Pd nanosheets with their surface coordinated by radioactive iodide as a high-performance theranostic nanoagent for orthotopic hepatocellular carcinoma imaging and cancer therapy

Exploring innovative strides in radiolabeled nanoparticle progress for multimodality cancer imaging and theranostic applications

Multimodal imaging unfolds as an innovative approach that synergistically employs a spectrum of imaging techniques either simultaneously or sequentially. The integration of computed tomography (CT), magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT), positron emission tomography (PET), and optical imaging (OI) results in a comprehensive and complementary understanding of complex biological processes. This innovative approach combines the strengths of each method and overcoming their individual limitations. By harmoniously blending data from these modalities, it significantly improves the accuracy of cancer diagnosis and aids in treatment decision-making processes. Nanoparticles possess a high potential for facile functionalization with radioactive isotopes and a wide array of contrast agents. This strategic modification serves to augment signal amplification, significantly enhance image sensitivity, and elevate contrast indices. Such tailored nanoparticles constructs exhibit a promising avenue for advancing imaging modalities in both preclinical and clinical setting. Furthermore, nanoparticles function as a unified nanoplatform for the co-localization of imaging agents and therapeutic payloads, thereby optimizing the efficiency of cancer management strategies. Consequently, radiolabeled nanoparticles exhibit substantial potential in driving forward the realms of multimodal imaging and theranostic applications. This review discusses the potential applications of molecular imaging in cancer diagnosis, the utilization of nanotechnology-based radiolabeled materials in multimodal imaging and theranostic applications, as well as recent advancements in this field. It also highlights challenges including cytotoxicity and regulatory compliance, essential considerations for effective clinical translation of nanoradiopharmaceuticals in multimodal imaging and theranostic applications.

Methods for Radiolabeling Nanoparticles (Part 3): Therapeutic Use

Following previously published systematic reviews on the diagnostic use of nanoparticles (NPs), in this manuscript, we report published methods for radiolabeling nanoparticles with therapeutic alpha-emitting, beta-emitting, or Auger's electron-emitting isotopes. After analyzing 234 papers, we found that different methods were used with the same isotope and the same type of nanoparticle. The most common type of nanoparticles used are the PLGA and PAMAM nanoparticles, and the most commonly used therapeutic isotope is 177Lu. Regarding labeling methods, the direct encapsulation of the isotope resulted in the most reliable and reproducible technique. Radiolabeled nanoparticles show promising results in metastatic breast and lung cancer, although this field of research needs more clinical studies, mainly on the comparison of nanoparticles with chemotherapy.

Nanoparticles in Cancer Diagnosis and Treatment

The use of tailored medication delivery in cancer treatment has the potential to increase efficacy while decreasing unfavourable side effects. For researchers looking to improve clinical outcomes, chemotherapy for cancer continues to be the most challenging topic. Cancer is one of the worst illnesses despite the limits of current cancer therapies. New anticancer medications are therefore required to treat cancer. Nanotechnology has revolutionized medical research with new and improved materials for biomedical applications, with a particular focus on therapy and diagnostics. In cancer research, the application of metal nanoparticles as substitute chemotherapy drugs is growing. Metals exhibit inherent or surface-induced anticancer properties, making metallic nanoparticles extremely useful. The development of metal nanoparticles is proceeding rapidly and in many directions, offering alternative therapeutic strategies and improving outcomes for many cancer treatments. This review aimed to present the most commonly used nanoparticles for cancer applications.

Rational N,P-Codoped pH-Activatable Red Carbon Dot for In Vitro and In Vivo Tumor Imaging

Tumor detection and imaging via tumor microenvironmental indicators can have practical value. Here, a low-pH-responsive red carbon dot (CD) was prepared via a hydrothermal reaction for specific tumor imaging in vitro and in vivo. The probe responded to the acidic tumor microenvironment. The CDs are codoped by nitrogen and phosphorene and contain anilines on the surface. These anilines are efficient electron donors and modulate the pH response: Fluorescence is undetectable at common physical pH (>7.0), but red fluorescence (600-720 nm) increases with decreasing pH. The inactivation of fluorescence is due to three aspects: photoinduced electron transfer from anilines, deprotonation-induced energy states changing, and particle aggregation-induced quenching. It is believed that this pH-responsive character of CD is better than other reported CDs. Thus, in vitro images of HeLa cells show strong fluorescence that is 4-fold higher than normal cells. Subsequently, the CDs are used for in vivo imaging of tumors in mice. Tumors can be clearly observed within 1 h, and clearance of CDs will be finished within 24 h due to the small size of the CDs. The CDs offer excellent tumor-to-normal tissue (T/N) ratios and have great potential for biomedical research and disease diagnosis.

