Bismuth nanoparticles-enhanced proton therapy: concept and biological assessment

Zelepukin I.V., Shevchenko K.G., Deyev S.M.

AbstractRapid uptake of nanoparticles by mononuclear phagocyte system (MPS) significantly hampers their therapeutic efficacy. Temporal MPS blockade is one of the few ways to overcome this barrier – the approach rediscovered many times under different names but never extensively used in clinic. Using meta-analysis of the published data we prove the efficacy of this technique for enhancing particle circulation in blood and their delivery to tumours, describe a century of its evolution and potential combined mechanism behind it. Finally, we discuss future directions of the research focusing on the features essential for successful clinical translation of the method.

Yang C., Zhang B., Lin X., Han Q., Bao H., Liu Y.

Concentration plays an essential role in generating hydroxyl radicals in irradiated nanoenhancer suspensions. In this paper, we used coumarin-3-carboxylic acid as a hydroxyl radical-specific probe to investigate the hydroxyl radical production of different concentration nanodiamonds (NDs) and CeO2 NPs in phosphate-buffered saline under x-ray irradiation. NDs significantly enhanced hydroxyl radical production, and the maximum enhancement of hydroxyl radical production was observed at a concentration of 10 µg/ml, with an enhanced factor of 1.398 ± 0.262. CeO2 NPs can increase and scavenge hydroxyl radicals at different concentration ranges, with the lowest and highest enhanced factors of 0.623 ± 0.069 and 1.738 ± 0.264, respectively. We tested the hydrodynamic diameter at various concentrations to explore the concentration effect further. We found that with increasing concentration, there might be factors, such as hydroxyl radical recombination and nanoparticle agglomeration, that lead to changes in the enhancement factor. Based on the data from previous and present studies, the experimental results indicate that the concentration factor is essential for hydroxyl radical generation in nanoenhancer suspensions under ionizing radiation. We also provide possible mechanisms for enhancing hydroxyl radical production by nanoenhancers in water under ionizing radiation and the decrease in enhancement factor at high concentrations of nanoenhancers.

Belyaev I.B., Zelepukin I.V., Kotelnikova P.A., Tikhonowski G.V., Popov A.A., Kapitannikova A.Y., Barman J., Kopylov A.N., Bratashov D.N., Prikhozhdenko E.S., Kabashin A.V., Deyev S.M., Zvyagin A.V.

AbstractBiodegradable nanomaterials can significantly improve the safety profile of nanomedicine. Germanium nanoparticles (Ge NPs) with a safe biodegradation pathway are developed as efficient photothermal converters for biomedical applications. Ge NPs synthesized by femtosecond‐laser ablation in liquids rapidly dissolve in physiological‐like environment through the oxidation mechanism. The biodegradation of Ge nanoparticles is preserved in tumor cells in vitro and in normal tissues in mice with a half‐life as short as 3.5 days. Biocompatibility of Ge NPs is confirmed in vivo by hematological, biochemical, and histological analyses. Strong optical absorption of Ge in the near‐infrared spectral range enables photothermal treatment of engrafted tumors in vivo, following intravenous injection of Ge NPs. The photothermal therapy results in a 3.9‐fold reduction of the EMT6/P adenocarcinoma tumor growth with significant prolongation of the mice survival. Excellent mass‐extinction of Ge NPs (7.9 L g−1 cm−1 at 808 nm) enables photoacoustic imaging of bones and tumors, following intravenous and intratumoral administrations of the nanomaterial. As such, strongly absorbing near‐infrared‐light biodegradable Ge nanomaterial holds promise for advanced theranostics.

Johny J., van Halteren C.E., Cakir F., Zwiehoff S., Behrends C., Bäumer C., Timmermann B., Rauschenbach L., Tippelt S., Scheffler B., Schramm A., Rehbock C., Barcikowski S.

AbstractGold 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.

Zhuang Z., Huang A., Tan X., Sun K., Chen C., Peng Q., Zhuang Z., Han T., Xiao H., Zeng Y., Yan W., Zhang J., Li Y.

