Gold Nanoparticles as a Potent Radiosensitizer: A Transdisciplinary Approach from Physics to Patient

Nonpersistent Nanoarchitectures Enhance Concurrent Chemoradiotherapy in an Immunocompetent Orthotopic Model of HPV+ Head/Neck Carcinoma

Cisplatin chemoradiotherapy (CRT) is the established standard of care for managing locally advanced human papillomavirus-positive head/neck carcinoma. The typically young patients may suffer serious and long-time side effects caused by the treatment, such as dysphagia, and hearing loss. Thus, ensuring a satisfactory post-treatment quality of life is paramount. One potential replacing approach to the classical CRT involves the combination of standard-dose radiotherapy and radiosensitizers such as noble metal nanoparticles (NPs). However, several concerns about size, shape, and biocompatibility limit the translation of metal nanomaterials to the clinical practice. Here, it is demonstrated that a new model of nonpersistent gold nanoarchitectures containing cisplatin (NAs-Cluster-CisPt) generates, in combination with radiotherapy, a significant in vivo tumor-reducing effect compared to the standard CRT, achieving a complete tumor clearance in 25% of the immunocompetent models that persist for 60 days. These findings, together with the negligible amount of metals recognized in the excretory organs, highlight that the concurrent administration of NAs-Cluster-CisPt and radiotherapy has the potential to overcome some clinical limitations associated to NP-based approaches while enhancing the treatment outcome with respect to standard CRT. Overall, despite further mechanistic investigations being essential, these data support the exploiting of nonpersistent metal-nanomaterial-mediated approaches for oral cancer management.

211At on gold nanoparticles for targeted radionuclide therapy application

Targeted alpha therapy (TAT) is a methodology that is being developed as a promising cancer treatment using the α-particle decay of radionuclides. This technique involves the use of heavy radioactive elements being placed near the cancer target area to cause maximum damage to the cancer cells while minimizing the damage to healthy cells. Using gold nanoparticles (AuNPs) as carriers, a more effective therapy methodology may be realized. AuNPs can be good candidates for transporting these radionuclides to the vicinity of the cancer cells since they can be labeled not just with the radionuclides, but also a host of other proteins and ligands to target these cells and serve as additional treatment options. Research has shown that astatine and iodine are capable of adsorbing onto the surface of gold, creating a covalent bond that is quite stable for use in experiments. However, there are still many challenges that lie ahead in this area, whether they be theoretical, experimental, and even in real-life applications. This review will cover some of the major developments, as well as the current state of technology, and the problems that need to be tackled as this research topic moves along to maturity. The hope is that with more workers joining the field, we can make a positive impact on society, in addition to bringing improvement and more knowledge to science.

Comparison of the effectiveness of two piperazine based nano-catalysts in the synthesis of benzoxazoles and benzimidazoles and use of the powerful one in the N-Boc protection of amines

In this work, a comparison between the catalytic activity of two piperazine based ionic liquids immobilized on ZnO NPs and SiO2 NPs is presented in the synthesis of benzoxazoles and benzimidazoles. These reactions are performed under solvent free conditions during appropriate reaction times with high yields. The catalyst obtained from ZnO-NPs (PINZS), as the more efficient one, is used for the efficient promotion of the N-Boc protection of amines. High chemoselectivity, no by-products, facile separation of the catalyst, short reaction times and no need for volatile organic solvents are the best features of the proposed methods.

An Optimized Method for Evaluating the Potential Gd-Nanoparticle Dose Enhancement Produced by Electronic Brachytherapy

This work reports an optimized method to experimentally quantify the Gd-nanoparticle dose enhancement generated by electronic brachytherapy. The dose enhancement was evaluated considering energy beams of 50 kVp and 70 kVp, determining the Gd-nanoparticle concentration ranges that would optimize the process for each energy. The evaluation was performed using delaminated radiochromic films and a Poly(methyl methacrylate) (PMMA) phantom covered on one side by a thin 2.5 μm Mylar filter acting as an interface between the region with Gd suspension and the radiosensitive film substrate. The results for the 70 kVp beam quality showed dose increments of 6±6%, 22±7%, and 9±7% at different concentrations of 10, 20, and 30 mg/mL, respectively, verifying the competitive mechanisms of enhancement and attenuation. For the 50 kVp beam quality, no increase in dose was recorded for the concentrations studied, indicating that the major contribution to enhancement is from the K-edge interaction. In order to separate the contributions of attenuation and enhancement to the total dose, measurements were replicated with a 12 μm Mylar filter, obtaining a dose enhancement attributable to the K-edge of 29±7% and 34±7% at 20 and 30 mg/mL, respectively, evidencing a significant additional dose proportional to the Gd concentration.

Sarcoma cell-specific radiation sensitization by titanate scrolled nanosheets: insights from physicochemical analysis and transcriptomic profiling

This study aimed to explore the potential of metal oxides such as Titanate Scrolled Nanosheets (TNs) in improving the radiosensitivity of sarcoma cell lines. Enhancing the response of cancer cells to radiation therapy is crucial, and one promising approach involves utilizing metal oxide nanoparticles. We focused on the impact of exposing two human sarcoma cell lines to both TNs and ionizing radiation (IR). Our research was prompted by previous in vitro toxicity assessments, revealing a correlation between TNs' toxicity and alterations in intracellular calcium homeostasis. A hydrothermal process using titanium dioxide powder in an alkaline solution produced the TNs. Our study quantified the intracellular content of TNs and analyzed their impact on radiation-induced responses. This assessment encompassed PIXE analysis, cell proliferation, and transcriptomic analysis. We observed that sarcoma cells internalized TNs, causing alterations in intracellular calcium homeostasis. We also found that irradiation influence intracellular calcium levels. Transcriptomic analysis revealed marked disparities in the gene expression patterns between the two sarcoma cell lines, suggesting a potential cell-line-dependent nano-sensitization to IR. These results significantly advance our comprehension of the interplay between TNs, IR, and cancer cells, promising potential enhancement of radiation therapy efficiency.

A review on metal complexes and its anti-cancer activities: Recent updates from in vivo studies

Research into cancer therapeutics has uncovered various potential medications based on metal-containing scaffolds after the discovery and clinical applications of cisplatin as an anti-cancer agent. This has resulted in many metallodrugs that can be put into medical applications. These metallodrugs have a wider variety of functions and mechanisms of action than pure organic molecules. Although platinum-based medicines are very efficient anti-cancer agents, they are often accompanied by significant side effects and toxicity and are limited by resistance. Some of the most studied and developed alternatives to platinum-based anti-cancer medications include metallodrugs based on ruthenium, gold, copper, iridium, and osmium, which showed effectiveness against many cancer cell lines. These metal-based medicines represent an exciting new category of potential cancer treatments and sparked a renewed interest in the search for effective anti-cancer therapies. Despite the widespread development of metal complexes touted as powerful and promising in vitro anti-cancer therapeutics, only a small percentage of these compounds have shown their worth in vivo models. Metallodrugs, which are more effective and less toxic than platinum-based drugs and can treat drug-resistant cancer cells, are the focus of this review. Here, we highlighted some of the most recently developed Pt, Ru, Au, Cu, Ir, and Os complexes that have shown significant in vivo antitumor properties between 2017 and 2023.

Assembling Au8 clusters on surfaces of bifunctional nanoimmunomodulators for synergistically enhanced low dose radiotherapy of metastatic tumor

BACKGROUND

Radiotherapy is one of the mainstays of cancer therapy and has been used for treating 65-75% of patients with solid tumors. However, radiotherapy of tumors has two limitations: high-dose X-rays damage adjacent normal tissue and tumor metastases cannot be prevented.

