CT Imaging of Enzymatic Activity in Cancer Using Covalent Probes Reveal a Size-Dependent Pattern

Nanopore sensing of protein and peptide conformation for point-of-care applications

The global population's aging and growth will likely result in an increase in chronic aging-related diseases. Early diagnosis could improve the medical care and quality of life. Many diseases are linked to misfolding or conformational changes in biomarker peptides and proteins, which affect their function and binding properties. Current clinical methods struggle to detect and quantify these changes. Therefore, there is a need for sensitive conformational sensors that can detect low-concentration analytes in biofluids. Nanopore electrical detection has shown potential in sensing subtle protein and peptide conformation changes. This technique can detect single molecules label-free while distinguishing shape or physicochemical property changes. Its proven sensitivity makes nanopore sensing technology promising for ultra-sensitive, personalized point-of-care devices. We focus on the capability of nanopore sensing for detecting and quantifying conformational modifications and enantiomers in biomarker proteins and peptides and discuss this technology as a solution to future societal health challenges.

Molecular Engineering of a SICTERS Small Molecule with Superior In Vivo Raman Imaging and Photothermal Performance

Raman-based theranostics has demonstrated great potential for sensitive real-time imaging and treatment. However, these advanced materials, primarily depending on the SERS technique, encounter clinical concerns regarding substrate biosafety. Herein, we molecularly engineered a de novo substrate-free SICTERS small molecule, namely BTT-TPA (bis-thienyl-substituted benzotriazole selenadiazole derivative structures), possessing both ultrasensitive Raman signals and excellent photothermal effects based on self-stacking. The mechanistic studies confirm that BTT maintains the planar structure with polycyclic distorted vibrations required for SICTERS. TPA enhances the donor-acceptor interaction, yielding a Raman sensitivity of BTT higher than previously reported SICTERS molecules; it also acts as a molecular rotor, increasing the photothermal conversion efficiency to 67.44%, which is superior to most of the existing SERS-based photothermal materials. In the tumor model of mouse orthotopic colon cancer, BTT-TPA NPs demonstrate a great Raman imaging-guided photothermal therapy effect in eliminating primary and metastatic tumors, remarkably decreasing the recurrence rate. This work puts forward substrate-free SICTERS small molecules toward Raman-based theranostic applications in vivo.

Cysteine cathepsins: From diagnosis to targeted therapy of cancer

Cysteine cathepsins are a fascinating group of proteolytic enzymes that play diverse and crucial roles in numerous biological processes, both in health and disease. Understanding these proteases is essential for uncovering novel insights into the underlying mechanisms of a wide range of disorders, such as cancer. Cysteine cathepsins influence cancer biology by participating in processes such as extracellular matrix degradation, angiogenesis, immune evasion, and apoptosis. In this comprehensive review, we explore foundational research that illuminates the diverse and intricate roles of cysteine cathepsins as diagnostic markers and therapeutic targets for cancer. This review aims to provide valuable insights into the clinical relevance of cysteine cathepsins and explore their capacity to advance personalised and targeted medical interventions in oncology.

Recent advances for enhanced photodynamic therapy: from new mechanisms to innovative strategies

Photodynamic therapy (PDT) has been developed as a potential cancer treatment approach owing to its non-invasiveness, spatiotemporal control and limited side effects. Currently, great efforts have been made to improve the PDT effect in terms of safety and efficiency. In this review, we highlight recent advances in innovative strategies for enhanced PDT, including (1) the development of novel radicals, (2) design of activatable photosensitizers based on the TME and light, and (3) photocatalytic NADH oxidation to damage the mitochondrial electron transport chain. Additionally, the new mechanisms for PDT are also presented as an inspiration for the design of novel PSs. Finally, we discuss the current challenges and future prospects in the clinical practice of these innovative strategies. It is hoped that this review will provide a new angle for understanding the relationship between the intratumoural redox environment and PDT mechanisms, and new ideas for the future development of smart PDT systems.

Artificial Intelligence-Driven Platform: Unveiling Critical Hepatic Molecular Alterations in Hepatocellular Carcinoma Development

Since most Hepatocellular Carcinoma (HCC) typically arises as a consequence of long-term liver damage, the hepatic molecular characteristics are closely related to the occurrence of HCC. Gaining comprehensive information about the location, morphology, and hepatic molecular alterations related to HCC is essential for accurate diagnosis. However, there is a dearth of technological advancements capable of concurrently providing precise HCC diagnosis and discerning the accompanying hepatic molecular alterations. In this study, an integrated information system is developed for the pathological-level diagnosis of HCC and the revelation of critical molecular alterations in the liver. This system utilizes computed tomography/Surface-enhanced Raman scattering combined with an artificial intelligence strategy to establish connections between the occurrence of HCC and alterations in hepatic biomolecules. Employing artificial intelligence techniques, the SERS spectra from both healthy and HCC groups are successfully classified into two distinct categories with a remarkable accuracy rate of 91.38%. Based on molecular profiling, it is identified that the nucleotide-to-lipid signal ratio holds significant potential as a reliable indicator for the occurrence of HCC, thereby serving as a promising tool for prevention and therapeutic surveillance.

Engineering Nanoplatforms for Theranostics of Atherosclerotic Plaques

Atherosclerotic plaque formation is considered the primary pathological mechanism underlying atherosclerotic cardiovascular diseases, leading to severe cardiovascular events such as stroke, acute coronary syndromes, and even sudden cardiac death. Early detection and timely intervention of plaques are challenging due to the lack of typical symptoms in the initial stages. Therefore, precise early detection and intervention play a crucial role in risk stratification of atherosclerotic plaques and achieving favorable post-interventional outcomes. The continuously advancing nanoplatforms have demonstrated numerous advantages including high signal-to-noise ratio, enhanced bioavailability, and specific targeting capabilities for imaging agents and therapeutic drugs, enabling effective visualization and management of atherosclerotic plaques. Motivated by these superior properties, various noninvasive imaging modalities for early recognition of plaques in the preliminary stage of atherosclerosis are comprehensively summarized. Additionally, several therapeutic strategies are proposed to enhance the efficacy of treating atherosclerotic plaques. Finally, existing challenges and promising prospects for accelerating clinical translation of nanoplatform-based molecular imaging and therapy for atherosclerotic plaques are discussed. In conclusion, this review provides an insightful perspective on the diagnosis and therapy of atherosclerotic plaques.

