Aptasensors with palladium nanoparticle-modified hemin-containing metal-organic frameworks as the signal marker for detection of exosomes.

ABSTRACT

Zr-metal-organic frameworks (Zr-MOFs) have received increasing interest for their use as the signal marker in the development of sandwich-structured aptasensors for the detection of exosomes. However, Zr4+ ions of the Zr-MOFs can interact with not only the exosomes, but also the aptamers, leading to possible false positives and a large background response. In the present study, we report for the first time aptasensors with Pd nanoparticle (NP)-decorated and hemin-embedded UiO-66 MOFs serving as the signal amplification marker to eliminate false positives and decrease the background response of aptasensors. To construct aptasensors for detection of exosomes, CD63-specific aptamers were tethered onto magnetic Fe3O4 particles coated with polydopamine (PDA) and UiO-66-NH2 using glutaraldehyde crosslinking for capturing the exosomes. To prepare highly catalytic Zr-MOF-based signal markers, UiO-66 MOFs were modified with hemin followed by Pd NPs. The as-prepared Pd-decorated hemin-embedded MOFs showed high catalytic activity towards the chromogenic oxidation reaction of TMB by H2O2. Moreover, the decoration with Pd NPs led to the change of the surface charge state of the catalytic hemin-embedded UiO-66 MOFs from positive to negative, weakening the interaction between the signal marker and the negatively charged aptamers. Therefore, the as-prepared aptasensors showed an improved sensing performance towards exosomes with a linear concentration range from 4.28 × 102 to 4.28 × 105 and a limit of detection (LOD) of 86.2 particles per µL. The as-prepared aptasensors also showed high sensitivity and selectivity to the exosomes from different origins including the HeLa cell line and MCF-7 cell line.