Using an aqueous two-phase polymer-salt system to rapidly concentrate viruses for improving the detection limit of the lateral-flow immunoassay

Sensitive Colorimetric Lateral Flow Assays Enabled by Platinum-Group Metal Nanoparticles with Peroxidase-Like Activities

The last several decades have witnessed the success and popularity of colorimetric lateral flow assay (CLFA) in point-of-care testing. Driven by increasing demand, great efforts have been directed toward enhancing the detection sensitivity of CLFA. Recently, platinum-group metal nanoparticles (PGM NPs) with peroxidase-like activities have emerged as a type of promising colorimetric labels for enhancing the sensitivity of CLFA. By incorporating a simple and rapid post-treatment process, the PGM NP-based CLFAs are orders of magnitude more sensitive than conventional gold nanoparticle-based CLFAs. In this perspective, the study begins with introducing the design, synthesis, and characterization of PGM NPs with peroxidase-like activities. The current techniques for surface modification of PGM NPs are then discussed, followed by operation and optimization of PGM NP-based CLFAs. Afterward, opinions are provided on the social impact of PGM NP-based CLFAs. Lastly, this perspective is concluded with an outlook of future research directions in this emerging field, where the challenges and opportunities are discussed.

Affinity-Controlled Partitioning of Biomolecules at Aqueous Interfaces and Their Bioanalytic Applications

All-aqueous phase separation systems play essential roles in bioanalytical and biochemical applications. Compared to conventional oil and organic solvent-based systems, these systems are characterized by their rich bulk and interfacial properties, offering superior biocompatibility. In particular, phase separation in all-aqueous systems facilitates the creation of compartments with specific physicochemical properties, and therefore largely enhances the accessibility of the systems. In addition, the all-aqueous compartments have diverse affinities, with an important property known as partitioning, which can concentrate (bio)molecules toward distinct immiscible phases. This partitioning affinity imparts all-aqueous interfaces with selective permeability, enabling the controlled enrichment of target (bio)molecules. This review introduces the basic principles and applications of partitioning-induced interfacial phenomena in a typical all-aqueous system, namely aqueous two-phase systems (ATPSs); these applications include interfacial chemical reactions, bioprinting, and assembly, as well as bio-sensing and detection. The primary challenges associated with designing all-aqueous phase separation systems and several future directions are also discussed, such as the stabilization of aqueous interfaces, the handling of low-volume samples, and exploration of suitable ATPSs compositions with the efficient protocol.

Investigating bottom phase extraction from aqueous two-phase systems for detecting bacteria using the lateral-flow immunoassay

Lateral-flow immunoassays (LFAs) can be used to diagnose urinary tract infections caused by Escherichia coli (E. coli) at the point of care. Unfortunately, urine samples containing dilute concentrations of E. coli can yield false negative results on LFAs. Our laboratory was first to implement aqueous two-phase systems (ATPSs) to preconcentrate samples into smaller volumes prior to their application on LFAs. This is achieved by manipulating the ratio of the volume of the top phase to that of the bottom phase (volume ratio; VR) and concentrating biomarkers in the bottom phase which, when applied to LFAs in fixed volumes, leads to corresponding improvements in sensitivity. This work is the first demonstration that the same LOD can be achieved irrespective of the VR when the entire bottom phase is added to LFAs. A custom 3D-printed device was also developed to decrease liquid handling steps. Across different VRs expected from patient urine variability, this diagnostic workflow successfully detected E. coli concentrations down to 2 × 105 colony-forming units (cfu) mL-1 in synthetic urine, demonstrating consistent 10-fold improvements in sensitivity compared to trials conducted without ATPS preconcentration. This method successfully addresses the variability of patient samples while remaining easy to use at the point of care.

Recent advances in drug delivery applications of aqueous two-phase systems

Aqueous two-phase systems (ATPSs) are liquid-liquid equilibria between two aqueous phases that usually contain over 70% water content each, which results in a nontoxic organic solvent-free environment for biological compounds and biomolecules. ATPSs have attracted significant interest in applications for formulating carriers (microparticles, nanoparticles, hydrogels, and polymersomes) which can be prepared using the spontaneous phase separation of ATPSs as a driving force, and loaded with a wide range of bioactive materials, including small molecule drugs, proteins, and cells, for delivery applications. This review provides a detailed analysis of various ATPSs, including strategies employed for particle formation, polymerization of droplets in ATPSs, phase-guided block copolymer assemblies, and stimulus-responsive carriers. Processes for loading various bioactive payloads are discussed, and applications of these systems for drug delivery are summarized and discussed.

