Rapid preconcentration of viable bacteria using magnetic ionic liquids for PCR amplification and culture-based diagnostics

Recent Advances in Microfluidics-Based Monitoring of Waterborne Pathogens: From Isolation to Detection

Waterborne pathogens seriously threaten human life and can cause diarrhea, gastrointestinal disorders, and more serious systemic infections. These pathogens are usually caused by contaminated water sources that contain disease-causing microorganisms, such as bacteria, viruses, and parasites, which cause infection and disease when they enter the human body through drinking water or other means. Due to the wide range of transmission routes and the high potential risk of waterborne pathogens, there is an urgent need for an ultrasensitive, rapid, and specific pathogenic microorganism monitoring platform to meet the critical monitoring needs of some water bodies' collection points daily monitoring needs. Microfluidics-based pathogen surveillance methods are an important stage towards automated detection through real-time and multi-targeted monitoring, thus enabling a comprehensive assessment of the risk of exposure to waterborne pathogens and even emerging microbial contaminants, and thus better protection of public health. Therefore, this paper reviews the latest research results on the isolation and detection of waterborne pathogens based on microfluidic methods. First, we introduce the traditional methods for isolation and detection of pathogens. Then, we compare some existing microfluidic pathogen isolation and detection methods and finally look forward to some future research directions and applications of microfluidic technology in waterborne pathogens monitoring.

Evaluating the capacity of magnetic ionic liquids for separation and concentration of non-enveloped viral particles and free viral genomic RNA

Magnetic ionic liquids (MILs) have proven effective as capture reagents for foodborne bacterial pathogens; however, there are currently no published studies regarding their use with foodborne, non-enveloped viruses. In this study, a protocol was evaluated for capture and recovery of bacteriophage MS2, a human norovirus surrogate, and purified viral genomic single stranded RNA (ssRNA) from an aqueous suspension using MILs. Transition metal-based MILs showed similar capture and recovery efficiency for both targets. A rare earth metal-based MIL showed much greater capture efficiency than the transition metal-based MILs, but displayed similar recovery. All tested MILs showed slightly higher capture and recovery efficiency for free RNA in comparison to intact virus, though overall trends were similar, and most MILs could recover both targets at as little as 102 PFU/mL intact MS2 or copies/mL purified RNA. A plaque assay confirmed that contact with MILs did not significantly reduce viral infectivity. Adjusting MIL volume gave no significant changes in capture or recovery, likely due to interplay between volume for the hydrophobic MIL and dispersion. Reducing the elution volume gave a slight increase in recovery, indicating MILs could be used for target enrichment after further optimization. MILs could also capture MS2 from romaine lettuce rinsate at comparable or even higher levels than from pure suspension, though loss in recovery was observed when the rinsate was prepared in an alkaline elution buffer. Overall, these results demonstrate the potential utility of MILs as concentration reagents for foodborne viruses, particularly for in-field applications.

A nano-biosensing platform based on CuS-BSA for label-free fluorescence detection of Escherichia coli

Bacterial contamination is a serious issue for public health and food safety. In this work, a simple and label-free fluorescence detection nanoplatform for Escherichia coli (E. coli) was established on the basis of the competitive relationship for the reduction of Cu2+ in CuS-BSA between E. coli and O-phenylenediamine (OPD). OPD could be directly oxidized by Cu2+ to produce 2,3-diaminophenazine (ox OPD) with fluorescence properties. When OPD was introduced into an aqueous solution containing CuS-BSA and E. coli, the oxidation of OPD was inhibited owing to the reduction of Cu2+ to Cu+/Cu0 by NADH-2 dehydrogenase in the bacterial copper homeostasis mechanism, thus decreasing the fluorescence response signal of the system. Meanwhile, our strategy exhibited a satisfactory performance with a broad linear response to E. coli ranging from 12 to 1.2 × 107 CFU mL-1, and the limit of detection was 9 CFU mL-1. The practicability of the developed fluorescence biosensing platform in real samples was evaluated by successful determination of E. coli in drinking water and orange juice. These findings provide a new sensing strategy for analyzing other foodborne bacteria and ensuring food safety assessment.

