[Show abstract][Hide abstract] ABSTRACT: Early diagnosis remains a task of upmost importance for reducing cancer morbidity and mortality. Successful development of highly specific companion diagnostics targeting aberrant molecular pathways of cancer is needed for sensitive detection, accurate diagnosis, and opportune therapeutic intervention. Herein, we generated a bispecific immunoconjugate [denoted as Bs-F(ab)2] by linking two antibody Fab fragments, an anti-epidermal growth factor receptor (EGFR) Fab and an anti-CD105 Fab, via bioorthogonal "click" ligation of trans-cyclooctene and tetrazine. PET imaging of mice bearing U87MG (EGFR/CD105(+/+)) tumors with (64)Cu-labeled Bs-F(ab)2 revealed a significantly enhanced tumor uptake [42.9 ± 9.5 percentage injected dose per gram (%ID/g); n = 4] and tumor-to-background ratio (tumor/muscle ratio of 120.2 ± 44.4 at 36 h postinjection; n = 4) compared with each monospecific Fab tracer. Thus, we demonstrated that dual targeting of EGFR and CD105 provides a synergistic improvement on both affinity and specificity of (64)Cu-NOTA-Bs-F(ab)2. (64)Cu-NOTA-Bs-F(ab)2 was able to visualize small U87MG tumor nodules (<5 mm in diameter), owing to high tumor uptake (31.4 ± 10.8%ID/g at 36 h postinjection) and a tumor/muscle ratio of 76.4 ± 52.3, which provided excellent sensitivity for early detection. Finally, we successfully confirmed the feasibility of a ZW800-1-labeled Bs-F(ab)2 for near-infrared fluorescence imaging and image-guided surgical resection of U87MG tumors. More importantly, our rationale can be used in the construction of other disease-targeting bispecific antibody fragments for early detection and diagnosis of small malignant lesions.
Proceedings of the National Academy of Sciences 09/2015; DOI:10.1073/pnas.1509667112 · 9.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: (52)Mn (t1/2 =5.59 d, ß+ = 29.6%, Eßave = 0.24 MeV) shows promise in positron emission tomography (PET) and in dual-modality manganese-enhanced magnetic resonance imaging (MEMRI) applications including neural tractography, stem cell tracking, and biological toxicity studies. The extension to bioconjugate application requires high specific activity (52)Mn in a state suitable for macromolecule labeling. To that end a (52)Mn production, purification, and labeling system is presented, and its applicability in preclinical, macromolecule PET is shown using the conjugate (52)Mn-DOTA-TRC105. (52)Mn is produced by 60 µA, 16 MeV proton irradiation of natural chromium metal pressed into a silver disc support. Radiochemical separation proceeds by strong anion exchange chromatography of the dissolved Cr target, employing a semi-organic mobile phase, 97:3 (v:v) ethanol: HCl (11M, aqueous). The method is 62 ± 14% efficient (n=7) in (52)Mn recovery, leading to a separation factor from Cr of (1.6 ± 1.0) x10(6) (n = 4), and an average effective specific activity of 0.8 GBq/µmol (n = 4) in titration against DOTA. (52)Mn-DOTA-TRC105 conjugation and labeling demonstrate the potential for chelation applications. In vivo images acquired using PET/CT in mice bearing 4T1 xenograft tumors are presented. Peak tumor uptake is 18.7 ± 2.7 %ID/g at 24 hours post injection and ex vivo (52)Mn biodistribution validates the in vivo PET data. Free (52)Mn(2+)(as chloride or acetate) is used as a control in additional mice to evaluate the non-targeted biodistribution in the tumor model.
[Show abstract][Hide abstract] ABSTRACT: Traditional chelator-based radio-labeled nanoparticles and positron emission tomography (PET) imaging are playing vital roles in the field of nano-oncology. However, their long-term in vivo integrity and potential mismatch of the biodistribution patterns between nanoparticle and radioisotope are two major concerns for this approach. Here, we present a chelator-free zirconium-89 (89Zr, t1/2=78.4 h) labeling of mesoporous silica nanoparticle (MSN) with significantly enhanced in vivo long-term (>20 Days) stability. Successful radio-labeling and in vivo stability are demonstrated to be highly dependent on both the concentration and location of deprotonated silanol groups (-Si-O-) from two types of silica nanoparticles investigated. This work reports on 89Zr-labeled MSN with detailed labeling mechanism investigation and long-term stability study. With its attractive radio-stability and the simplicity of chelator-free radio-labeling, 89Zr-MSN offers a novel, simple, and accurate way for studying the in vivo long-term fate and PET image-guided drug delivery of MSN in the near future.
