cellular and tissues. Near-infrared (NIR) emitting fluorescent probes serve dynamically for targeted fluorescent imaging of live cells and tissues. NIR imaging is advantageous because of its merits like deep tissue penetration, minimum damage to the tissue, reduced auto fluorescence from the background, and improved resolution in imaging. The Development of the NIR emitting probe was well explored recently and growing drastically. In this review, we summarise recent achievements in NIR probes in between 2018-2021. The merits and future applications have also been discussed in this review.

Nanotheranostic Strategies for Cancer Immunotherapy

Despite advancements in cancer immunotherapy, heterogeneity in tumor response impose barriers to successful treatments and accurate prognosis. Effective therapy and early outcome detection are critical as toxicity profiles following immunotherapies can severely affect patients' quality of life. Existing imaging techniques, including positron emission tomography, computed tomography, magnetic resonance imaging, or multiplexed imaging, are often used in clinics yet suffer from limitations in the early assessment of immune response. Conventional strategies to validate immune response mainly rely on the Response Evaluation Criteria in Solid Tumors (RECIST) and the modified iRECIST for immuno-oncology drug trials. However, accurate monitoring of immunotherapy efficacy is challenging since the response does not always follow conventional RECIST criteria due to delayed and variable kinetics in immunotherapy responses. Engineered nanomaterials for immunotherapy applications have significantly contributed to overcoming these challenges by improving drug delivery and dynamic imaging techniques. This review summarizes challenges in recent immune-modulation approaches and traditional imaging tools, followed by emerging developments in three-in-one nanoimmunotheranostic systems co-opting nanotechnology, immunotherapy, and imaging. In addition, a comprehensive overview of imaging modalities in recent cancer immunotherapy research and a brief outlook on how nanotheranostic platforms can potentially advance to clinical translations for the field of immuno-oncology is presented.

Nanotechnology Advances in the Detection and Treatment of Cancer: An Overview

Over the last few years, progress has been made across the nanomedicine landscape, in particular, the invention of contemporary nanostructures for cancer diagnosis and overcoming complexities in the clinical treatment of cancerous tissues. Thanks to their small diameter and large surface-to-volume proportions, nanomaterials have special physicochemical properties that empower them to bind, absorb and transport high-efficiency substances, such as small molecular drugs, DNA, proteins, RNAs, and probes. They also have excellent durability, high carrier potential, the ability to integrate both hydrophobic and hydrophilic compounds, and compatibility with various transport routes, making them especially appealing over a wide range of oncology fields. This is also due to their configurable scale, structure, and surface properties. This review paper discusses how nanostructures can function as therapeutic vectors to enhance the therapeutic value of molecules; how nanomaterials can be used as medicinal products in gene therapy, photodynamics, and thermal treatment; and finally, the application of nanomaterials in the form of molecular imaging agents to diagnose and map tumor growth.

Molecular imaging as a tool for evaluation of COVID-19 sequelae – A review of literature

Coronavirus disease 2019 (COVID-19) is caused by the novel viral pathogen, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COVID-19 primarily involves the lungs. Nucleic acid testing based on reverse-transcription polymerase chain reaction of respiratory samples is the current gold standard for the diagnosis of SARS-CoV-2 infection. Imaging modalities have an established role in triaging, diagnosis, evaluation of disease severity, monitoring disease progression, extra-pulmonary involvement, and complications. As our understanding of the disease improves, there has been substantial evidence to highlight its potential for multi-systemic involvement and development of long-term sequelae. Molecular imaging techniques are highly sensitive, allowing non-invasive visualization of physiological or pathological processes at a cellular or molecular level with potential for detection of functional changes earlier than conventional radiological imaging. The purpose of this review article is to highlight the evolving role of molecular imaging in evaluation of COVID-19 sequelae. Though not ideal for diagnosis, the various modalities of molecular imaging play an important role in assessing pulmonary and extra-pulmonary sequelae of COVID-19. Perfusion imaging using single photon emission computed tomography fused with computed tomography (CT) can be utilized as a first-line imaging modality for COVID-19 related pulmonary embolism. ¹⁸F-fluorodeoxyglucose positron emission tomography (PET)/CT is a sensitive tool to detect multi-systemic inflammation, including myocardial and vascular inflammation. PET in conjunction with magnetic resonance imaging helps in better characterization of neurological sequelae of COVID-19. Despite the fact that the majority of published literature is retrospective in nature with limited sample sizes, it is clear that molecular imaging provides additional valuable information (complimentary to anatomical imaging) with semi-quantitative or quantitative parameters to define inflammatory burden and can be used to guide therapeutic strategies and assess response. However, widespread clinical applicability remains a challenge owing to longer image acquisition times and the need for adoption of infection control protocols.