Surface-Enhanced Raman Spectroscopy Sensor Integrated with Ag@ZIF-8@Au Core-Shell-Shell Nanowire Membrane for Enrichment, Ultrasensitive Detection, and Inactivation of Bacteria in the Environment

A core-shell-shell sandwich material is developed with silver nanowires as the core, ZIF-8 as an inner shell, and gold nanoparticles as the outer shell, namely, Ag@ZIF-8@Au nanowires (AZA-NW). Then, the synthesized AZA-NW is transformed into a surface-enhanced Raman spectroscopy (SERS) sensor (named M-AZA) by the vacuum filtration method and used to enrich, detect, and inactivate traces of bacteria in the environment. The M-AZA sensor has three main functions: (1) trace bacteria are effectively enriched, with an enrichment efficiency of 91.4%; (2) ultrasensitive detection of trace bacteria is realized, with a minimum detectable concentration of 1 × 101 CFU/mL; (3) bacteria are effectively killed up to 92.4%. The shell thickness of ZIF-8 (5-75 nm) is controlled by adjusting the synthesis conditions. At an optimum shell thickness of 15 nm, the effect of gold nanoparticles and ZIF-8 shell on the sensor's stability, SERS activity, and antibacterial performance is investigated. The simulation of the SERS sensor using the finite difference time domain (FDTD) method is consistent with the experimental results, theoretically demonstrating the role of the gold nanoparticles and the ZIF-8 shell. The sensor also shows excellent stability, safety, and generalizability. The campus water sample is then tested on-site by the M-AZA SERS sensor, indicating its potential for practical applications.

Dilute-and-shoot approach combined with in-situ formed metal-containing ionic liquids for extraction of benzophenone and related compounds from açaí-based food products

For the first time, benzophenone and related compounds were investigated in açaí-based food products. An extraction method based on the dilute-and-shoot approach, combined with the use of in-situ formed metal-containing ionic liquids (MCILs) followed by high-performance liquid chromatography, was developed and validated. A nickel and cobalt-based MCIL, in addition to the ratio of MCIL to lithium bis[(trifluoromethyl)sulfonyl]imide salt ([Li+][NTf2-]) for the ensuing metathesis reaction, were optimized. Parameters of the in-situ formed MCIL step, namely, the amount of MCIL, centrifugation time, and dilution step, were analyzed using a multivariate optimization approach, including central composite rotatable design and Derringer and Suich's tool. Optimum extraction performance was achieved using 50.98 mg of nickel-based MCIL and a MCIL to ([Li+][NTf2-]) ratio of 1:3 (m/m), a centrifuge time of 22 min, and 10.53 mL of water for the dilution step. This condition was used to perform analytical validation, which yielded satisfactory results with R2 ≥ 0.995, limits of detection (LOD) ranging from 0.0025 to 0.5 mg kg-1, and limits of quantification (LOQ) between 0.008 and 1.5 mg kg-1. The recovery rate ranged from 87 % to 107 % and precision values (as percent relative standard deviation) were equal or lower than 13 %. The validated method was applied to 25 samples of açaí-based food products purchased from Brazil and the United States. None of the samples showed analyte concentration levels above the LOD. The method's suitability was demonstrated for future monitoring of complex samples, such as foodstuffs.

Progress in methods for the detection of viable Escherichia coli

Escherichia coli (E. coli) is a prevalent enteric bacterium and a necessary organism to monitor for food safety and environmental purposes. Developing efficient and specific methods is critical for detecting and monitoring viable E. coli due to its high prevalence. Conventional culture methods are often laborious and time-consuming, and they offer limited capability in detecting potentially harmful viable but non-culturable E. coli in the tested sample, which highlights the need for improved approaches. Hence, there is a growing demand for accurate and sensitive methods to determine the presence of viable E. coli. This paper scrutinizes various methods for detecting viable E. coli, including culture-based methods, molecular methods that target DNAs and RNAs, bacteriophage-based methods, biosensors, and other emerging technologies. The review serves as a guide for researchers seeking additional methodological options and aiding in the development of rapid and precise assays. Moving forward, it is anticipated that methods for detecting E. coli will become more stable and robust, ultimately contributing significantly to the improvement of food safety and public health.

