Zdravka Medarova

In vivo imaging of siRNA delivery and silencing in tumors

With the increased potential of RNA interference (RNAi) as a therapeutic strategy, new noninvasive methods for detection of siRNA delivery and silencing are urgently needed. Here we describe the development of dual-purpose probes for in vivo transfer of siRNA and the simultaneous imaging of its accumulation in tumors by high-resolution magnetic resonance imaging (MRI) and near-infrared in vivo optical imaging (NIRF). These probes consisted of magnetic nanoparticles labeled with a near-infrared dye and covalently linked to siRNA molecules specific for model or therapeutic targets. Additionally, these nanoparticles were modified with a membrane translocation peptide for intracellular delivery. We show the feasibility of in vivo tracking of tumor uptake of these probes by MRI and optical imaging in two separate tumor models. We also used proof-of-principle optical imaging to corroborate the efficiency of the silencing process. These studies represent the first step toward the advancement of siRNA delivery and imaging strategies, essential for cancer therapeutic product development and optimization.

Reversal of Autoimmunity by Boosting Memory-like Autoregulatory T Cells

Blunting autoreactivity without compromising immunity remains an elusive goal in the treatment of autoimmunity. We show that progression to autoimmune diabetes results in the conversion of naive low-avidity autoreactive CD8(+) T cells into memory-like autoregulatory cells that can be expanded in vivo with nanoparticles coated with disease-relevant peptide-major histocompatibility complexes (pMHC-NP). Treatment of NOD mice with monospecific pMHC-NPs expanded cognate autoregulatory T cells, suppressed the recruitment of noncognate specificities, prevented disease in prediabetic mice, and restored normoglycemia in diabetic animals. pMHC-NP therapy was inconsequential in mice engineered to bear an immune system unresponsive to the corresponding epitope, owing to absence of epitope-experienced autoregulatory T cells. pMHC-NP-expanded autoregulatory T cells suppressed local presentation of autoantigens in an interferon-gamma-, indoleamine 2,3-dioxygenase-, and perforin-dependent manner. Nanoparticles coated with human diabetes-relevant pHLA complexes restored normoglycemia in a humanized model of diabetes. These observations expose a paradigm in the pathogenesis of autoimmunity amenable for therapeutic intervention.

In vivo imaging of islet transplantation

Type 1 diabetes mellitus is characterized by the selective destruction of insulin-producing beta cells, which leads to a deficiency in insulin secretion and, as a result, to hyperglycemia. At present, transplantation of pancreatic islets is an emerging and promising clinical modality, which can render individuals with type 1 diabetes insulin independent without increasing the incidence of hypoglycemic events. To monitor transplantation efficiency and graft survival, reliable noninvasive imaging methods are needed. If such methods were introduced into the clinic, essential information could be obtained repeatedly and noninvasively. Here we report on the in vivo detection of transplanted human pancreatic islets using magnetic resonance imaging (MRI) that allowed noninvasive monitoring of islet grafts in diabetic mice in real time. We anticipate that the information obtained in this study would ultimately result in the ability to detect and monitor islet engraftment in humans, which would greatly aid the clinical management of this disease.

Design, Synthesis, and Testing of Difluoroboron-Derivatized Curcumins as Near-Infrared Probes for in Vivo Detection of Amyloid-β Deposits

Amyloid-beta (Abeta) deposits have been identified as key players in the progression of Alzheimers disease (AD). Recent evidence indicates that the deposits probably precede and induce the neuronal atrophy. Therefore, methods that enable monitoring the pathology before clinical symptoms are observed would be beneficial for early AD detection. Here, we report the design, synthesis, and testing of a curcumin-derivatized near-infrared (NIR) probe, CRANAD-2. Upon interacting with Abeta aggregates, CRANAD-2 undergoes a range of changes, which include a 70-fold fluorescence intensity increase, a 90 nm blue shift (from 805 to 715 nm), and a large increase in quantum yield. Moreover, this probe also shows a high affinity for Abeta aggregates (K(d) = 38.0 nM), a reasonable log P value (log P = 3), considerable stability in serum, and a weak interaction with albumin. After intravenous injection of this probe, 19-month-old Tg2576 mice exhibited significantly higher relative signal than that of the control mice over the same period of time. In summary, CRANAD-2 meets all the requirements for a NIR contrast agent for the detection of Abeta plaques both in vitro and in vivo. Our data point toward the feasibility of monitoring the progress of the disease by NIR imaging with CRANAD-2. In addition, we believe that our probe could be potentially used as a tool for drug screening.

