Development of multivalent radioimmunonanoparticles for cancer imaging and therapy

Utilization of nanotechnology in targeted radionuclide cancer therapy: monotherapy, combined therapy and radiosensitization

The rapid progress of nanomedicine field has a great influence on the different tumor therapeutic trends. It achieves a potential targeting of the therapeutic agent to the tumor site with neglectable exposure of the normal tissue. In nuclear medicine, nanocarriers have been employed for targeted delivery of therapeutic radioisotopes to the malignant tissues. This systemic radiotherapy is employed to overcome the external radiation therapy drawbacks. This review overviews studies concerned with investigation of different nanoparticles as promising carriers for targeted radiotherapy. It discusses the employment of different nanovehicles for achievement of the synergistic effect of targeted radiotherapy with other tumor therapeutic modalities such as hyperthermia and photodynamic therapy. Radiosensitization utilizing different nanosensitizer loaded nanoparticles has also been discussed briefly as one of the nanomedicine approach in radiotherapy.

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.

Superparamagnetic iron oxide nanoparticulate system: synthesis, targeting, drug delivery and therapy in cancer

Cancer is a global epidemic and is considered a leading cause of death. Various cancer treatments such as chemotherapy, surgery, and radiotherapy are available for the cure but those are generally associated with poor long-term survival rates. Consequently, more advanced and selective methods that have better outcomes, fewer side effects, and high efficacies are highly in demand. Among these is the use of superparamagnetic iron oxide nanoparticles (SPIONs) which act as an innovative kit for battling cancer. Low cost, magnetic properties and toxicity properties enable SPIONs to be widely utilized in biomedical applications. For example, magnetite and maghemite (Fe3O4 and γ-Fe2O3) exhibit superparamagnetic properties and are widely used in drug delivery, diagnosis, and therapy. These materials are termed SPIONs when their size is smaller than 20 nm. This review article aims to provide a brief introduction on SPIONs, focusing on their fundamental magnetism and biological applications. The quality and surface chemistry of SPIONs are crucial in biomedical applications; therefore an in-depth survey of synthetic approaches and surface modifications of SPIONs is provided along with their biological applications such as targeting, site-specific drug delivery and therapy.

Iron oxide nanoparticulate system as a cornerstone in the effective delivery of Tc-99 m radionuclide: a potential molecular imaging probe for tumor diagnosis

BACKGROUND

The evolution of nanoparticles has gained prominence as platforms for developing diagnostic and/or therapeutic radiotracers. This study aims to develop a novel technique for fabricating a tumor diagnostic probe based on iron oxide nanoparticles excluding the utilization of chelating ligands.

METHODS

Tc-99 m radionuclide was loaded into magnetic iron oxide nanoparticles platform (MIONPs) by sonication. ^99mTc-encapsulated MIONPs were fully characterized concerning particles size, charge, radiochemical purity, encapsulation efficiency, in-vitro stability and cytotoxicity. These merits were biologically evaluated in normal and solid tumor bearing mice via different delivery approaches.

RESULTS

^99mTc-encapsulated MIONPs probe was synthesized with average particle size 24.08 ± 7.9 nm, hydrodynamic size 52 nm, zeta potential -28 mV, radiolabeling yield 96 ± 0.83%, high in-vitro physiological stability, and appropriate cytotoxicity behavior. The in-vivo evaluation in solid tumor bearing mice revealed that the maximum tumor radioactivity accumulation (25.39 ± 0.57, 36.40 ± 0.59 and 72.61 ± 0.82%ID/g) was accomplished at 60, 60 and 30 min p.i. for intravenous, intravenous with physical magnet targeting and intratumoral delivery, respectively. The optimum T/NT ratios of 57.70, 65.00 and 87.48 were demonstrated at 60 min post I.V., I.V. with physical magnet targeting and I.T. delivery, respectively. These chemical and biological characteristics of our prepared nano-probe demonstrate highly advanced merits over the previously reported chelator mediated radiolabeled nano-formulations which reported maximum tumor uptakes in the scope of 3.65 ± 0.19 to 16.21 ± 2.56%ID/g.