Covalent activity-based probes for imaging of serine proteases

Serine proteases are one of the largest mechanistic classes of proteases. They regulate a plethora of biochemical pathways inside and outside the cell. Aberrant serine protease activity leads to a wide variety of human diseases. Reagents to visualize these activities can be used to gain insight into the biological roles of serine proteases. Moreover, they may find future use for the detection of serine proteases as biomarkers. In this review, we discuss small molecule tools to image serine protease activity. Specifically, we outline different covalent activity-based probes and their selectivity against various serine protease targets. We also describe their application in several imaging methods.

An Adaptable Nanoprobe Integrated with Quantitative T1 -Mapping MRI for Accurate Differential Diagnosis of Multidrug-Resistant Lung Cancer

Multidrug resistance (MDR) is one of the major factors causing failure of non-small-cell lung cancer (NSCLC) chemotherapy. Real-time and accurate differentiation between drug-resistant and sensitive NSCLC is of primary importance for guiding the subsequent treatments and improving the therapeutic outcome. However, there is no effective method to provide such an accurate differentiation. This study creates an innovative strategy of integrating H2 O2 -responsive nanoprobes with the quantitative T1 -mapping magnetic resonance imaging (MRI) technique to achieve an accurate differential diagnosis between drug-resistant and sensitive NSCLC in light of differences in H2 O2 content in the tumor microenvironment (TME). The result demonstrates that the synthesized MIL-53(Fe)@MnO2 nanocomposites possess an excellent capability of shortening the cancer longitudinal relaxation time (T1 ) when meeting H2 O2 in TME. T1 -mapping MRI could sensitively detect this T1 variation (about 2.6-fold that of T1-weighted imaging (T1 WI)) to accurately differentiate the H2 O2 content between drug-resistant and sensitive NSCLC. In addition, the quantitative data provided by the T1 -mapping MRI dedicates correct comparison across imaging tests and is more reliable than T1 WI, thus giving it a chance for precise assessment of the anti-cancer effect. This innovative strategy of merging TME adaptable nanoprobes with the quantitative MRI technique provides a new approach for the precise diagnosis of multidrug-resistant NSCLC.

Single Doping for Triple Functions: Integrated Theranostic Nanoplatforms for Multimodal Image-Guided Tumor Therapy

Accurate location and efficient treatment of diseases by multifunctional nanoplatforms are appealing but face great challenges. Theranostic agents through the physical combination of different functional nanoparticles are demonstrated to be effective. Yet, the complicated biological environment often leads to ambiguous fates of each agent, which fails to keep the behaviors of imaging and therapeutic components in a simultaneous manner. Herein, "integrated" theranostic NPs, Gd-doped CuWO4 (CWG) with strong near-infrared (808 nm) absorption, the longest absorption peak of reported CuWO4 , located in the biological transparent window, are constructed. The single doping of trace amount of Gd not only endows them with a distinguished magnetic resonance imaging capability (r1 = 12.01 mM-1 s-1 ), but also concurrently imposes great effect on the valence states of matrix ion (Cu), as evidenced by theoretical calculation results. The charge distribution shift of Cu would facilitate ·OH generation, beneficial for chemodynamic therapy (CDT). Moreover, CWG NPs display remarkable photoacoustic (PA) and computed tomography (CT) imaging capabilities (S = 10.33 HU mM-1 ). Such integrated theranostics afford a paradigm for multimodal imaging-guided synergistic therapy with all-in-one single nanoparticle.

Heavy Metal-Based Nanoparticles as High-Performance X-ray Computed Tomography Contrast Agents

X-ray computed tomography (CT) contrast agents offer extremely valuable tools and techniques in diagnostics via contrast enhancements. Heavy metal-based nanoparticles (NPs) can provide high contrast in CT images due to the high density of heavy metal atoms with high X-ray attenuation coefficients that exceed that of iodine (I), which is currently used in hydrophilic organic CT contrast agents. Nontoxicity and colloidal stability are vital characteristics in designing heavy metal-based NPs as CT contrast agents. In addition, a small particle size is desirable for in vivo renal excretion. In vitro phantom imaging studies have been performed to obtain X-ray attenuation efficiency, which is a critical parameter for CT contrast agents, and the imaging performance of CT contrast agents has been demonstrated via in vivo experiments. In this review, we focus on the in vitro and in vivo studies of various heavy metal-based NPs in pure metallic or chemical forms, including Au, Pt, Pd, Ag, Ce, Gd, Dy, Ho, Yb, Ta, W, and Bi, and provide an outlook on their use as high-performance CT contrast agents.

Illuminating and Radiosensitizing Tumors with 2DG-Bound Gold-Based Nanomedicine for Targeted CT Imaging and Therapy

Although radiotherapy is one of the most important curative treatments for cancer, its clinical application is associated with undesired therapeutic effects on normal or healthy tissues. The use of targeted agents that can simultaneously achieve therapeutic and imaging functions could constitute a potential solution. Herein, we developed 2-deoxy-d-glucose (2DG)-labeled poly(ethylene glycol) (PEG) gold nanodots (2DG-PEG-AuD) as a tumor-targeted computed tomography (CT) contrast agent and radiosensitizer. The key advantages of the design are its biocompatibility and targeted AuD with excellent sensitivity in tumor detection via avid glucose metabolism. As a consequence, CT imaging with enhanced sensitivity and remarkable radiotherapeutic efficacy could be attained. Our synthesized AuD displayed linear enhancement of CT contrast as a function of its concentration. In addition, 2DG-PEG-AuD successfully demonstrated significant augmentation of CT contrast in both in vitro cell studies and in vivo tumor-bearing mouse models. In tumor-bearing mice, 2DG-PEG-AuD showed excellent radiosensitizing functions after intravenous injection. Results from this work indicate that 2DG-PEG-AuD could greatly potentiate theranostic capabilities by providing high-resolution anatomical and functional images in a single CT scan and therapeutic capability.