In Vivo Targeting of Underglycosylated MUC-1 Tumor Antigen Using a Multimodal Imaging Probe

One of the most difficult challenges of oncology is to improve methods for early tumor detection, which is crucial for the success of cancer therapy and greatly improves the survival rate. Underglycosylated mucin-1 antigen (uMUC-1) is one of the early hallmarks of tumorigenesis and is overexpressed and underglycosylated on almost all human epithelial cell adenocarcinomas as well as in nonepithelial cancer cell lines, as well as in hematological malignancies such as multiple myeloma, and some B-cell non-Hodgkin lymphomas. In this study, we designed, synthesized, and tested a novel multimodal imaging probe specifically recognizing in vivo uMUC-1 antigen in an animal model of human cancer. Furthermore, in vivo magnetic resonance- and near-infrared-imaging experiments on tumor-bearing animals showed specific accumulation of the probe in uMUC-1-positive tumors and virtually no signal in control tumors. We expect that this probe has a potential to greatly aid in screening prospective patients for early cancer detection and in monitoring the efficacy of drug therapy.

In Vivo Imaging of Immune Rejection in Transplanted Pancreatic Islets

As islet transplantation becomes an acceptable clinical modality for restoring normoglycemia in type 1 diabetic patients, there is a crucial need for noninvasive assessment of the fate of the grafts. In spite of the success of the Edmonton Protocol, a significant graft loss occurs due to immunological and nonimmunological events immediately after transplantation. Allogeneic rejection in graft recipients is one of the major reasons for islet death and graft failure. Therefore, monitoring the islet rejection using reliable noninvasive methods would significantly aid in clinical assessment of graft success. We have previously developed a method to detect transplanted islets noninvasively using magnetic resonance imaging (MRI). For this procedure, human pancreatic islets are labeled with an MRI contrast agent that enables their visualization on magnetic resonance images. In our present study, we not only detected labeled human islets in a preclinical intrahepatic model of human islet transplantation in mice but also showed that islet rejection can be monitored noninvasively and repeatedly in real time by MRI. In addition, in this study, we have adapted, for islet cell labeling, a Food and Drug Administration–approved commercially available contrast agent, Feridex, that is used clinically for liver imaging. We believe that this agent, in combination with our preclinical model of islet transplantation, will facilitate the transition of imaging immune rejection to clinical trials.

Image-Guided Breast Tumor Therapy Using a Small Interfering RNA Nanodrug

Iron oxide nanoparticles offer a feasible tool for combined imaging and delivery of small interfering RNA (siRNA) to tumors, stimulating active interest in exploring different imaging and delivery platforms suitable for detection by a variety of modalities. In this study, we describe the synthesis and testing of a tumor-targeted nanodrug (MN-EPPT-siBIRC5) that is designed to specifically shuttle siRNA to human breast tumors. The nanodrug binds the tumor-specific antigen uMUC-1, which is found in >90% of human breast adenocarcinomas. MN-EPPT-siBIRC5 consists of superparamagnetic iron oxide nanoparticles [for magnetic resonance imaging (MRI)], the dye Cy 5.5 (for near-IR optical imaging), peptides (EPPT) that specifically target uMUC-1, and a synthetic siRNA that targets the tumor-specific antiapoptotic gene BIRC5. Nanodrug uptake by human breast adenocarcinoma cells resulted in a significant downregulation of BIRC5. Following i.v. delivery into subcutaneous mouse models of breast cancer, the nanodrug showed a preferential tumor uptake, which could be visualized by MRI and near-IR optical imaging. Furthermore, MRI could be used to quantitatively monitor nanodrug bioavailability in the tumor tissue throughout the course of treatment. Intravenous injection of the agent once a week over 2 weeks resulted in the induction of considerable levels of necrosis and apoptosis in the tumors, translating into a significant decrease in tumor growth rate. Our strategy permits the simultaneous tumor-specific delivery of siRNA to tumors and the imaging of the delivery process. More generally, it illustrates the potential to apply this approach to many human cancer studies, including for basic tumor biology and therapy.