Time-Resolved Luminescent Sensing and Imaging for Enzyme Catalytic Activity Based on Responsive Probes

Enzymes, as a kind of biomacromolecules, play an important role in many physiological processes and relate directly to various diseases. Developing an efficient detection method for enzyme activity is important to achieve early diagnosis of enzyme-relevant diseases and high throughput screening of potential enzyme-relevant drugs. Time-resolved luminescence assay provide a high accuracy and signal-to-noise ratios detection methods for enzyme activity, which has been widely used in high throughput screening of enzyme-relevant drugs and diagnosis of enzyme-relevant diseases. Inspired by these advantages, various responsive probes based on metal complexes and metal-free organic compounds have been developed for time-resolved bioimaging and biosensing of enzyme activity owing to their long luminescence lifetimes, high quantum yields and photostability. In this review, we comprehensively reviewed metal complex- and metal-free organic compound-based responsive probes applied to detect enzyme activity through time-resolved imaging, including their design strategies and sensing principles. Current challenges and future prospects in this rapidly growing field are also discussed.

3D Ultrasound-Guided Photoacoustic Imaging to Monitor the Effects of Suboptimal Tyrosine Kinase Inhibitor Therapy in Pancreatic Tumors

Pancreatic cancer is a disease with an incredibly poor survival rate. As only about 20% of patients are eligible for surgical resection, neoadjuvant treatments that can relieve symptoms and shrink tumors for surgical resection become critical. Many forms of treatments rely on increased vulnerability of cancerous cells, but tumors or regions within the tumors that may be hypoxic could be drug resistant. Particularly for neoadjuvant therapies such as the tyrosine kinase inhibitors utilized to shrink tumors, it is critical to monitor changes in vascular function and hypoxia to predict treatment efficacy. Current clinical imaging modalities used to obtain structural and functional information regarding hypoxia or oxygen saturation (StO2) do not provide sufficient depth penetration or require the use of exogenous contrast agents. Recently, ultrasound-guided photoacoustic imaging (US-PAI) has garnered significant popularity, as it can noninvasively provide multiparametric information on tumor vasculature and function without the need for contrast agents. Here, we built upon existing literature on US-PAI and demonstrate the importance of changes in StO2 values to predict treatment response, particularly tumor growth rate, when the outcomes are suboptimal. Specifically, we image xenograft mouse models of pancreatic adenocarcinoma treated with suboptimal doses of a tyrosine kinase inhibitor cabozantinib. We utilize the US-PAI data to develop a multivariate regression model that demonstrates that a therapy-induced reduction in tumor growth rate can be predicted with 100% positive predictive power and a moderate (58.33%) negative predictive power when a combination of pretreatment tumor volume and changes in StO2 values pretreatment and immediately posttreatment was employed. Overall, our study indicates that US-PAI has the potential to provide label-free surrogate imaging biomarkers that can predict tumor growth rate in suboptimal therapy.

Systematic Review: Targeted Molecular Imaging of Angiogenesis and Its Mediators in Rheumatoid Arthritis

Extensive angiogenesis is a characteristic feature in the synovial tissue of rheumatoid arthritis (RA) from a very early stage of the disease onward and constitutes a crucial event for the development of the proliferative synovium. This process is markedly intensified in patients with prolonged disease duration, high disease activity, disease severity, and significant inflammatory cell infiltration. Angiogenesis is therefore an interesting target for the development of new therapeutic approaches as well as disease monitoring strategies in RA. To this end, nuclear imaging modalities represent valuable non-invasive tools that can selectively target molecular markers of angiogenesis and accurately and quantitatively track molecular changes in multiple joints simultaneously. This systematic review summarizes the imaging markers used for single photon emission computed tomography (SPECT) and/or positron emission tomography (PET) approaches, targeting pathways and mediators involved in synovial neo-angiogenesis in RA.