Plasmonic nanotechnology for photothermal applications - an evaluation

The application of plasmonic nanoparticles is motivated by the phenomenon of surface plasmon resonance. Owing to the tunability of optothermal properties and enhanced stability, these nanostructures show a wide range of applications in optical sensors, steam generation, water desalination, thermal energy storage, and biomedical applications such as photothermal (PT) therapy. The PT effect, that is, the conversion of absorbed light to heat by these particles, has led to thriving research regarding the utilization of plasmonic nanoparticles for a myriad of applications. The design of conventional nanomaterials for PT conversion has focussed predominantly on the manipulation of photon absorption through bandgap engineering, doping, incorporation, and modification of suitable matrix materials. Plasmonic nanomaterials offer an alternative and attractive approach in this regard, through the flexibility in the excitation of surface plasmons. Specific advantages are the considerable improved bandwidth of the absorption, a higher efficiency of photon absorption, facile tuning, as well as flexibility in the synthesis of plasmonic nanomaterials. This review of plasmonic PT (PPT) research begins with a theoretical discussion on the plasmonic properties of nanoparticles by means of the quasi-static approximation, Mie theory, Gans theory, generic simulations on common plasmonic material morphologies, and the evaluation processes of PT performance. Further, a variety of nanomaterials and material classes that have potential for PPT conversion are elucidated, such as plasmonic metals, bimetals, and metal-metal oxide nanocomposites. A detailed investigation of the essential, but often ignored, concept of thermal, chemical, and aggregation stability of nanoparticles is another part of this review. The challenges that remain, as well as prospective directions and chemistries, regarding nanomaterials for PT conversion are pondered on in the final section of the article, taking into account the specific requirements from different applications.

Radiolabeled nanomaterial for cancer diagnostics and therapeutics: principles and concepts

In the last three decades, radiopharmaceuticals have proven their effectiveness for cancer diagnosis and therapy. In parallel, the advances in nanotechnology have fueled a plethora of applications in biology and medicine. A convergence of these disciplines has emerged more recently with the advent of nanotechnology-aided radiopharmaceuticals. Capitalizing on the unique physical and functional properties of nanoparticles, radiolabeled nanomaterials or nano-radiopharmaceuticals have the potential to enhance imaging and therapy of human diseases. This article provides an overview of various radionuclides used in diagnostic, therapeutic, and theranostic applications, radionuclide production through different techniques, conventional radionuclide delivery systems, and advancements in the delivery systems for nanomaterials. The review also provides insights into fundamental concepts necessary to improve currently available radionuclide agents and formulate new nano-radiopharmaceuticals.

Advances in Single-component inorganic nanostructures for photoacoustic imaging guided photothermal therapy

Phototheranostic based on photothermal therapy (PTT) and photoacoustic imaging (PAI), as one of avant-garde medical techniques, have sparked growing attention because it allows noninvasive, deeply penetrative, and highly selective and effective therapy. Among a variety of phototheranostic nanoagents, single-component inorganic nanostructures are found to be novel and attractive PAI and PTT combined nanotheranostic agents and received tremendous attention, which not only exhibit structural controllability, high tunability in physiochemical properties, size-dependent optical properties, high reproducibility, simple composition, easy functionalization, and simple synthesis process, but also can be endowed with multiple therapeutic and imaging functions, realizing the superior therapy result along with bringing less foreign materials into body, reducing systemic side effects and improving the bioavailability. In this review, according to their synthetic components, conventional single-component inorganic nanostructures are divided into metallic nanostructures, metal dichalcogenides, metal oxides, carbon based nanostructures, upconversion nanoparticles (UCNPs), metal organic frameworks (MOFs), MXenes, graphdiyne and other nanostructures. On the basis of this category, their detailed applications in PAI guide PTT of tumor treatment are systematically reviewed, including synthesis strategies, corresponding performances, and cancer diagnosis and therapeutic efficacy. Before these, the factors to influence on photothermal effect and the principle of in vivo PAI are briefly presented. Finally, we also comprehensively and thoroughly discussed the limitation, potential barriers, future perspectives for research and clinical translation of this single-component inorganic nanoagent in biomedical therapeutics.

Nanotechnology in the Diagnostic and Therapy of Hepatocellular Carcinoma

Hepatocellular carcinoma is the most common liver malignancy and is among the top five most common cancers. Despite the progress of surgery and chemotherapy, the results are often disappointing, in part due to chemoresistance. This type of tumor has special characteristics that allow the improvement of diagnostic and treatment techniques used in clinical practice, by combining nanotechnology. This article presents a brief review of the literature focused on nano-conditioned diagnostic methods, targeted therapy, and therapeutic implications for the pathology of hepatocellular carcinoma. Within each subdomain, several modern technologies with significant impact were highlighted: serological, imaging, or histopathological diagnosis; intraoperative detection; carrier-type nano-conditioned therapy, thermal ablation, and gene therapy. The prospects offered by nanomedicine will strengthen the hope of more efficient diagnoses and therapies in the future.

Two-Dimensional Nanomaterial-based catalytic Medicine: Theories, advanced catalyst and system design

Two-dimensional nanomaterial-based catalytic medicines that associate the superiorities of novel catalytic mechanisms with nanotechnology have emerged as absorbing therapeutic strategies for cancer therapy. Catalytic medicines featuring high efficiency and selectivity have been widely used as effective anticancer strategies without applying traditional nonselective and highly toxic chemodrugs. Moreover, two-dimensional nanomaterials are characterized by distinctive physicochemical properties, such as a sizeable bandgap, good conductivity, fast electron transfer and photoelectrochemical activity. The introduction of two-dimensional nanomaterials into catalytic medicine provides a more effective, controllable, and precise antitumor strategy. In this review, different types of two-dimensional nanomaterial-based catalytic nanomedicines are generalized, and their catalytic theories, advanced catalytic pathways and catalytic nanosystem design are also discussed in detail. Notably, future challenges and obstacles in the design and further clinical transformation of two-dimensional nanomaterial-based catalytic nanomedicine are prospected.

