Biocompatible Iron-Boron Nanoparticles Designed for Neutron Capture Therapy Guided by Magnetic Resonance Imaging

Synthesis of Gd-DTPA Carborane-Containing Compound and Its Immobilization on Iron Oxide Nanoparticles for Potential Application in Neutron Capture Therapy

Cancer is one of the leading causes of global mortality, and its incidence is increasing annually. Neutron capture therapy (NCT) is a unique anticancer modality capable of selectively eliminating tumor cells within normal tissues. The development of accelerator-based, clinically mountable neutron sources has stimulated a worldwide search for new, more effective compounds for NCT. We synthesized magnetic iron oxide nanoparticles (NPs) that concurrently incorporate boron and gadolinium, potentially enhancing the effectiveness of NCT. These magnetic nanoparticles underwent sequential modifications through silane polycondensation and allylamine graft polymerization, enabling the creation of functional amino groups on their surface. Characterization was performed using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive X-ray (EDX), dynamic light scattering (DLS), thermal gravimetric analysis (TGA), and transmission electron microscopy (TEM). ICP-AES measurements indicated that boron (B) content in the NPs reached 3.56 ppm/mg, while gadolinium (Gd) averaged 0.26 ppm/mg. Gadolinium desorption was observed within 4 h, with a peak rate of 61.74%. The biocompatibility of the NPs was confirmed through their relatively low cytotoxicity and sufficient cellular tolerability. Using NPs at non-toxic concentrations, we obtained B accumulation of up to 5.724 × 1010 atoms per cell, sufficient for successful NCT. Although limited by its content in the NP composition, the Gd amount may also contribute to NCT along with its diagnostic properties. Further development of the NPs is ongoing, focusing on increasing the boron and gadolinium content and creating active tumor targeting.

Physical Regimes and Mechanisms of Picosecond Laser Fragmentation of Gold Nanoparticles in Water from X-ray Probing and Atomistic Simulations

Laser fragmentation in liquids has emerged as a promising green chemistry technique for changing the size, shape, structure, and phase composition of colloidal nanoparticles, thus tuning their properties to the needs of practical applications. The advancement of this technique requires a solid understanding of the mechanisms of laser-nanoparticle interactions that lead to the fragmentation. While theoretical studies have made impressive practical and mechanistic predictions, their experimental validation is required. Hence, using the picosecond laser fragmentation of Au nanoparticles in water as a model system, the transient melting and fragmentation processes are investigated with a combination of time-resolved X-ray probing and atomistic simulations. The direct comparison of the diffraction profiles predicted in the simulations and measured in experiments has revealed a sequence of several nonequilibrium processes triggered by the laser irradiation. At low laser fluences, in the regime of nanoparticle melting and resolidification, the results provide evidence of a transient superheating of crystalline nanoparticles above the melting temperature. At fluences about three times the melting threshold, the fragmentation starts with evaporation of Au atoms and their condensation into small satellite nanoparticles. As fluence increases above five times the melting threshold, a transition to a rapid (explosive) phase decomposition of superheated nanoparticles into small liquid droplets and vapor phase atoms is observed. The transition to the phase explosion fragmentation regime is signified by prominent changes in the small-angle X-ray scattering profiles measured in experiments and calculated in simulations. The good match between the experimental and computational diffraction profiles gives credence to the physical picture of the cascade of thermal fragmentation regimes revealed in the simulations and demonstrates the high promise of the joint tightly integrated computational and experimental efforts.

Physical and chemical parameters determining the formation of gold-sp metal (Al, Ga, In, and Pb) nanoalloys

Alloying is a key step towards the fabrication of advanced and unique nanomaterials demanded by the next generation of nanotechnology solutions. In particular, the alloys of Au with the sp-metals are expected to have several appealing plasmonic and electronic properties for a wide range of applications in optics, catalysis, nanomedicine, sensing and quantum devices. However, little is known about the thermodynamic and synthetic factors leading to the successful alloying of Au and sp-metals at the nanoscale. In this work, Au-M nanoalloys, with M = Al, Ga, In, or Pb, have been synthesized by a green and single step laser ablation in liquid (LAL) approach in two environments (pure ethanol and anhydrous acetone). To delve deeper into the key parameters leading to successful alloying under the typical operating conditions of LAL, a multiparametric analysis was performed considering the mixing enthalpy from DFT calculations and other alloying descriptors such as the Hume-Rothery parameters. The results showed that the dominant factors for alloying change dramatically with the oxidative ability of the synthesis environment. In this way, the tendency of the four sp metals to alloy with gold was accurately predicted (R2 > 0.99) using only two and three parameters in anhydrous and non-anhydrous environments, respectively. These results are important to produce nanoalloys using LAL and other physical methods because they contribute to the understanding of factors leading to element mixing at the nanoscale under real synthetic conditions, which is crucial for guiding the realization of next-generation multifunctional metallic nanostructures.

