Gadolinium-based nanoparticles for theranostic MRI-radiosensitization

Gd-GQDs as nanotheranostic platform for the treatment of HPV-positive oropharyngeal cancer

In this study, we developed new gadolinium-graphene quantum dot nanoparticles (Gd-GQDs) as a theranostic platform for magnetic resonance imaging and improved the efficiency of radiotherapy in HPV-positive oropharyngeal cancer. Based on cell toxicity results, Gd-GQD NPs were nontoxic for both cancer and normal cell lines up to 25 µg/ml. These NPs enhance the cytotoxic effect of radiation only on cancer cells but not on normal cells. The flow cytometry analysis indicated that cell death mainly occurred in the late phase of apoptosis. The immunocytochemical analysis was used to evaluate apoptosis pathway proteins. The Bcl-2 and p53 protein levels did not differ statistically significantly between radiation alone group and those that received irradiation in combination with NPs. In contrast, the combination group exhibited a significant increase in Bax protein expression, suggesting that cells could undergo apoptosis independent of the p53 pathway. Magnetic resonance (MR) imaging showed that Gd-GQD NPs, when used at low concentrations, enhanced T1-weighted signal intensity resulting from T1 shortening effects. At higher concentrations, the T2 shortening effect became predominant and was able to decrease the signal intensity. Gd-GQD appears to offer a novel approach for enhancing the effectiveness of radiation treatment and facilitating MR imaging for monitoring HPV-positive tumors.

Preparation and Characterization of Zinc Ferrite and Gadolinium Iron Garnet Composite for Biomagnetic Applications

Cancer is a major worldwide public health problem. Although there have already been astonishing advances in cancer diagnosis and treatment, the scientific community continues to make huge efforts to develop new methods to treat cancer. The main objective of this work is to prepare, using a green sol-gel method with coconut water powder (CWP), a new nanocomposite with a mixture of Gd3Fe5O12 and ZnFe2O4, which has never been synthesized previously. Therefore, we carried out a structural (DTA-TG and X-ray diffraction), morphological (SEM), and magnetic (VSM and hyperthermia) characterization of the prepared samples. The prepared nanocomposite denoted a saturation magnetization of 11.56 emu/g at room temperature with a ferromagnetic behavior and with a specific absorption rate (SAR) value of 0.5 ± 0.2 (W/g). Regarding cytotoxicity, for concentrations < 10 mg/mL, it does not appear to be toxic. Although the obtained results were interesting, the high particle size was identified as a problem for the use of this nanocomposite.

In Vitro and In Vivo Synergetic Radiotherapy with Gold Nanoparticles and Docetaxel for Pancreatic Cancer

This research underscores the potential of combining nanotechnology with conventional therapies in cancer treatment, particularly for challenging cases like pancreatic cancer. We aimed to enhance pancreatic cancer treatment by investigating the synergistic effects of gold nanoparticles (GNPs) and docetaxel (DTX) as potential radiosensitizers in radiotherapy (RT) both in vitro and in vivo, utilizing a MIA PaCa-2 monoculture spheroid model and NRG mice subcutaneously implanted with MIA PaCa-2 cells, respectively. Spheroids were treated with GNPs (7.5 μg/mL), DTX (100 nM), and 2 Gy of RT using a 6 MV linear accelerator. In parallel, mice received treatments of GNPs (2 mg/kg), DTX (6 mg/kg), and 5 Gy of RT (6 MV linear accelerator). In vitro results showed that though RT and DTX reduced spheroid size and increased DNA DSBs, the triple combination of DTX/RT/GNPs led to a significant 48% (p = 0.05) decrease in spheroid size and a 45% (p = 0.05) increase in DNA DSBs. In vivo results showed a 20% (p = 0.05) reduction in tumor growth 20 days post-treatment with (GNPs/RT/DTX) and an increase in mice median survival. The triple combination exhibited a synergistic effect, enhancing anticancer efficacy beyond individual treatments, and thus could be employed to improve radiotherapy and potentially reduce adverse effects.

AGuIX nanoparticle-nanobody bioconjugates to target immune checkpoint receptors

This article presents bioconjugates combining nanoparticles (AGuIX) with nanobodies (VHH) targeting Programmed Death-Ligand 1 (PD-L1, A12 VHH) and Cluster of Differentiation 47 (CD47, A4 VHH) for active tumor targeting. AGuIX nanoparticles offer theranostic capabilities and an efficient biodistribution/pharmacokinetic profile (BD/PK), while VHH's reduced size (15 kDa) allows efficient tumor penetration. Site-selective sortagging and click chemistry were compared for bioconjugation. While both methods yielded bioconjugates with similar functionality, click chemistry demonstrated higher yield and could be used for the conjugation of various VHH. The specific targeting of AGuIX@VHH has been demonstrated in both in vitro and ex vivo settings, paving the way for combined targeted immunotherapies, radiotherapy, and cancer imaging.

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.

Multifunctional nanoprobe for multi-mode imaging and diagnosis of metastatic prostate cancer

The high incidence and complex subtypes of prostate cancer put forward higher requirements for accurate diagnosis. Furthermore, advanced prostate cancer is prone to metastasis. Single biological imaging mode faces a challenge of sensitive and fast bioimaging of metastasic prostate cancer. Thus, exploring a nanoprobe with multi-mode imaging function has an important impact on preoperative imaging and intraoperative visualization guide of metastatic prostate cancer. Herein, based on the optical properties and X-ray attenuation capability of Au nanodots as well as the slow electronic relaxation of Gd³⁺, we designed and fabricated the multifunctional nanoprobe Au/Gd nanodots for multi-mode imaging and accurate diagnosis of bone metastatic prostate cancer. The results showed that multiple imaging modes complement each other to achieve high-precision of metastasic prostate cancer detection and accurately guide treatment. In addition, in vitro/vivo experiments showed that Au/Gd nanodots had good biocompatibility and biosafety. Therefore, the prepared multifunctional nanoprobe may provide new strategies and insights for precise diagnosis of metastatic prostate cancer in clinical practice.

Dual-Peak Lorentzian CEST MRI for antiretroviral drug brain distribution

Objectives

Spatial-temporal biodistribution of antiretroviral drugs (ARVs) can now be achieved using MRI by utilizing chemical exchange saturation transfer (CEST) contrasts. However, the presence of biomolecules in tissue limits the specificity of current CEST methods. To overcome this limitation, a Lorentzian line-shape fitting algorithm was developed that simultaneously fits CEST peaks of ARV protons on its Z-spectrum.

Case presentation

This algorithm was tested on the common first line ARV, lamivudine (3TC), that has two peaks resulting from amino (-NH2) and hydroxyl (-OH) protons in 3TC. The developed dual-peak Lorentzian function fitted these two peaks simultaneously, and used the ratio of -NH2 and -OH CEST contrasts as a constraint parameter to measure 3TC presence in brains of drug-treated mice. 3TC biodistribution calculated using the new algorithm was compared against actual drug levels measured using UPLC-MS/MS. In comparison to the method that employs the -NH2 CEST peak only, the dual-peak Lorentzian fitting algorithm showed stronger correlation with brain tissue 3TC levels, signifying estimation of actual drug levels.

