Comparison of Sensitivity and Quantitation between Microbead Dielectrophoresis-Based DNA Detection and Real-Time PCR

New Approaches to Plant Pathogen Detection and Disease Diagnosis

Detecting plant pathogens and diagnosing diseases are critical components of successful pest management. These key areas have undergone significant advancements driven by breakthroughs in molecular biology and remote sensing technologies within the realm of precision agriculture. Notably, nucleic acid amplification techniques, with recent emphasis on sequencing procedures, particularly next-generation sequencing, have enabled improved DNA or RNA amplification detection protocols that now enable previously unthinkable strategies aimed at dissecting plant microbiota, including the disease-causing components. Simultaneously, the domain of remote sensing has seen the emergence of cutting-edge imaging sensor technologies and the integration of powerful computational tools, such as machine learning. These innovations enable spectral analysis of foliar symptoms and specific pathogen-induced alterations, making imaging spectroscopy and thermal imaging fundamental tools for large-scale disease surveillance and monitoring. These technologies contribute significantly to understanding the temporal and spatial dynamics of plant diseases.

Micro and Nanoscale Technologies for Diagnosis of Viral Infections

Viral infection is one of the leading causes of mortality worldwide. The growth of globalization significantly increases the risk of virus spreading, making it a global threat to future public health. In particular, the ongoing coronavirus disease 2019 (COVID-19) pandemic outbreak emphasizes the importance of devices and methods for rapid, sensitive, and cost-effective diagnosis of viral infections in the early stages by which their quick and global spread can be controlled. Micro and nanoscale technologies have attracted tremendous attention in recent years for a variety of medical and biological applications, especially in developing diagnostic platforms for rapid and accurate detection of viral diseases. This review addresses advances of microneedles, microchip-based integrated platforms, and nano- and microparticles for sampling, sample processing, enrichment, amplification, and detection of viral particles and antigens related to the diagnosis of viral diseases. Additionally, methods for the fabrication of microchip-based devices and commercially used devices are described. Finally, challenges and prospects on the development of micro and nanotechnologies for the early diagnosis of viral diseases are highlighted.

The Requirement of Genetic Diagnostic Technologies for Environmental Surveillance of Antimicrobial Resistance

Antimicrobial resistance (AMR) is threatening modern medicine. While the primary cost of AMR is paid in the healthcare domain, the agricultural and environmental domains are also reservoirs of resistant microorganisms and hence perpetual sources of AMR infections in humans. Consequently, the World Health Organisation and other international agencies are calling for surveillance of AMR in all three domains to guide intervention and risk reduction strategies. Technologies for detecting AMR that have been developed for healthcare settings are not immediately transferable to environmental and agricultural settings, and limited dialogue between the domains has hampered opportunities for cross-fertilisation to develop modified or new technologies. In this feature, we discuss the limitations of currently available AMR sensing technologies used in the clinic for sensing in other environments, and what is required to overcome these limitations.

Simple microfluidic device for detecting the negative dielectrophoresis of DNA labeled microbeads

We propose a new microfluidic device that can be used to determine the change in the negative dielectrophoresis (n-DEP) of dielectric microbeads when a small amount of DNA is attached to them. We previously proposed a DNA detection method based on changes in the DEP of microbeads induced by the attachment of DNA. When target DNA is attached to the microbeads having n-DEP property, the DEP changes from negative to positive. This occurs because electric charges of the DNA increase the surface conductance of the microbeads. Thus, only the DNA-labeled microbeads are attracted to a microelectrode by positive DEP. The trapped DNA-labeled microbeads can be counted by dielectrophoretic impedance measurements. A large amount of DNA (approximately 10⁵ DNA molecules) is required to change the DEP from negative to positive. Even though this method can be combined with DNA amplification, reducing the amount of DNA required can help us to shorten the reaction time. In this study, we aimed to detect DNA less than 10⁵ DNA molecules by determining the change in the n-DEP change. To achieve this, we proposed a simple microfluidic device consisting of a single microchannel and a single pair of microelectrodes. Numerical simulations revealed that the device can identify the slight change in the n-DEP of the microbeads corresponding to the attachment of a small amount of DNA. In practical experiments, the fabricated device distinguished 10-1000 DNA molecules per microbead. This method represents a fast and easy method of DNA detection when combined with DNA amplification techniques.

Dielectrophoresis Manipulation: Versatile Lateral and Vertical Mechanisms

Discussing the topic of the capability of dielectrophoresis (DEP) devices in terms of the selective detection and rapid manipulation of particles based on the DEP force (F_DEP) via contactless methods is challenging in medical research, drug discovery and delivery. Nonetheless, the process of the selective detection and rapid manipulation of particles via contactless DEP based on dielectric particles and the surrounding medium can reduce the effects of major issues, including physical contact with the particles and medium contamination to overcome operational difficulties. In this review, DEP microelectromechanical system (MEMS) microelectrodes with a tapered profile for the selective detection and rapid manipulation of particles were studied and compared with those of conventional designs with a straight-cut profile. The main objective of this manuscript is to review the versatile mechanism of tapered DEP MEMS microelectrodes for the purpose of selective detection and rapid manipulation. Thus, this review provides a versatile filtration mechanism with the potential for a glomerular-based membrane in an artificial kidneys’ development solution for implementing engineered particles and cells by lateral attraction as well as vertical repulsion in the development of lab-on-a-chip applications. For tapered DEP MEMS microelectrodes, the scope of this study methodology involved the characterisation of DEP, modelling of the polarisation factor and the dynamic dielectric changes between the particles and medium. Comprehensive discussions are presented on the capability of tapered DEP microelectrodes to drive the selected particles and the simulation, fabrication and testing of the tapered profile. This study revealed an outstanding performance with the capability of producing two regions of high electric field intensity at the bottom and top edges of the side wall of tapered microelectrodes. Observations on particle separation mainly by the lateral attraction force of particles with positive DEP on the y-axis and vertical repulsion force of particles with negative DEP on the z-axis proved an efficient and uniform F_DEP produced by tapered electrodes. In conclusion, this study confirmed the reliability and efficiency of the tapered DEP microelectrodes in the process of selective detection and rapid manipulation at a higher efficiency rate than straight-cut microelectrodes, which is significant in DEP technology applications.

Fast and sensitive isothermal DNA assay using microbead dielectrophoresis for detection of anti-microbial resistance genes

Antimicrobial resistant pathogens are a growing worldwide threat to human health. This study describes a novel method for rapid and sensitive detection of antimicrobial resistance (AMR) genes, specifically bla_CTX-M-15 which encodes for the enzyme that offers resistance to extended spectrum β-lactam antibiotics. The method combines isothermal DNA amplification by recombinase polymerase amplification (RPA), with microbead dielectrophoresis (DEP)-based DNA detection. The RPA amplicon is captured onto dielectric microbeads, and the amount of amplicon determined by dielectrophoretic impedance measurement (DEPIM) of the microbeads. Amplicon-labeled microbeads were prepared by either a two-step or one-step method. A purified recombinant plasmid containing bla_CTX-M-15 and genomic DNA (with plasmid) extracted from an AMR bacteria (Escherichia coli NCTC 13441) were used as target samples. A one-step method in which RPA and DNA immobilization on the microbeads is carried out simultaneously, has a detection limit of 2 copies/reaction for pure plasmid and 50 copies/reaction for genomic DNA. The assays are quantitative with a dynamic range up to 10⁵ copies/reaction, with a total detection time of 26 min. Both methods are easy, rapid, and unlike lateral flow detection are quantitative.