A theranostic approach based on the use of a dual boron/Gd agent to improve the efficacy of Boron Neutron Capture Therapy in the lung cancer treatment

Cutting-Edge Therapies for Lung Cancer

Lung cancer remains a formidable global health challenge that necessitates inventive strategies to improve its therapeutic outcomes. The conventional treatments, including surgery, chemotherapy, and radiation, have demonstrated limitations in achieving sustained responses. Therefore, exploring novel approaches encompasses a range of interventions that show promise in enhancing the outcomes for patients with advanced or refractory cases of lung cancer. These groundbreaking interventions can potentially overcome cancer resistance and offer personalized solutions. Despite the rapid evolution of emerging lung cancer therapies, persistent challenges such as resistance, toxicity, and patient selection underscore the need for continued development. Consequently, the landscape of lung cancer therapy is transforming with the introduction of precision medicine, immunotherapy, and innovative therapeutic modalities. Additionally, a multifaceted approach involving combination therapies integrating targeted agents, immunotherapies, or traditional cytotoxic treatments addresses the heterogeneity of lung cancer while minimizing its adverse effects. This review provides a brief overview of the latest emerging therapies that are reshaping the landscape of lung cancer treatment. As these novel treatments progress through clinical trials are integrated into standard care, the potential for more effective, targeted, and personalized lung cancer therapies comes into focus, instilling renewed hope for patients facing challenging diagnoses.

Proposal of recommended experimental protocols for in vitro and in vivo evaluation methods of boron agents for neutron capture therapy

Recently, boron neutron capture therapy (BNCT) has been attracting attention as a minimally invasive cancer treatment. In 2020, the accelerator-based BNCT with L-BPA (Borofalan) as its D-sorbitol complex (Steboronine®) for head and neck cancers was approved by Pharmaceutical and Medical Devices Agency for the first time in the world. As accelerator-based neutron generation techniques are being developed in various countries, the development of novel tumor-selective boron agents is becoming increasingly important and desired. The Japanese Society of Neutron Capture Therapy believes it is necessary to propose standard evaluation protocols at each stage in the development of boron agents for BNCT. This review summarizes recommended experimental protocols for in vitro and in vivo evaluation methods of boron agents for BNCT based on our experience with L-BPA approval.

In Vivo Application of Carboranes for Boron Neutron Capture Therapy (BNCT): Structure, Formulation and Analytical Methods for Detection

Carboranes have emerged as one of the most promising boron agents in boron neutron capture therapy (BNCT). In this context, in vivo studies are particularly relevant, since they provide qualitative and quantitative information about the biodistribution of these molecules, which is of the utmost importance to determine the efficacy of BNCT, defining their localization and (bio)accumulation, as well as their pharmacokinetics and pharmacodynamics. First, we gathered a detailed list of the carboranes used for in vivo studies, considering the synthesis of carborane derivatives or the use of delivery system such as liposomes, micelles and nanoparticles. Then, the formulation employed and the cancer model used in each of these studies were identified. Finally, we examined the analytical aspects concerning carborane detection, identifying the main methodologies applied in the literature for ex vivo and in vivo analysis. The present work aims to identify the current strengths and weakness of the use of carboranes in BNCT, establishing the bottlenecks and the best strategies for future applications.

Combined Gadolinium and Boron Neutron Capture Therapies for Eradication of Head-and-Neck Tumor Using Gd10B6 Nanoparticles under MRI/CT Image Guidance

Eradication of head-and-neck (H&N) tumors is very difficult and challenging because of the characteristic feature of frequent recurrence and the difficulty in killing cancer stem cells. Neutron capture therapy (NCT) is emerging as a noninvasive potential modality for treatments of various types of tumors. Herein, we report that 98.5% 10B-enriched anti-EGFR-Gd10B6 nanoparticles can not only deliver large doses of 158 μg 10B/g tumor tissues as well as 56.8 μg 157Gd/g tumor tissues with a very high tumor-to-blood (T/B) 10B ratio of 4.18, but also exert very effective CT/MRI image-guided combined GdBNCT effects on killing cancer stem cells and eradication of recurrent head-and-neck (H&N) tumors. This leads to a long average half-lifespan of 81 days for H&N tumor-bearing mice, which is a record-making result, and surpasses the best result reported in the literature using combined radiotherapy and T cell-mediated immunotherapy (70 d).

