Double imprinting-based electrochemical detection of mimetic exosomes

Exosomes (30–150 nm) secreted by cells play an important role in intercellular communication. Herein, a novel double imprinting-based electrochemical method has been developed for analyzing the particle size distribution (PSD) of mimetic exosomes – a mixture of SiO₂@HRP with the diameters in 50 nm, 100 nm and 150 nm at a ratio similar to the exosomes. Double imprinting polymers (DIP) were synthesized with SiO₂@HRP at different sizes as template, providing the both recognition of size and morphology. With the capture of the target and the binding of the signal amplification tag – SiO₂@Ag/MPBA on the DIP film, a sandwich structure was constructed on Au NPs-GO modified glassy carbon electrode. Under the optimal conditions, the DIP film exhibits the linear correlations between the current intensity and the logarithmic concentration of SiO₂@HRP as ΔI₅₀ = −1.52 + 0.50 × lgc₅₀ (2.89 × 10⁴–2.89 × 10⁹ particles/mL), ΔI₁₀₀ = −1.61 + 0.48 × lgc₁₀₀ (2.89 × 10⁴–2.89 × 10⁹ particles/mL) and ΔI₁₅₀ = −1.54 + 0.49 × lgc₁₅₀ (5.75 × 10⁴–5.75 × 10⁹ particles/mL) with the limit of detection of 1.44 × 10³ particles/mL, 5.68 × 10² particles/mL and 7.70 × 10² particles/mL, respectively. Furthermore, the DIP film was applied to the PSD analysis of mimetic exosomes – SiO₂@HRP at mixed sizes with a ratio of 50 nm:100 nm:150 nm = 5.0%:42.5%:52.5% detected by nanoparticle tracking analysis (NTA), obtaining a similar result of 50 nm:100 nm:150 nm = 3.6%:43.0%:53.4% with small relative concentration errors. It also exhibited excellent reproducibility and stability. This double imprinting-based method shows high potential in the separation and detection of complex biosamples.