Weibo Cai

University of Wisconsin–Madison, Madison, Wisconsin, United States

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Publications (151)772.99 Total impact

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    ABSTRACT: There is a growing demand for long-term in vivo stem cell imaging for assessing cell therapy techniques and guiding therapeutic decisions. This work develops the production of 52Mn and establishes proof of concept for the use of divalent metal transporter 1 (DMT1) as a positron emission tomography (PET) and magnetic resonance imaging (MRI) reporter gene for stem cell tracking in the rat brain. 52Mn was produced via proton irradiation of a natural chromium target. In a comparison of two 52Mn separation methods, solvent-solvent extraction was preferred over ion exchange chromatography because of reduced chromium impurities and higher 52Mn recovery. In vitro uptake of Mn-based PET and MRI contrast agents (52Mn2+ and Mn2+, respectively) was enhanced in DMT1 over-expressing human neural progenitor cells (hNPC-DMT1) compared to wild-type control cells (hNPC-WT). After cell transplantation in the rat striatum, increased uptake of Mn-based contrast agents in grafted hNPC-DMT1 was detected in in vivo manganese-enhanced MRI (MEMRI) and ex vivo PET and autoradiography. These initial studies indicate that this approach holds promise for dual-modality PET/MR tracking of transplanted stem cells in the central nervous system and prompt further investigation into the clinical applicability of this technique.
    Theranostics 01/2015; 5(3):227-239. · 7.81 Impact Factor
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    ABSTRACT: Theranostic nanoparticles hold the potential to revolutionize disease management. Over the last decade, there has been growing interest in the engineering of various kinds of theranostic nanoparticles for simultaneous cancer imaging and therapy in small animals. Efficient targeting of theranostic nanoparticles to the tumor site is critical for both diagnosis and therapy. However, difficulties still exist in the engineering of biocompatible theranostic nanoparticles with highly specific in vivo tumor-targeting capabilities. Here, we discuss the current and prospective status of theranostic nanoparticles that actively target tumors, as well as the challenges that still exist. Copyright © 2014 by the Society of Nuclear Medicine and Molecular Imaging, Inc.
    Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 11/2014;
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    ABSTRACT: Although graphene oxide (GO) has recently been considered as a highly attractive nanomaterial for future cancer imaging and therapy, it is still a major challenge to improve its in vivo tumor active targeting efficiency. Here in this full article, we demonstrated the successful and significantly enhanced in vivo tumor vasculature targeting efficacy of well-functionalized GO nanoconjugates by using vascular endothelial growth factor 121 (VEGF121) as the targeting ligand. As-developed GO nanoconjugate exhibits excellent in vivo stability, specific in vitro and in vivo vascular endothelial growth factor receptor (VEGFR) targeting, significantly enhanced tumor accumulation (>8 %ID/g) as well as high tumor-to-muscle contrast, showing great potential for future tumor targeted imaging and therapy.
    Biomaterials 11/2014; · 8.31 Impact Factor
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    ABSTRACT: Scandium-44 (t½ = 3.9 h) is a relatively new radioisotope of potential interest for use in clinical positron emission tomography (PET). Herein, we report for the first time the room temperature radiolabeling of proteins with 44Sc for in vivo PET imaging. For this purpose, the Fab fragment of Cetuximab, a monoclonal antibody that binds with high affinity to epidermal growth factor receptor (EGFR) was generated and conjugated with N-[(R)-2-Amino-3-(p-isothiocyanato-phenyl) propyl]-trans-(S,S)-cyclohexane-1,2-diamine-N,N,N',N″,N″-pentaacetic acid (CHX-A″-DTPA). The high purity of Cetuximab-Fab was confirmed by SDS-PAGE and mass spectrometry. The potential of the bioconjugate for PET imaging of EGFR expression in human glioblastoma (U87MG) tumor-bearing mice was investigated after 44Sc labeling. PET imaging revealed rapid tumor uptake (maximum uptake of ~12 %ID/g at 4 h post-injection) of 44Sc-CHX-A″-DTPA-Cetuximab-Fab with excellent tumor-to-background ratio, which might allow for same day PET imaging in future clinical studies. Immunofluorescence staining was conducted to correlate tracer uptake in the tumor and normal tissues with EGFR expression. This successful strategy for immunoPET imaging of EGFR expression using 44Sc-CHX-A″-DTPA-Cetuximab-Fab can make clinically translatable advances to select the right population of patients for EGFR-targeted therapy and also monitor the therapeutic efficacy of anti-EGFR treatments.
