Shape-Dependent Radiosensitization Effect of Gold Nanostructures in Cancer Radiotherapy: Comparison of Gold Nanoparticles, Nanospikes, and Nanorods

Enhancing X-Ray Sensitization with Multifunctional Nanoparticles

In the progression of X-ray-based radiotherapy for the treatment of cancer, the incorporation of nanoparticles (NPs) has a transformative impact. This study investigates the potential of NPs, particularly those comprised of high atomic number elements, as radiosensitizers. This aims to optimize localized radiation doses within tumors, thereby maximizing therapeutic efficacy while preserving surrounding tissues. The multifaceted applications of NPs in radiotherapy encompass collaborative interactions with chemotherapeutic, immunotherapeutic, and targeted pharmaceuticals, along with contributions to photodynamic/photothermal therapy, imaging enhancement, and the integration of artificial intelligence technology. Despite promising preclinical outcomes, the paper acknowledges challenges in the clinical translation of these findings. The conclusion maintains an optimistic stance, emphasizing ongoing trials and technological advancements that bolster personalized treatment approaches. The paper advocates for continuous research and clinical validation, envisioning the integration of NPs as a revolutionary paradigm in cancer therapy, ultimately enhancing patient outcomes.

Spike structure of gold nanobranches induces hepatotoxicity in mouse hepatocyte organoid models

BACKGROUND

Gold nanoparticles (GNPs) have been extensively recognized as an active candidate for a large variety of biomedical applications. However, the clinical conversion of specific types of GNPs has been hindered due to their potential liver toxicity. The origin of their hepatotoxicity and the underlying key factors are still ambiguous. Because the size, shape, and surfactant of GNPs all affect their properties and cytotoxicity. An effective and sensitive platform that can provide deep insights into the cause of GNPs' hepatotoxicity in vitro is therefore highly desired.

METHODS

Here, hepatocyte organoid models (Hep-orgs) were constructed to evaluate the shape-dependent hepatotoxicity of GNPs. Two types of GNPs with different nanomorphology, gold nanospheres (GNSs) and spiny gold nanobranches (GNBs), were synthesized as the representative samples. Their shape-dependent effects on mice Hep-orgs' morphology, cellular cytoskeletal structure, mitochondrial structure, oxidative stress, and metabolism were carefully investigated.

RESULTS

The results showed that GNBs with higher spikiness and tip curvature exhibited more significant cytotoxicity compared to the rounded GNSs. The spike structure of GNBs leads to a mitochondrial damage, oxidative stress, and metabolic disorder in Hep-orgs. Meanwhile, similar trends can be observed in HepG2 cells and mice models, demonstrating the reliability of the Hep-orgs.

CONCLUSIONS

Hep-orgs can serve as an effective platform for exploring the interactions between GNPs and liver cells in a 3D perspective, filling the gap between 2D cell models and animal models. This work further revealed that organoids can be used as an indispensable tool to rapidly screen and explore the toxic mechanism of nanomaterials before considering their biomedical functionalities.

A simulation study on the radiosensitization properties of gold nanorods

Objective. Gold nanorods (GNRs) have emerged as versatile nanoparticles with unique properties, holding promise in various modalities of cancer treatment through drug delivery and photothermal therapy. In the rapidly evolving field of nanoparticle radiosensitization (NPRS) for cancer therapy, this study assessed the potential of gold nanorods as radiosensitizing agents by quantifying the key features of NPRS, such as secondary electron emission and dose enhancement, using Monte Carlo simulations.Approach. Employing the TOPAS track structure code, we conducted a comprehensive evaluation of the radiosensitization behavior of spherical gold nanoparticles and gold nanorods. We systematically explored the impact of nanorod geometry (in particular size and aspect ratio) and orientation on secondary electron emission and deposited energy ratio, providing validated results against previously published simulations.Main results. Our findings demonstrate that gold nanorods exhibit comparable secondary electron emission to their spherical counterparts. Notably, nanorods with smaller surface-area-to-volume ratios (SA:V) and alignment with the incident photon beam proved to be more efficient radiosensitizing agents, showing superiority in emitted electron fluence. However, in the microscale, the deposited energy ratio (DER) was not markedly influenced by the SA:V of the nanorod. Additionally, our findings revealed that the geometry of gold nanoparticles has a more significant impact on the emission of M-shell Auger electrons (with energies below 3.5 keV) than on higher-energy electrons.Significance. This research investigated the radiosensitization properties of gold nanorods, positioning them as promising alternatives to the more conventionally studied spherical gold nanoparticles in the context of cancer research. With increasing interest in multimodal cancer therapy, our findings have the potential to contribute valuable insights into the perspective of gold nanorods as effective multipurpose agents for synergistic photothermal therapy and radiotherapy. Future directions may involve exploring alternative metallic nanorods as well as further optimizing the geometry and coating materials, opening new possibilities for more effective cancer treatments.

Recent nanotheranostic approaches in cancer research

Humanity is suffering from cancer which has become a root cause of untimely deaths of individuals around the globe in the recent past. Nanotheranostics integrates therapeutics and diagnostics to monitor treatment response and enhance drug efficacy and safety. We hereby propose to discuss all recent cancer imaging and diagnostic tools, the mechanism of targeting tumor cells, and current nanotheranostic platforms available for cancer. This review discusses various nanotheranostic agents and novel molecular imaging tools like MRI, CT, PET, SPEC, and PAT used for cancer diagnostics. Emphasis is given to gold nanoparticles, silica, liposomes, dendrimers, and metal-based agents. We also highlight the mechanism of targeting the tumor cells, and the limitations of different nanotheranostic agents in the field of research for cancer treatment. Due to the complexity in this area, multifunctional and hybrid nanoparticles functionalized with targeted moieties or anti-cancer drugs show the best feature for theranostics that enables them to work on carrying and delivering active materials to the desired area of the requirement for early detection and diagnosis. Non-invasive imaging techniques have a specificity of receptor binding and internalization processes of the nanosystems within the cancer cells. Nanotheranostics may provide the appropriate medicine at the appropriate dose to the appropriate patient at the appropriate time.

The Refined Application and Evolution of Nanotechnology in Enhancing Radiosensitivity During Radiotherapy: Transitioning from Gold Nanoparticles to Multifunctional Nanomaterials

Radiotherapy is a pivotal method for treating malignant tumors, and enhancing the therapeutic gain ratio of radiotherapy through physical techniques is the direction of modern precision radiotherapy. Due to the inherent physical properties of high-energy radiation, enhancing the therapeutic gain ratio of radiotherapy through radiophysical techniques inevitably encounters challenges. The combination of hyperthermia and radiotherapy can enhance the radiosensitivity of tumor cells, reduce their radioresistance, and holds significant clinical utility in radiotherapy. Multifunctional nanomaterials with excellent biocompatibility and safety have garnered widespread attention in tumor hyperthermia research, demonstrating promising potential. Utilizing nanotechnology as a sensitizing carrier in conjunction with radiotherapy, and high atomic number nanomaterials can also serve independently as radiosensitizing carriers. This synergy between tumor hyperthermia and radiotherapy may overcome many challenges currently limiting tumor radiotherapy, offering new opportunities for its further advancement. In recent years, the continuous progress in the synthesis and design of novel nanomaterials will propel the future development of medical imaging and cancer treatment. This article summarizes the radiosensitizing mechanisms and effects based on gold nanotechnology and provides an overview of the advancements of other nanoparticles (such as bismuth-based nanomaterials, magnetic nanomaterials, selenium nanomaterials, etc.) in the process of radiation therapy.

