M. Q. Israr, K. ul Hasan, J. R. Sadaf , I. Engquist, O. Nur, M. Willander and B. Danielsson
The potentiometric cholesterol biosensor based on graphene nanosheets has been successfully miniaturized. Homogeneous exfoliation of the mono- and double-layered graphene nanosheets on copper wire is achieved by drop casting the graphene nanosheets suspended in N-methyl-pyrrolidone solution. The process of physical adsorption has been utilized to immobilize the cholesterol oxidase onto graphene nanosheets. Morphological, crosssectional and structural crystallinity of the nanosheets have been investigated using atomic force microscope and transmission electron microscope. Ultraviolet-visible absorption and Fourier transform infrared spectrometers have been used to confirm the presence of the graphene nanosheets and their conjugation with cholesterol oxidase. The presented potentiometric biosensor renders effective selectivity and sensitivity (~82 mV/decade) for the detection of cholesterol biomolecules in 1 × 10−6 M to 1 × 10−3 M logarithmic range and quick output response within ~ 4 sec. The stability and reusability of the biosensor have also been investigated for the above mentioned range of cholesterol concentrations. Additionally, the functioning of presented biosensor is studied for the ranges of the temperature of 15-70 °C and pH values (4-9).
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