Radiation Nanomedicine for EGFR-Positive Breast Cancer: Panitumumab-Modified Gold Nanoparticles Complexed to the β-Particle-Emitter, (177)Lu

Miniaturized Fab' imaging probe derived from a clinical antibody: Characterization and imaging in CRISPRi-attenuated mammary tumor models

Clinical imaging-assisted oncosurgical navigation requires cancer-specific miniaturized optical imaging probes. We report a near-infrared (NIR) Fab'-based epidermal growth factor receptor (EGFR)-specific probe carrying 3 NIR fluorophores (Fab'-800CW), which retained high-affinity binding to EGFR ectodomain (equilibrium KD E = 1 nM). Fab'-800CW showed a robust 4-times gain of fluorescence intensity (FI) and a 20% lifetime (FLT) increase under the conditions mimicking intracellular degradation. The probe was tested by using triple-negative breast cancer (TNBC) cell lines obtained by applying CRISPR interference (CRISPRi) effect of EGFR-targeting sgRNA and dCas9-KRAB chimera coexpression in MDA-MB-231 cells (WT cells). FI imaging in cell culture proved a 50% EGFR expression attenuation by CRISPRi. FI imaging in animals harboring attenuated or WT TNBC tumors with ex vivo corroboration identified differences between WT and CRISPRi tumors FI at 30 min post injection. Our results suggest the feasibility of EGFR expression imaging using a Fab'-based probe relevant for imaging-guided cancer surgery.

Nanoparticle-Mediated Drug Delivery Systems for Precision Targeting in Oncology

Nanotechnology has emerged as a transformative force in oncology, facilitating advancements in site-specific cancer therapy and personalized oncomedicine. The development of nanomedicines explicitly targeted to cancer cells represents a pivotal breakthrough, allowing the development of precise interventions. These cancer-cell-targeted nanomedicines operate within the intricate milieu of the tumour microenvironment, further enhancing their therapeutic efficacy. This comprehensive review provides a contemporary perspective on precision cancer medicine and underscores the critical role of nanotechnology in advancing site-specific cancer therapy and personalized oncomedicine. It explores the categorization of nanoparticle types, distinguishing between organic and inorganic variants, and examines their significance in the targeted delivery of anticancer drugs. Current insights into the strategies for developing actively targeted nanomedicines across various cancer types are also provided, thus addressing relevant challenges associated with drug delivery barriers. Promising future directions in personalized cancer nanomedicine approaches are delivered, emphasising the imperative for continued optimization of nanocarriers in precision cancer medicine. The discussion underscores translational research's need to enhance cancer patients' outcomes by refining nanocarrier technologies in nanotechnology-driven, site-specific cancer therapy.

Radiation nanomedicines for cancer treatment: a scientific journey and view of the landscape

BACKGROUND

Radiation nanomedicines are nanoparticles labeled with radionuclides that emit α- or β-particles or Auger electrons for cancer treatment. We describe here our 15 years scientific journey studying locally-administered radiation nanomedicines for cancer treatment. We further present a view of the radiation nanomedicine landscape by reviewing research reported by other groups.

MAIN BODY

Gold nanoparticles were studied initially for radiosensitization of breast cancer to X-radiation therapy. These nanoparticles were labeled with 111In to assess their biodistribution after intratumoural vs. intravenous injection. Intravenous injection was limited by high liver and spleen uptake and low tumour uptake, while intratumoural injection provided high tumour uptake but low normal tissue uptake. Further, [111In]In-labeled gold nanoparticles modified with trastuzumab and injected iintratumourally exhibited strong tumour growth inhibition in mice with subcutaneous HER2-positive human breast cancer xenografts. In subsequent studies, strong tumour growth inhibition in mice was achieved without normal tissue toxicity in mice with human breast cancer xenografts injected intratumourally with gold nanoparticles labeled with β-particle emitting 177Lu and modified with panitumumab or trastuzumab to specifically bind EGFR or HER2, respectively. A nanoparticle depot (nanodepot) was designed to incorporate and deliver radiolabeled gold nanoparticles to tumours using brachytherapy needle insertion techniques. Treatment of mice with s.c. 4T1 murine mammary carcinoma tumours with a nanodepot incorporating [90Y]Y-labeled gold nanoparticles inserted into one tumour arrested tumour growth and caused an abscopal growth-inhibitory effect on a distant second tumour. Convection-enhanced delivery of [177Lu]Lu-AuNPs to orthotopic human glioblastoma multiforme (GBM) tumours in mice arrested tumour growth without normal tissue toxicity. Other groups have explored radiation nanomedicines for cancer treatment in preclinical animal tumour xenograft models using gold nanoparticles, liposomes, block copolymer micelles, dendrimers, carbon nanotubes, cellulose nanocrystals or iron oxide nanoparticles. These nanoparticles were labeled with radionuclides emitting Auger electrons (111In, 99mTc, 125I, 103Pd, 193mPt, 195mPt), β-particles (177Lu, 186Re, 188Re, 90Y, 198Au, 131I) or α-particles (225Ac, 213Bi, 212Pb, 211At, 223Ra). These studies employed intravenous or intratumoural injection or convection enhanced delivery. Local administration of these radiation nanomedicines was most effective and minimized normal tissue toxicity.

CONCLUSIONS

Radiation nanomedicines have shown great promise for treating cancer in preclinical studies. Local intratumoural administration avoids sequestration by the liver and spleen and is most effective for treating tumours, while minimizing normal tissue toxicity.

Recent Advances in Boosting EGFR Tyrosine Kinase Inhibitors-Based Cancer Therapy

Epidermal growth factor receptor (EGFR) plays a key role in signal transduction pathways associated with cell proliferation, growth, and survival. Its overexpression and aberrant activation in malignancy correlate with poor prognosis and short survival. Targeting inhibition of EGFR by small-molecular tyrosine kinase inhibitors (TKIs) is emerging as an important treatment model besides of chemotherapy, greatly reshaping the landscape of cancer therapy. However, they are still challenged by the off-targeted toxicity, relatively limited cancer types, and drug resistance after long-term therapy. In this review, we summarize the recent progress of oral, pulmonary, and injectable drug delivery systems for enhanced and targeting TKI delivery to tumors and reduced side effects. Importantly, EGFR-TKI-based combination therapies not only greatly broaden the applicable cancer types of EGFR-TKI but also significantly improve the anticancer effect. The mechanisms of TKI resistance are summarized, and current strategies to overcome TKI resistance as well as the application of TKI in reversing chemotherapy resistance are discussed. Finally, we provide a perspective on the future research of EGFR-TKI-based cancer therapy.

Treatment of Orthotopic U251 Human Glioblastoma Multiforme Tumors in NRG Mice by Convection-Enhanced Delivery of Gold Nanoparticles Labeled with the β-Particle-Emitting Radionuclide, 177Lu