[Show abstract][Hide abstract] ABSTRACT: Our goal was to demonstrate that suitably derivatized monomeric RGD peptide-based PET tracers, targeting integrin αvβ3, may offer advantages in image contrast, time for imaging, and low uptake in nontarget tissues.
Two cyclic RGDfK derivatives, (PEG)2-c(RGDfK) and PEG4-SAA4-c(RGDfK), were constructed and conjugated to NOTA for (64)Cu labeling. Their integrin αvβ3-binding properties were determined via a competitive cell binding assay. Mice bearing U87MG tumors were intravenously injected with each of the (64)Cu-labeled peptides, and PET scans were acquired during the first 30 min, and 2 and 4 h after injection. Blocking and ex vivo biodistribution studies were carried out to validate the PET data and confirm the specificity of the tracers.
The IC50 values of NOTA-(PEG)2-c(RGDfK) and NOTA-PEG4-SAA4-c(RGDfK) were 444 ± 41 nM and 288 ± 66 nM, respectively. Dynamic PET data of (64)Cu-NOTA-(PEG)2-c(RGDfK) and (64)Cu-NOTA-PEG4-SAA4-c(RGDfK) showed similar circulation t 1/2 and peak tumor uptake of about 4 %ID/g for both tracers. Due to its marked hydrophilicity, (64)Cu-NOTA-PEG4-SAA4-c(RGDfK) provided faster clearance from tumor and normal tissues yet maintained excellent tumor-to-background ratios. Static PET scans at later time-points corroborated the enhanced excretion of the tracer, especially from abdominal organs. Ex vivo biodistribution and receptor blocking studies confirmed the accuracy of the PET data and the integrin αvβ3-specificity of the peptides.
Our two novel RGD-based radiotracers with optimized pharmacokinetic properties allowed fast, high-contrast PET imaging of tumor-associated integrin αvβ3. These tracers may facilitate the imaging of abdominal malignancies, normally precluded by high background uptake.
European Journal of Nuclear Medicine 05/2015; 42(12). DOI:10.1007/s00259-015-3085-7 · 5.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Exploration of protein function and interaction is critical for discovering links between genomics, proteomics, and disease state; yet the immense complexity of proteomics found in biological systems currently limit our investigational capacities. While affinity and auto-fluorescent tags are widely employed for protein analysis, these methods have limited success as they lack specificity and require multiple fusion tags and genetic constructs. As an alternative approach, the innovative HaloTag protein fusion platform allows for comprehensive analysis of protein function and interaction using a single genetic construct with multiple capabilities. This is accomplished using a simplified process, in which a variable HaloTag ligand binds rapidly to the HaloTag protein (usually linked to the protein of interest) with high affinity and specificity. In this review article, we examine all current applications of the HaloTag technology platform for biomedical applications such as the study of protein isolation and purification, protein function, protein-protein and protein-DNA interactions, biological assays, in vitro cellular imaging, and in vivo molecular imaging. In addition, novel uses of the HaloTag platform are briefly discussed with potential future applications.
[Show abstract][Hide abstract] ABSTRACT: Aptamers are single-stranded oligonucleotides with high affinity and specificity to the target molecules or cells, thus they can serve as an important category of molecular targeting ligand. Since their discovery, aptamers have been rapidly translated into clinical practice. The strong target affinity/selectivity, cost-effectivity, chemical versatility and safety of aptamers are superior to traditional peptides- or proteins-based ligands which make them unique choices for molecular imaging. Therefore, aptamers are considered to be extremely useful to guide various imaging contrast agents to the target tissues or cells for optical, magnetic resonance, nuclear, computed tomography, ultrasound and multimodality imaging. This review aims to provide an overview of aptamers' advantages as targeting ligands and their application in targeted imaging. Further research in synthesis of new types of aptamers and their conjugation with new categories of contrast agents is required to develop clinically translatable aptamer-based imaging agents which will eventually result in improved patient care.
Current topics in medicinal chemistry 04/2015; 15(12). DOI:10.2174/1568026615666150413153400 · 3.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Actively targeted theranostic nanomedicine may be the key for future personalized cancer management. Although numerous types of theranostic nanoparticles have been developed in the last decade for cancer treatment, challenges still exist in the engineering of biocompatible theranostic nanoparticles with highly specific in vivo tumor targeting capabilities. Here, we report the design, synthesis, surface engineering, and in vivo active vasculature targeting of a new category of theranostic nanoparticle for future cancer management. Water-soluble photothermally sensitive copper sulfide nanoparticles were encapsulated in biocompatible mesoporous silica shells, followed by multi-step surface engineering to form the final theranostic nanoparticle. Systematic in vitro targeting, an in vivo long-term toxicity study, photothermal ablation evaluation, in vivo vasculature targeted imaging, and biodistribution and histology studies were performed to fully explore the potential of these as-developed new theranostic nanoparticles.