CONCLUSION

Stabilized encapsulation of ^99mTc radionuclide into MIONPs elucidates a novel strategy for developing an advanced nano-sized radiopharmaceutical for tumor diagnosis. Graphical abstract ^99mTc-encapsulated MIONPs nanosized-radiopharmaceutical as molecular imaging probe for tumor diagnosis.

PET-MR and SPECT-MR multimodality probes: Development and challenges

Positron emission tomography (PET)-magnetic resonance (MR) or single photon emission computed tomography (SPECT)-MR hybrid imaging is being used in daily clinical practice. Due to its advantages over stand-alone PET, SPECT or MR imaging, in many areas such as oncology, the demand for hybrid imaging techniques is increasing dramatically. The use of multimodal imaging probes or biomarkers in a single molecule or particle to characterize the imaging subjects such as disease tissues certainly provides us with more accurate diagnosis and promotes therapeutic accuracy. A limited number of multimodal imaging probes are being used in preclinical and potential clinical investigations. The further development of multimodal PET-MR and SPECT-MR imaging probes includes several key elements: novel synthetic strategies, high sensitivity for accurate quantification and high anatomic resolution, favourable pharmacokinetic profile and target-specific binding of a new probe. This review thoroughly summarizes all recently available and noteworthy PET-MR and SPECT-MR multimodal imaging probes including small molecule bimodal probes, nano-sized bimodal probes, small molecular trimodal probes and nano-sized trimodal probes. To the best of our knowledge, this is the first comprehensive overview of all PET-MR and SPECT-MR multimodal probes. Since the development of multimodal PET-MR and SPECT-MR imaging probes is an emerging research field, a selection of 139 papers were recognized following the literature review. The challenges for designing multimodal probes have also been addressed in order to offer some future research directions for this novel interdisciplinary research field.

Dual nano-sized contrast agents in PET/MRI: a systematic review

Nowadays molecular imaging plays a vital role in achieving a successful targeted and personalized treatment. Hence, the approach of combining two or more medical imaging modalities was developed. The objective of this review is to systematically compare recent dual contrast agents in Positron Emission Tomography (PET)/Magnetic Resonance Imaging (MRI) and in some cases Single photon emission computed tomography (SPECT)/MRI in terms of some their characteristics, such as tumor uptake, and reticuloendothelial system uptake (especially liver) and their relaxivity rates for early detection of primary cancer tumor. To the best of our knowledge, this is the first systematic and integrated overview of this field. Two reviewers individually directed the systematic review search using PubMed, MEDLINE and Google Scholar. Two other reviewers directed quality assessment, using the criteria checklist from the CAMARADES (Collaborative Approach to Meta-Analysis and Review of Animal Data from Experimental Studies) tool, and differences were resolved by consensus. After reviewing all 49 studies, we concluded that a size range of 20-200 nm can be used for molecular imaging, although it is better to try to achieve as small a size as it is possible. Also, small nanoparticles with a hydrophilic coating and positive charge are suitable as a T₂ contrast agent. According to our selected data, the most successful dual probes in terms of high targeting were with an average size of 40 nm, PEGylated using peptides as a biomarker and radiolabeled with copper 64 and gallium 68. Copyright © 2017 John Wiley & Sons, Ltd.

Forming next-generation antibody-nanoparticle conjugates through the oriented installation of non-engineered antibody fragments

Enabling oriented installation of non-engineered antibody fragments on nanoparticle surfaces to create next-generation antibody–nanoparticle conjugates.