In this study, we investigated convection-enhanced delivery (CED) of 23 ± 3 nm gold nanoparticles (AuNPs) labeled with the β-particle-emitting radionuclide ¹⁷⁷Lu (¹⁷⁷Lu-AuNPs) for treatment of orthotopic U251-Luc human glioblastoma multiforme (GBM) tumors in NRG mice. The cytotoxicity in vitro of ¹⁷⁷Lu-AuNPs (0.0-2.0 MBq, 4 × 10¹¹ AuNPs) on U251-Luc cells was also studied by a clonogenic survival assay, and DNA double-strand breaks (DSBs) caused by β-particle emissions of ¹⁷⁷Lu were measured by confocal immunofluorescence microscopy for γH2AX. NRG mice with U251-Luc tumors in the right cerebral hemisphere of the brain were treated by CED of 1.1 ± 0.2 MBq of ¹⁷⁷Lu-AuNPs (4 × 10¹¹ AuNPs). Control mice received unlabeled AuNPs or normal saline. Tumor retention of ¹⁷⁷Lu-AuNPs was assessed by single-photon emission computed tomography/computed tomography (SPECT/CT) imaging and biodistribution studies. Radiation doses were estimated for the tumor, brain, and other organs. The effectiveness for treating GBM tumors was determined by bioluminescence imaging (BLI) and T2-weighted magnetic resonance imaging (MRI) and by Kaplan-Meier median survival. Normal tissue toxicity was assessed by monitoring body weight and hematology and blood biochemistry analyses at 14 d post-treatment. ¹⁷⁷Lu-AuNPs (2.0 MBq, 4 × 10¹¹ AuNPs) decreased the clonogenic survival of U251-Luc cells to 0.005 ± 0.002 and increased DNA DSBs by 14.3-fold compared to cells treated with unlabeled AuNPs or normal saline. A high proportion of ¹⁷⁷Lu-AuNPs was retained in the U251-Luc tumor in NRG mice up to 21 d with minimal re-distribution to the brain or other organs. The radiation dose in the tumor was high (599 Gy). The dose in the normal right cerebral hemisphere of the brain excluding the tumor was 93-fold lower (6.4 Gy), and 2000-3000-fold lower doses were calculated for the contralateral left cerebral hemisphere (0.3 Gy) or cerebellum (0.2 Gy). The doses in peripheral organs were <0.1 Gy. BLI revealed almost complete tumor growth arrest in mice treated with ¹⁷⁷Lu-AuNPs, while tumors grew rapidly in control mice. MRI at 28 d post-treatment and histological staining showed no visible tumor in mice treated with ¹⁷⁷Lu-AuNPs but large GBM tumors in control mice. All control mice reached a humane endpoint requiring sacrifice within 39 d (normal saline) or 45 d post-treatment (unlabeled AuNPs), while 5/8 mice treated with ¹⁷⁷Lu-AuNPs survived up to 150 d. No normal tissue toxicity was observed in mice treated with ¹⁷⁷Lu-AuNPs. We conclude that CED of ¹⁷⁷Lu-AuNPs was highly effective for treating U251-Luc human GBM tumors in the brain in NRG mice at amounts that were non-toxic to normal tissues. These ¹⁷⁷Lu-AuNPs administered by CED hold promise for treating patients with GBM to prevent recurrence and improve long-term outcome.

Novel Implications of Nanoparticle-Enhanced Radiotherapy and Brachytherapy: Z-Effect and Tumor Hypoxia

Radiotherapy and internal radioisotope therapy (brachytherapy) induce tumor cell death through different molecular signaling pathways. However, these therapies in cancer patients are constrained by dose-related adverse effects and local discomfort due to the prolonged exposure to the surrounding tissues. Technological advancements in nanotechnology have resulted in synthesis of high atomic elements such as nanomaterials, which can be used as radiosensitizers due to their photoelectric characteristics. The aim of this review is to elucidate the effects of novel nanomaterials in the field of radiation oncology to ameliorate dose-related toxicity through the application of ideal nanoparticle-based radiosensitizers such as Au (gold), Bi (bismuth), and Lu (Lutetium-177) for enhancing cytotoxic effects of radiotherapy via the high-Z effect. In addition, we discuss the role of nanoparticle-enhanced radiotherapy in alleviating tumor hypoxia through the nanodelivery of genes/drugs and other functional anticancer molecules. The implications of engineered nanoparticles in preclinical and clinical studies still need to be studied in order to explore potential mechanisms for radiosensitization by minimizing tumor hypoxia, operational/logistic complications and by overcoming tumor heterogeneity in radiotherapy/brachytherapy.

Recent progress in antibody-based therapeutics for triple-negative breast cancer

INTRODUCTION

Triple-negative breast cancer (TNBC) is a subtype of severely aggressive breast cancer that lacks the expression of oestrogen receptor (ER), progesterone receptor and human epidermal growth factor receptor 2 (HER2) and is highly metastatic and related to a poor prognosis. Current standard treatments are still limited to systemic chemotherapy, radiotherapy, and surgical resection. More effective treatments are urgently needed.

AREAS COVERED

The immunogenicity of TNBC has provided opportunities for the development of targeted immunotherapy. In this review, we focus on the recent development in antibody-based drug modalities, including angiogenesis inhibitors, immune checkpoint inhibitors, antibody-drug conjugates, immunoconjugates, T cell-redirecting bispecific antibodies and CAR-T cells, and their mechanisms of action in TNBC.

EXPERT OPINION

At present, the treatment of TNBC is still a major challenge that needs to be addressed. Novel immunotherapies are promising opportunities for improving the management of this aggressive disease.

Multifunctional high-Z nanoradiosensitizers for multimodal synergistic cancer therapy

Radiotherapy (RT) is one of the most common and effective clinical therapies for malignant tumors. However, there are several limitations that undermine the clinical efficacy of cancer RT, including the low X-ray attenuation coefficient of organs, serious damage to normal tissues, and radioresistance in hypoxic tumors. With the rapid development of nanotechnology and nanomedicine, high-Z nanoradiosensitizers provide novel opportunities to overcome radioresistance and improve the efficacy of RT by deposition of radiation energy through photoelectric effects. To date, several types of nanoradiosensitizers have entered clinical trials. Nevertheless, the limitation of the single treatment mode and the unclear mechanism of nanoparticle radiosensitization have hindered the further development of nanoradiosensitizers. In this review, we systematically describe the interaction mechanisms between X-rays and nanomaterials and summarize recent advances in multifunctional high-Z nanomaterials for radiotherapeutic-based multimodal synergistic cancer therapy. Finally, the challenges and prospects are discussed to stimulate the development of nanomedicine-based cancer RT.

Radiolabeled Gold Nanoseeds Decorated with Substance P Peptides: Synthesis, Characterization and In Vitro Evaluation in Glioblastoma Cellular Models

Despite some progress, the overall survival of patients with glioblastoma (GBM) remains extremely poor. In this context, there is a pressing need to develop innovative therapy strategies for GBM, namely those based on nanomedicine approaches. Towards this goal, we have focused on nanoparticles (AuNP-SP and AuNP-SPTyr8) with a small gold core (ca. 4 nm), carrying DOTA chelators and substance P (SP) peptides. These new SP-containing AuNPs were characterized by a variety of analytical techniques, including TEM and DLS measurements and UV-vis and CD spectroscopy, which proved their high in vitro stability and poor tendency to interact with plasma proteins. Their labeling with diagnostic and therapeutic radionuclides was efficiently performed by DOTA complexation with the trivalent radiometals ⁶⁷Ga and ¹⁷⁷Lu or by electrophilic radioiodination with ¹²⁵I of the tyrosyl residue in AuNP-SPTyr8. Cellular studies of the resulting radiolabeled AuNPs in NKR1-positive GBM cells (U87, T98G and U373) have shown that the presence of the SP peptides has a crucial and positive impact on their internalization by the tumor cells. Consistently, ¹⁷⁷Lu-AuNP-SPTyr8 showed more pronounced radiobiological effects in U373 cells when compared with the non-targeted congener ¹⁷⁷Lu-AuNP-TDOTA, as assessed by cell viability and clonogenic assays and corroborated by Monte Carlo microdosimetry simulations.

Active targeting strategy in nanomedicines using anti-EGFR ligands - A promising approach for cancer therapy and diagnosis

As active targeting using nanomedicines establishes itself as a strategy of choice in cancer therapy, several target receptors or ligands overexpressed in cancer cells have been identified and exploited. Among them, the epidermal growth factor receptor (EGFR) has emerged as one of the most promising oncomarkers for active targeting nanomedicines due to its overexpression and its active involvement in a wide range of cancer types. Henceforth, many novel EGFR-targeted nanomedicines for cancer therapy have been developed, giving encouraging results both in vitro and in vivo. This review focuses on different applications of such medicines in oncotherapy. On an important note, the contribution of EGFR-targeting ligands to final therapy efficacy along with current challenges and possible solutions or alternatives are emphasized.