Conclusions

We concluded that 3TC levels can be extracted from confounding CEST effects of tissue biomolecules resulting in improved specificity for drug mapping. This algorithm can be expanded to measure a variety of ARVs using CEST MRI.

Vaccine-like nanomedicine for cancer immunotherapy

The successful clinical application of immune checkpoint blockade (ICB) and chimeric antigen receptor T cells (CAR-T) therapeutics has attracted extensive attention to immunotherapy, however, their drawbacks such as limited specificity, persistence and toxicity haven't met the high expectations on efficient cancer treatments. Therapeutic cancer vaccines which instruct the immune system to capture tumor specific antigens, generate long-term immune memory and specifically eliminate cancer cells gradually become the most promising strategies to eradicate tumor. However, the disadvantages of some existing vaccines such as weak immunogenicity and in vivo instability have restricted their development. Nanotechnology has been recently incorporated into vaccine fabrication and exhibited promising results for cancer immunotherapy. Nanoparticles promote the stability of vaccines, as well as enhance antigen recognition and presentation owing to their nanometer size which promotes internalization of antigens by phagocytic cells. The surface modification with targeting units further permits the delivery of vaccines to specific cells. Meanwhile, nanocarriers with adjuvant effect can improve the efficacy of vaccines. In addition to classic vaccines composed of antigens and adjuvants, the nanoparticle-mediated chemotherapy, radiotherapy and certain other therapeutics could induce the release of tumor antigens in situ, which therefore effectively simulate antitumor immune responses. Such vaccine-like nanomedicine not only kills primary tumors, but also prevents tumor recurrence and helps eliminate metastatic tumors. Herein, we introduce recent developments in nanoparticle-based delivery systems for antigen delivery and in situ antitumor vaccination. We will also discuss the remaining opportunities and challenges of nanovaccine in clinical translation towards cancer treatment.

Recent Advances in Functionalized Nanoparticles in Cancer Theranostics

Cancer theranostics is the combination of diagnosis and therapeutic approaches for cancer, which is essential in personalized cancer treatment. The aims of the theranostics application of nanoparticles in cancer detection and therapy are to reduce delays in treatment and hence improve patient care. Recently, it has been found that the functionalization of nanoparticles can improve the efficiency, performance, specificity and sensitivity of the structure, and increase stability in the body and acidic environment. Moreover, functionalized nanoparticles have been found to possess a remarkable theranostic ability and have revolutionized cancer treatment. Each cancer treatment modality, such as MRI-guided gene therapy, MRI-guided thermal therapy, magnetic hyperthermia treatment, MRI-guided chemotherapy, immunotherapy, photothermal and photodynamic therapy, has its strengths and weaknesses, and combining modalities allows for a better platform for improved cancer control. This is why cancer theranostics have been investigated thoroughly in recent years and enabled by functionalized nanoparticles. In this topical review, we look at the recent advances in cancer theranostics using functionalized nanoparticles. Through understanding and updating the development of nanoparticle-based cancer theranostics, we find out the future challenges and perspectives in this novel type of cancer treatment.

Using ELP Repeats as a Scaffold for De Novo Construction of Gadolinium-Binding Domains within Multifunctional Recombinant Proteins for Targeted Delivery of Gadolinium to Tumour Cells

Three artificial proteins that bind the gadolinium ion (Gd3+) with tumour-specific ligands were de novo engineered and tested as candidate drugs for binary radiotherapy (BRT) and contrast agents for magnetic resonance imaging (MRI). Gd3+-binding modules were derived from calmodulin. They were joined with elastin-like polypeptide (ELP) repeats from human elastin to form the four-centre Gd3+-binding domain (4MBS-domain) that further was combined with F3 peptide (a ligand of nucleolin, a tumour marker) to form the F3-W4 block. The F3-W4 block was taken alone (E2-13W4 protein), as two repeats (E1-W8) and as three repeats (E1-W12). Each protein was supplemented with three copies of the RGD motif (a ligand of integrin αvβ3) and green fluorescent protein (GFP). In contrast to Magnevist (a Gd-containing contrast agent), the proteins exhibited three to four times higher accumulation in U87MG glioma and A375 melanoma cell lines than in normal fibroblasts. The proteins remained for >24 h in tumours induced by Ca755 adenocarcinoma in C57BL/6 mice. They exhibited stability towards blood proteases and only accumulated in the liver and kidney. The technological advantages of using the engineered proteins as a basis for developing efficient and non-toxic agents for early diagnosis of tumours by MRI as well as part of BRT were demonstrated.

Advances in Nanoliposomes for the Diagnosis and Treatment of Liver Cancer

The mortality rate of liver cancer is gradually increasing worldwide due to the increasing risk factors such as fatty liver, diabetes, and alcoholic cirrhosis. The diagnostic methods of liver cancer include ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI), among others. The treatment of liver cancer includes surgical resection, transplantation, ablation, and chemoembolization; however, treatment still faces multiple challenges due to its insidious development, high rate of recurrence after surgical resection, and high failure rate of transplantation. The emergence of liposomes has provided new insights into the treatment of liver cancer. Due to their excellent carrier properties and maneuverability, liposomes can be used to perform a variety of functions such as aiding in imaging diagnoses, combinatorial therapies, and integrating disease diagnosis and treatment. In this paper, we further discuss such advantages.

Microdosimetric Investigation and a Novel Model of Radiosensitization in the Presence of Metallic Nanoparticles

Auger cascades generated in high atomic number nanoparticles (NPs) following ionization were considered a potential mechanism for NP radiosensitization. In this work, we investigated the microdosimetric consequences of the Auger cascades using the theory of dual radiation action (TDRA), and we propose the novel Bomb model as a general framework for describing NP-related radiosensitization. When triggered by an ionization event, the Bomb model considers the NPs that are close to a radiation sensitive cellular target, generates dense secondary electrons and kills the cells according to a probability distribution, acting like a “bomb.” TDRA plus a distance model were used as the theoretical basis for calculating the change in α of the linear-quadratic survival model and the relative biological effectiveness (RBE). We calculated these quantities for SQ20B and Hela human cancer cells under 250 kVp X-ray irradiation with the presence of gadolinium-based NPs (AGuIX^TM), and 220 kVp X-ray irradiation with the presence of 50 nm gold NPs (AuNPs), respectively, and compared with existing experimental data. Geant4-based Monte Carlo (MC) simulations were used to (1) generate the electron spectrum and the phase space data of photons entering the NPs and (2) calculate the proximity functions and other related parameters for the TDRA and the Bomb model. The Auger cascade electrons had a greater proximity function than photoelectric and Compton electrons in water by up to 30%, but the resulting increases in α were smaller than those derived from experimental data. The calculated RBEs cannot explain the experimental findings. The relative increase in α predicted by TDRA was lower than the experimental result by a factor of at least 45 for SQ20B cells with AGuIX under 250 kVp X-ray irradiation, and at least four for Hela cells with AuNPs under 220 kVp X-ray irradiation. The application of the Bomb model to Hela cells with AuNPs under 220 kVp X-ray irradiation indicated that a single ionization event for NPs caused by higher energy photons has a higher probability of killing a cell. NPs that are closer to the cell nucleus are more effective for radiosensitization. Microdosimetric calculations of the RBE for cell death of the Auger electron cascade cannot explain the experimentally observed radiosensitization by AGuIX or AuNP, while the proposed Bomb model is a potential candidate for describing NP-related radiosensitization at low NP concentrations.

