Extraction of DNA with magnetic ionic liquids using in situ dispersive liquid-liquid microextraction

Investigating a new approach for magnetic ionic liquids: Dispersive liquid-liquid microextraction coupled to pyrolysis gas-chromatography-mass spectrometry to determine flame retardants in sewage sludge samples

This study addresses the analysis of emerging contaminants, often using chromatographic techniques coupled to mass spectrometry. However, sample preparation is often required prior to instrumental analysis, and dispersive liquid-liquid microextraction (DLLME) is a viable strategy in this context. DLLME stands out for its ability to reduce sample and solvent volumes. Notably, dispersive liquid-liquid microextraction using magnetic ionic liquids (MILs) has gained relevance due to the incorporation of paramagnetic components in the chemical structure, thereby eliminating the centrifugation step. A pyrolizer was selected in this work to introduce sample onto the GC column, since the MIL is extremely viscous and incompatible with direct introduction through an autosampler. This study is the first to report the use of a DLLME/MIL technique for sample introduction through a pyrolizer in gas chromatography coupled to mass spectrometry (GC-MS). This approach enables the MIL to be compatible with gas chromatography systems, resulting in optimized analytical and instrument performance. The analysis of polybrominated diphenyl ether flame retardants (PBDEs) was focused on the PBDE congeners 28, 47, 99, 100, and 153 in sewage sludge samples. The [P6,6,6,14+]2[MnCl42-] MIL was thoroughly characterized using UV-Vis, Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy, as well as thermal analysis. In the chromatographic method, a pyrolyzer was used in the sample introduction step (Py-GC-MS), and critical injection settings were optimized using multivariate approaches. Optimized conditions were achieved with a temperature of 220 °C, a pyrolysis time of 0.60 min, and an injection volume of 9.00 μL. DLLME optimization was performed through central compound planning (CCD), and optimized training conditions were achieved with 10.0 mg of MIL, 3.00 μL of acetonitrile (ACN) as dispersive solvent, extraction time of 60 s, and volume of a sample of 8.50 mL. Precision was observed to range from 0.11 % to 12.5 %, with limits of detection (LOD) of 44.4 μg L-1 for PBDE 28, 16.9 μg L-1 for PBDE 47 and PBDE 99, 33.0 μg L-1 for PBDE 100 and 375 μg L-1 for PBDE 153. PBDE 28 was identified and analyzed in the sludge sample at a concentration of 800 μg L-1. The use of MIL in dispersive liquid-liquid microextraction combined with pyrolysis gas chromatography-mass spectrometry enables identification and quantification of PBDEs in sewage sludge samples at concentrations down to the µg L-1 level.

Critical assessment of interactions between ct-DNA and choline-based magnetic ionic liquids: evidences of compaction

Ionic liquids (ILs) have become an alternative green solvent for storage and for stability of DNA. However, an in-depth understanding of binding and molecular interactions between ILs and DNA is needed. In this respect, magnetic ILs (MILs) are promising due to their tunable physicochemical properties. Various spectroscopic techniques and molecular simulations have been employed to unravel the critical factors of the strength and binding mechanism of MILs with DNA. UV-vis spectra unravel the multimodal binding of MILs with DNA, and the intrusion of IL molecules into the minor groove of DNA has been observed from dye displacement studies. Fluorescence correlation spectroscopic studies and scanning electron microscopy confirm the compaction of the DNA. ITC and molecular docking studies estimate the binding affinity of DNA with MILs, of ∼7 kcal mol-1. The 1 μs long-MD simulations give insight into the structural changes in the DNA in the MIL environment. Due to strong interaction with choline ions in the close vicinity, DNA helixes bend or squeeze in length and dilate in diameter (elliptical → spherical), leading to compaction. The post-MD parameters suggest a stronger interaction with [Ch]2[Mn] IL than with [Ch][Fe] IL; hence, the former induces DNA compaction to a more significant extent. Furthermore, decompaction is observed with the addition of sodium salts and is characterized using spectroscopic methods.