Development of Radiotracers for Imaging of the PD-1/PD-L1 Axis

Immune checkpoint inhibitor (ICI) therapy has emerged as a major treatment option for a variety of cancers. Among the immune checkpoints addressed, the programmed death receptor 1 (PD-1) and its ligand PD-L1 are the key targets for an ICI. PD-L1 has especially been proven to be a reproducible biomarker allowing for therapy decisions and monitoring therapy success. However, the expression of PD-L1 is not only heterogeneous among and within tumor lesions, but the expression is very dynamic and changes over time. Immunohistochemistry, which is the standard diagnostic tool, can only inadequately address these challenges. On the other hand, molecular imaging techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) provide the advantage of a whole-body scan and therefore fully address the issue of the heterogeneous expression of checkpoints over time. Here, we provide an overview of existing PET, SPECT, and optical imaging (OI) (radio)tracers for the imaging of the upregulation levels of PD-1 and PD-L1. We summarize the preclinical and clinical data of the different molecule classes of radiotracers and discuss their respective advantages and disadvantages. At the end, we show possible future directions for developing new radiotracers for the imaging of PD-1/PD-L1 status in cancer patients.

Radiolabeling, biological distribution, docking and ADME studies of 99mTc-Ros as a promising natural tumor tracer

Rosmarinic acid (Ros) is one of phenolic metabolites with powerful potency as an anticancer agent, with different mechanisms to diminish the cancer cells. This current study represents radiolabeling of Ros with 99mTc using SnCl2 in pH4 for 15 min at 60 °C, The yield up to 92.2%. Biological evaluation in normal and cancer mice revealed the localization of the tracer in tumor tissue. Furthermore, docking and ADME (Absorption, Distribution, Metabolism, and Excretion) studies were performed, The resulted data clarifies the use of Ros as a promissing natural tracer.

SPECT Imaging of Acute Disc Herniation by Targeting Integrin α5β1 in Rat Models

Objective

Traditional morphological imaging of intervertebral disc herniation (IVDH) is challenging in early disease diagnosis. Aiming at the early diagnosis of IVD by non-invasive molecular imaging targeting of integrin α5β1, we performed novel imaging in rats with acute IVDH for the first time.

Methods

Animal models were prepared by conducting an established needle puncture procedure through the normal intervertebral disc (IVD). The disc-injured rats underwent SPECT/CT imaging of the ^99mTc-3PisoDGR2 peptide at 1 day to 2 months postinjury. The expression change of integrin α5β1 was determined by anti-integrin α5 and anti-integrin α5β1 immunohistochemistry (IHC). Magnetic resonance imaging (MRI) was performed for comparison during disease progression. The morphological changes of the disc were determined by safranin-O staining.

Results

Rats with acute IVDH showed gradually increased disc uptake of ^99mTc-3PisoDGR2 from 1 to 7 days posttreatment, which was a significantly higher level than that of the normal disks in degenerative diseases. IHC results showed the expression of integrin α5β1 on the surface of annulus fibrosus (AF) cells and nucleus pulposus (NP) cells, which agreed with the uptake data. MRI showed a progressively decreased T2 density and MRI index throughout the investigation. Hematoxylin and eosin (HE) staining and safranin-O staining revealed a disorganized structure of the IVD as well as loss of proteoglycans after puncture.

Conclusions

The present study demonstrated a good correlation between integrin α5β1 expression and acute disc herniation. The SPECT/CT imaging of ^99mTc-3PisoDGR2 targeting integrin α5β1 may diagnose IVDH in an acute phase for early disease management.

Challenges and opportunities in the development of metal-based anticancer theranostic agents

Around 10 million fatalities were recorded worldwide in 2020 due to cancer and statistical projections estimate the number to increase by 60% in 2040. With such a substantial rise in the global cancer burden, the disease will continue to impose a huge socio-economic burden on society. Currently, the most widely used clinical treatment modality is cytotoxic chemotherapy using platinum drugs which is used to treat variety of cancers. Despite its clinical success, critical challenges like resistance, off-target side effects and cancer variability often reduce its overall therapeutic efficiency. These challenges require faster diagnosis, simultaneous therapy and a more personalized approach toward cancer management. To this end, small-molecule ‘theranostic’ agents have presented a viable solution combining diagnosis and therapy into a single platform. In this review, we present a summary of recent efforts in the design and optimization of metal-based small-molecule ‘theranostic’ anticancer agents. Importantly, we highlight the advantages of a theranostic candidate over the purely therapeutic or diagnostic agent in terms of evaluation of its biological properties.

