Nanomaterials for targeted imaging are capable of delivering large numbers of contrast agents per targeted molecular recognition event to achieve high-sensitivity imaging. Nanovectors can also simultaneously deliver different types of imaging agents to enable imaging. Tran et al. studied gadonanotubes (GNTs), short (20–80 nm) segments of single-walled carbon nanotubes encapsulating small clusters of gadolinium ions, as magnetic nanolabels. They showed that the magnetic labeling of MSCs with GNTs in vitro did not affect the differentiation potential of the MSCs; however, cell adhesion properties of the MSCs were impaired.31 Sanchez-Antequera

Inhibitors,research,lifescience,medical et al. developed a novel methodology for performing genetic modification and cell isolation in a single standardized procedure that they called “magselectofection,” which integrated clinically approved Inhibitors,research,lifescience,medical nanomagnetic cell separation and magnetofection, nanomagnetically guided nucleic acid delivery. It was shown that the performance of cell sorting and cell recovery Inhibitors,research,lifescience,medical is not affected by magselectofection and

that the function, viability, and differentiation of cells are not diminished.32 Optical Labeling Optical labeling (OL) involves introducing a Wnt activation fluorescent signal to the cells, primarily in the near-infrared region. The method is based on ex vivo labeling of cells with a fluorescent tag, subsequent engraftment of the labeled cells, and visualization of their accumulation in specific target organelles of interest. OL is as sensitive Inhibitors,research,lifescience,medical as radiolabel-based imaging techniques but without any exposure to irradiation. OL provides an effective means of repeatedly tracking cells noninvasively, thereby providing insight into cell migration to the target site. Cell labeling

efficiency is usually Inhibitors,research,lifescience,medical improved if the cells are incubated with the fluorescent dye in serum-free media as opposed to incubation in serum-containing media. One major disadvantage of OL is the limited tissue penetration of fluorescent labels in vivo. Tracer accumulation in deep tissues, more than about 4 cm to 10 cm from the skin surface, may not be detected. Nanomaterial-based cellular labels like quantum dots have made OL a relatively 4-Aminobutyrate aminotransferase low-cost method, and it has become an indispensable tool in small animal studies.33 Multimodality Imaging The combination of several molecular imaging modalities can offer synergistic advantages over any one modality alone. Combining an optical imaging modality with 3D tomographic techniques such as positron emission tomography, single-photon emission computed tomography, or MRI can allow for noninvasive imaging in living subjects with higher sensitivity and/or accuracy with the needed resolution. Shi et al. developed bifunctional anionic Eu3+-doped Gd2O3 hybrid nanoparticles as a luminescent and T1-weighted MRI contrast agent for stem cell labeling.