The successful development of targeted nanotherapeutics is contingent upon the conjugation of therapeutic nanoparticles to target-specific ligands, with particular emphasis being placed on antibody-based ligands. Thus, new methods that enable the covalent and precise installation of targeting antibodies to nanoparticle surfaces are greatly desired, especially those which do not rely on costly and time-consuming antibody engineering techniques. Herein we present a novel method for the highly controlled and oriented covalent conjugation of non-engineered antibody F(ab) fragments to PLGA–PEG nanoparticles using disulfide-selective pyridazinedione linkers and strain-promoted alkyne–azide click chemistry. Exemplification of this method with trastuzumab and cetuximab showed significant improvements in both conjugation efficiency and antigen binding capability, when compared to commonly employed strategies for antibody–nanoparticle construction. This new approach paves the way for the development of antibody-targeted nanomedicines with improved paratope availability, reproducibility and uniformity to enhance both biological activity and ease of manufacture.

Nanoparticles as Theranostic Vehicles in Experimental and Clinical Applications-Focus on Prostate and Breast Cancer

Prostate and breast cancer are the second most and most commonly diagnosed cancer in men and women worldwide, respectively. The American Cancer Society estimates that during 2016 in the USA around 430,000 individuals were diagnosed with one of these two types of cancers, and approximately 15% of them will die from the disease. In Europe, the rate of incidences and deaths are similar to those in the USA. Several different more or less successful diagnostic and therapeutic approaches have been developed and evaluated in order to tackle this issue and thereby decrease the death rates. By using nanoparticles as vehicles carrying both diagnostic and therapeutic molecular entities, individualized targeted theranostic nanomedicine has emerged as a promising option to increase the sensitivity and the specificity during diagnosis, as well as the likelihood of survival or prolonged survival after therapy. This article presents and discusses important and promising different kinds of nanoparticles, as well as imaging and therapy options, suitable for theranostic applications. The presentation of different nanoparticles and theranostic applications is quite general, but there is a special focus on prostate cancer. Some references and aspects regarding breast cancer are however also presented and discussed. Finally, the prostate cancer case is presented in more detail regarding diagnosis, staging, recurrence, metastases, and treatment options available today, followed by possible ways to move forward applying theranostics for both prostate and breast cancer based on promising experiments performed until today.

Antibody fragments as nanoparticle targeting ligands: a step in the right direction

Recent advances in nanomedicine have shown that dramatic improvements in nanoparticle therapeutics and diagnostics can be achieved through the use of disease specific targeting ligands. Although immunoglobulins have successfully been employed for the generation of actively targeted nanoparticles, their use is often hampered by the suboptimal characteristics of the resulting complexes. Emerging data suggest that a switch in focus from full antibodies to antibody derived fragments could help to alleviate these problems and expand the potential of antibody-nanoparticle conjugates as biomedical tools. This review aims to highlight how antibody derived fragments have been utilised to overcome both fundamental and practical issues encountered during the design and application of antibody-targeted nanoparticles.

Intracellular Photodynamic Activity of Chlorin e6 Containing Nanoparticles

Nanoparticles (NPs) containing the photo-therapeutic dye Chlorin e6 (Ce6) have been explored in multiple studies for photo-dynamic therapy (PDT). However, little work has been carried out regarding their PDT efficacy, relative to other dye containing NPs. Here polyacrylamide nanoparticles (PAAm NPs) containing Ce6 were prepared and their PDT efficacy compared to previously reported methylene blue (MB) containing PAAmNPs. It was found that, for identical NP dosages and photon doses, the Ce6 NPs are an order of magnitude more potent in killing cancer cells.

High specificity targeting and detection of human neuroblastoma using multifunctional anti-GD2 iron-oxide nanoparticles

AIM

To develop biocompatible, tumor-specific multifunctional iron-oxide nanoconstructs targeting neuroblastoma, an aggressive pediatric malignancy.