In vivo investigation of boron-rich nanodrugs for treating triple-negative breast cancers via boron neutron capture therapy

Triple-negative breast cancer (TNBC) is characterized by highly proliferative cancer cells and is the only subtype of breast cancer that lacks a targeted therapy. Boron neutron capture therapy (BNCT) is an approach that combines chemotherapy with radiotherapy and can potentially offer beneficial targeted treatment for TNBC patients owing to its unique ability to eradicate cancer cells selectively while minimizing damage to the surrounding healthy cells. Since BNCT relies on specific delivery of a high loading of B10 to the tumor site, there is growing research interest to develop more potent boron-based drugs for BNCT that can overcome the limitations of small-molecule boron compounds. In this study, polyethylene-glycol-coated boron carbon oxynitride nanoparticles (PEG@BCNO) of size 134.2±23.6nm were prepared as a promising drug for BNCT owing to their high boron content and enhanced biocompatibility. The therapeutic efficiency of PEG@BCNO was compared with a state-of-the-art 10BPA boron drug in mice bearing MDA-MB-231 tumor. In the orthotopic mouse model, PEG@BCNO showed higher B10 accumulation in the tumor tissues (6 μg 10B/g tissue compared to 3 μg 10B/g tissue in mice administered B10-enriched 10BPA drug) despite using the naturally occurring 11B/10B boron precursor in the preparation of the BCNO nanoparticles. The in vivo biodistribution of PEG@BCNO in mice bearing MDA-MB-231 showed a tumor/blood ratio of ~3.5, which is comparable to that of the state-of-the-art 10BPA-fructose drug. We further demonstrated that upon neutron irradiation, the mice bearing MDA-MB-231 tumor cells treated with PEG@BCNO and 10BPA showed tumor growth delay times of 9 days and 1 day, respectively, compared to mice in the control group after BNCT. The doubling times (DTs) for mice treated with PEG@BCNO and 10BPA as well as mice in the control group were calculated to be 31.5, 19.8, and 17.7 days, respectively. Immunohistochemical staining for the p53 and caspase-3 antibodies revealed that mice treated with PEG@BCNO showed lower probability of cancer recurrence and greater level of cellular apoptosis than mice treated with 10BPA and mice in the control group. Our study thus demonstrates the potential of pegylated BCNO nanoparticles in effectively inhibiting the growth of TNBC tumors compared to the state-of-the-art boron drug 10BPA.

A transdermal drug delivery system based on dissolving microneedles for boron neutron capture therapy of melanoma

Boron neutron capture therapy (BNCT) is a promising therapy for malignant tumors that requires selective and high concentrations of 10B accumulation in tumor cells. Despite ongoing developments in novel boron agents and delivery carriers, the progress and clinical application of BNCT is still restricted by the low 10B accumulation and tumor-to-normal tissue (T/N) ratio. Herein, a dissolving microneedle-based transdermal drug delivery system was specifically designed for BNCT in a mouse model of melanoma. By incorporating fructose-BPA (F-BPA) into PVA microneedle tips, this system successfully delivered sufficient F-BPA into the melanoma site after the application of only two patches. Notably, the T/N ratio achieved through the treatment combining PVA/F-BPA MNs with BNCT (PVA/F-BPA MNs-BNCT) surpassed 93.16, signifying a great improvement. Furthermore, this treatment approach effectively inhibited tumor growth and significantly enhanced the survival rate of the mice. In brief, our study introduces a novel, simple, and efficient administration strategy for BNCT, opening new possibilities for the design of nanomedicine for BNCT.

