Biomedical Engineering Reference
In-Depth Information
found antibodies, biopolymers (such as collagen), and monolayers of small
molecules [
80
]. For example, a coating of small polyethylene glycol (PEG)
molecules has allowed NPs to be specifically absorbed by cancer cells, but not
significantly by macrophages. Therefore, PEG could be used in cancer therapy.
Surface modification has other benefits. Because of their surface charge density,
nanoparticles tend to agglomerate. As discussed previously, the repulsion between
the negative charges is offset by the impact of dissolved salts of opposite charge in
the biological solution. Polymeric coatings can be used to prevent agglomeration.
However, it is necessary to study the characteristics and impacts of these polymer
layers, as they may have an effect on the performance of a nanoparticle.
Functionalization of nanoparticles with peptides can be used to control
protein-nanoparticle interactions. Studies show that the chirality of the functional
groups bound to nanoparticles affects the complex stability. This demonstrates that
ligands can be used to control protein recognition [
79
].
The particle's interaction with biological compounds is dependent on protein
association and dissociation kinetics. The nanomaterial-ligand complexes have a
lifespan ranging from microseconds to days. Multiple proteins form transient
complexes with nanoparticles, and it is known that protein concentration and
composition of the physiological fluid will influence the formation of the corona.
In the blood, human serum albumin and fibrinogen are predominant and thus
dominate the particle surface for brief periods of time, whereas proteins present
in a lesser extent with higher affinities and slower kinetics might, in due course, oust
them. Conversely, bronchial and ocular fluids are less abundant in proteins and it is
the lower affinity proteins that will dominate the nanoparticle's surface.
A detailed review of the formation of protein corona on the surface of
nanoparticles, the kinetics of hard and soft corona, and parameters affecting the
on nanoparticle-cell interaction, toxicity, and circulation lifetime in body is
studying and analyzing the adsorbed corona on the surface of nanoparticles.
1.4.1.2 Nanoparticle-Lipid Interactions
Nanoparticle interactions with phospholipid bilayers result in a process called
membrane wrapping, where the nanoparticle is often engulfed in the lipid moiety.
This phenomenon is valuable for site-specific drug delivery. In order to overcome
the forces obstructing particle uptake in the cell, surface ligands are cemented on
the particle's surface and interact with complementary receptors on the cell,
resulting in receptor-mediated endocytosis. These ligands can be chemical
moieties, metallic sites, polymers, or surface functionalities. Many strategies,
such as the use of amphipathic cell-penetrating peptides (CCPs), polycationic
polyethyleneimine (PEI), and polyamidoamine, permit the particles to enter the
cell membrane without causing cell injury. However, attention must be given to the