MATERIALS & METHODS

Clinical-grade humanized monoclonal antibody (hu14.18K322A), designed to target GD2 antigen on neuroblastoma with reduced nonspecific immune interactions, was conjugated to hydroxyethyl starch-coated iron-oxide nanoparticles. Targeting capability in vitro and in vivo was assessed by immunofluorescence, electron microscopy, analytical spectrophotometry, histochemistry and magnetic resonance R2* relaxometry.

RESULTS

The biocompatible nanoconstructs demonstrated high tumor specificity in vitro and in vivo, and low background uptake in a mouse flank xenograft model. Specific accumulation in tumors enabled particle visualization and quantification by magnetic resonance R2* mapping.

CONCLUSION

Our findings support the further development toward clinical application of this anti-GD2 iron-oxide nanoconstruct as diagnostic and therapeutic scaffold for neuroblastoma and potentially other GD2-positive malignancies.

Intracystic concentrations of tumour markers for the diagnosis of cystic liver lesions

BACKGROUND

Imaging occasionally fails to differentiate hepatic simple cysts from malignant or premalignant mucinous cystic lesions such as biliary cystadenomas. Hepatic simple cysts can be treated conservatively, whereas malignant or premalignant cysts require complete resection. This study assessed the ability of intracystic tumour marker concentrations to differentiate these disease entities.

METHODS

Intracystic fluid was sampled in patients undergoing partial or complete resection of a cystic lesion of the liver. The indication for surgery in hepatic simple cysts was symptoms or suspicion of a biliary cystadenoma. Intracystic concentrations of carcinoembryonic antigen (CEA), carbohydrate antigen (CA) 19-9 and tumour-associated glycoprotein (TAG) 72 were measured to assess the diagnostic accuracy of these tumour markers. Cut-off values were defined by receiver operating characteristic (ROC) curves.

RESULTS

The study population comprised 118 patients (94 women) with a median age of 59 years. There were 75 patients with hepatic simple cysts, 27 with mucinous cysts (19 biliary cystadenomas, 4 biliary cystadenocarcinomas, 4 intraductal papillary mucinous neoplasms of the bile duct) and 16 with miscellaneous cysts. Unlike CEA and CA19-9, a TAG-72 concentration of more than 25 units/ml differentiated hepatic simple cysts from mucinous cysts with a sensitivity and a specificity of 0·79 and 0·97 respectively. The area under the ROC curve was 0·98 for mucinous versus hepatic simple cysts.

CONCLUSION

The concentration of TAG-72 in cyst fluid accurately identified hepatic cysts that required complete resection.

Superparamagnetic iron oxide nanoparticle 'theranostics' for multimodality tumor imaging, gene delivery, targeted drug and prodrug delivery

The superparamagnetic iron oxide nanoparticle (SPIO) 'theranostics', which contain imaging probes for tumor diagnosis and therapeutic compounds for therapy in a single nanoparticle, might provide significant benefits compared with exiting tumor imaging and therapeutic strategies. In this review, we summarize the progress of SPIO 'theranostics' that integrate tumor targeting, multimodality imaging, and gene delivery or targeted drug and prodrug delivery. This review describes various methods of SPIO synthesis, surface coating and characterization. Different tumor-targeting strategies, such as antibody fragments, nucleotides and receptor ligands, are discussed to improve SPIO delivery for multimodality imaging. We also examine the utility of SPIOs for gene delivery, siRNA delivery and imaging. Several methods for drug encapsulation and conjugation onto SPIOs are compared for targeted drug delivery, site-specific release and imaging-guided drug delivery. Finally, we also review the pharmacokinetics (including biodistribution) of SPIOs based on their characteristics.

Nanomedicine: towards development of patient-friendly drug-delivery systems for oncological applications

The focus on nanotechnology in cancer treatment and diagnosis has intensified due to the serious side effects caused by anticancer agents as a result of their cytotoxic actions on normal cells. This nonspecific action of chemotherapy has awakened a need for formulations capable of definitive targeting with enhanced tumor-killing. Nanooncology, the application of nanobiotechnology to the management of cancer, is currently the most important area of nanomedicine. Currently several nanomaterial-based drug-delivery systems are in vogue and several others are in various stages of development. Tumor-targeted drug-delivery systems are envisioned as magic bullets for cancer therapy and several groups are working globally for development of robust systems.

