Biomedical Engineering Reference
In-Depth Information
h e ZnONRs grown onto indium-tin-oxide (ITO)-coated glass surface
using zinc nitrate hexahydrate/hexamethylenetetramine (HMT) in aque-
ous phase have been utilized in the development of a urea biosensor [46].
h e Urs was immobilized onto ZnONRs/ITO at physiological pH via elec-
trostatic interactions between Urs and ZnO to fabricate an Urs/ZnONRs/
ITO bioelectrode. A linear amperometric response was obtained on the
Urs/ZnONRs/ITO biolectrode for urea concentrations in the range of
1-20 mM with a sensitivity of 0.4 μA mM
-1
, a response time of 3 s, a LOD
of 0.13 mM, and a K
M
app
of 9.09 mM. Further, studies indicate the selectiv-
ity of bioelectrode against glucose and ascorbic acid. Results indicate that
ZnONRs provide suitable microenvironment for Urs immobilization and
can be utilized in biosensor design and other biological applications.
Functionalized multilayered graphene (MLG), because of its very large
2D electrical conductivity and large surface area, has been used for the
fabrication of a novel amperometric urea biosensor [47]. A thin i lm of
functionalized MLG was fabricated onto an ITO substrate by electro-
phoretic deposition (EPD) technique and was used to immobilize ure-
ase and GLDH using ethyl(dimethylaminopropyl)carbodiimide and
N-hydroxysuccinimide (NHS) chemistry. h is biosensor showed linearity
in the 10−100 mg dL
-1
concentration range, sensitivity of 5.43 μA mg
-1
dL
cm
-2
, a low LOD of 3.9 mg dL
-1
, and a response time of 10 s, demonstrating
that MLG is a promising material for electrochemical biosensing applica-
tions of other clinically important bioanalytes such as glucose, cholesterol,
triglycerides, etc.
An amperometric biosensor based on CAT and a modii ed carbon paste
electrode (CPE) with ZnONPs have been applied to dopamine (DA) detec-
tion [54]. h e ZnONPs could play a key role in facilitating the electron
transfer between CAT and CPE. h e CAT/ZnONPs/CPE showed a good
sensitive state towards oxidation of DA in the range from 5 to 41 μM. h e
designed biosensor showed a good stability and retained 91% activity at er
21 days.
Zhou
et al.
proposed the application of a CRGO with the nature of a 2D
single sheet modii ed glassy carbon electrode (CRGO/GCE) for the prep-
aration of an electrochemical sensing and biosensing platform [26]. h e
electrocatalytic behaviors of eleven kinds of organic and inorganic elec-
troactive compounds (i.e., probe molecule (potassium ferricyanide), free
bases of DNA (guanine [G], adenine [A], thymine [T], and cytosine [C]),
oxidase/dehydrogenase-related molecules (H
2
O
2
/NADH), neurotransmit-
ters (DA), and other biological molecules (ascorbic acid [AA], UA, and
acetaminophen [APAP]) were employed to study their electrochemi-
cal responses at the CRGO/GCE, which show more favorable electron