Re-engineering a Liposome with Membranes of Red Blood Cells for Drug Delivery and Diagnostic Applications

Red blood cells (RBCs) make up the overwhelming majority of cells in the vascular system, spending most of their lives wandering the vast network of vessels that permeate every tissue of our bodies. Therefore, the delivery of any class of therapeutic agent that must stay in the circulatory system may benefit from being carried by RBCs. Toward this direction, we have re-engineered a synthetic liposome with the membranes of RBCs and incorporated a magnetic resonance imaging (MRI) contrast agent gadolinium along with the chemotherapeutic drug doxorubicin (DOX) to form a biomimetic liposome (BML). The BMLs proposed herein consist of biocompatible/biodegradable synthetic phospholipids, which include 1,2-distearoyl-sn-glycero-3-phosphoglycerol, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine, and gadolinium-conjugated lipids. These synthetic phospholipids have been fused with a natural RBC membrane and are loaded with DOX using the extrusion technique. BMLs were characterized for their physicochemical properties, stability, fusogenic (between synthetic and natural lipid from RBC), magnetic, drug loading, biocompatibility, and cytotoxicity properties. BMLs had a hydrodynamic diameter of 180 ± 20 nm with a negative surface charge of 29 ± 2 mV. The longitudinal relaxivity (r₁) of BML is 3.71 mM^-1 s^-1, which is comparable to the r₁ of commercial contrast agent, Magnevist. In addition, DOX-loaded BML showed a cytotoxicity pattern similar to that of free DOX. These results showed the potential of using the proposed BML system for both MRI-based diagnostic applications and drug delivery platforms.

Metal peroxides for cancer treatment

In recent years, metal peroxide (MO2) such as CaO2 has received more and more attention in cancer treatment. MO2 is readily decompose to release metal ions and hydrogen peroxide in the acidic tumor microenvironment (TME), resulting metal ions overloading, decreased acidity and elevated oxidative stress in TME. All of these changes making MO2 an excellent tumor therapeutic agent. Moreover, by combining MO2 with photosensitizers, enzymes or Fenton reagents, MO2 can assist and promote various tumor therapies such as photodynamic therapy and chemodynamic therapy. In this review, the synthesis and modification methods of MO2 are introduced, and the representative studies of MO2-based tumor monotherapy and combination therapy are discussed in detail. Finally, the current challenges and prospects of MO2 in the field of tumor therapy are emphasized to promote the development of MO2-based cancer treatment.

Chemical exchange saturation transfer for detection of antiretroviral drugs in brain tissue

OBJECTIVE

Antiretroviral drug theranostics facilitates the monitoring of biodistribution and efficacy of therapies designed to target HIV type-1 (HIV-1) reservoirs. To this end, we have now deployed intrinsic drug chemical exchange saturation transfer (CEST) contrasts to detect antiretroviral drugs within the central nervous system (CNS).

DESIGN AND METHODS

CEST effects for lamivudine (3TC) and emtricitabine (FTC) were measured by asymmetric magnetization transfer ratio analyses. The biodistribution of 3TC in different brain sub-regions of C57BL/6 mice treated with lipopolysaccharides was determined using MRI. CEST effects of 3TC protons were quantitated by Lorentzian fitting analysis. 3TC levels in plasma and brain regions were measured using ultraperformance liquid chromatography tandem mass spectrometry to affirm the CEST test results.

RESULTS

CEST effects of the hydroxyl and amino protons in 3TC and FTC linearly correlated to drug concentrations. 3TC was successfully detected in vivo in brain sub-regions by MRI. The imaging results were validated by measurements of CNS drug concentrations.

CONCLUSION

CEST contrasts can be used to detect antiretroviral drugs using MRI. Such detection can be used to assess spatial--temporal drug biodistribution. This is most notable within the CNS where drug biodistribution may be more limited with the final goal of better understanding antiretroviral drug-associated efficacy and potential toxicity.

Stability of MRI contrast agents in high-energy radiation of a 1.5T MR-Linac

BACKGROUND

Gadolinium-based contrast is often used when acquiring MR images for radiation therapy planning for better target delineation. In some situations, patients may still have residual MRI contrast agents in their tissue while being treated with high-energy radiation. This is especially true when MRI contrast agents are administered during adaptive treatment replanning for patients treated on MR-Linac systems.

PURPOSE

The purpose of this study was to analyze the molecular stability of MRI contrast agents when exposed to high energy photons and the associated secondary electrons in a 1.5T MR-Linac system. This was the first step in assessing the safety of administering MRI contrast agents throughout the course of treatment.

MATERIALS AND METHODS

Two common MRI contrast agents were irradiated with 7 MV photons to clinical dose levels. The irradiated samples were analyzed using liquid chromatography-high resolution mass spectrometry to detect degradation products or conformational alterations created by irradiation with high energy photons and associated secondary electrons.

RESULTS

No significant change in chemical composition or displacement of gadolinium ions from their chelates was discovered in samples irradiated with 7 MV photons at relevant clinical doses in a 1.5T MR-Linac. Additionally, no significant correlation between concentrations of irradiated MRI contrast agents and radiation dose was observed.

CONCLUSION

The chemical composition stability of the irradiated contrast agents is promising for future use throughout the course of patient treatment. However, in vivo studies are needed to confirm that unexpected metabolites are not created in biological milieus.

Impact of superparamagnetic iron oxide nanoparticles on in vitro and in vivo radiosensitisation of cancer cells

PURPOSE

The recent implementation of MR-Linacs has highlighted theranostic opportunities of contrast agents in both imaging and radiotherapy. There is a lack of data exploring the potential of superparamagnetic iron oxide nanoparticles (SPIONs) as radiosensitisers. Through preclinical 225 kVp exposures, this study aimed to characterise the uptake and radiobiological effects of SPIONs in tumour cell models in vitro and to provide proof-of-principle application in a xenograft tumour model.

METHODS

SPIONs were also characterised to determine their hydrodynamic radius using dynamic light scattering and uptake was measured using ICP-MS in 6 cancer cell lines; H460, MiaPaCa2, DU145, MCF7, U87 and HEPG2. The impact of SPIONs on radiobiological response was determined by measuring DNA damage using 53BP1 immunofluorescence and cell survival. Sensitisation Enhancement Ratios (SERs) were compared with the predicted Dose Enhancement Ratios (DEFs) based on physical absorption estimations. In vivo efficacy was demonstrated using a subcutaneous H460 xenograft tumour model in SCID mice by following intra-tumoural injection of SPIONs.