Exploiting Blood Transport Proteins as Carborane Supramolecular Vehicles for Boron Neutron Capture Therapy

Carboranes are promising agents for applications in boron neutron capture therapy (BNCT), but their hydrophobicity prevents their use in physiological environments. Here, by using reverse docking and molecular dynamics (MD) simulations, we identified blood transport proteins as candidate carriers of carboranes. Hemoglobin showed a higher binding affinity for carboranes than transthyretin and human serum albumin (HSA), which are well-known carborane-binding proteins. Myoglobin, ceruloplasmin, sex hormone-binding protein, lactoferrin, plasma retinol-binding protein, thyroxine-binding globulin, corticosteroid-binding globulin and afamin have a binding affinity comparable to transthyretin/HSA. The carborane@protein complexes are stable in water and characterized by favorable binding energy. The driving force in the carborane binding is represented by the formation of hydrophobic interactions with aliphatic amino acids and BH-π and CH-π interactions with aromatic amino acids. Dihydrogen bonds, classical hydrogen bonds and surfactant-like interactions also assist the binding. These results (i) identify the plasma proteins responsible for binding carborane upon their intravenous administration, and (ii) suggest an innovative formulation for carboranes based on the formation of a carborane@protein complex prior to the administration.

Low-density lipoprotein: a versatile nanoscale platform for targeted delivery

Low-density lipoprotein (LDL) is a small lipoprotein that plays a vital role in controlling lipid metabolism. LDL has a delicate nanostructure with unique physicochemical properties: superior payload capacity, long residence time in circulation, excellent biocompatibility, smaller size, and natural targeting. In recent decades, the superiority and feasibility of LDL particles as targeted delivery carriers have attracted much attention. In this review, we introduce the structure, composition, advantages, defects, and reconstruction of LDL delivery systems, summarize their research status and progress in targeted diagnosis and therapy, and finally look forward to the clinical application of LDL as an effective delivery vehicle.

Synthesis and Characterization of Gd-Functionalized B4C Nanoparticles for BNCT Applications

Inorganic nanoparticles of boron-rich compounds represent an attractive alternative to boron-containing molecules, such as boronophenylalanine or boranes, for BNCT applications. This work describes the synthesis and biological activity of multifunctional boron carbide nanoparticles stabilized with polyacrylic acid (PAA) and a gadolinium (Gd)-rich solid phase. A fluorophore (DiI) was included in the PAA functionalization, allowing the confocal microscopy imaging of the nanoparticles. Analysis of the interaction and activity of these fluorescent Gd-containing B₄C nanoparticles (FGdBNPs) with cultured cells was appraised using an innovative correlative microscopy approach combining intracellular neutron autoradiography, confocal, and SEM imaging. This new approach allows visualizing the cells, the FGdBNP, and the events deriving from the nuclear process in the same image. Quantification of ¹⁰B by neutron autoradiography in cells treated with FGdBNPs confirmed a significant accumulation of NPs with low levels of cellular toxicity. These results suggest that these NPs might represent a valuable tool for achieving a high boron concentration in tumoral cells.

A novel pH sensitive theranostic PLGA nanoparticle for boron neutron capture therapy in mesothelioma treatment

This study aims to develop poly lactic-co-glycolic acid (PLGA) nanoparticles with an innovative imaging-guided approach based on Boron Neutron Capture Therapy for the treatment of mesothelioma. The herein-reported results demonstrate that PLGA nanoparticles incorporating oligo-histidine chains and the dual Gd/B theranostic agent AT101 can successfully be exploited to deliver a therapeutic dose of boron to mesothelioma cells, significantly higher than in healthy mesothelial cells as assessed by ICP-MS and MRI. The selective release is pH responsive taking advantage of the slightly acidic pH of the tumour extracellular environment and triggered by the protonation of imidazole groups of histidine. After irradiation with thermal neutrons, tumoral and healthy cells survival and clonogenic ability were evaluated. Obtained results appear very promising, providing patients affected by this rare disease with an improved therapeutic option, exploiting PLGA nanoparticles.

Safe magnetic resonance imaging on biocompatible nanoformulations

Magnetic resonance imaging (MRI) holds promise for the early clinical diagnosis of various diseases, but most clinical MR techniques require the use of a contrast medium. Several nanomaterial (NM) mediated contrast agents (CAs) are widely used as T1- and T2-based MR contrast agents for clinical and non-clinical applications. Unfortunately, most NM-based CAs are toxic or non-biocompatible, restricting their practical/clinical applications. Therefore, the development of nontoxic and biocompatible CAs for clinical MRI diagnosis is highly desired. To this end, several biocompatible and biomimetic strategies have been developed to offer long blood circulation time, significant biocompatibility, in vivo biodistribution and high contrast ability for efficient imaging. However, detailed review reports on biocompatible NMs, specifically for MR imaging have not yet been summarized. Thus, in the present review we summarize  various surface coating strategies (such as polymers, proteins, cell membranes, etc.) to achieve biocompatible NPs, providing a detailed discussion of advances and future prospects for safe MRI imaging.