Mitochondria-Targeted Nanosystem Enhances Radio-Radiodynamic-Chemodynamic Therapy on Triple Negative Breast Cancer

Radiodynamic therapy (RDT), which produces ¹O₂ and other reactive oxygen species (ROS) in response to X-rays, can be used in conjunction with radiation therapy (RT) to drastically lower X-ray dosage and reduce radio resistance associated with conventional radiation treatment. However, radiation-radiodynamic therapy (RT-RDT) is still impotent in a hypoxic environment in solid tumors due to its oxygen-dependent nature. Chemodynamic therapy (CDT) can generate reactive oxygen species and O₂ by decomposing H₂O₂ in hypoxic cells and thus potentiate RT-RDT to achieve synergy. Herein, we developed a multifunctional nanosystem, AuCu-Ce6-TPP (ACCT), for RT-RDT-CDT. Ce6 photosensitizers were conjugated to AuCu nanoparticles via Au-S bonds to realize radiodynamic sensitization. Cu can be oxidized by H₂O₂ and catalyze the degradation of H₂O₂ to generate ^•OH through the Fenton-like reaction to realize CDT. Meanwhile, the degradation byproduct oxygen can alleviate hypoxia while Au can consume glutathione to increase the oxidative stress. We then attached mercaptoethyl-triphenylphosphonium (TPP-SH) to the nanosystem, targeting ACCT to mitochondria (colocalization Pearson coefficient 0.98) to directly disrupt mitochondrial membranes and more efficiently induce apoptosis. We confirmed that ACCT efficiently generates ¹O₂ and ^•OH upon X-ray irradiation, resulting in strong anticancer efficacy in both normoxic and hypoxic 4T1 cells. The down-regulation of hypoxia-inducible factor 1α expression and reduction of intracellular H₂O₂ concentrations suggested that ACCT could significantly alleviate hypoxia in 4T1 cells. ACCT-enhanced RT-RDT-CDT can successfully shrink or remove tumors in radioresistant 4T1 tumor-bearing mice upon 4 Gy of X-ray irradiation. Our work thus presents a new strategy to treat radioresistant hypoxic tumors.

Water-Soluble Au25 Clusters with Single-Crystal Structure for Mitochondria-Targeting Radioimmunotherapy

Atomically precise gold clusters play an important role in the development of high-Z-element-based radiosensitizers, due to their intriguing structural diversity and advantages in correlating structures and properties. However, the synthesis of gold clusters with both water-solubility and single-crystal structure remains a challenge. In this study, atomically precise Au₂₅(S-TPP)₁₈ clusters (TPP-SNa = sodium 3-(triphenylphosphonio)propane-1-thiolate bromide) showing both mitochondria-targeting ability and water-solubility were obtained via ligand design for enhanced radioimmunotherapy. Compared with Au₂₅(SG)₁₈ clusters (SG = glutathione), Au₂₅(S-TPP)₁₈ exhibited higher radiosensitization efficiency due to its mitochondria-targeting ability, higher ROS production capacity, and obvious inhibition upon thioredoxin reductase (TrxR). In addition, the enhanced radiotherapy-triggered abscopal effect in combination with checkpoint blockade displayed effective growth inhibition of distant tumors. This work reveals the ligand-regulated organelle targeting ability of metal clusters by which feasible strategies to promote their application in precise theranostics could be realized.

Gold-containing liposomes and glucose-coated gold nanoparticles enhances the radiosensitivity of B16F0 melanoma cells via increasing apoptosis and ROS production

AIM

To increase the effectiveness of radiation therapy, metals with high Z number are used as radiosensitizers. In this regard, the effectiveness of various gold nanoparticles as radiosensitizer has been proven. Therefore, this study aimed to evaluate the effects of liposomes containing gold ions (Gold-Lips) and glucose-coated gold nanoparticles (Glu-GNPs) on radiation sensitivity of B16F0 melanoma cells.

MAIN METHODS

Naked GNPs, Glu-GNPs and Gold-Lips were synthesized and their physicochemical properties were evaluated using DLS. The cytotoxicity and sensitivity of the nanoparticles to radiation were evaluated using MTT and colony formation assay, respectively. Flow cytometry was performed to evaluate the apoptotic effect of nanoparticles on B16F0 cells. The intracellular ROS levels and mRNA expression of Bax, Bcl-2, p53, Caspase-3, and Caspase-7 genes were also evaluated. Finally, caspase 3/7 activity was determined using a luminescence assay kit.

KEY FINDINGS

The results revealed that GNPs, Glu-GNPs, and Gold-Lips had a desired size and zeta potential. Results from the colony assay showed that the all non-toxic concentrations of Gold-Lips significantly increased cell death in B16F0 cells compared with the Glu-GNPs (p > 0.05). Flow cytometry and Caspase-3/-7 activity confirmed the results of the colony assay and showed that increasing the sensitivity of cells to radiation increases apoptosis. Moreover, we found that Gold-Lips increased the mRNA expression of p53, Bax, and Caspase-3/-7, and decreased the Bcl-2 mRNA expression.

SIGNIFICANCE

Overall, both Gold-Lips and Glu-GNPs enhanced the radiosensitivity of B16F0 cells, however, Gold-Lips had better effects, which could make them a promising tools in cancer radiotherapy.

Nanodrugs with intrinsic radioprotective exertion: Turning the double-edged sword into a single-edged knife

Ionizing radiation (IR) poses a growing threat to human health, and thus ideal radioprotectors with high efficacy and low toxicity still receive widespread attention in radiation medicine. Despite significant progress made in conventional radioprotectants, high toxicity, and low bioavailability still discourage their application. Fortunately, the rapidly evolving nanomaterial technology furnishes reliable tools to address these bottlenecks, opening up the cutting-edge nano-radioprotective medicine, among which the intrinsic nano-radioprotectants characterized by high efficacy, low toxicity, and prolonged blood retention duration, represent the most extensively studied class in this area. Herein, we made the systematic review on this topic, and discussed more specific types of radioprotective nanomaterials and more general clusters of the extensive nano-radioprotectants. In this review, we mainly focused on the development, design innovations, applications, challenges, and prospects of the intrinsic antiradiation nanomedicines, and presented a comprehensive overview, in-depth analysis as well as an updated understanding of the latest advances in this topic. We hope that this review will promote the interdisciplinarity across radiation medicine and nanotechnology and stimulate further valuable studies in this promising field.

Metabolic Disruption of Gold Nanospheres, Nanostars and Nanorods in Human Metastatic Prostate Cancer Cells

Nanomaterials offer a broad spectrum of applications in biomedicine. The shapes of gold nanoparticles could modulate tumor cell behavior. Spherical (AuNP_sp), stars (AuNP_st) and rods (AuNP_r) shapes of polyethylene glycol coated-gold nanoparticles (AuNPs-PEG) were synthesized. Metabolic activity, cellular proliferation, and reactive oxygen species (ROS) were measured and the impact of AuNPs-PEG in metabolic enzymes function was evaluated by RT-qPCR in PC3, DU145, and LNCaP prostate cancer cells. All AuNPs were internalized, and the different morphologies of AuNPs showed to be an essential modulator of metabolic activity. For PC3 and DU145, the metabolic activity of AuNPs was found to rank in the following order from lowest to highest: AuNP_sp-PEG, AuNP_st-PEG, and AuNP_r-PEG. Regarding LNCaP cells, the AuNP_st-PEG were less toxic, followed by AuNP_sp-PEG and AuNP_r-PEG, but it seems not to be dose-dependent. The proliferation was lower in AuNP_r-PEG in PC3 and DU145 cells but was stimulated around 10% in most conditions (0.001-0.1 mM) in LNCaP cells (not statistically significant). For 1 mM, LNCaP cells showed a significant decrease in proliferation only for AuNP_r-PEG. The outcomes of the current study demonstrated that different AuNPs conformations influence cell behavior, and the correct size and shape must be chosen considering its final application in the field of nanomedicine.

Emerging plasmonic nanoparticles and their assemblies for cancer radiotherapy

Plasmonic nanoparticles and their assemblies have been widely used in biosensing, optical imaging, and biomedicine over the past few decades. Especially in the field of radiotherapy, the physicochemical properties of high-Z plasmonic nanomaterials endow them with the ability to sensitize radiotherapy. Compared with single particles, the assembled structure with tunable properties leads to versatile applications in drug delivery and cancer treatment. In this review, we focus on plasmonic nanoparticles and their assemblies for cancer radiotherapy. First, the sensitization mechanism of plasmonic radiosensitizers is briefly introduced. Subsequently, the recent progress in cancer radiotherapy is systematically discussed according to the structure and shape classification. Finally, the current challenges and future perspectives in this field are also discussed in detail.