Can we accurately quantify nanoparticle associated proteins when constructing high-affinity MRI molecular imaging probes?

Targeted magnetic resonance contrast agents (e.g. iron oxide nanoparticles) have the potential to become highly selective imaging tools. In this context, quantification of the coupled amount of protein is essential for the design of antibody- or antibody fragment-conjugated nanoparticles. Nevertheless, the presence of magnetic iron oxide nanoparticles is still an unsolved problem for this task. The aim of the present work was to clarify whether proteins can be reliably quantified directly in the presence of magnetic iron oxide nanoparticles without the use of fluorescence or radioactivity. Protein quantification via Bradford was not influenced by the presence of magnetic iron oxide nanoparticles (0-17.2 mmol Fe l(-1) ). Instead, bicinchoninic acid based assay was, indeed, distinctly affected by the presence of nanoparticle-iron in suspension (0.1-17.2 mmol Fe l(-1) ), although the influence was linear. This observation allowed for adequate mathematical corrections with known iron content of a given nanoparticle. The applicability of our approach was demonstrated by the determination of bovine serum albumin (BSA) content coupled to dextrane-coated magnetic nanoparticles, which was found with the QuantiPro Bicinchoninic acid assay to be of 1.5 ± 0.2 µg BSA per 1 mg nanoparticle. Both Bradford and bicinchoninic acid assay protein assays allow for direct quantification of proteins in the presence of iron oxide containing magnetic nanoparticles, without the need for the introduction of radioactivity or fluorescence modules. Thus in future it should be possible to make more precise estimations about the coupled protein amount in high-affinity targeted MRI probes for the identification of specific molecules in living organisms, an aspect which is lacking in corresponding works published so far. Additionally, the present protein coupling procedures can be drastically improved by our proposed protein quantification method.

Utilization of monoclonal antibody-targeted nanomaterials in the treatment of cancer

Due to their excellent specificity for a single epitope, monoclonal antibodies (mAbs) present a means of influencing the function of cells at the molecular level. In particular they show great promise in the treatment of cancer because they can inhibit cancer cell proliferation, tumor angiogenesis, invasiveness and malignant spread of cancerous cells. Many mAbs are in various stages of testing and 11 are currently marketed in the US or Europe for the treatment of cancers that express particular antigens such as human epidermal growth factor receptor-2, CD20, epidermal growth factor receptor and vascular endothelial growth factor. Strategies to conjugate mAbs to toxins, radioactive isotopes and chemotherapeutic drugs to improve efficacy are under intense investigation and numerous immunoconjugates have been studied in the clinical setting. However, the molecules have limitations, and so nanomaterials (NMs), which potentially offer more flexibility of design and functionality in providing platforms for binding of multiple therapeutic agents in a single structure, are being examined as an alternative. Studies utilizing mAb-targeted NMs have shown that they exhibit focused targeting, improved pharmacokinetics and improved "passive" drug delivery via leaky vasculature. Nevertheless, before they can be utilized to treat cancer, potential NM toxicity must be thoroughly investigated. Thus, rigorous testing of NM-mAb conjugates in both in vitro and in vivo systems is underway to determine how NM-mAb conjugates will interact with cells and tissues of the body. In this review, we discuss the broad range of nanomaterials that are under investigation as potential platforms for the presentation of mAbs either as single therapeutics or in combination with other drugs and their advantages and limitations in specifically targeting cancer.

