A label-free, highly reproducible, sensitive, and selective biosensor is proposed using antiapolipoprotein B 100 (AAB) functionalized mesoporous few-layer reduced graphene oxide and nickel oxide (rGO-NiO) nanocomposite for detection of low density lipoprotein (LDL) molecules. The formation of mesoporous rGO-NiO composite on indium tin oxide conductive electrode has been accomplished via electrophoretic technique using colloidal suspension of rGO sheets and NiO nanoparticles. This biosensor shows good stability obtained by surface conjugation of antibody AAB molecules with rGO-NiO matrix by EDC-NHS coupling chemistry. The defect-less few layer rGO sheets, NiO nanoparticles (nNiO) and formation of nanocomposite has been confirmed by Raman mapping, electron microscopic studies, X-ray diffraction, and electrochemical techniques. The synthesized rGO-NiO composite is mesoporous dominated with a small percentage of micro and macroporous structure as is evident by the results of Brunauer-Emmett-Teller experiment. Further, the bioconjugation of AAB with rGO-NiO has been investigated by Fourier transform-infrared spectroscopy studies. The kinetic studies for binding of antigen-antibody (LDL-AAB) and analytical performance of this biosensor have been evaluated by the impedance spectroscopic method. This biosensor exhibits an excellent sensitivity of 510 Ω (mg/dL)(-1) cm(-2) for detection of LDL molecules and is sensitive to 5 mg/dL concentration of LDL in a wide range of 0-130 mg/dL. Thus, this fabricated biosensor is an efficient and highly sensitive platform for the analysis of other antigen-antibody interactions and biomolecules detection.
Keywords: impedance spectroscopy; label-free; low density lipoprotein; mesoporosity; nickel oxide nanoparticles; reduce graphene oxide.