Multimodal peptide ligand extracts parvovirus from interface in affinity aqueous two-phase system

Aqueous two-phase systems (ATPS) have found various applications in bioseparations and microencapsulation. The primary goal of this technique is to partition target biomolecules in a preferred phase, rich in one of the phase-forming components. However, there is a lack of understanding of biomolecule behavior at the interface between the two phases. Biomolecule partitioning behavior is studied using tie-lines (TL), where each TL is a group of systems at thermodynamic equilibrium. Across a TL, a system can either have a bulk PEG-rich phase with citrate-rich droplets, or the opposite can occur. We found that porcine parvovirus (PPV) was recovered at a higher amount when PEG was the bulk phase and citrate was in droplets and that the salt and PEG concentrations are high. To improve the recovery, A PEG 10 kDa-peptide conjugate was formed using the multimodal WRW ligand. When WRW was present, less PPV was caught at the interface of the two-phase system, and more was recovered in the PEG-rich phase. While WRW did not significantly increase the PPV recovery in the high TL system, which was found earlier to be optimal for PPV recovery, the peptide did greatly enhance recovery at a lower TL. This lower TL has a lower viscosity and overall system PEG and citrate concentration. The results provide both a method to increase virus recovery in a lower viscosity system, as well as provide interesting thoughts into the interfacial phenomenon and how to recover virus in a phase and not at the interface.

Application of the aqueous two-phase system and nanozyme signal enhancement for the improved detection of Plasmodium lactate dehydrogenase in serum

Malaria is an infectious disease that can cause severe sickness and death if not diagnosed and treated in a timely manner. The current gold standard technique for malaria diagnosis is microscopy, which requires a dedicated laboratory setting and trained personnel and can have a long time to result. These requirements can be alleviated using paper-based diagnostic devices that enable rapid and inexpensive diagnosis at the point of care, which can allow patients to receive treatment before their symptoms progress when used for early detection of diseases. The lateral-flow immunoassay (LFA) is one such device, but currently available LFAs are susceptible to false negative results caused by low parasite density. To improve sensitivity and detection, we utilized the aqueous two-phase system (ATPS) to concentrate and purify the sample, and nanozyme signal enhancement to increase the intensity of the visible signal on the test strip. We were able to achieve a limit of detection (LOD) of 0.01 ng/mL for the malaria biomarker Plasmodium lactate dehydrogenase (pLDH) in human serum using a multi-step assay combining the LFA format with the ATPS and nanozyme signal enhancement.

Using the forces of hydrodynamic countercurrent chromatography for the study of bacteriophages

Bacteriophages (phages) are viruses that target bacteria, with the ability to lyse and kill host bacterial cells. Due to this, they have been of some interest as a therapeutic since their discovery in the early 1900s, but with the recent increase in antibiotic resistance, phages have seen a resurgence in attention. Current methods of isolation and purification of phages can be long and tedious, with caesium chloride concentration gradients the gold standard for purifying a phage fraction. Isolation of novel phages requires centrifugation and ultrafiltration of mixed samples, such as water sources, effluent or faecal samples etc, to prepare phage filtrates for further testing. We propose countercurrent chromatography as a novel and alternative approach to use when studying phages, as a scalable and high-yield method for obtaining phage fractions. However, the full extent of the usefulness and resolution of separation with this technique has not been researched; it requires optimization and ample testing before this can be revealed. Here we present an initial study to determine survivability of two phages, T4 and ϕX174, using only water as a mobile phase in a Spectrum Series 20 HPCCC. Both phages were found to remain active once eluted from the column. Phages do not fully elute from the column and sodium hydroxide is necessary to flush the column between runs to deactivate remaining phages.

On-demand nanozyme signal enhancement at the push of a button for the improved detection of SARS-CoV-2 nucleocapsid protein in serum

We developed an innovative 3D printed casing that incorporates a lateral-flow immunoassay, dehydrated signal enhancement reagents, and a sealed buffer chamber. With only the push of a button for signal enhancement, our device detected the SARS-CoV-2 N-protein in 40 min at concentrations as low as 0.1 ng mL^-1 in undiluted serum.

