Simultaneous Preconcentration and Separation of Native Protein Variants Using Thermal Gel Electrophoresis

Controllable concentric electric field line distribution for simultaneous separation of DNA

An approach for the controllable separation and concentration of nucleic acid using a circular nonuniform electric field was proposed and developed. Using six different lengths of DNA molecules as standard samples, the distribution of the gradient electric field was increased from the outer circular electrode to the inner rod-shaped electrode, contributing to the migration of DNA molecules at a velocity gradient towards the region with the strongest inner electric field. The DNA molecules were arranged in a distribution of concentric circles that aligned with the distribution of concentric equipotential lines. The concentration of DNA multiplied with the alternation of radius. As a result, this platform allowed simultaneous DNA separation, achieving a resolution range of 1.17-3.03 through an extended electrophoresis time, resulting in enhanced concentration factors of 1.08-6.27. Moreover, the manipulation of the relative height of the inner and outer electrodes enabled precise control over the distribution and the deflection degree of electric field lines, leading to accurate control over DNA deflection.

Electrophoretic Microplate Protein Identification Based on Gold Staining of Molybdenum Disulfide Hydrogels

Numerous high-performance nanotechnologies have been developed, but their practical applications are largely restricted by the nanomaterials' low stabilities and high operation complexity in aqueous substrates. Herein, we develop a simple and high-reliability hydrogel-based nanotechnology based on the in situ formation of Au nanoparticles in molybdenum disulfide (MoS2)-doped agarose (MoS2/AG) hydrogels for electrophoresis-integrated microplate protein recognition. After the incubation of MoS2/AG hydrogels in HAuCl4 solutions, MoS2 nanosheets spontaneously reduce Au ions, and the hydrogels are remarkably stained with the color of as-synthetic plasmonic Au hybrid nanomaterials (Au staining). Proteins can precisely mediate the morphologies and optical properties of Au/MoS2 heterostructures in the hydrogels. Consequently, Au staining-based protein recognition is exhibited, and hydrogels ensure the comparable stabilities and sensitivities of protein analysis. In comparison to the fluorescence imaging and dye staining, enhanced sensitivity and recognition performances of proteins are implemented by Au staining. In Au staining, exfoliated MoS2 semiconductors directly guide the oriented growth of plasmonic Au nanostructures in the presence of formaldehyde, showing environment-friendly features. The Au-stained hydrogels merge the synthesis and recognition applications of plasmonic Au nanomaterials. Significantly, the one-step incubation of the electrophoretic hydrogels leads to high simplicity of operation, largely challenging those multiple-step Ag staining routes which were performed with high complexity and formaldehyde toxicity. Due to its toxic-free, simple, and sensitive merits, the Au staining integrated with electrophoresis-based separation and microplate-based high-throughput measurements exhibits highly promising and improved practicality of those developing nanotechnologies and largely facilitates in-depth understanding of biological information.

A review of electrophoretic separations in temperature-responsive Pluronic thermal gels

Gel electrophoresis is a ubiquitous bioanalytical technique used in research laboratories to validate protein and nucleic acid samples. Polyacrylamide and agarose have been the gold standard gel materials for decades, but an alternative class of polymer has emerged with potentially superior performance. Pluronic thermal gels are water-soluble polymers that possess the unique ability to undergo a change in viscosity in response to changing temperature. Thermal gels can reversibly convert between low-viscosity liquids and high-viscosity solid gels using temperature as an adjustable parameter. The properties of thermal gels provide unmatched flexibility as a dynamic separations matrix to measure analytes ranging from small molecules to cells. This review article describes the physical and chemical properties of Pluronic thermal gels to provide a fundamental overview of polymer behavior. The performance of thermal gels is then reviewed to highlight their applications as a gel matrix for electrokinetic separations in capillary, microfluidic, and slab gel formats. The use of dynamic temperature-responsive gels in bioanalytical separations is an underexplored area of research but one that holds exciting potential to achieve performance unattainable with conventional static polymers.

Selective miRNA quantitation with high-temperature thermal gel electrophoresis

MicroRNAs (miRNAs) are short non-coding RNAs that control gene expression and correlate to the prognosis of numerous diseases. To support research efforts elucidating the roles of miRNAs in pathogenesis, rapid and inexpensive analytical methods are required to quantify miRNAs from biological samples. The challenge of developing new analyses with these time and cost constraints is compounded by the short sequence lengths and high degrees of homology between miRNAs that hinder detection selectivity. This report describes the development of a high-temperature thermal gel electrophoresis (TGE) method to rapidly quantify miRNAs with single-nucleotide resolution using low-cost microfluidic devices. Fluorescent probes were designed for three miRNAs that differed in sequence by one or two nucleotides. A microfluidic analysis was optimized to enrich miRNA-probe hybrids into a high-concentration band and then automatically initiate a separation to resolve each species. Analyses conducted at 30 °C exhibited significant off-target hybridization, as the different-yet-structurally-similar miRNAs bound to each probe, which biased measurements. To overcome this problem, the stability of thermal gels at elevated temperatures was exploited to conduct analyses. At 50 °C, off-target hybrids melted to prevent their detection without impeding the enrichment or separation of on-target hybrids. Selectivity studies validated that high-temperature TGE prevented off-target hybrids from interfering with the quantitative responses of the target miRNAs. This work demonstrates that TGE affords rapid, highly selective analyses of structurally similar miRNAs in low-complexity microfluidic devices, which is expected to facilitate diverse biomedical research.