•The discovery of p-block-metal bismuth-based ORR electrocatalysts is reported •The metallic Bi nanoparticles exhibit outstanding activity for H2O2 production •The single-atomic-site Bi catalysts give excellent performance for 4e− ORR •DFT calculations explain the origin of the high performance of Bi-based ORR catalysts For oxygen reduction reaction (ORR), replacing the conventional electrocatalysts based on platinum-group metals (PGMs) with alternatives based on non-noble metals is vital for the large-scale applications of green energy conversion and chemical synthesis. Here, we report the discovery of ORR catalysts based on the p-block-metal bismuth (Bi); the selectivity in ORR pathways could be controlled by tailoring the size of Bi. Specifically, the metallic Bi nanoparticles gave a high selectivity (>96%) for 2e− ORR, an ultra-high kinetic current density (3.8 mA·cm−2 at 0.65 V), and an excellent stability; in contrast, the single-atomic-site Bi catalysts gave a good selectivity for 4e− ORR and a corresponding half-wave potential of 0.875 V, approaching that of the best-known Fe/NC catalysts. This work presents new high-performance ORR catalysts based on the p-block-metal Bi, in contrast to the intensively studied d-block transition metals, and thus would provide new perspectives for developing PGM-free ORR catalysts. For oxygen reduction reaction (ORR), replacing the conventional electrocatalysts based on platinum-group metals (PGMs) with alternatives based on non-noble metals is vital for the large-scale applications of green energy conversion and chemical synthesis. Here, we report the discovery of ORR catalysts based on the p-block-metal bismuth (Bi); the selectivity in ORR pathways could be controlled by tailoring the size of Bi. Specifically, the metallic Bi nanoparticles gave a high selectivity (>96%) for 2e− ORR, an ultra-high kinetic current density (3.8 mA·cm−2 at 0.65 V), and an excellent stability; in contrast, the single-atomic-site Bi catalysts gave a good selectivity for 4e− ORR and a corresponding half-wave potential of 0.875 V, approaching that of the best-known Fe/NC catalysts. This work presents new high-performance ORR catalysts based on the p-block-metal Bi, in contrast to the intensively studied d-block transition metals, and thus would provide new perspectives for developing PGM-free ORR catalysts.

Akhtar M.J., Ahamed M., Alhadlaq H.

A review of recent literature suggests that bismuth oxide (Bi2O3, referred to as B in this article) nanoparticles (NPs) elicit an appreciable response only after a concentration above 40–50 µg/mL in different cells all having an epithelial origin, to the best of our knowledge. Here, we report the toxicological profile of Bi2O3 NPs (or BNPs) (71 ± 20 nm) in a human endothelial cell (HUVE cell line) in which BNPs exerted much steeper cytotoxicity. In contrast to a high concentration of BNPs (40–50 µg/mL) required to stimulate an appreciable toxicity in epithelial cells, BNPs induced 50% cytotoxicity in HUVE cells at a very low concentration (6.7 µg/mL) when treated for 24 h. BNPs induced reactive oxygen species (ROS), lipid peroxidation (LPO), and depletion of the intracellular antioxidant glutathione (GSH). BNPs also induced nitric oxide (NO,) which can result in the formation of more harmful species in a fast reaction that occurs with superoxide (O2•−). Exogenously applied antioxidants revealed that NAC (intracellular GSH precursor) was more effective than Tiron (a preferential scavenger of mitochondrial O2•−) in preventing the toxicity, indicating ROS production is extra-mitochondrial. Mitochondrial membrane potential (MMP) loss mediated by BNPs was significantly less than that of exogenously applied oxidant H2O2, and MMP loss was not as intensely reduced by either of the antioxidants (NAC and Tiron), again suggesting BNP-mediated toxicity in HUVE cells is extra-mitochondrial. When we compared the inhibitory capacities of the two antioxidants on different parameters of this study, ROS, LPO, and GSH were among the strongly inhibited biomarkers, whereas MMP and NO were the least inhibited group. This study warrants further research regarding BNPs, which may have promising potential in cancer therapy, especially via angiogenesis modulation.

Sisin N.N., Rahman W.N.

Radiotherapy treatment on cancer patients has the limitation of the possible side effects to the unrelated healthy tissues. Hence, radiosensitizers have been utilized to enhance the radiation dose onto the cancer sites and reduce the radiation effects on the surrounding areas. Recent findings have found the potentials of nanomaterials such as gold, platinum, and bismuth as radiosensitizers that would induce more radiation absorption due to their high atomic numbers (Z) profile. Among the types of high-Z nanomaterials that have been applied clinically as radiosensitizers are iron oxide, hafnium oxide, and gadolinium-based nanoparticles. Another potential radiosensitizer that has gained interest due to its safe utilization and anticancer properties is derived from natural compounds. Both radiosensitizers from nanomaterials and natural compound have shown intriguing outcome that might improve cancer treatment. This article reviews the effects of bismuth-based nanoparticles and natural compounds from the Oroxylum indicum plant as prospective radiosensitizers for radiotherapy. The individual effects of the bismuth nanoparticles and natural compounds, as well as their potential synergies in cancer radiotherapy, are discussed based on their physical, chemical, and biological interactions. This review summarizes the applicability and mechanisms of bismuth-based nanoparticles and baicalein natural compounds as radiosensitizers, which are valuable for future research and approaches in cancer radiotherapy.

