Label-free bioassay with graphene oxide-based fluorescent aptasensors: A review

Bioassays using a fluorophore and DNA aptamer have been extensively developed due to the ultra -sensitivity of fluorophores and recognition ability of DNA aptamers. Conventional fluorescent aptamer-based sensors (aptasensors) require chemical labeling between the fluorophore and aptamer and is technologically impracical for various sensing and assay applications. A simple mix and go strategy has been introduced that uses label-free technology as a platform for sensor development. The biosensors comprise a fluorophore, a ssDNA aptamer, and eco-friendly graphene oxide (GO). In the absence of the sensor target, GO quenches the fluorescence of the fluorophore and single-strand DNA aptamer complex. When the target is added, the DNA aptamer conformationally turns into a duplex, G-quadruplexe, or other secondary structure. This structure change leads to release of GO by the fluorophore-aptamer-target complex, generating dramatic fluorescence recovery and amplification. With this sensing method, the DNA aptamer does not need to be chemically labeled. Therefore, flexible fluorophore in-dicators and ssDNA aptamers can be used in this label-free aptasensing strategy. In this review, we discuss various unlabeled fluorophores, including synthetic small molecular fluorophores and genetically encoded fluorescent proteins, as indicators for generating GO-based fluorescent DNA aptasensors for label-free bioassay. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

Bioassays using fluorophore and DNA aptamer have been extensively developed due to the ultra-sensitivity of fluorophores and recognition ability of DNA aptamers. A label-free aptasensing strategy has been introduced, utilizing flexible fluorophore indicators and ssDNA aptamers for various sensing and assay applications. The conformational change of the DNA aptamer in the presence of the target results in dramatic fluorescence recovery and amplification.