b2815 Tissue Engineering and Nanotheranostics “9.61x6.69”
230 Tissue Engineering and Nanotheranostics
include fluorescence imaging, photoacoustic imaging, Raman imaging,
computed tomography (CT), radionuclide imaging (PET and SPECT)
and magnetic resonance imaging (MRI).
According to a large number of literature reports, both organic
and inorganic nanomaterials can be applied for a nanotheranostic
system.52–54 Common materials used to synthesize or form nanocarri
ers include polymers, lipids, silicon dioxide, carbonbased materials,
gold, and iron oxides et al.53,55–70 In order to ensure in vivo circulation
escape host defenses and effectively penetrate blood vessels into the
tumor tissues, each class of nanomaterials needs to have a size of less
than 150 nm in diameter, with highly homogeneous particle distribu
tions, good biocompatibility and sufficient stability in vivo. In addi
tion, the nanomaterials must have the functions of modification with
imaging contrast, targeting elements and the loading of the antican
cer drug, without any changes to its nanomaterials properties. The
targeting ligands overexpressed on tumors are attached to the surface
of the nanomaterials so that they are bound to the receptors of cancer.
Drug loaded nanoparticles should be slowrelease before reaching the
tumor site. Once entered into the tumor tissue, drug loading nano
particles have a rapid drug release through physical or chemical
action. Compared to the current chemotherapy drugs, these nanocar
riers with unique drugrelease behavior can enhance the therapeutic
effect on cancer, and reduce the drug harm of body and tissues. In
the following sections, we briefly introduce some examples of possi
bilities for the different components in a theranostic system.
2. Nanomaterials for Drug Delivery
According to the needs of drug delivery and tumor therapy, different
morphology, size, change and hydrophobicity of nanocarriers can be
synthesized. The advantages of the use of nanomaterials as a delivery
tool of chemotherapeutic drugs have been widely recognized. The drug
delivery vehicle can overcome the following series of limitations associ
ated with traditional drug administration routes. (1) Drug solubility. In
order to dissolve the drugs and for convenient clinical use, solubiliza
tion agents such as Cremophor EL associated with hypersensitivity