    Bioconjugate Chemistry 11/2014; · 4.58 Impact Factor
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    ABSTRACT: Vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) signaling cascade plays a critical role in tumor angiogenesis and metastasis and has been correlated with several poorly prognostic cancers such as malignant gliomas. Although a number of anti-VEGFR therapies have been conceived, inefficient drug administration still limits their therapeutic efficacy and raise concerns of potential side effects. In the present work, we propose the use of uniform mesoporous silica nanoparticles (MSNs) for VEGFR targeted positron emission tomography imaging and delivery of the anti-VEGFR drug, i.e. sunitinib, in human glioblastoma (U87MG) bearing murine models. MSNs were synthesized, characterized and modified with the polyethylene glycol, anti-VEGFR ligands VEGF121 and radioisotope 64Cu, followed by extensive in vitro, in vivo and ex vivo studies. Our results demonstrated that significantly higher amount of sunitinib could be delivered to U87MG tumor by targeting VEGFR when compared with the non-targeted counterparts. As developed VEGF121-conjugated MSN could become another attractive nanoplatform for the design of future theranostic nanomedicine.
    ACS Applied Materials & Interfaces 10/2014; · 5.90 Impact Factor
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    ABSTRACT: Intrinsically radiolabeled nanoparticles are an emerging paradigm for nanotechnology and nanomedicine. On page 3825, F. Chen, W. Cai, and co-workers summarize the state-of-the-art techniques for the preparation of intrinsically radiolabeled nanoparticles, with a focus on the formation mechanism, in vivo stability, and multimodality molecular imaging.
    Small 10/2014; 10(19). · 7.82 Impact Factor
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    ABSTRACT: Tremendous resources are being invested all over the world for prevention, diagnosis, and treatment of various types of cancer. Successful cancer management depends on accurate diagnosis of the disease along with precise therapeutic protocol. The conventional systemic drug delivery approaches generally cannot completely remove the competent cancer cells without surpassing the toxicity limits to normal tissues. Therefore, development of efficient drug delivery systems holds prime importance in medicine and healthcare. Also, molecular imaging can play an increasingly important and revolutionizing role in disease management. Synergistic use of molecular imaging and targeted drug delivery approaches provides unique opportunities in a relatively new area called 'image-guided drug delivery' (IGDD). Single-photon emission computed tomography (SPECT) is the most widely used nuclear imaging modality in clinical context and is increasingly being used to guide targeted therapeutics. The innovations in material science have fueled the development of efficient drug carriers based on, polymers, liposomes, micelles, dendrimers, microparticles, nanoparticles, etc. Efficient utilization of these drug carriers along with SPECT imaging technology have the potential to transform patient care by personalizing therapy to the individual patient, lessening the invasiveness of conventional treatment procedures and rapidly monitoring the therapeutic efficacy. SPECT-IGDD is not only effective for treatment of cancer but might also find utility in management of several other diseases. Herein, we provide a concise overview of the latest advances in SPECT-IGDD procedures and discuss the challenges and opportunities for advancement of the field.
