Diseño de nuevos (bio)sensores electroquímico basados en el uso de compósitos de grafito modificados con grafeno y nanopartículas de magnetita
Abstract
In this thesis were developed electrochemical sensors based on the employment of
graphite powder composites modified either with electro-generated nanoparticles of
Fe304 or graphene, for the quantification of bioanalytes of clinical relevance like
hydrogen peroxide, glucose and dopamine.
The excelent electrocatalytic properties of the Fe304 nanoparticles dispersed in the
composite made possible the amperometric detection of hydrogen peroxide at very low
potentials (-0,100 V) with the consequent improvement in the sensibility and selectivity
of the sensor.
The simultaneous incorporation of different proteins (insulin, glucose oxidase,
ovolizocim, mucin, albumin and casein) and Fe304 in the composite allowed to obtain a
drastic improvement in the reduction signal of hydrogen peroxide, due to the
considerable increment in the exposed electrocatalytic surface area The presence of
the proteins within the composite favors a more efficient dispersion of the Fe304
nanoparticles, which in turns produce a considerable increment in the exposed
electrocatalytic surface area augmenting the electro-analytical signal. The synergic
effect between the Fe304 nanoparticles and the proteins resulted in a significant
decrease in the charge transfer resistance towards hydrogen peroxide reduction, thus,
in an important increment in thesensitivity and repeatability of the amperometric
response. This effect was highly dependent on the Fe304/protein proportions and
protein nature.
Due to the good response obtained with the aboye mentioned modified electrode
for the amperometric reduction of hydrogen peroxide, we incorporated the enzyme
glucose oxidase to obtain an amperometric biosensor for glucose. The analytical signal
was obtained from the amperometric reduction of enzimatically-generated hydrogen
peroxide. A sensitive, stable, reproducible and fast biosensor for the detection of
glucose was obtained, allowing its use for direct quantification of glucose in human
blood serum, with an excellent correlation with the conventional spectrophotometric
technique. Another aspect addressed in this thesis was the study of a new electrode for the
development of electrochemical sensors based in the incorporation of chemically
reduced graphene oxide in graphite composites. Through the employment of medium
exchange adsorptive stripping voltammetry, the determination of submicromoiar leveis
of dopamine was achieved, even in excess of ascorbic acid and serotonin.
The sensors proposed in this thesis, represent a strategy with a great potentiality for
future development of electrochemical (bio)sensors using other biorecognition
molecules and new transduction schemes.
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