Synthesis of multifunctional amorphous metallic shell on crystalline metallic nanoparticles

Colloidal nanoparticles can be coated with a conformal shell to form multifunctional nanoparticles. For instance, plasmonic, magnetic, and catalytic properties, chemical stability and biocompatibility can be mixed and matched. Here, a facile synthesis for depositing metal boride amorphous coatings on colloidal metallic nanocrystals is introduced. The synthesis is independent of core size, shape, and composition. We have found that the shell synthesis is limited to nanoparticles capped with short molecular weight and low binding energy ligands, and does not work with polyvinylpyrrolidone (PVP)-coated Ag nanoparticles or thiol-coated Au nanoparticles. Shell thickness can be as thin as 3 nm with no apparent pinholes. High pressure studies show that the coatings are highly resistant to crystallization and are strongly bonded to the crystalline core. By choosing either CoB or NiB for the coating, the composite nanoparticles can be either ferromagnetic or paramagnetic at room temperature, respectively.

Nanostructured boron agents for boron neutron capture therapy: a review of recent patents

Boron neutron capture therapy (BNCT) is a potential radiation therapy modality for cancer, and tumor-targeted stable boron-10 (10B) delivery agents are an important component of BNCT. Currently, two low-molecular-weight boron-containing compounds, sodium mercaptoundecahydro-closo-dodecaborate (BSH) and boronophenylalanine (BPA), are mainly used in BNCT. Although both have suboptimal tumor selectivity, they have shown some therapeutic benefit in patients with high-grade glioma and several other tumors. To improve the efficacy of BNCT, great efforts have been devoted for the development of new boron delivery agents with better uptake and favorable pharmacokinetic profiles. This article reviews the application and research progress of boron nanomaterials as boron carriers in boron neutron capture therapy and hopes to stimulate people's interest in nanomaterial-based delivery agents by summarizing various kinds of boron nanomaterial patents disclosed in the past decade.

Optimizing Boron Neutron Capture Therapy (BNCT) to Treat Cancer: An Updated Review on the Latest Developments on Boron Compounds and Strategies

Boron neutron capture therapy (BNCT) is a tumor-selective particle radiotherapy. It combines preferential boron accumulation in tumors and neutron irradiation. The recent initiation of BNCT clinical trials employing hospital-based accelerators rather than nuclear reactors as the neutron source will conceivably pave the way for new and more numerous clinical trials, leading up to much-needed randomized trials. In this context, it would be interesting to consider the implementation of new boron compounds and strategies that will significantly optimize BNCT. With this aim in mind, we analyzed, in this review, those articles published between 2020 and 2023 reporting new boron compounds and strategies that were proved therapeutically useful in in vitro and/or in vivo radiobiological studies, a critical step for translation to a clinical setting. We also explored new pathologies that could potentially be treated with BNCT and newly developed theranostic boron agents. All these radiobiological advances intend to solve those limitations and questions that arise during patient treatment in the clinical field, with BNCT and other therapies. In this sense, active communication between clinicians, radiobiologists, and all disciplines will improve BNCT for cancer patients, in a cost- and time-effective way.

Multi-Functional Boron-Delivery Agents for Boron Neutron Capture Therapy of Cancers

Boron neutron capture therapy (BNCT) is a binary cancer treatment that involves the irradiation of ¹⁰B-containing tumors with low-energy neutrons (thermal or epithermal). The alpha particles and recoiling Li nuclei that are produced in the ¹⁰B-capture nuclear reaction are high-linear-energy transfer particles that destroy boron-loaded tumor cells; therefore, BNCT has the potential to be a localized therapeutic modality. Two boron-delivery agents have been used in clinical trials of BNCT in patients with malignant brain tumors, cutaneous melanoma, or recurrent tumors of the head and neck region, demonstrating the potential of BNCT in the treatment of difficult cancers. A variety of potentially highly effective boron-delivery agents have been synthesized in the past four decades and tested in cells and animal models. These include boron-containing nucleosides, peptides, proteins, polyamines, porphyrins, liposomes, monoclonal antibodies, and nanoparticles of various types. The most promising agents are multi-functional boronated molecules and nanoparticles functionalized with tumor cell-targeting moieties that increase their tumor selectivity and contain a radiolabel or fluorophore to allow quantification of ¹⁰B-biodistribution and treatment planning. This review discusses multi-functional boron agents reported in the last decade, but their full potential can only be ascertained after their evaluation in BNCT clinical trials.