Aqueous Two-Phase Systems and Microfluidics for Microscale Assays and Analytical Measurements

Phase separation is a common occurrence in nature. Synthetic and natural polymers, salts, ionic liquids, surfactants, and biomacromolecules phase separate in water, resulting in an aqueous two-phase system (ATPS). This review discusses the properties, handling, and uses of ATPSs. These systems have been used for protein, nucleic acid, virus, and cell purification and have in recent years found new uses for small organics, polysaccharides, extracellular vesicles, and biopharmaceuticals. Analytical biochemistry applications such as quantifying protein-protein binding, probing for conformational changes, or monitoring enzyme activity have been performed with ATPSs. Not only are ATPSs biocompatible, they also retain their properties at the microscale, enabling miniaturization experiments such as droplet microfluidics, bacterial quorum sensing, multiplexed and point-of-care immunoassays, and cell patterning. ATPSs include coacervates and may find wider interest in the context of intracellular phase separation and origin of life. Recent advances in fundamental understanding and in commercial application are also considered.

Osmolyte enhanced aqueous two-phase system for virus purification

Due to the high variation in viral surface properties, a platform method for virus purification is still lacking. A potential alternative to the high-cost conventional methods is aqueous two-phase systems (ATPSs). However, optimizing virus purification in ATPS requires a large experimental design space, and the optimized systems are generally found to operate at high ATPS component concentrations. The high concentrations capitalize on hydrophobic and electrostatic interactions to obtain high viral particle yields. This study investigated using osmolytes as driving force enhancers to reduce the high concentration of ATPS components while maintaining high yields. The partitioning behavior of porcine parvovirus (PPV), a nonenveloped mammalian virus, and human immunodeficiency virus-like particle (HIV-VLP), a yeast-expressed enveloped VLP, were studied in a polyethylene glycol (PEG) 12 kDa-citrate system. The partitioning of the virus modalities was enhanced by osmoprotectants glycine and betaine, while trimethylamine N-oxide was ineffective for PPV. The increased partitioning to the PEG-rich phase pertained only to viruses, resulting in high virus purification. Recoveries were 100% for infectious PPV and 92% for the HIV-VLP, with high removal of the contaminant proteins and more than 60% DNA removal when glycine was added. The osmolyte-induced ATPS demonstrated a versatile method for virus purification, irrespective of the expression system.

Thermostabilization of viruses via complex coacervation

Widespread vaccine coverage for viral diseases could save the lives of millions of people each year. For viral vaccines to be effective, they must be transported and stored in a narrow temperature range of 2-8 °C. If temperatures are not maintained, the vaccine may lose its potency and would no longer be effective in fighting disease; this is called the cold storage problem. Finding a way to thermally stabilize a virus and end the need to transport and store vaccines at refrigeration temperatures will increase access to life-saving vaccines. We explore the use of polymer-rich complex coacervates to stabilize viruses. We have developed a method of encapsulating virus particles in liquid complex coacervates that relies on the electrostatic interaction of viruses with polypeptides. In particular, we tested the incorporation of two model viruses; a non-enveloped porcine parvovirus (PPV) and an enveloped bovine viral diarrhea virus (BVDV) into coacervates formed from poly(lysine) and poly(glutamate). We identified optimal conditions (i.e., the relative amount of the two polypeptides) for virus encapsulation, and trends in this composition matched differences in the isoelectric point of the two viruses. Furthermore, we were able to achieve a ∼103-104-fold concentration of virus into the coacervate phase, such that the level of virus remaining in the bulk solution approached our limit of detection. Lastly, we demonstrated a significant enhancement of the stability of non-enveloped PPV during an accelerated aging study at 60 °C over the course of a week. Our results suggest the potential for using coacervation to aid in the purification and formulation of both enveloped and non-enveloped viruses, and that coacervate-based formulations could help limit the need for cold storage throughout the transportation and storage of vaccines based on non-enveloped viruses.