Ultra-Low Viscosity and High Magnetic Susceptibility Magnetic Ionic Liquids Featuring Functionalized Diglycolic Acid Ester Rare-Earth and Transition Metal Chelates

Magnetic ionic liquids (MILs) comprise a subcategory of ionic liquids (ILs) and contain a paramagnetic metal center allowing them to be readily manipulated by an external magnetic field. While MILs are popularly employed as solvents in catalysis, separations, and organic synthesis, most low viscosity combinations possess a hydrophilic character that limits their use in aqueous matrices. To date, no study has reported the synthesis and characterization of hydrophobic MILs with viscosities similar to those of hydrophilic MILs and organic solvents while simultaneously exhibiting enhanced magnetic and thermal properties. In this study, diglycolic acid esters are employed as ligands to chelate with paramagnetic metals to produce cations that are paired with metal chelates composed of hexafluoroacetylacetonate ligands to form MILs incorporating multiple metal centers in the cation and anion. Viscosity values below 31.6 cP were obtained for these solvents, the lowest ever reported for hydrophobic MILs. Solubilities in nonpolar solvents such as benzene were observed to be as high as 50% (w/v) MIL-to-solvent ratio while being insoluble in water at concentrations as low as 0.01% (w/v). Effective paramagnetic moment values for these solvents ranged from 5.33 to 15.56 Bohr magnetons (μB), with mixed metal MILs containing multiple lanthanides in the anion generally offering higher magnetic susceptibilities. MILs composed of ligands containing octyl substituents were found to possess thermal stabilities up to 190 °C. The synthetic strategies explored in this study exploit the highly tunable nature of the employed cation and anion pairs to design versatile ultra-low viscosity magnetoactive solvents that possess tremendous potential and applicability in liquid-liquid separation systems, catalysis, and microfluidics where the mechanical movement of the solvent can be easily facilitated using electromagnets.

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.

Multi-magnetic center ionic liquids for dispersive liquid-liquid microextraction coupled with in-situ decomposition based back-extraction for the enrichment of parabens in beverage samples

In this paper, several new multi-magnetic center magnetic ionic liquids (MMILs) were prepared with paramagnetic component simultaneously contained in both the cation and anion and used as extractants to establish a dispersive liquid-liquid microextraction (DLLME) approach followed by in-situ MMIL decomposition based back-extraction for the enrichment and determination of four parabens in beverages. The appropriate MMIL was selected by investigating the extraction performances of the obtained MMILs combined with high performance liquid chromatography-ultraviolet detection (HPLC-UV), and some other experimental factors were explored. Under the optimized DLLME conditions, the four parabens exhibited coefficients of determination (R²) above 0.9987 in the linear range of 0.1-500 ng·mL^-1 for ethylparaben, propylparaben and butylparaben and 0.2-500 ng·mL^-1 for methylparaben. The limits of detection (LODs) and limits of quantification (LOQs) were respectively within 0.03-0.06 ng·mL^-1 and 0.1-0.2 ng·mL^-1, and the relative standard deviations (RSDs) for intra-day and inter-day precision were below 10.8%. Moreover, the application of the developed MMIL-based DLLME method in beverage samples exhibited recoveries within 81.3%-112.1% with RSDs of 0.3%-13.1% at three different spiked levels.

A new magnetic ionic liquid based salting-out assisted dispersive liquid-liquid microextraction for the determination of parabens in environmental water samples

In this study, a new magnetic ionic liquid (MIL) was designed and prepared, containing a magnetic cation from the ligand N,N-dimethyl biguanide (DMBG) complexing with magnetic center Co²⁺ and a bis-trifluoromethanesulfonimide (NTf₂^-) anion. Using the MIL as the extraction solvent, a salting-out assisted dispersive liquid-liquid microextraction (SA-DLLME) combined with high performance liquid chromatography-ultraviolet detection (HPLC-UV) was established for the enrichment and detection of four parabens in environmental water samples. The one-factor-at-a-time experiment was employed to optimize the conditions affecting the extraction efficiency. Under the optimized extraction conditions, the limits of quantification (LOQs) of the four target analytes ranged from 2.0 ng mL^-1 to 2.8 ng mL^-1, and the coefficients of determination (R²) were above 0.9996 in the linear range of 2.8-400 ng mL^-1. On the other hand, the method displayed good repeatability and accuracy with intra-day and inter-day relative standard deviations (RSDs) of 2.1-13.0% and recoveries of 82.0-114.6%. The established method was applied to real samples with recoveries within 81.6-125.4%, and the results demonstrated that the method was practical.