Application of Gold Nanoparticles as Radiosensitizer for Metastatic Prostate Cancer Cell Lines

More than 50% of all prostate cancer (PCa) patients are treated by radiotherapy (RT). Radioresistance and cancer recurrence are two consequences of the therapy and are related to dose heterogeneity and non-selectivity between normal and tumoral cells. Gold nanoparticles (AuNPs) could be used as potential radiosensitizers to overcome these therapeutic limitations of RT. This study assessed the biological interaction of different morphologies of AuNPs with ionizing radiation (IR) in PCa cells. To achieve that aim, three different amine-pegylated AuNPs were synthesized with distinct sizes and shapes (spherical, AuNP_sp-PEG, star, AuNP_st-PEG, and rods, AuNP_r-PEG) and viability, injury and colony assays were used to analyze their biological effect on PCa cells (PC3, DU145, and LNCaP) when submitted to the accumulative fraction of RT. The combinatory effect of AuNPs with IR decreased cell viability and increased apoptosis compared to cells treated only with IR or untreated cells. Additionally, our results showed an increase in the sensitization enhancement ratio by cells treated with AuNPs and IR, and this effect is cell line dependent. Our findings support that the design of AuNPs modulated their cellular behavior and suggested that AuNPs could improve the RT efficacy in PCa cells.

Novel strategies for tumor radiosensitization mediated by multifunctional gold-based nanomaterials

Radiotherapy (RT) is one of the most effective and commonly used cancer treatments for malignant tumors. However, the existing radiosensitizers have a lot of side effects and poor efficacy, which limits the curative effect and further application of radiotherapy. In recent years, emerging nanomaterials have shown unique advantages in enhancing radiosensitization. In particular, gold-based nanomaterials, with high X-ray attenuation capacity, good biocompatibility, and promising chemical, electronic and optical properties, have become a new type of radiotherapy sensitizer. In addition, gold-based nanomaterials can be used as a carrier to load a variety of drugs and immunosuppressants; in particular, its photothermal therapy, photodynamic therapy and multi-mode imaging functions aid in providing excellent therapeutic effect in coordination with RT. Recently, many novel strategies of radiosensitization mediated by multifunctional gold-based nanomaterials have been reported, which provides a new idea for improving the efficacy and reducing the side effects of RT. In this review, we systematically summarize the recent progress of various new gold-based nanomaterials that mediate radiosensitization and describe the mechanism. We further discuss the challenges and prospects in the field. It is hoped that this review will help researchers understand the latest progress of gold-based nanomaterials for radiosensitization, and encourage people to optimize the existing methods or explore novel approaches for radiotherapy.

Copolymerized carbon nitride nanoparticles for near-infrared II photoacoustic-guided synergistic photothermal/radiotherapy

Nanotheranostic agents that integrate diagnosis and treatment are promising for precision medicine, but they encounter some obstacles such as penetration depth and efficiency. In this study, novel carbon nitride-rose bengal nanoparticles (CN-RB NPs) with a graphite carbon nitride skeleton were synthesized by one-step thermal copolymerization. The enhanced absorption in the near-infrared-II region (NIR-II) endows CN-RB NPs with an excellent photothermal effect under 1064 nm laser irradiation, as well as an obvious photoacoustic signal for imaging in vivo. Interestingly, due to the introduced iodine element, CN-RB NPs exhibit enhanced radiation therapy, indicating that CN-RB NPs can achieve ideal therapeutic outcome through collaborative photothermal/radiation therapy under the guidance of NIR-II photoacoustic imaging. Moreover, CN-RB NPs demonstrate minimal side effects and long-term biological stability after 14 days. Therefore, the proposed new multifunctional nano-platform CN-RB NPs hold great potential in the application of deep therapeutics.

Boosted Radiation Bystander Effect of PSMA-Targeted Gold Nanoparticles in Prostate Cancer Radiosensitization

Metal nanoparticles are effective radiosensitizers that locally enhance radiation doses in targeted cancer cells. Compared with other metal nanoparticles, gold nanoparticles (GNPs) exhibit high biocompatibility, low toxicity, and they increase secondary electron scatter. Herein, we investigated the effects of active-targeting GNPs on the radiation-induced bystander effect (RIBE) in prostate cancer cells. The impact of GNPs on the RIBE presents implications for secondary cancers or spatially fractionated radiotherapy treatments. Anti-prostate-specific membrane antigen (PSMA) antibodies were conjugated with PEGylated GNPs through EDC-NHS chemistry. The media transfer technique was performed to induce the RIBE on the non-irradiated bystander cells. This study focused on the LNCaP cell line, because it can model a wide range of stages relating to prostate cancer progression, including the transition from androgen dependence to castration resistance and bone metastasis. First, LNCaP cells were pretreated with phosphate buffered saline (PBS) or PSMA-targeted GNPs (PGNPs) for 24 h and irradiated with 160 kVp X-rays (0-8 Gy). Following that, the collected culture media were filtered (sterile 0.45 µm polyethersulfone) in order to acquire PBS- and PGNP- conditioned media (CM). Then, PBS- and PGNP-CM were transferred to the bystander cells that were loaded with/without PGNPs. MTT, γ-H2AX, clonogenic assays and reactive oxygen species assessments were performed to compare RIBE responses under different treatments. Compared with 2 Gy-PBS-CM, 8 Gy-PBS-CM demonstrated a much higher RIBE response, thus validating the dose dependence of RIBE in LNCaP cells. Compared with PBS-CM, PGNP-CM exhibited lower cell viability, higher DNA damage, and a smaller survival fraction. In the presence of PBS-CM, bystander cells loaded with PGNPs showed increased cell death compared with cells that did not have PGNPs. These results demonstrate the PGNP-boosted expression and sensitivity of RIBE in prostate cancer cells.

Photothermal therapy (PTT) is an effective treatment measure against solid tumors which fails to respond conventional chemo/radiation therapies in clinic

Photothermal therapy (PTT) has emerged as a fast, precisive, and cost-effective anticancer therapy protocol. Here we applied our previously designed nanomaterial (Tocophotoxil) for prospective PTT application to manage radiation- and chemo-resistant cancers in a preclinical model. A PTT dose vs. efficacy relationship was established for radioresistant breast (ZR-75-1 50Gy, 4T1 20Gy) and chemo-resistant ovarian (A2780LR) cancer cells and tumors in mice models. Compared to the sensitive cases, resistant cells treated with PTT for a shorter duration show higher endurance. However, preclinical tumor xenografts treated with optimal PTT dose show 2-3 fold higher longevity (P ≤ 0.05) of treated mice monitored by non-invasive imaging methods. Elevated ERK and AKT activation in radioresistant or only AKT activation in chemo-resistant cells were contributory to higher cell survival in sub-optimal PTT dose. A comprehensive single-cell Raman map of PTT treated ZR-75-1 cell reveals broad-spectrum macromolecular deformities, including protein damage features. Marked induction of pJNK, unfolded protein response (UPR) pathway, increased reactive oxygen species (ROS), and lipid peroxidation in PTT-treated cells disrupted the intracellular homeostasis. Analyzing cellular ultrastructure, the coexistence of swollen endoplasmic reticulum, and autophagic bodies after PTT indicate possible coordination between UPR and autophagy pathways. Therefore, this comprehensive study provides new evidence on the potential impact of PTT as a standalone therapy for ablation of failed conventional therapy-resistant cancers in vivo, the success of which is intricately linked to the PTT dose optimization. The study, for the first time, also illustrates that under PTT treatment, concerted action of novel molecular switches such as JNK activation and UPR activation plays a vital role in triggering autophagy and cancer cell death.

Improving the Effect of Cancer Cells Irradiation with X-rays and High-Energy Protons Using Bimetallic Palladium-Platinum Nanoparticles with Various Nanostructures

Nano-sized radiosensitizers can be used to increase the effectiveness of radiation-based anticancer therapies. In this study, bimetallic, ~30 nm palladium-platinum nanoparticles (PdPt NPs) with different nanostructures (random nano-alloy NPs and ordered core-shell NPs) were prepared. Scanning transmission electron microscopy (STEM), selected area electron diffraction (SAED), energy-dispersive X-ray spectroscopy (EDS), zeta potential measurements, and nanoparticle tracking analysis (NTA) were used to provide the physicochemical characteristics of PdPt NPs. Then, PdPt NPs were added to the cultures of colon cancer cells and normal colon epithelium cells in individually established non-toxic concentrations and irradiated with the non-harmful dose of X-rays/protons. Cell viability before and after PdPt NPs-(non) assisted X-ray/proton irradiation was evaluated by MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay. Flow cytometry was used to assess cell apoptosis. The results showed that PdPt NPs significantly enhanced the effect of irradiation on cancer cells. It was noticed that nano-alloy PdPt NPs possess better radiosensitizing properties compared to PtPd core-shell NPs, and the combined effect against cancer cells was c.a. 10% stronger for X-ray than for proton irradiation. Thus, the radio-enhancing features of differently structured PdPt NPs indicate their potential application for the improvement of the effectiveness of radiation-based anticancer therapies.