RESULTS

Therefore, to overcome the two limitations of radiotherapy, a multifunctional core-shell R837/BMS@Au8 nanoparticles as a novel radiosensitizer were fabricated by assembling Au8NCs on the surface of a bifunctional nanoimmunomodulator R837/BMS nanocore using nanoprecipitation followed by electrostatic assembly. Formed R837/BMS@Au8 NP composed of R837, BMS-1, and Au8 clusters. Au8NC can enhance X-ray absorption at the tumor site to reduce X-ray dose and releases a large number of tumor-associated antigens under X-ray irradiation. With the help of immune adjuvant R837, dendritic cells can effectively process and present tumor-associated antigens to activate effector T cells, meanwhile, a small-molecule PD-L1 inhibitor BMS-1 can block PD-1/PD-L1 pathway to reactivate cytotoxic T lymphocyte, resulting in a strong systemic antitumor immune response that is beneficial for limiting tumor metastasis. According to in vivo and in vitro experiments, radioimmunotherapy based on R837/BMS@Au8 nanoparticles can increase calreticulin expression on of cancer cells, reactive oxygen species generation, and DNA breakage and decrease colony formation. The results revealed that distant tumors were 78.2% inhibited depending on radioimmunotherapy of primary tumors. Therefore, the use of a novel radiosensitizer R837/BMS@Au8 NPs realizes low-dose radiotherapy combined with immunotherapy against advanced cancer.

CONCLUSION

In conclusion, the multifunctional core-shell R837/BMS@Au8 nanoparticles as a novel radiosensitizer effectively limiting tumor metastasis and decrease X-ray dose to 1 Gy, providing an efective strategy for the construction of nanosystems with radiosensitizing function.

Morphological Effects and In Vitro Biological Mechanisms of Radiation-Induced Cell Killing by Gold Nanomaterials

Gold nanomaterials have been shown to augment radiation therapy both in vitro and in vivo. However, studies on these materials are mostly phenomenological due to nanoparticle heterogeneity and the complexity of biological systems. Even accurate quantification of the particle dose still results in bulk average biases; the effect on individual cells is not measured but rather the effect on the overall population. To perform quantitative nanobiology, we coated glass coverslips uniformly at varying densities with Au nanoparticle preparations with different morphologies (45 nm cages, 25 nm spheres, and 30 nm rods). Consequently, the effect of a specific number of particles per unit area in contact with breast cancer cells growing on the coated surfaces was ascertained. Gold nanocages showed the highest degree of radiosensitization on a per particle basis, followed by gold nanospheres and gold nanorods, respectively. All three materials showed little cytotoxic effect at 0 Gy, but clonogenic survival decreased proportionally with the radiation dose and particle coverage density. A similar trend was seen in vivo in the combined treatment antitumor response in 4T1 tumor-bearing animals. The presence of gold affected the type and quantity of reactive oxygen species generated, specifically superoxide and hydroxyl radicals, and the concentration of nanocages correlated with the development of more numerous double-stranded DNA breaks and increased protein oxidation as measured by carbonylation. This work demonstrates the dependence on morphology and concentration of radiation enhancement by gold nanomaterials and may lead to a novel method to differentiate intra- and extracellular functionalities of gold nanomedicine treatment strategies. It further provides insights that can guide the rational development of gold nanomaterial-based radiosensitizers for clinical use.

X-ray radio-enhancement by Ti3C2Tx MXenes in soft tissue sarcoma

Radiotherapy is a cornerstone of cancer treatment. However, due to the low tissue specificity of ionizing radiation, damage to the surrounding healthy tissue of the tumor remains a significant challenge. In recent years, radio-enhancers based on inorganic nanomaterials have gained considerable interest. Beyond the widely explored metal and metal oxide nanoparticles, 2D materials, such as MXenes, could present potential benefits because of their inherently large specific surface area. In this study, we highlight the promising radio-enhancement properties of Ti3C2Tx MXenes. We demonstrate that atomically thin layers of titanium carbides (Ti3C2Tx MXenes) are efficiently internalized and well-tolerated by mammalian cells. Contrary to MXenes suspended in aqueous buffers, which fully oxidize within days, yielding rice-grain shaped rutile nanoparticles, the MXenes internalized by cells oxidize at a slower rate. This is consistent with cell-free experiments that have shown slower oxidation rates in cell media and lysosomal buffers compared to dispersants without antioxidants. Importantly, the MXenes exhibit robust radio-enhancement properties, with dose enhancement factors reaching up to 2.5 in human soft tissue sarcoma cells, while showing no toxicity to healthy human fibroblasts. When compared to oxidized MXenes and commercial titanium dioxide nanoparticles, the intact 2D titanium carbide flakes display superior radio-enhancement properties. In summary, our findings offer evidence for the potent radio-enhancement capabilities of Ti3C2Tx MXenes, marking them as a promising candidate for enhancing radiotherapy.

Nanoparticle-Mediated Radiotherapy: Unraveling Dose Enhancement and Apoptotic Responses in Cancer and Normal Cell Lines

Cervical cancer remains a pressing global health concern, necessitating advanced therapeutic strategies. Radiotherapy, a fundamental treatment modality, has faced challenges such as targeted dose deposition and radiation exposure to healthy tissues, limiting optimal outcomes. To address these hurdles, nanomaterials, specifically gold nanoparticles (AuNPs), have emerged as a promising avenue. This study delves into the realm of cervical cancer radiotherapy through the meticulous exploration of AuNPs' impact. Utilizing ex vivo experiments involving cell lines, this research dissected intricate radiobiological interactions. Detailed scrutiny of cell survival curves, dose enhancement factors (DEFs), and apoptosis in both cancer and normal cervical cells revealed profound insights. The outcomes showcased the substantial enhancement of radiation responses in cancer cells following AuNP treatment, resulting in heightened cell death and apoptotic levels. Significantly, the most pronounced effects were observed 24 h post-irradiation, emphasizing the pivotal role of timing in AuNPs' efficacy. Importantly, AuNPs exhibited targeted precision, selectively impacting cancer cells while preserving normal cells. This study illuminates the potential of AuNPs as potent radiosensitizers in cervical cancer therapy, offering a tailored and efficient approach. Through meticulous ex vivo experimentation, this research expands our comprehension of the complex dynamics between AuNPs and cells, laying the foundation for their optimized clinical utilization.

Catalase-gold nanoaggregates manipulate the tumor microenvironment and enhance the effect of low-dose radiation therapy by reducing hypoxia

Radiotherapy as a standard method for cancer treatment faces tumor recurrence and antitumoral unresponsiveness. Suppressive tumor microenvironment (TME) and hypoxia are significant challenges affecting efficacy of radiotherapy. Herein, a versatile method is introduced for the preparation of pH-sensitive catalase-gold cross-linked nanoaggregate (Au@CAT) having acceptable stability and selective activity in tumor microenvironment. Combining Au@CAT with low-dose radiotherapy enhanced radiotherapy effects via polarizing protumoral immune cells to the antitumoral landscape. This therapeutic approach also attenuated hypoxia, confirmed by downregulating hypoxia hallmarks, such as hypoxia-inducible factor α-subunits (HIF-α), vascular endothelial growth factor (VEGF), and EGF. Catalase stability against protease digestion was improved significantly in Au@CAT compared to the free catalase. Moreover, minimal toxicity of Au@CAT on normal cells and increased reactive oxygen species (ROS) were confirmed in vitro compared with radiotherapy. Using the nanoaggregates combined with radiotherapy led to a significant reduction of immunosuppressive infiltrating cells such as myeloid-derived suppressor cells (MDSCs) and regulatory T cells (T-regs) compared to the other groups. While, this combined therapy could significantly increase the frequency of CD8+ cells as well as M1 to M2 macrophages (MQs) ratio. The combination therapy also reduced the tumor size and increased survival rate in mice models of colorectal cancer (CRC). Our results indicate that this innovative nanocomposite could be an excellent system for catalase delivery, manipulating the TME and providing a potential therapeutic strategy for treating CRC.