Targeting Engineered Nanoparticles for Breast Cancer Therapy

Breast cancer (BC) is the second most common cancer in women globally after lung cancer. Presently, the most important approach for BC treatment consists of surgery, followed by radiotherapy and chemotherapy. The latter therapeutic methods are often unsuccessful in the treatment of BC because of their various side effects and the damage incurred to healthy tissues and organs. Currently, numerous nanoparticles (NPs) have been identified and synthesized to selectively target BC cells without causing any impairments to the adjacent normal tissues or organs. Based on an exploratory study, this comprehensive review aims to provide information on engineered NPs and their payloads as promising tools in the treatment of BC. Therapeutic drugs or natural bioactive compounds generally incorporate engineered NPs of ideal sizes and shapes to enhance their solubility, circulatory half-life, and biodistribution, while reducing their side effects and immunogenicity. Furthermore, ligands such as peptides, antibodies, and nucleic acids on the surface of NPs precisely target BC cells. Studies on the synthesis of engineered NPs and their impact on BC were obtained from PubMed, Science Direct, and Google Scholar. This review provides insights on the importance of engineered NPs and their methodology for validation as a next-generation platform with preventive and therapeutic effects against BC.

Oligonucleotide-Functionalized Gold Nanoparticles for Synchronous Telomerase Inhibition, Radiosensitization, and Delivery of Theranostic Radionuclides

Telomerase represents an attractive target in oncology as it is expressed in cancer but not in normal tissues. The oligonucleotide inhibitors of telomerase represent a promising anticancer strategy, although poor cellular uptake can restrict their efficacy. In this study, gold nanoparticles (AuNPs) were used to enhance oligonucleotide uptake. "match" oligonucleotides complementary to the telomerase RNA template subunit (hTR) and "scramble" (control) oligonucleotides were conjugated to diethylenetriamine pentaacetate (DTPA) for 111In-labeling. AuNPs (15.5 nm) were decorated with a monofunctional layer of oligonucleotides (ON-AuNP) or a multifunctional layer of oligonucleotides, PEG(polethylene glycol)800-SH (to reduce AuNP aggregation) and the cell-penetrating peptide Tat (ON-AuNP-Tat). Match-AuNP enhanced the cellular uptake of radiolabeled oligonucleotides while retaining the ability to inhibit telomerase activity. The addition of Tat to AuNPs increased nuclear localization. 111In-Match-AuNP-Tat induced DNA double-strand breaks and caused a dose-dependent reduction in clonogenic survival of telomerase-positive cells but not telomerase-negative cells. hTR inhibition has been reported to sensitize cancer cells to ionizing radiation, and 111In-Match-AuNP-Tat therefore holds promise as a vector for delivery of radionuclides into cancer cells while simultaneously sensitizing them to the effects of the emitted radiation.

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.

A model of modified meta-iodobenzylguanidine conjugated gold nanoparticles for neuroblastoma treatment

Iodine-131 meta-iodobenzylguanidine (131I-mIBG) has been utilized as a standard treatment to minimize adverse side effects by targeting therapies to bind to the norepinephrine transporter (NET) expressed on 90% of neuroblastoma cells. However, only a minority of patients who receive 131I-mIBG radiotherapy have clinical responses, and these are usually not curative. In this study, novel ligand-conjugated gold nanoparticles (GNPs) based on mIBG were synthesized and evaluated biologically with neuroblastoma cells in vitro. To induce specific internalization to the tumor cells and utilize it as a model for radioenhancement, 127I-modified mIBG was successfully synthesized and grafted covalently to the surface of carboxylated PEG-GNPs. 49.28% of the novel mIBG derivative was grafted on carboxylated PEG-GNPs. The particles were stable and not toxic to the normal fibroblast cell line, L929, even at the highest concentration tested (1013 NPs per mL) at 24, 48, and 72 h. Moreover, the cellular uptake of the model was decreased significantly in the presence of a NET inhibitor, suggesting that there was specific internalization into neuroblastoma cells line (SH-SY5Y) via the NET. Therefore, this model provides useful guidance toward the design of gold nanomaterials to enhance the efficiency of 131I-mIBG treatment in neuroblastoma patients. However, the investigation of radio-therapeutic efficiency after radioisotope 131I substitution will be further conducted in a radiation safety laboratory using an animal model.

Treatment with Radiopharmaceuticals and Radionuclides in Breast Cancer: Current Options

Radiopharmaceutical therapy (RPT) is an effective and safe treatment for many types of cancer. RPT acts by binding radioactive atoms to tumor-associated antigens, monoclonal antibodies, nanoparticles, peptides, and small molecules. These treatments ensure that a concentrated dose is delivered to the targeted tumor tissue while preserving the normal tissues surrounding the tumor. Given these features, RPT is superior to traditional methods. This review article aimed to performa comprehensive review and evaluation of the potential of radionuclides and radiopharmaceuticals used in breast cancer treatment in preclinical studies conducted in the last five years.

Nanomedicines functionalized with anti-EGFR ligands for active targeting in cancer therapy: Biological strategy, design and quality control

Recently, active targeting using nanocarriers with biological ligands has emerged as a novel strategy for improving the delivery of therapeutic and/or imaging agents to tumor cells. The presence of active targeting moieties on the surface of nanomedicines has been shown to play an important role in enhancing their accumulation in tumoral cells and tissues versus healthy ones. This property not only helps to increase the therapeutic index but also to minimize possible side effects of the designed nanocarriers. Since the overexpression of epidermal growth factor receptors (EGFR) is a common occurrence linked to the progression of a broad variety of cancers, the potential application of anti-EGFR immunotherapy and EGFR-targeting ligands in active targeting nanomedicines is getting increasing attention. Henceforth, the EGFR-targeted nanomedicines were extensively studied in vitro and in vivo but exhibited both satisfactory and disappointing results, depending on used protocols. This review is designed to give an overview of a variety of EGFR-targeting ligands available for nanomedicines, how to conjugate them onto the surface of nanoparticles, and the main analytical methods to confirm this successful conjugation.

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.

Perspectives on metals-based radioimmunotherapy (RIT): moving forward

Radioimmunotherapy (RIT) is FDA-approved for the clinical management of liquid malignancies, however, its use for solid malignancies remains a challenge. The putative benefit of RIT lies in selective targeting of antigens expressed on the tumor surface using monoclonal antibodies, to systemically deliver cytotoxic radionuclides. The past several decades yielded dramatic improvements in the quality, quantity, recent commercial availability of alpha-, beta- and Auger Electron-emitting therapeutic radiometals. Investigators have created new or improved existing bifunctional chelators. These bifunctional chelators bind radiometals and can be coupled to antigen-specific antibodies. In this review, we discuss approaches to develop radiometal-based RITs, including the selection of radiometals, chelators and antibody platforms (i.e. full-length, F(ab')2, Fab, minibodies, diabodies, scFv-Fc and nanobodies). We cite examples of the performance of RIT in the clinic, describe challenges to its implementation, and offer insights to address gaps toward translation.

Gold Nanoparticles as Radiosensitizers in Cancer Radiotherapy

The rapid development of nanotechnology offers a variety of potential therapeutic strategies for cancer treatment. High atomic element nanomaterials are often utilized as radiosensitizers due to their unique photoelectric decay characteristics. Among them, gold nanoparticles (GNPs) are one of the most widely investigated and are considered to be an ideal radiosensitizers for radiotherapy due to their high X-ray absorption and unique physicochemical properties. Over the last few decades, multi-disciplinary studies have focused on the design and optimization of GNPs to achieve greater dosing capability and higher therapeutic effects and highlight potential mechanisms for radiosensitization of GNPs. Although the radiosensitizing potential of GNPs has been widely recognized, its clinical translation still faces many challenges. This review analyses the different roles of GNPs as radiosensitizers in cancer radiotherapy and summarizes recent advances. In addition, the underlying mechanisms of GNP radiosensitization, including physical, chemical and biological mechanisms are discussed, which may provide new directions for the optimization and clinical transformation of next-generation GNPs.

Roadmap for metal nanoparticles in radiation therapy: current status, translational challenges, and future directions

This roadmap outlines the potential roles of metallic nanoparticles (MNPs) in the field of radiation therapy. MNPs made up of a wide range of materials (from Titanium, Z = 22, to Bismuth, Z = 83) and a similarly wide spectrum of potential clinical applications, including diagnostic, therapeutic (radiation dose enhancers, hyperthermia inducers, drug delivery vehicles, vaccine adjuvants, photosensitizers, enhancers of immunotherapy) and theranostic (combining both diagnostic and therapeutic), are being fabricated and evaluated. This roadmap covers contributions from experts in these topics summarizing their view of the current status and challenges, as well as expected advancements in technology to address these challenges.

