Clinical scale synthesis of intrinsically radiolabeled and cyclic RGD peptide functionalized 198Au nanoparticles for targeted cancer therapy

Production, purification and formulation of nanoradiopharmaceutical with 211At: An emerging candidate for targeted alpha therapy

INTRODUCTION

Astatine-211 has attained significant interest in the recent times as a promising radioisotope for targeted alpha therapy (TAT) of cancer. In this study, we report the production of 211At via 209Bi (α, 2n) 211At reaction in a cyclotron and development of a facile radiochemical separation procedure to isolate 211At for formulation of nanoradiopharmaceuticals.

METHODS

Natural bismuth oxide target in pelletized form wrapped in Al foil was irradiated with 30 MeV α-beam in an AVF cyclotron. The irradiated target was dissolved in 2 M HNO3 followed by selective precipitation of Bi as Bi(OH)3 under alkaline condition. The radiochemically separated 211At was used for labeling cyclic RGD peptide conjugated gold nanoparticles (Au-RGD NPs) by surface adsorption. The radiochemical stability of 211At-Au-RGD NPs was evaluated in phosphate buffered saline (PBS) and human serum media.

RESULTS

The batch yield of 211At at the end of irradiation was ∼6 MBq.μA-1.h-1. After radiochemical separation, ∼80 % of 211At could be retrieved with >99.9 % radionuclidic purity. Au-RGD NPs (particle size 8.4±0.8 nm) could be labeled with 211At with >99 % radiolabeling yield. The radiolabeled nanoparticles retained their integrity in PBS and human serum media over a period of 21 h.

CONCLUSIONS

The present strategy simplifies 211At production in terms of purification and would increase affordable access to this radioisotope for TAT of cancer.

Cancer Brachytherapy at the Nanoscale: An Emerging Paradigm

Brachytherapy is an established treatment modality that has been globally utilized for the therapy of malignant solid tumors. However, classic therapeutic sealed sources used in brachytherapy must be surgically implanted directly into the tumor site and removed after the requisite period of treatment. In order to avoid the trauma involved in the surgical procedures and prevent undesirable radioactive distribution at the cancerous site, well-dispersed radiolabeled nanomaterials are now being explored for brachytherapy applications. This emerging field has been coined "nanoscale brachytherapy". Despite present-day advancements, an ongoing challenge is obtaining an advanced, functional nanomaterial that concurrently incorporates features of high radiolabeling yield, short labeling time, good radiolabeling stability, and long tumor retention time without leakage of radioactivity to the nontargeted organs. Further, attachment of suitable targeting ligands to the nanoplatforms would widen the nanoscale brachytherapy approach to tumors expressing various phenotypes. Molecular imaging using radiolabeled nanoplatforms enables noninvasive visualization of cellular functions and biological processes in vivo. In vivo imaging also aids in visualizing the localization and retention of the radiolabeled nanoplatforms at the tumor site for the requisite time period to render safe and effective therapy. Herein, we review the advancements over the last several years in the synthesis and use of functionalized radiolabeled nanoplatforms as a noninvasive substitute to standard brachytherapy sources. The limitations of present-day brachytherapy sealed sources are analyzed, while highlighting the advantages of using radiolabeled nanoparticles (NPs) for this purpose. The recent progress in the development of different radiolabeling methods, delivery techniques and nanoparticle internalization mechanisms are discussed. The preclinical studies performed to date are summarized with an emphasis on the current challenges toward the future translation of nanoscale brachytherapy in routine clinical practices.

RGD peptide in cancer targeting: Benefits, challenges, solutions, and possible integrin-RGD interactions

RGD peptide can be found in cell adhesion and signaling proteins, such as fibronectin, vitronectin, and fibrinogen. RGD peptides' principal function is to facilitate cell adhesion by interacting with integrin receptors on the cell surface. They have been intensively researched for use in biotechnology and medicine, including incorporation into biomaterials, conjugation to medicinal molecules or nanoparticles, and labeling with imaging agents. RGD peptides can be utilized to specifically target cancer cells and the tumor vasculature by engaging with these integrins, improving drug delivery efficiency and minimizing adverse effects on healthy tissues. RGD-functionalized drug carriers are a viable option for cancer therapy as this focused approach has demonstrated promise in the future. Writing a review on the RGD peptide can significantly influence how drugs are developed in the future by improving our understanding of the peptide, finding knowledge gaps, fostering innovation, and making drug design easier.

