Gold-Nanoparticle-Functionalized Cobalt–Nickel Phosphate 3D Nanoice Creams to Fabricate Stable and Sensitive Biosensors for the Cytochrome c Assay

Designing a stable and sensitive luminol-based electrochemiluminescence (ECL) analytical platform in the neutral condition has attracted a lot of attention. Here, gold-nanoparticle-functionalized cobalt–nickel phosphate three-dimensional nanoice creams (Au@Co3Ni3(PO4)4 NICs) are successfully prepared via electrostatic interaction. Generally, cobalt–nickel phosphate nanoice creams (Co3Ni3(PO4)4 NICs) are synthesized via a mild hydrothermal method and functionalized via polyethylenimine (PEI). Then, Au NPs are adsorbed on the surface of Co3Ni3(PO4)4 NICs via Au–N weak interaction to fabricate Au@Co3Ni3(PO4)4 NICs. Owing to the important roles of Au@Co3Ni3(PO4)4 in exhibiting excellent electrocatalytic activity, as well as preventing the deposition of negatively charged oxidation product induced electrode passivation, luminol in the nanohybrids (LH-Au@Co3Ni3(PO4)4) gives strong and stable ECL intensity in the neutral conditions. Moreover, the ECL emission of luminol is obviously quenched based on the resonance energy transfer (RET) between luminol as donor and cytochrome c (Cyt c) as acceptor. Hence, a sensitive ECL biosensor is successfully fabricated for the quantitative determination of Cyt c in cell lysates and exhibits wide linear ranges of 1.0 × 10–4–0.5 × 10–5 and 0.5 × 10–5–1.0 × 10–8 M as well as a low detection limit of 2.48 nM. This novel sensing strategy will broaden the application of transition metal (Co, Ni) phosphates in bioassays.