Radiolabeling strategies and pharmacokinetic studies for metal based nanotheranostics

Radiolabeled metal-based nanoparticles (MNPs) have drawn considerable attention in the fields of nuclear medicine and molecular imaging, drug delivery, and radiation therapy, given the fact that they can be potentially used as diagnostic imaging and/or therapeutic agents, or even as theranostic combinations. Here, we present a systematic review on recent advances in the design and synthesis of MNPs with major focuses on their radiolabeling strategies and the determinants of their in vivo pharmacokinetics, and together how their intended applications would be impacted. For clarification, we categorize all reported radiolabeling strategies for MNPs into indirect and direct approaches. While indirect labeling simply refers to the use of bifunctional chelators or prosthetic groups conjugated to MNPs for post-synthesis labeling with radionuclides, we found that many practical direct labeling methodologies have been developed to incorporate radionuclides into the MNP core without using extra reagents, including chemisorption, radiochemical doping, hadronic bombardment, encapsulation, and isotope or cation exchange. From the perspective of practical use, a few relevant examples are presented and discussed in terms of their pros and cons. We further reviewed the determinants of in vivo pharmacokinetic parameters of MNPs, including factors influencing their in vivo absorption, distribution, metabolism, and elimination, and discussed the challenges and opportunities in the development of radiolabeled MNPs for in vivo biomedical applications. Taken together, we believe the cumulative advancement summarized in this review would provide a general guidance in the field for design and synthesis of radiolabeled MNPs towards practical realization of their much desired theranostic capabilities. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > Diagnostic Nanodevices Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Photoimmunotherapy with cetuximab-conjugated gold nanorods reduces drug resistance in triple negative breast cancer spheroids with enhanced infiltration of tumor-associated macrophages

Tumor-associated macrophages (TAM) constitute up to 50-80% of stromal cells in breast cancer (BC), and are correlated with poor prognosis. As epidermal growth factor receptor (EGFR) is overexpressed in 60-80% of patients with triple negative breast cancer (TNBC), photoimmunotherapy (PIT) with cetuximab-targeted gold nanorods (CTX-AuNR) is an attractive therapeutic strategy for TNBC. The 3D cell culture model can mimic drug resistance conferred by the tumor microenvironment and its 3D organization; therefore, TAM and non-TAM embedded TNBC spheroids were constructed to evaluate the therapeutic efficacy of CTX-AuNR plus near infrared (NIR) irradiation. Cytotoxicity, reactive oxygen species (ROS) generation, and protein expression were compared in TNBC (± TAM) spheroids. The IC₅₀ values of doxorubicin (DOX) in TAM-embedded TNBC spheroids were significantly higher than those in TNBC spheroids, demonstrating drug resistance, which could be explained by activation of IL-10/IL-10 receptor/STAT3/Bcl-2 signaling. However, 3D in vitro and in vivo results demonstrated that the efficacy of CTX-AuNR plus NIR irradiation was not significantly different in (± TAM) embedded TNBC cells. By enhancing ROS generation, CTX-AuNR plus NIR irradiation reprogrammed TAM polarization to the M1 anti-tumor phenotype, as indicated by macrophage mannose receptor (MMR) downregulation. Thus, CTX-AuNR plus NIR can serve as a potent PIT strategy for treating EGFR-overexpressing TNBC cells.

Immunoadjuvants for cancer immunotherapy: A review of recent developments

Cancer immunotherapy evolved as a new treatment modality to eradicate tumor cells and has gained in popularity after its successful clinical transition. By activating antigen-presenting cells (APCs), and thus, inducing innate or adaptive immune responses, immunoadjuvants have become promising tools for cancer immunotherapy. Different types of immunoadjuvants such as toll-like receptor (TLR) agonists, exosomes, and metallic and plant-derived immunoadjuvants have been studied for their immunological effects. However, the clinical use of immunoadjuvants is limited by short response rates and various side-effects. The rapid progress made in the development of nanoparticle systems as immunoadjuvant carrier vehicles has provided potential carriers for cancer immunotherapy. In this review article, we describe different types of immunoadjuvants, their limitations, modes of action, and the reasons for their clinical adoption. In addition, we review recent progress made in the nanoparticle-based immunoadjuvant field and on the combined use of nanoparticle-based immunoadjuvants and chemotherapy, phototherapy, radiation therapy, and immune checkpoint inhibitor-based therapy. STATEMENT OF SIGNIFICANCE: Cancer immunotherapy emerged as a new hope for treating malignant tumors. Different types of immunoadjuvants serve as an important tool for cancer immunotherapy by activating an innate or adaptive immune response. Limitation of free immunoadjuvant has paved the path for the development of nanoparticle-based immunoadjuvant therapy with the hope of prolonging the therapeutic efficacy. This review highlights the recent advancement made in nanoparticle-based immunoadjuvant therapy in modulating the adaptive and innate immune system. The application of the combinatorial approach of chemotherapy, phototherapy, radiation therapy adds synergy in nanoparticle-based immunoadjuvant therapy. It will broaden the reader's understanding on the recent progress made in immunotherapy with the aid of immunoadjuvant-based nanosystem.

Emerging technologies for local cancer treatment

The fundamental limitations of systemic therapeutic administration have prompted the development of local drug delivery platforms as a solution to increase effectiveness and reduce side effects. By confining therapeutics to the site of disease, local delivery technologies can enhance therapeutic index. This review highlights recent advances and opportunities in local drug delivery strategies for cancer treatment in addition to challenges that need to be addressed to facilitate clinical translation. The benefits of local cancer treatment combined with technological advancements and increased understanding of the tumor microenvironment, present a prime breakthrough opportunity for safer and more effective therapies.

Opportunities in the Synthesis and Design of Radioactive Thin Films and Nanoparticles

Studies of radioactive isotopes at the liquid-solid or gas-solid interface are enabling a detailed mechanistic understanding of the effects of radioactive decay on physical, biological, and chemical systems. In recent years, there has been a burgeoning interest in using radioactive isotopes for both imaging and therapeutic purposes by attaching them to the surface of colloidal nanoparticles. By merging the field of nanomedicine with the more mature field of internal radiation therapy, researchers are discovering new ways to diagnose and treat cancer. In this Perspective, we discuss state-of-the-art radioactive thin films as applied to both well-defined surfaces and more complex nanoparticles. We highlight the design considerations that are unique to radioactive films, which originate from the damaging and potentially self-destructive emissions produced during radioactive decay, and highlight future opportunities in the largely underexplored area between radioisotope chemistry and nanoscience.

Preclinical evaluation of cationic DOTA-triarginine-lipid conjugates for theranostic liquid brachytherapy

Liquid brachytherapy is an emerging technology for internal radiation therapy where liquids containing radionuclides are administered directly into solid tumors. These technologies are less invasive than conventional brachytherapy, and can potentially improve the dose coverage and homogeneity of the radioactivity distribution within the tumor. For this purpose, we have developed a novel cationic micelle system for delivery of a range of radionuclides. The system is applicable for emitters of alpha, beta or photon radiation, and enables dose-mapping via theranostic nuclear imaging. Methods: The cationic micelles were developed as linear surfactants comprising the chelator DOTA, a triarginine sequence and a palmitoyl or stearoyl fatty acid chain. The critical micelle concentration of the surfactants was determined, and the micelles were radiolabelled with ⁶⁴Cu or ¹⁷⁷Lu in high radiochemical purity (>95%). The tumor retention and biodistribution of the ⁶⁴Cu-radiolabeled surfactants, administered as micelles or formulated in liposomes, were investigated in vivo by PET/CT in a tumor bearing mouse model. Results: The interaction of the micelles with anionic lipid membranes was demonstrated to be favourable, using a liposome partition assay. In vivo, the surfactants formulated both as cationic micelles and liposomes displayed the best intratumoral retention, with micelles providing more homogeneous activity distribution. Conclusion: A cationic, surfactant-based drug delivery system was developed and demonstrated promise as a vehicle for liquid brachytherapy when formulated as micelles or in liposomes. The system enables accurate dosimetry due to the flexible radiochemistry of DOTA.