Automation of Biomarker Preconcentration, Capture, and Nanozyme Signal Enhancement on Paper-Based Devices

Infectious diseases remain one of the leading causes of deaths in developing countries because of a lack of basic sanitation, healthcare clinics, and centralized laboratories. Paper-based rapid diagnostic tests, such as the lateral-flow immunoassay (LFA), provide a promising alternative to the traditional laboratory-based tests; however, they typically suffer from having a poor sensitivity. Biomarker preconcentration and signal enhancement are two common methods to improve the sensitivity of paper-based assays. While effective, these methods often require multiple liquid handling steps which are not ideal for use by untrained personnel in a point-of-care setting. Our lab previously discovered the phenomenon of an aqueous two-phase system (ATPS) separating on paper, which allowed for the seamless integration of concentration and detection of biomarkers on the LFA. In this work, we have extended the functionality of an ATPS separating on paper to automate the sequential delivery of signal enhancement reagents in addition to concentrating biomarkers. The timing of reagent delivery was controlled by changing the initial composition of the ATPS. We applied this technology to automate biomarker concentration and nanozyme signal enhancement on the LFA, resulting in a 30-fold improvement in detection limit over the conventional LFA when detecting Escherichia coli, all while maintaining a single application step.

A one-pot, isothermal DNA sample preparation and amplification platform utilizing aqueous two-phase systems

Infectious diseases remain one of the major causes of death worldwide in developing countries. While screening via conventional polymerase chain reaction (PCR) is the gold standard in laboratory testing, its limited applications at the point-of-care have prompted the development of more portable nucleic acid detection systems. These include isothermal DNA amplification techniques, which are less equipment-intensive than PCR. Unfortunately, these techniques still require extensive sample preparation, limiting user accessibility. In this study, we introduce a novel system that combines thermophilic helicase-dependent amplification (tHDA) with a Triton X-100 micellar aqueous two-phase system (ATPS) to achieve cell lysis, lysate processing, and enhanced nucleic acid amplification in a simple, one-step process. The combined one-pot system was able to amplify and detect a target gene from whole-cell samples containing as low as 10² cfu/mL, and is the first known application of ATPSs to isothermal DNA amplification. This system's ease-of-use and sensitivity underlie its potential as a point-of-care diagnostic platform to detect for infectious diseases. Graphical abstract ᅟ.

Aminolated and Thiolated PEG-Covered Gold Nanoparticles with High Stability and Antiaggregation for Lateral Flow Detection of Bisphenol A

The few lateral flow assays (LFAs) established for detecting the endocrine disrupting chemical bisphenol A (BPA) have employed citrate-stabilized gold nanoparticles (GNPs), which have inevitable limitations and instability issues. To address these limitations, a more stable and more sensitive biosensor is developed by designing strategies for modifying the surfaces of GNPs with polyethylene glycol and then testing their effectiveness and sensitivity toward BPA in an LFA. Without the application of any enhancement strategy, this modified BPA LFA can achieve a naked-eye limit of detection (LOD) of 0.8 ng mL^-1 , which is 12.5 times better than the LOD of regular BPA LFAs, and a quantitative LOD of 0.472 ng mL^-1 . This modified LFA has the potential to be applied to the detection of various antigens.

Emerging Biotechnology Applications of Aqueous Two-Phase Systems

Liquid-liquid phase separation between aqueous solutions containing two incompatible polymers, a polymer and a salt, or a polymer and a surfactant, has been exploited for a wide variety of biotechnology applications throughout the years. While many applications for aqueous two-phase systems fall within the realm of separation science, the ability to partition many different materials within these systems, coupled with recent advances in materials science and liquid handling, has allowed bioengineers to imagine new applications. This progress report provides an overview of the history and key properties of aqueous two-phase systems to lend context to how these materials have progressed to modern applications such as cellular micropatterning and bioprinting, high-throughput 3D tissue assembly, microscale biomolecular assay development, facilitation of cell separation and microcapsule production using microfluidic devices, and synthetic biology. Future directions and present limitations and design considerations of this adaptable and promising toolkit for biomolecule and cellular manipulation are further evaluated.

All-Aqueous Assemblies via Interfacial Complexation: Toward Artificial Cell and Microniche Development

In nature, the environment surrounding biomolecules and living cells can dictate their structure, function, and properties. Confinement is a key means to define and regulate such environments. For example, the confinement of appropriate constituents in compartments facilitates the assembly, dynamics, and function of biochemical machineries as well as subcellular organelles. Membraneless organelles, in particular, are thought to form via thermodynamic cues defined within the interior space of cells. On larger length scales, the confinement of living cells dictates cellular function for both mammalian and bacterial cells. One promising class of artificial structures that can recapitulate these multiscale confinement effects is based on aqueous two-phase systems (ATPSs). This feature article highlights recent developments in the production and stabilization of ATPS-droplet-based systems, with a focus on interfacial complexation. These systems enable structure formation, modulation, and triggered (dis)assembly, thereby allowing structures to be tailored to fit the desired function and designed for particular confinement studies. Open issues for both synthetic cells and niche studies are identified.