Ultrasmall, elementary and highly translational nanoparticle X-ray contrast media from amphiphilic iodinated statistical copolymers

To expand the single-dose duration over which noninvasive clinical and preclinical cancer imaging can be conducted with high sensitivity, and well-defined spatial and temporal resolutions, a facile strategy to prepare ultrasmall nanoparticulate X-ray contrast media (nano-XRCM) as dual-modality imaging agents for positron emission tomography (PET) and computed tomography (CT) has been established. Synthesized from controlled copolymerization of triiodobenzoyl ethyl acrylate and oligo(ethylene oxide) acrylate monomers, the amphiphilic statistical iodocopolymers (ICPs) could directly dissolve in water to afford thermodynamically stable solutions with high aqueous iodine concentrations (>140 mg iodine/mL water) and comparable viscosities to conventional small molecule XRCM. The formation of ultrasmall iodinated nanoparticles with hydrodynamic diameters of ca. 10 nm in water was confirmed by dynamic and static light scattering techniques. In a breast cancer mouse model, in vivo biodistribution studies revealed that the 64Cu-chelator-functionalized iodinated nano-XRCM exhibited extended blood residency and higher tumor accumulation compared to typical small molecule imaging agents. PET/CT imaging of tumor over 3 days showed good correlation between PET and CT signals, while CT imaging allowed continuous observation of tumor retention even after 10 days post-injection, enabling longitudinal monitoring of tumor retention for imaging or potentially therapeutic effect after a single administration of nano-XRCM.

Surface hydrolysis-designed AuNPs-zwitterionic-glucose as a novel tool for targeting macrophage visualization and delivery into infarcted hearts

Macrophages, innate immune cells, are key players in the maintenance of myocardial homeostasis under normal conditions and tissue repair after injury. The infiltration of macrophages into the injured heart makes them a potentially appealing vehicle for noninvasive imaging and targeted drug delivery of myocardial infarction (MI). In this study, we demonstrated the use of surface hydrolysis-designed AuNPs-zwitterionic-glucose to label macrophages and track their infiltration into isoproterenol hydrochloride (ISO)-induced MI sites noninvasively using CT. The AuNPs-zwitterionic-glucose did not affect the viability or cytokine release of macrophages and were highly taken up by these cells. The in vivo CT images were obtained on Day 4, Day 6, Day 7, and Day 9, and the attenuation was seen to increase in the heart over time compared to the Day 4 scan. In vitro analysis also confirmed the presence of macrophages around injured cardiomyocytes. Additionally, we also addressed the concern of cell tracking or merely AuNP tracking, which is the inherent problem for any form of nanoparticle-labeled cell tracking by using zwitterionic and glucose-functionalized AuNPs. The glucose coated on the surface of AuNPs-zwit-glucose will be hydrolyzed in macrophages, forming only zwitterionic protected AuNPs that cannot be taken up again by endogenous cells in vivo. This will greatly improve the accuracy and precision of imaging and target delivery. We believe this is the first study to noninvasively visualize the infiltration of macrophages into MI hearts using CT, which could be used for imaging and evaluating the possibility of macrophage-mediated delivery in infarcted hearts.

Dipeptide nanostructures: Synthesis, interactions, advantages and biomedical applications

Short peptides are important in the design of self-assembled materials due to their versatility and flexibility. Self-assembled dipeptides, a group of peptide nanostructures, have highly attractive uses in the field of biomedicine. Recently these materials have proved to be important nanostructures because of their biocompatibility, low-cost and simplicity of synthesis, functionality/easy tunability and nano dimensions. Although there are different studies on peptide and protein-based nanostructures, more information about self-assembled nanostructures for dipeptides is still required to discover the advantages, challenges, importance, synthesis, interactions, and applications. This review describes and discusses the self-assembled dipeptide nanostructures especially for biomedical applications.

Nanomaterial-based CT contrast agents and their applications in image-guided therapy

Computed tomography (CT), a diagnostic tool with clinical application, comprehensive coverage, and low cost, is used in hospitals worldwide. However, CT imaging fails to distinguish soft tissues from normal organs and tumors because their mass attenuation coefficients are similar. Various CT contrast agents have been developed in recent years to improve the sensitivity and contrast of imaging. Here, we review the progress of nanomaterial-based CT contrast agents and their applications in image-guided therapy. The CT contrast agents are classified according to their components; gold (Au)-based, bismuth (Bi)-based, lanthanide (Ln)-based, and transition metal (TM)-based nanomaterials are discussed. CT image-guided therapy of diseases, including photothermal therapy (PPT), photodynamic therapy (PDT), chemotherapy, radiotherapy (RT), gas therapy, sonodynamic therapy (SDT), immunotherapy, starvation therapy, gene therapy (GT), and microwave thermal therapy (MWTT), are reviewed. Finally, the perspectives on the CT contrast agents and their biomedical applications are discussed.

Cysteine cathepsins: A long and winding road towards clinics

Biomedical research often focuses on properties that differentiate between diseased and healthy tissue; one of the current focuses is elevated expression and altered localisation of proteases. Among these proteases, dysregulation of cysteine cathepsins can frequently be observed in inflammation-associated diseases, which tips the functional balance from normal physiological to pathological manifestations. Their overexpression and secretion regularly exhibit a strong correlation with the development and progression of such diseases, making them attractive pharmacological targets. But beyond their mostly detrimental role in inflammation-associated diseases, cysteine cathepsins are physiologically highly important enzymes involved in various biological processes crucial for maintaining homeostasis and responding to different stimuli. Consequently, several challenges have emerged during the efforts made to translate basic research data into clinical applications. In this review, we present both physiological and pathological roles of cysteine cathepsins and discuss the clinical potential of cysteine cathepsin-targeting strategies for disease management and diagnosis.