Răileanu M., Straticiuc M., Iancu D., Andrei R., Radu M., Bacalum M.

The increased use of proton therapy has led to the need of better understanding the cellular mechanisms involved. The aim of this study was to investigate the effects induced by the accelerated proton beam in hepatocarcinoma cells. An existing facility in IFIN-HH, a 3 MV Tandetron™ accelerator, was used to irradiate HepG2 human hepatocarcinoma cells with doses between 0 and 3 Gy. Colony formation was used to assess the influence of radiation on cell long-term replication. Also, the changes induced at the mitochondrial level were shown by increased ROS and ATP levels as well as a decrease in the mitochondrial membrane potential. An increased dose has induced DNA damages and G2/M cell cycle arrest which leads to caspase 3/7 mediated apoptosis and senescence induction. Finally, the morphological and ultrastructural changes were observed at the membrane level and the nucleus of the irradiated cells. Thus, proton irradiation induces both morphological and functional changes in HepG2 cells.

Zelepukin I.V., Griaznova O.Y., Shevchenko K.G., Ivanov A.V., Baidyuk E.V., Serejnikova N.B., Volovetskiy A.B., Deyev S.M., Zvyagin A.V.

AbstractTumour microenvironment hinders nanoparticle transport deep into the tissue precluding thorough treatment of solid tumours and metastatic nodes. We introduce an anticancer drug delivery concept termed FlaRE (Flash Release in Endothelium), which represents alternative to the existing approaches based on enhanced permeability and retention effect. This approach relies on enhanced drug-loaded nanocarrier accumulation in vessels of the target tumour or metastasised organ, followed by a rapid release of encapsulated drug within tens of minutes. It leads to a gradient-driven permeation of the drug to the target tissue. This pharmaceutical delivery approach is predicted by theoretical modelling and validated experimentally using rationally designed MIL-101(Fe) metal-organic frameworks. Doxorubicin-loaded MIL-101 nanoparticles get swiftly trapped in the vasculature of the metastasised lungs, disassemble in the blood vessels within 15 minutes and release drug, which rapidly impregnates the organ. A significant improvement of the therapeutic outcome is demonstrated in animal models of early and late-stage B16-F1 melanoma metastases with 11-fold and 4.3-fold decrease of pulmonary melanoma nodes, respectively.

Tselikov G.I., Ermolaev G.A., Popov A.A., Tikhonowski G.V., Panova D.A., Taradin A.S., Vyshnevyy A.A., Syuy A.V., Klimentov S.M., Novikov S.M., Evlyukhin A.B., Kabashin A.V., Arsenin A.V., Novoselov K.S., Volkov V.S.

Recent developments in the area of resonant dielectric nanostructures have created attractive opportunities for concentrating and manipulating light at the nanoscale and the establishment of the new exciting field of all-dielectric nanophotonics. Transition metal dichalcogenides (TMDCs) with nanopatterned surfaces are especially promising for these tasks. Still, the fabrication of these structures requires sophisticated lithographic processes, drastically complicating application prospects. To bridge this gap and broaden the application scope of TMDC nanomaterials, we report here femtosecond laser-ablative fabrication of water-dispersed spherical TMDC (MoS 2 and WS 2 ) nanoparticles (NPs) of variable size (5 to 250 nm). Such NPs demonstrate exciting optical and electronic properties inherited from TMDC crystals, due to preserved crystalline structure, which offers a unique combination of pronounced excitonic response and high refractive index value, making possible a strong concentration of electromagnetic field in the NPs. Furthermore, such NPs offer additional tunability due to hybridization between the Mie and excitonic resonances. Such properties bring to life a number of nontrivial effects, including enhanced photoabsorption and photothermal conversion. As an illustration, we demonstrate that the NPs exhibit a very strong photothermal response, much exceeding that of conventional dielectric nanoresonators based on Si. Being in a mobile colloidal state and exhibiting superior optical properties compared to other dielectric resonant structures, the synthesized TMDC NPs offer opportunities for the development of next-generation nanophotonic and nanotheranostic platforms, including photothermal therapy and multimodal bioimaging.

