Biomedical Engineering Reference
In-Depth Information
A biosensor has been developed for the potentiometric determination
of AA based on ascorbate oxidase immobilization on ZnONRs [53]. Well-
aligned, perpendicular to the substrate, and highly dense ZnONRs were
grown on the gold coated substrate by using the hydrothermal growth
method. h en, they were functionalized by immobilizing ascorbate oxi-
dase with the crosslinking molecule 3-glycidoxypropy1trimethoxysilane
(GPTS). h e biosensor exhibited an output potentiometric response in
the wide linear dynamic range concentration of AA from 1×10
-6
to 5×10
-2
M with a good sensitivity of 32 mV decade
-1
, and showed excellent fast
response time (<10 s), better selectivity, repeatability, reproducibility and
no signii cant interference to the common interfering ions (K
+
, Na
+
, Ca
2+
and Zn
2+
) glucose and fructose, and showing a slight interference with
Cu
2+
. In addition, the biosensor retained the good enzymatic activity for
more than three weeks, due to a strong electrostatic interaction between
ascorbate oxidase and ZnONRs. h is biosensor was thus considered as
useful for ascorbic acid determination and monitoring in food, drugs, and
real samples.
h e same authors also developed a potentiometric L-lactic acid sensor
based on lactate oxidase immobilization on ZnONRs grown on gold coated
glass [52]. h e biosensor was developed by immobilizing lactate oxidase
on the ZnONRs in combination with glutaraldehyde as a crosslinker. h e
presented biosensor showed a wide linear detection concentration range
from 1×10
−4
-1×10
0
mM with an acceptable sensitivity, about (41.33 ± 1.58)
mV decade
-1
. In addition, the proposed biosensor showed a fast response
time, lower than 10 s, a good selectivity towards L-lactic acid in the pres-
ence of common interfering substances such as ascorbic acid, urea, glucose,
galactose, Mg
2+
and Ca
2+
, and sustained its response for more than three
weeks, thus being considered as a promising alternative to detect L−lactic
acid in biological samples. Using the same fabrication protocol, a galactose
biosensor was also developed [59]. h is galactose biosensor had a linear
detection concentration range from 10 to 200 mM with good sensitivity,
(89
.
10 ±
1
.
23) mV decade
-1
, a fast response time of less than 10 s, excellent
selectivity towards galactose in the presence of common interferents (AA,
UA, glucose, and Mg
2+
), and a shelf life of more than four weeks. All h ese
features indicated that this biosensor could be used for the monitoring of
galactose in milk, food, and blood samples, as well as for clinical purposes.
A GO-modii ed light addressable potentiometric sensor (GO-LAPS)
has been developed and applied to a ssDNA probe immobilization and
hybridization with complementary ssDNA molecules of dif erent chain
length monitoring [58]. Dif erent curves of LAPS' currents versus ana-
lyte concentrations for ssDNA probe binding and the target ssDNA