Novel Water-Soluble Phthalocyanine-Based Small Molecule for Effective NIR Triggered Dual Phototherapy of Cancer

Photothermal therapy (PTT) synergized photodynamic therapy (PDT) indicates more hopeful future of clinical application and is of significant importance for cancer theranostic compared with monotherapy. Dual phototherapy is attracting increasing...

Recent advances in hepatocellular carcinoma therapeutic strategies and imaging-guided treatment

Hepatocellular carcinoma (HCC) is one of the most common malignant cancer in the world, which greatly threatens human health. However, the routine treatment strategies for HCC have failed to specifically eradicate the tumorigenic cells, leading to the occurrence of metastasis and recurrence. To improve treatment efficacies, the development of novel effective technologies is urgently required. Recently, nanotechnologies have gained the extensive attention in cancer targeted therapy, which could provide a promising way for HCC clinical practice. However, a successful cancer management depends on accurate diagnosis of the tumour along with precise therapeutic protocol, thereby predicting the tumour response to existing therapies. The synergistic effect of targeted therapeutic systems and imaging approaches (also called 'imaging-guided cancer treatment') may establish a more effective platform for individual cancer care. This review outlines the recent advanced nano-targeted and -traceable therapeutic strategies for HCC management. The multifunctional nano agents that have both diagnosis and therapy abilities are highlighted. Finally, we conclude with our perspectives on the future development and challenges of HCC nanotheranostics.

Molecular Imaging of Tumor Microenvironment to Assess the Effects of Locoregional Treatment for Hepatocellular Carcinoma

Liver cancer is one of the leading causes of cancer deaths worldwide. Among all primary liver cancers, hepatocellular carcinoma (HCC) is the most common type, representing 75%‐85% of all primary liver cancer cases. Median survival following diagnosis of HCC is approximately 6 to 20 months due to late diagnosis in its course and few effective treatment options. Interventional therapy with minimal invasiveness is recognized as a promising treatment for HCC. However, due to the heterogeneity of HCC and the complexity of the tumor microenvironment, the long‐term efficacy of treatment for HCC remains a challenge in the clinic. Tumor microenvironment, including factors such as hypoxia, angiogenesis, low extracellular pH, interstitial fluid pressure, aerobic glycolysis, and various immune responses, has emerged as a key contributor to tumor residual and progression after locoregional treatment for HCC. New approaches to noninvasively assess the treatment response and assist in the clinical decision‐making process are therefore urgently needed. Molecular imaging tools enabling such an assessment may significantly advance clinical practice by allowing real‐time optimization of treatment protocols for the individual patient. This review discusses recent advances in the application of molecular imaging technologies for noninvasively assessing changes occurring in the microenvironment of HCC after locoregional treatment.

Semiconducting polymer nano-radiopharmaceutical for combined radio-photothermal therapy of pancreatic tumor

Background

Pancreatic ductal adenocarcinoma (PDAC) is a devastatingly malignant tumor with a high mortality. However, current strategies to treat PDAC generally have low efficacy and high side-effects, therefore, effective treatment against PDAC remains an urgent need.

Results

We report a semiconducting polymer nano-radiopharmaceutical with intrinsic photothermal capability and labeling with therapeutic radioisotope ¹⁷⁷Lu (¹⁷⁷Lu-SPN-GIP) for combined radio- and photothermal therapy of pancreatic tumor. ¹⁷⁷Lu-SPN-GIP endowed good stability at physiological conditions, high cell uptake, and long retention time in tumor site. By virtue of combined radiotherapy (RT) and photothermal therapy (PTT), ¹⁷⁷Lu-SPN-GIP exhibited enhanced therapeutic capability to kill cancer cells and xenograft tumor in living mice compared with RT or PTT alone. More importantly, ¹⁷⁷Lu-SPN-GIP could suppress the growth of the tumor stem cells and reverse epithelial mesenchymal transition (EMT), which may greatly reduce the occurrence of metastasis.

Conclusion

Such strategy we developed could improve therapeutic outcomes over traditional RT as it is able to ablate tumor with relatively lower doses of radiopharmaceuticals to reduce its side effects.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01083-0.

Palladium nanoplates scotch breast cancer lung metastasis by constraining epithelial-mesenchymal transition

Metastasis accounts for the majority of cancer deaths in many tumor types including breast cancer. Epithelial-mesenchymal transition (EMT) is the driving force for the occurrence and progression of metastasis, however, no targeted strategies to block the EMT program are currently available to combat metastasis. Diverse engineered nanomaterials (ENMs) have been reported to exert promising anti-cancer effects, however, no ENMs have been designed to target EMT. Palladium (Pd) nanomaterials, a type of ENM, have received substantial attention in nanomedicine due to their favorable photothermal performance for cancer therapeutics. Herein, Pd nanoplates (PdPL) were found to be preferentially biodistributed to both primary tumors and metastatic tumors. Importantly, PdPL showed a significant inhibition of lung metastasis with and without near-infrared (NIR) irradiation. Mechanistic investigations revealed that EMT was significantly compromised in breast cancer cells upon the PdPL treatment, which was partially due to the inhibition of the transforming growth factor-beta (TGF-β) signaling. Strikingly, the PdPL was found to directly interact with TGF-β proteins to diminish TGF-β functions in activating its downstream signaling, as evidenced by the reduced phosphorylation of Smad2. Notably, TGF-β-independent pathways were also involved in undermining EMT and other important biological processes that are necessary for metastasis. Additionally, NIR irradiation elicited synergistic effects on PdPL-induced inhibition of primary tumors and metastasis. In summary, these results revealed that the PdPL remarkably curbed metastasis by inhibiting EMT signaling, thereby indicating the promising potential of PdPL as a therapeutic agent for treating breast cancer metastasis.