    Current drug targets. 09/2014;
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    ABSTRACT: Insulin-like growth factor 1 receptor (IGF1R) plays an important role in proliferation, apoptosis, angiogenesis, and tumor invasion. The expression level of IGF1R is related to resistance to several targeted therapies. The goal of this study was to develop an immunoPET tracer for imaging of IGF1R in prostate cancer. Murine antibodies against human IGF1R were generated in BALB/c mice, which were screened in IGF1R-positive MCF-7 cells using flow cytometry as well as biodistribution studies with multiple 64Cu-labeled antibody clones. The antibody production method we adopted could readily produce milligram quantities of anti-IGF1R antibodies for in vivo studies. One antibody clone (1A2G11) with the highest affinity for IGF1R was selected and conjugated to NOTA for 64Cu-labeling. NOTA-1A2G11 maintained IGF1R specificity/avidity based on flow cytometry. 64Cu-labeling was achieved with good yield (>50%) and high specific activity (> 1 Ci/μmol). Serial PET imaging revealed that uptake of 64Cu-NOTA-1A2G11 was 2.8 ± 0.7, 10.2 ± 2.6, and 9.6 ± 1.7 %ID/g in IGF1R-positive DU-145 tumors at 4, 24, and 48 h post-injection, respectively (n = 3), significantly higher than that in IGF1R-negative LNCaP tumors (< 3%ID/g at each time point) except at 4 h post-injection. Histology studies showed strong correlations between IGF1R expression level in the prostate cancer tumor tissues and tumor uptake of 64Cu-NOTA-1A2G11. Prominent, persistent, and IGF1R-specific uptake of 64Cu-NOTA-1A2G11 in IGF1R-positive prostate tumors holds strong potential for future cancer diagnosis, prognosis, and therapy using this antibody.
    Molecular Pharmaceutics 08/2014; · 4.57 Impact Factor
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    ABSTRACT: Graphene-based nanomaterials have attracted tremendous interest over the last decade due to their unique electronic, optical, mechanical and chemical properties. However, the biomedical applications of these intriguing nanomaterials are still limited due to their suboptimal solubility/biocompatibility, potential toxicity, and difficulties in achieving active tumor targeting, just to name a few. In this review article, we will discuss in detail the important role of surface engineering (i.e. bioconjugation) in improving the in vitro/in vivo stability and enriching the functionality of graphene-based nanomaterials, which can enable single-/multi-modality imaging (e.g. optical imaging, positron emission tomography, magnetic resonance imaging) and therapy (e.g. photothermal therapy, photodynamic therapy, and drug/gene delivery) of cancer. Current challenges and future research directions are also discussed and we believe that graphene-based nanomaterials are attractive nanoplatforms for a broad array of future biomedical applications.
    Bioconjugate Chemistry 08/2014; · 4.58 Impact Factor
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    ABSTRACT: Tremendous advances over the last several decades in positron emission tomography (PET) and single photon emission computed tomography (SPECT) allow for targeted imaging of molecular and cellular events in the living systems. Angiogenesis, a multistep process regulated by the network of different angiogenic factors, has attracted world-wide interests, due to its pivotal role in the formation and progression of different diseases including cancer, cardiovascular diseases (CVD), and inflammation. In this review article, we will summarize the recent progress in PET or SPECT imaging of a wide variety of vascular targets in three major angiogenesis-related diseases: cancer, cardiovascular diseases, and inflammation. Faster drug development and patient stratification for a specific therapy will become possible with the facilitation of PET or SPECT imaging and it will be critical for the maximum benefit of patients.
    Advanced drug delivery reviews. 07/2014;
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    ABSTRACT: The overexpression of integrin αvβ3 has been linked to tumor aggressiveness and metastasis in several cancer types. Because of its high affinity, peptides containing the arginine-glycine-aspartic acid (RGD) motif have been proven valuable vectors for noninvasive imaging of integrin αvβ3 expression and for targeted radionuclide therapy. In this study, we aim to develop a (44)Sc-labeled RGD-based peptide for in vivo positron emission tomography (PET) imaging of integrin αvβ3 expression in a preclinical cancer model. High quality (44)Sc (t1/2, 3.97 h; β(+) branching ratio, 94.3%) was produced inexpensively in a cyclotron, via proton irradiation of natural Ca metal targets, and separated by extraction chromatography. A dimeric cyclic-RGD peptide, (cRGD)2, was conjugated to 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and radiolabeled with (44)Sc in high yield (>90%) and specific activity (7.4 MBq/nmol). Serial PET imaging of mice bearing U87MG tumor xenografts showed elevated (44)Sc-DOTA-(cRGD)2 uptake in the tumor tissue of 3.93 ± 1.19, 3.07 ± 1.17, and 3.00 ± 1.25 %ID/g at 0.5, 2, and 4 h postinjection, respectively (n = 3), which were validated by ex vivo biodistribution experiments. The integrin αvβ3 specificity of the tracer was corroborated, both in vitro and in vivo, by competitive cell binding and receptor blocking assays. These results parallel previously reported studies showing similar tumor targeting and pharmacokinetic profiles for dimeric cRGD peptides labeled with (64)Cu or (68)Ga. Our findings, together with the advantageous radionuclidic properties of (44)Sc, capitalize on the relevance of this isotope as an attractive alternative isotope to more established radiometals for small molecule-based PET imaging, and as imaging surrogate of (47)Sc in theranostic applications.