Gadolinium Neutron Capture Therapy (GdNCT) Agents from Molecular to Nano: Current Status and Perspectives

157Gd (natural abundance = 15.7%) has the highest thermal neutron capture cross section (σ) of 254,000 barns (1 barn = 10-28 m2) among stable (nonradioactive) isotopes in the periodic table. Another stable isotope, 155Gd (natural abundance = 14.8%), also has a high σ value of 60,700 barns. These σ values are higher than that of 10B (3840 barns, natural abundance = 19.9%), which is currently used as a neutron-absorbing isotope for boron neutron capture therapy agents. Energetic particles such as electrons and γ-rays emitted from Gd-isotopes after neutron beam absorption kill cancer cells by damaging DNAs inside cancer-cell nuclei without damaging normal cells if Gd-chemicals are positioned in cancer cells. To date, various Gd-chemicals such as commercial Gd-chelates used as magnetic resonance imaging contrast agents, modified Gd-chelates, nanocomposites containing Gd-chelates, fullerenes containing Gd, and solid-state Gd-nanoparticles have been investigated as gadolinium neutron capture therapy (GdNCT) agents. All GdNCT agents had exhibited cancer-cell killing effects, and the degree of the effects depended on the GdNCT agents used. This confirms that GdNCT is a promising cancer therapeutic technique. However, the commercial Gd-chelates were observed to be inadequate in clinical use because of their low accumulation in cancer cells due to their extracellular and noncancer targeting properties and rapid excretion. The other GdNCT agents exhibited higher accumulation in cancer cells, compared to Gd-chelates; consequently, they demonstrated higher cancer-cell killing effects. However, they still displayed limitations such as poor specificity to cancer cells. Therefore, continuous efforts should be made to synthesize GdNCT agents suitable in clinical applications. Herein, the principle of GdNCT, current status of GdNCT agents, and general design strategy for GdNCT agents in clinical use are discussed and reviewed.

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.

Mössbauer effect using 57Fe-ferrabisdicarbollide ([o-57FESAN]-): a glance into the potential of a low-dose approach for glioblastoma radiotherapy

Although a variety of cancers is initially susceptible to chemotherapy, they eventually develop multi-drug resistance. To overcome this situation, more effective and selective treatments are necessary by using anti-tumour agents...

Combined BNCT and PET for theranostics

This short review summarizes the issue of boron distribution monitoring in boron neutron capture therapy (BNCT), which remains a serious drawback of this powerful oncological treatment. Here we present the monitoring methods that are presently used with particular emphasis on the positron emission tomography (PET) which has the highest potential to be used for the real-time monitoring of boron biodistribution. We discuss the possibility of using present PET scanners to determine the boron uptake in vivo before the BNCT treatment with the use of p-boronphenylalanine (BPA) labeled with 18F isotope. Several examples of preclinical studies and clinical trials performed with the use of [18F]FBPA are shown. We also discuss shortly the perspectives of using other radiotracers and boron carriers which may significantly improve the boron imaging with the use of the state-of-the-art Total-Body PET scanners providing a theranostic approach in the BNCT.

Development of MRI-Detectable Boron-Containing Gold Nanoparticle-Encapsulated Biodegradable Polymeric Matrix for Boron Neutron Capture Therapy (BNCT)

This study aimed to develop a novel magnetic resonance imaging (MRI)-detectable boron (B)-containing nanoassemblies and evaluate their potential for boron neutron capture therapy (BNCT). Starting from the citrate-coated gold nanoparticles (AuNPs) (23.9 ± 10.2 nm), the diameter of poly (D, L-lactide-co-glycolide) AuNPs (PLGA-AuNPs) increased approximately 110 nm after the encapsulation of the PLGA polymer. Among various B drugs, the self-produced B cages had the highest loading efficiency. The average diameter of gadolinium (Gd)- and B-loaded NPs (PLGA-Gd/B-AuNPs) was 160.6 ± 50.6 nm with a B encapsulation efficiency of 28.7 ± 2.3%. In vitro MR images showed that the signal intensity of PLGA-Gd/B-AuNPs in T1-weighted images was proportional to its Gd concentration, and there exists a significantly positive relationship between Gd and B concentrations (R² = 0.74, p < 0.005). The hyperintensity of either 250 ± 50 mm³ (larger) or 100 ± 50 mm³ (smaller) N87 xenograft was clearly visualized at 1 h after intravenous injection of PLGA-Gd/B-AuNPs. However, PLGA-Gd/B-AuNPs stayed at the periphery of the larger xenograft while located near the center of the smaller one. The tumor-to-muscle ratios of B content, determined by inductively coupled plasma mass spectrometry, in smaller- and larger-sized tumors were 4.17 ± 1.42 and 1.99 ± 0.55, respectively. In summary, we successfully developed theranostic B- and Gd-containing AuNPs for BNCT in this study.