Alkaline phosphatase-triggered self-assembly of near-infrared nanoparticles for the enhanced photoacoustic imaging of tumors

In this chapter, we discuss the need for the development of enzyme-activatable probes in the field of tumor-targeted photoacoustic (PA) imaging, then we give a brief description of the innovation of designing alkaline phosphatase (ALP)-activatable probes for PA imaging. After that, we provide detailed protocols for the syntheses and characterizations of a near-infrared photoacoustic imaging probe, 1P, developed in our research group. With this tool, 1P could form nanoparticles 1-NPs under the catalysis of ALP and thus could be used to enhance PA imaging both in vitro and in vivo.

The cellular immunotherapy of integrated photothermal anti-oxidation Pd-Se nanoparticles in inhibition of the macrophage inflammatory response in rheumatoid arthritis

Reducing the inflammatory response is a major goal in the therapy of rheumatoid arthritis (RA). Herein, we integrated palladium nanoparticles (Pd NPs) with selenium nanoparticles (Se NPs) and obtained a multiple nanosystem (Pd@Se-HA NPs) that could simultaneously scavenge hydroxyl radicals (⋅OH) and provide a photothermal effect. The Pd@Se-HA NPs were constructed by a simple self-assembly method in which Se NPs were electrostatically bonded to Pd NPs; hyaluronic acid (HA) was linked to the NPs by ester bonding to provide macrophage targeting ability. The experiments show that the combined therapy of eliminating ⋅OH with Se NPs and utilizing PTT with Pd NPs could effectively reduce the inflammatory response in macrophages more effectively than either individual NP treatment. In addition, the outer layer of HA could specifically target the CD44 receptor to enhance the accumulation of Pd@Se NPs at the lesion, further enhancing the therapeutic effect. After treatment for 15 days, the Pd@Se-HA NPs nearly eliminated the inflammatory response in the joints of mice in an induced RA model, and prevented joint damage and degradation.

Biomaterial-mediated internal radioisotope therapy

Radiation therapy (RT), including external beam radiotherapy (EBRT) and internal radioisotope therapy (RIT), has been an indispensable strategy for cancer therapy in clinical practice in recent years. Ionized atoms and free radicals emitted from the nucleus of radioisotopes can cleave a single strand of DNA, inducing the apoptosis of cancer cells. Thus far, nuclides used for RIT could be classified into three main types containing alpha (α), beta (β), and Auger particle emitters. In order to enhance the bioavailability and reduce the physiological toxicity of radioisotopes, various biomaterials have been utilized as multifunctional nanocarriers, including targeting molecules, macromolecular monoclonal antibodies, peptides, inorganic nanomaterials, and organic and polymeric nanomaterials. Therapeutic radioisotopes have been labeled onto these nanocarriers via different methods (chelating, chemical doping, encapsulating, displacement) to inhibit or kill cancer cells. With the continuous development of research in this respect, more promising biomaterials as well as novel therapeutic strategies have emerged to achieve the high-performance RIT of cancer. In this review article, we summarize recent advances in biomaterial-mediated RIT of cancer and provide guidance for non-experts to understand nuclear medicine and to conduct cancer radiotherapy.

Pharmacological Ascorbate Promotes the Tumor Radiosensitization of Au@Pd Nanoparticles with Simultaneous Protection of Normal Tissues

Nanoradiosensitizers containing high-Z elements hold great potential in radiotherapy owing to the increasing energy deposition effect on X-ray irradiation. However, their potential clinical application is limited by the irradiation damage in nontarget tissues surrounding the tumor site, as well as the safety concerns for nanomaterials. Our findings demonstrate that pharmacological ascorbate displays a synergistic radiosensitizing effect in combination with nanoradiosensitizers. By engineering the Au@Pd core-shell nanostructures and precisely regulating their shell thickness, the obtained Au@Pd nanomaterials exhibit excellent ascorbate oxidase-like activity. Along with the accelerating generation of H₂O₂, pharmacological ascorbate significantly enhances the radiosensitizing effect of Au@Pd-PEG nanoparticles on both cancer cells and solid tumor. Interestingly, pharmacological ascorbate effectively protects normal tissues from X-ray-induced injury. The present work demonstrates that pharmacological ascorbate is an ideal agent for selectively improving the radiosensitizing effect of nanomaterials, providing a promising strategy to facilitate the clinical translation of nanoradiosensitizers.