Magnetic Nanoparticles for Cancer Diagnosis and Therapy

ABSTRACTNanotechnology is evolving as a new field that has a potentially high research and clinical impact. Medicine, in particular, could benefit from nanotechnology, due to emerging applications for noninvasive imaging and therapy. One important nanotechnological platform that has shown promise includes the so-called iron oxide nanoparticles. With specific relevance to cancer therapy, iron oxide nanoparticle-based therapy represents an important alternative to conventional chemotherapy, radiation, or surgery. Iron oxide nanoparticles are usually composed of three main components: an iron core, a polymer coating, and functional moieties. The biodegradable iron core can be designed to be superparamagnetic. This is particularly important, if the nanoparticles are to be used as a contrast agent for noninvasive magnetic resonance imaging (MRI). Surrounding the iron core is generally a polymer coating, which not only serves as a protective layer but also is a very important component for transforming nanoparticles into biomedical nanotools for in vivo applications. Finally, different moieties attached to the coating serve as targeting macromolecules, therapeutics payloads, or additional imaging tags. Despite the development of several nanoparticles for biomedical applications, we believe that iron oxide nanoparticles are still the most promising platform that can transform nanotechnology into a conventional medical discipline.

In vivo imaging of tumor response to therapy using a dual-modality imaging strategy

In vivo assessment of the outcome of cancer therapy is hampered by the paucity of imaging probes that target tumors specifically and noninvasively. The importance of such probes increases with the continuous development of chemotherapeutics and the necessity to evaluate their effectiveness in a clinical setting. We have recently reported on a dual‐modality imaging probe specifically targeting the underglycosylated mucin‐1 tumor‐specific antigen (uMUC‐1), which is one of the early hallmarks of tumorigenesis in a wide variety of tumors. This probe consists of crosslinked superparamagnetic iron oxide nanoparticles (CLIO) for MR imaging, modified with Cy5.5 dye (for near infrared optical fluorescence imaging (NIRF)), and has peptides (EPPT), specifically recognizing uMUC‐1, attached to the nanoparticles dextran coat. In the present study, we demonstrated that this probe could not only detect orthotopically implanted preclinical models of adenocarcinomas but could also track tumor response to chemotherapy in vivo in real time. Considering the high cost associated with the development and testing of new cancer therapeutics and the need for accurate, noninvasive assessment of their effectiveness, we believe that the developed probe represents a valuable research tool relevant to clinical discovery.

Noninvasive MRI-SERS imaging in living mice using an innately bimodal nanomaterial.

We report a novel nanomaterial (AuMN-DTTC) that can be used as a bimodal contrast agent for in vivo magnetic resonance imaging (MRI) and Raman spectroscopy. The probe consists of MRI-active superparamagnetic iron oxide nanoparticles, stably complexed with gold nanostructures. The gold component serves as a substrate for a Raman active dye molecule to generate a surface-enhanced Raman scattering (SERS) effect. The synthesized probe produces T2 weighted contrast and can be used as a SERS active material both in silico (in aqueous solution) and in vivo. A quantitative assessment of T2 relaxation times was obtained using multiecho MRI analysis. The T2 relaxation times of AuMN-DTTC and MN (dextran-coated iron oxide nanoparticles) were 29.23 + 1.45 and 31.58 + 1.7 ms, respectively. The SERS signature of AuMN-DTTC revealed peaks at 508, 629, 782, 844, 1080, 1108, 1135, and 1242 cm(-1). Intramuscular administration of the probe resulted in a decrease of the T2 relaxation time of muscle from 33.4 + 2.5 to 20.3 + 2.2 ms. SERS peaks were observed at 508, 629, 782, 844, 1080, 1108, 1135, and 1242 cm(-1), consistent with the in silico results. Our studies illustrate for the first time the design and in vivo application of a contrast agent, whose component modalities include MRI and SERS. The value of this agent lies in its innately bimodal nature and its application in vivo for molecular imaging applications.