LDL mediated delivery of Paclitaxel and MRI imaging probes for personalized medicine applications

BACKGROUND

The combination of imaging and therapeutic agents in the same smart nanoparticle is a promising option to perform a minimally invasive imaging guided therapy. In this study, Low density lipoproteins (LDL), one of the most attractive biodegradable and biocompatible nanoparticles, were used for the simultaneous delivery of Paclitaxel (PTX), a hydrophobic antitumour drug and an amphiphilic contrast agent, Gd-AAZTA-C17, in B16-F10 melanoma cell line. These cells overexpress LDL receptors, as assessed by flow cytometry analysis.

RESULTS

PTX and Gd-AAZTA-C17 loaded LDLs (LDL-PTX-Gd) have been prepared, characterized and their stability was assessed under 72 h incubation at 37 °C and compared to LDL loaded with Gd-AAZTA-C17 (LDL-Gd) and LDL-PTX. The cytotoxic effect of LDL-PTX-Gd was evaluated by MTT assay. The anti-tumour drug loaded into LDLs showed a significantly higher toxicity on B16-F10 cells with respect to the commercially available formulation Paclitaxel kabi (PTX Kabi) used in clinical applications. Tumour cells uptake was initially assessed by ICP-MS and MRI on B16-F10 cell line. By the analysis of the image signal intensity, it was possible to extrapolate the amount of internalized PTX indirectly by the decrease of relaxation times caused by Gd, proportional to its concentration. Finally, the treatment with PTX loaded LDL on B16-F10 tumour bearing mice resulted in a marked reduction of tumour growth compared to the administration of PTX Kabi alone.

CONCLUSIONS

LDLs are selectively taken-up by tumour cells and can be successfully exploited for the selective delivery of Paclitaxel and imaging agents. For the first time the anon invasive "in vivo" determination of the amount of PTX accumulated in the tumour was possible, thanks to the use of theranostic agents of natural origin.

Theranostics in Boron Neutron Capture Therapy

Boron neutron capture therapy (BNCT) has the potential to specifically destroy tumor cells without damaging the tissues infiltrated by the tumor. BNCT is a binary treatment method based on the combination of two agents that have no effect when applied individually: ¹⁰B and thermal neutrons. Exclusively, the combination of both produces an effect, whose extent depends on the amount of ¹⁰B in the tumor but also on the organs at risk. It is not yet possible to determine the ¹⁰B concentration in a specific tissue using non-invasive methods. At present, it is only possible to measure the ¹⁰B concentration in blood and to estimate the boron concentration in tissues based on the assumption that there is a fixed uptake of ¹⁰B from the blood into tissues. On this imprecise assumption, BNCT can hardly be developed further. A therapeutic approach, combining the boron carrier for therapeutic purposes with an imaging tool, might allow us to determine the ¹⁰B concentration in a specific tissue using a non-invasive method. This review provides an overview of the current clinical protocols and preclinical experiments and results on how innovative drug development for boron delivery systems can also incorporate concurrent imaging. The last section focuses on the importance of proteomics for further optimization of BNCT, a highly precise and personalized therapeutic approach.

Low-density lipoprotein nanomedicines: mechanisms of targeting, biology, and theranostic potential

Native nanostructured lipoproteins such as low- and high-density lipoproteins (LDL and HDL) are powerful tools for the targeted delivery of drugs and imaging agents. While the cellular recognition of well-known HDL-based carriers occurs via interactions with an HDL receptor, the selective delivery and uptake of LDL particles by target cells are more complex. The most well-known mode of LDL-based delivery is via the interaction between apolipoprotein B (Apo-B) - the main protein of LDL - and the low-density lipoprotein receptor (LDLR). LDLR is expressed in the liver, adipocytes, and macrophages, and thus selectively delivers LDL carriers to these cells and tissues. Moreover, the elevated expression of LDLR in tumor cells indicates a role for LDL in the targeted delivery of chemotherapy drugs. In addition, chronic inflammation associated with hypercholesterolemia (i.e., high levels of endogenous LDL) can be abated by LDL carriers, which outcompete the deleterious oxidized LDL for uptake by macrophages. In this case, synthetic LDL nanocarriers act as 'eat-me' signals and exploit mechanisms of native LDL uptake for targeted drug delivery and imaging. Lastly, recent studies have shown that the delivery of LDL-based nanocarriers to macrophages via fluid-phase pinocytosis is a promising tool for atherosclerosis imaging. Hence, the present review summarizes the use of natural and synthetic LDL-based carriers for drug delivery and imaging and discusses various mechanisms of targeting.