Rapid detection of live bacteria in water using nylon filter membrane-integrated centrifugal microfluidics

Water is one of the most indispensable elements for human beings. People can live without food for a couple of weeks but cannot live without water for a couple of days. Unfortunately, drinking water is not always safe around the world; in many areas, the water for drinking could be contaminated with various microbes. However, the total viable microbe count in water still relies on culture-based methods in laboratories. Therefore, in this work, we report a novel, simple, and highly efficient strategy to detect live bacteria in water via a nylon membrane-integrated centrifugal microfluidic device. A handheld fan and a rechargeable hand warmer were utilized as the centrifugal rotor and the heat resource for reactions, respectively. The bacteria in water can be rapidly concentrated >500-fold by our centrifugation system. After incubation with water-soluble tetrazolium-8 (WST-8), the color change of the nylon membranes can be visually interpreted directly by the naked eye or recorded with a smartphone camera. The whole process can be finished in 3 h, and the detection limit can reach 10² CFU/mL. The detection range ranges from 10² CFU/mL to 10⁵ CFU/mL. The cell counting results of our platform are highly positively correlated with the results of cell counting by the conventional lysogeny broth (LB) agar plate approach or the commercial 3 M Petrifilm™ cell counting plate. Our platform provides a convenient and sensitive strategy for rapid monitoring. We highly anticipate that this platform can improve water quality monitoring in resource-poor countries in the near future.

Applications of magnetic and electromagnetic forces in micro-analytical systems

Novel applications of magnetic fields in analytical chemistry have become a remarkable trend in the last two decades. Various magnetic forces have been employed for the migration, orientation, manipulation, and trapping of microparticles, and new analytical platforms for separating and detecting molecules have been proposed. Magnetic materials such as functional magnetic nanoparticles, magnetic nanocomposites, and specially designed magnetic solids and liquids have also been developed for analytical purposes. Numerous attractive applications of magnetic and electromagnetic forces on magnetic and non-magnetic materials have been studied, but fundamental studies to understand the working principles of magnetic forces have been challenging. These studies will form a new field of magneto-analytical science, which should be developed as an interdisciplinary field. In this review, essential pioneering works and recent attractive developments are presented.

Silent Raman imaging of highly effective anti-bacterial activity synchronous with biofilm breakage using poly(4-cyanostyrene)@silver@polylysine nanocomposites

Biofilms are known to be a great challenge for their anti-bacterial activity as they obstruct drug action for deeper and more thorough bacteria-killing effects. Therefore, developing highly effective antibacterial agents to destroy biofilms and eradicate bacteria is of great significance. Herein, a new type of nanocomposites (denoted as poly(4-cyanostyrene)@silver@polylysine) is proposed, in which polylysine (PLL) could rapidly capture the biofilms and exhibit excellent antibacterial efficacy together with decorated silver (Ag) nanoparticles (NPs) through the charge effect and Ag⁺ release. Notably, nearly 100% antibacterial rates against Gram-positive bacterium (Staphylococcus aureus, S. aureus) and Gram-negative bacterium (Escherichia coli, E. coli) were achieved. More importantly, poly(4-cyanostyrene) with biological silent Raman imaging capacity is able to illustrate the relationship between antibacterial efficiency and biofilm breakage. In short, such novel nanocomposites can improve the bioavailability of each component and display tremendous potential in antibacterial applications.

Emerging Bioanalytical Devices and Platforms for Rapid Detection of Pathogens in Environmental Samples

The development of robust bioanalytical devices and biosensors for infectious pathogens is progressing well with the advent of new materials, concepts, and technology. The progress is also stepping towards developing high throughput screening technologies that can quickly identify, differentiate, and determine the concentration of harmful pathogens, facilitating the decision-making process for their elimination and therapeutic interventions in large-scale operations. Recently, much effort has been focused on upgrading these analytical devices to an intelligent technological platform by integrating them with modern communication systems, such as the internet of things (IoT) and machine learning (ML), to expand their application horizon. This review outlines the recent development and applications of bioanalytical devices and biosensors to detect pathogenic microbes in environmental samples. First, the nature of the recent outbreaks of pathogenic microbes such as foodborne, waterborne, and airborne pathogens and microbial toxins are discussed to understand the severity of the problems. Next, the discussion focuses on the detection systems chronologically, starting with the conventional methods, advanced techniques, and emerging technologies, such as biosensors and other portable devices and detection platforms for pathogens. Finally, the progress on multiplex assays, wearable devices, and integration of smartphone technologies to facilitate pathogen detection systems for wider applications are highlighted.