Zelepukin I.V., Ivanov I.N., Mirkasymov A.B., Shevchenko K.G., Popov A.A., Prasad P.N., Kabashin A.V., Deyev S.M.

Bismuth-based compounds are considered to be the best candidates for computed tomography (CT) imaging of gastrointestinal (GI) tract due to high X-ray absorption. Here, we report the introduction of polymer-coated bismuth oxychloride (BiOCl) nanosheets for highly efficient CT imaging in healthy mice and animal with colitis. We demonstrate simple, low cost and fast aqueous synthesis protocol which provides gram-quantity yield of chemically stable BiOCl nanosheets. The developed contrast gives 2.55-fold better CT enhancement compared to conventional contrast with negligible in vivo toxicity. As a major finding we report a regioselective CT imaging of GI tract by using nanoparticles coated with differentially charged polymers. Coating of nanoparticles with a positively charged polymer leads to their fast accumulation in small intestine, while the coating with negatively charged polymers stimulates prolonged stomach retention. We propose that this effect may be explained by a pH-controlled aggregation of nanoparticles in stomach. This feature may become the basis for advancement in clinical diagnosis of entire GI tract.

Gerken L.R., Gogos A., Starsich F.H., David H., Gerdes M.E., Schiefer H., Psoroulas S., Meer D., Plasswilm L., Weber D.C., Herrmann I.K.

Nanoparticle-based radioenhancement is a promising strategy for extending the therapeutic ratio of radiotherapy. While (pre)clinical results are encouraging, sound mechanistic understanding of nanoparticle radioenhancement, especially the effects of nanomaterial selection and irradiation conditions, has yet to be achieved. Here, we investigate the radioenhancement mechanisms of selected metal oxide nanomaterials (including SiO2, TiO2, WO3 and HfO2), TiN and Au nanoparticles for radiotherapy utilizing photons (150 kVp and 6 MV) and 100 MeV protons. While Au nanoparticles show outstanding radioenhancement properties in kV irradiation settings, where the photoelectric effect is dominant, these properties are attenuated to baseline levels for clinically more relevant irradiation with MV photons and protons. In contrast, HfO2 nanoparticles retain some of their radioenhancement properties in MV photon and proton therapies. Interestingly, TiO2 nanoparticles, which have a comparatively low effective atomic number, show significant radioenhancement efficacies in all three irradiation settings, which can be attributed to the strong radiocatalytic activity of TiO2, leading to the formation of hydroxyl radicals, and nuclear interactions with protons. Taken together, our data enable the extraction of general design criteria for nanoparticle radioenhancers for different treatment modalities, paving the way to performance-optimized nanotherapeutics for precision radiotherapy. Nanoparticles have recently received attention in radiation therapy since they can act as radioenhancers. In this article, the authors report on the dose enhancement capabilities of a series of nanoparticles based on their metal core composition and beam characteristics, obtaining designing criteria for their optimal performance in specific radiotreatments.

Tikhonowski G.V., Popov A.A., Kurinnaya A.A., Garmash A.A., Gromushkina E.V., Zavestovskaya I.N., Klimentov S.M., Kabashin A.V.

The effect of laser radiation parameters on properties of bismuth (Bi) nanoparticles (NPs) produced by pulsed laser ablation in liquids (PLAL) was studied. We demonstrated that the average NPs size increases under the increase of laser radiation energy and the decrease in the distance from the focusing lens to the target surface. The obtained results provide a tool for a controllable synthesis of new functional nanomaterials for biomedical applications.

Pastukhov A.I., Belyaev I.B., Bulmahn J.C., Zelepukin I.V., Popov A.A., Zavestovskaya I.N., Klimentov S.M., Deyev S.M., Prasad P.N., Kabashin A.V.