Covalent Organic Polymer as a Carborane Carrier for Imaging-Facilitated Boron Neutron Capture Therapy

Boron neutron capture therapy (BNCT) is an atomic targeted radiotherapy that shows fantastic suppression impact on locally intrusive threatening tumors. One key factor for effective BNCT is to aggregate an adequate concentration (>20 ppm) of ¹⁰B in the cytoplasm of the tumor. Carborane-loaded polymer nanoparticles are promising because of their outstanding biocompatibility and plasma steadiness. In this study, a new class of carborane-loaded nanoscale covalent organic polymers (BCOPs) was prepared by a Schiff base condensation reaction, and their solubility was greatly improved in common solvents via alkyl chain engineering and size tailoring. The obtained BCOP-5T was further functionalized by biocompatible 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[amino(polyethylene-glycol)-2000] (DSPE-PEG, molecular weight 2000) to form stable aqueous-phase nanoparticles with a hydrodynamic diameter of around 100 nm. After chelating with radioactive copper-64, DSPE-BCOP-5T was tracked by positron emission tomography (PET) imaging and showed significant accumulation in the tumor. DSPE-BCOP-5T + neutron radiation showed remarkable tumor suppression in 4T1 tumor-bearing mice (murine breast cancer). No obvious physical tissue damage and abnormal behavior were observed, demonstrating that the boron delivery was successful and tumor-selective. To conclude, this study presents a theranostic COP-based platform with a well-defined composition, good biocompatibility, and satisfactory tumor accumulation, which is promising for PET imaging, drug delivery, and BNCT.

In vitro and in vivo BNCT investigations using a carborane containing sulfonamide targeting CAIX epitopes on malignant pleural mesothelioma and breast cancer cells

This study aims at merging the therapeutic effects associated to the inhibition of Carbonic Anhydrase IX (CAIX), an essential enzyme overexpressed by cancer cells including mesothelioma and breast cancer, with those ones brought by the application of Boron Neutron Capture Therapy (BNCT). This task was pursued by designing a sulfonamido-functionalised-carborane (CA-SF) that acts simultaneously as CAIX inhibitor and boron delivery agent. The CAIX expression, measured by Western blot analysis, resulted high in both mesothelioma and breast tumours. This finding was exploited for the delivery of a therapeutic dose of boron (> 20 μg/g) to the cancer cells. The synergic cytotoxic effects operated by the enzymatic inhibition and neutron irradiation was evaluated in vitro on ZL34, AB22 and MCF7 cancer cells. Next, an in vivo model was prepared by subcutaneous injection of AB22 cells in Balb/c mice and CA-SF was administered as inclusion complex with a β-cyclodextrin oligomer. After irradiation with thermal neutrons tumour growth was evaluated for 25 days by MRI. The obtained results appear very promising as the tumour growth was definitively markedly lower in comparison to controls and the CAIX inhibitor alone. This approach appears promising and it call consideration for the design of new therapeutic routes to cure patients affected by this disease.

Serum protein-based nanoparticles for cancer diagnosis and treatment

Serum protein as naturally essential biomacromolecules has recently emerged as a versatile carrier for diagnostic and therapeutic drug delivery for cancer nanomedicine with superior biocompatibility, improved pharmacokinetics and enhanced targeting capacity. A variety of serum proteins have been utilized for drug delivery, mainly including albumin, ferritin/apoferritin, transferrin, low-density lipoprotein, high-density lipoprotein and hemoglobin. As evidenced by the success of paclitaxel-bound albumin nanoparticles (Abraxane^TM), serum protein-based nanoparticles have gained attractive attentions for precise biological design and potential clinical application. In this review, we summarize the general design strategies, targeting mechanisms and recent development of serum protein-based nanoparticles in the field of cancer nanomedicine. Moreover, we also concisely specify the current challenges to be addressed for a bright future of serum protein-based nanomedicines.

Functional gadolinium-based nanoscale systems for cancer theranostics

Cancer theranostics is a new strategy for combating cancer that integrates cancer imaging and treatment through theranostic agents to provide an efficient and safe way to improve cancer prognosis. Design and synthesis of these cancer theranostic agents are crucial since these agents are required to be biocompatible, tumor-specific, imaging distinguishable and therapeutically efficacious. In this regard, several types of gadolinium (Gd)-based nanomaterials have been introduced to combine different therapeutic agents with Gd to enhance the efficacy of therapeutic agents. At the same time, the entire treatment procedure could be monitored via imaging tools due to incorporation of Gd ions, Gd chelates and Gd/other imaging probes in the theranostic agents. This review aims to overview recent advances in the Gd-based nanomaterials for cancer theranostics and perspectives for Gd nanomaterial-based cancer theranostics are provided.

