Development of a Novel Nanocomposite Based on Reduced Graphene Oxide/Chitosan/Au/ZnO and Electrochemical Sensor for Determination of Losartan
Authors: Ghanbari Khadijeh , Sivandi Ashraf 
Published: December 2019

Background:
Hypertension is a major risk for morbidity and mortality, while hypertension
is associated with cardiovascular disease and organ damage. Recent research efforts have focused
on the development of highly selective angiotensin receptor blockers. In which losartan (LOS)
is considered as a new generation of an effective oral drug product against arterial hypertension.
Therefore, the determination of drugs in biological fluids, pharmaceuticals (tablets), and wastewater
is of critical importance for clinical applications, forensics, quality control, and environmental
protection that call for the development of analytical methods. Many ranges of methods such as spectroscopic
methods and chromatographic techniques have been developed to determine LOS in pharmaceutical
formulations and biological fluids. However, there are crucial interference problems in
these methods. For these reasons, more sensitive, desirable, portable, low-cost, simple, and selective
nanocomposite-based sensors are needed in terms of health safety. Nanomaterials such as reduced
graphene oxide, chitosan, and metal nanoparticles are used to improve the sensitivity in the
development of electrochemical sensors.

Objective:
In this study, a novel reduced graphene oxide (RGO), chitosan (Chit), gold (Au), and zinc
oxide (ZnO) nanocomposite (RGO/Chitosan/Au/ZnO) was synthesized and used to develop a sensitive
and efficient electrochemical sensor for LOS detection.

Methods:
Modification of electrode by RGO/Chit/Au/ZnO nanocomposite was performed in four
stages with GO (at -2.0 V for 150 s), Chitosan (at -3.0 V for 300 s), Au nanoparticles (at -0.4 V for
400 s), and Zn nanoflowers like (at -0.7 V for 1200 s). The RGO/Chitosan/Au/ZnO nanocomposite
was characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction
(XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR).
Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) were used to detect LOS, and
the influence of pH value, scan rate, accumulation potential, and time also losartan concentration on
the performance of ZnO/Au/Chitosan/RGO/GCE were investigated. In order to investigate the selectivity
of the modified electrode for the determination of LOS, the effect of possible interfering
species was evaluated and showed that these species are not interferences. Also, the reproducibility
of the modified electrode was investigated and implying that the RGO/Chit/Au/ZnO nanocomposite
was highly reproducible.

Results:
The modified electrode was used as a sensor for the selective and sensitive determination of
LOS with a detection limit of 0.073 μM over the dynamic linear range of 0.5μM to 18.0 μM. In
addition, electrochemical oxidation of LOS was well recovered in pharmaceutical formulations.

Conclusion:
LOS is used to treat high blood pressure, taking into account the oxidation of this
compound, the use of electrochemical based sensors, ideally suited to a specific chemical species,
can be fully selectable and High-sensitivity answer is very important. In this study, the electrodes
with RGO/Chit/Au/ZnO nanocomposite were modified by the electrochemical method.
Nanocomposites were characterized by various methods such as FE-SEM, FT-IR, XRD, Raman, and
XPS. The electrocatalytic activity of the modified electrode was then investigated for measuring
LOS. According to the results of the modified electrode, high sensitivity, reproducibility, and
selectivity have been shown to oxidize this composition.