Advances in bacterial concentration methods and their integration in portable detection platforms: A review

Early detection and identification of microbial contaminants is crucial in many sectors, including clinical diagnostics, food quality control and environmental monitoring. Biosensors have recently gained attention among other bacterial detection technologies due to their simplicity, rapid response, selectivity, and integration/miniaturization potential in portable microfluidic platforms. However, biosensors are limited to the analysis of small sample volumes, and pre-concentration steps are necessary to reach the low sensitivity levels of few bacteria per mL required in the analysis of real clinical, industrial or environmental samples. Many platforms already exist where bacterial detection and separation/accumulation systems are integrated in a single platform, but they have not been compiled and critically analysed. This review reports on most recent advances in bacterial concentration/detection platforms with emphasis on the concentration strategy. Systems based on five concentration strategies, i.e. centrifugation, filtration, magnetic separation, electric separation or acoustophoresis, are here presented and compared in terms of processed sample volume, concentration efficiency, concentration time, ability to work with different types of samples, and integration potential, among others. The critical evaluation presented in the review is envision to facilitate the development of future platforms for fast, sensitive and in situ bacterial detection in real sample.

An overview of magnetic ionic liquids: From synthetic strategies to applications in microextraction techniques

Remarkable progress has been achieved in the application of magnetic ionic liquids in microextraction-based procedures. These materials exhibit unique physicochemical properties of ionic liquids featuring additional responses to magnetic fields by incorporating a paramagnetic component within the chemical structure. This intriguing property can open new horizons in analytical extractions because the solvent manipulation is facilitated. Moreover, the tunable chemical structures of magnetic ionic liquids also allow for task-specific extractions that can significantly increase the method selectivity. This review aimed at providing an up-to-date overview of articles involving synthesis, physicochemical properties, and applications of magnetic ionic liquids highlighting recent developments and configurations. Moreover, a section containing critical evaluation and future trends in magnetic ionic liquid-based extractions is included.

A gadolinium-based magnetic ionic liquid for dispersive liquid-liquid microextraction

A hydrophobic gadolinium-based magnetic ionic liquid (MIL) was investigated for the first time as an extraction solvent in dispersive liquid–liquid microextraction (DLLME). The tested MIL was composed of trihexyl(tetradecyl)phosphonium cations and paramagnetic gadolinium chloride anions. The prepared MIL showed low water miscibility, reasonable viscosity, markedly high magnetic susceptibility, adequate chemical stability, low UV background, and compatibility with reversed-phase HPLC solvents. These features resulted in a more efficient extraction than the corresponding iron or manganese analogues. Accordingly, the overall method sensitivity and reproducibility were improved, and the analysis time was reduced. The applicability of the proposed MIL was examined through the microextraction of four sartan antihypertensive drugs from aqueous samples followed by reversed-phase HPLC with UV detection at 240 nm. The DLLME procedures were optimized for disperser solvent type, MIL mass, disperser solvent volume, as well as acid, base, and salt addition. The limits of quantitation (LOQs) obtained with the analysis of 1.2-mL samples after DLLME and HPLC were 80, 30, 40, and 160 ng/mL for azilsartan medoxomil, irbesartan, telmisartan, and valsartan, respectively. Correlation coefficients were greater than 0.9988 and RSD values were in the range of 2.48–4.07%. Under the optimized microextraction conditions and using a 5-mL sample volume, enrichment factors were raised from about 40 for all sartans using a 1.2-mL sample to 175, 176, 169, and 103 for azilsartan medoxomil, irbesartan, valsartan, and telmisartan, respectively. The relative extraction recoveries for the studied sartans in river water varied from 82.5 to 101.48% at a spiked concentration of 0.5 μg/mL for telmisartan and irbesartan and 1 μg/mL for azilsartan medoxomil and valsartan.

Rapid Detection of Legionella pneumophila in Drinking Water, Based on Filter Immunoassay and Chronoamperometric Measurement

Legionella is a pathogenic bacterium, ubiquitous in freshwater environments and able to colonise man-made water systems from which it can be transmitted to humans during outbreaks. The prevention of such outbreaks requires a fast, low cost, automated and often portable detection system. In this work, we present a combination of sample concentration, immunoassay detection, and measurement by chronoamperometry. A nitrocellulose microfiltration membrane is used as support for both the water sample concentration and the Legionella immunodetection. The horseradish peroxidase enzymatic label of the antibodies permits using the redox substrate 3,3′,5,5′-Tetramethylbenzidine to generate current changes proportional to the bacterial concentration present in drinking water. Carbon screen-printed electrodes are employed in the chronoamperometric measurements. Our system reduces the detection time: from the 10 days required by the conventional culture-based methods, to 2–3 h, which could be crucial to avoid outbreaks. Additionally, the system shows a linear response (R² value of 0.99), being able to detect a range of Legionella concentrations between 10¹ and 10⁴ cfu·mL⁻¹ with a detection limit (LoD) of 4 cfu·mL⁻¹.

