Characterization and application of fluidic properties of trinucleotide repeat sequences by wax-on-plastic microfluidics

PNA microprobe for label-free detection of expanded trinucleotide repeats

We present a PNA microprobe sensing platform to detect trinucleotide repeat mutation by electrochemical impedance spectroscopy. The microprobe platform discriminated Huntington's disease-associated CAG repeats in cell-derived total RNA with S/N 1 : 3. This sensitive, label-free, and PCR-free detection strategy may be employed in the future to develop biosensing platforms for the detection of a plethora of repeat expansion disorders.

DNA interfaces with dimensional materials for biomedical applications

DNA interfaces with nano, micro, and macro materials have gained widespread attention for various applications. Such interfaces exhibit distinct functions and properties not only due to the unique properties of interfacing materials but also sequence- and conformation-dependent characteristics of the DNA. Therefore, DNA interfaces with diverse dimensional materials have advanced our understanding of the interaction mechanisms and the properties of such interfaces. The unique interfacial properties of such novel materials have applications in nanotechnology, biophysics, cell biology, biosensing, and bioelectronics. The field is growing rapidly with the frequent emergence of new interfaces carrying remarkable interfacial character. In this review article, we have classified the DNA interfaces into 0D, 1D, 2D, and 3D categories based on the types of dimensional materials. We review the key efforts made in the last five years and focus on types of interfaces, interfacing mechanisms, and their state-of-the-art applications. This review will draw a general interest because of the diversity in the DNA materials science but also the unique applications that will play a cutting-edge role in biomedical and biosensing research.

DNA interfaces with 0–3 dimensional materials through physisorption and chemisorption mechanisms acquire unique interfacial character for novel biomedical applications.

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

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.

Desktop Fabrication of Lab-On-Chip Devices on Flexible Substrates: A Brief Review

Flexible microfluidic devices are currently in demand because they can be mass-produced in resource-limited settings using simple and inexpensive fabrication tools. Finding new ways to fabricate microfluidic platforms on flexible substrates has been a hot area. Integration of customized detection tools for different lab-on-chip applications has made this area challenging. Significant advancements have occurred in the area over the last decade; therefore, there is a need to review such interesting fabrication tools employed on flexible substrates, such as paper and plastics. In this short review, we review individual fabrication tools and their combinations that have been used to develop such platforms in the past five years. These tools are not only simple and low-cost but also require minimal skills for their operation. Moreover, key examples of plastic-based flexible substrates are also presented, because a diverse range of plastic materials have prevailed recently for a variety of lab-on-chip applications. This review should attract audience of various levels, i.e., from hobbyists to scientists, and from high school students to postdoctoral researchers, to produce their own flexible devices in their own settings.

Unique sequence-dependent properties of trinucleotide repeat monolayers: electrochemical, electrical, and topographic characterization

The sequence-dependent properties of the surface-assembled trinucleotide repeat interface on a gold surface were explored by electrochemical methods and surface probe microscopy.