Biomedical Engineering Reference
In-Depth Information
1.2.4 Nanoparticle-Enabled Diagnostics
The emergence of nanotechnology has refocused the research effort on the remark-
able nanoscale properties of several noble metal nanoparticles, such as highly
tunable spectral behavior, high surface to volume ratios, and astounding optical
properties. An example of these optical properties is localized surface plasmon
resonance (LSPR), which is the collective oscillations of free electrons at a metal-
dielectric interface when the frequency of incident light matches with the frequency
of electron oscillation. Recently, noble nanoparticles, such as gold and silver, have
been intensively researched for use in biomedicine and more specifically for the
development of inexpensive, highly sensitive detection assays.
Colloidal gold nanoparticles have been intensively explored for the purpose of
biosensing due to their optical and physical properties. Gold nanoparticles can
easily be synthesized via salt reduction or laser ablation techniques and
functionalized with thiol-modified oligonucleotides, permitting the detection of a
vast array of biomolecules, nucleic acid sequences, and pathogens. There are fewer
reports in the literature on the use of functionalized silver nanoparticles compared
to their gold counterparts. This is mainly due to the difficulty of synthesizing silver
nanoparticles with a homogeneous size distribution and a heightened difficulty for
thiol functionalization.
The signal enhancement brought about by noble metal nanoparticles permits the
development of detection assays that are more sensitive, faster, simpler, and cost-
effective. These diagnostic platforms can be based on electrochemistry, lumines-
cence, target labeling, and SPR biosensors and may be further combined to allow
for early identification of diseases of clinical relevance.
For example, pathogen detection is of utmost importance in multiple sectors,
such as in the food industry, environmental quality control, clinical diagnostics,
biodefense, and counterterrorism. Failure to appropriately and specifically detect
pathogenic bacteria can lead to serious consequences and ultimately be lethal.
Conventional methods for the detection of infectious agents are based on standard
microbiological methods such as plate-counting or biochemical assays. Although
these methods are accurate, they are time consuming as isolation and culturing of
large quantities of bacteria can take up to 7 days. In recent years, major
breakthroughs in biosensor technology reduced the time required to detect bacteria.
However, the majority of techniques currently employed to require some type of
radio, enzymatic, or fluorescent labeling to report biomolecular interaction. Other
techniques such as direct impediometric detection is limited by the fact that the
media utilized needs to be optimized for electrical measurements and that not all
microorganisms generate an adequate amount of ionized metabolites to allow for
their detection. LSPR is a method that can be suitably modified for bacterial
detection as it is designed for real-time monitoring of all dynamic processes without
labeling and complex sample preparation.
