Surface plasmon resonance assay for exosomes based on aptamer recognition and polydopamine-functionalized gold nanoparticles for signal amplification

A novel surface plasmon resonance (SPR) strategy is introduced for the specific determination of exosomes based on aptamer recognition and polydopamine-functionalized gold nanoparticle (Au@PDA NP)–assisted signal amplification. Exosomes derived from hepatic carcinoma SMMC-7721 were selected as the model target. SMMC-7721 exosomes can be specifically captured by the aptamer ZY-sls that was complementary to the DNA tetrahedron probes (DTPs), and then the CD63 aptamer–linked Au@PDA NPs recognized SMMC-7721 exosomes for signal amplification. The DTPs were modified on a Au film for preventing Au deposition on the surface during the introduction of HAuCl4, and PDA coated on the AuNPs was used to reduce HAuCl4 in situ without any reductant assistance. It results in a further enhanced SPR signal. The assay can clearly distinguish SMMC-7721 exosomes from others (HepG2 exosomes, Bel-7404 exosomes, L02 exosomes, MCF-7 exosomes, and SW480 exosomes, respectively). SMMC-7721 exosomes are specifically determined as low as 5.6 × 105 particles mL−1. The method has successfully achieved specific determination of SMMC-7721 exosomes even in 50% of human serum without any pretreatment.