Label-free Electrochemical Detection of CGG Repeats on Inkjet Printable 2D Layers of MoS₂

Abstract

Flexible and ultrasensitive biosensing platforms capable of detecting a large number of trinucleotide repeats (TNRs) are crucial for future technology development needed to combat a variety of genetic disorders. For example, trinucleotide CGG repeat expansions in the FMR1 gene can cause Fragile X syndrome (FXS) and Fragile X-associated tremor/ataxia syndrome (FXTAS). Current state-of-the-art technologies to detect repeat sequences are expensive, while relying on complicated procedures, and prone to false negatives. We reasoned that two-dimensional (2D) molybdenum sulfide (MoS2) surfaces may be useful for label-free electrochemical detection of CGG repeats due to its high affinity for guanine bases. Here, we developed a low-cost and sensitive wax-on-plastic electrochemical sensor using 2D MoS2 ink for the detection of CGG repeats. The ink containing few-layered MoS2 nanosheets was prepared and characterized using optical, electrical, electrochemical, and electron microscopic methods. The devices were characterized by electron microscopic and electrochemical methods. Repetitive CGG DNA was adsorbed on a MoS2 surface in a high cationic strength environment and the electrocatalytic current of the CGG/MoS2 interface was recorded using a soluble Fe­(CN)6 –3/–4 redox probe by differential pulse voltammetry (DPV). The dynamic range for the detection of prehybridized duplexes ranged from 1 aM to 100 nM with a 3.0 aM limit of detection. A detection range of 100 fM to 1 nM was recorded for surface hybridization events. Using this method, we were able to observe selectivity of MoS2 for CGG repeats and distinguish nonpathogenic from disease-associated repeat lengths. The detection of CGG repeat sequences on inkjet printable 2D MoS2 surfaces is a forward step toward developing chip-based rapid and label-free sensors for the detection of repeat expansion sequences.

PNA microprobe for label-free detection of expanded trinucleotide repeats

“…The detection of DNA repeat expansions has been challenging owing to their length and complex structures they can form. 2,3 Despite the high sensitivity of the electrochemical techniques, down to attomolar level, 4,5 there have been very few efforts to detect expanded repeats. Most of the methods relied on chemical labelling or detecting short target lengths (maximum 10 repeats).…”

Sequence-Independent DNA Adsorption on Few-Layered Oxygen-Functionalized Graphene Electrodes: An Electrochemical Study for Biosensing Application

“…The upward trend of the current response with respect to length indicates that the increase in DNA adsorption aided by Mg 2+ facilitates the charge transport at the interface. This length-dependent current response may lead to sensitive and label-free discrimination of normal and abnormal lengths of DNA repeat sequences associated with neurodegenerative diseases, as reported recently on MoS 2 nanosheets surfaces [44]. Then, we tested the adsorption of various single-stranded, double-stranded, and noncomplementary sequences of same length (i.e., 8 trinucleotide repeats or 24 nucleotides) at 10 nM concentration.…”

DNA interfaces with dimensional materials for biomedical applications

“…6e. 86 These platforms can be easily fabricated through desktop wax and inkjet printers. [87][88][89] Specically, it was demonstrated that physisorbed DNA improves the electrochemical property of MoS 2 electrodes, because it reduces the bandgap of the MoS 2 .…”