Targeting Ultrasmall Gold Nanoparticles with cRGD Peptide Increases the Uptake and Efficacy of Cytotoxic Payload

Cyclic arginyl-glycyl-aspartic acid peptide (cRGD) peptides show a high affinity towards αVβ3 integrin, a receptor overexpressed in many cancers. We aimed to combine the versatility of ultrasmall gold nanoparticles (usGNP) with the target selectivity of cRGD peptide for the directed delivery of a cytotoxic payload in a novel design. usGNPs were synthesized with a modified Brust-Schiffrin method and functionalized via amide coupling and ligand exchange and their uptake, intracellular trafficking, and toxicity were characterized. Our cRGD functionalized usGNPs demonstrated increased cellular uptake by αVβ3 integrin expressing cells, are internalized via clathrin-dependent endocytosis, accumulated in the lysosomes, and when loaded with mertansine led to increased cytotoxicity. Targeting via cRGD functionalization provides a mechanism to improve the efficacy, tolerability, and retention of therapeutic GNPs.

Multifunctional nanoprobe for real-time in vivo monitoring of T cell activation

Genetically engineered T cells are a powerful new modality for cancer immunotherapy. However, their clinical application for solid tumors is challenging, and crucial knowledge on cell functionality in vivo is lacking. Here, we fabricated a nanoprobe composed of dendrimers incorporating a calcium sensor and gold nanoparticles, for dual-modal monitoring of engineered T cells within a solid tumor. T cells engineered to express a melanoma-specific T-cell receptor and loaded with the nanoprobe were longitudinally monitored within melanoma xenografts in mice. Fluorescent imaging of the nanoprobe's calcium sensor revealed increased intra-tumoral activation of the T cells over time, up to 24 h. Computed tomography imaging of the nanoprobe's gold nanoparticles revealed the cells' intra-tumoral distribution pattern. Quantitative analysis revealed the intra-tumoral T cell quantities. Thus, this nanoprobe reveals intra-tumoral persistence, penetration and functional status of genetically engineered T cells, which can advance T cell-based immunotherapy and promote next-generation live cell imaging.

Structure of Industrial Sacrificial Fragile Cementitious Foams

Sacrificial fragile cementitious foams (SFCFs) act as a core material of the engineered material arresting system (EMAS) installed in airports to enhance the safe take-offs and landings of aircrafts. The foam structures and foaming mechanisms that greatly impact the collapse strength, specific energy, and arresting efficiency of SFCFs, however, have not been fully addressed. Herein, the engineering properties, chemical characteristics, and pore-skeleton structures of three batches of industrial SFCFs were experimentally investigated. Penetration tests showed significant differences in collapse strength and specific energy among the SFCFs with a similar density. Three-dimensional (3D) pore-skeleton structures were resolved by microfocused X-ray computed tomography. The pore-skeleton anisotropy was investigated to uncover the stages of differences in the SFCFs' engineering properties. The results demonstrate that the pore anisotropy rather than the porosity dominates the collapse of cementitious foams. Viscosity-associated nucleation and growth mechanisms were proposed to account for the featured pore-skeleton structures of the SFCFs. The findings would contribute to better pore structure controls of SFCFs toward the improved quality of EMAS.

Title: Advances of Gold Nanoclusters for Bioimaging

Gold nanoclusters (AuNCs) have become a promising material for bioimaging detection because of their tunable photoluminescence, large Stokes shift, low photobleaching, and good biocompatibility. Last decade, great efforts have been made to develop AuNCs for enhanced imaging contrast and multimodal imaging. Herein, an updated overview of recent advances in AuNCs was present for visible fluorescence (FL) imaging, near-infrared fluorescence (NIR-FL) imaging, two-photon near-infrared fluorescence (TP-NIR-FL) imaging, computed tomography (CT) imaging, positron emission tomography (PET) imaging, magnetic resonance imaging (MRI), and photoacoustic (PA) imaging. The justification of AuNCs applied in bioimaging mentioned above applications was discussed, the performance location of different AuNCs were summarized and highlighted in an unified parameter coordinate system of corresponding bioimaging, and the current challenges, research frontiers, and prospects of AuNCs in bioimaging were discussed. This review will bring new insights into the future development of AuNCs in bio-diagnostic imaging.

Targeted Chemoradiotherapy of Prostate Cancer Using Gold Nanoclusters with Protease Activatable Monomethyl Auristatin E

Combined radiotherapy (RT) and chemotherapy are prescribed to patients with advanced prostate cancer (PCa) to increase their survival; however, radiation-related side effects and systematic toxicity caused by chemotherapeutic drugs are unavoidable. To improve the precision and efficacy of concurrent RT and chemotherapy, we have developed a PCa-targeted gold nanocluster radiosensitizer conjugated with a highly potent cytotoxin, monomethyl auristatin E, PSMA-AuNC-MMAE, for RT and chemotherapy of PCa. This approach resulted in enhanced uptake of NCs by PSMA-positive cancer cells, targeted chemotherapy, and increased efficacy of RT both in vitro and in vivo. In addition, the combination of gold and MMAE further increased the efficacy of either of the agents delivered alone or simultaneously but not covalently linked. The PSMA-AuNC-MMAE conjugates improve the specificity and efficacy of radiation and chemotherapy, potentially reducing the toxicity of each therapy and making this an attractive avenue for clinical treatment of advanced PCa.

Molecular Regulation of Polymeric Raman Probes for Ultrasensitive Microtumor Diagnosis and Noninvasive Microvessle Imaging

Raman imaging is a powerful tool for the diagnosis of cancers and visualization of various biological processes. Polymers possessing excellent biocompatibility are promising probes for Raman imaging. However, few polymers are reported to serve as Raman probes for in vivo imaging, mainly due to the intrinsic weak Raman signal intensity and fluorescence interference of these polymers. Herein, a poly(indacenodithiophene-benzothiadiazole) (IDT-BT) polymer is presented, which emits unprecedentedly strong Raman signals under the near-infrared wavelength (785 nm) excitation, thus functioning as a Raman probe for ultrasensitive in vivo Raman imaging. Further mechanistic studies unveil that the unique Raman feature of the IDT-BT polymer relies on molecularly regulating its absorbance edge adjacent to the desired excitation wavelength, thus avoiding fluorescence interference and simultaneously emitting strong Raman scattering under preresonant excitation. Taking advantage of this discipline, the IDT-BT polymeric probe successfully realizes intraoperative Raman imaging of micrometastasis as small as 0.3 mm × 0.3 mm, comparable to the most sensitive Raman probes currently reported. Impressively, the IDT-BT enables noninvasive microvascular imaging, which is not achieved using other Raman probes. This work opens a new avenue toward the development of polymeric Raman probes for in vivo Raman imaging.

