Imaging in Stem Cell Transplant and Cell-based Therapy

22

nanoparticles, served as high contrast agents, aiding in PAI of targeted cells [ 31 ].
Particularly, tunable near-infrared (NIR)-responsive plasmonic nanoparticles,
including gold nanoshells (GNSs), gold nanorods (GNRs), and golden carbon nano-
tubes (GNTs), have attracted attention for minimally invasive imaging and therapy
owing to their high NIR absorption (e.g., ∼700–900 nm) in the window of optical
transparency of most biological tissues as well as high efficiency conversion of
absorbed energy into thermal and acoustic phenomena [ 28 , 31 – 35 ]. Although these
studies mainly focused on solid and metastatic tumor cells, including stem circulat-
ing tumor cells, such plasmonic nanoparticles represent a potentially powerful tool
for in  vivo PAI of other types of stem cells. Carbon nanotubes (CNTs) are also
sensitive contrast nanoagents that are useful for PAI; however, their biocompatibil-
ity is in question [ 28 , 30 ]. This challenge could be overcome by coating CNTs with
a thin layer of gold, thereby producing golden nanotubes [ 33 ], as well as various
types of biocompatible disguising agents [ 36 – 39 ].
In the following section we will outline five types of nanoparticles that have been
considered and researched in stem cell medicine, and give an overview of the in vivo
imaging that may be applicable.

2.4 Different Nanoparticles and Their Uses in Stem Cell

Applications

2.4.1 Superparamagnetic Iron Oxide Nanoparticles

Superparamagnetic Iron Oxide nanoparticles or SPIOs are the only commercial
nanoparticles that have been utilized in clinical applications. In 2009, the Food and
Drug Administration approved ferumoxides (Feridex®) and ferucarbotran (Resovist©)

Pulsed or

modulated

laser

Wide-band

ultrasound

Image

Formation

Organelle

Cell

Tissue

Organ

Whole-body

Comprehensive

pathophysiological

information

Trends in Biotechnology

Precise

medicine

Early-stage

theranostics

Structural

Functional

Molecular

Metabolic

Genetic

Multicontrast

Multiscale

Fig. 2.2 Photoacoustic imaging. Reprinted with permission from Liu et al. [ 26 ]

H.A. Jensen et al.