Biomedical Engineering Reference
In-Depth Information
receptor 2 (anti-HER2 or anti-HER2/neu) forming IO-Ab. HER2 is a cell mem-
brane protein that is overexpressed in several types of human cancer cells. Using
a HER2/neu overexpressing human breast cancer cell line SK-BR3 as a model
cell, the IO-Ab successfully isolated about 73.6% (with a maximum capture of
84%) of SK-BR3 cells that were spiked in 1 mL of fresh human whole blood.
The IO-Ab preferentially bound to SK-BR3 cells over the 10
9
normal cells
found in blood due to the high level of HER2/neu receptor on the surface of the
cancer cell membrane unlike the normal cell membrane surfaces. Their studies
exhibited an enrichment factor (cancer cells over normal cells) of 1:10,000,000
in a magnetic field (with gradient of 100 T/m) through the binding of IO-Ab on
the cell surface that resulted in the preferential capture of the cancer cells.
In addition, as shown in the examples above, a number of studies on bio-
conjugated NMs for infectious diseases diagnostics have started to emerge.
These studies have shown that the use of NMs as conjugates to biorecognition
elements have great potential in the development of biosensing devices that are
easy to use, fast, highly sensitive (lower detection limit compared to conven-
tional assays), and capable of detecting analytes even in complex media like
blood. Moreover, due to the small dimensions of the NMs, they can be incorpo-
rated into portable handheld devices for POC diagnostics.
Bioconjugation of NMs for diagnostic applications has led to more selective
and even more specific sensing of target analytes. However, for the development
of cost effective sensing devices that allow for multiplex sensing and at the same
time, provide fast and high-resolution analysis (more sensitive), the transducer
surface are often nanomanipulated. Nanomanipulation techniques include elec-
tron beam lithography (EBL), oblique angle deposition (OAD), nanoimprint
lithography (NIL), nanosphere lithography (NSL), dip-pen lithography, micro-
contact printing (µCP), and various self-assembly approaches
233,234
This sec-
tion will only present sensor fabrication/modification of the most promising
sensors in the field of POC medical diagnostics—amperometric and field effect
transistor (FET)-based potentiometric sensors and localized surface plasmon
resonance (LSPR), and surface enhanced Raman spectroscopy (SERS).
In applications where uniformity and reproducibility of surface property is
very important, the expensive top-down approaches like EBL is still the method
of choice.
235
This is due to the fact that bottom-up approaches such as NIL and
NSL suffer from reproducibility and reliability issues. Nevertheless, bottom-up
techniques are gaining importance owing to the low cost, simplicity, and speed
of the methods.
236,237,238,239
One of the most promising applications of biocompatible NMs is drug deliv-
ery. Today, a number of nano-enabled drugs are available for various applications.
A few of these are shown in
Table 3.2
. Aside from the use of NMs for MRI contrast
agents and drug encapsulation, some are also being studied for vaccine delivery.
192
In this study, they focused on the use of the semiconductor NMs, in particular
the QDs as an alternative vaccine delivery platform. They used <15 nm QDs
with a crystal shell of alternating cationic and anionic layers, which consisted of
