Targeted Drug Delivery - Nanomaterials for Medical Applications - page 185

FIGURE 5.3 TEM image of organic soluble 20-nm IOMNP with narrow size distribution.
Courtesy of Ocean NanoTech.
requires the viscosity of the medium to be known and determines the diameter
of the particle by Brownian motion and light scattering properties. 48 The results
obtained by photon correlation spectroscopy are usually verified by scanning
electron microscopy (SEM) or TEM. This size of the water-soluble form called
the hydrodynamic size includes the water of solvation and is, therefore, higher
than the core or core/shell size. The hydrodynamic size and size distribution
determine the in vivo distribution, biological fate, toxicity, and targeting ability
of these NMs for drug delivery systems. In addition, they can influence drug
loading, drug release, and stability of NMs. Many studies have demonstrated
that NMs have a number of advantages over microparticles. 49 Generally, due to
their small size and mobility, NMs have relatively higher cell uptake in com-
parison with microparticles making them more available to a wider range of
cellular and intracellular targets. Following the opening of the endothelium
tight junction (TJ), NMs can cross the blood-brain barrier (BBB) by hyperos-
motic mannitol. 50 This may provide a route for sustained delivery of therapeutic
agents for difficult-to-treat diseases like brain tumors. 50 Kreuter et al. 51 showed
that Tween 80-coated NPs crossed the BBB as well and Zauner 52 showed that
submicron NMs are taken up by the majority of cell types but not the larger
microparticles. Caco-2 cells showed uptake of 100-nm NPs at 2.5-fold greater
than 1-µm microparticles and a 6-fold greater uptake than 10-µm microparticles