Stabilization and functionalization of iron oxide nanoparticles for biomedical applications

Superparamagnetic iron oxide nanoparticles (NPs) are used in a rapidly expanding number of research and practical applications in the biomedical field, including magnetic cell labeling separation and tracking, for therapeutic purposes in hyperthermia and drug delivery, and for diagnostic purposes, e.g., as contrast agents for magnetic resonance imaging. These applications require good NP stability at physiological conditions, close control over NP size and controlled surface presentation of functionalities. This review is focused on different aspects of the stability of superparamagnetic iron oxide NPs, from its practical definition to its implementation by molecular design of the dispersant shell around the iron oxide core and further on to its influence on the magnetic properties of the superparamagnetic iron oxide NPs. Special attention is given to the selection of molecular anchors for the dispersant shell, because of their importance to ensure colloidal and functional stability of sterically stabilized superparamagnetic iron oxide NPs. We further detail how dispersants have been optimized to gain close control over iron oxide NP stability, size and functionalities by independently considering the influences of anchors and the attached sterically repulsive polymer brushes. A critical evaluation of different strategies to stabilize and functionalize core-shell superparamagnetic iron oxide NPs as well as a brief introduction to characterization methods to compare those strategies is given.

Delivery of therapeutic radioisotopes using nanoparticle platforms: potential benefit in systemic radiation therapy

Radiation therapy is an effective cancer treatment option in conjunction with chemotherapy and surgery. Emerging individualized internal and systemic radiation treatment promises significant improvement in efficacy and reduction of normal tissue damage; however, it requires cancer cell targeting platforms for efficient delivery of radiation sources. With recent advances in nanoscience and nanotechnology, there is great interest in developing nanomaterials as multifunctional carriers to deliver therapeutic radioisotopes for tumor targeted radiation therapy, to monitor their delivery and tumor response to the treatment. This paper provides an overview on developing nanoparticles for carrying and delivering therapeutic radioisotopes for systemic radiation treatment. Topics discussed in the review include: selecting nanoparticles and radiotherapy isotopes, strategies for targeting nanoparticles to cancers, together with challenges and potential solutions for the in vivo delivery of nanoparticles. Some examples of using nanoparticle platforms for the delivery of therapeutic radioisotopes in preclinical studies of cancer treatment are also presented.

Antibody vectors for imaging

Noninvasive molecular imaging approaches include nuclear, optical, magnetic resonance imaging, computed tomography, ultrasound, and photoacoustic imaging, which require accumulation of a signal delivered by a probe at the target site. Monoclonal antibodies are high affinity molecules that can be used for specific, high signal delivery to cell surface molecules. However, their long circulation time in blood makes them unsuitable as imaging probes. Efforts to improve antibodies pharmacokinetics without compromising affinity and specificity have been made through protein engineering. Antibody variants that differ in antigen binding sites and size have been generated and evaluated as imaging probes to target tissues of interest. Fast clearing fragments, such as single-chain variable fragment (scFv; 25 kDa), with 1 antigen-binding site (monovalent) demonstrated low accumulation in tumors because of the low exposure time to the target. Using scFv as building block to produce larger, bivalent fragments, such as scFv dimers (diabodies, 50 kDa) and scFv-fusion proteins (80 kDa minibodies and 105 kDa scFv-Fc), resulted in higher tumor accumulation because of their longer residence time in blood. Imaging studies with these fragments after radiolabeling have demonstrated excellent, high-contrast images in gamma cameras and positron emission tomography scanners. Several studies have also investigated antibody fragments conjugated to fluorescence (near infrared dyes), bioluminescence (luciferases), and quantum dots for optical imaging and iron oxides nanoparticles for magnetic resonance imaging. However, these studies indicate that there are several factors that influence successful targeting and imaging. These include stability of the antibody fragment, the labeling chemistry (direct or indirect), whether critical residues are modified, the number of antigen expressed on the cell, and whether the target has a rapid recycling rate or internalizes upon binding. The preclinical data presented are compelling, and it is evident that antibody-based molecular imaging tracers will play an important future role in the diagnosis and management of cancer and other diseases.