Prospects of nanoparticle-based radioenhancement for radiotherapy

Radiotherapy is a key pillar of solid cancer treatment. Despite a high level of conformal dose deposition, radiotherapy is limited due to co-irradiation of organs at risk and subsequent normal tissue toxicities. Nanotechnology offers an attractive opportunity for increasing the efficacy and safety of cancer radiotherapy. Leveraging the freedom of design and the growing synthetic capabilities of the nanomaterial-community, a variety of engineered nanomaterials have been designed and investigated as radiosensitizers or radioenhancers. While research so far has been primarily focused on gold nanoparticles and other high atomic number materials to increase the absorption cross section of tumor tissue, recent studies are challenging the traditional concept of high-Z nanoparticle radioenhancers and highlight the importance of catalytic activity. This review provides a concise overview on the knowledge of nanoparticle radioenhancement mechanisms and their quantification. It critically discusses potential radioenhancer candidate materials and general design criteria for different radiation therapy modalities, and concludes with research priorities in order to advance the development of nanomaterials, to enhance the efficacy of radiotherapy and to increase at the same time the therapeutic window.

Metal Ions Modify In Vitro DNA Damage Yields with High-LET Radiation

Cu2+ and Co2+ are metals known to increase DNA damage in the presence of hydrogen peroxide through a Fenton-type reaction. We hypothesized that these metals could increase DNA damage following irradiations of increasing LET values as hydrogen peroxide is a product of the radiolysis of water. The reaction mixtures contain either double- or single-stranded DNA in solution with Cu2+ or Co2+ and were irradiated either with X-ray, carbon-ion or iron-ion beams, or they were treated with hydrogen peroxide or bleomycin at increasing radiation dosages or chemical concentrations. DNA damage was then assessed via gel electrophoresis followed with a band intensity analysis. DNA damage was the greatest when DNA in the solution with either metal was treated with only hydrogen peroxide followed by the DNA damage of DNA in the solution with either metal post irradiation of low-LET (X-Ray) or high-LET (carbon-ion and iron-ion), respectively, and demonstrated the least damage after treatment with bleomycin. Cu2+ portrayed greater DNA damage than Co2+ following all experimental conditions. The metals' effect caused more DNA damage and was observed to be LET-dependent for single-strand break formation but inversely dependent for double-strand break formation. These results suggest that Cu2+ is more efficient than Co2+ at inducing both DNA single-strand and double-strand breaks following all irradiations and chemical treatments.

Surface Chemistry and Specific Surface Area Rule the Efficiency of Gold Nanoparticle Sensitizers in Proton Therapy

Gold nanoparticles (AuNPs) are currently the most studied radiosensitizers in proton therapy (PT) applicable for the treatment of solid tumors, where they amplify production of reactive oxygen species (ROS). However, it is underexplored how this amplification is correlated with the AuNPs' surface chemistry. To clarify this issue, we fabricated ligand-free AuNPs of different mean diameters by laser ablation in liquids (LAL) and laser fragmentation in liquids (LFL) and irradiated them with clinically relevant proton fields by using water phantoms. ROS generation was monitored by the fluorescent dye 7-OH-coumarin. Our findings reveal an enhancement of ROS production driven by I) increased total particle surface area, II) utilization of ligand-free AuNPs avoiding sodium citrate as a radical quencher ligands, and III) a higher density of structural defects generated by LFL synthesis, indicated by surface charge density. Based on these findings it may be concluded that the surface chemistry is a major and underexplored contributor to ROS generation and sensitizing effects of AuNPs in PT. We further highlight the applicability of AuNPs in vitro in human medulloblastoma cells.

Radiation-activated nanoparticles: Which combination to optimize radiosensitization?

Radiotherapy plays a crucial role in the treatment of various cancers. With the ongoing technological advancements in radiotherapy equipment, allowing for increasingly precise targeting of tumours, there are numerous strategies being explored to enhance its effectiveness by combining it with other therapies. Among these, metal nanoparticles seem to have a promising future driven by their ability to locally amplify the dose deposited by ionizing radiation, and to radiosensitize cells by modifying their oxidative status. Recent advancements in understanding the mechanisms of action of these nanoparticles have provided valuable insights for the development of new therapeutic combinations. Among these, the combination with immunotherapies would make it possible to benefit both from the amplified local effect of radiotherapy by nanoparticles and to induce a better antitumour immune response. In this article, we review shortly the existing literature on ongoing combinations and suggest potential novel therapies associated with the combination of radiotherapy and nanoparticles.

Gold-Enhanced Brachytherapy by a Nanoparticle-Releasing Hydrogel and 3D-Printed Subcutaneous Radioactive Implant Approach

Brachytherapy (BT) is a widely used clinical procedure for localized cervical cancer treatment. In addition, gold nanoparticles (AuNPs) have been demonstrated as powerful radiosensitizers in BT procedures. Prior to irradiation by a BT device, their delivery to tumors can enhance the radiation effect by generating low-energy photons and electrons, leading to reactive oxygen species (ROS) production, lethal to cells. No efficient delivery system has been proposed until now for AuNP topical delivery to localized cervical cancer in the context of BT. This article reports an original approach developed to accelerate the preclinical studies of AuNP-enhanced BT procedures. First, an AuNP-containing hydrogel (Pluronic F127, alginate) is developed and tested in mice for degradation, AuNP release, and biocompatibility. Then, custom-made 3D-printed radioactive BT inserts covered with a AuNP-containing hydrogel cushion are designed and administered by surgery in mice (HeLa xenografts), which allows for measuring AuNP penetration in tumors (≈100 µm), co-registered with the presence of ROS produced through the interactions of radiation and AuNPs. Biocompatible AuNPs-releasing hydrogels could be used in the treatment of cervical cancer prior to BT, with impact on  the total amount of radiation needed per BT treatment, which will result in benefits to the preservation of healthy tissues surrounding cancer.

Applications and safety of gold nanoparticles as therapeutic devices in clinical trials

Use of gold nanoparticles (GNPs) in medicine is an emerging field of translational research with vast clinical implications and exciting therapeutic potential. However, the safety of using GNPs in human subjects is an important question that remains unanswered. This study reviews over 20 clinical trials focused on GNP safety and aims to summarize all the clinical studies, completed and ongoing, to identify whether GNPs are safe to use in humans as a therapeutic platform. In these studies, GNPs were implemented as drug delivery devices, for photothermal therapy, and utilized for their intrinsic therapeutic effects by various routes of delivery. These studies revealed no major safety concerns with the use of GNPs; however, the number of trials and total patient number remains limited. Multi-dose, multi-center blinded trials are required to deepen our understanding of the use of GNPs in clinical settings to facilitate translation of this novel, multifaceted therapeutic device. Expanding clinical trials will require collaboration between clinicians, scientists, and biotechnology companies.

