Biomedical Engineering Reference
In-Depth Information
Apoptosis is the process of a death of a cell mediated by an intracellular program
that may occur in multicellular organisms. Apoptosis occurs when a cell is damaged
beyond repair, infected with a virus, or undergoing stressful conditions. Damage to
DNA from ionizing radiation or toxic chemicals can also induce apoptosis. The
“decision” for apoptosis can come from the cell itself, from the surrounding tissue,
or from a cell that is part of the immune system. During apoptosis, cells put in place
“suicide mechanism” which results in various modifications on the cellular level.
The most significant modifications are alteration of the outer mitochondrial mem-
brane, condensation of cell's cytoplasm and core, and fragmentation of DNA.
Many nanoparticle cytotoxicity researchers have identified mitochondria as a
potentially relevant target organelle with regard to the cellular effects of
NP. Currently, several NPs have been shown to be capable of eliciting damage of
the nuclear DNA [
91
]. On a single-cell level, such particle-induced injuries may
principally have three major consequences, usually depending on the type and
extent of DNA damage, namely, induction and fixation of mutations, induction of
DNA cell cycle arrest, and activation of signal transduction pathways which
promote apoptosis.
Correlating the physicochemical properties of nanoparticles and their biological
responses can be challenging as surface area, particle surface chemistry, biodegrad-
ability, concentration, and solubility will greatly affect the way the particle is going
to be perceived by the biological environment and their subsequent pharmacoki-
netics and biodistribution. It is therefore imperative to understand the mechanisms
governing the interactions of the aforementioned particles and the major players of
the immune response. In order to do that, the physicochemical properties, adsorbed
proteins, adherent cells, and inflammatory cytokines and growth factors need to be
fully characterized.
1.6 Conclusion
The late Nobel laureate physicist Richard Feynman laid the first stepping stones of
modern nanotechnology in 1959. In his lecture “There's plenty room at the bottom,
an invitation to enter a new field of physics,” he proposed to employ machine tools
to manipulate and control things on a small scale. In recent years, the field of
nanoscience has been rapidly evolving. Enormous amount funding has contributed
to advances in diagnostics and therapeutics at the nanoscale. However, these
nanodevices will ultimately need to pass many rigorous testing protocols to ulti-
mately be approved by the regulatory agencies, such as the FDA, before being
allowed on the markets. Therefore, much work is still needed in order to better
understand the interface between nanomaterials and biological systems. These
interactions are governed by a large number of phenomena such as the formation
of the protein corona, cellular contact, particle wrapping at cell surfaces, endocyto-
sis, and intracellular processes. A better understanding of the nano-bio-interface
will permit, in a near future, for the safe use of nanotechnology.