Gold Nanoclusters: Imaging, Therapy, and Theranostic Roles in Biomedical Applications

For the past two decades, atomic gold nanoclusters (AuNCs, ultrasmall clusters of several to 100 gold atoms, having a total diameter of <2 nm) have emerged as promising agents in the diagnosis and treatment of cancer. Owing to their small size, significant quantization occurs to their conduction band, which leads to emergent photonic properties and the disappearance of the plasmonic responses observed in larger gold nanoparticles. For example, AuNCs exhibit native luminescent properties, which have been well-explored in the literature. Using proteins, peptides, or other biomolecules as structural scaffolds or capping ligands, required for the stabilization of AuNCs, improves their biocompatibility, while retaining their distinct optical properties. This paved the way for the use of AuNCs in fluorescent bioimaging, which later developed into multimodal imaging combined with computer tomography and magnetic resonance imaging as examples. The development of AuNC-based systems for diagnostic applications in cancer treatment was then made possible by employing active or passive tumor targeting strategies. Finally, the potential therapeutic applications of AuNCs are extensive, having been used as light-activated and radiotherapy agents, as well as nanocarriers for chemotherapeutic drugs, which can be bound to the capping ligand or directly to the AuNCs via different mechanisms. In this review, we present an overview of the diverse biomedical applications of AuNCs in terms of cancer imaging, therapy, and combinations thereof, as well as highlighting some additional applications relevant to biomedical research.

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.

Nanomaterials as Promising Theranostic Tools in Nanomedicine and Their Applications in Clinical Disease Diagnosis and Treatment

In recent decades, with the rapid development of nanotechnology, nanomaterials have been widely used in the medical field, showing great potential due to their unique physical and chemical properties including minimal size and functionalized surface characteristics. Nanomaterials such as metal nanoparticles and polymeric nanoparticles have been extensively studied in the diagnosis and treatment of diseases that seriously threaten human life and health, and are regarded to significantly improve the disadvantages of traditional diagnosis and treatment platforms, such as poor effectiveness, low sensitivity, weak security and low economy. In this review, we report and discuss the development and application of nanomaterials in the diagnosis and treatment of diseases based mainly on published research in the last five years. We first briefly introduce the improvement of several nanomaterials in imaging diagnosis and genomic sequencing. We then focus on the application of nanomaterials in the treatment of diseases, and select three diseases that people are most concerned about and that do the most harm: tumor, COVID-19 and cardiovascular diseases. First, we introduce the characteristics of nanoparticles according to the excellent effect of nanoparticles as delivery carriers of anti-tumor drugs. We then review the application of various nanoparticles in tumor therapy according to the classification of nanoparticles, and emphasize the importance of functionalization of nanomaterials. Second, COVID-19 has been the hottest issue in the health field in the past two years, and nanomaterials have also appeared in the relevant treatment. We enumerate the application of nanomaterials in various stages of viral pathogenesis according to the molecular mechanism of the complete pathway of viral infection, pathogenesis and transmission, and predict the application prospect of nanomaterials in the treatment of COVID-19. Third, aiming at the most important causes of human death, we focus on atherosclerosis, aneurysms and myocardial infarction, three of the most common and most harmful cardiovascular diseases, and prove that nanomaterials could be involved in a variety of therapeutic approaches and significantly improve the therapeutic effect in cardiovascular diseases. Therefore, we believe nanotechnology will become more widely involved in the diagnosis and treatment of diseases in the future, potentially helping to overcome bottlenecks under existing medical methods.

Comparison of Rhenium and Iodine as Contrast Agents in X-Ray Imaging

Purpose

The majority of X-ray contrast agents (XCA) are made with iodine, but iodine-based XCA (I-XCA) exhibit low contrast in high kVp X-rays due to iodine's low atomic number (Z = 53) and K-edge (33.1 keV). While rhenium is a transition metal with a high atomic number (Z = 75) and K-edge (71.7 keV), the utilization of rhenium-based XCA (Re-XCA) in X-ray imaging techniques has not been studied in depth. Our study had two objectives: (1) to compare both the image quality and the absorbed dose of I- and Re-XCA and (2) to prepare and image a rhenium-doped scaffold. Procedures. I- and Re-XCA were prepared and imaged from 50 to 120 kVp by Micro-computed tomography (µCT) and digital radiography and from 120 to 220 kVp by planar X-ray imaging. The scans were repeated using 0.1 to 1.6 mm thick copper filters to harden the X-ray beam. A rhenium-doped scaffold was prepared via electrospinning, used to coat catheters, and imaged at 90 kVp by µCT.

Results

I-XCA have a greater contrast-to-noise ratio (CNR) at 50 and 80 kVp, but Re-XCA have a greater CNR at >120 kVp. The difference in CNR is increased as the thickness of the copper filters is increased. For instance, the percent CNR improvement of rhenium over iodine is 14.2% with a 0.6 mm thick copper filter, but it is 59.1% with a 1.6 mm thick copper filter, as shown at 120 kVp by µCT. Upon coating them with a rhenium-doped scaffold, the catheters became radiopaque.

Conclusions

Using Monte Carlo simulations, we showed that it is possible to reduce the absorbed dose of high kVp X-rays while allowing the acquisition of high-quality images. Furthermore, radiopaque catheters have the potential of enhancing the contrast during catheterizations and helping physicians to place catheters inside patients more rapidly and precisely.