    Molecular Pharmaceutics 07/2014; · 4.57 Impact Factor
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    ABSTRACT: There is a need for safer and improved methods for non-invasive imaging of the gastrointestinal tract. Modalities based on X-ray radiation, magnetic resonance and ultrasound suffer from limitations with respect to safety, accessibility or lack of adequate contrast. Functional intestinal imaging of dynamic gut processes has not been practical using existing approaches. Here, we report the development of a family of nanoparticles that can withstand the harsh conditions of the stomach and intestine, avoid systemic absorption, and provide good optical contrast for photoacoustic imaging. The hydrophobicity of naphthalocyanine dyes was exploited to generate purified ∼20 nm frozen micelles, which we call nanonaps, with tunable and large near-infrared absorption values (>1,000). Unlike conventional chromophores, nanonaps exhibit non-shifting spectra at ultrahigh optical densities and, following oral administration in mice, passed safely through the gastrointestinal tract. Non-invasive, non-ionizing photoacoustic techniques were used to visualize nanonap intestinal distribution with low background and remarkable resolution, and enabled real-time intestinal functional imaging with ultrasound co-registration. Positron emission tomography following seamless nanonap radiolabelling allowed complementary whole-body imaging.
    Nature Nanotechnology 07/2014; · 31.17 Impact Factor
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    ABSTRACT: Intrinsically germanium-69-labeled super-paramagnetic iron oxide nanoparticles are synthesized via a newly developed, fast and highly specific chelator-free approach. The biodistribution pattern and the feasibility of (69) Ge-SPION@PEG for in vivo dual-modality positron emission tomography/magnetic resonance (PET/MR) imaging and lymph-node mapping are investigated, which represents the first example of the successful utilization of a (69) Ge-based agent for PET/MR imaging.
    Advanced Materials 06/2014; · 14.83 Impact Factor
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    ABSTRACT: Multifunctional mesoporous silica nanoparticles (MSN) with well-integrated multimodality imaging properties have generated increasing research interest in the last decade. However, limited progress has been made in developing MSN-based multimodality imaging agents to image tumors. We describe the successful conjugation of, copper-64 (64Cu, t1/2=12.7 h), 800CW (a near-infrared fluorescence [NIRF] dye) and TRC105 (a human/murine chimeric IgG1 monoclonal antibody) to the surface of MSN via well-developed surface engineering procedures, resulting in a dual-labeled MSN for in vivo targeted positron emission tomography (PET) imaging/NIRF imaging of the tumor vasculature. 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. Dual-labeled MSN is an attractive candidate for future cancer theranostics.
    Molecular Pharmaceutics 06/2014; · 4.57 Impact Factor
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    ABSTRACT: Although chelator-based radiolabeling techniques have been used for decades, concerns about the complexity of coordination chemistry, possible altering of pharmacokinetics of carriers, and potential detachment of radioisotopes during imaging have driven the need for developing a simple yet better technique for future radiolabeling. Here, the emerging concept of intrinsically radiolabeled nanoparticles, which could be synthesized using methods such as hot-plus-cold precursors, specific trapping, cation exchange, and proton beam activation, is introduced. Representative examples of using these multifunctional nanoparticles for multimodality molecular imaging are highlighted together with current challenges and future research directions. Although still in the early stages, design and synthesis of intrinsically radiolabeled nanoparticles has shown attractive potential to offer easier, faster, and more specific radiolabeling possibilities for the next generation of molecular imaging.