Pd nanoparticles as a plasmonic material: synthesis, optical properties and applications

This review provides an overview of current progress in Pd nanoparticles supporting localized surface plasmon resonance and their applications. We begin by analyzing briefly the optical properties of Pd putting particular focus on outlining the origin of its size- and shape-dependent LSPR, high refractive index sensitivity, and high absorption contribution. The differences in the optical behavior with Au and Ag, the primary plasmonic materials, are highlighted. The main strategies to synthesize Pd nanoparticles, pure or hybrid, with well-defined optical properties are then reviewed. In this section, we include only those works that carry out the study of the optical properties of the nanoparticles. The applications of plasmonic Pd nanoparticles are also discussed in detail. This review is concluded with a section devoted to the future perspectives highlighting the most relevant challenges to be addressed to take Pd nanoparticles from the laboratory to real applications.

Controllable stripping of radiolabeled group in vivo to optimize nuclear imaging via NO-responsive bioorthogonal cleavage reaction

A novel "turn-off" strategy for controllable radionuclide clearance is established. 1,4-dihydropyridine (DHP) is used as a conditional linker to connect a radioisotope labeled moiety and nano-agent. A highly specific, sensitive and effective C-C bond cleavage of DHP happens in vivo when treated with nitric oxide which is provided by glyceryl trinitrate (GTN). The radioactive cut-off part from the nanoparticle is observed to be cleared quickly by microSPECT-CT. 3-5 times decreases of radioactivity in the blood, kidneys, intestine, heart and lungs are observed after GTN treatment in a biodistribution assay. The radioactivity redistribution indicates that the radioactive leaving part is indeed cut off and the radionuclide metabolism accelerated. Organ level internal dose assessment reveals the GTN treated groups carry only ½ the radiation dose of the control group. Collectively, a feasible pathway for controllable radionuclide clearance is for the first time provided for high contrast and low radiation nuclear imaging.

Radiolabeling strategies and pharmacokinetic studies for metal based nanotheranostics

Radiolabeled metal-based nanoparticles (MNPs) have drawn considerable attention in the fields of nuclear medicine and molecular imaging, drug delivery, and radiation therapy, given the fact that they can be potentially used as diagnostic imaging and/or therapeutic agents, or even as theranostic combinations. Here, we present a systematic review on recent advances in the design and synthesis of MNPs with major focuses on their radiolabeling strategies and the determinants of their in vivo pharmacokinetics, and together how their intended applications would be impacted. For clarification, we categorize all reported radiolabeling strategies for MNPs into indirect and direct approaches. While indirect labeling simply refers to the use of bifunctional chelators or prosthetic groups conjugated to MNPs for post-synthesis labeling with radionuclides, we found that many practical direct labeling methodologies have been developed to incorporate radionuclides into the MNP core without using extra reagents, including chemisorption, radiochemical doping, hadronic bombardment, encapsulation, and isotope or cation exchange. From the perspective of practical use, a few relevant examples are presented and discussed in terms of their pros and cons. We further reviewed the determinants of in vivo pharmacokinetic parameters of MNPs, including factors influencing their in vivo absorption, distribution, metabolism, and elimination, and discussed the challenges and opportunities in the development of radiolabeled MNPs for in vivo biomedical applications. Taken together, we believe the cumulative advancement summarized in this review would provide a general guidance in the field for design and synthesis of radiolabeled MNPs towards practical realization of their much desired theranostic capabilities. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > Diagnostic Nanodevices Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Palladium-based nanomaterials for cancer imaging and therapy

In recent decade, palladium-based (Pd-based) nanomaterials have shown significant potential for biomedical applications because of their unique optical properties, excellent biocompatibility and high stability in physiological environment. Compared with other intensively studied noble nanomaterials, such as gold (Au) and silver (Ag) nanomaterials, research on Pd-based nanomaterials started late, but the distinctive features, such as high photothermal conversion efficiency and high photothermal stability, have made them getting great attention in the field of nanomedicine. The goal of this review is to provide a comprehensive and critical perspective on the recent progress of Pd-based nanomaterials as imaging contrast agents and therapeutic agents. The imaging section focuses on applications in photoacoustic (PA) imaging, single-photon emission computed tomography (SPECT) imaging, computed tomography (CT) imaging and magnetic resonance (MR) imaging. For treatment of cancer, single photothermal therapy (PTT) and PTT combined with other therapeutic modalities will be discussed. Finally, the safety concerns, forthcoming challenges and perspective of Pd-based nanomaterials on biomedical applications will be presented.

Technetium-99 m-PEGylated dendrimer-G2-(Dabcyle-Lys6,Phe7)-pHBSP: A novel Nano-Radiotracer for molecular and early detecting of cardiac ischemic region

In cardiac ischemic disorder, pyroglutamate helix B surface peptide (pHBSP) which derived from erythropoietin causes to increase cell stability. To improve the serum stability of pHBSP, two lipophilic amino acids Arg⁶, Ala⁷ were replaced with Fmoc-(Dabcyle)-Lys-OH and Fmoc-Phe-OH during the peptide synthesis. This peptide was subsequently conjugated to PEGylated dendrimer-G₂ and labeled with ^99mTcO₄^- to detect cardiac ischemic region. Radiochemical purity (RCP) of ^99mTc-PEGylated dendrimer-G₂-(Dabcyle-Lys⁶,Phe⁷)-pHBSP was evaluated by ITLC method. In addition, the radiopeptide was investigated for stability in human serum and binding affinity to hypoxic cells in myocardium H9c2 cell lines. Biodistribution and SPECT/CT scintigraphy were assessed in cardiac ischemic rats. Radiochemical yield indicated that the anionic dendrimer has a very high potential to complex formation with ^99mTcO^-₄ (RCP > 94%) which was stable in human serum with RCP 89% up to 6 h. The binding of ^99mTc- nanoconjugate to hypoxic cells was significantly more than normoxic cells (3-fold higher compared to normoxic cells at 1 h). In biodistribution studies, erythropoietin receptor-Beta common receptor (EPO-BcR)-positive uptake in the cardiac ischemic region was 3.62 ± 0.44% ID/g 30 min post injection. SPECT imaging showed a prominent uptake of ^99mTc-nanoconjugate in EPO-BcR expressing ischemic heart.