Thin Layer-Protected Gold Nanoparticles for Targeted Multimodal Imaging with Photoacoustic and CT

The large size of nanoparticles prevents rapid extravasation from blood vessels and diffusion into tumors. Multimodal imaging uses the physical properties of one modality to validate the results of another. We aim to demonstrate the use of a targeted thin layer-protected ultra-small gold nanoparticles (Au-NPs) to detect cancer in vivo using multimodal imaging with photoacoustic and computed tomography (CT). The thin layer was produced using a mixed thiol-containing short ligands, including MUA, CVVVT-ol, and HS-(CH2)₁₁-PEG₄-OH. The gold nanoparticle was labeled with a heterobivalent (HB) peptide ligand that targets overexpression of epidermal growth factor receptors (EGFR) and ErbB2, hereafter HB-Au-NPs. A human xenograft model of esophageal cancer was used for imaging. HB-Au-NPs show spherical morphology, a core diameter of 4.47 ± 0.8 nm on transmission electron microscopy, and a hydrodynamic diameter of 6.41 ± 0.73 nm on dynamic light scattering. Uptake of HB-Au-NPs was observed only in cancer cells that overexpressed EGFR and ErbB2 using photoacoustic microscopy. Photoacoustic images of tumors in vivo showed peak HB-Au-NPs uptake at 8 h post-injection with systemic clearance by ~48 h. Whole-body images using CT validated specific tumor uptake of HB-Au-NPs in vivo. HB-Au-NPs showed good stability and biocompatibility with fast clearance and contrast-enhancing capability for both photoacoustic and CT imaging. A targeted thin layer-protected gold nanoprobe represents a new platform for molecular imaging and shows promise for early detection and staging of cancer.

Chemodynamic nanomaterials for cancer theranostics

It is of utmost urgency to achieve effective and safe anticancer treatment with the increasing mortality rate of cancer. Novel anticancer drugs and strategies need to be designed for enhanced therapeutic efficacy. Fenton- and Fenton-like reaction-based chemodynamic therapy (CDT) are new strategies to enhance anticancer efficacy due to their capacity to generate reactive oxygen species (ROS) and oxygen (O2). On the one hand, the generated ROS can damage the cancer cells directly. On the other hand, the generated O2 can relieve the hypoxic condition in the tumor microenvironment (TME) which hinders efficient photodynamic therapy, radiotherapy, etc. Therefore, CDT can be used together with many other therapeutic strategies for synergistically enhanced combination therapy. The antitumor applications of Fenton- and Fenton-like reaction-based nanomaterials will be discussed in this review, including: (iþ) producing abundant ROS in-situ to kill cancer cells directly, (ii) enhancing therapeutic efficiency indirectly by Fenton reaction-mediated combination therapy, (iii) diagnosis and monitoring of cancer therapy. These strategies exhibit the potential of CDT-based nanomaterials for efficient cancer therapy.

Nanotechnology for Cancer Imaging: Advances, Challenges, and Clinical Opportunities

Nanoparticle (NP) imaging applications have the potential to improve cancer diagnostics, therapeutics, and treatment management. In biomedical research and clinical practice, NPs can serve as labels or labeled carriers for monitoring drug delivery or serve as imaging agents for enhanced imaging contrast, as well as providing improved signal sensitivity and specificity for in vivo imaging of molecular and cellular processes. These qualities offer exciting opportunities for NP-based imaging agents to address current limitations in oncologic imaging. Despite substantial advancements in NP design and development, very few NP-based imaging agents have translated into clinics within the past 5 years. This review highlights some promising NP-enabled imaging techniques and their potential to address current clinical cancer imaging limitations. Although most examples provided herein are from the preclinical space, discussed imaging solutions could offer unique in vivo tools to solve biologic questions, improve cancer treatment effectiveness, and inspire clinical translation innovation to improve patient care. Keywords: Molecular Imaging-Cancer, Molecular Imaging-Nanoparticles, Molecular Imaging-Optical Imaging, Metastases, Oncology, Surgery, Treatment Effects.

Recent Development of Gold Nanoparticles as Contrast Agents for Cancer Diagnosis

The last decade has witnessed the booming of preclinical studies of gold nanoparticles (AuNPs) in biomedical applications, from therapeutics delivery, imaging diagnostics, to cancer therapies. The synthetic versatility, unique optical and electronic properties, and ease of functionalization make AuNPs an excellent platform for cancer theranostics. This review summarizes the development of AuNPs as contrast agents to image cancers. First, we briefly describe the AuNP synthesis, their physical characteristics, surface functionalization and related biomedical uses. Then we focus on the performances of AuNPs as contrast agents to diagnose cancers, from magnetic resonance imaging, CT and nuclear imaging, fluorescence imaging, photoacoustic imaging to X-ray fluorescence imaging. We compare these imaging modalities and highlight the roles of AuNPs as contrast agents in cancer diagnosis accordingly, and address the challenges for their clinical translation.

The Tumor Proteolytic Landscape: A Challenging Frontier in Cancer Diagnosis and Therapy

In recent decades, dysregulation of proteases and atypical proteolysis have become increasingly recognized as important hallmarks of cancer, driving community-wide efforts to explore the proteolytic landscape of oncologic disease. With more than 100 proteases currently associated with different aspects of cancer development and progression, there is a clear impetus to harness their potential in the context of oncology. Advances in the protease field have yielded technologies enabling sensitive protease detection in various settings, paving the way towards diagnostic profiling of disease-related protease activity patterns. Methods including activity-based probes and substrates, antibodies, and various nanosystems that generate reporter signals, i.e., for PET or MRI, after interaction with the target protease have shown potential for clinical translation. Nevertheless, these technologies are costly, not easily multiplexed, and require advanced imaging technologies. While the current clinical applications of protease-responsive technologies in oncologic settings are still limited, emerging technologies and protease sensors are poised to enable comprehensive exploration of the tumor proteolytic landscape as a diagnostic and therapeutic frontier. This review aims to give an overview of the most relevant classes of proteases as indicators for tumor diagnosis, current approaches to detect and monitor their activity in vivo, and associated therapeutic applications.

Functional CT Contrast Nanoagents for the Tumor Microenvironment

Understanding the detailed tumor microenvironment (TME) is essential to achieve effective treatment of tumor, because TME has an extremely profound influence on the occurrence, development, invasion, and metastasis of tumor. It is of great significance to realize accurate diagnosis of the TME by using functional computed tomography (CT) contrast nanoagents (FCTNAs). Here, an overview of FCTNAs that respond to the overexpressed receptors, acidic microenvironment, overexpressed glutathione and enzymes, and hypoxia in tumor is provided, and also prospects the advance of novel spectral CT technique to detect the TME precisely. Utilizing FCTNAs is expected to achieve accurate monitoring of the TME and further provide guidance for the effective personalized tumor treatment in clinic.