Tuning ultrasmall theranostic nanoparticles for MRI contrast and radiation dose amplification

Background: The introduction of magnetic resonance (MR)-guided radiation treatment planning has opened a new space for theranostic nanoparticles to reduce acute toxicity while improving local control. In this work, second-generation AGuIX® nanoparticles (AGuIX-Bi) are synthesized and validated. AGuIX-Bi are shown to maintain MR positive contrast while further amplifying the radiation dose by the replacement of some Gd3+ cations with higher Z Bi3+. These next-generation nanoparticles are based on the AGuIX® platform, which is currently being evaluated in multiple Phase II clinical trials in combination with radiotherapy. Methods: In this clinically scalable methodology, AGuIX® is used as an initial chelation platform to exchange Gd3+ for Bi3+. AGuIX-Bi nanoparticles are synthesized with three ratios of Gd/Bi, each maintaining MR contrast while further amplifying radiation dose relative to Bi3+. Safety, efficacy, and theranostic potential of the nanoparticles were evaluated in vitro and in vivo in a human non-small cell lung cancer model. Results: We demonstrated that increasing Bi3+ in the nanoparticles is associated with more DNA damage and improves in vivo efficacy with a statistically significant delay in tumor growth and 33% complete regression for the largest Bi/Gd ratio tested. The addition of Bi3+ by our synthetic method leads to nanoparticles that present slightly altered pharmacokinetics and lengthening of the period of high tumor accumulation with no observed evidence of toxicity. Conclusions: We confirmed the safety and enhanced efficacy of AGuIX-Bi with radiation therapy at the selected ratio of 30Gd/70Bi. These results provide crucial evidence towards patient translation.

Novel platform for subcutaneous tumor irradiation in mice

Preclinical development of cancer treatments including radiotherapy (RT) is now crucial to optimize all the treatment aspects for a better efficacy and to help clinicians to build new clinical trials based on robust results. More and more teams use preclinical irradiators to deliver radiotherapy in a comparable way to clinical treatments (image-based RT, arc therapy, stereotactic body RT…). In daily conditions, users usually need to develop easy to use techniques (for applicator technicians for example), allowing to treat many mice per day with a high level of reproducibility. Besides, the best compromise between a satisfying dose coverage to the tumor and nearby organs at risk sparing has to be ensured. We describe here new a home-made immobilization device to irradiate grafted tumors, as well as the different steps to develop the treatment planning and generate an easy procedure to routinely irradiate subcutaneous tumor model.

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

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

Gold-Nanoparticles-Enhanced Production of Reactive Oxygen Species in Cells at Spread-Out Bragg Peak under Proton Beam Radiation

This study investigates the radiobiological effects of gold nanoparticles (GNPs) as radiosensitizers for proton beam therapy (PBT). Specifically, we explore the enhanced production of reactive oxygen species (ROS) in GNP-loaded tumor cells irradiated by a 230 MeV proton beam in a spread-out Bragg peak (SOBP) zone obtained by a passive scattering system. Our findings indicate that the radiosensitization enhancement factor is 1.24 at 30% cell survival fraction, 8 days after 6 Gy proton beam irradiation. Since protons deposit the majority of their energy at the SOBP region and interact with GNPs to induce more ejected electrons from the high-Z GNPs, these ejected electrons then react with water molecules to produce excessive ROS that can damage cellular organelles. Laser scanning confocal microscopy reveals the excessive ROS induced inside the GNP-loaded cells immediately after proton irradiation. Furthermore, the damage to cytoskeletons and mitochondrial dysfunction in GNP-loaded cells caused by the induced ROS becomes significantly severe, 48 h after proton irradiation. Our biological evidence suggests that the cytotoxicity of GNP-enhanced ROS production has the potential to increase the tumoricidal efficacy of PBT.

Application of nano-radiosensitizers in combination cancer therapy

Radiosensitizers are compounds or nanostructures, which can improve the efficiency of ionizing radiation to kill cells. Radiosensitization increases the susceptibility of cancer cells to radiation-induced killing, while simultaneously reducing the potentially damaging effect on the cellular structure and function of the surrounding healthy tissues. Therefore, radiosensitizers are therapeutic agents used to boost the effectiveness of radiation treatment. The complexity and heterogeneity of cancer, and the multifactorial nature of its pathophysiology has led to many approaches to treatment. The effectiveness of each approach has been proven to some extent, but no definitive treatment to eradicate cancer has been discovered. The current review discusses a broad range of nano-radiosensitizers, summarizing possible combinations of radiosensitizing NPs with several other types of cancer therapy options, focusing on the benefits and drawbacks, challenges, and future prospects.

Radiation therapy-activated nanoparticle and immunotherapy: The next milestone in oncology?

Radiotherapy (RT) is a fundamental treatment at the locoregional or oligometastatic stages of cancer. In various tumors, RT effects may be optimized using synergistic combinations that enhance tumor response. Innovative strategies have been designed that explore the radiation mechanisms, at the physical, chemical and biological levels, to propose precision RT approaches. They consist in combining RT with immunotherapy to revert radiation immunosuppressive effects or to enhance radiation-induced immune defenses against the tumor to favor immunogenic cell death. Radiotherapy-activated nanoparticles are another innovation. By increasing radiation response in situ, nanoparticles improve tumor control locally, and can trigger systemic immune reactions that may be exploited to improve the systemic efficacy of RT. Strong clinical evidence of improved outcomes is now available for combinations of RT and immunotherapy on one hand and RT and nanoparticles on the other hand. The triple combination of RT, immunotherapy and nanoparticles is promising in terms of tolerance, local and systemic anti-tumor control. Yet, significant challenges remain to unravel the complexity of the multiscale mechanisms underlying response to this combination and their associated parameters. Such parameters include patient characteristics, tumor bulk and histology, radiation technique, energy, dose, fractionation, immunotherapy targets and predictive biomarkers, nanoparticle type, size, delivery (intratumoral/intravenous), distribution. The temporal combination is another critical parameter. The mechanisms of response of the combinatorial approaches are reviewed, with a focus on underlying mechanisms based on preclinical, translational and clinical studies. Opportunities for translation of current understanding into precision RT trials combined with immunotherapy and nanoparticles are also discussed.

Nanomaterial-Based Antivascular Therapy in the Multimodal Treatment of Cancer

Abnormal tumor vasculature and a hypoxic tumor microenvironment (TME) limit the effectiveness of conventional cancer treatment. Recent studies have shown that antivascular strategies that focus on antagonizing the hypoxic TME and promoting vessel normalization effectively synergize to increase the antitumor efficacy of conventional therapeutic regimens. By integrating multiple therapeutic agents, well-designed nanomaterials exhibit great advantages in achieving higher drug delivery efficiency and can be used as multimodal therapy with reduced systemic toxicity. In this review, strategies for the nanomaterial-based administration of antivascular therapy combined with other common tumor treatments, including immunotherapy, chemotherapy, phototherapy, radiotherapy, and interventional therapy, are summarized. In particular, the administration of intravascular therapy and other therapies with the use of versatile nanodrugs is also described. This review provides a reference for the development of multifunctional nanotheranostic platforms for effective antivascular therapy in combined anticancer treatments.