Ultrathin Pd-based nanosheets: syntheses, properties and applications

Two-dimensional (2D) noble metal-based nanosheets (NSs) have received considerable interest in recent years due to their unique properties and widespread applications. Pd-based NSs, as a typical member of 2D noble metal-based NSs, have been most extensively studied. In this review, we first summarize the research progress on the synthesis of Pd-based NSs, including pure Pd NSs, Pd-based alloy NSs, Pd-based core-shell NSs and Pd-based hybrid NSs. The synthetic strategy and growth mechanism are systematically discussed. Then their properties and applications in catalysis, biotherapy, gas sensing and so on are introduced in detail. Finally, the challenges and opportunities towards the rational design and controlled synthesis of Pd-based NSs are proposed.

A dual factor activated metal-organic framework hybrid nanoplatform for photoacoustic imaging and synergetic photo-chemotherapy

Metal organic frameworks (MOFs) have attracted great interest as a smart drug delivery platform in the battle against cancer for their intriguing properties, such as high drug loading efficiency and microenvironment responsive degradation. Hence, the development of multifunctional MOFs integrating several theranostic elements is of crucial importance. In this work, we constructed a theranostic nanoplatform (DOX/Pd@ZIF-8) based on metal-organic frameworks encapsulating 2D Pd nanosheets and DOX using an all-in-one strategy, taking the advantages of the smart drug delivery function of MOFs and the excellent optical properties of Pd nanosheets. Polydopamine (PDA) was then introduced (DOX/Pd@ZIF-8@PDA) to improve the biocompatibility. DOX/Pd@ZIF-8@PDA exhibited excellent photothermal conversion effects and optoacoustic effects due to the strong NIR light absorption of Pd nanosheets. DOX was released in a pH-dependent manner and the release rates were accelerated in acidic solutions. However burst drug release in a relatively short period could be achieved upon 808 nm laser irradiation. Moreover, the potential of DOX/Pd@ZIF-8@PDA implemented as photoacoustic imaging contrast agents in vitro and in vivo was fully exploited and dual factor activated synergetic photo-chemo cancer therapy was successfully carried out.

Radiolabeling nanomaterials for multimodality imaging: New insights into nuclear medicine and cancer diagnosis

Nuclear medicine imaging has been developed as a powerful diagnostic approach for cancers by detecting gamma rays directly or indirectly from radionuclides to construct images with beneficial characteristics of high sensitivity, infinite penetration depth and quantitative capability. Current nuclear medicine imaging modalities mainly include single-photon emission computed tomography (SPECT) and positron emission tomography (PET) that require administration of radioactive tracers. In recent years, a vast number of radioactive tracers have been designed and constructed to improve nuclear medicine imaging performance toward early and accurate diagnosis of cancers. This review will discuss recent progress of nuclear medicine imaging tracers and associated biomedical imaging applications. Radiolabeling nanomaterials for rational development of tracers will be comprehensively reviewed with highlights on radiolabeling approaches (surface coupling, inner incorporation and interface engineering), providing profound understanding on radiolabeling chemistry and the associated imaging functionalities. The applications of radiolabeled nanomaterials in nuclear medicine imaging-related multimodality imaging will also be summarized with typical paradigms described. Finally, key challenges and new directions for future research will be discussed to guide further advancement and practical use of radiolabeled nanomaterials for imaging of cancers.

An Activatable Near-Infrared Chromophore for Multispectral Optoacoustic Imaging of Tumor Hypoxia and for Tumor Inhibition

Hypoxia is a key hallmark of solid tumors and tumor hypoxia usually contributes to cancer progression, therapeutic resistance and poor outcome. Accurately detecting and imaging tumor hypoxia with high spatial resolution would be conducive to formulating optimized treatment plan and thus achieving better patient outcome. Methods: Tumor hypoxia can cleave the azo linker and release a NIR fluorophore (NR-NH2) and release the active drug as well. NR-NH2 shows a strong absorption band at around 680 nm and a strong fluorescence band at 710 nm, allowing for both multispectral optoacoustic tomography imaging (MSOT) and fluorescent imaging of tumor hypoxia in a tumor-bearing mouse model. Results: Liposome encapsulated with the activatable chromophore (NR-azo) for detecting/imaging tumor hypoxia and for tumor inhibition was demonstrated. For this chromophore, a xanthene-based NIR fluorophore acts as the optoacoustic and fluorescent reporter, an azo linker serves as the hypoxia-responsive moiety and a nitrogen mustard as the therapeutic drug. NR-azo shows an absorption at around 575 nm but exhibits negligible fluorescence due to the existence of the strong electron-withdrawing azo linker. Conclusion: We demonstrated an optoacoustic and fluorescent system for not only imaging tumor hypoxia in vivo but also achieving tumor inhibition.

