Single vs sandwich aptamers: Towards the detection of human epidermal growth factor receptor 2 using composites of phthalocyanine and nanoparticles

Abstract

The superiority of the sandwich over a single aptamer based aptasensor assay for the detection of the human epidermal growth factor receptor 2 (HER2) is demonstrated for the first time. Cobalt tris-3,5 dimethoxy-phenoxy pyridine (5) oxy (2)- carboxylic acid phthalocyanine (CoMPhPyCPc) and sulphur/nitrogen doped graphene quantum dots (SNGQDs) and cerium oxide nanoparticles (CeO₂NPs) nanocomposite (SNGQDs@CeO₂NPs) were used for electrode modification of glassy carbon electrode (GCE) both individually and combined to form the substrates: GCE/SNGQDs@CeO₂NPs, GCE/CoMPhPyCPc and GCE/SNGQDs@CeO₂NPs/CoMPhPyCPc. The designed substrates were used as immobilization platforms for the amino functionalized HB5 aptamer for the development of both single and sandwich aptasensor assays. A novel bioconjugate, made of the HB5 aptamer and nanocomposite (HB5-SNGQDs@CeO₂NPs) was fabricated, and characterized using ultra-violet/visible, Fourier transform infrared, and Raman spectroscopies as well as scanning electron microscopy. HB5-SNGQDs@CeO₂NPs was applied as a secondary aptamer in the design of novel sandwich assays towards the electrochemical detection of HER2. The performance of the designed aptasensors were evaluated using electrochemical impedance spectroscopy. The sandwich assay gave low limit of detection of 0.00088 pg/mL, high sensitivity of 773925 Ω pg^-1mL, showed stability, and good precision in real samples towards HER2 detection.

Keywords: CeO(2) nanoparticles; Co phthalocyanine; Electrochemical impedance spectroscopy; Graphene quantum dots; Human Epidermal Growth Factor 2; Sandwich aptasensor.