DNA treatment of metal nanoparticles provides a potent tool for tuning their native properties and constructing advanced materials. However, there have been limited studies on interactions between DNA and nanomaterial-based artificial enzymes (nanozymes) to influence their intrinsic peroxidase-like properties. Here, we present the utilization of DNA as a capping ligand to engineer various bio-nanointerfaces for high-precise and adjustable regulation of catalytic behaviors of nanozymes toward the oxidation of substrates. The treatment of stiff double-stranded DNA only induced a negligible enhancement of the catalytic activity of nanozymes, and both coil-like single-stranded DNA and hairpin DNA-capped nanoparticles produced a medium signal increase. Interestingly, hybridization chain reaction (HCR) product-treated nanoparticles showed the highest peroxidase-like activities among four DNA structures. Furthermore, significant parameters that influence HCR process and the modulation of catalysis, such as the concentration of the hairpin DNA, the ionic strength, and the amount of nanozyme, were also systematically investigated. On the basis of HCR amplification and iron oxide (Fe3O4) nanoparticles, we develop a simple, fast, label-free, and sensitive colorimetric strategy for sensing of a Yersinia pestis-relevant DNA sequence with a detection limit as low as 100 pM as well as single nucleotide polymorphism discrimination. These results highlight DNA engineering as a facile strategy to regulate the catalytic activities of nanozymes and understand the interactions between metallic nanoparticles and nucleic acids for biosensing applications.
In this study, a rapid, low-cost and facile method for detecting exosomes was developed by engineering DNA ligands on the surface of an iron-based metal–organic framework (Fe-MOF). Aptamers of exosomal transmembrane CD63 protein (CD63-aptamers) were utilized as both the optically active layer and the exosome-specific recognition element to engineer an Fe-MOF bio-interface for high-efficiency regulation of the catalytic behavior of Fe-MOF toward the chromogenic substrate. The effective enhancement of the intrinsic peroxidase-like catalytic activity was confirmed via the self-assembly of CD63-aptamers on the surface of Fe-MOF. The specific binding of exosomes with CD63-aptamers altered the conformation of DNA ligands on the surface of Fe-MOF, contributing to sensitive variation in Fe-MOF catalytic activity. This directly produced a distinct color change and enabled the visual detection of exosomes. Via one-step “mixing-and-detection”, the Fe-MOF bio-interface exhibited excellent performance in quantitative analysis of exosomes derived from human breast cancer cell lines ranging from 1.1 × 10 5 to 2.2 × 10 7 particles/μL with a detection limit of 5.2 × 10 4 particles/μL. The expression of exosomal CD63 proteins originated from three types of cancer cell lines, including breast cancer, gastric cancer and lung cancer cell lines, was differentiated within only 17 min. Furthermore, the method was successfully applied to the identification of exosomes in serum samples, suggesting its potential in clinical analysis as a valuable tool for the rapid, convenient and economical testing of exosomes.
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