Advances in Biosensor Technologies for Acute Kidney Injury

Acute kidney injury (AKI) is one of the most prevalent and complex clinical syndromes with high morbidity and mortality. The traditional diagnosis parameters are insufficient regarding specificity and sensitivity, and therefore, novel biomarkers and their facile and rapid applications are being sought to improve the diagnostic procedures. The biosensors, which are employed on the basis of electrochemistry, plasmonics, molecular probes, and nanoparticles, are the prominent ways of developing point-of-care devices, along with the mutual integration of efficient surface chemistry strategies. In this manner, biosensing platforms hold pivotal significance in detecting and quantifying novel AKI biomarkers to improve diagnostic interventions, potentially accelerating clinical management to control the injury in a timely manner. In this review, novel diagnostic platforms and their manufacturing processes are presented comprehensively. Furthermore, strategies to boost their effectiveness are also indicated with several applications. To maximize these efforts, we also review various biosensing approaches with a number of biorecognition elements (e.g., antibodies, aptamers, and molecular imprinting molecules), as well as benchmark their features such as robustness, stability, and specificity of these platforms.

A metabolic acidity-activatable calcium phosphate probe with fluorescence signal amplification capabilities for non-invasive imaging of tumor malignancy

Dysregulated energy metabolism has recently been recognized as an emerging hallmark of cancer. Tumor cells, which are characterized by abnormal glycolysis, exhibit a lower extracellular pH (6.5-7.0) than normal tissues (7.2-7.4), providing a promising target for tumor-specific imaging and therapy. However, most pH-sensitive materials are unable to distinguish such a subtle pH difference owing to their wide and continuous pH-responsive range. In this study, we developed an efficient strategy for the fabrication of a tumor metabolic acidity-activatable calcium phosphate (CaP) fluorescent probe (termed MACaP9). Unlike traditional CaP-based biomedical nanomaterials, which only work within more acidic organelles, such as endosomes and lysosomes (pH 4.0-6.0), MACaP9 could not only specifically respond to the tumor extra-cellular pH but also rapidly convert pH variations into a distinct fluorescence signal to visually distinguish tumor from normal tissues. The superior sensitivity and specificity of MACaP9 enabled high-contrast visualization of a broad range of tumors, as well as small tumor lesions.

Cold Kit Labeling: The Future of 68Ga Radiopharmaceuticals?

Over the last couple of decades, gallium-68 (68Ga) has gained a formidable interest for PET molecular imaging of various conditions, from cancer to infection, through cardiac pathologies or neuropathies. It has gained routine use, with successful radiopharmaceuticals such as somatostatin analogs ([68Ga]Ga-DOTATOC and [68Ga]GaDOTATATE) for neuroendocrine tumors, and PSMA ligands for prostate cancer. It represents a major clinical impact, particularly in the context of theranostics, coupled with their 177Lu-labeled counterparts. Beside those, a bunch of new 68Ga-labeled molecules are in the preclinical and clinical pipelines, with some of them showing great promise for patient care. Increasing clinical demand and regulatory issues have led to the development of automated procedures for the production of 68Ga radiopharmaceuticals. However, the widespread use of these radiopharmaceuticals may rely on simple and efficient radiolabeling methods, undemanding in terms of equipment and infrastructure. To make them technically and economically accessible to the medical community and its patients, it appears mandatory to develop a procedure similar to the well-established kit-based 99mTc chemistry. Already available commercial kits for the production of 68Ga radiopharmaceuticals have demonstrated the feasibility of using such an approach, thus paving the way for more kit-based 68Ga radiopharmaceuticals to be developed. This article discusses the development of 68Ga cold kit radiopharmacy, including technical issues, and regulatory aspects.

Dendrimer-Based Nanogels for Cancer Nanomedicine Applications

Recent advances in the field of nanotechnology bring an alternative approach to personalized medicine in cancer treatment. Nanogels (NGs) are among the nanosized superconstructs composed of amphiphilic or hydrophilic polymer networks. The design of different types of biodegradable polymer-based NGs in various biomedical applications has received extensive attention, due to their unique physicochemical properties such as highly porous structure, stimuli-responsiveness, and mimicking of some biological properties. In this review, we concisely surveyed the synthesis of dendrimer-based NGs synthesized via different methods including covalent conjugation, inverse nanoprecipitation, physical cross-linking, or self-assembly for various cancer nanomedicine applications, particularly for drug delivery, gene delivery, photothermal therapy, and combination therapy, as well as for biological imaging-guided chemotherapy. Additionally, we provide herein future perspective toward the new design of dendrimer-based NGs for different cancer nanomedicine uses.

