Sensitive Insulin Detection based on Electrogenerated Chemiluminescence Resonance Energy Transfer between Ru(bpy)₃²⁺ and Au Nanoparticle-Doped β-Cyclodextrin-Pb (II) Metal–Organic Framework

A novel sandwich-type electrochemiluminescent (ECL) biosensor based on ECL resonance energy transfer (RET) was developed for the determination of insulin. Au nanoparticle-doped Pb(II)-β-cyclodextrin (Pb-β-CD) metal–organic framework was exploited as an ECL donor and chitosan/Ru(bpy) 3 2+ /silica nanoparticles (CRuSi NPs) were employed as ECL acceptor. Pb-β-CD shows excellent ECL behavior and unexpected reducing ability toward AuCl 4 – . Au nanoparticles could massively form on the surface of Pb-β-CD (Au@Pb-β-CD) without use of any additional reducing agent. In the presence of co-reactant K 2 S 2 O 8, the ECL emission of Pb-β-CD was enhanced by the formation of Au nanoparticles, which is desirable for the construction of a RET immunosensor. The absorption spectra of the synthesized CRuSi NPs show great overlaps with the ECL spectra of Pb-β-CD. This enabled the ECL-RET by incorporating Au@Pb-β-CD and CRuSi NPs into electrode surfaces. The immunosensor is fabricated using Au@Pb-β-CD as sensing platform and CRuSi NPs as labels of antibodies. After the optimization of determination conditions, a linear response range for insulin from 0.1 pg mL –1 to 10.0 ng mL –1 was obtained, and the limit of detection was calculated to be 0.042 pg mL –1 (S/N = 3). The prepared insulin biosensor displayed excellent stability and good specificity.