Design and fabrication of magnetic nanoparticles for targeted drug delivery and imaging

Magnetic nanoparticles (MNPs) represent a class of non-invasive imaging agents that have been developed for magnetic resonance (MR) imaging. These MNPs have traditionally been used for disease imaging via passive targeting, but recent advances have opened the door to cellular-specific targeting, drug delivery, and multi-modal imaging by these nanoparticles. As more elaborate MNPs are envisioned, adherence to proper design criteria (e.g. size, coating, molecular functionalization) becomes even more essential. This review summarizes the design parameters that affect MNP performance in vivo, including the physicochemical properties and nanoparticle surface modifications, such as MNP coating and targeting ligand functionalizations that can enhance MNP management of biological barriers. A careful review of the chemistries used to modify the surfaces of MNPs is also given, with attention paid to optimizing the activity of bound ligands while maintaining favorable physicochemical properties.

Molecular imaging and therapy of cancer with radiolabeled nanoparticles

This review summarizes the current state-of-the-art of radiolabeled nanoparticles for molecular imaging and internal radiotherapy applications targeting cancer. With the capacity to provide enormous flexibility, radiolabeled nanoparticles have the potential to profoundly impact disease diagnosis and patient management in the near future. Currently, the major challenges facing the research on radiolabeled nanoparticles are desirable (tumor) targeting efficacy, robust chemistry for both radionuclide encapsulation/incorporation and targeting ligand conjugation, favorable safety profile, as well as certain commercial and regulatory hurdles.

Bifunctional phage-based pretargeted imaging of human prostate carcinoma

INTRODUCTION

Two-step and three-step pretargeting systems utilizing biotinylated prostate tumor-homing bacteriophage (phage) and (111)In-radiolabeled streptavidin or biotin were developed for use in cancer radioimaging. The in vivo selected prostate carcinoma-specific phage (G1) displaying up to five copies of the peptide IAGLATPGWSHWLAL was the focus of the present study.

METHODS

The ability of G1 phage to extravasate and target prostate tumor cells was investigated using immunohistochemistry. G1 phages were biotinylated, streptavidin was conjugated to diethylenetriaminepentaacetic acid (DTPA) and biotin was conjugated to 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA). Biodistribution studies and single-photon emission computed tomography (SPECT)/CT imaging of xenografted PC-3 tumors via two-step pretargeted (111)In-labeled streptavidin and three-step pretargeted (111)In-labeled biotin were performed in SCID mice to determine the optimal pretargeting method.

RESULTS

The ability of G1 phage to extravasate the vasculature and bind directly to human PC-3 prostate carcinoma tumor cells in vivo was demonstrated via immunocytochemical analysis. Comparative biodistribution studies of the two-step and three-step pretargeting strategies indicated increased PC-3 human prostate carcinoma tumor uptake in SCID mice of 4.34+/-0.26 %ID g(-1) at 0.5 h postinjection of (111)In-radiolabeled biotin (utilized in a three-step protocol) compared to 0.67+/-0.06 %ID g(-1) at 24 h postinjection of (111)In radiolabeled streptavidin (employed in a two-step protocol). In vivo SPECT/CT imaging of xenografted PC-3 tumors in SCID mice with the three-step pretargeting method was superior to that of the two-step pretargeting method, and, importantly, blocking studies demonstrated specificity of tumor uptake of (111)In-labeled biotin in the three-step pretargeting scheme.

CONCLUSION

This study demonstrates the use of multivalent bifunctional phage in a three-step pretargeting system for prostate cancer radioimaging.

