Detection of Cd²⁺ and Pb²⁺ using amyloid oligomer–reduced graphene oxide composite

Heavy metal ions are toxic to humans and can further interact with amyloid in the human body to produce amyloid plaques, which disrupt neurotransmitter function and are linked to Alzheimer's and Parkinson's diseases. In this study, we developed an amyloid oligomer–reduced graphene oxide composite (AOrGOC) electrochemical sensor for effective heavy metal ion detection based on square-wave anodic stripping voltammetry. The reactivity between amyloids and heavy metal ions was studied by analyzing the stripping current for different amyloids (lysozyme, bovine serum albumin, and β-lactoglobulin) and amyloid growth types (monomers, oligomers, and fibrils). Reduced graphene oxide was used to improve the sensitivity of the sensor. The AOrGOC sensor exhibited the detection limits of 86.0 and 9.5 nM for Cd²⁺ and Pb²⁺, respectively, and selectively detected Cd²⁺ and Pb²⁺ over other heavy metal ions. The AOrGOC sensor also detected Cd²⁺ and Pb²⁺ in human plasma, thus exhibiting its potential as a biosensor. This study not only promoted our fundamental understanding of amyloids and the detection of heavy metal ions using amyloids, but also provided valuable insights into amyloid-based electrochemical sensors.