Practical aspects of the automated preparation of aqueous two phase systems for the analysis of biological macromolecules

A robust strategy for the automated preparation of aqueous two-phase systems (ATPS) using a liquid handling sample processor was developed using gravimetric methods: to determine the accuracy of preparation. The major robotic control parameters requiring adjustment were; speed of aspiration and dispense; delay times following aspiration and dispense alongside measures to control cross-contamination during phase sampling. In general mixture compositions of both polymer/polymer and polymer/salt mixtures could be prepared with a target bias accuracy of less than 5%. However, we found that the bias accuracy with which systems of defined TLL and MR could be constructed was highly dependent on the tie line length of the ATPS and the geometrical form of the ATPS co-existence curve. For systems with a very low degree of curvature (PEG/salt systems here) increases in bias (accuracy) are appreciable at relatively long tie line lengths. Where the degree of curvature is more pronounced (PEG/dextran systems) closer approach to the critical point was possible without major effect on bias/accuracy. Application of the strategy to the measurement of the partitioning of phosphorylated and dephosphorylated forms of the model protein ovalbumin are reported. Differences in partition of phosphorylated (native) forms and dephosphorylated forms could be demonstrated. In a PEG/salt system this was manifest as a substantial decrease in solubility based on overall protein recovery derived from accurate knowledge of the system mass ratio. In a PEG/dextran system differences in partition coefficient could be demonstrated between phosphorylated and dephosphorylated forms.

A Combined Aqueous Two-Phase System and Spot-Test Platform for the Rapid Detection of Escherichia coli O157:H7 in Milk

Foodborne illnesses are a public health concern in the United States and worldwide. Recent outbreaks of Escherichia coli O157:H7 have brought to light the need for improved ways to detect foodborne pathogens and minimize serious outbreaks. Unfortunately, current methods for the detection of foodborne pathogens are time intensive and complex. In this study, we designed a spot immunoassay that uses a UCON-potassium phosphate salt aqueous two-phase system (ATPS) for the preconcentration of O157:H7. This platform was tested with samples of O157:H7 spiked in phosphate-buffered saline and milk. The ATPS was found to improve the detection limit of the spot test, yielding detection at 106 cfu/mL within 30 min. This is the first known application of ATPSs to spot immunoassays. Moreover, detection was successfully achieved without upstream processing or dilution of the sample prior to testing, thereby further simplifying the detection process. This technology’s ease of use, sensitivity, and short time to result highlight its potential to advance the spot test as a viable diagnostic tool for foodborne pathogens.

Dual RNA-seq reveals viral infections in asthmatic children without respiratory illness which are associated with changes in the airway transcriptome

Background

Respiratory illness caused by viral infection is associated with the development and exacerbation of childhood asthma. Little is known about the effects of respiratory viral infections in the absence of illness. Using quantitative PCR (qPCR) for common respiratory viruses and for two genes known to be highly upregulated in viral infections (CCL8/CXCL11), we screened 92 asthmatic and 69 healthy children without illness for respiratory virus infections.

Results

We found 21 viral qPCR-positive and 2 suspected virus-infected subjects with high expression of CCL8/CXCL11. We applied a dual RNA-seq workflow to these subjects, together with 25 viral qPCR-negative subjects, to compare qPCR with sequencing-based virus detection and to generate the airway transcriptome for analysis. RNA-seq virus detection achieved 86% sensitivity when compared to qPCR-based screening. We detected additional respiratory viruses in the two CCL8/CXCL11-high subjects and in two of the qPCR-negative subjects. Viral read counts varied widely and were used to stratify subjects into Virus-High and Virus-Low groups. Examination of the host airway transcriptome found that the Virus-High group was characterized by immune cell airway infiltration, downregulation of cilia genes, and dampening of type 2 inflammation. Even the Virus-Low group was differentiated from the No-Virus group by 100 genes, some involved in eIF2 signaling.

Conclusions

Respiratory virus infection without illness is not innocuous but may determine the airway function of these subjects by driving immune cell airway infiltration, cellular remodeling, and alteration of asthmogenic gene expression.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-016-1140-8) contains supplementary material, which is available to authorized users.