Radiosynthesis of Stable 198Au-Nanoparticles by Neutron Activation of αvβ3-Specific AuNPs for Therapy of Tumor Angiogenesis

This paper reports on the development of stable tumor-specific gold nanoparticles (AuNPs) activated by neutron irradiation as a therapeutic option for the treatment of cancer with high tumor angiogenesis. The AuNPs were designed with different mono- or dithiol-ligands and decorated with different amounts of Arg-Gly-Asp (RGD) peptides as a tumor-targeting vector for αvβ3 integrin, which is overexpressed in tissues with high tumor angiogenesis. The AuNPs were evaluated for avidity in vitro and showed favorable properties with respect to tumor cell accumulation. Furthermore, the therapeutic properties of the [198Au]AuNPs were evaluated in vitro on U87MG cells in terms of cell survival, suggesting that these [198Au]AuNPs are a useful basis for future therapeutic concepts.

Methods for Radiolabeling Nanoparticles (Part 3): Therapeutic Use

Following previously published systematic reviews on the diagnostic use of nanoparticles (NPs), in this manuscript, we report published methods for radiolabeling nanoparticles with therapeutic alpha-emitting, beta-emitting, or Auger's electron-emitting isotopes. After analyzing 234 papers, we found that different methods were used with the same isotope and the same type of nanoparticle. The most common type of nanoparticles used are the PLGA and PAMAM nanoparticles, and the most commonly used therapeutic isotope is 177Lu. Regarding labeling methods, the direct encapsulation of the isotope resulted in the most reliable and reproducible technique. Radiolabeled nanoparticles show promising results in metastatic breast and lung cancer, although this field of research needs more clinical studies, mainly on the comparison of nanoparticles with chemotherapy.

Advances in the design of amino acid and peptide synthesized gold nanoparticles for their applications

The field of therapeutics and diagnostics is advanced by nanotechnology-based approaches including the spatial-temporal release of drugs, targeted delivery, enhanced accumulation of drugs, immunomodulation, antimicrobial action, and high-resolution bioimaging, sensors and detection. Various compositions of nanoparticles (NPs) have been developed for biomedical applications; however, gold NPs (Au NPs) have attracted tremendous attention due to their biocompatibility, easy surface functionalization and quantification. Amino acids and peptides have natural biological activities as such, their activities enhance several folds in combination with NPs. Although peptides are extensively used to produce various functionalities of Au NPs, amino acids have also gained similar interests in producing amino acid-capped Au NPs due to the availability of amine, carboxyl and thiol functional groups. Henceforth, a comprehensive review is needed to timely bridge the synthesis and the applications of amino acid and peptide-capped Au NPs. This review aims to describe the synthesis mechanism of Au NPs using amino acids and peptides along with their applications in antimicrobial, bio/chemo-sensors, bioimaging, cancer therapy, catalysis, and skin regeneration. Moreover, the mechanisms of various activities of amino acid and peptide capped-Au NPs are presented. We believe this review will motivate researchers to better understand the interactions and long-term activities of amino acid and peptide-capped Au NPs for their success in various applications.

Radiolabelling and in vivo radionuclide imaging tracking of emerging pollutants in environmental toxicology: A review

Emerging pollutants (EPs) have become a global concern, attracting tremendous attention because of serious threats to human and animal health. EP diversity emanates from their behaviour and ability to enter the body via multiple pathways and exhibit completely different distribution, transport, and excretion. To better understand the in vivo behaviour of EPs, we reviewed radiolabelling and in vivo radionuclide imaging tracking of various EPs, including micro- and nano-plastics, perfluoroalkyl substances, metal oxides, pharmaceutical and personal care products, and so on. Because this accurate and quantitative imaging approach requires the labelling of radionuclides onto EPs, the main strategies for radiolabelling were reviewed, such as synthesis with radioactive precursors, element exchange, proton beam activation, and modification. Spatial and temporal biodistribution of various EPs was summarised in a heat map, revealing that the absorption, transport, and excretion of EPs are markedly related to their type, size, and pathway into the body. These findings implicate the potential toxicity of diverse EPs in organs and tissues. Finally, we discussed the potential and challenges of radionuclide imaging tracking of EPs, which can be considered in future EPs studies.

Activation cross sections of proton-induced reactions on natural platinum up to 30 MeV

Activation cross sections of proton-induced reactions on natural platinum were measured. The stacked-foil activation technique and high-resolution gamma-ray spectrometry were used. The production cross sections of ^{198, 196, 196m2, 195, 194, 193, 192, 191}Au, ¹⁹¹Pt, and ^{192, 190}Ir were determined up to 30 MeV. The experimental results were compared with previous experimental data and theoretical calculations in the TENDL-2019 library.