Magnetic Nylon 6 Nanocomposites for the Microextraction of Nucleic Acids from Biological Samples

Magnetic Fe3O4 nanoparticles (MNPs) have great potential for nucleic acid separation, detection, and delivery. MNPs are considered a valuable tool in biomedicine due to their cost-effectiveness, stability, easy surface functionalization, and the possibility of the manipulations under a magnetic field. Herein, the synthesis of magnetic nylon 6 nanocomposites (MNPs@Ny6) was investigated. Transmission electron microscopy (TEM) was used for morphology and size analysis. A new method of UV-induced immobilization of oligonucleotides on MNPs@Ny6 for nucleic acid magnetic separation was proposed. MNPs@Ny6 shows a high oligonucleotide binding capacity of 2.2 nmol/mg with 73.3% loading efficiency. The proposed system has been applied to analyze model mixtures of target RNA on the total yeast RNA background. The RNA target isolation efficiency was 60% with high specificity. The bind RNA release was 88.8% in a quantity of 0.16 nmol/mg. The total RNA capture efficiency was 53%. Considering this, the MNPs@Ny6 is an attractive candidate for nucleic acids-specific magnetic isolation.

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.

Magnetic Ionic Liquids in Sample Preparation: Recent Advances and Future Trends

In the last decades, a myriad of materials has been synthesized and utilized for the development of sample preparation procedures. The use of their magnetic analogues has gained significant attention and many procedures have been developed using magnetic materials. In this context, the benefits of a new class of magnetic ionic liquids (MILs), as non-conventional solvents, have been reaped in sample preparation procedures. MILs combine the advantageous properties of ionic liquids along with the magnetic properties, creating an unsurpassed combination. Owing to their unique nature and inherent benefits, the number of published reports on sample preparation with MILs is increasing. This fact, along with the many different types of extraction procedures that are developed, suggests that this is a promising field of research. Advances in the field are achieved both by developing new MILs with better properties (showing either stronger response to external magnetic fields or tunable extractive properties) and by developing and/or combining methods, resulting in advanced ones. In this advancing field of research, a good understanding of the existing literature is needed. This review aims to provide a literature update on the current trends of MILs in different modes of sample preparation, along with the current limitations and the prospects of the field. The use of MILs in dispersive liquid–liquid microextraction, single drop microextraction, matrix solid-phase dispersion, etc., is discussed herein among others.

Drop-to-drop liquid-liquid extraction of DNA in an electrowetting-on-dielectric digital microfluidics

Recent advancements in microfluidics and lab-on-a-chip technologies enabled miniaturization and automation of many downstream nucleic acid analysis steps such as PCR. However, DNA extraction/isolation protocol remains a stand-alone sample preparation step. For a quick sample-to-result solution, downstream protocols and sample preparation protocols need to be seamlessly integrated into a single lab-on-a-chip platform. As a step toward such integration, this paper introduces microfluidic DNA isolation using the liquid-liquid extraction (LLE) method in the drop-to-drop (DTD) format. The electrowetting-on-dielectric digital microfluidic platform is capable of handling a two-phase liquid system easily, which enables DTD LLE. In this study, the extraction of plasmid DNA (pDNA) from an aqueous sample to an ionic liquid is demonstrated. Prior to pDNA extraction study, the DTD LLE protocol was developed and optimized using organic dyes as solutes. The selective extraction of pDNA in the presence of proteins as interfering molecules is also demonstrated. This work implies that DTD LLE can substitute for magnetic beads steps in standard DNA isolation protocols.

Selective extraction of low-abundance BRAF V600E mutation from plasma, urine, and sputum using ion-tagged oligonucleotides and magnetic ionic liquids

Sequence-specific DNA extractions have the potential to improve the detection of low-abundance mutations from complex matrices, making them ideal for circulating tumor DNA analysis during the early stages of cancer. Ion-tagged oligonucleotides (ITOs) are oligonucleotides modified with an allylimidazolium salt via thiolene click chemistry. The allylimidazolium-based tag allows the ITO-DNA duplex to be selectively captured by a hydrophobic magnetic ionic liquid (MIL). In this study, the selectivity of the ITO-MIL method was examined by extracting low abundance of the BRAF V600E mutation-a common single-nucleotide polymorphism associated with several different cancers-from diluted human plasma, artificial urine, and diluted artificial sputum. Quantitative polymerase chain reaction (qPCR) was not able to distinguish a 9% BRAF V600E standard (50 fg·μL^-1 BRAF V600E, 500 fg·μL^-1 wild-type BRAF) from the 100% wild-type BRAF (50 fg·μL^-1) standard. However, introducing the ITO-MIL extraction prior to qPCR allowed for samples consisting of 0.1% BRAF V600E (50 fg·μL^-1 V600E BRAF, 50,000 fg·μL^-1 wild-type BRAF) to be distinguished from the 100% wild-type BRAF standard. Ion-tagged oligonucleotides (ITOs) are combined with magnetic ionic liquids (MILs) to extract low-abundance BRAF V600E mutation from diluted human plasma, artificial urine, and diluted artificial sputum. The ITO-MIL extraction prior to qPCR allowed for samples consisting of 0.1% BRAF V600E to be distinguished from the 100% wild-type BRAF standard.