Application of nanotechnology in reversing therapeutic resistance and controlling metastasis of colorectal cancer

Colorectal cancer (CRC) is the most common digestive malignancy across the world. Its first-line treatments applied in the routine clinical setting include surgery, chemotherapy, radiotherapy, targeted therapy, and immunotherapy. However, resistance to therapy has been identified as the major clinical challenge that fails the treatment method, leading to recurrence and distant metastasis. An increasing number of studies have been attempting to explore the underlying mechanisms of the resistance of CRC cells to different therapies, which can be summarized into two aspects: (1) The intrinsic characters and adapted alterations of CRC cells before and during treatment that regulate the drug metabolism, drug transport, drug target, and the activation of signaling pathways; and (2) the suppressive features of the tumor microenvironment (TME). To combat the issue of therapeutic resistance, effective strategies are warranted with a focus on the restoration of CRC cells’ sensitivity to specific treatments as well as reprogramming impressive TME into stimulatory conditions. To date, nanotechnology seems promising with scope for improvement of drug mobility, treatment efficacy, and reduction of systemic toxicity. The instinctive advantages offered by nanomaterials enable the diversity of loading cargoes to increase drug concentration and targeting specificity, as well as offer a platform for trying the combination of different treatments to eventually prevent tumor recurrence, metastasis, and reversion of therapy resistance. The present review intends to summarize the known mechanisms of CRC resistance to chemotherapy, radiotherapy, immunotherapy, and targeted therapy, as well as the process of metastasis. We have also emphasized the recent application of nanomaterials in combating therapeutic resistance and preventing metastasis either by combining with other treatment approaches or alone. In summary, nanomedicine is an emerging technology with potential for CRC treatment; hence, efforts should be devoted to targeting cancer cells for the restoration of therapeutic sensitivity as well as reprogramming the TME. It is believed that the combined strategy will be beneficial to achieve synergistic outcomes contributing to control and management of CRC in the future.

Recent Advances in Metal-Based NanoEnhancers for Particle Therapy

Radiotherapy is one of the most common therapeutic regimens for cancer treatment. Over the past decade, proton therapy (PT) has emerged as an advanced type of radiotherapy (RT) that uses proton beams instead of conventional photon RT. Both PT and carbon-ion beam therapy (CIBT) exhibit excellent therapeutic results because of the physical characteristics of the resulting Bragg peaks, which has been exploited for cancer treatment in medical centers worldwide. Although particle therapies show significant advantages to photon RT by minimizing the radiation damage to normal tissue after the tumors, they still cause damage to normal tissue before the tumor. Since the physical mechanisms are different from particle therapy and photon RT, efforts have been made to ameliorate these effects by combining nanomaterials and particle therapies to improve tumor targeting by concentrating the radiation effects. Metallic nanoparticles (MNPs) exhibit many unique properties, such as strong X-ray absorption cross-sections and catalytic activity, and they are considered nano-radioenhancers (NREs) for RT. In this review, we systematically summarize the putative mechanisms involved in NRE-induced radioenhancement in particle therapy and the experimental results in in vitro and in vivo models. We also discuss the potential of translating preclinical metal-based NP-enhanced particle therapy studies into clinical practice using examples of several metal-based NREs, such as SPION, Abraxane, AGuIX, and NBTXR3. Furthermore, the future challenges and development of NREs for PT are presented for clinical translation. Finally, we propose a roadmap to pursue future studies to strengthen the interplay of particle therapy and nanomedicine.

Gold Nanorods Inhibit Tumor Metastasis by Regulating MMP-9 Activity: Implications for Radiotherapy

Dysregulation of matrix metalloproteinase (MMP) is strongly implicated in tumor invasion and metastasis. Nanomaterials can interact with proteins and have impacts on protein activity, which provides a potential strategy for inhibiting tumor invasion and metastasis. However, the regulation of MMP activity by nanomaterials has not been fully determined. Herein, we have found that gold nanorods (Au NRs) are able to induce the change of the secondary structure of MMP-9 and thereby inhibit their activity. Interestingly, the inhibition of MMP-9 activity is highly dependent on the aspect ratio of Au NRs, and an aspect ratio of 3.3 shows the maximum inhibition efficiency. Molecular dynamics simulations combined with mathematical statistics algorithm reveal the binding behaviors and interaction modes of MMP-9 with Au NRs in atomic details and disclose the mechanism of aspect ratio-dependent inhibition effect of Au NRs on MMP-9 activity. Au NRs with an aspect ratio of 3.3 successfully suppress the X-ray-activated invasion and metastasis of tumor by inhibiting MMP-9 activity. Our findings provide important guidance for the modulation of MMP-9 activity by tuning key parameters of nanomaterials and demonstrate that gold nanorods could be developed as potential MMP inhibitors.

Radiosensitization with Gadolinium Chelate-Coated Gold Nanoparticles Prevents Aggressiveness and Invasiveness in Glioblastoma

Purpose

This study aimed to evaluate the radiosensitizing potential of Au@DTDTPA(Gd) nanoparticles when combined with conventional external X-ray irradiation (RT) to treat GBM.

Methods

Complementary biological models based on U87 spheroids including conventional 3D invasion assay, organotypic brain slice cultures, chronic cranial window model were implemented to investigate the impact of RT treatments (10 Gy single dose; 5×2 Gy or 2×5 Gy) combined with Au@DTDTPA(Gd) nanoparticles on tumor progression. The main tumor mass and its infiltrative area were analyzed. This work focused on the invading cancer cells after irradiation and their viability, aggressiveness, and recurrence potential were assessed using mitotic catastrophe quantification, MMP secretion analysis and neurosphere assays, respectively.

Results

In vitro clonogenic assays showed that Au@DTDTPA(Gd) nanoparticles exerted a radiosensitizing effect on U87 cells, and in vivo experiments suggested a benefit of the combined treatment "RT 2×5 Gy + Au@DTDTPA(Gd)" compared to RT alone. Invasion assays revealed that invasion distance tended to increase after irradiation alone, while the combined treatments were able to significantly reduce tumor invasion. Monitoring of U87-GFP tumor progression using organotypic cultures or intracerebral grafts confirmed the anti-invasive effect of Au@DTDTPA(Gd) on irradiated spheroids. Most importantly, the combination of Au@DTDTPA(Gd) with irradiation drastically reduced the number, the viability and the aggressiveness of tumor cells able to escape from U87 spheroids. Notably, the combined treatments significantly reduced the proportion of escaped cells with stem-like features that could cause recurrence.

Conclusion

Combining Au@DTDTPA(Gd) nanoparticles and X-ray radiotherapy appears as an attractive therapeutic strategy to decrease number, viability and aggressiveness of tumor cells that escape and can invade the surrounding brain parenchyma. Hence, Au@DTDTPA(Gd)-enhanced radiotherapy opens up interesting perspectives for glioblastoma treatment.

New Frontiers in Colorectal Cancer Treatment Combining Nanotechnology with Photo- and Radiotherapy

Colorectal cancer is the third most common cancer worldwide. Despite recent advances in the treatment of this pathology, which include a personalized approach using radio- and chemotherapies in combination with advanced surgical techniques, it is imperative to enhance the performance of these treatments and decrease their detrimental side effects on patients' health. Nanomedicine is likely the pathway towards solving this challenge by enhancing both the therapeutic and diagnostic capabilities. In particular, plasmonic nanoparticles show remarkable potential due to their dual therapeutic functionalities as photothermal therapy agents and as radiosensitizers in radiotherapy. Their dual functionality, high biocompatibility, easy functionalization, and targeting capabilities make them potential agents for inducing efficient cancer cell death with minimal side effects. This review aims to identify the main challenges in the diagnosis and treatment of colorectal cancer. The heterogeneous nature of this cancer is also discussed from a single-cell point of view. The most relevant works in photo- and radiotherapy using nanotechnology-based therapies for colorectal cancer are addressed, ranging from in vitro studies (2D and 3D cell cultures) to in vivo studies and clinical trials. Although the results using nanoparticles as a photo- and radiosensitizers in photo- and radiotherapy are promising, preliminary studies showed that the possibility of combining both therapies must be explored to improve the treatment efficiency.

