Biomedical Engineering Reference
In-Depth Information
S
S
S
S
S
S
S
S
S
S
O
O
HO
HO
HN
HO
HO
HO
HO
HN
HO
HO
PNA
PNA
Figure 3.15 After treating the surface with 3-mercaptopropionic acid and
subsequent activation via 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/ N -
hydroxysuccinimide (EDC/NHS), the PNAs were attached to the backside of the
electrode.
The PNA-modiied Au was placed in contact with the open chamber for the
introduction of analysable solutions. The analyser measured the source-to-
drain voltage ( V SD ) versus the source-to-drain current ( I SD ), with a reference
electrode (Ag/AgCl) immersed in phosphate buffer solution.
Different solutions of DNA at different concentrations were used to
assess the perfect running and the sensitivity of the device. The increase in
conductance for these p -type semiconductors was consistent with an increase
in negative charge density due to the hybridisation of negatively charged
DNA. The experiments performed demonstrated that the device was able to
discriminate not only non-complementary DNA but also single-nucleotide
polymorphism. The recorded low luctuations of conductance were ascribed
to a non-speciic interaction between the DNA and the Au surface. Moreover,
the detection was the lowest (6.8 fM) with respect to other existing real-time,
label-free DNA detection systems.
As mentioned already, another important biomarker is represented by
prostate-speciic antigen (PSA), secreted by epithelial cells of prostate and
then introduced into the bloodstream. Little quantities of PSA (about 4 ng/
mL) are normally produced in healthy people, but its overexpression is strictly
related to prostatic cancer, and therefore it has high relevance as a biomarker.
In addition, it can be considered a model for the evaluation of the design of
new devices because a lot of data are available about it. PSA, once into the
bloodstream, partially interacts with plasma proteins, and so the total PSA is
given by the combination of the free PSA and the bounded PSA, rendering the
quantiication more complicated.
Li et al. were the irst to design a hybrid FET with CNTs and InO 2
nanowires (NWs), combining p -type and n -type semiconductors. They
 
Search WWH ::




Custom Search