Comparative Study on Neutron Irradiation Sensitization Effects of Nucleotide Borate Esters and Several Other Boron Agents

More effective boron-containing compounds are needed for use in boron neutron capture therapy (BNCT). Here, borate esters were synthesized by heating and dehydrating nucleotides adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), the nucleoside (inosine) or glycerol in the presence of boric acid (H₃BO₃). Borate ester products were compared to clinical boron agent boronophenylalanine (BPA) and several other borate esters for neutron-sensitization effects using the A549 cell line. Cells were incubated with boron agent solutions (2.3 mM) for 5 h, then washed, resuspended in fresh media, and irradiated with a neutron dose of 0.33 Sv followed by cell survival assessment using the CCK-8 method. Calculated radiosensitization values (control group cell survival rate/boron agent-treated experimental group cell survival rate) were 3.9 ± 0.2 (ATP borate ester), 2.4 ± 0.1 (BPA), 2.1 ± 0.1 (ADP borate ester), 1.9 ± 0.2 (AMP borate ester), 1.7 ± 0.3 (glycerin borate ester), 1.4 ± 0.1 (inosine borate ester), 1.3 ± 0.3 (triethanolamine borate ester) and 1.3 ± 0.5 (H₃BO₃). Borate esters derived from nucleotides ATP, ADP or AMP exhibited significantly higher sensitization values than did those derived from glycerol, inosine or triethanolamine. Notably, due to its relatively higher water solubility and degree of tumor cell enrichment, ATP borate ester exhibited the highest sensitization rate overall, significantly exceeding rates obtained for BPA and borate esters of ADP and AMP. Flow cytometric determinations of boron agent-treated cell survival at 24 h postirradiation revealed long-term apoptosis rates of 4.8-6.6 ± 0.2% (nucleotide borate ester groups) and 5.6 ± 0.3% (BPA group) compared to 3.9 ± 0.1% (irradiation control group without boron agent) and 2.6 ± 0.2% (blank control group). Significant differences between experimental and control groups demonstrated that nucleotide borate esters and BPA induced long-term radiosensitization effects. In particular, postirradiation percentages of ATP borate ester-treated cells progressing to DNA replication prophase (G₁ phase) increased significantly, while percentages of cells progressing to S phase significantly decreased, demonstrating cellular DNA replication inhibition. Meanwhile, boron content values of tumor tissue, measured using inductively coupled plasma mass spectrometry (ICP-MS) and expressed as tumor-to-normal tissue boron ratios (T/N), were not significantly different between nucleotide borate ester- and BPA-fed groups of tumor-bearing mice. However, tumor tissue boron concentrations of nucleotide borate ester-fed mice (0.81-0.88 ± 0.04 µg/g) significantly exceeded those of BPA-fed mice (0.52 ± 0.05 µg/g) and thus provided greater tumor tissue boron enrichment for achieving a stronger neutron radiation-sensitizing effect. In conclusion, nucleotide borate esters, especially ATP borate ester, exhibited superior neutron radiosensitization effects than did other representative borate ester compounds and significantly greater long-term radiation effects as well. Thus, nucleotide borate esters have several advantages over other borate esters for BNCT and therefore warrant further study.

Application of Nitroimidazole-Carbobane-Modified Phenylalanine Derivatives as Dual-Target Boron Carriers in Boron Neutron Capture Therapy

Boron neutron capture therapy (BNCT) has received extensive attention as noninvasive cell-level oncotherapy for treating solid cancer tumors. However, boron-containing drugs such as l-boronophenylalanine (BPA) and sodium borocaptate have low boron content and/or poor tumor-targeting ability, limiting their application. In this study, we designed and synthesized a series of nontoxic, dual-target boron carriers (B139, B142, and B151) with the ability to accumulate specifically in tumor cells. We found that the B139 uptake into hypoxic tumor regions was high, with a 70-fold boron content compared to BPA. In addition, in vivo observation showed that B139 can be trapped in tumor cells for a prolonged period and maintains an effective therapeutic concentration, with a peak boron concentration of 50.7 μg/g and a high tumor: blood boron ratio of >3, achieving ideal BNCT conditions. Cytotoxicity evaluation in mice further proved that B139 is safe and reliable. Therefore, B139 has great potential for BNCT application as a dual-target, safe, and efficient boron carrier.

Translational boron neutron capture therapy (BNCT) studies for the treatment of tumors in lung

PURPOSE

Boron neutron capture therapy (BNCT) combines selective accumulation of ¹⁰B carriers in tumor tissue with subsequent neutron irradiation. BNCT has been proposed for the treatment of multiple, non-resectable, diffuse tumors in lung. The aim of the present study was to evaluate the therapeutic efficacy and toxicity of BNCT in an experimental model of lung metastases of colon carcinoma in BDIX rats and perform complementary survival studies.

MATERIALS AND METHODS

We evaluated tumor control and toxicity in lung 2 weeks post-BNCT at 2 dose levels, including 5 experimental groups per dose level: T0 (euthanized pre-treatment), Boronophenylalanine-BNCT (BPA-BNCT), BPA + Sodium decahydrodecaborate-BNCT ((BPA + GB-10)-BNCT), Beam only (BO) and Sham (no treatment, same manipulation). Tumor response was assessed employing macroscopic and microscopic end-points. An additional experiment was performed to evaluate survival and oxygen saturation in blood.