Nanoparticles Yield Increased Drug Uptake and Therapeutic Efficacy upon Sequential Near-Infrared Irradiation

Nanoparticles offer great opportunities for precision medicine. However, the use of nanoparticles as smart photosensitizers that target tumor biomarkers and are responsive to the tumor microenvironment has yet to be explored. Herein, prostate cancer (PCa)-selective theranostic gold nanoparticles (AuNPs) for precise cancer imaging and therapy are developed. Silicon phthalocyanine, Pc158, was synthesized and deactivated by conjugating it to AuNPs via a biocleavable linker. In vitro and in vivo, the targeted AuNPs show excellent selectivity for PSMA-positive tumor cells. Triggered release of the therapeutic, Pc158, followed by sequential photodynamic therapy (PDT) results in significant inhibition of tumor growth. Further, we demonstrate that multiple sequential PDT greatly enhances nanoparticle uptake and therapeutic efficacy. PSMA is highly expressed in the neovasculature of most other solid tumors in humans, as well as PCa, making this approach of great practical interest for precision PDT in a wide range of cancers.

Advances in Medical Imaging: Aptamer- and Peptide-Targeted MRI and CT Contrast Agents

Computed tomography (CT) and magnetic resonance imaging (MRI) are among the most well-established modalities in the field of noninvasive medical imaging. Despite being powerful tools, both suffer from a number of limitations and often fall short when it comes to full delineation of pathological tissues. Since its conception, molecular imaging has been commonly utilized to further the understanding of disease progression, as well as monitor treatment efficacy. This has naturally led to the advancement of the field of targeted imaging. Targeted imaging research is currently dominated by ligand-modified contrast media for applications in MRI and CT imaging. Although a plethora of targeting ligands exist, a fine balance between their size and target binding efficiency must be considered. This review will focus on aptamer- and peptide-modified contrast agents, outlining selected formulations developed in recent years while highlighting the advantages offered by these targeting ligands.

Peptide and protein modified metal clusters for cancer diagnostics

The biomedical features of metal clusters have been explored in tumor diagnostic applications in recent years. Peptide or protein protected metal clusters with low toxicity, ultra-small size and good biocompatibility are ideal bioanalytical tools, and exhibit better cancer diagnostic properties that have been attractive to oncologists. This perspective provides a rigorous but succinct overview of cancer diagnosis as a working concept for metal clusters by reporting the latest significant advances in the applications of metal clusters in tumor-related bioanalysis and diagnosis. The materials design principles, bioanalytical mechanisms and biomedical applications of metal clusters are described, and then the potential challenges and prospects of metal clusters in cancer diagnosis are discussed. A perspective addressing the role of metal clusters in this field is required to understand their effects and functions, as well as for the scientific community to further advance the development of metal clusters for broader diagnostic applications.

Interactions Between Tumor Biology and Targeted Nanoplatforms for Imaging Applications

Although considerable efforts have been conducted to diagnose, improve, and treat cancer in the past few decades, existing therapeutic options are insufficient, as mortality and morbidity rates remain high. Perhaps the best hope for substantial improvement lies in early detection. Recent advances in nanotechnology are expected to increase the current understanding of tumor biology, and will allow nanomaterials to be used for targeting and imaging both in vitro and in vivo experimental models. Owing to their intrinsic physicochemical characteristics, nanostructures (NSs) are valuable tools that have received much attention in nanoimaging. Consequently, rationally designed NSs have been successfully employed in cancer imaging for targeting cancer-specific or cancer-associated molecules and pathways. This review categorizes imaging and targeting approaches according to cancer type, and also highlights some new safe approaches involving membrane-coated nanoparticles, tumor cell-derived extracellular vesicles, circulating tumor cells, cell-free DNAs, and cancer stem cells in the hope of developing more precise targeting and multifunctional nanotechnology-based imaging probes in the future.

New insights into the synthesis, toxicity and applications of gold nanoparticles in CT imaging and treatment of cancer

The past decades have witnessed enormous development of gold nanoparticles (AuNPs) and their applications in the biomedical field, an area in which they show infinite potential. Abundant investigations have been conducted in improving AuNP synthesis, aimed at obtaining water-dispersible ultrasmall AuNPs, which can exhibit biocompatibility, renal clearance and minimal toxicity. Due to their excellent x-ray attenuation ability, special optical properties and surface modification properties, AuNPs are reported to be promising as computed tomography contrast agents and can be applied in radiotherapy, photothermal and photodynamic therapies, and drug delivery. In this review, synthesis methods and toxicity of AuNPs have been summarized, emphasizing the preparation of ultra-small AuNPs. Applications of AuNPs in computed tomography imaging and cancer treatment are also considered, revealing their potential in the clinic.

Cysteine cathepsins as therapeutic targets in inflammatory diseases

Introduction: Cysteine cathepsins are involved in the development and progression of numerous inflammation-associated diseases such as cancer, arthritis, bone and immune disorders. Consequently, there is a drive to progress research efforts focused on cathepsin use in diagnostics and as therapeutic targets in disease.Areas covered: This review discusses the potential of cysteine cathepsins as therapeutic targets in inflammation-associated diseases and recent advances in preclinical and clinical research. We describe direct targeting of cathepsins for treatment purposes and their indirect use in diagnostics.Expert opinion: The targeting of cysteine cathepsins has not translated into the clinic; this failure is attributed to off- and on-target side effects and/or the lack of companion biomarkers. This field now embraces developments in diagnostic imaging, the activation of prodrugs and antibody-drug conjugates for targeted drug delivery. The future lies in improved molecular tools and therapeutic concepts that will find a wide spectrum of uses in diagnostic and therapeutic applications.

Prostate-specific membrane antigen targeted gold nanoparticles for prostate cancer radiotherapy: does size matter for targeted particles?