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.

Dual-Receptor-Targeted (DRT) Radiation Nanomedicine Labeled with 177Lu Is More Potent for Killing Human Breast Cancer Cells That Coexpress HER2 and EGFR Than Single-Receptor-Targeted (SRT) Radiation Nanomedicines

Resistance to HER2-targeted therapies in breast cancer (BC) is associated in some cases with an increased expression of epidermal growth factor receptors (EGFR). We describe a dual-receptor-targeted (DRT) radiation nanomedicine for local intratumoral (i.t.) treatment of BC composed of 15 nm sized gold nanoparticles (AuNPs) modified with trastuzumab (TmAb) to target HER2 and panitumumab (PmAb) to target EGFR. The AuNPs were modified with poly(ethylene glycol) (PEG_3k) linked to 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelators to complex the β-particle emitter, ¹⁷⁷Lu. Our aim was to compare the properties of these DRT-AuNP-¹⁷⁷Lu with single-receptor-targeted (SRT)-TmAb-AuNP-¹⁷⁷Lu or PmAb-AuNP-¹⁷⁷Lu or nontargeted (NT)-AuNP-¹⁷⁷Lu using human BC cells that expressed HER2, EGFR, or both receptors. To construct these radiation nanomedicines, PEG_5K was linked to TmAb or PmAb, while PEG_3k was linked to DOTA. These polymers were conjugated to AuNP via two Au-thiol bonds using a terminal lipoic acid (LA) group on the polymers. NT-AuNP-¹⁷⁷Lu were constructed without modification with TmAb or PmAb. MDA-MB-231-H2N, MDA-MB-468, and BT-474 human BC cells were designated as HER2^mod/EGFR^mod, EGFR^high/HER2^neg, and HER2^high/EGFR^low, respectively, based on the expression of these receptors. Specific binding to HER2 and/or EGFR was assessed by incubating BC cells with DRT-AuNP-¹⁷⁷Lu or TmAb-AuNP-¹⁷⁷Lu or PmAb-AuNP-¹⁷⁷Lu, or NT-AuNP-¹⁷⁷Lu in the absence or presence of an excess of TmAb or PmAb or both competitors. Binding and internalization of AuNP by BC cells were assessed by dark-field microscopy. Cell fractionation studies were conducted to quantify AuNP-¹⁷⁷Lu bound and internalized. The cytotoxicity of DRT-AuNP-¹⁷⁷Lu was determined in clonogenic survival (CS) assays after an exposure of 5 × 10⁵ BC cells to 3 MBq (1.4 × 10¹² AuNP) for 16 h and then seeding and culturing the cells for 7-15 days. CS was compared to exposure to TmAb-AuNP-¹⁷⁷Lu and PmAb-AuNP-¹⁷⁷Lu or NT-AuNP-¹⁷⁷Lu. The absorbed doses to the nucleus in these CS assays were estimated. DRT-AuNP-¹⁷⁷Lu were specifically bound by BC cells that expressed HER2 or EGFR or both receptors. In contrast, SRT-TmAb-AuNP-¹⁷⁷Lu and PmAb-AuNP-¹⁷⁷Lu were bound and internalized only by BC cells that expressed HER2 or EGFR, respectively. NT-AuNP-¹⁷⁷Lu exhibited very low binding to BC cells. DRT-AuNP-¹⁷⁷Lu and SRT-TmAb-AuNP-¹⁷⁷Lu or PmAb-AuNP-¹⁷⁷Lu were internalized by BC cells in accordance with the receptor expression. Importantly, DRT-AuNP-¹⁷⁷Lu were more potent in vitro than PmAb-AuNP-¹⁷⁷Lu for killing MDA-MB-231-H2N cells that coexpress HER2 and EGFR (CS = 18.8 ± 1.0 vs 51.5 ± 10.4%; P = 0.006). Furthermore, DRT-AuNP-¹⁷⁷Lu were more potent for killing BT-474 cells with high HER2 but low EGFR expression than TmAb-AuNP-¹⁷⁷Lu (CS = 8.9 ± 3.3 vs 20.7 ± 2.4%; P = 0.007) or PmAb-AuNP-¹⁷⁷Lu (CS = 63.9 ± 1.7%; P < 0.0001). Even for MDA-MB-468 cells that overexpress EGFR but have negligible HER2, DRT-AuNP-¹⁷⁷Lu were more potent for cell killing than PmAb-AuNP-¹⁷⁷Lu (CS = 3.2 ± 3.0 vs 7.5 ± 1.8%; P = 0.001) or TmAb-AuNP-¹⁷⁷Lu (63.2 ± 3.2%; P = 0.0002). All targeted forms of AuNP-¹⁷⁷Lu were more cytotoxic to BC cells than those of NT-AuNP-¹⁷⁷Lu. High absorbed doses (36-119 Gy) were deposited in the nucleus of BC cells by DRT-AuNP-¹⁷⁷Lu. We conclude that a DRT radiation nanomedicine is more potent for killing BC cells that coexpress HER2 and EGFR than SRT radiation nanomedicines. These results are promising for further evaluation of these DRT-AuNP-¹⁷⁷Lu in vivo for the local radiation treatment of human BC tumors that coexpress HER2 and EGFR in mice following i.t. injection, especially tumors that are resistant to HER2-targeted therapies.

Multifunctional nanomedicines for targeting epidermal growth factor receptor in colorectal cancer

Systemic administration of chemotherapeutics by nanocarriers (NCs) functionalized with targeting agents provides a localized accumulation of drugs in the target tissues and cells. Advanced nanoscaled medicaments can enter into the tumor microenvironment (TME) and overcome the uniquely dysregulated biological settings of TME, including highly pressurized tumor interstitial fluid in an acidic milieu. Such multimodal nanomedicines seem to be one of the most effective treatment modalities against solid tumors such as colorectal cancer (CRC). To progress and invade, cancer cells overexpress various oncogenes and molecular markers such as epidermal growth factor receptors (EGFRs), which can be exploited for targeted delivery of nanoscaled drug delivery systems (DDSs). In fact, to develop effective personalized multimodal nanomedicines, the type of solid tumor and status of the disease in each patient should be taken into consideration. While the development of such multimodal-targeted nanomedicines is largely dependent on the expression level of oncomarkers, the type of NCs and homing/imaging agents play key roles in terms of their efficient applications. In this review, we provide deep insights into the development of EGFR-targeting nanomedicines and discuss various types of nanoscale DDSs (e.g., organic and inorganic nanoparticles) for targeting of the EGFR-positive solid tumors such as CRC.