A Nanomedicine Structure-Activity Framework for Research, Development, and Regulation of Future Cancer Therapies

Despite their clinical success in drug delivery applications, the potential of theranostic nanomedicines is hampered by mechanistic uncertainty and a lack of science-informed regulatory guidance. Both the therapeutic efficacy and the toxicity of nanoformulations are tightly controlled by the complex interplay of the nanoparticle's physicochemical properties and the individual patient/tumor biology; however, it can be difficult to correlate such information with observed outcomes. Additionally, as nanomedicine research attempts to gradually move away from large-scale animal testing, the need for computer-assisted solutions for evaluation will increase. Such models will depend on a clear understanding of structure-activity relationships. This review provides a comprehensive overview of the field of cancer nanomedicine and provides a knowledge framework and foundational interaction maps that can facilitate future research, assessments, and regulation. By forming three complementary maps profiling nanobio interactions and pathways at different levels of biological complexity, a clear picture of a nanoparticle's journey through the body and the therapeutic and adverse consequences of each potential interaction are presented.

Gold-Nanoparticle-Enhanced Radio-Fluorogenic Hydrogel Sensor for Low Radiation Doses in Clinical Radiotherapy

Radio-fluorogenic hydrogel dosimeters are urgently needed in radiotherapy for 3D dose verification. However, few hydrogel sensors have been reported at low absorbed doses under 2 Gy which meets the requirements of clinical practice. Here, we report a new type of gold-nanoparticle-enhanced radio-fluorogenic agarose hydrogel with coumarin as the dose-responsive material. An optimal composition of 3 wt% of agarose, 0.1 mM of gold nanoparticles, and 0.5 mM coumarin was selected. The addition of gold nanoparticles enhanced the hydroxyl radicals generated from the radiolysis of water, which can react with coumarin and generate fluorescent 7-hydroxy-coumarin and, eventually, achieve low-dose verification of 0-2.4 Gy with a high linear correlation coefficient. These findings provide an effective method for 3D dose verification, and will inspire the development of other radio-fluorogenic sensing hydrogels as well.

An overview of the intracellular localization of high-Z nanoradiosensitizers

Radiation therapy (RT) is a method commonly used for cancer treatment worldwide. Commonly, RT utilizes two routes for combating cancers: 1) high-energy radiation to generate toxic reactive oxygen species (ROS) (through the dissociation of water molecules) for damaging the deoxyribonucleic acid (DNA) inside the nucleus 2) direct degradation of the DNA. However, cancer cells have mechanisms to survive under intense RT, which can considerably decrease its therapeutic efficacy. Excessive radiation energy damages healthy tissues, and hence, low doses are applied for cancer treatment. Additionally, different radiosensitizers were used to sensitize cancer cells towards RT through individual mechanisms. Following this route, nanoparticle-based radiosensitizers (herein called nanoradiosensitizers) have recently gained attention owing to their ability to produce massive electrons which leads to the production of a huge amount of ROS. The success of the nanoradiosensitizer effect is closely correlated to its interaction with cells and its localization within the cells. In other words, tumor treatment is affected from the chain of events which is started from cell-nanoparticle interaction followed by the nanoparticles direction and homing inside the cell. Therefore, passive or active targeting of the nanoradiosensitizers in the subcellular level and the cell-nano interaction would determine the efficacy of the radiation therapy. The importance of the nanoradiosensitizer's targeting is increased while the organelles beyond nucleus are recently recognized as the mediators of the cancer cell death or resistance under RT. In this review, the principals of cell-nanomaterial interactions and which dominate nanoradiosensitizer efficiency in cancer therapy, are thoroughly discussed.

Composition-Dependent Enzyme Mimicking Activity and Radiosensitizing Effect of Bimetallic Clusters to Modulate Tumor Hypoxia for Enhanced Cancer Therapy

Alloying is an efficient chemistry to tailor the properties of metal clusters. As a class of promising radiosensitizers, most previously reported metal clusters exhibit unitary function and cannot overcome radioresistance of hypoxic tumors. Here, atomically precise alloy clusters Pt₂ M₄ (M = Au, Ag, Cu) are synthesized with bright luminescence and adequate biocompatibility, and their composition-dependent enzyme mimicking activity and radiosensitizing effect is explored. Specifically, only the Pt₂ Au₄ cluster displays catalase-like activity, while the others do not have clusterzyme properties, and its radiosensitizing effect is the highest among all the alloy clusters tested. By taking advantage of the sustainable production of O₂ via the decomposition of endogenous H₂ O₂ , the Pt₂ Au₄ cluster modulates tumor hypoxia as well as increases the efficacy of radiotherapy. This work thus advances the cluster alloying strategy to produce multifunctional therapeutic agents for improving hypoxic tumor therapy.

Radiotherapy combined with immunotherapy: the dawn of cancer treatment

Radiotherapy (RT) is delivered for purposes of local control, but can also exert systemic effect on remote and non-irradiated tumor deposits, which is called abscopal effect. The view of RT as a simple local treatment has dramatically changed in recent years, and it is now widely accepted that RT can provoke a systemic immune response which gives a strong rationale for the combination of RT and immunotherapy (iRT). Nevertheless, several points remain to be addressed such as the interaction of RT and immune system, the identification of the best schedules for combination with immunotherapy (IO), the expansion of abscopal effect and the mechanism to amplify iRT. To answer these crucial questions, we roundly summarize underlying rationale showing the whole immune landscape in RT and clinical trials to attempt to identify the best schedules of iRT. In consideration of the rarity of abscopal effect, we propose that the occurrence of abscopal effect induced by radiation can be promoted to 100% in view of molecular and genetic level. Furthermore, the “radscopal effect” which refers to using low-dose radiation to reprogram the tumor microenvironment may amplify the occurrence of abscopal effect and overcome the resistance of iRT. Taken together, RT could be regarded as a trigger of systemic antitumor immune response, and with the help of IO can be used as a radical and systemic treatment and be added into current standard regimen of patients with metastatic cancer.

Histological Injury to Rat Brain, Liver, and Kidneys by Gold Nanoparticles is Dose-Dependent

Gold nanoparticles (GNPs) possess various interesting plasmonic properties that can provide a variety of diagnostic and therapeutic functionalities for biomedical applications. Compared to other inorganic metal nanoparticles (NPs), GNPs are less toxic and more biocompatible. However, the in vivo toxicity of gold nanoparticles on humans can be significant due to the size effect. This work aims to study the effect of multiple doses of small-size (≈20 nm) GNPs on the vital organs of Wistar rats. The study includes the oxidative stress in vital organs (liver, brain, and kidney) caused by GNPs and histopathology analysis. The rats were given a single caudal injection of NPs dispersed in PBS at 25, 50, 100, and 250 mg/kg of body weight. After sacrifice, both plasma and organs were collected for the determination of oxidant/antioxidant markers and histological studies. Our data show the high sensitivity of oxidative stress parameters to the GNPs in the brain, liver, and kidneys. However, the response to this stress is different between the organs and depends upon the antioxidant defense, where GSH levels control the MDA and PCO levels. Histological alterations are mild at 25, 50, and 100 mg/kg but significant at higher concentrations of 250 mg/kg. Therefore, histological impairments are shown to be dependent on the dose of GNPs. The results contribute to the understanding of oxidative stress and cellular interaction induced by nanoparticles.

Engineering Gold Nanostructures for Cancer Treatment: Spherical Nanoparticles, Nanorods, and Atomically Precise Nanoclusters

Cancer is a major global health issue and is a leading cause of mortality. It has been documented that various conventional treatments can be enhanced by incorporation with nanomaterials. Thanks to their rich optical properties, excellent biocompatibility, and tunable chemical reactivities, gold nanostructures have been gaining more and more research attention for cancer treatment in recent decades. In this review, we first summarize the recent progress in employing three typical gold nanostructures, namely spherical Au nanoparticles, Au nanorods, and atomically precise Au nanoclusters, for cancer diagnostics and therapeutics. Following that, the challenges and the future perspectives of this field are discussed. Finally, a brief conclusion is summarized at the end.