Gold nanoplatform for near-infrared light-activated radio-photothermal gas therapy in breast cancer

Although radiotherapy is one of the most common treatments for triple-negative breast cancer (TNBC), it frequently has unsatisfactory therapeutic outcomes due to the radiation resistance of tumor tissues. Therefore, a synergistic strategy is urgently needed to increase therapeutic responses and prolong patient survival. Herein, we constructed gold nanocages (GNCs) loaded with a hyperpyrexia-sensitive nitric oxide (NO) donor (thiolate cupferron) to integrate extrinsic radiosensitization, local photothermal therapy, and near-infrared-activated NO gas therapy. The resulting nanoplatform (GNCs@NO) showed a high photothermal conversion efficiency, which induced the death of cancer cells and facilitated rapid NO release in tumor tissues. The radiosensitizing efficacy of GNCs@NO was further demonstrated in vitro and in vivo. Importantly, the released NO reacted with the reactive oxide species induced by radiotherapy to produce more toxic reactive nitrogen species, exerting a synergistic effect to improve anticancer efficacy. Thus, GNCs@NO demonstrated excellent effects as a combination therapy with few adverse effects. Our work proposes a promising nanoplatform for the radio/photothermal/gas treatment of TNBC.

Advances in the Mechanistic Understanding of Iron Oxide Nanoparticles' Radiosensitizing Properties

Among the plethora of nanosystems used in the field of theranostics, iron oxide nanoparticles (IONPs) occupy a central place because of their biocompatibility and magnetic properties. In this study, we highlight the radiosensitizing effect of two IONPs formulations (namely 7 nm carboxylated IONPs and PEG₅₀₀₀-IONPs) on A549 lung carcinoma cells when exposed to 225 kV X-rays after 6 h, 24 h and 48 h incubation. The hypothesis that nanoparticles exhibit their radiosensitizing effect by weakening cells through the inhibition of detoxification enzymes was evidenced by thioredoxin reductase activity monitoring. In particular, a good correlation between the amplification effect at 2 Gy and the residual activity of thioredoxin reductase was observed, which is consistent with previous observations made for gold nanoparticles (NPs). This emphasizes that NP-induced radiosensitization does not result solely from physical phenomena but also results from biological events.

Boron clusters (ferrabisdicarbollides) shaping the future as radiosensitizers for multimodal (chemo/radio/PBFR) therapy of glioblastoma

Glioblastoma multiforme (GBM) is the most common and fatal primary brain tumor, and is highly resistant to conventional radiotherapy and chemotherapy. Therefore, the development of multidrug resistance and tumor recurrence are frequent. Given the poor survival with the current treatments, new therapeutic strategies are urgently needed. Radiotherapy (RT) is a common cancer treatment modality for GBM. However, there is still a need to improve RT efficiency, while reducing the severe side effects. Radiosensitizers can enhance the killing effect on tumor cells with less side effects on healthy tissues. Herein, we present our pioneering study on the highly stable and amphiphilic metallacarboranes, ferrabis(dicarbollides) ([o-FESAN]^- and [8,8'-I2-o-FESAN]^-), as potential radiosensitizers for GBM radiotherapy. We propose radiation methodologies that utilize secondary radiation emissions from iodine and iron, using ferrabis(dicarbollides) as iodine/iron donors, aiming to achieve a greater therapeutic effect than that of a conventional radiotherapy. As a proof-of-concept, we show that using 2D and 3D models of U87 cells, the cellular viability and survival were reduced using this treatment approach. We also tested for the first time the proton boron fusion reaction (PBFR) with ferrabis(dicarbollides), taking advantage of their high boron (¹¹B) content. The results from the cellular damage response obtained suggest that proton boron fusion radiation therapy, when combined with boron-rich compounds, is a promising modality to fight against resistant tumors. Although these results are encouraging, more developments are needed to further explore ferrabis(dicarbollides) as radiosensitizers towards a positive impact on the therapeutic strategies for GBM.

Improve the cytotoxic effects of megavoltage radiation treatment by Fe3O4@Cus–PEG nanoparticles as a novel radiosensitizer in colorectal cancer cells

Background

To enhance the performance of radiotherapy, emerging nanoparticles that can professionally enhance X-ray irradiation to destruct cancer cells are extremely necessary. Here, we examined the potential of PEG-coated magnetite copper sulfide hetero-nanoparticles (Fe3O4@Cus–PEG) as a radiosensitizer agent.

Methods

Fe3O4@Cus–PEG nanoparticles were synthesized and characterized. The toxicity of nanoparticles on HT-29 colorectal cancer cells was assessed by the MTT assay. The radio-sensitizing effects of Fe3O4@Cus–PEG nanoparticles on HT-29 cancer cells were investigated by the MTT and colony formation assays. Moreover, the underlying mechanisms for Fe3O4@Cus–PEG nanoparticles to improve the radiation sensitivity of cells were evaluated.

Results

The results demonstrated that nanoparticles enhanced the effects of X-ray irradiation in a dose-dependent manner. The effects of combined treatments (nanoparticles and X-ray radiation) were strongly synergistic. The sensitizing enhancement ratio (SER) of nanoparticles was 2.02. Our in vitro assays demonstrated that the nitric oxide production, the intracellular hydrogen peroxide concentration, and the expression level of Bax and Caspase-3 genes significantly increased in the cells treated with the combination of nanoparticles and radiation. Whereas, the Glutathione peroxidase enzyme activity and the expression level of the Bcl-2 gene in the combined treatment significantly decreased compared to the radiation alone.

Conclusions

Our study suggests that Fe3O4@Cus–PEG nanoparticles are the promising nano radio-sensitizing agents for the treatment of cancer cells to enhance the efficacy of radiation therapy through increasing the reactive oxygen species generation, nitric oxide production, and inducing apoptosis.

Graphical Abstract

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.

Pancreatic tumor microenvironmental acidosis and hypoxia transform gold nanorods into cell-penetrant particles for potent radiosensitization

Coating nanoparticles with stealth epilayers increases circulation time by evading opsonization, macrophage phagocytosis, and reticuloendothelial sequestration. However, this also reduces internalization by cancer cells upon reaching the tumor. We designed gold nanorods (GNRs) with an epilayer that retains stealth properties in circulation but transforms spontaneously in the acidotic tumor microenvironment to a cell-penetrating particle. We used a customized stoichiometric ratio of l-glutamic acid and l-lysine within an amphiphilic polymer of poly(l-glutamic acid-co-l-lysine), or P(Glu-co-Lys), to effect this transformation in acidotic environments. P(Glu-co-Lys)-GNRs were internalized by cancer cells to facilitate potent in vitro radiosensitization. When administered intravenously in mice, they accumulate in the periphery and core of tumors without any signs of serum biochemical or hematological alterations, normal organ histopathological abnormalities, or overt deterioration in animal health. Furthermore, P(Glu-co-Lys)-GNRs penetrated the tumor microenvironment to accumulate in the hypoxic cores of tumors to potently radiosensitize heterotopic and orthotopic pancreatic cancers in vivo.

