Recent progress in an emerging area of designing aptamer and nanomaterial conjugates as molecular diagnostic and drug delivery agents in biomedical applications is summarized. Aptamers specific for a wide range of targets are first introduced and compared to antibodies. Methods of integrating these aptamers with a variety of nanomaterials, such as gold nanoparticles, quantum dots, carbon nanotubes, and superparamagnetic iron oxide nanoparticles, each with unique optical, magnetic, and electrochemical properties, are reviewed. Applications of these systems as fluorescent, colorimetric, magnetic resonance imaging, and electrochemical sensors in medical diagnostics are given, along with new applications as smart drug delivery agents.

Design of smart MRI contrast agent based on superparamagnetic iron oxide nanoparticles and aptamers has been described for the detection of human alpha-thrombin protein. The contrast agent is based on the assembly of the aptamer functionalized nanoparticles in the presence of thrombin. A detectable change in MRI signal is observed with 25 nM thrombin in human serum. Changes were neither observed with control analytes, streptavidin, or bovine serum albumin, nor with inactive aptamer functionalized nanoparticles.

Metastases, and not the primary tumor from which they originate, are the main reason for mortality from carcinoma. Although the molecular mechanisms behind metastasis are poorly understood, it is clear that epigenetic dysregulation at the level of microRNA expression is a key characteristic of the metastatic process that can be exploited for therapy. Here, we describe an miRNA-targeted therapeutic approach for the prevention and arrest of lymph node metastasis. Therapy relies on the inhibition of the pro-metastatic microRNA-10b. It is delivered to primary and lymph node metastatic tumor cells using an imaging-capable nanodrug that is designed to specifically home to these tissues. Treatment of invasive human breast tumor cells (MDA-MB-231) with the nanodrug in vitro downregulates miR-10b and abolishes the invasion and migration of the tumor cells. After intravenous delivery to mice bearing orthotopic MDA-MB-231-luc-D3H2LN tumors, the nanodrug accumulates in the primary tumor and lymph nodes. When treatment is initiated before metastasis to lymph nodes, metastasis is prevented. Treatment after the formation of lymph node metastases arrests the metastatic process without a concomitant effect on primary tumor growth raising the possibility of a context-dependent variation in miR-10b breast oncogenesis.

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 Cy5.5 (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. Cancer Res; 70(19); 7553-61. ©2010 AACR.

Smart agents. A contrast agent was designed by combining target specific nucleic‐acid aptamers against adenosine with superparamagnetic iron oxide nanoparticles. Target‐induced disassembly of clustered nanoparticles in the presence of adenosine led to an increase in T2, which was seen as an increase in the brightness of the magnetic resonance image (see figure).

The universal sensor array is composed of 12 fluorescently silent non-specific artificial nanoreceptors (2D-nps) for the identification and classification of five proteins, three types of breast cancer cells and a structure-switching event of a macromolecule.

Nanotechnology 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 this study, we have investigated the intrinsic peroxidase-like activity of citrate-capped AuNPs (perAuxidase) and demonstrated that the nanozyme function can be multiplexed and tuned by integrating oligonucleotides on a nanoparticle surface. Systematic studies revealed that by controlling the reaction parameters, the mutiplexing effect can be delayed or advanced and further used for aptasensor applications.