Systematic Review of Cancer Targeting by Nanoparticles Revealed a Global Association between Accumulation in Tumors and Spleen

Active targeting of nanoparticles toward tumors is one of the most rapidly developing topics in nanomedicine. Typically, this strategy involves the addition of cancer-targeting biomolecules to nanoparticles, and studies on this topic have mainly focused on the localization of such formulations in tumors. Here, the analysis of the factors determining efficient nanoparticle targeting and therapy, various parameters such as types of targeting molecules, nanoparticle type, size, zeta potential, dose, and the circulation time are given. In addition, the important aspects such as how active targeting of nanoparticles alters biodistribution and how non-specific organ uptake influences tumor accumulation of the targeted nanoformulations are discussed. The analysis reveals that an increase in tumor accumulation of targeted nanoparticles is accompanied by a decrease in their uptake by the spleen. There is no association between targeting-induced changes of nanoparticle concentrations in tumors and other organs. The correlation between uptake in tumors and depletion in the spleen is significant for mice with intact immune systems in contrast to nude mice. Noticeably, modulation of splenic and tumor accumulation depends on the targeting molecules and nanoparticle type. The median survival increases with the targeting-induced nanoparticle accumulation in tumors; moreover, combinatorial targeting of nanoparticle drugs demonstrates higher treatment efficiencies. Results of the comprehensive analysis show optimal strategies to enhance the efficiency of actively targeted nanoparticle-based medicines.

Gold nanoparticles meet medical radionuclides

Thanks to their unique optical and physicochemical properties, gold nanoparticles have gained increased interest as radiosensitizing, photothermal therapy and optical imaging agents to enhance the effectiveness of cancer detection and therapy. Furthermore, their ability to carry multiple medically relevant radionuclides broadens their use to nuclear medicine SPECT and PET imaging as well as targeted radionuclide therapy. In this review, we discuss the radiolabeling process of gold nanoparticles and their use in (multimodal) nuclear medicine imaging to better understand their specific distribution, uptake and retention in different in vivo cancer models. In addition, radiolabeled gold nanoparticles enable image-guided therapy is reviewed as well as the enhancement of targeted radionuclide therapy and nanobrachytherapy through an increased dose deposition and radiosensitization, as demonstrated by multiple Monte Carlo studies and experimental in vitro and in vivo studies.

The Peptide Functionalized Inorganic Nanoparticles for Cancer-Related Bioanalytical and Biomedical Applications

In order to improve their bioapplications, inorganic nanoparticles (NPs) are usually functionalized with specific biomolecules. Peptides with short amino acid sequences have attracted great attention in the NP functionalization since they are easy to be synthesized on a large scale by the automatic synthesizer and can integrate various functionalities including specific biorecognition and therapeutic function into one sequence. Conjugation of peptides with NPs can generate novel theranostic/drug delivery nanosystems with active tumor targeting ability and efficient nanosensing platforms for sensitive detection of various analytes, such as heavy metallic ions and biomarkers. Massive studies demonstrate that applications of the peptide-NP bioconjugates can help to achieve the precise diagnosis and therapy of diseases. In particular, the peptide-NP bioconjugates show tremendous potential for development of effective anti-tumor nanomedicines. This review provides an overview of the effects of properties of peptide functionalized NPs on precise diagnostics and therapy of cancers through summarizing the recent publications on the applications of peptide-NP bioconjugates for biomarkers (antigens and enzymes) and carcinogens (e.g., heavy metallic ions) detection, drug delivery, and imaging-guided therapy. The current challenges and future prospects of the subject are also discussed.

Biomaterial-mediated internal radioisotope therapy

Radiation therapy (RT), including external beam radiotherapy (EBRT) and internal radioisotope therapy (RIT), has been an indispensable strategy for cancer therapy in clinical practice in recent years. Ionized atoms and free radicals emitted from the nucleus of radioisotopes can cleave a single strand of DNA, inducing the apoptosis of cancer cells. Thus far, nuclides used for RIT could be classified into three main types containing alpha (α), beta (β), and Auger particle emitters. In order to enhance the bioavailability and reduce the physiological toxicity of radioisotopes, various biomaterials have been utilized as multifunctional nanocarriers, including targeting molecules, macromolecular monoclonal antibodies, peptides, inorganic nanomaterials, and organic and polymeric nanomaterials. Therapeutic radioisotopes have been labeled onto these nanocarriers via different methods (chelating, chemical doping, encapsulating, displacement) to inhibit or kill cancer cells. With the continuous development of research in this respect, more promising biomaterials as well as novel therapeutic strategies have emerged to achieve the high-performance RIT of cancer. In this review article, we summarize recent advances in biomaterial-mediated RIT of cancer and provide guidance for non-experts to understand nuclear medicine and to conduct cancer radiotherapy.