RESULTS AND CONCLUSIONS

No dose-limiting signs of short/medium-term toxicity were observed in lung. All end-points revealed statistically significant BNCT-induced tumor control vs Sham at both dose levels. The survival experiment showed a statistically significant 45% increase in post-treatment survival time in the BNCT group (48 days) versus Sham (33 days). These data consistently revealed growth suppression of lung metastases by BNCT with no manifest lung toxicity. Highlights Boron Neutron Capture Therapy suppresses growth of experimental lung metastases No BNCT-induced short/medium-term toxicity in lung is associated with tumor control Boron Neutron Capture Therapy increased post-treatment survival time by 45.

Opportunistic dose amplification for proton and carbon ion therapy via capture of internally generated thermal neutrons

This paper presents Neutron Capture Enhanced Particle Therapy (NCEPT), a method for enhancing the radiation dose delivered to a tumour relative to surrounding healthy tissues during proton and carbon ion therapy by capturing thermal neutrons produced inside the treatment volume during irradiation. NCEPT utilises extant and in-development boron-10 and gadolinium-157-based drugs from the related field of neutron capture therapy. Using Monte Carlo simulations, we demonstrate that a typical proton or carbon ion therapy treatment plan generates an approximately uniform thermal neutron field within the target volume, centred around the beam path. The tissue concentrations of neutron capture agents required to obtain an arbitrary 10% increase in biological effective dose are estimated for realistic treatment plans, and compared to concentrations previously reported in the literature. We conclude that the proposed method is theoretically feasible, and can provide a worthwhile improvement in the dose delivered to the tumour relative to healthy tissue with readily achievable concentrations of neutron capture enhancement drugs.

An innovative therapeutic approach for malignant mesothelioma treatment based on the use of Gd/boron multimodal probes for MRI guided BNCT

The aim of this study is to develop an innovative imaging guided approach based on Boron Neutron Capture Therapy, for the treatment of mesothelioma, assisted by the quantification of the in vivo boron distribution by MRI. The herein reported results demonstrate that overexpressed Low Density Lipoproteins receptors can be successfully exploited to deliver to mesothelioma cells a therapeutic dose of boron (26 μg/g), significantly higher than in the surrounding tissue (3.5 μg/g). Boron and Gd cells uptake was assessed by ICP-MS and MRI on two mesothelioma (ZL34, AE17) and two healthy (MRC-5 and NMuMg) cell lines. An in vivo model was prepared by subcutaneous injection of ZL34 cells in Nu/Nu mice. After irradiation with thermal neutrons, tumor growth was evaluated for 40 days by MRI. Tumor masses of boron treated mice showed a drastic reduction of about 80-85%. The obtained results appear very promising providing patients affected by this rare disease with an improved therapeutic option, exploiting LDL transporters.

Bio-Inspired Protein-Based Nanoformulations for Cancer Theranostics

Over the past decade, more interests have been aroused in engineering protein-based nanoformulations for cancer treatment. This excitement originates from the success of FDA approved Abraxane (Albumin-based paclitaxel nanoparticles) in 2005. The new generation of biocompatible endogenous protein-based nanoformulations is currently constructed through delivering cancer therapeutic and diagnostic agents simultaneously, as named potential theranostics. Protein nanoformulations are commonly incorporated with dyes, contrast agents, drug payloads or inorganic nanoclusters, serving as imaging-guided combinatorial cancer therapeutics. Employing the nature identity of proteins, the theranostics, escape the clearance by reticuloendothelial cells and have a long blood circulation time. The nanoscale sizet allows them to be penetrated deeply into tumor tissues. In addition, stimuli release and targeted molecules are incorporated to improve the delivery efficiency. The ongoing advancement of protein-based nanoformulations for cancer theranostics in recent 5 years is reviewed in this paper. Fine-designed nanoformulations based on albumin, ferritin, gelatin, and transferrin are highlighted from the literature. Finally, the current challenges are identified in translating protein-based nanoformulations from laboratory to clinical trials.

Theranostic Nanoparticles Loaded with Imaging Probes and Rubrocurcumin for Combined Cancer Therapy by Folate Receptor Targeting

The combination of different therapeutic modalities is a promising option to combat the recurrence of tumors. In this study, polylactic and polyglycolic acid nanoparticles were used for the simultaneous delivery of a boron-curcumin complex (RbCur) and an amphiphilic gadolinium complex into tumor cells with the aim of performing boron and gadolinium neutron capture therapy (NCT) in conjunction with the additional antiproliferative effects of curcumin. Furthermore, the use of Gd complexes allows magnetic resonance imaging (MRI) assessment of the amount of B and Gd internalized by tumor cells. Poly(lactic-co-glycolic acid) (PLGA) nanoparticles were targeted to ovarian cancer (IGROV-1) cells through folate receptors, by including in the formulation a PEGylated phospholipid functionalized with the folate moiety. NCT was performed on IGROV-1 cells internalizing 6.4 and 78.6 μg g^-1 of ¹⁰ B and ¹⁵⁷ Gd, respectively. The synergic action of neutron treatment and curcumin cytotoxicity was shown to result in a significant therapeutic improvement.