RESULTS

The hydrodynamic radius was found to be between 110 and 130 nm, with evidence of being monodisperse in nature. SPIONs significantly increased DNA damage in all cell lines with the exception of U87 cells at a dose of 1 Gy, 1 h post-irradiation. Levels of DNA damage correlated with the cell survival, in which all cell lines except U87 cells showed an increased sensitivity (P < 0.05) in the linear quadratic curve fit for 1 h exposure to 23.5 μg/ml SPIONs. There was also a 30.1% increase in the number of DNA damage foci found for HEPG2 cells at 2 Gy. No strong correlation was found between SPION uptake and DNA damage at any dose, yet the biological consequences of SPIONs on radiosensitisation were found to be much greater, with SERs up to 1.28 ± 0.03, compared with predicted physical dose enhancement levels of 1.0001. In vivo, intra-tumoural injection of SPIONs combined with radiation showed significant tumour growth delay compared to animals treated with radiation or SPIONs alone (P < 0.05).

CONCLUSIONS

SPIONs showed radiosensitising effects in 5 out of 6 cancer cell lines. No correlation was found between the cell-specific uptake of SPIONs into the cells and DNA damage levels. The in vivo study found a significant decrease in the tumour growth rate.

Monte Carlo study of dosimetric impact of gadolinium contrast medium in transverse field MR-Linac system

The aim of this study is to evaluate the dosimetric impact of gadolinium contrast medium (Gadovist) in a transverse MR-Linac system using Monte Carlo methods. The dose distributions were calculated using two heterogeneous multi-layer phantoms consisting of Gadovist, water, bone, and lung. The photon beam was irradiated with a filed size of 5 × 5 cm², and a transverse magnetic field of 0-3.0 T was applied perpendicular to the incident photon beam. Next, dose distributions for brain, head and neck (H&N), and lung cancer patients were calculated using a patient voxel-based phantom with and without replacing the patient's GTV with Gadovist. The dose at the water-Gadovist interface increased by 8% without a magnetic field. A similar dose increment was observed at 0.35 T. In contrast, the dose increment at the water-Gadovist interface was small at 1.5 T and a dose decrement of 5% was observed at 3.0 T. The dose variation at the lung-Gadovist interface was larger than that at the water-Gadovist interface. The mass collision stopping power ratio for Gadovist was 7% lower than that for water, whereas, the electron fluence spectra at the water-Gadovist interface increased by 17.5%. In a patient study, Gadovist increased the D_mean for brain, H&N, and lung cancer patients by 0.65-8.9%. The dose variation due to Gadovist grew large in the low-dose region in H&N and lung cancer. The GTV dose variation due to Gadovist in all treatment site was below 2% at 0-3 T if the Gadovist concentration was lower than 0.2 mmol/ml^-1.

Multifunctional theranostic nanoparticles for biomedical cancer treatments - A comprehensive review

Modern-day search for the novel agents (their preparation and consequent implementation) to effectively treat the cancer is mainly fuelled by the historical failure of the conventional treatment modalities. Apart from that, the complexities such as higher rate of cell mutations, variable tumor microenvironment, patient-specific disparities, and the evolving nature of cancers have made this search much stronger in the latest times. As a result of this, in about two decades, the theranostic nanoparticles (TNPs) - i.e., nanoparticles that integrate therapeutic and diagnostic characteristics - have been developed. The examples for TNPs include mesoporous silica nanoparticles, luminescence nanoparticles, carbon-based nanomaterials, metal nanoparticles, and magnetic nanoparticles. These TNPs have emerged as single and powerful cancer-treating multifunctional nanoplatforms, as they widely provide the necessary functionalities to overcome the previous/conventional limitations including lack of the site-specific delivery of anti-cancer drugs, and real-time continuous monitoring of the target cancer sites while performing therapeutic actions. This has been mainly possible due to the association of the as-developed TNPs with the already-available unique diagnostic (e.g., luminescence, photoacoustic, and magnetic resonance imaging) and therapeutic (e.g., photothermal, photodynamic, hyperthermia therapy) modalities in the biomedical field. In this review, we have discussed in detail about the recent developments on the aforementioned important TNPs without/with targeting ability (i.e., attaching them with ligands or tumor-specific antibodies) and also the strategies that are implemented to increase their tumor accumulation and to enhance their theranostic efficacies for effective biomedical cancer treatments.

Nanoscale coordination polymers induce immunogenic cell death by amplifying radiation therapy mediated oxidative stress

Radiation therapy can potentially induce immunogenic cell death, thereby priming anti-tumor adaptive immune responses. However, radiation-induced systemic immune responses are very rare and insufficient to meet clinical needs. Here, we demonstrate a synergetic strategy for boosting radiation-induced immunogenic cell death by constructing gadolinium-hemin based nanoscale coordination polymers to simultaneously perform X-ray deposition and glutathione depletion. Subsequently, immunogenic cell death is induced by sensitized radiation to potentiate checkpoint blockade immunotherapies against primary and metastatic tumors. In conclusion, nanoscale coordination polymers-sensitized radiation therapy exhibits biocompatibility and therapeutic efficacy in preclinical cancer models, and has the potential for further application in cancer radio-immunotherapy.

Effects of Gadolinium MRI Contrast Agents on DNA Damage and Cell Survival when Used in Combination with Radiation

Gadolinium is a commonly used contrast agent for magnetic resonance imaging (MRI). The goal of this work was to determine how MRI contrast agents affect radiosensitivity for tumour cells. Using a 225kVp X-ray cabinet source, immunofluorescence and clonogenic assays were performed on six cancer cell lines: lung (H460), pancreas (MiaPaCa2), prostate (DU145), breast (MCF7), brain (U87) and liver (HEPG2). Dotarem® contrast agent, at concentrations of 0.2, 2 and 20 mM, was used to determine its effect on DNA damage and cell survival. Measurements were performed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the amount of gadolinium taken up by each cell line for each concentration. A statistically significant increase in DNA damage was seen for all cell lines at a dose of 1 Gy for concentrations of 2 and 20 mM, at 1 h postirradiation. At 24 h postirradiation, most of the DNA damage had been repaired, with approximately 90% repair for almost all doses of radiation and concentrations of Dotarem. Clonogenic results showed no statistically significant decrease in cell survival for any cell line or concentration. Uptake measurements showed cell line-specific variations in uptake, with MCF7 and HEPG2 cells having a high percentage uptake compared to other cell lines, with 151.4 ± 0.3 × 10-15 g and 194.8 ± 0.4 × 10-15 g per cell, respectively, at 2 mM Dotarem concentration. In this work, a variability in gadolinium uptake was observed between cell lines. A significant increase was seen in initial levels of DNA damage after 1 Gy irradiation for all six cancer cell lines; however, no significant decrease in cell survival was seen with the clonogenic assay. The observation of high levels of repair suggest that while initial levels of DNA damage are increased, this damage is almost entirely repaired within 24 h, and does not affect the ability of cells to survive and produce colonies.

