Multiparametric monitoring of tumor response to chemotherapy by noninvasive imaging

Optical imaging and magnetic field targeting of magnetic nanoparticles in tumors

To address efficacy issues of cancer diagnosis and chemotherapy, we have developed a magnetic nanoparticle (MNP) formulation with combined drug delivery and imaging properties that can potentially be used in image-guided drug therapy. Our MNP consists of an iron-oxide magnetic core coated with oleic acid (OA) and stabilized with an amphiphilic block copolymer. Previously, we reported that our MNP formulation can provide prolonged contrast for tumor magnetic resonance imaging and can be loaded with hydrophobic anticancer agents for sustained drug delivery. In this study, we developed MNPs with optical imaging properties using new near-infrared dyes to quantitatively determine their long-term biodistribution and tumor localization with and without an external magnetic field in mice with xenograft breast tumors. MNPs localized slowly in the tumor, reaching a peak 48 h post-injection before slowly declining over the next 11 days. One hour exposure of the tumor to a magnetic field further enhanced MNP localization to tumors. Our MNPs can be developed with combined drug delivery and multimodal imaging properties to improve cancer diagnosis, provide sustained treatment, and monitor therapeutic effects in tumors over time.

Pharmacokinetics of contrast agents targeted to the tumor vasculature in molecular magnetic resonance imaging

Molecular magnetic resonance imaging (MRI) is increasingly used to investigate tumor angiogenic activity non-invasively. However, the pharmacokinetic behavior and tumor penetration of the often large contrast agent particles is thus far unknown. Here, pharmacokinetic analysis of cyclic asparagine-glycine-arginine (cNGR) labeled paramagnetic quantum dots (pQDs) was developed to quantify the contrast agent's homing efficacy to activated endothelial cells of angiogenic tumor vessels using dynamic contrast-enhanced (DCE) MRI. cNGR homes to CD13, an overexpressed aminopeptidase on angiogenic tumor endothelial cells. First, a two-compartment pharmacokinetic model, comprising the blood space and endothelial cell surface, was compared with a three-compartment model additionally including the extravascular-extracellular component. The resulting extravasation parameter was irrelevantly small and was therefore neglected. Next, the association constant K(a), the dissociation constant k(d) and the fractional plasma volume v(P) were determined from the time-series data using the two-compartment model. Magnitude and spatial distribution of the parameters were compared for cNGR-labeled and unlabeled pQDs. The tumor area with significant K(a) values was approximately twice as large for cNGR-pQDs compared with unlabeled pQDs (p < 0.05), indicating more contrast agent binding for cNGR-pQDs. Using cNGR-pQDs, a two-fold larger area with significant K(a) was also found for the angiogenic tumor rim compared with tumor core (p < 0.05). It was furthermore found that both contrast agents perfused the tumor at all depths, thereby providing unequivocal evidence that rim/core differences can indeed be ascribed to stronger angiogenic activity in the rim. Summarizing, molecular DCE-MRI with pharmacokinetic modeling provides unique information on contrast agent delivery and angiogenic activity in tumors.

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.

Optical small animal imaging in the drug discovery process

Molecular imaging of tumors in preclinical models is of the utmost importance for developing innovative cancer treatments. This field is moving extremely rapidly, with recent advances in optical imaging technologies and sophisticated molecular probes for in vivo imaging. The aim of this review is to provide a succinct overview of the imaging modalities available for rodents and with focus on describing optical probes for cancer imaging.

HER2 targeting as a two-sided strategy for breast cancer diagnosis and treatment: Outlook and recent implications in nanomedical approaches

At present, mammary carcinoma is the second most common type of malignant tumor in adult women after lung cancer, as more than one million women are diagnosed with breast cancer every year. Despite advances in diagnosis and treatment, which have resulted in a decrease in mortality in recent decades, breast cancer remains a major public health problem. One of the most significant unresolved clinical and scientific problems is the occurrence of resistance to clinical treatments and their toxicity (and how to predict, prevent and overcome them). However, the heterogeneity of human breast cancer in terms of genetic features, molecular profiles and clinical behavior represents a constraint obstructing the discovery of a solution to the disease. It is currently considered that the chances of success of therapy may increase if the tumor cells are selectively removed before they can evolve to their mature stages up to metastases production. Therefore, novel and more sensitive diagnostic tools are being developed, with the aim of improving the early and noninvasive detection of rising malignancies and the accuracy of tumor tissue localization. Meanwhile, there is an emerging use of targeted therapies in oncology, depending on the expression of specific proteins or genes present in tumor cells. Among the molecular targets considered for the treatment of breast cancer cells so far, we chose to focus on examples involving overexpression and/or gene amplification of "Human Epidermal growth factor Receptor 2" (HER2) protein. In current studies, various types of nanoparticles conjugated with the anti-HER2 monoclonal antibody, the so-called "trastuzumab", are investigated extensively due to promising results in biological and preclinical applications aimed at improving the treatment of breast cancer. In this paper, we present a critical review of the preparation and use of different kinds of trastuzumab-functionalized nanoparticles, with an emphasis on the therapeutic and diagnostic (theranostic) potential of this generation of hybrid nanoparticles, exploiting the multifaceted mechanisms of action of trastuzumab against malignant cells.

Gold nanotags for combined multi-colored Raman spectroscopy and x-ray computed tomography

Multi-color gold-nanoparticle-based tags (nanotags) are synthesized for combined surface-enhanced Raman spectroscopy (SERS) and x-ray computed tomography (CT). The nanotags are synthesized with quasi-spherical gold nanoparticles encoded with a reporter dye (color), each with a unique Raman spectrum. A library of nanotags with six different colors were synthesized for a range of gold nanoparticle sizes and an optimum size has been established to yield the largest SERS intensity and x-ray attenuation that is higher than the iodinated CT contrast agents used in clinics. Proof-of-principle in vivo imaging results with nanotags are presented that, for the first time, demonstrates the combined in vivo dual modality imaging capability of SERS and CT with a single nanoparticle probe.

Optical imaging-guided cancer therapy with fluorescent nanoparticles

The diagnosis and treatment of cancer have been greatly improved with the recent developments in nanotechnology. One of the promising nanoscale tools for cancer diagnosis is fluorescent nanoparticles (NPs), such as organic dye-doped NPs, quantum dots and upconversion NPs that enable highly sensitive optical imaging of cancer at cellular and animal level. Furthermore, the emerging development of novel multi-functional NPs, which can be conjugated with several functional molecules simultaneously including targeting moieties, therapeutic agents and imaging probes, provides new potentials for clinical therapies and diagnostics and undoubtedly will play a critical role in cancer therapy. In this article, we review the types and characteristics of fluorescent NPs, in vitro and in vivo imaging of cancer using fluorescent NPs and multi-functional NPs for imaging-guided cancer therapy.

Near-infrared fluorescence: application to in vivo molecular imaging

Molecular imaging often relies on the use of targeted and activatable reporters to quantitate and visualize targets, biological processes, and cells in vivo. The use of optical probes with near-infrared fluorescence allows for improved photon penetration through tissue and minimizes the effects of tissue autofluorescence. There are several parameters that define the effectiveness of imaging agents in vivo. These factors include probe targeting, activation, pharmacokinetics, biocompatibility, and photophysics. Recent advances in our understanding of these variables as they pertain to the application of optical reporters for in vivo imaging are discussed in this review.