LC-based Sensor Research Articles

Real-time detection of Tau-381 protein using liquid crystal-based sensors for Alzheimer's disease diagnosis

Tau is a protein found in the central nervous system (CNS) and is involved in stabilizing microtubules in axons. Given the link between Tau levels in the body and Alzheimer's disease (AD), there is a demand for straightforward and precise strategies to detect Tau in body fluids. In this study, we report liquid crystal (LC)-based sensors for the real-time detection of Tau protein, a well-known AD biomarker. The sensor uses a detection method based on the orientation change of the LC because of the competitive biomolecular interaction between Tau and Tau aptamers with the cationic polymer poly-L-lysine (PLL). Tau and its aptamers form stable complexes through electrostatic interactions. Owing to the consumption of the aptamer, the positively charged PLL fails to interact with the aptamer but binds to the negatively charged 1.2-dioleoyl-sn-glycero-3-phospho-(1′-rac-glycerol) sodium salt (DOPG). The PLL and DOPG complex alters the orientation of the LC to ensure a planar anchoring of the 4-cyano-4′-pentylbiphenyl (5CB)/aqueous interface; this anchoring intensifies with increasing Tau concentration, thus enabling the observation of a bright optical image. Our LC-based sensor demonstrated a low detection limit of 2.77 pg/mL in phosphate buffered saline (PBS) and 10.86 pg/mL and 19.31 pg/mL in human serum and plasma, respectively. Moreover, it is anticipated to be suitable for point-of-care diagnosis of AD because it does not require specialized analytical equipment and only requires microliters of sample.

Harnessing Liquid Crystal Sensors for High-Throughput Real-Time Detection of Structural Changes in Lysozyme during Refolding Processes.

Despite the rapid advances in process analytical technology, the assessment of protein refolding efficiency has largely relied on off-line protein-specific assays and/or chromatographic procedures such as reversed-phase high-performance liquid chromatography and size exclusion chromatography. Due to the inherent time gap pertaining to traditional methods, exploring optimum refolding conditions for many recombinant proteins, often expressed as insoluble inclusion bodies, has proven challenging. The present study describes a novel protein refolding sensor that utilizes liquid crystals (LCs) to discriminate varying protein structures during unfolding and refolding. An LC layer containing 4-cyano-4'-pentylbiphenyl (5CB) intercalated with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) is used as a sensing platform, and its proof-of-concept performance is demonstrated using lysozyme as a model protein. As proteins unfold or refold, a local charge fluctuation at their surfaces modulates their interaction with zwitterionic phospholipid DOPE. This alters the alignment of DOPE molecules at the aqueous/LC interface, affecting the orientational ordering of bulk LC (i.e., homeotropic to planar for refolding and planar to homeotropic for unfolding). Differential polarized optical microscope images of the LC layer are subsequently generated, whose brightness directly linked to conformational changes of lysozyme molecules is quantified by gray scale analysis. Importantly, our LC-based refolding sensor is compatible with diverse refolding milieus for real-time analysis of lysozyme refolding and thus likely to facilitate the refolding studies of many proteins, especially those lacking a method to determine structure-dependent biological activity.

A cost-effective label-free biosensor for rapid detection of multiple viral respiratory infections base on liquid crystals: Fabrication and modeling

The high transmission rate and incurability of recurrent Herpes Simplex Virus (HSV) infection require an accurate and fast detection approach for its efficient prevention. In an attempt to find a novel sensitive and simple optical diagnostic technique which enables on-spot testing, here we developed label-free biosensors based on E7 nematic liquid crystals (LCs) for specific detection of HSV DNA. For this purpose, homeotropically oriented LCs as smart materials are spread on the textile grid to make their both upper and lower surfaces be in contact with ambient air. HSV DNA of concentration between 1.4 nM and 5.5 nM is added to the platform, and DNA elution buffer is used as a control. Then, the reorientation of LCs occurs due to the coupling of electrical dipoles between LCs and DNA molecules. Creating a unique pattern that is projected onto CCD by putting the sample in a cross-polarizer and using white light. To model the LC's director distribution, LC's free energy equation is solved using the variational method and finite difference method (FDM). Overall, our LC-based sensor is a user-friendly, cost-effective, highly sensitive, and fast way for specific detection of HSV without the need for experts and expensive equipment.