High-throughput approach for the in situ generation of magnetic ionic liquids in parallel-dispersive droplet extraction of organic micropollutants in aqueous environmental samples

In this work, a novel and high-throughput parallel-dispersive droplet extraction (Pa-DDE) based on in situ formation of the hydrophobic MILs ([Co(C₄IM)₄⁺²]2[NTf₂^-], [Ni(C₄IM)₄⁺²]2[NTf₂^-] and [Ni(BeIM)₄⁺²]2[NTf₂^-]) is demonstrated, for the first time, for the determination of benzophenone, metolachlor, triclocarban, pendimethalin, 4-methylbenzylidene camphor, and 2-ethylhexyl-4-methoxycinnamate from aqueous environmental samples. This experimental setup is comprised of a 96-well plate system containing a set of magnetic pins which were used to collect the MIL droplet after in situ formation. This consolidated system enabled simultaneous extraction of up to 96 samples and MIL production in one step. Using this apparatus, sample preparation times of 0.78 min per sample was achieved. The experimental conditions were carefully optimized using uni and multivariate approaches. The optimal conditions were comprised of sample volume of 1.25 mL, 4 mg of [Co(C₄IM)₄⁺²]2[Cl^-] and 40 μL of LiNTf₂ for the in situ formation, and dilution in 20 μL of acetonitrile. The analytical parameters of merit were successfully determined with LODs ranging from 7.5 to 25 μg L^-1 and coefficients of determination higher than 0.989. Intraday and interday precision ranged from 6.4 to 20.6% (n = 3) and 11.6-22.9% (n = 9), respectively, with analyte relative recovery ranging between 53.9 and 129.1%.

Use of Ionic Liquids in Protein and DNA Chemistry

Ionic liquids (ILs) have been receiving much attention as solvents in various areas of biochemistry because of their various beneficial properties over the volatile solvents and ILs availability in myriad variants (perhaps as many as 108) owing to the possibility of paring one cation with several anions and vice-versa as well as formulations as zwitterions. Their potential as solvents lies in their tendency to offer both directional and non-directional forces toward a solute molecule. Because of these forces, ionic liquids easily undergo intermolecular interactions with a range of polar/non-polar solutes, including biomolecules such as proteins and DNA. The interaction of genomic species in aqueous/non-aqueous states assists in unraveling their structure and functioning, which have implications in various biomedical applications. The charge density of ionic liquids renders them hydrophilic and hydrophobic, which retain intact over long-range of temperatures. Their ability in stabilizing or destabilizing the 3D-structure of a protein or the double-helical structure of DNA has been assessed superior to the water and volatile organic solvents. The aptitude of an ion in influencing the structure and stability of a native protein depends on their ranking in the Hofmeister series. However, at several instances, a reverse Hofmeister ordering of ions and specific ion-solute interaction has been observed. The capability of an ionic liquid in terms of the tendency to promote the coiling/uncoiling of DNA structure is noted to rely on the basicity, electrostatic interaction, and hydrophobicity of the ionic liquid in question. Any change in the DNA's double-helical structure reflects a change in its melting temperature (T m), compared to a standard buffer solution. These changes in DNA structure have implications in biosensor design and targeted drug-delivery in biomedical applications. In the current review, we have attempted to highlight various aspects of ionic liquids that influence the structure and properties of proteins and DNA. In short, the review will address the issues related to the origin and strength of intermolecular interactions, the effect of structural components, their nature, and the influence of temperature, pH, and additives on them.

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.

