Biomedical Engineering Reference
In-Depth Information
of 1.25 ng/ml genomic DNA was determined under optimized conditions.
h e dual-labeled AuNP-facilitated electrochemical sensor was also evalu-
ated by clinical sputum samples, showing a higher sensitivity and specii c-
ity and the outcome was in agreement with the PCR analysis [99].
h e other system was developed for the electrochemical detection of the
mutated
BRAF
gene associated with papillary thyroid carcinomas (PTC).
PTC is the most common carcinoma of the thyroid gland and the most
frequent type of endocrine cancers. Over the past six decades, the inci-
dence of PTC has increased in many countries [100-102]. PTC is sporadic
in around 95% of cases and familial in the remaining 5%. PTC patients
have a very good prognosis provided that the carcinoma is detected and
treated at an early stage. Given prompt intervention, the mortality rate is
typically less than 10%, even 10 years at er surgery [103]. For this pur-
pose, a biotinylated 30-nucleotides probe DNA was immobilized in a
streptavidin-modii ed 96-well microtiter plate and the free active sites of
the streptavidin were blocked using biotinylated BSA. h e biotinylated
target DNA was then added and allowed to hybridize with the immobi-
lized probe DNA for 30 min. Subsequently, streptavidin-labeled AuNPs
were added, and a nanoparticle enlargement process was performed using
gold ion solution and formaldehyde reductant. h e AuNPs were then
dissolved in bromide and the DNA hybridization detection process was
performed using a square-wave stripping voltammetry technique. h e
detection limit was estimated to be 0.35 aM, based on a signal-to-noise
ratio of 3:1. h is value was compared with regular protocol where no gold
amplii cation method was applied. As a result, it was found that approxi-
mately three orders of magnitude lower results were obtained with the
gold amplii cation method which included assay. Finally, the proposed
approach was applied in dif erentiating between the mutant and wildtype
BRAF
sequences that are present in genuine 224-nucleotides DNA and
successful results were obtained [104].
Besides DNA biosensors, AuNP modii ed aptasensors were also used for
the same purpose. A practical EIS aptasensor based on an anti-thrombin
aptamer as a molecular recognition element was prepared [105]. h rombin
is the last enzyme protease involved in the coagulation cascade, and it con-
verts i brinogen to insoluble i brin that forms the i brin gel both in physi-
ological conditions and in a pathological thrombus [106]. h rombin also
has hormone-like properties, and is involved in thrombosis and platelet
activation. h erefore, thrombin plays a central role in a number of car-
diovascular diseases [107] and is thought to regulate many processes in
inl ammation and tissue repair at the blood vessel wall [105]. For the con-
struction of aptasensor, AuNPs were self-assembled on the surface of a