Size-changeable nanoprobes for the combined radiotherapy and photodynamic therapy of tumor

PURPOSE

Radiation therapy (RT) and photodynamic therapy (PDT) are promising while challenging in treating tumors. The potential radiation resistance of tumor cells and side effects to healthy tissues restrict their clinical treatment efficacy. Effective delivery of therapeutic agents to the deep tumor tissues would be available for tumor-accurate therapy and promising for the tumor therapy. Thus, developing nanoprobes with effectively delivering radiotherapy sensitizers and photosensitizers to the interior of tumors is needed for the accurate combined RT and PDT of tumor.

METHODS

The size-changeable nanoprobes of Gd₂O₃@BSA-BSA-Ce6 (BGBC) were synthesized with a crosslinking method. Magnetic resonance imaging (MRI) and in vivo near-infrared (NIR) imaging were measured to evaluate the nanoprobes' tumor accumulation and intratumor penetration effect. The tumor suppression effect of combined RT and PDT with these nanoprobes was also studied for the 4T1 bearing Balb/c mice.

RESULTS

The nanoprobes BGBC showed high tumor accumulation and disintegrated into small particles responding to the photo-irradiation-produced reactive oxygen species (ROS), allowing for tumor penetration. Abundant radiotherapy sensitizers and photosensitizers were delivered to the deep tumor tissues, which is available for the accurate therapy of tumor. In addition, the BGBC displayed outstanding MRI and fluorescence imaging effects for evaluating the biodistribution and tumor suppression effect of nanoprobes. Consequently, significant tumor suppression effect was obtained based on the accurate tumor treatment with the combined RT and PDT.

CONCLUSION

The designed size-changeable nanoprobes BGBC showed excellent tumor accumulation and deep tumor penetration, resulting in a significant tumor suppression effect based on the combined RT and PDT. This study provides a novel strategy for dual delivery of radiotherapy sensitizers and photosensitizers into the deep tumor tissues and is promising for the accurate theranostics of tumor.

Photothermal Therapy with HER2-Targeted Silver Nanoparticles Leading to Cancer Remission

Nanoparticles exhibiting the localized surface plasmon resonance (LSPR) phenomenon are promising tools for diagnostics and cancer treatment. Among widely used metal nanoparticles, silver nanoparticles (Ag NPs) possess the strongest light scattering and surface plasmon strength. However, the therapeutic potential of Ag NPs has until now been underestimated. Here we show targeted photothermal therapy of solid tumors with 35 nm HER2-targeted Ag NPs, which were produced by the green synthesis using an aqueous extract of Lavandula angustifolia Mill. Light irradiation tests demonstrated effective hyperthermic properties of these NPs, namely heating by 10 °C in 10 min. To mediate targeted cancer therapy, Ag NPs were conjugated to the scaffold polypeptide, affibody ZHER2:342, which recognizes a clinically relevant oncomarker HER2. The conjugation was mediated by the PEG linker to obtain Ag-PEG-HER2 nanoparticles. Flow cytometry tests showed that Ag-PEG-HER2 particles successfully bind to HER2-overexpressing cells with a specificity comparable to that of full-size anti-HER2 IgGs. A confocal microscopy study showed efficient internalization of Ag-PEG-HER2 into cells in less than 2 h of incubation. Cytotoxicity assays demonstrated effective cell death upon exposure to Ag-PEG-HER2 and irradiation, caused by the production of reactive oxygen species. Xenograft tumor therapy with Ag-PEG-HER2 particles in vivo resulted in full primary tumor regression and the prevention of metastatic spread. Thus, for the first time, we have shown that HER2-directed plasmonic Ag nanoparticles are effective sensitizers for targeted photothermal oncotherapy.

Biocompatible polymer-modified gold nanocomposites of different shapes as radiation sensitizers

Radiation therapy is a powerful approach for cancer treatment due to its low invasiveness. The development of radiation sensitizers is of great importance as they assist in providing radiation therapy at a low dose. In this study, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC)-modified gold nanocomposites of different shapes were created using the grafting-to approach to serve as a novel radiation sensitizer with high cellular uptake. The effect of the shape of the nanocomposite on cellular uptake by the breast cancer cell line MCF-7 was also investigated. The PMPC-modified gold nanostars showed the highest cellular uptake compared to the other gold nanocomposites (spheres and rods), whereas cell cytotoxicity was negligible among all candidates. Furthermore, the therapeutic effect of radiation of PMPC-modified nanostars was the highest among all the gold nanocomposites. These results clearly indicate that the shape of the gold nanocomposite is an important parameter for cellular uptake and radiation sensitizing effects in breast cancer cells.

Multifunctional high-Z nanoradiosensitizers for multimodal synergistic cancer therapy

Radiotherapy (RT) is one of the most common and effective clinical therapies for malignant tumors. However, there are several limitations that undermine the clinical efficacy of cancer RT, including the low X-ray attenuation coefficient of organs, serious damage to normal tissues, and radioresistance in hypoxic tumors. With the rapid development of nanotechnology and nanomedicine, high-Z nanoradiosensitizers provide novel opportunities to overcome radioresistance and improve the efficacy of RT by deposition of radiation energy through photoelectric effects. To date, several types of nanoradiosensitizers have entered clinical trials. Nevertheless, the limitation of the single treatment mode and the unclear mechanism of nanoparticle radiosensitization have hindered the further development of nanoradiosensitizers. In this review, we systematically describe the interaction mechanisms between X-rays and nanomaterials and summarize recent advances in multifunctional high-Z nanomaterials for radiotherapeutic-based multimodal synergistic cancer therapy. Finally, the challenges and prospects are discussed to stimulate the development of nanomedicine-based cancer RT.

Emerging Single-Atom Catalysts/Nanozymes for Catalytic Biomedical Applications

Single-atom catalysts (SACs) are a type of atomically dispersed nanozymes with the highest atom utilization, which employ low-coordinated single atoms as the catalytically active sites. SACs not only inherit the merits of traditional nanozymes, but also hold high catalytic activity and superb catalytic selectivity, which ensure their tremendous application potential in environmental remediation, energy storage and conversion, chemical industry, nanomedicine, etc. Nevertheless, undesired aggregation effect of single atoms during preactivation and reaction processes is significantly enhanced owing to the high surface free energy of single atoms. In this case, appropriate substrates are requisite to prevent the aggregation event through the powerful interactions between the single atoms and the substrates, thereby stabilizing the high catalytic activity of the catalysts. In this review, the synthetic methods and characterization approaches of SACs are first described. Then the application cases of SACs in nanomedicine are summarized. Finally, the current challenges and future opportunities of the SACs in nanomedicine are outlined. It is hoped that this review may have implications for furthering the development of new SACs with improved biophysicochemical properties and broadened biomedical applications.

GMT8 aptamer conjugated PEGylated Ag@Au core-shell nanoparticles as a novel radiosensitizer for targeted radiotherapy of glioma

Radiotherapy is one of the main treatment modalities for glioma, but the therapeutic efficacy is often limited by the radioresistance of tumor cells. The radiosensitization effects of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) on tumors have been confirmed by previous studies. To enhance the specific killing effect of irradiation on tumor cells, targeted modification of radiosensitizers is urgently needed. Herein, we developed polyethylene glycol (PEG)-coated Ag@Au core-shell nanoparticles (PSGNPs) modified with GMT8 aptamer (GSGNPs) and evaluated their radiosensitization effects on glioma cells through in vivo and in vitro experiments. Transmission electron microscope image showed that the prepared PSGNPs had a spherical core-shell structure with an average size of 11 nm. The ultraviolet-visible absorption spectra and Fourier transform infrared spectra displayed that GMT8 was successfully conjugated to PSGNPs. The results of dark-field imaging revealed that the targeting ability of GSGNPs to U87 glioma cells was much better than that to normal human microvascular endothelial cells. Additionally, it was also found that the endocytic pathways of GSGNPs mainly involved clathrin-mediated endocytosis and macropinocytosis. The sensitization enhancement ratio of GSGNPs was calculated to be 1.62, which was higher than that of PSGNPs. In vivo imaging results showed that GSGNPs exhibited good tumor targeting and retention capabilities, and the fluorescence intensity ratio of Cy5-GSGNPs to Cy5-PSGNPs reached a peak at 4 h after injection. More importantly, the median survival time of mice bearing U87 glioma was significantly prolonged after intravenous administration of GSGNPs combined with radiotherapy. This work demonstrated that GSGNPs could be used as an effective nano-radiosensitizer for targeted radiotherapy of glioma.