Zebrafish as a correlative and predictive model for assessing biomaterial nanotoxicity

The lack of correlative and predictive models to assess acute and chronic toxicities limits the rapid pre-clinical development of new therapeutics. This barrier is due in part to the exponential growth of nanotechnology and nanotherapeutics, coupled with the lack of rigorous and robust screening assays and putative standards. It is a fairly simple and cost-effective process to initially screen the toxicity of a nanomaterial by using invitro cell cultures; unfortunately it is nearly impossible to imitate a complimentary invivo system. Small mammalian models are the most common method used to assess possible toxicities and biodistribution of nanomaterials in humans. Alternatively, Daniorerio, commonly known as zebrafish, are proving to be a quick, cheap, and facile model to conservatively assess toxicity of nanomaterials.

Applications of single-chain variable fragment antibodies in therapeutics and diagnostics

Antibodies (Abs) are some of the most powerful tools in therapy and diagnostics and are currently one of the fastest growing classes of therapeutic molecules. Recombinant antibody (rAb) fragments are becoming popular therapeutic alternatives to full length monoclonal Abs since they are smaller, possess different properties that are advantageous in certain medical applications, can be produced more economically and are easily amendable to genetic manipulation. Single-chain variable fragment (scFv) Abs are one of the most popular rAb format as they have been engineered into larger, multivalent, bi-specific and conjugated forms for many clinical applications. This review will show the tremendous versatility and importance of scFv fragments as they provide the basic antigen binding unit for a multitude of engineered Abs for use as human therapeutics and diagnostics.

NanoFerrite particle based radioimmunonanoparticles: binding affinity and in vivo pharmacokinetics

Dextran and PEG-coated iron oxide nanoparticles (NP), when suitably modified to enable conjugation with molecular targeting agents, provide opportunities to target cancer cells. Monoclonal antibodies, scFv, and peptides conjugated to 20 nm NP have been reported to target cancer for imaging and alternating magnetic field (AMF) therapy. The physical characteristics of NPs can affect their in vivo performance. Surface morphology, surface charge density, and particle size are considered important factors that determine pharmacokinetics, toxicity, and biodistribution. New NanoFerrite (NF) particles having improved specific AMF absorption rates and diameters of 30 and 100 nm were studied to evaluate the variation in their in vitro and in vivo characteristics in comparison to the previously studied 20 nm superparamagnetic iron oxide (SPIO) NP. SPIO NP 20 nm and NF NP 30 and 100 nm were conjugated to (111)In-DOTA-ChL6, a radioimmunoconjugate. Radioimmunoconjugates were conjugated to NPs using 25 microg of RIC/mg of NP by carbodiimide chemistry. The radioimmunonanoparticles (RINP) were purified and characterized by PAGE, cellulose acetate electrophoresis (CAE), live cell binding assays, and pharmacokinetics in athymic mice bearing human breast cancer (HBT 3477) xenografts. RINP (2.2 mg) were injected iv and whole body; blood and tissue data were collected at 4, 24, and 48 h. The preparations used for animal study were >90% monomeric by PAGE and CAE. The immunoreactivity of the RINP was 40-60% compared to (111)In-ChL6. Specific activities of the doses were 20-25 microCi/2.2 mg and 6-11 microg of mAb/2.2 mg of NP. Mean tumor uptakes (% ID/g +/- SD) of each SPIO 20 nm, NF 30 nm, and 100 nm RINP at 48 h were 9.00 +/- 0.8 (20 nm), 3.0 +/- 0.3 (30 nm), and 4.5 +/- 0.8 (100 nm), respectively; the ranges of tissue uptakes were liver (16-32 +/- 1-8), kidney (7.0-15 +/- 1), spleen (8-17 +/- 3-8), lymph nodes 5-6 +/- 1-2), and lung (2.0-4 +/- 0.1-2). In conclusion, this study demonstrated that 100 nm NF NP could be conjugated to (111)In-mAb so that the resulting RINP had characteristics suitable for AMF therapy. Although 100 nm RINP targeted tumor less than 20 nm SPIO RINP, their heating capacity is typically 6 times greater, suggesting the 100 nm NF RINP could still deliver better therapy with AMF.