Studies on the Exposure of Gadolinium Containing Nanoparticles with Monochromatic X-rays Drive Advances in Radiation Therapy

While conventional radiation therapy uses white X-rays that consist of a mixture of X-ray waves with various energy levels, a monochromatic X-ray (monoenergetic X-ray) has a single energy level. Irradiation of high-Z elements such as gold, silver or gadolinium with a synchrotron-generated monochromatic X-rays with the energy at or higher than their K-edge energy causes a photoelectric effect that includes release of the Auger electrons that induce DNA damage—leading to cell killing. Delivery of high-Z elements into cancer cells and tumor mass can be facilitated by the use of nanoparticles. Various types of nanoparticles containing high-Z elements have been developed. A recent addition to this growing list of nanoparticles is mesoporous silica-based nanoparticles (MSNs) containing gadolinium (Gd–MSN). The ability of Gd–MSN to inhibit tumor growth was demonstrated by evaluating effects of irradiating tumor spheroids with a precisely tuned monochromatic X-ray.

Human Serum Albumin in the Presence of AGuIX Nanoagents: Structure Stabilisation without Direct Interaction

The gadolinium-based nanoagent named AGuIX^® is a unique radiosensitizer and contrast agent which improves the performance of radiotherapy and medical imaging. Currently tested in clinical trials, AGuIX^® is administrated to patients via intravenous injection. The presence of nanoparticles in the blood stream may induce harmful effects due to undesired interactions with blood components. Thus, there is an emerging need to understand the impact of these nanoagents when meeting blood proteins. In this work, the influence of nanoagents on the structure and stability of the most abundant blood protein, human serum albumin, is presented. Synchrotron radiation circular dichroism showed that AGuIX^® does not bind to the protein, even at the high ratio of 45 nanoparticles per protein at 3 mg/L. However, it increases the stability of the albumin. Isothermal thermodynamic calorimetry and fluorescence emission spectroscopy demonstrated that the effect is due to preferential hydration processes. Thus, this study confirms that intravenous injection of AGuIX^® presents limited risks of perturbing the blood stream. In a wider view, the methodology developed in this work may be applied to rapidly evaluate the impact and risk of other nano-products that could come into contact with the bloodstream.

Gadolinium-Rose Bengal Coordination Polymer Nanodots for MR-/Fluorescence-Image-Guided Radiation and Photodynamic Therapy

Combination therapy based on nanomedicine has gained momentum in oncology in recent years, offering superior safety and efficacy over monotherapies. It is critical to design theranostics that are composed of imaging and therapeutic agents already approved. Herein, gadolinium (Gd)-rose bengal coordination polymer nanodots (GRDs) are reported. The GRDs exhibit a unique absorption property and 7.7-fold luminescence enhancement, as well as a 1.9-fold increase in singlet oxygen generation efficiency over free rose bengal. Meanwhile, GRDs exhibit a twofold increase in r₁ relaxivity over gadopentetic acid (Gd-DTPA) and have better X-ray absorption ability than rose bengal alone. These excellent properties of the GRDs are verified both in vitro and in vivo. The combination of photodynamic therapy (PDT) and radiation therapy (RT) more significantly inhibits tumor growth than monotherapies (i.e., PDT or RT). This work offers a new route to designing and synthesizing Gd-based nanotheranostics for image-guided cancer therapy.

X-ray Induced Hydroxyl Radical Generation by GdYVO4:Eu3+ Nanoparticles in Aqueous Solution: Main Mechanisms

We report on strong X-ray-induced hydroxyl radical (. O H ) generation in an aqueous solution containing UV light pre-treated GdYVO4:Eu3+ nanoparticles (L-GdYVO). The methods of optical spectroscopy were used to detect . O H in the solutions. The complex nature of the mechanism of . O H generation has been revealed and discussed. The experimental data obtained indicate that the mechanism of . O H generation is associated with two main processes: (i) direct . O H generation with the participation of thermalized h+ formed at X-ray irradiation, and (ii) X-ray-facilitated jumps of h+ formed in the nanoparticles’ (NPs’) valence band at UV light pre-treatment and trapped in local levels formed by random scattering potential. At the same time, for GdYVO4:Eu3+ nanoparticles, which were not exposed to UV light before the X-ray irradiation (D-GdYVO), a strong radioprotective effect ascribed to the electron-donation properties of V4+ ions was observed. Thus, depending on the pre-treatment condition, we can change the redox properties of GdYVO4:Eu3+ NPs in an opposite direction, which makes this nanomaterial a unique theranostic agent for radiation therapy (RT) enhancement, allowing the problem of radiation therapy (RT)-resistant hypoxic tumours to be overcome.

Gadolinium-Based Nanoparticles for Theranostic MRI-Guided Radiosensitization in Hepatocellular Carcinoma

Background: Radiation therapy (RT) of hepatocellular carcinoma (HCC) is limited by low tolerance of the liver to radiation, whereas radiosensitizers are effective in reducing the required radiation dose. Multimodality gadolinium-based nanoparticles (AGuIX) are small and have enhanced permeability and retention effects; thus, they are very suitable for radiation sensitizer HCC RT. Here, we evaluated the potential value of AGuIX for theranostic MRI-radiosensitization in HCC.

Methods: The radiosensitization effects of AGuIX were evaluated via in vitro and in vivo experiments. Tumor growth, apoptosis imaging, and immunohistochemistry were performed to verify the antitumor effects of RT with AGuIX.

Results:In vitro evaluation of the efficacy of radiosensitivity of the AGuIX demonstrated that the presence of AGuIX significantly decreased HepG2 cell survival when combined with an X-ray beam. In vivo MRI imaging showed the ratio of tumor/liver concentration of the AGuIX was the highest 1 h after intravenous injection. For antitumor effects, we found that the tumor size decreased by RT-only and RT with AGuIX. The antitumor effects were more effective with high-dose AGuIX-mediated RT. Apoptosis imaging and immunohistochemistry both demonstrated that the degree of the cell apoptosis was highest with a high dose of AGuIX-mediated RT.

Conclusions: This study provides compelling data that AGuIX can facilitate theranostic MRI-radiosensitization in HCC.

