Biomedical Engineering Reference
In-Depth Information
Nature
Water
molecule
DNA
Virus rythrocyte
Apple
10
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10
-1
10
4
10
6
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Nanometers
Ta blet
capsule
Microparticles
Polymer
Nanoparticles
Micelles
Liposome
Dendrimers
Nanotubes
Quantum dots
Niosome
Pharmaceutical
nanotechnology
FIGURE 1.1
(
See color insert.
) Dimensions scale of nanotechnology.
novel carriers, such as liposomes, polymeric micelles, and NPs, are now known as nanovehicles.
However, this is only in the terms of size. These conventional drug delivery systems would have
developed to their current state regardless of the current development of nanotechnology. To fully
understand the scope of nanotechnology in the drug delivery field, it may be favorable to categorize
drug delivery systems by providing examples from before and after the rise of nanotechnology.
The properties of materials at the nanometer scale can be incredibly altered from those at a
larger scale. As the size decreases from bulk compounds, only very small changes in the properties
occur until the size of the particulates falls below 100 nm, while remarkable changes in properties
can further take place. Nanostructured materials are of great interests for the development of novel
properties and functions (Bhushan 2010).
Nanoparticulate drug delivery systems offer many benefits over conventional dosage forms. The
advantages of nanoparticulate drug delivery systems include improved therapeutic efficacies, reduc-
tions in toxicity, improved biodistributions, and improved patient compliance. Pharmaceutical NPs
contain entrapped API substances and are composed of tens or hundreds of atoms or molecules,
ranging from 5 to 300 nm in size and with different morphologies, such as amorphous, crystalline,
spherical, and needles, among others (Saraf 2006).
Nanosized formulations and structures can be produced by using either “bottom-up” or “top-down”
fabrication methods. In “bottom-up” methods, nanoparticulate structures are developed by building up
atoms or molecules in a controlled manner through the regulation of thermodynamic properties such
as self-assembly, precipitation, and crystallization. On the other hand, advances in nanotechnologies
can be used to fabricate nanoscale structures through size-reduction approaches. These techniques,
referred to as “top-down” nanofabrication technologies, include photolithography, nanomolding, dip-
pen, lithography, and nanofluidics (Figure 1.2 compares the bottom-up and top-down techniques in
various manufacturing processes) (Peppas 2004, Sahoo and Labhasetwar 2003).
The reduction of size, having a crucial role in pharmacy, is essential for proper unit operations.
It helps in improving the performance of dosages and by providing better formulation opportunities
for drugs. Drugs with sizes in the nanometer range improve performances in various dosage forms.
Nano-sized formulations provide enhancements in surface area, solubility, rate of dissolution, and
oral bioavailability. It may also provide a rapid onset of therapeutic action, a reduction in doses (and
frequencies), and decreased fed/fasted and patient-to-patient variabilities.
Particulate dispersions, or solid particles with a size in the nanometer range (10-1000 nm),
are known as NPs, in which a drug is dissolved, entrapped, encapsulated, or attached to a NP