Strategies based on metal-based nanoparticles for hypoxic-tumor radiotherapy

Radiotherapy (RT) is one of the most effective and frequent clinical cancer treatments. Nevertheless, RT can cause damage to normal tissues around tumors under high-dose ionizing radiation. Inspired by versatile metal-based nanomaterials, great efforts have been devoted to developing nanomaterials with high-Z metal elements as radiosensitizers by depositing more energy into tumors for RT enhancement. However, these metal-based nanomaterial-mediated RTs are highly O2-dependent. Unfortunately, O2 concentrations within the majority of solid tumors exhibit low levels, which seriously hampers the antitumor efficacy of these nanomaterials during RT. Therefore, the development of novel metal-based nanomaterials as radiosensitizers capable of avoiding the radioresistance induced by tumor hypoxia is highly desirable and important. Currently, the most effective approaches to reverse the radioresistance of hypoxic tumors are to introduce nanomaterials with O2-elevating ability by delivering exogenous O2, generating O2 in situ, increasing intratumoral blood flow, or reducing HIF-1 expression to harness the O2 level in solid tumors. Besides these, recently, some innovative and simple strategies by employing nanoradiosensitizers with diminished oxygen dependence have also been applied to combat unmet hypoxic challenges, in which nanoradiosensitizers can target tumor hypoxia for selective RT, enhance oxygen-independent ROS generation, or combine with non-oxygen dependent cancer therapies for synergistic treatments. These approaches and strategies provide new avenues for enhanced hypoxic-tumor RT. Nevertheless, an overall review aiming specifically at these strategies is still rare. Herein, we present an overview about recent advances in metal-based nanomaterials for hypoxic-tumor RT, and give a detailed discussion about the design and working mechanisms of these strategies in their application of RT. Finally, current challenges and future perspectives are also pointed out in this field.

DNA-templated porous nanoplatform towards programmed "double-hit" cancer therapy via hyperthermia and immunogenicity activation

Photothermal therapy, assisted with long-term immunological anti-tumor effect, has great potential in clinical medical practice. Herein, a brand new DNA-template hydrothermal method was developed to prepare novel Co₉S₈ nanoplatform with outstanding hydrophily and mesoporous internal structure. Based on the mesoporous Co₉S₈ nanoplatform, MRI-guided enhanced photothermal-immunology "double-hit" synergistic cancer therapy was achieved, through the HSP90 inhibition and immunology activation effect of the loaded epigallocatechin gallate and oxaliplatin. It is noteworthy that the drugs were stepwise released from the nanoplatform under the trigger of pH and heat, respectively. More importantly, the high efficient synergistic cancer therapy and long-term immunological anti-tumor effect were confirmed in vivo. The developed porous nanoplatform, taking accounts of both high efficient tumor ablation and long-term anti-tumor effect, provide a new strategy to the development of next generation nanomedicine for clinical cancer treatment.

Novel phthalocyanine-based polymeric micelles with high near-infrared photothermal conversion efficiency under 808 nm laser irradiation for in vivo cancer therapy

Photothermal therapy (PTT) has emerged as one of the promising methodologies for the treatment of cancer, and ideal photothermal agents need to be biodegradable and have strong optical absorbance in the near-infrared (NIR) optical window. Here, we report a new phthalocyanine molecule, 4OCSPC, which expands the absorbance edge to 850 nm. Under 808 nm NIR laser irradiation, 4OCSPC polymeric micelles showed robust photostability and a high photothermal conversion of 47.0%. Also, the 4OCSPC polymeric micelles exhibit a high in vivo PTT efficacy against 4T1 tumors in mice.

The biobehavior, biocompatibility and theranostic application of SPNS and Pd@Au nanoplates in rats and rabbits

On account of the fascinating surface plasmon resonance (SPR) properties, the ability of passively targeting tumors and remarkable biocompatibility, two-dimensional (2D) Pd-based nanomaterials have demonstrated wide application prospects in cancer theranostics. However, the used animal models for exploring the bioapplications and biosafety of 2D Pd-based nanomaterials were usually limited to mice. To further widen their biomedical applications and promote future clinical transformation, it is necessary to make a breakthrough in animal models. In this work, Sprague Dawley (SD) rats and New Zealand rabbits were used as the experimental animals and orthotopic liver tumors or subcutaneous tumors were induced in these animals. Taking ≈5 nm small Pd nanosheets (SPNS) and 30 nm Pd@Au nanoplates (Pd@Au) as the representative 2D Pd-based nanomaterials, we investigated their biobehaviors and biosafety in rat liver & subcutaneous tumor models and rabbit liver tumors. The results indicated that SPNS and Pd@Au could still effectively accumulate on the tumor sites of these bigger animal models by the enhanced permeability and retention (EPR) effect, and the accumulation effects were closely related to their sizes. Metabolism studies confirmed that SPNS could be excreted out of rats through urine. Moreover, based on the sufficient uptake by cancer cells and passive accumulation of SPNS and Pd@Au in subcutaneous tumors in rats, we performed photothermal therapy (PTT) in vitro and in vivo. Significant tumor growth inhibition illustrated that even though the animal model was dozens of times bigger than the mouse model, the 2D Pd-based nanomaterials satisfied the requirements of being an outstanding photothermal reagent. Finally, the hematological and histological examination results suggested that SPNS and Pd@Au had favorable biocompatibility in rats and rabbits at a given dose. We hope this work will drive the development of 2D Pd-based nanomaterials towards practical clinical applications and provide a guide for other theranostic nanoplatforms that will be applied in bigger animal tumor models in the future.