Boron Vehiculating Nanosystems for Neutron Capture Therapy in Cancer Treatment

Boron neutron capture therapy is a low-invasive cancer therapy based on the neutron fission process that occurs upon thermal neutron irradiation of ¹⁰B-containing compounds; this process causes the release of alpha particles that selectively damage cancer cells. Although several clinical studies involving mercaptoundecahydro-closo-dodecaborate and the boronophenylalanine-fructose complex are currently ongoing, the success of this promising anticancer therapy is hampered by the lack of appropriate drug delivery systems to selectively carry therapeutic concentrations of boron atoms to cancer tissues, allowing prolonged boron retention therein and avoiding the damage of healthy tissues. To achieve these goals, numerous research groups have explored the possibility to formulate nanoparticulate systems for boron delivery. In this review. we report the newest developments on boron vehiculating drug delivery systems based on nanoparticles, distinguished on the basis of the type of carrier used, with a specific focus on the formulation aspects.

Discovery of Discrete Stages in the Oxidation of exo-Tetrahydrodicyclopentadiene (C10H16) Droplets Doped with Titanium-Aluminum-Boron Reactive Mixed-Metal Nanopowder

Titanium (Ti), aluminum (Al), and boron (B) reactive mixed-metal nanopowders (Ti-Al-B RMNPs) represent attractive additives to hydrocarbon fuels such as exo-tetrahydrodicyclopentadiene (C₁₀H₁₆; JP-10) enhancing the limited volumetric energy densities of traditional hydrocarbons, but fundamental mechanisms and combustion stages in the oxidation have been obscure. This understanding is of vital significance in the development of next-generation propulsion systems and energy-generation technologies. Here, we expose distinct oxidation stages of single droplets of JP-10 doped with Ti-Al-B-RMNP exploiting innovative ultrasonic levitator technology coupled with time-resolved spectroscopic (UV-vis) and imaging diagnostics (optical and infrared). Two spatially and temporally distinct stages of combustion define a glow flame stage in which JP-10 and nanoparticles combust via a homogeneous gas phase (Al) and heterogeneous gas-surface oxidation (Ti, B) and a slower diffusion flame stage associated with the oxidation of JP-10. These findings enable the development of next-generation RMNP fuel additives with superior payload delivery capabilities.

Animal Tumor Models for Boron Neutron Capture Therapy Studies (Excluding Central Nervous System Solid Tumors)

Translational research in adequate experimental models is necessary to optimize boron neutron capture therapy (BNCT) for different pathologies. Multiple radiobiological in vivo studies have been performed in a wide variety of animal models, studying multiple boron compounds, routes of compound administration, and a range of administration strategies. Animal models are useful for the study of the stability and potential toxicity of new boron compounds or delivery systems, BNCT theranostic strategies, the evaluation of biomarkers to monitor BNCT therapeutic and adverse effects, and to study the BNCT immune response by the host against tumor cells. This article will mention examples of these studies, highlighting the importance of experimental animal models for the advancement of BNCT. Animal models are essential to design novel, safe, and effective clinical BNCT protocols for existing or new targets for BNCT.

Laser-ablative aqueous synthesis and characterization of elemental boron nanoparticles for biomedical applications

Boron-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.

Transforming Nuclear Medicine with Nanoradiopharmaceuticals

Nuclear medicine is expected to make major advances in cancer diagnosis and therapy; tumor-targeted radiopharmaceuticals preferentially eradicate tumors while causing minimal damage to healthy tissues. The current scope of nuclear medicine can be significantly expanded by integration with nanomedicine, which utilizes nanoparticles for cancer diagnosis and therapy by capitalizing on the increased surface area-to-volume ratio, the passive/active targeting ability and high loading capacity, the greater interaction cross section with biological tissues, the rich surface properties of nanomaterials, the facile decoration of nanomaterials with a plethora of functionalities, and the potential for multiplexing several functionalities within one construct. This review provides a comprehensive discussion of nuclear nanomedicine using tumor-targeted nanoparticles for cancer radiation therapy with either pre-embedded radionuclides or nonradioactive materials which can be extrinsically triggered using various external nuclear particle sources to produce in situ radioactivity. In addition, it describes the prospect of combining nuclear nanomedicine with other modalities to enable synergistically enhanced combination therapies. The review also discusses advances in the fabrication of radionuclides as well as describes laser ablation technologies for producing nanoradiopharmaceuticals, which combine the ease of production with exceptional purity and rapid biodegradability, along with additional imaging or therapeutic functionalities. From a practical standpoint, these attributes of nanoradiopharmaceuticals may provide distinct advantages in diagnostic/therapeutic sensitivity and specificity, imaging resolution, and scalability of turnkey platforms. Coupling image-guided targeted radiation therapy with the possibility of in situ activation of nanomaterials as well as combining with other therapeutic modalities using a multifunctional nanoplatform could herald an era of exciting technological and therapeutic advances to radically transform the landscape of nuclear medicine. The review concludes with a discussion of current challenges and presents the authors' views on future opportunities to stimulate further research in this rewarding field of high societal impact.

