Biomedical Engineering Reference
In-Depth Information
as oncology, cardiovascular and orthopedics. Nanomaterials have been used
in specific applications such as tissue engineered scaffolds and devices, site
specific drug delivery systems, cancer therapy and clinical bioanalytical di-
agnostics and therapeutics. An area of research where nanotechnology and
nanomedicine applications have been particularly prolific pertains to the de-
livery of diagnostic and therapeutic agents.
Drug delivery can be defined as the process of releasing a bioactive
agent at a specific rate and at a specific site. As current advances in bio-
technology and related areas are aiding the discovery and rational design
of many new classes of drugs, it is crucial to improve specific drug-delivery
methods, to turn these new advances into clinical effectiveness. Several
drugs are limited by their poor solubility, high toxicity, and high dosage,
aggregation due to poor solubility, nonspecific delivery, in vivo degrada-
tion and short circulating half-lives. Targeted drug-delivery systems can
increase patient compliance, extend the product life cycle, provide prod-
uct differentiation and reduce healthcare costs. Nanotechnology can be
correctly envisioned as the future of drug-delivery technology as it has
the potential to provide useful therapeutic and diagnostic tools in the
near future. NPs offer a suitable means to deliver small molecular weight
drugs as well as macromolecules such as proteins, peptides or genes in the
body using various routes of administration. The ability of the engineered
NPs to interact with cells and tissues at a molecular level provides them
with a distinct advantage over other polymeric or macromolecular sub-
stances. Drug delivery carriers are macromolecular assemblies that can
incorporate imaging and therapeutic compounds of distinct nature, such
as small chemicals, fluorophores and biosensors, peptides and proteins,
oligonucleotides and genes. They can be designed to improve the solubil-
ity of these cargo molecules and their bioavailability, and also to control
their circulation, biodistribution in the body, and release rate, together
enhancing their efficacy [50-51]. Surface property modifications confer
advantageous properties to the particle, such as increased solubility and
biocompatibility which are useful in the crossing of biophysical barriers.
The use of biodegradable materials in the NPs formulation permits drug
release for prolonged periods. For their small size, NPs can extravasate
through the endothelium in inflammatory sites, epithelium, tumors, or
penetrate microcapillaries.
4.1.1 Nanoparticle distribution
The natural clearance and excretion mechanisms of the human body pro-
vide a framework for the rational design of effective nanoparticles for use
in medical therapies. Once a pharmaceutical agent is introduced into the
circulatory system, it is distributed systemically via the vascular and lym-
phatic systems. The distribution of a drug in a tissue is correlated with the
relative amount of cardiac output passing through that tissue. Accordingly,