Engineered Nanostructured Photocatalysts for Cancer Therapy

The present review aims at highlighting recent advances in the development of photocatalysts devoted to cancer therapy applications. We pay especial attention to the engineering aspects of different nanomaterials including inorganic semiconductors, organic-based nanostructures, noble metal-based systems or synergistic hybrid heterostructures. Furthermore, we also explore and correlate structural and optical properties with their photocatalytic capability to successfully performing in cancer-related therapies. We have made an especial emphasis to introduce current alternatives to organic photosensitizers (PSs) in photodynamic therapy (PDT), where the effective generation of reactive oxidative species (ROS) is pivotal to boost the efficacy of the treatment. We also overview current efforts in other photocatalytic strategies to tackle cancer based on photothermal treatment, starvation therapy, oxidative stress unbalance via glutathione (GSH) depletion, biorthogonal catalysis or local relief of hypoxic conditions in tumor microenvironments (TME).

Development of nanotechnology-mediated precision radiotherapy for anti-metastasis and radioprotection

Radiotherapy (RT), including external beam RT and internal radiation therapy, uses high-energy ionizing radiation to kill tumor cells.

Active Nanomotors Surpass Passive Nanomedicines: Current Progress and Challenges

Artificial nanomotors show advantages over traditional nanomedicines in biomedical applications due to their active locomotion by converting various energy sources into mechanical force in situ. Currently, nanomotors have attracted wide...

Shape-Controllable Tellurium-Driven Heterostructures with Activated Robust Immunomodulatory Potential for Highly Efficient Radiophotothermal Therapy of Colon Cancer

Tellurium (Te)-based semiconductor easily leads to the recombination of photogenerated electron-hole pairs (h⁺-e^-) that severely limits the efficiency of reactive oxygen species (ROS) generation and further hinders its clinical application in biomedicine. With regard to these problems, herein we designed and synthesized a Te heterostructure (BTe-Pd-Au) by incorporating palladium (Pd) and gold (Au) elements to promote its radiosensitivity and photothermal performance, thus realizing highly efficient radiophotothermal tumor elimination by activating robust immunomodulatory potential. This shape-controllable heterostructure that coated by Pd on the surface of Te nanorods and Au in the center of Te nanorods was simply synthesized by using in situ synthesis method, which could promote the generation and separation of h⁺-e^- pairs, thereby exhibiting superior ROS producing ability and photothermal conversion efficiency. Using a mouse model of colon cancer, we proved that BTe-Pd-Au-R-combined radiophotothermal therapy not only eradicated tumor but also elicited to a series of antitumor immune responses by enhancing the cytotoxic T lymphocytes, triggering dendritic cells maturation, and decreasing the percentage of M2 tumor-associated macrophages. In summary, our study highlights a facile strategy to design Te-driven heterostructure with versatile performance in radiosensitization, photothermal therapy, and immunomodulation and offers great promise for clinical translational treatment of colon cancer.

Preparation, toxicity reduction and radiation therapy application of gold nanorods

Gold nanorods (GNRs) have a broad application prospect in biomedical fields because of their unique properties and controllable surface modification. The element aurum (Au) with high atomic number (high-Z) render GNRs ideal radiosensitive materials for radiation therapy and computed tomography (CT) imaging. Besides, GNRs have the capability of efficiently converting light energy to heat in the near-infrared (NIR) region for photothermal therapy. Although there are more and more researches on GNRs for radiation therapy, how to improve their biocompatibility and how to efficiently utilize them for radiation therapy should be further studied. This review will focuse on the research progress regarding the preparation and toxicity reduction of GNRs, as well as GNRs-mediated radiation therapy.

A multifunctional AIE gold cluster-based theranostic system: tumor-targeted imaging and Fenton reaction-assisted enhanced radiotherapy

BACKGROUND

As cancer is one of the main leading causes of mortality, a series of monotherapies such as chemotherapy, gene therapy and radiotherapy have been developed to overcome this thorny problem. However, a single treatment approach could not achieve satisfactory effect in many experimental explorations.

RESULTS

In this study, we report the fabrication of cyclic RGD peptide (cRGD) modified Au₄-iron oxide nanoparticle (Au₄-IO NP-cRGD) based on aggregation-induced emission (AIE) as a multifunctional theranostic system. Besides Au₄ cluster-based fluorescence imaging and enhanced radiotherapy, iron oxide (IO) nanocluster could realize magnetic resonance (MR) imaging and Fenton reaction-based chemotherapy. Abundant toxic reactive oxygen species generated from X-ray irradiation and in situ tumor-specific Fenton reaction under acidic microenvironment leads to the apoptotic and necrotic death of cancer cells. In vivo studies demonstrated good biocompatibility of Au₄-IO NP-cRGD and a high tumor suppression rate of 81.1% in the synergistic therapy group.

CONCLUSIONS

The successful dual-modal imaging and combined tumor therapy demonstrated AIE as a promising strategy for constructing multifunctional cancer theranostic platform.

Delineating the Role of Tailored Gold Nanostructures at the Biointerface

Gold (Au) has emerged as a superior element, because of its widespread applications in electronic and medical fields. The desirable physical, chemical, optical, and inherent enzyme-like properties of Au are efficiently exploited for detection, diagnostic, and therapeutic purposes. Au offers a unique advantage of fabricating gold nanostructures (GNS) having exact physical, chemical, optical, and enzyme-like properties required for the specific biomedical application. In this Review, the emerging trend of GNS for various biomedical applications is highlighted. Some notable structural and chemical modifications achieved for the detection of biomolecules, pathogens, diagnosis of diseases, and therapeutic applications are discussed in brief. The limitations of GNS during biomedical usage are highlighted and the way forward to overcome these limitations are discussed.

Gold nanotheranostics: future emblem of cancer nanomedicine

Cancer nanotheranostics aims at providing alternative approaches to traditional cancer diagnostics and therapies. In this context, plasmonic nanostructures especially gold nanostructures are intensely explored due to their tunable shape, size and surface plasmon resonance (SPR), better photothermal therapy (PTT) and photodynamic therapy (PDT) ability, effective contrast enhancing ability in Magnetic Resonance imaging (MRI) and Computed Tomography (CT) scan. Despite rapid breakthroughs in gold nanostructures based theranostics of cancer, the translation of gold nanostructures from bench side to human applications is still questionable. The major obstacles that have been facing by nanotheranostics are specific targeting, poor resolution and photoinstability during PTT etc. In this regard, various encouraging studies have been carried out recently to overcome few of these obstacles. Use of gold nanocomposites also overcomes the limitations of gold nanostructure probes and emerged as good nanotheranostic probe. Hence, the present article discusses the advances in gold nanostructures based cancer theranostics and mainly emphasizes on the importance of gold nanocomposites which have been designed to decipher the past questions and limitations of in vivo gold nanotheranostics.

Multifunctional Hybrid Hydrogel Enhanced Antitumor Therapy through Multiple Destroying DNA Functions by a Triple-Combination Synergistic Therapy

Brachytherapy, as an effective setting for precise cancer therapy in clinic, can lead to serious DNA damage. However, its therapeutic efficacy is always limited by the DNA self-repair property, tumor hypoxia-associated radiation resistance as well as inhomogeneous distribution of the radioactive material. Herein, a multifunctional hybrid hydrogel (¹³¹ I-hydrogel/DOX/GNPs aggregates) is developed by loading gold nanoparticle aggregates (GNPs aggregates) and DOX into a radionuclide iodine-131 (¹³¹ I) labelled polymeric hydrogels (¹³¹ I-PEG-P(Tyr)₈ ) for tumor destruction by completely damaging DNA self-repair functions. This hybrid hydrogel exhibits excellent photothermal/radiolabel stability, biocompatibility, and fluorescence/photothermal /SPECT imaging properties. After local injection, the sustained releasing DOX within tumor greatly inhibits the DNA replication. Meanwhile, GNPs aggregates as a radiosensitizer and photosensitizer show a significant improvement of brachytherapeutic efficacy and cause serious DNA damage. Simultaneously, GNPs aggregates induce mild photothermal therapy under 808 nm laser irradiation, which not only inhibits self-repair of the damaged DNA but also effectively relieves tumor hypoxic condition to enhance the therapeutic effects of brachytherapy, leading to a triple-synergistic destruction of DNA functions. Therefore, this study provides a highly efficient tumor synergistic therapy platform and insight into the synergistic antitumor mechanism in DNA level.