Importance of radiobiological studies for the advancement of boron neutron capture therapy (BNCT)

Boron neutron capture therapy (BNCT) is a tumour selective particle radiotherapy, based on the administration of boron carriers incorporated preferentially by tumour cells, followed by irradiation with a thermal or epithermal neutron beam. BNCT clinical results to date show therapeutic efficacy, associated with an improvement in patient quality of life and prolonged survival. Translational research in adequate experimental models is necessary to optimise BNCT for different pathologies. This review recapitulates some examples of BNCT radiobiological studies for different pathologies and clinical scenarios, strategies to optimise boron targeting, enhance BNCT therapeutic effect and minimise radiotoxicity. It also describes the radiobiological mechanisms induced by BNCT, and the importance of the detection of biomarkers to monitor and predict the therapeutic efficacy and toxicity of BNCT alone or combined with other strategies. Besides, there is a brief comment on the introduction of accelerator-based neutron sources in BNCT. These sources would expand the clinical BNCT services to more patients, and would help to make BNCT a standard treatment modality for various types of cancer. Radiobiological BNCT studies have been of utmost importance to make progress in BNCT, being essential to design novel, safe and effective clinical BNCT protocols.

The Development of Boron Analysis and Imaging in Boron Neutron Capture Therapy (BNCT)

Boron neutron capture therapy (BNCT) is a selective biological targeted nuclide technique for cancer therapy. It has the following attractive features: good targeting, high effectiveness, and causes slight damage to surrounding healthy tissue compared with other traditional methods. It has been considered as one of the promising methods for the treatment of various cancers. Measuring ¹⁰B concentrations is vital for BNCT. However, the existing technology and equipment cannot satisfy the real-time and accurate measurement requirements, and more efficient methods are in demand. The development of methods and imaging applied in BNCT to help measure boron concentration is described in this review.

The Pharmaceutical Technology Approach on Imaging Innovations from Italian Research

Many modern therapeutic approaches are based on precise diagnostic evidence, where imaging procedures play an essential role. To date, in the diagnostic field, a plethora of agents have been investigated to increase the selectivity and sensitivity of diagnosis. However, the most common drawbacks of conventional imaging agents reside in their non-specificity, short imaging time, instability, and toxicity. Moreover, routinely used diagnostic agents have low molecular weights and consequently a rapid clearance and renal excretion, and this represents a limitation if long-lasting imaging analyses are to be conducted. Thus, the development of new agents for in vivo diagnostics requires not only a deep knowledge of the physical principles of the imaging techniques and of the physiopathological aspects of the disease but also of the relative pharmaceutical and biopharmaceutical requirements. In this scenario, skills in pharmaceutical technology have become highly indispensable in order to respond to these needs. This review specifically aims to collect examples of newly developed diagnostic agents connoting the importance of an appropriate formulation study for the realization of effective products. Within the context of pharmaceutical technology research in Italy, several groups have developed and patented promising agents for fluorescence and radioactive imaging, the most relevant of which are described hereafter.

Polymer-coated silver-iron nanoparticles as efficient and biodegradable MRI contrast agents

Bimetallic nanoparticles allow new and synergistic properties compared to the monometallic equivalents, often leading to unexpected results. Here we present on silver-iron nanoparticles coated with polyethylene glycol, which exhibit a high transverse relaxivity (316 ± 13 mM^-1s^-1, > 3 times that of the most common clinical benchmark based on iron oxide), excellent colloidal stability and biocompatibility in vivo. Ag-Fe nanoparticles are obtained through a one-step, low-cost laser-assisted synthesis, which makes surface functionalization with the desired biomolecules very easy. Besides, Ag-Fe nanoparticles show biodegradation over a few months, as indicated by incubation in the physiological environment. This is crucial for nanomaterials removal from the living organism and, in fact, in vivo biodistribution studies evidenced that Ag-Fe nanoparticles tend to be cleared from liver over a period in which the benchmark iron oxide contrast agent persisted. Therefore, the Ag-Fe NPs offer positive prospects for solving the problems of biopersistence, contrast efficiency, difficulties of synthesis and surface functionalization usually encountered in nanoparticulate contrast agents.