Controlling the separation of native proteins with temperature in thermal gel transient isotachophoresis

Polyacrylamide gel electrophoresis (PAGE) is a ubiquitous technique used in biochemical research laboratories to characterize protein samples. Despite its popularity, PAGE is relatively slow and provides limited separation resolution, especially for native proteins. This report describes the development of a microfluidic thermal gel transient isotachophoresis (TG-tITP) method to rapidly separate native proteins with high resolution. Thermal gels were employed as a separations matrix because of their unique ability to change viscosity in response to temperature. Proteins were added into thermal gel and loaded into a microfluidic device. Electrolyte optimization was conducted to achieve robust tITP to isotachophoretically preconcentrate proteins and then electrophoretically separate them. Electropherograms were collected through both time and distance to enable both small and large proteins to be measured within a single analysis. The effects of temperature were evaluated and found to exhibit a pronounced effect on the separation. Temperature gradients were then employed to alter thermal gel viscosity over time to maximize separation resolution between proteins. The results herein demonstrate how gradient TG-tITP achieves rapid, high-performance separations of native proteins. This analysis provided a wide mass range (6-464 kDa) with two-fold higher resolution than native PAGE while requiring 15,000-fold less protein loading and providing five-fold faster analysis times.

Gels in Microscale Electrophoresis

Gel matrices are fundamental to electrophoresis analyses of biopolymers in microscale channels. Both capillary gel and microchannel gel electrophoresis systems have produced fundamental advances in the scientific community. These analytical techniques remain as foundational tools in bioanalytical chemistry and are indispensable in the field of biotherapeutics. This review summarizes the current state of gels in microscale channels and provides a brief description of electrophoretic transport in gels. In addition to the discussion of traditional polymers, several nontraditional gels are introduced. Advances in gel matrices highlighted include selective polymers modified to contain added functionality as well as thermally responsive gels formed through self-assembly. This review discusses cutting-edge applications to challenging areas of discovery in DNA, RNA, protein, and glycan analyses. Finally, emerging techniques that result in multifunctional assays for real-time biochemical processing in capillary and three-dimensional channels are identified.

Recent Advances in Detection for Breast-Cancer-Derived Exosomes

Breast cancer is the most common malignant tumor in women, its incidence is secret, and more than half of the patients are diagnosed in the middle and advanced stages, so it is necessary to develop simple and efficient detection methods for breast cancer diagnosis to improve the survival rate and quality of life of breast cancer patients. Exosomes are extracellular vesicles secreted by all kinds of living cells, and play an important role in the occurrence and development of breast cancer and the formation of the tumor microenvironment. Exosomes, as biomarkers, are an important part of breast cancer fluid biopsy and have become ideal targets for the early diagnosis, curative effect evaluation, and clinical treatment of breast cancer. In this paper, several traditional exosome detection methods, including differential centrifugation and immunoaffinity capture, were summarized, focusing on the latest research progress in breast cancer exosome detection. It was summarized from the aspects of optics, electrochemistry, electrochemiluminescence and other aspects. This review is expected to provide valuable guidance for exosome detection of clinical breast cancer and the establishment of more reliable, efficient, simple and innovative methods for exosome detection of breast cancer in the future.

Multiplexed miRNA Quantitation Using Injectionless Microfluidic Thermal Gel Electrophoresis

MicroRNAs (miRNAs) are a class of biomolecules that have high clinical and pharmaceutical significance because of their ability to regulate protein expression. Better methods are needed to quantify target miRNAs, but their similar sequence lengths and low concentrations in biomedical samples impede analysis. This report aimed to develop a simple, rapid method to directly quantify multiple miRNAs using microfluidic thermal gel electrophoresis (TGE). Fluorescent probes were designed complementarily in sequence to four target miRNAs that also contained variable DNA overhangs to alter their electrophoretic mobilities. Samples and probes were directly added into thermal gel and loaded throughout a microchannel. Applying voltage resulted in an inline preconcentration and separation of the miRNAs that did not require a sample injection nor user intervention to switch between modes. Baseline resolution was achieved between four double-stranded miRNA-probe hybrids and four excess single-stranded probes. Analytical performance was then improved by designing an innovative microfluidic device with a tapered channel geometry. This device exhibited superior detection limits and separation resolution compared to standard channel devices without increasing the complexity of microfabrication or device operation. A proof-of-concept demonstration was then performed, showing that target miRNAs could be detected from cell extracts. These results demonstrate that TGE provides a simple, inexpensive means of conducting multiplexed miRNA measurements, with the potential for automation to facilitate future clinical and pharmaceutical analyses.