Codoping Enhanced Radioluminescence of Nanoscintillators for X-ray-Activated Synergistic Cancer Therapy and Prognosis Using Metabolomics

Radio- and photodynamic therapies are the first line of cancer treatments but suffer from poor light penetration and less radiation accumulation in soft tissues with high radiation toxicity. Therefore, a multifunctional nanoplatform with diagnosis-assisted synergistic radio- and photodynamic therapy and tools facilitating early prognosis are urgently needed to fight the war against cancer. Further, integrating cancer therapy with untargeted metabolomic analysis would collectively offer clinical pertinence through facilitating early diagnosis and prognosis. Here, we enriched scintillation of CeF₃ nanoparticles (NPs) through codoping Tb³⁺ and Gd³⁺ (CeF₃:Gd³⁺,Tb³⁺) for viable clinical approach in the treatment of deep-seated tumors. The codoped CeF₃:Gd³⁺,Tb³⁺ scintillating theranostic NPs were then coated with mesoporous silica, followed by loading with rose bengal (CGTS-RB) for later computed tomography (CT)- and magnetic resonance image (MRI)-guided X-ray stimulated synergistic radio- and photodynamic therapy (RT+XPDT) using low-dose, one-time X-ray irradiation. The results corroborated an efficient tumor regression with synergistic RT+XPDT relative to single RT. Global untargeted metabolome shifts highlighted the mechanism behind this efficient tumor regression using RT, and synergistic RT+XPDT treatment is due to the starvation of nonessential amino acids involved in protein and DNA synthesis and energy regulation pathways necessary for growth and progression. Our study also concluded that tumor and serum metabolites shift during disease progression and regression and serve as robust biomarkers for early assessment of disease state and prognosis. From our results, we propose that codoping is an effective and extendable technique to other materials for gaining high optical yield and multifunctionality and for use in diagnostic and therapeutic applications. Critically, the integration of multifunctional theranostic nanomedicines with metabolomics has excellent potential for the discovery of early metabolic biomarkers to aid in better clinical disease diagnosis and prognosis.

Pharmacokinetics and biodistribution study of self-assembled Gd-micelles demonstrating blood-pool contrast enhancement for MRI

Magnetic resonance angiography (MRA) requires the use of contrast agents (CAs) to enable accurate diagnosis. There are currently no CAs on the market with appropriate pharmacokinetic (PK) parameters, namely long persistence in the blood, that can be easily used for MRA. We have recently synthesized amphiphilic building blocks loaded with gadolinium (Gd), which self-assemble into Gd-micelles in aqueous media, and have evaluated their potential as a blood-pool contrast agent (BPCA) in vivo. To assess the short and long term PK of Gd-micelles, the blood and organs of the mice were analyzed at t = 30 min, 1, 2, 3 h, 7, 14 and 21 days. Gd-DOTA was used as a control because it is the gold-standard CA for MRA despite its rapid clearance from the blood compartment. Gd-micelles circulated in the blood for more than 3 h postinjection whereas Gd-DOTA was eliminated less than half an hour postinjection. No side effects were observed in the mice up to the end of the study at 21 days and no accumulation of Gd was observed in the brain or bones. The Magnetic Resonance Imaging (MRI) parameters and the results of this in vivo study indicate the true BCPA properties of Gd-micelles and warrant further development.

Enhanced cytotoxic and genotoxic effects of gadolinium-doped ZnO nanoparticles on irradiated lung cancer cells at megavoltage radiation energies

The purpose of this study was to investigate the radiation dose enhancement effects of gadolinium-doped zinc oxide nanoparticles (Gd-doped ZnO NPs) under the megavoltage (MV) X-ray irradiation. ZnO NPs have preferred photocatalytic properties under UV light for cancer killing. UV light has limited applications in cancer treatment and it is necessary to use X-ray photons with MV energies. In order to increase the absorption of radiation and also to enhance the imaging visualization capabilities of ZnO NPs, gadolinium (Gd) as a high atomic number element was selected for doping into the structure of ZnO NPs. Gd-doped ZnO NPs were synthesized by a chemical precipitation method and characterized by transmission electron microscopy, powder X-ray diffraction, ultraviolet-visible spectroscopy, and energy-dispersive X-ray techniques. Cellular uptake was assessed by TEM and inductively coupled plasma mass spectrometry. NPs cytotoxicity was analyzed by MTT assay and radiation dose enhancement was measured by clonogenic survival assay. Apoptosis induction, cell cycle progression, micronucleus formation and expression of DNA double-strand break repair genes of XRCC2 and XRCC4 were determined by flow cytometry, micronucleus assay, and quantitative real-time polymerase chain reaction. CT and MR imaging were used to analyze the image visualization capabilities of NPs. NPs characterization showed that highly pure crystalline Gd-doped ZnO NPs with a narrow size distribution and grain size of 9 nm were synthesized. Gd-doped ZnO NPs were distributed in the cells and showed dose-dependent toxicity. Combination of Gd-doped ZnO NPs with 6 MV X-rays induced dose-dependent radiosensitivity with sensitizer enhancement ratios (SER) of 1.47 and 1.61 for 10 and 20 μg/mL NPs concentrations. Cancer cells blocked in G1, apoptosis rates, and micronuclei formation was enhanced and inversely, the DNA repair efficiency was impaired by down regulation of the mRNA levels of XRCC2 and XRCC4 genes. Gd-doped ZnO NPs enhanced the contrasts of CT and MR images of cancer cells. Overall, the results of this study provide detailed biological insights on the dose enhancement of Gd-doped ZnO NPs at MV radiations, which would contribute to the further development of this potent theranostic platform for clinical applications.

Treatment of multiple brain metastases using gadolinium nanoparticles and radiotherapy: NANO-RAD, a phase I study protocol

INTRODUCTION

Occurrence of multiple brain metastases is a critical evolution of many cancers with significant neurological and overall survival consequences, despite new targeted therapy and standard whole brain radiotherapy (WBRT). A gadolinium-based nanoparticle, AGuIX, has recently demonstrated its effectiveness as theranostic and radiosensitiser agent in preclinical studies. The favourable toxicity profile in animals and its administration as a simple intravenous injection has motivated its use in patients with this first in human study.

METHODS AND ANALYSIS

The NANO-RAD study is a phase I, first in human injection, monocentric, open-label, dose-escalation study to investigate the safety, the tolerability and the spectrum of side effects of AGuIX in combination with WBRT (30 Gy, 10 fractions of 3 Gy) for patients with multiple brain metastases. Five dose escalation cohorts are planned: 15, 30, 50, 75 and 100 mg/kg. A total of 15-18 patients will be recruited into this trial. The primary objective is to determine the maximum-tolerated dose of AGuIX nanoparticles combined with WBRT for the treatment of multiple brain metastases. Toxicity will be assessed using the National Cancer Institute Common Toxicity Criteria V.4.03. Secondary objectives are pharmacokinetic profile, distribution of AGuIX in metastases and surrounding healthy tissue visualised by MRI, intracranial progression-free survival and overall survival. Intracranial response will be determined according to Response Evaluation Criteria in Solid Tumour Criteria V.1.1 comparing MRI performed prior to treatment and at each follow-up visits.

ETHICS AND DISSEMINATION

Approval was obtained from the ethics committee Sud Est V, France (Reference number 15-CHUG-48). The study was approved by the French National Agency for the Safety of Medicines and Health Products (ANSM) (Reference number 151519A-12). The results will be published in peer-reviewed journals or disseminated through national and international conferences.

TRIAL REGISTRATION NUMBER

NCT02820454; Pre-results.