Magnetic ionic liquids: interactions with bacterial cells, behavior in aqueous suspension, and broader applications

Previously, we demonstrated capture and concentration of Salmonella enterica subspecies enterica ser. Typhimurium using magnetic ionic liquids (MILs), followed by rapid isothermal detection of captured cells via recombinase polymerase amplification (RPA). Here, we report work intended to explore the broader potential of MILs as novel pre-analytical capture reagents in food safety and related applications. Specifically, we evaluated the capacity of the ([P₆₆₆₁₄⁺][Ni(hfacac)₃^-]) ("Ni(II)") MIL to bind a wider range of human pathogens using a panel of Salmonella and Escherichia coli O157:H7 isolates, including a "deep rough" strain of S. Minnesota. We extended this exploration further to include other members of the family Enterobacteriaceae of food safety and clinical or agricultural significance. Both the Ni(II) MIL and the ([P₆₆₆₁₄⁺][Dy(hfacac)₄^-]) ("Dy(III)") MIL were evaluated for their effects on cell viability and structure-function relationships behind observed antimicrobial activities of the Dy(III) MIL were determined. Next, we used flow imaging microscopy (FIM) of Ni(II) MIL dispersions made in model liquid media to examine the impact of increasing ionic complexity on MIL droplet properties as a first step towards understanding the impact of suspension medium properties on MIL dispersion behavior. Finally, we used FIM to examine interactions between the Ni(II) MIL and Serratia marcescens, providing insights into how the MIL may act to capture and concentrate Gram-negative bacteria in aqueous samples, including food suspensions. Together, our results provide further characterization of bacteria-MIL interactions and support the broader utility of the Ni(II) MIL as a cell-friendly capture reagent for sample preparation prior to cultural or molecular analyses. Graphical abstract.

Impacts of Clarification Techniques on Sample Constituents and Pathogen Retention

Determination of the microbial content in foods is important, not only for safe consumption, but also for food quality, value, and yield. A variety of molecular techniques are currently available for both identification and quantification of microbial content within samples; however, their success is often contingent upon proper sample preparation when the subject of investigation is a complex mixture of components such as foods. Because of the importance of sample preparation, the present study employs a systematic approach to compare the effects of four different separation techniques (glass wool, 50 μm polypropylene filters, graphite felt, and continuous flow centrifugation (CFC)) on sample preparation. To define the physical effects associated with the use of these separation methods, a multifactorial analysis was performed where particle size and composition, both pre- and post- processing, were analyzed for four different food matrices including lean ground beef, ground pork, ground turkey and spinach. Retention of three important foodborne bacterial pathogens (Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes) was also examined to evaluate the feasibility of the aforementioned methods to be utilized within the context of foodborne pathogen detection. Data from the multifactorial analysis not only delineated the particle size ranges but also defined the unique compositional profiles and quantified the bacterial retention. The three filtration membranes allowed for the passage of bacteria with minimal loss while CFC concentrated the inoculated bacteria. In addition, the deposition and therefore concentration of food matrix observed with CFC was considerably higher for meat samples relative to spinach. However, filtration with glass wool prior to CFC helped clarify meat samples, which led to considerably lower amounts of solids in the CFC vessel post processing and an increase in the recovery of the bacteria. Overall, by laying a framework for the deductive selection of sample preparation techniques, the results of the study can be applied to a range of applications where it would be beneficial to scientifically guide the pairing of the criteria associated with a downstream detection method with the most advantageous sample preparation techniques for complex matrices such as foods.