Sensitivity improved Cerenkov luminescence endoscopy using optimal system parameters

Background

The challenges of clinical translation of optical imaging, including the limited availability of clinically used imaging probes and the restricted penetration depth of light propagation in tissues can be avoided using Cerenkov luminescence endoscopy (CLE). However, the clinical applications of CLE are limited due to the low signal level of Cerenkov luminescence and the large transmission loss caused by the endoscope, which results in a relatively low detection sensitivity of current CLE. The aim of this study was to enhance the detection sensitivity of the CLE system and thus improve the system for clinical application in the detection of gastrointestinal diseases.

Methods

Four optical fiber endoscopes were customized with different system parameters, including monofilament (MF) diameter of imaging fiber bundles, fiber material, probe coating, etc. The endoscopes were connected to the detector via a specifically designed straight connection device to form the CLE system. The β-2-[¹⁸F]-Fluoro-2-deoxy-D-glucose (¹⁸F-FDG) solution and the radionuclide of Gallium-68 (⁶⁸Ga) were used to evaluate the performance of the CLE system. The images of the ¹⁸F-FDG solution acquired by the CLE were used to optimize imaging parameters of the system. By using the endoscope with optimized parameters, including the MF diameter of imaging fiber bundles, fiber materials, etc., the resolution and sensitivity of the assembled CLE system were measured by imaging the radionuclide of ⁶⁸Ga.

Results

The results of ¹⁸F-FDG experiments showed that larger MF diameter led to higher collection efficiency. The fiber material and probe coating with high transmission ratios in the range of 400-900 nm also increased signal collection and transmission efficiency. The results of ⁶⁸Ga evaluations showed that a minimum radioactive activity of radionuclides as low as 0.03 µCi was detected in vitro within 5 minutes, while that of 0.68 µCi can be detected within 1 minute. In vivo experiments also demonstrated that the developed CLE system achieved a high sensitivity at a submicrocurie level; that is, 0.44 µCi within 5 minutes, and 0.83 µCi within 1 minute. The weaker in vivo sensitivity was due to the attenuation of the signal by the mouse tissue skin and the autofluorescence interference produced by biological tissues.

Conclusions

By optimizing the structural parameters of fiber endoscope and imaging parameters for data acquisition, we developed a CLE system with a sensitivity at submicrocurie level. These results support the possibility that this technology can clinically detect early tumors within 1 minute.

Redox Chemistry-Enabled Stepwise Surface Dual Nanoparticle Engineering of 2D MXenes for Tumor-Sensitive T1&T2 MRI-Guided Photonic Breast-Cancer Hyperthermia in NIR-II Biowindow

With the fast advent of two-dimensional (2D) MXenes, several therapeutic paradigms based on 2D MXene flourish, but it still lacks a generic strategy for MXenes’ functionalization to achieve theranostic functionalities...

An Acidity-Initiated Self-Assembly/Disassembly Nanoprobe to Switch on Fluorescence for Tumor-Targeted Near-Infrared Imaging

The deep penetration, real-time monitoring ability, and high resolution of near-infrared (NIR) fluorescence imaging make it suitable for tumor diagnosis. However, the lack of specificity and selectivity restricts its further application. Here, for the first time, we applied a CBT-Cys click condensation reaction to synthesize an acidity-initiated molecular probe (AIM-Probe, Cys(StBu)-Lys(Cy 5.5)-EDA-PMA-CBT), which could self-assemble into nanoparticles (AIM-NP) with self-quenched fluorescence under glutathione (GSH) reduction. AIM-NP could accumulate in tumors after intravenous injection. Subsequently, the EDA-PMA part of AIM-Probe in AIM-NP is fractured by the unique subacid condition in the tumor microenvironment, and AIM-NP disassembles into a small AIM-cleaved molecule (PMA-CBT-Cys-Lys(Cy5.5)-EDA) along with fluorescence switching on. As a result, AIM-NP could switch on fluorescence at the tumor site, thereby achieving tumor-targeted imaging. To our knowledge, utilizing tumor acidity to initiate the disassembly of self-assembled nanoparticles through a CBT-Cys click condensation reaction has not been reported.

