Biomedical Engineering Reference
In-Depth Information
smaller than 20 nm can transmit through blood vessel walls. Magnetic
nanoparticles, for instance, can image metastatic lesions in lymph nodes
because of their ability to exit the systemic circulation through the perme-
able vascular epithelium [7]. Nanoparticles also of er the ability to pen-
etrate the blood-brain or stomach epithelium [7-9] barriers that make it
dii cult for legacy therapeutic and imaging agents to reach their intended
targets. h e size of nanoscale devices also allows them to interact readily
with biomolecules on the cell surface and within the cell, ot en in ways that
do not alter the behavior and biochemical properties of those molecules
[7]. Such ready access to the interior of a living cell af ords the opportunity
for unprecedented gains on the clinical and basic research frontiers. h e
ability to interact with receptors, nucleic acids, transcription factors, and
other signaling proteins at their own molecular scales should provide the
data needed to better understand the complex regulatory and signaling
networks and transport processes that govern the behavior of cells in their
normal state [10] and as they undergo changes that transform them dur-
ing the disease process [7]. Today, metal nanoparticles are i nding increas-
ing acceptance in biomedical applications, with optical properties such as
surface plasmon resonance (SPR) and the l uorescence of gold and silver
nanoparticles [11-13] forming the basis of optics-based analytical tech-
niques used for bioimaging [14-16] and biosensing [17, 18]. Au nanopar-
ticles are also useful for drug delivery [19, 20] and photothermal ablation
treatment [21, 22]. For such biomedical applications, the biocompatibility
of a metal surface is a key consideration, and a good compliance strategy
would be to perform a metal nanoparticle synthesis using biological sys-
tems. In this chapter, biosynthesis of metal nanoparticles and their possible
applications are discussed in detail.
8.2
Synthesis of Metal Nanoparticles
h ere are three main approaches for the synthesis of metal nanoparticles—
physical, chemical and biological. Broadly, the nanoparticles are synthesized
by either top-down or bottom-up approaches. h e top-down approach is
based on the mechanical method of size reduction by breaking down the
bulk materials gradually to nanoscale structure. h e bottom-up approach
is based on the assembly of atom or molecules to molecular structure in
nanoscale range. Both chemical and biological synthesis of nanoparticles
relies on the bottom-up approach [23]. Physical approaches to synthesize
metallic nanoparticles include UV irradiation [24, 25], sonochemistry [26],
radiolysis [27], laser ablation [28] and so forth. During physical fabrication,
