When nanoparticles bind to PSMA and are internalized, Dox is released and the system consequently regains its ability to fluoresce. than one type of imaging component, is also highly advantageous, as it allows for the maximal amount of data to be acquired from a single nanoagent preparation. The application of nanomedicine to the diagnosis and treatment of cancer has been ongoing for over 20 years, although its clinical Dimethyl 4-hydroxyisophthalate utility has yet to be fully realized (Retel et?al., 2009). For example, superparamagnetic iron oxide nanoparticles, which have proven to be highly useful contrast agents for magnetic resonance imaging, have been utilized to increase the accuracy of cancer nodal staging (Ferrari, 2005; Harisinghani et?al., 2003; Harisinghani and Weissleder, 2004), better delineate primary tumors (Enochs et?al., 1999), image angiogenesis (Tang et?al., 2005), and detect metastases (Harisinghani et?al., 2001; Saini et?al., 2000). While these initial agents relied upon the intrinsic ability of the materials to localize to diseased tissues, subsequent iterations have allowed for their targeting to sites of interest using a variety of ligands, including antibodies, peptides, aptamers, and small molecules. Herein, this review will focus upon the creation of targeted nanoagents for the improved detection of cancers. Given the breadth of this subject, this is not meant to be all\encompassing. Instead, we have chosen some of the most prominent examples of targeted nanomaterials utilized for the imaging of cancers. Importantly, this review will discuss the methodologies utilized for the discovery of potential targeting ligands, and examine the ultimate utility of the resulting targeted nanoagents. Dimethyl 4-hydroxyisophthalate For a more general overview of biomedical imaging in cancer detection and therapy please see (Fass, 2008). 2.?Nanomaterials in cancer imaging 2.1. Materials and modalities 2.1.1. Magnetic resonance imaging Magnetic resonance imaging (MRI) is a non\invasive technique that involves the disturbance of aligned nuclear spins in a strong magnetic field by a radio frequency pulse and the measurement of the realignment time of the nuclei to the Mouse monoclonal to TYRO3 magnetic field following termination of the pulse (Hornak, 2010). The realignment or relaxation time is tissue dependent allowing for the different magnetic gradients to be spatially localized to create an image with high tissue contrast based on differences in spin density (Kherlopian et?al., 2008). Two types of relaxation times T1, or spin\lattice (longitudinal) and T2, or spinCspin Dimethyl 4-hydroxyisophthalate (transverse), determine the signal for a particular tissue (Lin et?al., 2009). T1\weighted images are thus the result?of longitudinal relaxation time and T2\weighted images rely on the rate of transverse relaxation to afford positive and negative contrast enhancement in the MR image respectively (Lin et?al., 2009). MRI has become a valuable commodity in cancer detection due to its high soft tissue contrast, spatial resolution and penetration depth. A significant amount of research in the field of medical MRI has focused on the development of contrast agents to improve image signal intensity, which can be low in their absence and is an inherent limitation of MRI. A majority of contrast agent research has focused on gadolinium (Gd)\based MRI agents due to this lanthanide’s ability to decrease the T1 relaxation time, thus increasing the MR signal (Caravan et?al., 1999). Unfortunately,?one potential drawback of using paramagnetic Gd chelates is that relatively high concentrations are needed to achieve a sufficient increase in contrast signal resulting in a greater chance of acute toxicity (Caravan et?al., 1999; Lin et?al., 2009). In order to circumvent this, nanoparticulate strategies have been developed to increase the amount of complex delivered to a site of interest, such as tumors. For example, liposomal or micellar encapsulation of gadolinium chelates have successfully demonstrated the delivery of large payloads of these contrast agents to cancerous tissues (Mulder et?al., 2005; Zhang et?al., 2009). In addition to contrast agent delivery vehicles, nanoparticles such as those composed of crystalline iron oxide, have themselves been utilized as negative contrast enhancers for MRI due to their ability to shorten T2 relaxation times. This property was first realized in the mid 1980s while imaging patients with hepatic iron overload (Stark et?al., 1985). Studies shortly following this discovery demonstrated that small injectable ferrite particles were capable of detecting different types of cancer such as liver, splenic, and hepatic lymphoma (Saini et?al., 1987, 1987, 1987). More recent examples of using Dimethyl 4-hydroxyisophthalate these superparamagnetic nanoparticles for the MRI detection of cancer include the visualization of otherwise evasive lymph node metastases in patients with prostate cancer (Harisinghani et?al., 2003), as well as targeted nanoparticle conjugates that provided negative contrast enhancement for pancreatic cancer imaging (Montet et?al., 2006)..