One Pot Synthesis of PEGylated Bimetallic Gold-Silver Nanoparticles for Imaging and Radiosensitization of Oral Cancers

Background

Radiotherapy is an important treatment modality for many types of head and neck squamous cell carcinomas. Nanomaterials comprised of high atomic number (Z) elements are novel radiosensitizers enhance radiation injury by production of free radicals and subsequent DNA damage. Gold nanoparticles are upcoming as promising radiosensitizers due to their high (Z) biocompatibility, and ease for surface engineering. Bimetallic nanoparticles have shown enhanced anticancer activity compared to monometallic nanoparticles.

Materials and Methods

PEG-coated Au–Ag alloy nanoparticles (BNPs) were synthesized using facile one pot synthesis techniques. Size of ~50±5nm measured by dynamic light scattering. Morphology, structural composition and elemental mapping were analyzed by electron microscopy and SAXS (small-angle X-ray scattering). The radiosensitization effects on KB oral cancer cells were evaluated by irradiation with 6MV X-rays on linear accelerator. Nuclear damage was imaged using confocal microscopy staining cells with Hoechst stain. Computed tomography (CT) contrast enhancement of BNPs was compared to that of the clinically used agent, Omnipaque.

Results

BNPs were synthesized using PEG 600 as reducing and stabilizing agent. The surface charge of well dispersed colloidal BNPs solution was −5mV. Electron microscopy reveals spherical morphology. HAADF-STEM and elemental mapping studies showed that the constituent metals were Au and Ag intermixed nanoalloy. Hydrodynamic diameter was ~50±5nm due to PEG layer and water molecules absorption. SAXS measurement confirmed BNPs size around 35nm. Raman shift of around 20 cm⁻¹ was observed when BNPs were coated with PEG. ¹H NMR showed extended involvement of ⁻OH in synthesis. BNPs efficiently enter cytoplasm of KB cells and demonstrated potent in vitro radiosensitization with enhancement ratio ~1.5–1.7. Imaging Hoechst-stained nuclei demonstrated apoptosis in a dose-dependent manner. BNPs exhibit better CT contrast enhancement ability compared to Omnipaque.

Conclusion

This bimetallic intermix nanoparticles could serve a dual function as radiosensitizer and CT contrast agent against oral cancers, and by extension possibly other cancers as well.

Development of A Decahedral Nanoenzyme Capable of Overcoming Hypoxia to Facilitate the Iodine-125 Radiosensitization of Esophageal Cancer

Radioisotopes have long been leveraged for internal radiotherapy-mediated cancer treatment. However, such therapeutic approaches are associated with serious side effects, and their efficacy is limited by intratumoral hypoxia. Herein, we prepared a folic acid-decorated palladium decahedral platform capable of enhancing the radiotherapeutic efficacy of iodine-125 (125I) seed treatment. This decahedral nanoenzyme was able to target tumor regions and catalyze the conversion of intracellular H2O2 to O2, thereby alleviating hypoxia within the tumor microenvironment. In addition, palladium was hypoxia can be alleviated, on the other hand, palladium was able to enhance the radiotherapeutic energy deposition within tumor tissues. The results of this analysis indicated that synthesized decahedral constructs can efficiently target and modify the hypoxic tumor microenvironment while simultaneously enhancing radiation energy deposition therein. Relative to palladium nanodots, the prolonged in vivo circulation of these decahedral constructs better enabled them to facilitate sustained radiosensitization. Overall, the results of this study highlight a novel approach to improving the therapeutic utility of 125I seed interstitial implantation, thus underscoring an important direction for future clinical research.

Morphological and mechanical changes induced by quercetin in human T24 bladder cancer cells

Quercetin is a flavonoid found in a great variety of foods such as vegetables and fruits. This compound has been shown to inhibit the proliferation of various types of cancer cells, as well as the growth of tumors in animal models. In the present study, we analyze morphological and mechanical changes produced by quercetin in T24 bladder cancer cells. Decreased cell viability and cell number were observed following quercetin treatment at 40 μM and 60 μM, respectively, as observed by the MTT assay and trypan blue exclusion test, supporting the hypothesis of quercetin anticancer effect. These assays also allowed us to determine the 40, 60, and 80 μM quercetin concentrations for the following analyses, Lactate Dehydrogenase assay (LDH); Nuclear Morphometric Analysis (NMA); and atomic force microscopy (AFM). The LDH assay showed no cytotoxic effect of quercetin on T24 cancer cells. The AFM showed morphological changes following quercetin treatment, namely decreased cell body, cytoplasmic retraction, and membrane condensation. Following quercetin treatment, the NMA evidenced an increased percentage of nuclei characteristic to the apoptotic and senescence processes. Cells also presented biophysical alterations consistent with cell death by apoptosis, as increased roughness and aggregation of membrane proteins, in a dose-dependent manner. Cellular elasticity, obtained through force curves, showed increased stiffness after quercetin treatment. Data presented herein demonstrate, for the first time, in a quantitative and qualitative form, the morphological and mechanical alterations induced by quercetin on bladder cancer cells.

Endocytosis of abiotic nanomaterials and nanobiovectors: Inhibition of membrane trafficking

Humans are exposed to nanoscopical nanobiovectors (e.g. coronavirus SARS-CoV-2) as well as abiotic metal/carbon-based nanomaterials that enter cells serendipitously or intentionally. Understanding the interactions of cell membranes with these abiotic and biotic nanostructures will facilitate scientists to design better functional nanomaterials for biomedical applications. Such knowledge will also provide important clues for the control of viral infections and the treatment of virus-induced infectious diseases. In the present review, the mechanisms of endocytosis are reviewed in the context of how nanomaterials are uptaken into cells. This is followed by a detailed discussion of the attributes of man-made nanomaterials (e.g. size, shape, surface functional groups and elasticity) that affect endocytosis, as well as the different human cell types that participate in the endocytosis of nanomaterials. Readers are then introduced to the concept of viruses as nature-derived nanoparticles. The mechanisms in which different classes of viruses interact with various cell types to gain entry into the human body are reviewed with examples published over the last five years. These basic tenets will enable the avid reader to design advanced drug delivery and gene transfer nanoplatforms that harness the knowledge acquired from endocytosis to improve their biomedical efficacy. The review winds up with a discussion on the hurdles to be addressed in mimicking the natural mechanisms of endocytosis in nanomaterials design.

Alpha-ketoglutarate decorated iron oxide-gold core-shell nanoparticles for active mitochondrial targeting and radiosensitization enhancement in hepatocellular carcinoma

The ability of some tumours to impart radioresistance serves as a barrier in the cancer therapeutics. Mitochondrial metabolism significantly persuades this cancer cell survival, incursion and plays a crucial role in conferring radioresistance. It would be of great importance to target the active mitochondria to overcome this resistance and achieve tumoricidal efficacy. The current report investigates the improved radiosensitization effect (under Gamma irradiation) in hepatocellular carcinoma through active mitochondrial targeting of alpha-ketoglutarate decorated iron oxide-gold core-shell nanoparticles (GNP). The loading of a chemotherapeutic drug N-(4-hydroxyphenyl)retinamide in GNP allows adjuvant chemotherapy, which further sensitizes cancerous cells for radiotherapy. The GNP shows a drug loading efficiency of 8.5 wt% with a sustained drug release kinetics. The X-Ray diffraction (XRD) pattern and High-Resolution Transmission Electron microscopy (HRTEM) indicates the synthesis of core iron oxide nanoparticles with indications of a thin layer of gold shell on the surface with 1:7 ratios of Fe: Au. The GNP application significantly reduced per cent cell viability in Hepatocellular carcinoma cells through improved radiosensitization at 5 Gy gamma radiation dose. The molecular mechanism revealed a sharp increment in reactive oxygen species (ROS) generation and DNA fragmentation. The mitochondrial targeting probes confirm the presence of GNP in the mitochondria, which could be the possible reason for such improved cellular damage. In addition to the active mitochondrial targeting, the currently fabricated nanoparticles work as a potent Magnetic Resonance Imaging (MRI)/Computed Tomography (CT) contrast agent. This multifunctional therapeutic potential makes GNP as one of the most promising theragnostic molecules in cancer therapeutics.

