Promiscuous dye binding by a light-up aptamer: application for label-free multi-wavelength biosensing

A self-assembling split aptamer multiplex assay for SARS-COVID19 and miniaturization of a malachite green DNA-based aptamer

Multiplex assays often rely on expensive sensors incorporating covalently linked fluorescent dyes. Herein, we developed a self-assembling aptamer-based multiplex assay. This multiplex approach utilizes a previously established split aptamer sensor in conjugation with a novel split aptamer sensor based upon a malachite green DNA aptamer. This system was capable of simultaneous fluorescent detection of two SARS COVID-19-related sequences in one sample with individual sensors that possesses a limit of detection (LOD) in the low nM range. Optimization of the Split Malachite Green (SMG) sensor yielded a minimized aptamer construct, Mini-MG, capable of inducing fluorescence of malachite green in both a DNA hairpin and sensor format.

A Washing-Free and Easy-to-Operate Fluorescent Biosensor for Highly Efficient Detection of Breast Cancer-Derived Exosomes

Traditional detection methods for protein tumor markers in the early screening of breast cancer are restricted by complicated operation procedures and unstable reproducibility. As one of alternative emerging tumor markers, exosomes play an important role in diagnosing and treating cancers at the early stage due to traceability of their origins and great involvement in occurrence and development of cancers. Herein, a washing-free and efficient fluorescent biosensor has been proposed to realize simple and straightforward analysis of breast cancer cell-derived exosomes based on high affinity aptamers and G quadruplex-hemin (G4-hemin). The whole reaction process can be completed by several simple steps, which realizes washing-free and labor-saving. With simplified operation procedures and high repeatability, the linear detection range for this developed fluorescent biosensing strategy to breast cancer cell-derived exosomes is from 2.5 × 10⁵ to 1.00 × 10⁷ particles/ml, and the limit of detection is down to 0.54 × 10⁵ particles/ml.

MicroRNA detection in biologically relevant media using a split aptamer platform

MicroRNA (miRNA)-based intercellular communication has been implicated in many functional and dysfunctional biological processes. This has raised interest in the potential use of miRNAs as biomarkers for diagnosis and prognosis. Though the list of clinically significant miRNA biomarkers is expanding, it remains challenging to adapt current chemical tools to investigate miRNAs in complex environments native to cells and tissues. We describe here a methodology for rapidly developing aptamer-based fluorescent biosensors that can specifically detect miRNAs in biologically relevant media (10-30% v/v), including medium collected from cultured HeLa cells, human serum, and human plasma. This methodology involves the semi-rational design of the hybridization between DNA oligonucleotides and the miRNA target to build a pool of potential aptamers, and the screening of this pool for high signal-to-background ratio and target specificity. The DNA oligonucleotides are readily available and require no chemical modification, rendering these chemical tools highly adaptable to any novel and niche miRNA target. Following this approach, we developed sensors that detect distinct oncogenic miRNA targets (miR-19b, miR-21, and miR-92a) at concentrations as low as 5 nM without amplification and are selective against single-nucleotide mutants. This work provides a systematic approach toward the development of miRNA biosensors that are easily accessible and can perform in biological environments with minimal sample handling.