Towards Imaging Pt Chemoresistance Using Gd(III)-Pt(II) Theranostic MR Contrast Agents

Cisplatin and related Pt(II) chemotherapeutics are indispensable tools for the treatment of various solid tumors. Despite their widespread clinical use in approximately 50 % of chemotherapy regimens, they are hindered by issues with off-target toxicity and chemoresistance, both innate and acquired. To date, there is no effective way to predict the outcome of Pt(II) chemotherapy because the genes associated with resistance are not completely known or understood. Instead, patients undergo weeks to months of potentially harmful therapy before knowing if it is effective. Here we report two Gd(III)-Pt(II) theranostic MR contrast agents that contain cisplatin and carboplatin-based moieties respectively. We used these agents to demonstrate that accumulation differences in Pt(II) sensitive and resistant cells, a dominant factor in chemoresistance, can be imaged by MR. Both theranostic agents bind to DNA, are cytotoxic, and enhance the intracellular T₁ -weighted MR contrast of multiple cell lines. Most importantly, the cisplatin-based agent accumulates less in Pt(II) resistant cells in vitro and in vivo, resulting in decreased MR contrast enhancement compared to the parent Pt(II) sensitive cell line. This straightforward method to image a key factor of Pt(II) resistance using MRI is an important first step towards the ultimate goals of predicting response to Pt(II) chemotherapy and monitoring for the onset of chemoresistance - a critical unmet need in medicine that could significantly improve patient outcomes.

Advances in magnetic resonance imaging contrast agents for glioblastoma-targeting theranostics

Glioblastoma (GBM) is the most aggressive malignant brain tumour, with a median survival of 3 months without treatment and 15 months with treatment. Early GBM diagnosis can significantly improve patient survival due to early treatment and management procedures. Magnetic resonance imaging (MRI) using contrast agents is the preferred method for the preoperative detection of GBM tumours. However, commercially available clinical contrast agents do not accurately distinguish between GBM, surrounding normal tissue and other cancer types due to their limited ability to cross the blood–brain barrier, their low relaxivity and their potential toxicity. New GBM-specific contrast agents are urgently needed to overcome the limitations of current contrast agents. Recent advances in nanotechnology have produced alternative GBM-targeting contrast agents. The surfaces of nanoparticles (NPs) can be modified with multimodal contrast imaging agents and ligands that can specifically enhance the accumulation of NPs at GBM sites. Using advanced imaging technology, multimodal NP-based contrast agents have been used to obtain accurate GBM diagnoses in addition to an increased amount of clinical diagnostic information. NPs can also serve as drug delivery systems for GBM treatments. This review focuses on the research progress for GBM-targeting MRI contrast agents as well as MRI-guided GBM therapy.

Optical to Planar X-ray Mouse Image Mapping in Preclinical Nuclear Medicine Using Conditional Adversarial Networks

In the current work, a pix2pix conditional generative adversarial network has been evaluated as a potential solution for generating adequately accurate synthesized morphological X-ray images by translating standard photographic images of mice. Such an approach will benefit 2D functional molecular imaging techniques, such as planar radioisotope and/or fluorescence/bioluminescence imaging, by providing high-resolution information for anatomical mapping, but not for diagnosis, using conventional photographic sensors. Planar functional imaging offers an efficient alternative to biodistribution ex vivo studies and/or 3D high-end molecular imaging systems since it can be effectively used to track new tracers and study the accumulation from zero point in time post-injection. The superimposition of functional information with an artificially produced X-ray image may enhance overall image information in such systems without added complexity and cost. The network has been trained in 700 input (photography)/ground truth (X-ray) paired mouse images and evaluated using a test dataset composed of 80 photographic images and 80 ground truth X-ray images. Performance metrics such as peak signal-to-noise ratio (PSNR), structural similarity index measure (SSIM) and Fréchet inception distance (FID) were used to quantitatively evaluate the proposed approach in the acquired dataset.