[Show abstract][Hide abstract] ABSTRACT: Development of multifunctional and well-dispersed hollow mesoporous silica nanoparticles (HMSNs) for tumor vasculature targeted drug delivery and PET imaging.
Amine functionalized HMSNs (150-250 nm) were conjugated with a macrocyclic chelator, (S)-2-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triaceticacid (NOTA), PEGylated and loaded with antiangiogenesis drug, Sunitinib. Cyclo(Arg-Gly-Asp-D-Tyr-Lys) (cRGDyK) peptide was attached to the nanoconjugate and radiolabeled with (64)Cu for PET imaging.
(64)Cu-NOTA-HMSN-PEG-cRGDyK exhibited integrin-specific uptake both in vitro and in vivo. PET results indicated approximately 8% ID/g uptake of targeted nanoconjugates in U87MG tumors, which correlated well with ex vivo and histological analyses. Enhanced tumor-targeted delivery of sunitinib was also observed.
We successfully developed tumor vasculature targeted HMSNs for PET imaging and image-guided drug delivery.
[Show abstract][Hide abstract] ABSTRACT: To date, there is no effective therapy for triple-negative breast cancer (TNBC), which has a dismal clinical outcome. Upregulation of tissue factor (TF) expression leads to increased patient morbidity and mortality in many solid tumor types, including TNBC. Our goal was to employ the Fab fragment of ALT-836, a chimeric anti-human TF mAb, for PET imaging of TNBC, which can be used to guide future TNBC therapy.
ALT-836-Fab was generated by enzymatic papain digestion. SDS-PAGE and FACS studies were performed to evaluate the integrity and TF binding affinity of ALT-836-Fab before NOTA conjugation and (64)Cu-labeling. Serial PET imaging and biodistribution studies were carried out to evaluate the tumor targeting efficacy and pharmacokinetics in the MDA-MB-231 TNBC model, which expresses high levels of TF on the tumor cells. Blocking studies, histological assessment, as well as RT-PCR were performed to confirm TF specificity of (64)Cu-NOTA-ALT-836-Fab.
ALT-836-Fab was produced with high purity, which exhibited superb TF binding affinity and specificity. Serial PET imaging revealed rapid and persistent tumor uptake of (64)Cu-NOTA-ALT-836-Fab (5.1 ± 0.5 %ID/g at 24 h post-injection; n = 4) and high tumor/muscle ratio (7.0 ± 1.2 at 24 h post-injection; n = 4), several-fold higher than that of the blocking group and tumor models that do not express significant level of TF, which was confirmed by biodistribution studies. TF specificity of the tracer was also validated by histology and RT-PCR.
(64)Cu-NOTA-ALT-836-Fab exhibited prominent tissue factor targeting efficiency in MDA-MB-231 TNBC model. The use of a Fab fragment led to fast tumor uptake and good tissue/muscle ratio, which may be translated into same-day immunoPET imaging in the clinical setting to improve TNBC patient management.
European Journal of Nuclear Medicine 03/2015; 42(8). DOI:10.1007/s00259-015-3038-1 · 5.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Positron emission tomography (PET) is a radionuclide imaging technology that plays an important role in preclinical and clinical research. With administration of a small amount of radiotracer, PET imaging can provide a noninvasive, highly sensitive, and quantitative readout of its organ/tissue targeting efficiency and pharmacokinetics. Various radiotracers have been designed to target specific molecular events. Compared with antibodies, proteins, peptides, and other biologically relevant molecules, nanoparticles represent a new frontier in molecular imaging probe design, enabling the attachment of different imaging modalities, targeting ligands, and therapeutic payloads in a single vector.
Accounts of Chemical Research 01/2015; 48(2). DOI:10.1021/ar500362y · 22.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Multifunctional zinc oxide (ZnO) nanoparticles (NPs) with well-integrated multimodality imaging capacities have generated increasing research interest in the last decade. However, limited progress has been made in developing ZnO NP-based multimodality tumor-imaging agents. Here we developed novel red fluorescent ZnO NPs and described the successful conjugation of copper-64 (64Cu, t1/2 = 12.7 h) and TRC105, a human/murine chimeric IgG1 monoclonal antibody, to these ZnO NPs via well-developed surface engineering procedures. The produced dual-modality ZnO NPs were readily applicable for in vivo targeted positron emission tomography (PET) imaging and fluorescence imaging of the tumor vasculature. Their pharmacokinetics and tumor-targeting efficacy/specificity in 4T1 murine breast tumor-bearing mice were thoroughly investigated through various in vitro, in vivo, and ex vivo experiments. We conclude that ZnO NPs with dual-modality imaging properties can serve as an attractive candidate for future cancer theranostics.