Trastuzumab Conjugated Superparamagnetic Iron Oxide Nanoparticles Labeled with 225Ac as a Perspective Tool for Combined α-Radioimmunotherapy and Magnetic Hyperthermia of HER2-Positive Breast Cancer

It has been proven and confirmed in numerous repeated tests, that the use of a combination of several therapeutic methods gives much better treatment results than in the case of separate therapies. Particularly promising is the combination of ionizing radiation and magnetic hyperthermia in one drug. To achieve this objective, magnetite nanoparticles have been modified in their core with α emitter ²²⁵Ac, in an amount affecting only slightly their magnetic properties. By 3-phosphonopropionic acid (CEPA) linker nanoparticles were conjugated covalently with trastuzumab (Herceptin^®), a monoclonal antibody that recognizes ovarian and breast cancer cells overexpressing the HER2 receptors. The synthesized bioconjugates were characterized by transmission electron microscopy (TEM), Dynamic Light Scattering (DLS) measurement, thermogravimetric analysis (TGA) and application of ¹³¹I-labeled trastuzumab for quantification of the bound biomolecule. The obtained results show that one ²²⁵Ac@Fe₃O₄-CEPA-trastuzumab bioconjugate contains an average of 8–11 molecules of trastuzumab. The labeled nanoparticles almost quantitatively retain ²²⁵Ac (>98%) in phosphate-buffered saline (PBS) and physiological salt, and more than 90% of ²²¹Fr and ²¹³Bi over 10 days. In human serum after 10 days, the fraction of ²²⁵Ac released from ²²⁵Ac@Fe₃O₄ was still less than 2%, but the retention of ²²¹Fr and ²¹³Bi decreased to 70%. The synthesized ²²⁵Ac@Fe₃O₄-CEPA-trastuzumab bioconjugates have shown a high cytotoxic effect toward SKOV-3 ovarian cancer cells expressing HER2 receptor in-vitro. The in-vivo studies indicate that this bioconjugate exhibits properties suitable for the treatment of cancer cells by intratumoral or post-resection injection. The intravenous injection of the ²²⁵Ac@Fe₃O₄-CEPA-trastuzumab radiobioconjugate is excluded due to its high accumulation in the liver, lungs and spleen. Additionally, the high value of a specific absorption rate (SAR) allows its use in a new very perspective combination of α radionuclide therapy with magnetic hyperthermia.

A Proof-of-Concept Study on the Therapeutic Potential of Au Nanoparticles Radiolabeled with the Alpha-Emitter Actinium-225

Actinium-225 (²²⁵Ac) is receiving increased attention for its application in targeted radionuclide therapy, due to the short range of its emitted alpha particles in conjunction with their high linear energy transfer, which lead to the eradication of tumor cells while sparing neighboring healthy tissue. The objective of our study was the evaluation of a gold nanoparticle radiolabeled with ²²⁵Ac as an injectable radiopharmaceutical form of brachytherapy for local radiation treatment of cancer. Au@TADOTAGA was radiolabeled with ²²⁵Ac at pH 5.6 (30 min at 70 °C), and in vitro stability was evaluated. In vitro cytotoxicity was assessed in U-87 MG cancer cells, and in vivo biodistribution was performed by intravenous and intratumoral administration of [²²⁵Ac]²²⁵Ac-Au@TADOTAGA in U-87 MG tumor-bearing mice. A preliminary study to assess therapeutic efficacy of the intratumorally-injected radio-nanomedicine was performed over a period of 22 days, while the necrotic effect on tumors was evaluated by a histopathology study. We have shown that [²²⁵Ac]²²⁵Ac-Au@TADOTAGA resulted in the retardation of tumor growth after its intratumoral injection in U87MG tumor-bearing mice, even though very low activities were injected per mouse. This gold nanoparticle radiopharmaceutical could be applied as an unconventional brachytherapy in injectable form for local radiation treatment of cancer.

Current outlook on radionuclide delivery systems: from design consideration to translation into clinics

Radiopharmaceuticals have proven to be effective agents, since they can be successfully applied for both diagnostics and therapy. Effective application of relevant radionuclides in pre-clinical and clinical studies depends on the choice of a sufficient delivery platform. Herein, we provide a comprehensive review on the most relevant aspects in radionuclide delivery using the most employed carrier systems, including, (i) monoclonal antibodies and their fragments, (ii) organic and (iii) inorganic nanoparticles, and (iv) microspheres. This review offers an extensive analysis of radionuclide delivery systems, the approaches of their modification and radiolabeling strategies with the further prospects of their implementation in multimodal imaging and disease curing. Finally, the comparative outlook on the carriers and radionuclide choice, as well as on the targeting efficiency of the developed systems is discussed.

MicroSPECT/CT Imaging of Cell-Line and Patient-Derived EGFR-Positive Tumor Xenografts in Mice with Panitumumab Fab Modified with Hexahistidine Peptides To Enable Labeling with 99mTc(I) Tricarbonyl Complex

We aimed to investigate the feasibility of conjugating synthetic hexahistidine peptides (His₆) peptides to panitumumab Fab (PmFab) to enable labeling with [^99mTc(H₂O)₃(CO)₃]⁺ complex and study these radioimmunoconjugates for imaging EGFR-overexpressing tumor xenografts in mice by microSPECT/CT. Fab were reacted with a 10-fold excess of sulfo-SMCC to introduce maleimide functional groups for reaction with the terminal thiol on peptides [CGYGGHHHHHH] that harbored the His₆ motif. Modification of Fab with His₆ peptides was assessed by SDS-PAGE/Western blot, and the number of His₆ peptides introduced was quantified by a radiometric assay incorporating ¹²³I-labeled peptides into the conjugation reaction. Radiolabeling was achieved by incubation of PmFab-His₆ in PBS, pH 7.0, with [^99mTc(H₂O)₃(CO)₃]⁺ in a 1.4 MBq/μg ratio. The complex was prepared by adding [^99mTcO₄]^- to an Isolink kit (Paul Scherrer Institute). Immunoreactivity was assessed in a direct (saturation) binding assay using MDA-MB-468 human triple-negative breast cancer (TNBC) cells. Tumor and normal tissue uptake and imaging properties of ^99mTc-PmFab-His₆ (70 μg; 35-40 MBq) injected i.v. (tail vein) were compared to irrelevant ^99mTc-Fab 3913 in NOD/SCID mice engrafted subcutaneously (s.c.) with EGFR-overexpressing MDA-MB-468 or PANC-1 human pancreatic ductal carcinoma (PDCa) cell-line derived xenografts (CLX) at 4 and 24 h post injection (p.i.). In addition, tumor imaging studies were performed with ^99mTc-PmFab-His₆ in mice with patient-derived tumor xenografts (PDX) of TNBC, PDCa, and head and neck squamous cell carcinoma (HNSCC). Biodistribution studies in nontumor bearing Balb/c mice were performed to project the radiation absorbed doses for imaging studies in humans with ^99mTc-PmFab-His₆. PmFab was derivatized with 0.80 ± 0.03 His₆ peptides. Western blot and SDS-PAGE confirmed the presence of His₆ peptides. ^99mTc-PmFab-His₆ was labeled to high radiochemical purity (≥95%), and the K_d for binding to EGFR on MDA-MB-468 cells was 5.5 ± 0.4 × 10^-8 mol/L. Tumor uptake of ^99mTc-PmFab-His₆ at 24 h p.i. was significantly (P < 0.05) higher than irrelevant ^99mTc-Fab 3913 in mice with MDA-MB-468 tumors (14.9 ± 3.1%ID/g vs 3.0 ± 0.9%ID/g) and in mice with PANC-1 tumors (5.6 ± 0.6 vs 0.5 ± 0.1%ID/g). In mice implanted orthotopically in the pancreas with the same PDCa PDX, tumor uptake at 24 h p.i. was 4.2 ± 0.2%ID/g. Locoregional metastases of these PDCa tumors in the peritoneum exhibited slightly and significantly lower uptake than the primary tumors (3.1 ± 0.3 vs 4.2 ± 0.3%ID/g; P = 0.02). In mice implanted with different TNBC or HNSCC PDX, tumor uptake at 24 h p.i. was variable and ranged from 3.7 to 11.4%ID/g and 3.8-14.5%ID/g, respectively. MicroSPECT/CT visualized all CLX and PDX tumor xenografts at 4 and 24 h p.i. Dosimetry estimates revealed that in humans, the whole body dose from administration of 740-1110 MBq of ^99mTc-PmFab-His₆ would be 2-3 mSv, which is less than for a ^99mTc-medronate bone scan (4 mSv).

Use of an imaging station for rapid colony counting in radiobiology studies

Colony counting by eye is time consuming and subjective. Here comparison between the measurements of proliferative growth inhibition in plates of radiation-treated cells by an imaging station correlated highly significantly with counts determined by eye. This would suggest that an imaging station could be a viable alternative for colony counting for doses over 200KBq.