From Paramagnetic to Superparamagnetic Ionic Liquid/Poly(ionic liquid): The Effect of π-π Stacking Interaction

Magnetic ionic liquids (MILs) and poly(magnetic ionic liquids) (PMILs) with FeCl₄^- as anions usually show weak magnetism, such as paramagnetism or antiferromagnetism, at room temperature. Inspired by the natural inorganic ferromagnet with ordered crystal structures, a soft superparamagnetic ionic liquid (TMBBDI[FeCl₄]) and corresponding poly(ionic liquid) (PTMBBDI[FeCl₄]) were prepared by introducing π-π stacking biphenyl groups into the organic cations. Both of the compounds exhibited superparamagnetism from 100 to 300 K, while a ferromagnetic hysteresis loop was found at 300 K. Ferromagnetic interactions were observed from zero field cooling and field cooling studies for both TMBBDI[FeCl₄] and PTMBBDI[FeCl₄]. However, the MIL and PMIL without π-π stacking interaction were paramagnetic without ferromagnetic interaction. The superparamagnetism of the TMBBDI[FeCl₄] and PTMBBDI[FeCl₄] was ascribed to the π-π stacking interactions between biphenyl groups, which not only shortened the Fe-Fe distance to the ferromagnetic interaction range but also increased the order degree of the molecules.

Point-of-Care Strategies for Detection of Waterborne Pathogens

Waterborne diseases that originated due to pathogen microorganisms are emerging as a serious global health concern. Therefore, rapid, accurate, and specific detection of these microorganisms (i.e., bacteria, viruses, protozoa, and parasitic pathogens) in water resources has become a requirement of water quality assessment. Significant research has been conducted to develop rapid, efficient, scalable, and affordable sensing techniques to detect biological contaminants. State-of-the-art technology-assisted smart sensors have improved features (high sensitivity and very low detection limit) and can perform in a real-time manner. However, there is still a need to promote this area of research, keeping global aspects and demand in mind. Keeping this view, this article was designed carefully and critically to explore sensing technologies developed for the detection of biological contaminants. Advancements using paper-based assays, microfluidic platforms, and lateral flow devices are discussed in this report. The emerging recent trends, mainly point-of-care (POC) technologies, of water safety analysis are also discussed here, along with challenges and future prospective applications of these smart sensing technologies for water health diagnostics.

Development of an innovative and sustainable one-step method for rapid plant DNA isolation for targeted PCR using magnetic ionic liquids

BACKGROUND

Nowadays, there is an increasing demand for fast and reliable plant biomolecular analyses. Conventional methods for the isolation of nucleic acids are time-consuming and require multiple and often non-automatable steps to remove cellular interferences, with consequence that sample preparation is the major bottleneck in the bioanalytical workflow. New opportunities have been created by the use of magnetic ionic liquids (MILs) thanks to their affinity for nucleic acids.

RESULTS

In the present study, a MIL-based magnet-assisted dispersive liquid-liquid microextraction (maDLLME) method was optimized for the extraction of genomic DNA from Arabidopsis thaliana (L.) Heynh leaves. MILs containing different metal centers were tested and the extraction method was optimized in terms of MIL volume and extraction time for purified DNA and crude lysates. The proposed approach yielded good extraction efficiency and is compatible with both quantitative analysis through fluorimetric-based detection and qualitative analysis as PCR amplification of multi and single locus genes. The protocol was successfully applied to a set of plant species and tissues.

CONCLUSIONS

The developed MIL-based maDLLME approach exhibits good enrichment of nucleic acids for extraction of template suitable for targeted PCR; it is very fast, sustainable and potentially automatable thereby representing a powerful tool for screening plants rapidly using DNA-based methods.

Coupling oligonucleotides possessing a poly-cytosine tag with magnetic ionic liquids for sequence-specific DNA analysis

Oligonucleotide probes were designed with a poly-cytosine region that facilitates stable anchoring to a magnetic ionic liquid support. By tethering a recognition sequence to the poly-C tag, the resulting diblock oligonucleotides distinguished single-nucleotide variants and captured DNA targets from interfering genomic DNA and cell lysate for qPCR amplification.