[Show abstract][Hide abstract] ABSTRACT: A simple approach is proposed in which a nanoparticulate agent, readily formed from just two active components, can be used to explore imaging parameters in six modalities. Porphyrin-phospholipid- upconversion nanoparticles (PoP-UCNPs) were generated by coating oleic acid-capped UCNPs, synthesized via thermal decomposition, with phospholipids to render them dispersible in aqueous solutions. Thin films containing PoP-UCNPs with varying ratios of PoP to polyethylene glycol (PEG)-lipid were hydrated with water and sonicated to generate stable and dispersed nanoparticles. Transmission electron microscopy and dynamic light scattering of PoP-UCNPs coated with 80 molar% PoP and 20 molar% PEG-lipid revealed an average particle size of 74 nm. At higher resolution, micrographs revealed a crystal lattice spacing of 0.52 nm. Based on their dense self-packing in a spatially constrained bilayer, PoP bilayers give rise to intense intermolecular porphyrin face-to-face contact and FL self-quenching.
[Show abstract][Hide abstract] ABSTRACT: Follicle-stimulating hormone receptor (FSHR) is selectively overexpressed by the vascular endothelium in a wide variety of tumors and confirmed to play critical roles in angiogenesis, tumor invasion, and metastases. The expression level of FSHR correlates strongly with the response of tumors to antiangiogenic therapies. The goal of this study was to develop an immunoPET tracer for imaging of FSHR in different cancer types. A monoclonal antibody (FSHR-mAb) against FSHR was conjugated with S-2-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (p-SCN-Bn-NOTA) and used for 64Cu-labeling. NOTA-FSHR-mAb maintained FSHR specificity/avidity based on flow cytometry. 64Cu-labeling was achieved with decent yields (~ 25%) and high specific activity (0.93 GBq/mg). Serial PET imaging revealed that uptake of 64Cu-NOTA-FSHR-mAb was 3.6 ± 0.8, 13.2 ± 0.7, and 14.6 ± 0.4%ID/g in FSHR-positive CAOV-3 tumors at 4, 24, and 48 h post-injection, respectively (n = 3), significantly higher (p<0.05) than that in FSHR-negative SKOV-3 tumors (2.3 ± 1.2, 8.0 ± 0.9, and 9.1 ± 1.3 %ID/g at 4, 24, and 48 h post-injection, respectively (n = 3)) except at 4 h p.i. FSHR-relevant uptake of 64Cu-NOTA-FSHR-mAb was also readily observed in other tumor types (e.g. triple-negative breast tumor MDA-MB-231 or prostate tumor PC-3). Histology studies showed universal FSHR expression in microvasculature of these four tumor types and also prominent expression in tumor cells of CAOV-3, PC-3, and MDA-MB-231. Strong correlations between FSHR expression level in the tumor tissues and tumor uptake of 64Cu-NOTA-FSHR-mAb were witnessed in this study. Prominent, persistent, and FSHR-specific uptake of 64Cu-NOTA-FSHR mAb in different tumors holds strong potential for future cancer diagnosis, prognosis, and therapy using this antibody and establishes FSHR as a promising clinical target for cancer.
[Show abstract][Hide abstract] ABSTRACT: Theranostics for in vivo cancer diagnosis and treatment generally requires well-designed nanoscale platforms with multiple integrated functionalities. In this study, we uncover that functionalized iron oxide nanoparticles (IONPs) could be self-assembled on the surface of two-dimensional MoS2 nanosheets via sulfur chemistry, forming MoS2-IO nanocomposites which are then modified with dual types of polyethylene glycol (PEG) to acquire enhanced stability in physiological environments. Interestingly, 64Cu, a commonly used positron emitting radioisotope, could be firmly adsorbed on the surface of MoS2 without the need of chelating molecules, to enable in vivo positron emission tomography (PET) imaging. On the other hand, the strong near-infrared (NIR) and superparamagnetism of MoS2-IO-PEG could also be utilized for photoacoustic tomography (PAT) and magnetic resonance (MR) imaging, respectively. Under the guidance by such triple-modal imaging which uncovers efficient tumor retention of MoS2-IO-(d)PEG upon intravenous injection, in vivo photothermal therapy is finally conducted, achieving effective tumor ablation in an animal tumor model. Our study highlights the promise of constructing multifunctional theranostic nanocomposites based on 2D transitional metal dichalcogenides (TMDCs) for multimodal imaging-guided cancer therapy.