Simultaneous cell lysis and DNA extraction from whole blood using magnetic ionic liquids

Conventional DNA sample preparation methods involve tedious sample handling steps that require numerous inhibitors of the polymerase chain reaction (PCR) and instrumentation to implement. These disadvantages limit the applicability of conventional cell lysis and DNA extraction methods in high-throughput applications, particularly in forensics and clinical laboratories. To overcome these drawbacks, a series of nine hydrophobic magnetic ionic liquids (MILs) previously shown to preconcentrate DNA were explored as cell lysis reagents. The MILs were found to lyse white blood cells from whole blood, 2-fold diluted blood, and dry blood samples while simultaneously extracting human genomic DNA. The identity of metal ion incorporated within the MIL appears to cause hemolysis while the cationic component further reduces the cell's integrity. Over 500 pg of human genomic DNA was isolated from 50 μL of whole blood using the trioctylbenzylammonium tris(hexafluoroacetylaceto)nickelate(II) ([N_8,8,8,Bz⁺][Ni(hfacac)₃^-]) MIL, and 800 pg DNA was isolated from a dry blood samples using the trihexyl(tetradecyl)phosphonium tris(phenyltrifluoroacetylaceto)nickelate(II) ([P_6,6,6,14⁺][Ni(Phfacac)₃^-]) MIL following a 1-min vortex step. A rapid, one-step cell lysis and DNA extraction from blood is ideal for settings that seek high-throughput analysis while minimizing the potential for contamination.Graphical abstract.

Ionic Liquids Toxicity-Benefits and Threats

Ionic liquids (ILs) are solvents with salt structures. Typically, they contain organic cations (ammonium, imidazolium, pyridinium, piperidinium or pyrrolidinium), and halogen, fluorinated or organic anions. While ILs are considered to be environmentally-friendly compounds, only a few reasons support this claim. This is because of high thermal stability, and negligible pressure at room temperature which makes them non-volatile, therefore preventing the release of ILs into the atmosphere. The expansion of the range of applications of ILs in many chemical industry fields has led to a growing threat of contamination of the aquatic and terrestrial environments by these compounds. As the possibility of the release of ILs into the environment s grow systematically, there is an increasing and urgent obligation to determine their toxic and antimicrobial influence on the environment. Many bioassays were carried out to evaluate the (eco)toxicity and biodegradability of ILs. Most of them have questioned their "green" features as ILs turned out to be toxic towards organisms from varied trophic levels. Therefore, there is a need for a new biodegradable, less toxic "greener" ILs. This review presents the potential risks to the environment linked to the application of ILs. These are the following: cytotoxicity evaluated by the use of human cells, toxicity manifesting in aqueous and terrestrial environments. The studies proving the relation between structures versus toxicity for ILs with special emphasis on directions suitable for designing safer ILs synthesized from renewable sources are also presented. The representants of a new generation of easily biodegradable ILs derivatives of amino acids, sugars, choline, and bicyclic monoterpene moiety are collected. Some benefits of using ILs in medicine, agriculture, and the bio-processing industry are also presented.

Allelic discrimination between circulating tumor DNA fragments enabled by a multiplex-qPCR assay containing DNA-enriched magnetic ionic liquids

Multiplex amplification of DNA can be highly valuable in circulating tumor DNA (ctDNA) analysis due to the sheer number of potential mutations. However, commercial ctDNA extraction methods struggle to preconcentrate low concentrations of DNA and require multiple sample handling steps. Recently, magnetic ionic liquids (MILs) have been used to extract DNA and were integrated with a quantitative polymerase chain reaction (qPCR). However, in previous studies, DNA could not be preconcentrated from plasma and only one fragment could be amplified per reaction. In this study, MILs were utilized as DNA extraction solvents and directly integrated into a multiplex-qPCR buffer to simultaneously amplify wild-type KRAS, G12S KRAS, and wild-type BRAF, three clinically-relevant genes whose mutation status can affect the success of anti-EGFR therapy. DNA was desorbed from the MIL solvent during a multiplex-PCR without having a significant effect on the amplification efficiency, and allelic discrimination of single-nucleotide polymorphisms could still be achieved. Enrichment factors over 35 for all three sequences were achieved from Tris buffer using the [N_8,8,8,Bz⁺][Ni(hfacac)₃^-]) and [P_6,6,6,14⁺][Ni(Phtfacac)₃^-] MILs. DNA could still be preconcentrated from 2-fold diluted human plasma using the [N_8,8,8,Bz⁺][Ni(hfacac)₃^-] MIL. Extractions from undiluted plasma were reproducible with the [P_6,6,6,14⁺][Ni(Phtfacac)₃^-] MIL although DNA was not preconcentrated with enrichment factors around 0.6 for all three fragments. Compared to commercial DNA extraction methods (i.e., silica-based spin columns and magnetic beads), the MIL-based extraction achieved higher enrichment factors in Tris buffer and plasma. The ability of the MIL-based dispersive liquid-liquid microextraction (DLLME) direct-multiplex-qPCR method to simultaneously achieve high enrichment factors of multiple DNA fragments from human plasma is highly promising in the field of ctDNA detection.