Since the introduction of PSA testing, significantly more men have been diagnosed and treated for prostate cancer. Localized prostate cancer typically is treated with prostatectomy, however there is still a high risk of recurrence after surgery, and adjuvant radiation has been shown to mitigate disease progression. X-ray therapy is frequently used as an adjuvant to treat prostate cancer, but is an imperfect tool. In this report we describe the development of a targeted-radiosensitizing nanoparticle that significantly improves X-ray therapy. Taking advantage of the demonstrated radiosensitizing activity of gold nanoparticles (AuNPs) we developed targeted AuNPs and varied both surface ligand density and AuNP size to develop an optimized AuNP for X-ray radiotherapy. We conjugated a prostate-specific membrane antigen (PSMA) targeting ligand, PSMA-1, to AuNPs and found that the targeting ligand dramatically improved gold uptake by PSMA-expressing PC3pip cells compared with PC3flu cells lacking the PSMA receptors. Further, enhancement of radiotherapy was significantly more pronounced by internalization of smaller PSMA targeted-AuNPs. Our studies provide a foundation for design of size-selected AuNPs for targeted radiotherapy and, for the first time, systematically investigate both the effect of ligand and AuNP size on the cell uptake, tumor targeting and radiotherapy efficacy.

A Theranostic Cathepsin Activity-Based Probe for Noninvasive Intervention in Cardiovascular Diseases

Despite the common use of lipid-lowering medications, cardiovascular diseases continue to be a significant health concern. Atherosclerosis, one of the most frequent causes of cardiovascular morbidity, involves extensive inflammatory activity and remodeling of the vascular endothelium. This relentless inflammatory condition can ultimately give rise to clinical manifestations, such as ischemic heart disease or stroke. Accumulating evidence over the past decades implicates cysteine protease cathepsins in cardiovascular disorders. In particular, Cathepsins B, L, and S are over-expressed during vascular inflammation, and their activity is associated with impaired clinical outcomes. Here we took advantage of these molecular events to introduce a non-invasive detection and treatment approach to modulate vascular inflammation using a Photosensitizing quenched Activity-Based Probed (PS-qABP) that targets these proteases. Methods: We tested the application of this approach in LDL receptor-deficient mice and used non-invasive imaging and heart cross-section staining to assess the theranostic efficacy of this probe. Moreover, we used fresh human endarterectomy tissues to analyze cathepsin signals on gel, and verified cathepsin identity by mass spectrometry. Results: We showed that our PS-qABP can rapidly accumulate in areas of inflammatory atheromas in vivo, and application of light therapy profoundly reduced lesional immune cell content without affecting smooth muscle cell and collagen contents. Lastly, using human tissue samples we provided proof-of-concept for future clinical applications of this technology. Conclusions: Photodynamic therapy guided by cysteine cathepsin activity is an effective approach to reduce vascular inflammation and attenuate atherosclerosis progression. This approach could potentially be applied in clinical settings.

Targeted Gold Nanocluster-Enhanced Radiotherapy of Prostate Cancer

For over a hundred years, X-rays have been a main component of the radiotherapeutic approaches to treat cancer. Yet, to date, no radiosensitizer has been developed to selectively target prostate cancer. Gold has excellent X-ray absorptivity and is used as a radiotherapy enhancing material. In this work, ultrasmall Au25 nanoclusters (NCs) are developed for selective prostate cancer targeting, radiotherapy enhancement, and rapid clearance from the body. Targeted-Au25 NCs are rapidly and selectively taken up by prostate cancer in vitro and in vivo and also have fast renal clearance. When combined with X-ray irradiation of the targeted cancer tissues, radiotherapy is significantly enhanced. The selective targeting and rapid clearance of the nanoclusters may allow reductions in radiation dose, decreasing exposure to healthy tissue and making them highly attractive for clinical translation.

Gram-scale fabrication of Bi@C nanoparticles through one-step hydrothermal method for dual-model imaging-guided NIR-II photothermal therapy

At present, increasing attention is being paid to photothermal therapy corresponding to the second near infrared (NIR-II) range (1000-1700 nanometers); however, its biomedical applications related to carbon-based nanomaterials (CNMs) have always been limited by the large-scale fabrication of excellent diagnostic probes with a suitable size and optical absorption cross-section. Herein, we successfully prepared Bi@C nanoparticles with a suitable size and high output (3.14 g per patch) through a one-pot hydrothermal method. By combining Bi with carbon, the optical absorption in the NIR-II range was enhanced compared to that for single carbon; moreover, Bi@C could no longer be easily oxidized due to the protection of outer C compared with individual Bi. Furthermore, because of the high atomic number of Bi (Z = 83), the Bi@C nanoparticles exhibited computed imaging contrast properties. According to the in vitro and in vivo experiments, the Bi@C nanoparticles could ablate cancer cells under illumination with a 1064 nm laser with deeper penetration and an appropriate permissible exposure (MPE) to the laser (1 W cm^-2), showing excellent performance for the diagnosis and treatment of tumors. This study provides a simple method to synthesize metal-carbon nanocomposites to enhance the NIR-II optical absorption efficiency for effective deep-seated tumor photothermal therapy and will further broaden the applications of CNMs.

X-ray-activated nanosystems for theranostic applications

X-rays are widely applied in clinical medical facilities for radiotherapy (RT) and biomedical imaging. However, the sole use of X-rays for cancer treatment leads to insufficient radiation energy deposition due to the low X-ray attenuation coefficients of living tissues and organs, producing unavoidable excessive radiation doses with serious side effects to healthy body parts. Over the past decade, developments in materials science and nanotechnology have led to rapid progress in the field of X-ray-activated tumor-targeting nanosystems, which are able to tackle even systemic tumors and relieve the burden of exposure to large radiation doses. Additionally, novel imaging contrast agents and techniques have also been developed. In comparison with conventional external light sources (e.g., near infrared), the X-ray technique is ideal for the activation of nanosystems for cancer treatment and biomedical imaging applications due to its nearly unlimited penetration depth in living tissues and organisms. In this review, we systematically describe the interaction mechanisms between X-rays and nanosystems, and provide an overview of X-ray-sensitive materials and the recent progress on X-ray-activated nanosystems for cancer-associated theranostic applications.