Abstract
We report the preparation of poly (propylene imine) dendrimer (PPI) and CdTe/CdSe/ZnSe
quantum dots (QDs) as a suitable platform for the development of an enzyme-based electrochemical
cholesterol biosensor with enhanced analytical performance. The mercaptopropionic acid (MPA)-capped
CdTe/CdSe/ZnSe QDs was synthesized in an aqueous phase and characterized using photoluminescence
(PL) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, transmission electron microscopy
(TEM), X-ray power diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy. The absorption
and emission maxima of the QDs red shifted as the reaction time and shell growth increased,
indicating the formation of CdTe/CdSe/ZnSe QDs. PPI was electrodeposited on a glassy carbon
electrode followed by the deposition (by deep coating) attachment of the QDs onto the PPI dendrimer
modified electrode using 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC), and
N-hydroxysuccinimide (NHS) as a coupling agent. The biosensor was prepared by incubating the
PPI/QDs modified electrode into a solution of cholesterol oxidase (ChOx) for 6 h. The modified
electrodes were characterized by voltammetry and impedance spectroscopy. Since efficient electron
transfer process between the enzyme cholesterol oxidase (ChOx) and the PPI/QDs-modified electrode
was achieved, the cholesterol biosensor (GCE/PPI/QDs/ChOx) was able to detect cholesterol in the
range 0.1–10 mM with a detection limit (LOD) of 0.075 mM and sensitivity of 111.16 µA mM−1 cm−2.
The biosensor was stable for over a month
and had greater selectivity towards the cholesterol molecule.