Towards a protein-selective Raman enhancement by a glycopolymer-based composite surface

Surface-enhanced Raman scattering (SERS), which is based on the surface plasmon resonance (LSPR) of noble metal nanostructures, is widely used in the biological field due to its advantages of non-damaging samples and detection up to the molecular level. For biological SERS detection, preparation of substrates with biocompatibility and specific adsorption, leading to selective enhancement of the target biomolecules, are important design strategies. Utilizing the specific interaction between a carbohydrate and protein, a glycopolymer-based composite surface is fabricated to realize specific SERS detection of proteins. Herein, we use N-3,4-dihydroxybenzeneethyl methacrylamide (DMA), 2-deoxy-2-(methacrylamido)glucopyranose (MAG) and methacrylic acid (MAA) as monomers in a sunlight-induced RAFT polymerization to synthesize a dopamine-containing glycopolymer. The glycopolymers are used to prepare a SERS substrate. The composite surface shows specific protein adsorption capacity, and the selective Raman enhancement of specific proteins was successfully achieved between the two different proteins Con A and BSA. This provides a feasible approach to design a SERS surface for protein detection and the study of the interaction between sugar and proteins.

Lab-on-a-chip technologies for food safety, processing, and packaging applications: a review

The advent of microfluidic systems has led to significant developments in lab-on-a-chip devices integrating several functions onto a single platform. Over the years, these miniature devices have become a promising tool for faster analytical testing, displaying high precision and efficiency. Nonetheless, most microfluidic systems are not commercially available. Research is actually undergoing on the application of these devices in environmental, food, biomedical, and healthcare industries. The lab-on-a-chip industry is predicted to grow annually by 20%. Here, we review the use of lab-on-a-chip devices in the food sector. We present fabrication technologies and materials to developing lab-on-a-chip devices. We compare electrochemical, optical, colorimetric, chemiluminescence and biological methods for the detection of pathogens and microorganisms. We emphasize emulsion processing, food formulation, nutraceutical development due to their promising characteristics. Last, smart packaging technologies like radio frequency identification and indicators are highlighted because they allow better product identification and traceability.

Harnessing Joule heating in microfluidic thermal gel electrophoresis to create reversible barriers for cell enrichment

Gel electrophoresis is a ubiquitous bioanalytical technique used to characterize the components of cell lysates. However, analyses of bulk lysates sacrifice detection sensitivity because intracellular biomolecules become diluted, and the liberation of proteases and nucleases can degrade target analytes. This report describes a method to enrich cells directly within a microfluidic gel as a first step toward online measurement of trace intracellular biomolecules with minimal dilution and degradation. Thermal gels were employed as the gel matrix because they can be reversibly converted between liquid and solid phases as a function of temperature. Rather than fabricate costly heating elements into devices to control temperature-and thus the phase of the gel-Joule heating was used instead. Adjoining regions of liquid-phase and solid-phase gel were formed within microfluidic channels by selectively inducing localized Joule heat. Cells migrated through the liquid gel but could not enter the solid gel-accumulating at the liquid-solid gel boundary-whereas small molecule contaminants passed through to waste. Barriers were then liquified on-demand by removing Joule heat to collect the purified, non-lysed cells for downstream analyses. Using voltage-controlled Joule heating to regulate the phase of thermal gels is an innovative approach to facilitate in-gel cell enrichment in low-cost microfluidic devices.

Advances in Micro/Nanoporous Membranes for Biomedical Engineering

Porous membrane materials at the micro/nanoscale have exhibited practical and potential value for extensive biological and medical applications associated with filtration and isolation, cell separation and sorting, micro-arrangement, in-vitro tissue reconstruction, high-throughput manipulation and analysis, and real-time sensing. Herein, an overview of technological development of micro/nanoporous membranes (M/N-PMs) is provided. Various membrane types and the progress documented in membrane fabrication techniques, including the electrochemical-etching, laser-based technology, microcontact printing, electron beam lithography, imprinting, capillary force lithography, spin coating, and microfluidic molding are described. Their key features, achievements, and limitations associated with micro/nanoporous membrane (M/N-PM) preparation are discussed. The recently popularized applications of M/N-PMs in biomedical engineering involving the separation of cells and biomolecules, bioparticle operations, biomimicking, micropatterning, bioassay, and biosensing are explored too. Finally, the challenges that need to be overcome for M/N-PM fabrication and future applications are highlighted.