Emerging Strategies of Nanomaterial-Mediated Tumor Radiosensitization

Nano-radiosensitization has been a hot concept for the past ten years, and the nanomaterial-mediated tumor radiosensitization method is mainly focused on increasing intracellular radiation deposition by high atomic number (high Z) nanomaterials, particularly gold (Au)-mediated radiation enhancement. Recently, various new nanomaterial-mediated radiosensitive approaches have been successively reported, such as catalyzing reactive oxygen species (ROS) generation, consuming intracellular reduced glutathione (GSH), overcoming tumor hypoxia, and various synergistic radiotherapy ways. These strategies may open a new avenue for enhancing the radiotherapeutic effect and avoiding its side effects. Nevertheless, reviews systematically summarizing these newly emerging methods and their radiosensitive mechanisms are still rare. Therefore, the general strategies of nanomaterial-mediated tumor radiosensitization are comprehensively summarized, particularly aiming at introducing the emerging radiosensitive methods. The strategies are divided into three general parts. First, methods on account of the intrinsic radiosensitive properties of nanoradiosensitizers for radiosensitization are highlighted. Then, newly developed synergistic strategies based on multifunctional nanomaterials for enhancing radiotherapy efficacy are emphasized. Third, nanomaterial-mediated radioprotection approaches for increasing the radiotherapeutic ratio are discussed. Importantly, the clinical translation of nanomaterial-mediated tumor radiosensitization is also covered. Finally, further challenges and outlooks in this field are discussed.

Synchrotron-based infrared microspectroscopy study on the radiosensitization effects of Gd nanoparticles at megavoltage radiation energies

Synchrotron-based infrared microspectroscopy is a powerful technique for disentangling biochemical effects in nanoparticle-based radiotherapy approaches.

Sequentially Triggered Delivery System of Black Phosphorus Quantum Dots with Surface Charge-Switching Ability for Precise Tumor Radiosensitization

Cancer radiotherapy suffers from drawbacks such as radiation resistance of hypoxic cells, excessive radiation that causes damage of adjacent healthy tissues, and concomitant side effects. Hence, radiotherapy sensitizers with improved radiotherapeutic performance and requiring a relatively small radiation dose are highly desirable. In this study, a nanosystem based on poly(lactic- co-glycolic acid) (PLGA) and ultrasmall black phosphorus quantum dots (BPQDs) is designed and prepared to accomplish precise tumor radiosensitization. The PLGA nanoparticles act as carriers to package the BPQDs to avoid off-target release and rapid degradation during blood circulation. The nanosystem that targets the polypeptide peptide motif Arg-Gly-Asp-Gys actively accumulates in tumor tissues. The 2,3-dimethylmaleic anhydride shell decomposes in an acidic microenvironment, and the nanoparticles become positively charged, thereby favoring cellular uptake. Furthermore, glutathione (GSH) deoxidizes the disulfide bond of cystamine and sequentially triggers release of BPQDs, rendering tumor cells sensitive to radiotherapy. The treatment utilizing the PLGA_-SS-D@BPQDs nanosystem and X-ray induces cell apoptosis triggered by overproduction of reactive oxygen species. In the in vivo study, the nanosystem shows excellent radiotherapy sensitization efficiency but negligible histological damage of the major organs. This study provides insights into the design and fabrication of surface-charge-switching and pH-responsive nanosystems as potent radiosensitizers to achieve excellent radiotherapy sensitization efficacy and negligible toxic side effects.

Elemental and optical imaging evaluation of zwitterionic gold nanoclusters in glioblastoma mouse models

We report in this study the in vivo biodistribution of ultra-small luminescent gold (Au) particles (∼1.5 nm core size; 17 kDa), so-called nanoclusters (NCs), stabilized by bidentate zwitterionic molecules in subcutaneous (s.c.) and orthotopic glioblastoma mice models. Particular investigations on renal clearance and tumor uptake were performed using highly sensitive advanced imaging techniques such as multi-elemental Laser-Induced Breakdown Spectroscopy (LIBS) imaging and in-line X-ray Synchrotron Phase Contrast Tomography (XSPCT). Results show a blood circulation time of 6.5 ± 1.3 min accompanied by an efficient and fast renal clearance through the cortex of the kidney with a 66% drop between 1 h and 5 h. With a similar size range, these Au NCs are 5 times more fluorescent than the well-described Au₂₅GSH₁₈ NCs in the near-infrared (NIR) region and present significantly stronger tumor uptake and retention illustrated by an in vivo s.c. tumor-to-skin ratio of 1.8 measured by non-invasive optical imaging and an ex vivo tumor-to-muscle of 6.1. This work highlights the pivotal role of surface coating in designing optimum Au NC candidates for cancer treatment.

Toxicological status of nanoparticles: What we know and what we don't know

The field of nanotechnology has grown exponentially during the last few decades, due in part to the use of nanoparticles in many manufacturing processes, as well as their potential as clinical agents for treatment of diseases and for drug delivery. This has created several new avenues by which humans can be exposed to nanoparticles. Unfortunately, investigations assessing the toxicological impacts of nanoparticles (i.e. nanotoxicity), as well as their possible risks to human health and the environment, have not kept pace with the rapid rise in their use. This has created a gap-in-knowledge and a substantial need for more research. Studies are needed to help complete our understanding of the mechanisms of toxicity of nanoparticles, as well as the mechanisms mediating their distribution and accumulation in cells and tissues and their elimination from the body. This review summarizes our knowledge on nanoparticles, including their various applications, routes of exposure, their potential toxicity and risks to human health.

Towards tailored management of malignant brain tumors with nanotheranostics

Malignant brain tumors still represent an unmet medical need given their rapid progression and often fatal outcome within months of diagnosis. Given their extremely heterogeneous nature, the assumption that a single therapy could be beneficial for all patients is no longer plausible. Hence, early feedback on drug accumulation at the tumor site and on tumor response to treatment would help tailor therapies to each patient's individual needs for personalized medicine. In this context, at the intersection between imaging and therapy, theranostic nanomedicine is a promising new technique for individualized management of malignant brain tumors. Although brain nanotheranostics has yet to be translated into clinical practice, this field is now a research hotspot due to the growing demand for personalized therapies. In this review, the barriers to the clinical implementation of theranostic nanomedicine for tracking tumor responses to treatment and for guiding stimulus-activated therapies and surgical resection of malignant brain tumors are discussed. Likewise, the criteria that nanotheranostic systems need to fulfil to become clinically relevant formulations are analyzed in depth, focusing on theranostic agents already tested in vivo. Currently, magnetic nanoparticles exploiting brain targeting strategies represent the first generation of preclinical theranostic nanomedicines for the management of malignant brain tumors.

STATEMENT OF SIGNIFICANCE

The development of nanocarriers that can be used both in imaging studies and the treatment of brain tumors could help identify which patients are most and least likely to respond to a given treatment. This will enable clinicians to adapt the therapy to the needs of the patient and avoid overdosing non-responders. Given the many different approaches to non-invasive techniques for imaging and treating brain tumors, it is important to focus on the strategies most likely to be implemented and to design the most feasible theranostic biomaterials that will bring nanotheranostics one step closer to clinical practice.