    Small 06/2014; · 7.82 Impact Factor
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    ABSTRACT: Positron emission tomography (PET) is an important modality in the field of molecular imaging which is gradually impacting patient care by providing safe, fast and reliable techniques that help to alter the course of patient care by revealing invasive, de-facto procedures to be unnecessary or rendering them obsolete. Also, PET provides a key connection between the molecular mechanisms involved in the pathophysiology of disease and the according targeted therapies. Recently, PET imaging is also gaining ground in the field of drug delivery. Current drug delivery research is focused on developing novel drug delivery systems with emphasis on precise targeting, accurate dose delivery and minimal toxicity in order to achieve maximum therapeutic efficacy. At the intersection between PET imaging and controlled drug delivery, interest has grown in combining both these paradigms into clinically effective formulations. PET image-guided drug delivery has great potential to revolutionize patient care by in vivo assessment of drug biodistribution and accumulation at the target site and real-time monitoring of the therapeutic outcome. The expected end-point of this approach is to provide a fundamental support for the optimization of innovative diagnostic and therapeutic strategies that could contribute to emerging concepts in the field of "personalized medicine". This review focuses on the recent developments in PET image-guided drug delivery and discusses intriguing opportunities for future development. The preclinical data reported to date are quite promising, and it is evident that such strategies in cancer management holds promise for clinically translatable advances that can positively impact the overall diagnostic and therapeutic processes and result in enhanced quality of life for cancer patients.
    Molecular Pharmaceutics 05/2014; · 4.57 Impact Factor
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    ABSTRACT: Ligand-based molecular imaging probes have been designed with high affinity and specificity for monitoring biological process and responses. Single target recognition by traditional probes can limit their applicability for disease detection and therapy as synergistic action between disease mediators and different receptors are often involved in disease progression. Consequently, probes that can recognize multiple targets should demonstrate higher targeting efficacy and specificity than their mono-specific peers. This concept has been validated by multiple bispecific heterodimer-based imaging probes with promising results in several animal models. This review summarizes the design strategies for bispecific peptide and antibody-based heterodimers and their applications in molecular targeting and imaging. The design and application of bispecific heterodimer-conjugated nanomaterials are also discussed.
    Molecular Pharmaceutics 04/2014; · 4.57 Impact Factor
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    ABSTRACT: Brush-shaped amphiphilic block copolymers were conjugated with a monoclonal antibody against CD105 (i.e., TRC105) and a macrocyclic chelator for (64)Cu-labeling to generate multifunctional theranostic unimolecular micelles. The backbone of the brush-shaped amphiphilic block copolymer was poly(2-hydroxyethyl methacrylate) (PHEMA) and the side chains were poly(l-lactide)-poly(ethylene glycol) (PLLA-PEG). The doxorubicin (DOX)-loaded unimolecular micelles showed a pH-dependent drug release profile and a uniform size distribution. A significantly higher cellular uptake of TRC105-conjugated micelles was observed in CD105-positive human umbilical vein endothelial cells (HUVEC) than nontargeted micelles due to CD105-mediated endocytosis. In contrast, similar and extremely low cellular uptake of both targeted and nontargeted micelles was observed in MCF-7 human breast cancer cells (CD105-negative). The difference between the in vivo tumor accumulation of (64)Cu-labeled TRC105-conjugated micelles and that of nontargeted micelles was studied in 4T1 murine breast tumor-bearing mice, by serial positron emission tomography (PET) imaging and validated by biodistribution studies. These multifunctional unimolecular micelles offer pH-responsive drug release, noninvasive PET imaging capability, together with both passive and active tumor-targeting abilities, thus making them a desirable nanoplatform for cancer theranostics.
    ACS Applied Materials & Interfaces 03/2014; · 5.90 Impact Factor

Publication Stats

5k Citations
772.99 Total Impact Points


  • 2008–2014
    • University of Wisconsin–Madison
      • • Department of Radiology
      • • Department of Medical Physics
      • • School of Medicine and Public Health
      Madison, Wisconsin, United States
  • 2011
    • National Institutes of Health
      Maryland, United States
    • University of Wisconsin - Milwaukee
      • Department of Mechanical Engineering
      Milwaukee, WI, United States
  • 2006–2009
    • Stanford Medicine
      • Department of Radiology
      Stanford, California, United States
  • 2005–2008
    • Stanford University
      • • Department of Medicine
      • • Department of Neurosurgery
      • • Department of Radiology
      Stanford, CA, United States