Photoacoustic Imaging: Contrast Agents and Their Biomedical Applications

Photoacoustic (PA) imaging as a fast-developing imaging technique has great potential in biomedical and clinical applications. It is a noninvasive imaging modality that depends on the light-absorption coefficient of the imaged tissue and the injected PA-imaging contrast agents. Furthermore, PA imaging provides superb contrast, super spatial resolution, and high penetrability and sensitivity to tissue functional characteristics by detecting the acoustic wave to construct PA images. In recent years, a series of PA-imaging contrast agents are developed to improve the PA-imaging performance in biomedical applications. Here, recent progress of PA contrast agents and their biomedical applications are outlined. PA contrast agents are classified according to their components and function, and gold nanocrystals, gold-nanocrystal assembly, transition-metal chalcogenides/MXene-based nanomaterials, carbon-based nanomaterials, other inorganic imaging agents, small organic molecules, semiconducting polymer nanoparticles, and nonlinear PA-imaging contrast agents are discussed. The applications of PA contrast agents as biosensors (in the sensing of metal ions, pH, enzymes, temperature, hypoxia, reactive oxygen species, and reactive nitrogen species) and in bioimaging (lymph nodes, vasculature, tumors, and brain tissue) are discussed in detail. Finally, an outlook on the future research and investigation of PA-imaging contrast agents and their significance in biomedical research is presented.

Alkaline Phosphatase-Triggered Self-Assembly of Near-Infrared Nanoparticles for the Enhanced Photoacoustic Imaging of Tumors

Photoacoustic (PA) imaging is advantageous for the diagnosis of superficial cancer with high spatial resolution. However, to the best of our knowledge, using an alkaline phosphatase (ALP)-activatable probe for the enhanced PA imaging of tumors has not been reported. In this work, we rationally designed a NIR probe IR775-Phe-Phe-Tyr(H₂PO₃)-OH (1P) for PA imaging ALP activity in vitro and in tumor. Under the catalysis of ALP, 1P was efficiently converted to IR775-Phe-Phe-Tyr-OH (1), which self-assembled into the nanoparticles 1-NPs. The formation of 1-NPs induced a 6.4-fold enhancement of the 795 nm PA signal of 1P. In vivo tumor PA imaging results indicated that, compared to that in the ALP inhibitor-treated control group, PA contrast in the experimental group enhanced 2.3 folds at 4 h after 1P injection. By replacing the Phe-Phe-Tyr(H₂PO₃)-OH motif in 1P with other enzyme-cleavable ones, we hope that more PA probes could be developed for the precise diagnoses of their corresponding cancers in the near future.

Wetting transition in nanochannels for biomimetic free-blocking on-demand drug transport

Water wetting behavior in nanometer dimensions is of great importance to the signal transmission and substance transport of organisms, e.g., aquaporins on cell membranes. A biological channel can control the transport of water and ions by regulating channel wettability, which results from the transition between the intrinsic hydrophobic state and the stimulus-induced hydration state. Inspired by aquaporins in nature, herein, a biomimetic free-blocking on-demand delivery system is proposed, which is constructed by controlling the wettability of the inner surface of nanochannels of mesoporous silica nanoparticles (MSNs). Such a system is completely different from the traditional physically occluding pore controlled release system. It circumvents the use of other extra capping agents, thus overcoming the limitations of the traditional nano "gate" blockage system with inherent instability, poor plugging capability and low biocompatibility. Additionally, further applications in drug delivery have shown that this system can selectively release entrapped drugs in beta cells triggered by intracellular glucose in a controlled manner but not in normal cells. This hydrophobic gating drug delivery system with simple and effective performance provides a new opportunity for constructing a mass transport platform from the perspective of surface wettability.

pH-sensitive radiolabeled and superfluorinated ultra-small palladium nanosheet as a high-performance multimodal platform for tumor theranostics

Radiolabeled nanomaterials, especially those with ultra-small structures, have been the research focus in recent years, and thus may open up new prospects for clinical diseases theranostics. Herein, fluorinated Pd nanosheets labeled with Gd or radionuclides are developed as multimodal platforms for tumor theranostics. These nanomaterials decorated by functional polyethylene glycol demonstrate ultrahigh ¹⁹F MRI signal, ultrasmall size and good dispersibility. These ultrasmall materials exhibit good biocompatibility and easily to be modified for multimodal imaging (SPECT/MRI/PAI) by assembling the functional groups like building blocks. Furthermore, with high accumulation in tumor sites, under the guidance of multimodal imaging, combined photothermal therapy and radiotherapy are performed and synergistic effects are obtained. By comparing the in vivo behaviors of nanostructures labeled by different nuclides, the present study suggests the pH-sensitive radioiodinated Pd nanosheet which has unexpected T/NT ratio (>4-fold tumor-to-muscle ratio) in SPECT imaging and solves the critical high background issue of nanoprobes, could improve diagnostic accuracy and guide combination therapy. In summary, this functionalized nanoplatform with promising imaging and therapeutic efficacy has great potential for precision theranostic nanomedicines.