Virus-Inspired Nanogenes Free from Man-Made Materials for Host-Specific Transfection and Bio-Aided MR Imaging

Many viruses have a lipid envelope derived from the host cell membrane that contributes much to the host specificity and the cellular invasion. This study puts forward a virus-inspired technology that allows targeted genetic delivery free from man-made materials. Genetic therapeutics, metal ions, and biologically derived cell membranes are nanointegrated. Vulnerable genetic therapeutics contained in the formed "nanogene" can be well protected from unwanted attacks by blood components and enzymes. The surface envelope composed of cancer cell membrane fragments enables host-specific targeting of the nanogene to the source cancer cells and homologous tumors while effectively inhibiting recognition by macrophages. High transfection efficiency highlights the potential of this technology for practical applications. Another unique merit of this technology arises from the facile combination of special biofunction of metal ions with genetic therapy. Typically, Gd(III)-involved nanogene generates a much higher T₁ relaxation rate than the clinically used Gd magnetic resonance imaging agent and harvests the enhanced MRI contrast at tumors. This virus-inspired technology points out a distinctive new avenue for the disease-specific transport of genetic therapeutics and other biomacromolecules.

Using immunotherapy to boost the abscopal effect

More than 60 years ago, the effect whereby radiotherapy at one site may lead to regression of metastatic cancer at distant sites that are not irradiated was described and called the abscopal effect (from 'ab scopus', that is, away from the target). The abscopal effect has been connected to mechanisms involving the immune system. However, the effect is rare because at the time of treatment, established immune-tolerance mechanisms may hamper the development of sufficiently robust abscopal responses. Today, the growing consensus is that combining radiotherapy with immunotherapy provides an opportunity to boost abscopal response rates, extending the use of radiotherapy to treatment of both local and metastatic disease. In this Opinion article, we review evidence for this growing consensus and highlight emerging limitations to boosting the abscopal effect using immunotherapy. This is followed by a perspective on current and potential cross-disciplinary approaches, including the use of smart materials to address these limitations.

Big Potential from Small Agents: Nanoparticles for Imaging-Based Companion Diagnostics

The importance of medical imaging in the diagnosis and monitoring of cancer cannot be overstated. As personalized cancer treatments are gaining popularity, a need for more advanced imaging techniques has grown significantly. Nanoparticles are uniquely suited to fill this void, not only as imaging contrast agents but also as companion diagnostics. This review provides an overview of many ways nanoparticle imaging agents have contributed to cancer imaging, both preclinically and in the clinic, as well as charting future directions in companion diagnostics. We conclude that, while nanoparticle-based imaging agents are not without considerable scientific and developmental challenges, they enable enhanced imaging in nearly every modality, hold potential as in vivo companion diagnostics, and offer precise cancer treatment and maximize intervention efficacy.

Metal-based NanoEnhancers for Future Radiotherapy: Radiosensitizing and Synergistic Effects on Tumor Cells

Radiotherapy is one of the major therapeutic strategies for cancer treatment. In the past decade, there has been growing interest in using high Z (atomic number) elements (materials) as radiosensitizers. New strategies in nanomedicine could help to improve cancer diagnosis and therapy at cellular and molecular levels. Metal-based nanoparticles usually exhibit chemical inertness in cellular and subcellular systems and may play a role in radiosensitization and synergistic cell-killing effects for radiation therapy. This review summarizes the efficacy of metal-based NanoEnhancers against cancers in both in vitro and in vivo systems for a range of ionizing radiations including gamma-rays, X-rays, and charged particles. The potential of translating preclinical studies on metal-based nanoparticles-enhanced radiation therapy into clinical practice is also discussed using examples of several metal-based NanoEnhancers (such as CYT-6091, AGuIX, and NBTXR3). Also, a few general examples of theranostic multimetallic nanocomposites are presented, and the related biological mechanisms are discussed.

Evaluation of cell penetrating peptide coated Mn:ZnS nanoparticles for paclitaxel delivery to cancer cells

This work aimed at formulating paclitaxel (PTX) loaded cell penetrating peptide (CPP) coated Mn doped ZnS nanoparticles (Mn:ZnS NPs) for improved anti-cancer efficacy in vitro and in vivo. The developed PTX loaded Mn:ZnS NPs with different CPPs (PEN, pVEC and R9) showed enhanced anti-cancer effect compared to bare PTX, which has been validated by MTT assay followed by apoptosis assay and DNA fragmentation analysis. The in vivo bio-distribution and anti-cancer efficacy was studied on breast cancer xenograft model showing maximum tumor localization and enhanced therapeutic efficacy with R9 coated Mn:ZnS NPs (R9:Mn:ZnS NPs) and was confirmed by H/E staining. Thus, R9:Mn:ZnS NPs could be an ideal theranostic nano-carrier for PTX with enhanced  the rapeutic efficacy toward cancer cells, where penetration and sustainability of therapeutics are essential.

Nanoparticle radio-enhancement: principles, progress and application to cancer treatment

Enhancement of radiation effects by high-atomic number nanoparticles (NPs) has been increasingly studied for its potential to improve radiotherapeutic efficacy. The underlying principle of NP radio-enhancement is the potential to release copious electrons into a nanoscale volume, thereby amplifying radiation-induced biological damage. While the vast majority of studies to date have focused on gold nanoparticles with photon radiation, an increasing number of experimental, theoretical and simulation studies have explored opportunities offered by other NPs (e.g. gadolinium, platinum, iron oxide, hafnium) and other therapeutic radiation sources such as ion beams. It is thus of interest to the research community to consolidate findings from the different studies and summarise progress to date, as well as to identify strategies that offer promising opportunities for clinical translation. This is the purpose of this Topical Review.

Competitive Inhibition of the Enzyme-Mimic Activity of Gd-Based Nanorods toward Highly Specific Colorimetric Sensing of l-Cysteine

Gd-based nanomaterials offer interesting magnetic properties and have been heavily investigated for magnetic resonance imaging. The applicability of these materials beyond biomedical imaging remains limited. The current study explores the applicability of these rare-earth nanomaterials as nanozyme-mediated catalysts for colorimetric sensing of l-cysteine, an amino acid of high biomedical relevance. We show a facile solution-based strategy to synthesize two Gd-based nanomaterials viz. Gd(OH)₃ and Gd₂O₃ nanorods. We further establish the catalytic peroxidase-mimic nanozyme activity of these Gd(OH)₃ and Gd₂O₃ nanorods. This catalytic activity was suppressed specifically in the presence of l-cysteine that allowed us to develop a colorimetric sensor to detect this biologically relevant molecule among various other contaminants. This suppression, which could either be caused due to catalyst poisoning or enzyme inhibition, prompted extensive investigation of the kinetics of this catalytic inhibition in the presence of cysteine. This revealed a competitive inhibition process, a mechanism akin to those observed in natural enzymes, bringing nanozymes a step closer to the biological systems.