AbstractBoron-based nano-formulations look very promising for biomedical applications, including photo- and boron neutron capture therapies, but the fabrication of non-toxic water-dispersible boron nanoparticles (NPs), which contain the highest boron atom concentration, is difficult using currently available chemical and plasma synthesis methods. Here, we demonstrate purely aqueous synthesis of clean boron NPs by methods of femtosecond laser ablation from a solid boron target in water, thus free of any toxic organic solvents, and characterize their properties. We show that despite highly oxidizing water ambience, the laser-ablative synthesis process follows an unusual scenario leading to the formation of boron NPs together with boric acid (H3BO3) as an oxidation by-product coating the nanoparticles, which acts to stabilize the elemental boron NPs dispersion. We then demonstrate the purification of boron NPs from residual boric acid in deionized water, followed by their coating with polyethylene glycol to improve colloidal stability and biocompatibility. It was found that the formed NPs have a spherical shape with averaged size of about 37 nm, and are composed of elemental boron in mostly amorphous phase with the presence of certain crystalline fraction. The synthesized NPs demonstrate low toxicity and exhibit strong absorption in the NIR window of relative tissue transparency, promising their use in photoacoustic imaging and phototherapy, in addition to their promise for neutron capture therapy. This combined potential ability of generating imaging and therapy functionalities makes laser-synthesized B NPs a very promising multifunctional agent for biomedical applications.

Duarte D., Vale N.

Current cancer therapy includes a variety of strategies that can comprise only one type of treatment or a combination of multiple treatments. Chemotherapy is still the gold standard for cancer therapy, though sometimes associated with undesired side effects and the development of drug resistance. For this reason, drug combination is an approach that has been proposed to overcome the problems related to monotherapy and several studies have already demonstrated the superiority of combined therapies compared to monotherapy. The main goal when designing and evaluating drug combinations is to achieve synergistic effects by demonstrating that the combined effects are greatly superior to the expected from the additive effects of the single drugs, allowing for dosage reduction and therefore decreasing toxicity. Nevertheless, synergism quantification is not a simple task due to the different definitions of additivity and over the years several reference models have been proposed based on different assumptions and with different mathematical frameworks. In this review, we begin to cover the available treatment options for cancer therapy, with emphasis on the importance of drug combinations in cancer therapy. We next describe the classical reference models that have been proposed for synergism evaluation, usually classified as effect-based and dose-effect based methods, with a brief analysis of the current limitations of these models. We also describe here the novel methods for the accurate quantification of drug interactions in combined treatments. At the end of this manuscript, we covered some of the most recent preclinical and clinical combination studies that reflect the importance of the appropriate, accurate and precise application of the concepts and methodologies here described for the evaluation of synergism.

Albadr R.J., Taher W.M., Alwan M., Jawad M.J., Hiba Mushtaq, Yaseen B.M.

Abd El-Raheem H., Helim R., Hassan R.Y., Youssef A.F., Korri-Youssoufi H., Kraiya C.

Popov A.L., Kolmanovich D.D., Chukavin N.N., Zelepukin I.V., Tikhonowski G.V., Pastukhov A.I., Popov A.A., Shemyakov A.E., Klimentov S.M., Ryabov V.A., Deyev S.M., Zavestovskaya I.N., Kabashin A.V.

Boron-enhanced proton therapy has recently appeared as a promising approach to increase the efficiency of proton therapy on tumor cells, and this modality can further be improved by the use of boron nanoparticles (B NPs) as local sensitizers to achieve enhanced and targeted therapeutic outcomes. However, the mechanisms of tumor cell elimination under boron-enhanced proton therapy still require clarification. Here, we explore possible molecular mechanisms responsible for the enhancement of therapeutic outcomes under boron NP-enhanced proton therapy. Spherical B NPs with a mode size of 25 nm were prepared by methods of pulsed laser ablation in water, followed by their coating by polyethylene glycol to improve their colloidal stability in buffers. Then, we assessed the efficiency of B NPs as sensitizers of cancer cell killing under irradiation with a 160.5 MeV proton beam. Our experiments showed that the combined effect of B NPs and proton irradiation induces an increased level of superoxide anion radical generation, which leads to the depolarization of mitochondria, a drop in their membrane mitochondrial potential, and the development of apoptosis. A comprehensive gene expression analysis (via RT-PCR) confirmed increased overexpression of 52 genes (out of 87 studied) involved in the cell redox status and oxidative stress, compared to 12 genes in the cells irradiated without B NPs. Other possible mechanisms responsible for the B NPs-induced radiosensitizing effect, including one related to the generation of alpha particles, are discussed. The obtained results give a better insight into the processes involved in the boron-induced enhancement of proton therapy and enable one to optimize parameters of proton therapy in order to maximize therapeutic outcomes.