Impact of Sterilization on the Colloidal Stability of Ligand-Free Gold Nanoparticles for Biomedical Applications

Sterilization is a major prerequisite for the utilization of nanoparticle colloids in biomedicine, a process well examined for particles derived from chemical synthesis although highly underexplored for electrostatically stabilized ligand-free gold nanoparticles (AuNPs). Hence, in this work, we comprehensively examined and compared the physicochemical characteristics of laser-generated ligand-free colloidal AuNPs exposed to steam sterilization and sterile filtration as a function of particle size and mass concentration and obtained physicochemical insight into particle growth processes. These particles exhibit long-term colloidal stability (up to 3 months) derived from electrostatic stabilization without using any ligands or surfactants. We show that particle growth attributed to cluster-based ripening occurs in smaller AuNPs (∼5 nm) following autoclaving, while larger particles (∼10 and ∼30 nm) remain stable. Sterile filtration, as an alternative effective sterilizing approach, has no substantial impact on the colloidal stability of AuNPs, regardless of particle size, although a mass loss of 5-10% is observed. Finally, we evaluated the impact of the sterilization procedures on potential particle functionality in proton therapy, using the formation of reactive oxygen species (ROS) as a readout. In particular, 5 nm AuNPs exhibit a significant loss in activity upon autoclaving, probably dedicated to specific surface area reduction and surface restructuring during particle growth. The filtered analog enhanced the ROS release by up to a factor of ∼2.0, at 30 ppm gold concentration. Our findings highlight the need for carefully adapting the sterilization procedure of ligand-free NPs to the desired biomedical application with special emphasis on particle size and concentration.

Biological Response of Human Cancer Cells to Ionizing Radiation in Combination with Gold Nanoparticles

Simple Summary

Various types of metallic nanoparticles and especially gold nanoparticles (AuNPs) have been utilized in radiation studies to enhance the radiosensitization of cancer cells while minimizing detrimental effects in normal tissue. The aim of our study was to investigate the biological responses of various human cancer cells to gold-nanoparticle-induced radiosensitization. This was accomplished by using different AuNPs and several techniques in order to provide valuable insights regarding the multiple adverse biological effects, following ionizing radiation (IR) in combination with AuNPs. Insightful methodologies such as transmission electron microscopy were employed to identify comprehensively the complexity of the biological damage occurrence. Our findings confirm that AuNP radiosensitization may occur due to extensive and/or complex DNA damage, cell death, or cellular senescence. This multiparameter study aims to further elucidate the biological mechanisms and at the same time provide new information regarding the use of AuNPs as radiosensitizers in cancer treatment.

Abstract

In the context of improving radiation therapy, high-atomic number (Z) metallic nanoparticles and, more importantly, gold-based nanostructures are developed as radiation enhancers/radiosensitizers. Due to the diversity of cell lines, nanoparticles, as well as radiation types or doses, the resulting biological effects may differ and remain obscure. In this multiparameter study, we aim to shed light on these effects and investigate them further by employing X-irradiation and three human cancer cell lines (PC3, A549, and U2OS cells) treated by multiple techniques. TEM experiments on PC3 cells showed that citrate-capped AuNPs were found to be located mostly in membranous structures/vesicles or autophagosomes, but also, in the case of PEG-capped AuNPs, inside the nucleus as well. The colony-forming capability of cancer cells radiosensitized by AuNPs decreased significantly and the DNA damage detected by cytogenetics, γH2AX immunostaining, and by single (γH2AX) or double (γH2AX and OGG1) immunolocalization via transmission electron microscopy (TEM) was in many cases higher and/or persistent after combination with AuNPs than upon individual exposure to ionizing radiation (IR). Moreover, different cell cycle distribution was evident in PC3 but not A549 cells after treatment with AuNPs and/or irradiation. Finally, cellular senescence was investigated by using a newly established staining procedure for lipofuscin, based on a Sudan Black-B analogue (GL13) which showed that based on the AuNPs’ concentration, an increased number of senescent cells might be observed after exposure to IR. Even though different cell lines or different types and concentrations of AuNPs may alter the levels of radiosensitization, our results imply that the complexity of damage might also be an important factor of AuNP-induced radiosensitization.

Nanotherapeutic treatment of the invasive glioblastoma tumor microenvironment

Glioblastoma (GBM) is the most common malignant adult brain cancer with no curative treatment strategy. A significant hurdle in GBM treatment is effective therapeutic delivery to the brain-invading tumor cells that remain following surgery within functioning brain regions. Developing therapies that can either directly target these brain-invading tumor cells or act on other cell types and molecular processes supporting tumor cell invasion and recurrence are essential steps in advancing new treatments in the clinic. This review highlights some of the drug delivery strategies and nanotherapeutic technologies that are designed to target brain-invading GBM cells or non-neoplastic, invasion-supporting cells residing within the GBM tumor microenvironment.

Differential Radiosensitizing Effect of 50 nm Gold Nanoparticles in Two Cancer Cell Lines

Simple Summary

Nanoparticle treatment on tumor cells is proposed for its potential radiosensitizing properties, increasing the radiation effect on tumor cells and reducing the adverse effects on healthy tissues. The present study evaluates, on two cell lines derived from colon and breast adenocarcinomas, the impact of irradiation in the presence of specifically targeted gold nanoparticles. Cells were irradiated in the absence and in the presence of non-functionalized or specifically functionalized gold nanoparticles. The results pointed out that actively targeting gold nanoparticles has a clear radiosensitizing effect in both cell lines.

Abstract

Radiation therapy is widely used as an anti-neoplastic treatment despite the adverse effects it can cause in non-tumoral tissues. Radiosensitizing agents, which can increase the effect of radiation in tumor cells, such as gold nanoparticles (GNPs), have been described. To evaluate the radiosensitizing effect of 50 nm GNPs, we carried out a series of studies in two neoplastic cell lines, Caco2 (colon adenocarcinoma) and SKBR3 (breast adenocarcinoma), qualitatively evaluating the internalization of the particles, determining with immunofluorescence the number of γ-H2AX foci after irradiation with ionizing radiation (3 Gy) and evaluating the viability rate of both cell lines after treatment by means of an MTT assay. Nanoparticle internalization varied between cell lines, though they both showed higher internalization degrees for functionalized GNPs. The γ-H2AX foci counts for the different times analyzed showed remarkable differences between cell lines, although they were always significantly higher for functionalized GNPs in both lines. Regarding cell viability, in most cases a statistically significant decreasing tendency was observed when treated with GNPs, especially those that were functionalized. Our results led us to conclude that, while 50 nm GNPs induce a clear radiosensitizing effect, it is highly difficult to describe the magnitude of this effect as universal because of the heterogeneity found between cell lines.