Review of Therapeutic Applications of Radiolabeled Functional Nanomaterials

In the last two decades, various nanomaterials have attracted increasing attention in medical science owing to their unique physical and chemical characteristics. Incorporating radionuclides into conventionally used nanomaterials can confer useful additional properties compared to the original material. Therefore, various radionuclides have been used to synthesize functional nanomaterials for biomedical applications. In particular, several α- or β-emitter-labeled organic and inorganic nanoparticles have been extensively investigated for efficient and targeted cancer treatment. This article reviews recent progress in cancer therapy using radiolabeled nanomaterials including inorganic, polymeric, and carbon-based materials and liposomes. We first provide an overview of radiolabeling methods for preparing anticancer agents that have been investigated recently in preclinical studies. Next, we discuss the therapeutic applications and effectiveness of α- or β-emitter-incorporated nanomaterials in animal models and the emerging possibilities of these nanomaterials in cancer therapy.

Doxorubicin and Anti-PD-L1 Antibody Conjugated Gold Nanoparticles for Colorectal Cancer Photochemotherapy

Colorectal cancer (CRC) is the third leading cause of cancer-related death worldwide. The prognosis and overall survival of CRC are known to be significantly correlated with the overexpression of PD-L1. Since combination therapies can significantly improve therapeutic efficacy, we constructed doxorubicin (DOX) conjugated and anti-PD-L1 targeting gold nanoparticles (PD-L1-AuNP-DOX) for the targeted chemo-photothermal therapy of CRC. DOX and anti-PD-L1 antibody were conjugated to the α-terminal end group of lipoic acid polyethylene glycol N-hydroxysuccinimide (LA-PEG-NHS) using an amide linkage, and PD-L1-AuNP-DOX was constructed by linking LA-PEG-DOX, LA-PEG-PD-L1, and a short PEG chain on the surface of AuNP using thiol-Au covalent bonds. Physicochemical characterizations and biological studies of PD-L1-AuNP-DOX were performed in the presence of near-infrared (NIR) irradiation (biologic studies were conducted using cellular uptake, apoptosis, and cell cycle assays in CT-26 cells). PD-L1-AuNP-DOX (40.0 ± 3.1 nm) was successfully constructed and facilitated the efficient intracellular uptake of DOX as evidenced by pronounced apoptotic effects (66.0%) in CT-26 cells. PD-L1-AuNP-DOX treatment plus NIR irradiation significantly and synergistically suppressed the in vitro proliferation of CT-26 cells by increasing apoptosis and cell cycle arrest. The study demonstrates that PD-L1-AuNP-DOX in combination with synergistic targeted chemo-photothermal therapy has a considerable potential for the treatment of localized CRC.

Radioimmunotherapy of PANC-1 Human Pancreatic Cancer Xenografts in NRG Mice with Panitumumab Modified with Metal-Chelating Polymers Complexed to 177Lu

Our aim was to evaluate the effectiveness and normal tissue toxicity of radioimmunotherapy (RIT) of s.c. PANC-1 human pancreatic cancer (PnCa) xenografts in NRG mice using anti-EGFR panitumumab linked to metal-chelating polymers (MCPs) that present 13 DOTA chelators to complex the β-emitter, ¹⁷⁷Lu. The clonogenic survival (CS) of PANC-1 cells treated in vitro with panitumumab-MCP-¹⁷⁷Lu (0.3-1.2 MBq) and DNA double-strand breaks (DSBs) in the nucleus of these cells were measured by confocal immunofluorescence microscopy for γ-H2AX. Subcellular distribution of radioactivity for panitumumab-MCP-¹⁷⁷Lu was measured, and absorbed doses to the cell nucleus were calculated. Normal tissue toxicity was assessed in non tumor-bearing NRG mice by monitoring body weight, complete blood cell counts (CBC), serum alanine aminotransferase (ALT), and creatinine (Cr) after i.v. injection of 6 MBq (10 μg) of panitumumab-MCP-¹⁷⁷Lu. RIT was performed in NRG mice with s.c. PANC-1 tumors injected i.v. with 6 MBq (10 μg) of panitumumab-MCP-¹⁷⁷Lu. Control mice received nonspecific human IgG-MCP-¹⁷⁷Lu (6 MBq; 10 μg), unlabeled panitumumab (10 μg), or normal saline. The tumor growth index (TGI) was compared. Tumor and normal organ doses were estimated based on biodistribution studies. Panitumumab-MCP-¹⁷⁷Lu reduced the CS of PANC-1 cells in vitro by 7.7-fold at the highest amount tested (1.2 MBq). Unlabeled panitumumab had no effect on the CS of PANC-1 cells. γ-H2AX foci were increased by 3.8-fold by panitumumab-MCP-¹⁷⁷Lu. Panitumumab-MCP-¹⁷⁷Lu deposited 3.84 Gy in the nucleus of PANC-1 cells. Administration of panitumumab-MCP-¹⁷⁷Lu (6 MBq; 10 μg) to NRG mice caused no change in body weight, CBC, or ALT and only a slight increase in Cr compared to NRG mice treated with normal saline. Panitumumab-MCP-¹⁷⁷Lu strongly inhibited tumor growth in NRG mice (TGI = 2.3 ± 0.2) compared to normal saline-treated mice (TGI = 5.8 ± 0.5; P < 0.01). Unlabeled panitumumab had no effect on tumor growth (TGI = 6.0 ± 1.6; P > 0.05). The absorbed dose of PANC-1 tumors was 12.3 Gy. The highest normal organ doses were absorbed by the pancreas, liver, spleen, and kidneys. We conclude that EGFR-targeted RIT with panitumumab-MCP-¹⁷⁷Lu was able to overcome resistance to panitumumab in KRAS mutant PANC-1 tumors in NRG mice and may be a promising approach to treatment of PnCa in humans.

An overview of nanoscale radionuclides and radiolabeled nanomaterials commonly used for nuclear molecular imaging and therapeutic functions

Recent advances in the field of nanotechnology applications in nuclear medicine offer the promise of better diagnostic and therapeutic options. In recent years, increasing efforts have been focused on developing nanoconstructs that can be used as core platforms for attaching medical radionuclides with different strategies for the purposes of molecular imaging and targeted drug delivery. This review article presents an introduction to some commonly used nanomaterials with zero-dimensional, one-dimensional, two-dimensional, and three-dimensional structures, describes the various methods applied to radiolabeling of nanomaterials, and provides illustrative examples of application of the nanoscale radionuclides or radiolabeled nanocarriers in nuclear nanomedicine. Especially, the passive and active nanotargeting delivery of radionuclides with illustrating examples for tumor imaging and therapy was reviewed and summarized. The accurate and early diagnosis of cancer can lead to increased survival rates for different types of this disease. Although, the conventional single-modality diagnostic methods such as positron emission tomography/single photon emission computed tomography or MRI used for such purposes are powerful means; most of these are limited by sensitivity or resolution. By integrating complementary signal reporters into a single nanoparticulate contrast agent, multimodal molecular imaging can be performed as scalable images with high sensitivity, resolution, and specificity. The advent of radiolabeled nanocarriers or radioisotope-loaded nanomaterials with magnetic, plasmonic, or fluorescent properties has stimulated growing interest in the developing multimodality imaging probes. These new developments in nuclear nanomedicine are expected to introduce a paradigm shift in multimodal molecular imaging and thereby opening up an era of new diagnostic medical imaging agents. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 251-285, 2019.

Gold Nanoparticles in Radiotherapy and Recent Progress in Nanobrachytherapy

Over the last few decades, gold nanoparticles (GNPs) have emerged as "radiosensitizers" in oncology. Radiosensitizers are additives that can enhance the effects of radiation on biological tissues treated with radiotherapy. The interaction of photons with GNPs leads to the emission of low-energy and short-range secondary electrons, which in turn increase the dose deposited in tissues. In this context, GNPs are the subject of intensive theoretical and experimental studies aiming at optimizing the parameters leading to greater dose enhancement and highest therapeutic effect. This review describes the main mechanisms occurring between photons and GNPs that lead to dose enhancement. The outcome of theoretical simulations of the interactions between GNPs and photons is presented. Finally, the findings of the most recent in vivo studies about interactions between GNPs and photon sources (e.g., external beams, brachytherapy sources, and molecules labeled with radioisotopes) are described. The advantages and challenges inherent to each of these approaches are discussed. Future directions, providing new guidelines for the successful translation of GNPs into clinical applications, are also highlighted.