All-purpose nanostrategy based on dose deposition enhancement, cell cycle arrest, DNA damage, and ROS production as prostate cancer radiosensitizer for potential clinical translation

Radiotherapy (RT) is one of the main treatments for men with prostate cancer (PCa). To date, numerous sophisticated nano-formulations as radiosensitizers have been synthesized with inspiring therapeutic effects both in vitro and in vivo; however, almost all the attention has been paid on the enhanced dose deposition effect by secondary electrons of nanomaterials with high atomic numbers (Z); despite this, cell-cycle arrest, DNA damage, and also reactive oxygen species (ROS) production are critical working mechanisms that account for radiosensitization. Herein, an 'all-purpose' nanostrategy based on dose deposition enhancement, cell cycle arrest, and ROS production as prostate cancer radiosensitizer for potential clinical translation was proposed. The rather simple structure of docetaxel-loaded Au nanoparticles (NPs) with prostate specific membrane antigen (PSMA) ligand conjugation have been successfully synthesized. Enhanced cellular uptake achieved via the selective internalization of the NPs by PCa cells with positive PSMA expression could guarantee enhanced dose deposition. Moreover, the as-synthesized nanosystem could effectively arrest the cell cycle at G2/M phases, which would reduce the ability of DNA damage repair for more irradiation sensitive of the PCa cells. Moreover, the G2/M phase arrest would further promote cascade retention and the enrichment of NPs within the cells. Furthermore, ROS generation and double strand breaks greatly promoted by NPs under irradiation (IR) could also provide an underlying basis for effective radiosensitizers. In vitro and in vivo investigations confirmed the as-synthesized NPs as an effective nano-radiosensitizer with ideal safety. More importantly, all moieties within the present nanosystem have been approved by FDA for the purpose of PCa treatment, thus making it highly attractive for clinical translation.

Nanodelivery of oxiracetam enhances memory, functional recovery and induces neuroprotection following concussive head injury

Military personnel are the most susceptible to concussive head injury (CHI) caused by explosion, blast or missile or blunt head trauma. Mild to moderate CHI could induce lifetime functional and cognitive disturbances causing significant decrease in quality of life. Severe CHI leads to instant death and lifetime paralysis. Thus, further exploration of novel therapeutic agents or new features of known pharmacological agents are needed to enhance quality of life of CHI victims. Previous reports from our laboratory showed that mild CHI induced by weight drop technique causing an impact of 0.224N results in profound progressive functional deficit, memory impairment and brain pathology from 5h after trauma that continued over several weeks of injury. In this investigation we report that TiO2 nanowired delivery of oxiracetam (50mg/kg, i.p.) daily for 5 days after CHI resulted in significant improvement of functional deficit on the 8th day. This was observed using Rota Rod treadmill, memory improvement assessed by the time spent in finding hidden platform under water. The motor function improvement is seen in oxiracetam treated CHI group by placing forepaw on an inclined mesh walking and foot print analysis for stride length and distance between hind feet. TiO2-nanowired oxiracetam also induced marked improvements in the cerebral blood flow, reduction in the BBB breakdown and edema formation as well as neuroprotection of neuronal, glial and myelin damages caused by CHI at light and electron microscopy on the 7th day after 5 days TiO2 oxiracetam treatment. Adverse biochemical events such as upregulation of CSF nitrite and nitrate, IL-6, TNF-a and p-Tau are also reduced significantly in oxiracetam treated CHI group. On the other hand post treatment of 100mg/kg dose of normal oxiracetam in identical conditions after CHI is needed to show slight but significant neuroprotection together with mild recovery of memory function and functional deficits on the 8th day. These observations are the first to point out that nanowired delivery of oxiracetam has superior neuroprotective ability in CHI. These results indicate a promising clinical future of TiO2 oxiracetam in treating CHI patients for better quality of life and neurorehabilitation, not reported earlier.

Utilization of nanotechnology in targeted radionuclide cancer therapy: monotherapy, combined therapy and radiosensitization

The rapid progress of nanomedicine field has a great influence on the different tumor therapeutic trends. It achieves a potential targeting of the therapeutic agent to the tumor site with neglectable exposure of the normal tissue. In nuclear medicine, nanocarriers have been employed for targeted delivery of therapeutic radioisotopes to the malignant tissues. This systemic radiotherapy is employed to overcome the external radiation therapy drawbacks. This review overviews studies concerned with investigation of different nanoparticles as promising carriers for targeted radiotherapy. It discusses the employment of different nanovehicles for achievement of the synergistic effect of targeted radiotherapy with other tumor therapeutic modalities such as hyperthermia and photodynamic therapy. Radiosensitization utilizing different nanosensitizer loaded nanoparticles has also been discussed briefly as one of the nanomedicine approach in radiotherapy.

Intracellular Delivery of Doxorubicin by Iron Oxide-Based Nano-Constructs Increases Clonogenic Inactivation of Ionizing Radiation in HeLa Cells

In this study, we determined the potential of polyethylene glycol-encapsulated iron oxide nanoparticles (IONP_CO) for the intracellular delivery of the chemotherapeutic doxorubicin (IONP_DOX) to enhance the cytotoxic effects of ionizing radiation. The biological effects of IONP and X-ray irradiation (50 kV and 6 MV) were determined in HeLa cells using the colony formation assay (CFA) and detection of γH2AX foci. Data are presented as mean ± SEM. IONP were efficiently internalized by HeLa cells. IONP_CO radiomodulating effect was dependent on nanoparticle concentration and photon energy. IONP_CO did not radiosensitize HeLa cells with 6 MV X-rays, yet moderately enhanced cellular radiosensitivity to 50 kV X-rays (DMF_SF0.1 = 1.13 ± 0.05 (p = 0.01)). IONP_DOX did enhance the cytotoxicity of 6 MV X-rays (DMF_SF0.1 = 1.3 ± 0.1; p = 0.0005). IONP treatment significantly increased γH2AX foci induction without irradiation. Treatment of HeLa cells with IONP_CO resulted in a radiosensitizing effect for low-energy X-rays, while exposure to IONP_DOX induced radiosensitization compared to IONP_CO in cells irradiated with 6 MV X-rays. The effect did not correlate with the induction of γH2AX foci. Given these results, IONP are promising candidates for the controlled delivery of DOX to enhance the cytotoxic effects of ionizing radiation.

Folic Acid-Conjugated Gold Nanostars for Computed Tomography Imaging and Photothermal/Radiation Combined Therapy

Fabrication of multifunctional nanoprobes, which integrate tumor targeting, imaging, and effective treatment, has been widely explored in nanomedicine. In the present study, we fabricated tumor-targeting polymer folic acid-terminated polyethylene glycol thiol-modified gold nanostars (GNS-FA), which could realize X-ray computed tomography (CT) imaging and PTT/RT synergistic therapy. The synthesized GNS-FA exhibited good biocompatibility. GNS-FA could be used as a CT imaging contrast agent due to the strong X-ray attenuation of Au. GNS-FA exhibited good near-infrared (NIR) light absorption and excellent photothermal conversion performance, making them promising photothermal transduction agents (PTAs). Furthermore, GNS-FA could be used as an RT sensitizer to enhance the radio-mediated cell death due to the high atomic number (high Z) of gold. Hence, GNS-FA were used as the CT imaging agent, PTA, and radiosensitizer in this work. The in vitro antitumor experiments showed that the PTT/RT combined treatment had enhanced anticancer efficacy compared with the monotherapy (PTT or RT). Our results indicated that the bioconjugated GNS could offer an excellent nanoplatform for CT imaging-guided PTT/RT combined cancer therapy in the future.