Lipoproteins and lipoprotein mimetics for imaging and drug delivery

Lipoproteins are a set of natural nanoparticles whose main role is the transport of fats within the body. While much work has been done to develop synthetic nanocarriers to deliver drugs or contrast media, natural nanoparticles such as lipoproteins represent appealing alternatives. Lipoproteins are biocompatible, biodegradable, non-immunogenic and are naturally targeted to some disease sites. Lipoproteins can be modified to act as contrast agents in many ways, such as by insertion of gold cores to provide contrast for computed tomography. They can be loaded with drugs, nucleic acids, photosensitizers or boron to act as therapeutics. Attachment of ligands can re-route lipoproteins to new targets. These attributes render lipoproteins attractive and versatile delivery vehicles. In this review we will provide background on lipoproteins, then survey their roles as contrast agents, in drug and nucleic acid delivery, as well as in photodynamic therapy and boron neutron capture therapy.

Insights into the use of gadolinium and gadolinium/boron-based agents in imaging-guided neutron capture therapy applications

Gadolinium neutron capture therapy (Gd-NCT) is currently under development as an alternative approach for cancer therapy. All of the clinical experience to date with NCT is done with (10)B, known as boron neutron capture therapy (BNCT), a binary treatment combining neutron irradiation with the delivery of boron-containing compounds to tumors. Currently, the use of Gd for NCT has been getting more attention because of its highest neutron cross-section. Although Gd-NCT was first proposed many years ago, its development has suffered due to lack of appropriate tumor-selective Gd agents. This review aims to highlight the recent advances for the design, synthesis and biological testing of new Gd- and B-Gd-containing compounds with the task of finding the best systems able to improve the NCT clinical outcome.

Lung cancer nanomedicine: potentials and pitfalls

Lung cancer is by far the most common cause of cancer-related deaths in the world. Nanoparticle-based therapies enable targeted drug delivery for lung cancer treatment with increased therapeutic efficiency and reduced systemic toxicity. At the same time, nanomedicine has the potential for multimodal treatment of lung cancer that may involve 'all-in-one' targeting of several tumor-associated cell types in a timely and spatially controlled manner. Therapeutic approaches, however, are hampered by a translational gap between basic scientists, clinicians and pharma industry due to suboptimal animal models and difficulties in scale-up production of nanoagents. This calls for a disease-centered approach with interdisciplinary basic and clinical research teams with the support of pharma industries.

GEM-loaded magnetic albumin nanospheres modified with cetuximab for simultaneous targeting, magnetic resonance imaging, and double-targeted thermochemotherapy of pancreatic cancer cells

Background

Targeted delivery is a promising strategy to improve the diagnostic imaging and therapeutic effect of cancers. In this paper, novel cetuximab (C225)-conjugated, gemcitabine (GEM)-containing magnetic albumin nanospheres (C225-GEM/MANs) were fabricated and applied as a theranostic nanocarrier to conduct simultaneous targeting, magnetic resonance imaging (MRI), and double-targeted thermochemotherapy against pancreatic cancer cells.

Methods

Fe₃O₄ nanoparticles (NPs) and GEM co-loaded albumin nanospheres (GEM/MANs) were prepared, and then C225 was further conjugated to synthesize C225-GEM/MANs. Their morphology, mean particle size, GEM encapsulation ratio, specific cell-binding ability, and thermal dynamic profiles were characterized. The effects of discriminating different EGFR-expressing pancreatic cancer cells (AsPC-1 and MIA PaCa-2) and monitoring cellular targeting effects were assessed by targeted MRI. Lastly, the antitumor efficiency of double/C225/magnetic-targeted and nontargeted thermochemotherapy was compared with chemotherapy alone using 3-(4, 5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and flow cytometry (FCM) assay.

Results

When treated with targeted nanospheres, AsPC-1 cells showed a significantly less intense MRI T2 signal than MIA PaCa-2 cells, while both cells had similar signal strength when incubated with nontargeted nanospheres. T2 signal intensity was significantly lower when magnetic and C225 targeting were combined, rather than used alone. The inhibitory and apoptotic rates of each thermochemotherapy group were significantly higher than those of the chemotherapy-alone groups. Additionally, both MTT and FCM analysis verified that double-targeted thermochemotherapy had the highest targeted killing efficiency among all groups.

Conclusion

The C225-GEM/MANs can distinguish various EGFR-expressing live pancreatic cancer cells, monitor diverse cellular targeting effects using targeted MRI imaging, and efficiently mediate double-targeted thermochemotherapy against pancreatic cancer cells.