Intercomparison of radiosensitization induced by gold and iron oxide nanoparticles in human glioblastoma cells irradiated by 6 MV photons

In this work, an intercomparison of sensitization effects produced by gold (GNP) and dextran-coated iron oxide (SPION-DX) nanoparticles in M059J and U87 human glioblastoma cells was performed using 6 MV-photons. Three variables were mapped: the nanoparticle material, treatment concentration, and cell radiosensitivity. For U87, GNP treatments resulted in high sensitization enhancement ratios (SER\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{10\%}$$\end{document}10% up to 2.04). More modest effects were induced by SPION-DX, but still significant reductions in survival were achieved (maximum SER\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{10\%}=1.61$$\end{document}10%=1.61 ). For the radiosensitive M059J, sensitization by both NPs was poor. SER\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{10\%}$$\end{document}10% increased with the degree of elemental uptake in the cells, but not necessarily with treatment concentration. For GNP, where exposure concentration and elemental uptake were found to be proportional, SER\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{10\%}$$\end{document}10% increased linearly with concentration in both cell lines. For SPION-DX, saturation of sensitization enhancement and metal uptake occurred at high exposures. Fold change in the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha /\beta$$\end{document}α/β ratios extracted from survival curves are reduced by the presence of SPION-DX but strongly increased by GNPs , suggesting that sensitization by GNPs occurs mainly via promotion of lethal damage, while for SPION-DX repairable damage dominates. The NPs were more effective in eliminating the radioresistant glioblastoma cells, an interesting finding, as resistant cells are key targets to improve treatment outcome.

Dose Rate Effects on the Selective Radiosensitization of Prostate Cells by GRPR-Targeted Gold Nanoparticles

For a while, gold nanoparticles (AuNPs) have been recognized as potential radiosensitizers in cancer radiation therapy, mainly due to their physical properties, making them appealing for medical applications. Nevertheless, the performance of AuNPs as radiosensitizers still raises important questions that need further investigation. Searching for selective prostate (PCa) radiosensitizing agents, we studied the radiosensitization capability of the target-specific AuNP-BBN in cancer versus non-cancerous prostate cells, including the evaluation of dose rate effects in comparison with non-targeted counterparts (AuNP-TDOTA). PCa cells were found to exhibit increased AuNP uptake when compared to non-tumoral ones, leading to a significant loss of cellular proliferation ability and complex DNA damage, evidenced by the occurrence of multiple micronucleus per binucleated cell, in the case of PC3 cells irradiated with 2 Gy of γ-rays, after incubation with AuNP-BBN. Remarkably, the treatment of the PC3 cells with AuNP-BBN led to a much stronger influence of the dose rate on the cellular survival upon γ-photon irradiation, as well as on their genomic instability. Overall, AuNP-BBN emerged in this study as a very promising nanotool for the efficient and selective radiosensitization of human prostate cancer PC3 cells, therefore deserving further preclinical evaluation in adequate animal models for prostate cancer radiotherapy.

Nanomaterials in cancer: Reviewing the combination of hyperthermia and triggered chemotherapy

Nanoparticle mediated hyperthermia has been explored as a method to increase cancer treatment efficacy by heating tumours inside-out. With that purpose, nanoparticles have been designed and their properties tailored to respond to external stimuli and convert the supplied energy into heat, therefore inducing damage to tumour cells. Moreover, the combination of hyperthermia with chemotherapy has been described as a more effective strategy due to the synergy between the high temperature and the drug's effects, also associated with a remote controlled and on-demand drug release. In this review, the methods behind nanoparticle mediated hyperthermia, namely material design, external stimuli response and energy conversion will be discussed and critically analysed. We will address the most relevant studies on hyperthermia and temperature triggered drug release for cancer treatment. Finally, the advantages, difficulties and challenges of this therapeutic strategy will be discussed, while giving insight for future developments.

Hydrothermal Synthesis of β-Nb2ZnO6 Nanoparticles for Photocatalytic Degradation of Methyl Orange and Cytotoxicity Study

β-Nb₂ZnO₆ nanoparticles were synthesized by a hydrothermal process and calcined at two temperatures, 500 °C and 700 °C, and assigned as A and B, respectively. X-ray diffraction, together with transmission electron microscopy, revealed that the β-Nb₂ZnO₆ nanoparticles calcined at 700 °C (B) were more crystalline than the β-Nb₂ZnO₆ calcined at 500 °C (A) with both types of nanoparticles having an average size of approximately 100 nm. The physiochemical, photocatalytic, and cytotoxic activities of both types of β-Nb₂ZnO₆ nanoparticles (A and B) were examined. Interestingly, the photodegradation of methyl orange, used as a standard for environmental pollutants, was faster in the presence of the β-Nb₂ZnO₆ nanoparticles calcined at 500 °C (A) than in the presence of those calcined at 700 °C (B). Moreover, the cytotoxicity was evaluated against different types of cancer cells and the results indicated that both types of β-Nb₂ZnO₆ nanoparticles (A and B) exhibited high cytotoxicity against MCF-7 and HCT116 cells but low cytotoxicity against HeLa cells after 24 and 48 h of treatment. Overall, both products expressed similar EC₅₀ values on tested cell lines and high cytotoxicity after 72 h of treatment. As a photocatalyst, β-Nb₂ZnO₆ nanoparticles (A) could be utilized in different applications including the purification of the environment and water from specific pollutants. Further biological studies are required to determine the other potential impacts of utilizing β-Nb₂ZnO₆ nanoparticles in the biomedical application field.

Mass Cytometry Exploration of Immunomodulatory Responses of Human Immune Cells Exposed to Silver Nanoparticles

Increasing production and application of silver nanoparticles (Ag NPs) have raised concerns on their possible adverse effects on human health. However, a comprehensive understanding of their effects on biological systems, especially immunomodulatory responses involving various immune cell types and biomolecules (e.g., cytokines and chemokines), is still incomplete. In this study, a single-cell-based, high-dimensional mass cytometry approach is used to investigate the immunomodulatory responses of Ag NPs using human peripheral blood mononuclear cells (hPBMCs) exposed to poly-vinyl-pyrrolidone (PVP)-coated Ag NPs of different core sizes (i.e., 10-, 20-, and 40-nm). Although there were no severe cytotoxic effects observed, ^PVPAg¹⁰ and ^PVPAg²⁰ were excessively found in monocytes and dendritic cells, while ^PVPAg⁴⁰ displayed more affinity with B cells and natural killer cells, thereby triggering the release of proinflammatory cytokines such as IL-2, IL-17A, IL-17F, MIP1β, TNFα, and IFNγ. Our findings indicate that under the exposure conditions tested in this study, Ag NPs only triggered the inflammatory responses in a size-dependent manner rather than induce cytotoxicity in hPBMCs. Our study provides an appropriate ex vivo model to better understand the human immune responses against Ag NP at a single-cell level, which can contribute to the development of targeted drug delivery, vaccine developments, and cancer radiotherapy treatments.

NVCL-Based Galacto-Functionalized and Thermosensitive Nanogels with GNRDs for Chemo/Photothermal-Therapy

Dual-function nanogels (particle size from 98 to 224 nm) synthesized via surfactant-free emulsion polymerization (SFEP) were tested as smart carriers toward synergistic chemo- and photothermal therapy. Cisplatin (CDDP) or doxorubicin (DOX) and gold nanorods (GNRDs) were loaded into galacto-functionalized PNVCL-based nanogels, where the encapsulation efficiency for CDDP and DOX was around 64 and 52%, respectively. PNVCL-based nanogels were proven to be an efficient delivery vehicle under conditions that mimic the tumor site in vitro. The release of CDDP or DOX was slower at pH 7.4 and 37 °C than at tumor conditions of pH 6 and 40 °C. On the other hand, in the systems with GNRDs at pH 7.4 and 37 °C, the sample was irradiated with a 785 nm laser for 10 min every hour, obtaining that the release profiles were even higher than in the conditions that simulated a cancer tissue (without irradiation). Thus, the present study demonstrates the synergistic effect of chemo- and photothermal therapy as a promising dual function in the potential future use of PNVCL nanogels loaded with GNRDs and CDDP/DOX to achieve an enhanced chemo/phototherapy in vivo.