111In-labelled polymeric nanoparticles incorporating a ruthenium-based radiosensitizer for EGFR-targeted combination therapy in oesophageal cancer cells

Radiolabelled, drug-loaded nanoparticles may combine the theranostic properties of radionuclides, the controlled release of chemotherapy and cancer cell targeting. Here, we report the preparation of poly(lactic-co-glycolic acid) (PLGA) nanoparticles surface conjugated to DTPA-hEGF (DTPA = diethylenetriaminepentaacetic acid, hEGF = human epidermal growth factor) and encapsulating the ruthenium-based DNA replication inhibitor and radiosensitizer Ru(phen)2(tpphz)2+ (phen = 1,10-phenanthroline, tpphz = tetrapyridophenazine) Ru1. The functionalized PLGA surface incorporates the metal ion chelator DTPA for radiolabelling and the targeting ligand for EGF receptor (EGFR). Nanoparticles radiolabelled with 111In are taken up preferentially by EGFR-overexpressing oesophageal cancer cells, where they exhibit radiotoxicity through the generation of cellular DNA damage. Moreover, nanoparticle co-delivery of Ru1 alongside 111In results in decreased cell survival compared to single-agent formulations; an effect that occurs through DNA damage enhancement and an additive relationship between 111In and Ru1. Substantially decreased uptake and radiotoxicity of nanoparticles towards normal human fibroblasts and oesophageal cancer cells with normal EGFR levels is observed. This work demonstrates nanoparticle co-delivery of a therapeutic radionuclide plus a ruthenium-based radiosensitizer can achieve combinational and targeted therapeutic effects in cancer cells that overexpress EGFR.

Gas-Stabilizing Gold Nanocones for Acoustically Mediated Drug Delivery

The efficient penetration of drugs into tumors is a major challenge that remains unmet. Reported herein is a strategy to promote extravasation and enhanced penetration using inertial cavitation initiated by focused ultrasound and cone-shaped gold nanoparticles that entrap gas nanobubbles. The cones are capable of initiating inertial cavitation under pressures and frequencies achievable with existing clinical ultrasound systems and of promoting extravasation and delivery of a model large therapeutic molecule in an in vitro tissue mimicking flow phantom, achieving penetration depths in excess of 2 mm. Ease of functionalization and intrinsic imaging capabilities provide gold with significant advantages as a material for biomedical applications. The cones show neither cytotoxicity in Michigan Cancer Foundation (MCF)-7 cells nor hemolytic activity in human blood at clinically relevant concentrations and are found to be colloidally stable for at least 5 d at 37 °C and several months at 4 °C.

Using Atomic Force Microscopy to Predict Tumor Specificity of ICAM1 Antibody-Directed Nanomedicines

Atomic force microscopy (AFM) is a powerful tool to detect in vitro antibody-antigen interactions. To date, however, AFM-measured antibody-antigen interactions have yet to be exploited to predict in vivo tumor specificity of antibody-directed nanomedicines. In this study, we have utilized AFM to directly measure the biomechanical interaction between live triple negative breast cancer (TNBC) cells and an antibody against ICAM1, a recently identified TNBC target. For the first time, we provide proof-of-principle evidence that in vitro TNBC cell-ICAM1 antibody binding force measured by AFM on live cells more precisely correlates with in vivo tumor accumulation and therapeutic efficacy of ICAM1 antibody-directed liposomes than ICAM1 gene and surface protein overexpression levels. These studies demonstrate that live cell-antibody binding force measurements may be used as a novel in vitro metric for predicting the in vivo tumor recognition of antibody-directed nanomedicines.

Panitumumab Modified with Metal-Chelating Polymers (MCP) Complexed to 111In and 177Lu-An EGFR-Targeted Theranostic for Pancreatic Cancer

A metal-chelating polymer (MCP) with a polyglutamide (PGlu) backbone presenting on average 13 DOTA (tetraazacyclododecane-1,4,7,10-tetraacetic acid) chelators for complexing ¹¹¹In or ¹⁷⁷Lu and 10 polyethylene glycol (PEG) chains to minimize liver and spleen uptake was conjugated to antiepidermal growth factor receptor (EGFR) monoclonal antibody (mAb), panitumumab. Because panitumumab-MCP may be dual-labeled with ¹¹¹In and ¹⁷⁷Lu for SPECT, or radioimmunotherapy (RIT) exploiting the Auger electrons or β-particle emissions, respectively, we propose that panitumumab-MCP could be a useful theranostic agent for EGFR-positive PnCa. Bioconjugation was achieved by reaction of a hydrazine nicotinamide (HyNIC) group on the MCP with an aryl aromatic aldehyde introduced into panitumumab by reaction with succinimidyl-4-formylbenzamide (S-4FB). The conjugation reaction was monitored by measurement of the chromophoric bis-aryl hydrazone bond formed (ε_350 nm = 24 500 M^-1 cm^-1) to achieve two MCPs/panitumumab. Labeling of panitumumab-MCP with ¹¹¹In or ¹⁷⁷Lu demonstrated that masses as small as 0.1 μg were labeled to >90% labeling efficiency (L.E.) and a specific activity (SA) of >70 MBq/μg. Panitumumab-DOTA incorporating two DOTA per mAb was labeled with ¹¹¹In or ¹⁷⁷Lu to a maximum SA of 65 MBq/μg and 46 MBq/μg, respectively. Panitumumab-MCP-¹⁷⁷Lu exhibited saturable binding to EGFR-overexpressing MDA-MB-468 human breast cancer cells. The K_d for binding of panitumumab-MCP-¹⁷⁷Lu to EGFR (2.2 ± 0.6 nmol/L) was not significantly different than panitumumab-DOTA-¹⁷⁷Lu (1.0 ± 0.4 nmol/L). ¹¹¹In and ¹⁷⁷Lu were stably complexed to panitumumab-MCP. Panitumumab-MCP-¹¹¹In exhibited similar whole body retention (55-60%) as panitumumab-DOTA-¹¹¹In in NOD-scid mice up to 72 h postinjection (p.i.) and equivalent excretion of radioactivity into the urine and feces. The uptake of panitumumab-MCP-¹¹¹In in most normal tissues in NOD-scid mice with EGFR-positive PANC-1 human pancreatic cancer (PnCa) xenografts at 72 h p.i. was not significantly different than panitumumab-DOTA-¹¹¹In, except for the liver which was 3-fold greater for panitumumab-MCP-¹¹¹In. Tumor uptake of panitumumab-MCP-¹¹¹In (6.9 ± 1.3%ID/g) was not significantly different than panitumumab-DOTA-¹¹In (6.6 ± 3.3%ID/g). Tumor uptake of panitumumab-MCP-¹¹¹In and panitumumab-DOTA-¹¹¹In were reduced by preadministration of excess panitumumab, suggesting EGFR-mediated uptake. Tumor uptake of nonspecific IgG-MCP (5.4 ± 0.3%ID/g) was unexpectedly similar to panitumumab-MCP-¹¹¹In. An increased hydrodynamic radius of IgG when conjugated to an MCP may encourage tumor uptake via the enhanced permeability and retention (EPR) effect. Tumor uptake of panitumumab-DOTA-¹¹¹In was 3.5-fold significantly higher than IgG-DOTA-¹¹¹In. PANC-1 tumors were imaged by microSPECT/CT at 72 h p.i. of panitumumab-MCP-¹¹¹In or panitumumab-DOTA-¹¹¹In. Tumors were not visualized with preadministration of excess panitumumab to block EGFR, or with nonspecific IgG radioimmunoconjugates. We conclude that linking panitumumab to an MCP enabled higher SA labeling with ¹¹¹In and ¹⁷⁷Lu than DOTA-conjugated panitumumab, with preserved EGFR binding in vitro and comparable tumor localization in vivo in mice with s.c. PANC-1 human PnCa xenografts. Normal tissue distribution was similar except for the liver which was higher for the polymer radioimmunoconjugates.

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

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