Preconcentration of DNA using magnetic ionic liquids that are compatible with real-time PCR for rapid nucleic acid quantification

Nucleic acid extraction and purification represents a major bottleneck in DNA analysis. Traditional methods for DNA purification often require reagents that may inhibit quantitative polymerase chain reaction (qPCR) if not sufficiently removed from the sample. Approaches that employ magnetic beads may exhibit lower extraction efficiencies due to sedimentation and aggregation. In this study, four hydrophobic magnetic ionic liquids (MILs) were investigated as DNA extraction solvents with the goal of improving DNA enrichment factors and compatibility with downstream bioanalytical techniques. By designing custom qPCR buffers, we directly incorporated DNA-enriched MILs including trihexyl(tetradecyl)phosphonium tris(hexafluoroacetylaceto)nickelate(II) ([P_6,6,6,14⁺][Ni(hfacac)₃^-]), [P_6,6,6,14⁺] tris(hexafluoroacetylaceto)colbaltate(II) ([Co(hfacac)₃^-]), [P_6,6,6,14⁺] tris(hexafluoroacetylaceto)manganate(II) ([Mn(hfacac)₃^-]), or [P_6,6,6,14⁺] tetrakis(hexafluoroacetylaceto)dysprosate(III) ([Dy(hfacac)₄^-]) into reaction systems, thereby circumventing the need for time-consuming DNA recovery steps. Incorporating MILs into the reaction buffer did not significantly impact the amplification efficiency of the reaction (91.1%). High enrichment factors were achieved using the [P_6,6,6,14⁺][Ni(hfacac)₃^-] MIL for the extraction of single-stranded and double-stranded DNA with extraction times as short as 2 min. When compared to a commercial magnetic bead-based platform, the [P_6,6,6,14⁺][Ni(hfacac)₃^-] MIL was capable of producing higher enrichment factors for single-stranded DNA and similar enrichment factors for double-stranded DNA. The MIL-based method was applied for the extraction and direct qPCR amplification of mutation prone-KRAS oncogene fragment in plasma samples. Graphical abstract Magnetic ionic liquid solvents are shown to preconcentrate sufficient KRAS DNA template from an aqueous solution in as short as 2 min without using chaotropic salts or toxic organic solvents. By using custom-designed qPCR buffers, DNA can be directly amplified and quantified from four MILs examined in this study.

Biological and nanotechnological applications using interactions between ionic liquids and nucleic acids

Nucleic acids have emerged as powerful biological and nanotechnological tools. In biological and nanotechnological experiments, methods of extracting and purifying nucleic acids from various types of cells and their storage are critical for obtaining reproducible experimental results. In nanotechnological experiments, methods for regulating the conformational polymorphism of nucleic acids and increasing sequence selectivity for base pairing of nucleic acids are important for developing nucleic acid-based nanomaterials. However, dearth of media that foster favourable behaviour of nucleic acids has been a bottleneck for promoting the biology and nanotechnology using the nucleic acids. Ionic liquids (ILs) are solvents that may be potentially used for controlling the properties of the nucleic acids. Here, we review researches regarding the behaviour of nucleic acids in ILs. The efficiency of extraction and purification of nucleic acids from biological samples is increased by IL addition. Moreover, nucleic acids in ILs show long-term stability, which maintains their structures and enhances nuclease resistance. Nucleic acids in ILs can be used directly in polymerase chain reaction and gene expression analysis with high efficiency. Moreover, the stabilities of the nucleic acids for duplex, triplex, and quadruplex (G-quadruplex and i-motif) structures change drastically with IL cation-nucleic acid interactions. Highly sensitive DNA sensors have been developed based on the unique changes in the stability of nucleic acids in ILs. The behaviours of nucleic acids in ILs detailed here should be useful in the design of nucleic acids to use as biological and nanotechnological tools.

Expanding the Structural Motif Landscape of Heterometallic β-Diketonates: Congruently Melting Ionic Solids

The first example of ionic β-diketonates in which both the cation and anion are octahedral coordinatively saturated metal diketonate moieties are reported. Heterometallic tin-transition-metal heteroleptic diketonates were obtained through solid-state redox reactions and are formulated as {[Sn^IV(thd)₃]⁺[M^II(hfac)₃]^-} (M^II = Mn (1), Fe (2), Co (3); thd = 2,2,6,6-tetramethyl-3,5-heptanedionate, hfac = hexafluoroacetylacetonate). X-ray single-crystal structural investigations along with DART mass spectrometry, multinuclear NMR, and magnetic susceptibility measurements have been used to confirm an assignment of metal oxidation states in compounds 1-3. Ionic compounds were found to melt congruently at temperatures below the decomposition point. As such, they represent prospective materials that can be utilized as ionic liquids as well as reagents for the soft transfer of diketonate ligands. An unexpected volatility of ionic compounds 1-3 was proposed to occur through a transport reaction, in which the transport agent is one of the products of their partial decomposition in the gas or condensed phase.