The Use of Alternative Strategies for Enhanced Nanoparticle Delivery to Solid Tumors

Nanomaterial (NM) delivery to solid tumors has been the focus of intense research for over a decade. Classically, scientists have tried to improve NM delivery by employing passive or active targeting strategies, making use of the so-called enhanced permeability and retention (EPR) effect. This phenomenon is made possible due to the leaky tumor vasculature through which NMs can leave the bloodstream, traverse through the gaps in the endothelial lining of the vessels, and enter the tumor. Recent studies have shown that despite many efforts to employ the EPR effect, this process remains very poor. Furthermore, the role of the EPR effect has been called into question, where it has been suggested that NMs enter the tumor via active mechanisms and not through the endothelial gaps. In this review, we provide a short overview of the EPR and mechanisms to enhance it, after which we focus on alternative delivery strategies that do not solely rely on EPR in itself but can offer interesting pharmacological, physical, and biological solutions for enhanced delivery. We discuss the strengths and shortcomings of these different strategies and suggest combinatorial approaches as the ideal path forward.

αvβ3-Specific Gold Nanoparticles for Fluorescence Imaging of Tumor Angiogenesis

This paper reports on the development of tumor-specific gold nanoparticles (AuNPs) as theranostic tools intended for target accumulation and the detection of tumor angiogenesis via optical imaging (OI) before therapy is performed, being initiated via an external X-ray irradiation source. The AuNPs were decorated with a near-infrared dye, and RGD peptides as the tumor targeting vector for α_vβ₃-integrin, which is overexpressed in tissue with high tumor angiogenesis. The AuNPs were evaluated in an optical imaging setting in vitro and in vivo exhibiting favorable diagnostic properties with regards to tumor cell accumulation, biodistribution, and clearance. Furthermore, the therapeutic properties of the AuNPs were evaluated in vitro on pUC19 DNA and on A431 cells concerning acute and long-term toxicity, indicating that these AuNPs could be useful as radiosensitizers in therapeutic concepts in the future.

Radiolabeled Gold Nanoparticles for Imaging and Therapy of Cancer

In the Last decades, nanotechnology has provided novel and alternative methodologies and tools in the field of medical oncology, in order to tackle the issues regarding the control and treatment of cancer in modern society. In particular, the use of gold nanoparticles (AuNPs) in radiopharmaceutical development has provided various nanometric platforms for the delivery of medically relevant radioisotopes for SPECT/PET diagnosis and/or radionuclide therapy. In this review, we intend to provide insight on the methodologies used to obtain and characterize radiolabeled AuNPs while reporting relevant examples of AuNPs developed during the last decade for applications in nuclear imaging and/or radionuclide therapy, and highlighting the most significant preclinical studies and results.

Nanoparticulate formulations of radiopharmaceuticals: Strategy to improve targeting and biodistribution properties

Application of nanotechnology principles in drug delivery has created opportunities for treatment of several diseases. Nanotechnology offers the advantage of overcoming the adverse biopharmaceutics or pharmacokinetic properties of drug molecules, to be determined by the transport properties of the particles themselves. Through the manipulation of size, shape, charge, and type of nanoparticle delivery system, variety of distribution profiles may be obtained. However, there still exists greater need to derive and standardize definitive structure property relationships for the distribution profiles of the delivery system. When applied to radiopharmaceuticals, the delivery systems assume greater significance. For the safety and efficacy of both diagnostics and therapeutic radiopharmaceuticals, selective localization in target tissue is even more important. At the same time, the synthesis and fabrication reactions of radiolabelled nanoparticles need to be completed in much shorter time. Moreover, the extensive understanding of the several interesting optical and magnetic properties of materials in nanoscale provides for achieving multiple objectives in nuclear medicine. This review discusses the various nanoparticle systems, which are applied for radionuclides and analyses the important bottlenecks that are required to be overcome for their more widespread clinical adaptation.