Development of quantitative radioactive methodologies on paper to determine important lateral-flow immunoassay parameters

The lateral-flow immunoassay (LFA) is a well-established diagnostic technology that has recently seen significant advancements due in part to the rapidly expanding fields of paper diagnostics and paper-fluidics. As LFA-based diagnostics become more complex, it becomes increasingly important to quantitatively determine important parameters during the design and evaluation process. However, current experimental methods for determining these parameters have certain limitations when applied to LFA systems. In this work, we describe our novel methods of combining paper and radioactive measurements to determine nanoprobe molarity, the number of antibodies per nanoprobe, and the forward and reverse rate constants for nanoprobe binding to immobilized target on the LFA test line. Using a model LFA system that detects for the presence of the protein transferrin (Tf), we demonstrate the application of our methods, which involve quantitative experimentation and mathematical modeling. We also compare the results of our rate constant experiments with traditional experiments to demonstrate how our methods more appropriately capture the influence of the LFA environment on the binding interaction. Our novel experimental approaches can therefore more efficiently guide the research process for LFA design, leading to more rapid advancement of the field of paper-based diagnostics.

Human Immunodeficiency Virus (HIV) Separation and Enrichment via the Combination of Antiviral Lectin Recognition and a Thermoresponsive Reagent System

PURPOSE

In order to improve the detection limit of existing HIV diagnostic assays, we explored the use of a temperature-responsive magnetic nanoparticle reagent system in conjunction with cyanovirin-N for HIV recognition to rapidly and efficiently concentrate viral particles from larger sample volumes, ~ 1 ml.

METHODS

Cyanovirin-N (CVN) mutant, Q62C, was expressed, biotinylated, and then complexed with a thermally responsive polymer-streptavidin conjugate. Confirmation of protein expression/activity was performed using matrix assisted laser desorption/ionization (MALDI) and a TZM-bl HIV inhibition assay. Biotinylated CVN mutant recognition with gp120 was characterized using surface plasmon resonance (SPR). Virus separation and enrichment using a thermoresponsive magnetic nanoparticle reagent system were measured using RT-PCR.

RESULTS

Biotinylated Q62C exhibited a KD of 0.6 nM to gp120. The temperature-responsive binary reagent system achieved a maximum viral capture of nearly 100% HIV, 1 × 10(5) virus copies in 100 μl, using pNIPAAm-Q62C within 30 minutes. Additionally, the same reagent system achieved nearly 9-fold enrichment by processing a 10-times larger sample of 1000 μl (Fig. 3).

CONCLUSION

This work demonstrated a temperature-responsive reagent system that provides enrichment of HIV using antiviral lectin CVN for recognition, which is potentially amenable for use in point-of-care settings.

An Aqueous Two-Phase System for the Concentration and Extraction of Proteins from the Interface for Detection Using the Lateral-Flow Immunoassay

The paper-based immunoassay for point-of-care diagnostics is widely used due to its low cost and portability over traditional lab-based assays. Lateral-flow immunoassay (LFA) is the most well-established paper-based assay since it is rapid and easy to use. However, the disadvantage of LFA is its lack of sensitivity in some cases where a large sample volume is required, limiting its use as a diagnostic tool. To improve the sensitivity of LFA, we previously reported on the concentration of analytes into one of the two bulk phases of an aqueous two-phase system (ATPS) prior to detection. In this study, we preserved the advantages of LFA while significantly improving upon our previous proof-of-concept studies by employing a novel approach of concentrating gold nanoparticles, a common LFA colorimetric indicator. By conjugating specific antibodies and polymers to the surfaces of the particles, these gold nanoprobes (GNPs) were able to capture target proteins in the sample and subsequently be concentrated within 10 min at the interface of an ATPS solution comprised of polyethylene glycol, potassium phosphate, and phosphate-buffered saline. These GNPs were then extracted and applied directly to LFA. By combining this prior ATPS interface extraction with LFA, the detection limit of LFA for a model protein was improved by 100-fold from 1 ng/μL to 0.01 ng/μL. Additionally, we examined the behavior of the ATPS system in fetal bovine serum and synthetic urine to more closely approach real-world applications. Despite using more complex matrices, ATPS interface extraction still improved the detection limit by 100-fold within 15 to 25 min, demonstrating the system’s potential to be applied to patient samples.