Toward Sensitive and Reliable Surface-Enhanced Raman Scattering Imaging: From Rational Design to Biomedical Applications

Early specific detection through indicative biomarkers and precise visualization of lesion sites are urgent requirements for clinical disease diagnosis. However, current detection and optical imaging methods are insufficient for these demands. Molecular imaging technologies are being intensely studied for reliable medical diagnosis. In the past several decades, molecular imaging with surface-enhanced Raman scattering (SERS) has significant advances from analytical chemistry to medical science. SERS is the inelastic scattering generated from the interaction between photons and substances, presenting molecular structure information. The outstanding SERS virtues of high sensitivity, high specificity, and resistance to biointerference are highly advantageous for biomarker detection in a complex biological matrix. In this work, we review recent progress on the applications of SERS imaging in clinical diagnostics. With the assistance of SERS imaging, the detection of disease-related proteins, nucleic acids, small molecules, and pH of the cellular microenvironment can be implemented for adjuvant medical diagnosis. Moreover, multimodal imaging integrates the high penetration and high speed of other imaging modalities and imaging precision of SERS imaging, resulting in final complete and accurate imaging outcomes and exhibiting robust potential in the discrimination of pathological tissues and surgical navigation. As a promising molecular imaging technology, SERS imaging has achieved remarkable performance in clinical diagnostics and the biomedical realm. It is expected that this review will provide insights for further development of SERS imaging and promote the rapid progress and successful translation of advanced molecular imaging with clinical diagnostics.

Tumor Microenvironment Responsive "Head-to-Foot" Self-Assembly Nanoplatform for Positron Emission Tomography Imaging in Living Subjects

Sensitivity and specificity of molecular probes are two important factors in determining the accuracy of cancer diagnosis or the efficacy of cancer treatment. However, the development of probes with high sensitivity and strong specificity still poses many challenges. Herein, we report an ¹⁸F-labeled smart tracer ([¹⁸F]1) targeting cancer-associated biotin receptor (BR) and self-assembling into nanoparticles in response to intracellular glutathione. The tracer [¹⁸F]1 selectively targeted BR-positive cancer cells A549 and Hela and formed nanoparticles through self-assembly with an average diameter of 138.2 ± 16.3 nm. The character of self-assembly into nanoparticles enhanced the uptake and extended the retention of probe [¹⁸F]1 in the target tissue and hence improved the quality of positron emission tomography (PET) images. Thus, [¹⁸F]1 is a promising PET tracer for accurately detecting BR-positive cancers. Moreover, the tumor microenvironment responsive "head-to-foot" self-assembly nanoplatform is particularly attractive for development of other smart molecular probes.

Emerging contrast-enhanced ultrasound applications in children

Ultrasound contrast agent (UCA) use in radiology is expanding beyond traditional applications such as evaluation of liver lesions, vesicoureteral reflux and echocardiography. Among emerging techniques, 3-D and 4-D contrast-enhanced ultrasound (CEUS) imaging have demonstrated potential in enhancing the accuracy of voiding urosonography and are ready for wider clinical adoption. US contrast-based lymphatic imaging has been implemented for guiding needle placement in MR lymphangiography in children. In adults, intraoperative CEUS imaging has improved diagnosis and assisted surgical management in tumor resection, and its translation to pediatric brain tumor surgery is imminent. Because of growing interest in precision medicine, targeted US molecular imaging is a topic of active preclinical research and early stage clinical translation. Finally, an exciting new development in the application of UCA is in the field of localized drug delivery and release, with a particular emphasis on treating aggressive brain tumors. Under the appropriate acoustic settings, UCA can reversibly open the blood-brain barrier, allowing drug delivery into the brain. The aim of this article is to review the emerging CEUS applications and provide evidence regarding the feasibility of these applications for clinical implementation.

Non-invasive cell-tracking methods for adoptive T cell therapies

Adoptive T cell therapies (ACT) have demonstrated groundbreaking results in blood cancers and melanoma. Nevertheless, their significant cost, the occurrence of severe adverse events, and their poor performance in solid tumors are important hurdles hampering more widespread applicability. In vivo cell tracking allows instantaneous and non-invasive monitoring of the distribution, tumor homing, persistence, and redistribution to other organs of infused T cells in patients. Furthermore, cell tracking could aid in the clinical management of patients, allowing the detection of non-responders or severe adverse events at an early stage. This review provides a concise overview of the main principles and potential of cell tracking, followed by a discussion of the clinically relevant labeling strategies and their application in ACT.