Construction of Liquid Crystal-Based Sensors Using Enzyme-Linked Dual-Functional Nucleic Acid on Magnetic Beads.

The development of liquid crystal (LC)-based sensors with superior performances such as high portability, excellent stability, great convenience, and remarkable sensitivity is highly demanded. This work proposes a new strategy for constructing the LC-based sensor using enzyme-linked dual-functional nucleic acid (d-FNA) on magnetic beads (MBs). The detection of kanamycin (KA) is demonstrated as a model. Acetylcholinesterase (AChE) is assembled onto the KA aptamer-modified MBs with a d-FNA strand that consists of an AChE aptamer and the complementary sequence of a KA aptamer. As the specific recognition of KA by its aptamer triggers the release of AChE from the MBs, the myristoylcholine (Myr) solution after incubation with the MBs causes the black image of the LCs due to the formation of the Myr monolayer at the aqueous/LC interface. Otherwise, in the absence of KA, AChE is still decorated on the MBs and causes the hydrolysis of Myr. Therefore, a bright image of LCs is obtained. The detection of KA is successfully achieved with a lower detection limit of 48.1 pg/mL. In addition, a thin polydimethylsiloxane (PDMS) layer-coated glass and a portable optical device are used to improve the stability and portability of the LC-based sensor to advance potential commercial applications. Furthermore, the detection of KA in milk with a portable device is demonstrated, showing the potential of the proposed enzyme-linked LC-based sensor.

Ultra-trace level detection of nickel(II) ions in real water samples using surface anchored recognition probes at liquid crystal sensing platform

Rational fabrication approach for ultra-trace level detection of nickel (Ni(II)) ions in water samples has been developed using surface anchored recognition probes at liquid crystal sensing platform. In this system, the optimized volume per cent (5:1, %v/v) of synthesized surface anchored diacetate probes along with DMOAP decorated on glass substrate is able to perfectly align 5-cyanobiphenyl (5-CB) liquid crystal (LC) giving dark textural pattern. On the other hand, the fabricated probe is able to selectively reorient the transitions of the decorated LC molecules in the presence of Ni(II) ions too, leading to bright textural pattern under cross polarizers. The optimized and fabricated system demonstrated high selectivity and sensitivity, detecting Ni(II) ions as low as 0.08 μM (∼4.7 ppb) in distilled water and 0.8 μM (∼47 ppb) in real water with results observable to the naked eye. Moreover, the sensor can detect Ni(II) in drinking water, providing an approach to develop LC-based sensor for detection of natural water contaminants with simplified operating techniques.

A liquid crystal-based sensor exploiting the aptamer-mediated recognition at the aqueous/liquid crystal interface for sensitive detection of serotonin.

We report here a liquid crystal (LC)-based sensor for detecting serotonin (5-HT); the proposed sensor uses target-specific aptamer recognition at a cationic surfactant decorated-aqueous/LC interface. Our detection strategy focuses on the orientational transition of LCs upon biological interactions at the interface. In this sensing system, the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) forms a self-assembled monolayer at the aqueous/LC interface and triggers the homeotropic orientation of LCs. After introducing the 5-HT specific aptamer, an electrostatic attraction occurs between the cationic CTAB and anionic aptamer. This interaction destructs the surfactant monolayer at the interface, inducing reorganization of LC alignment from homeotropic to tilted conditions. In the increasing 5-HT levels, specific binding between 5-HT and the aptamer diminishes the interaction between the aptamer and CTAB, thereby maintaining the homeotropic alignment of LCs. The orientational transition of the LCs was observed under a polarized optical microscope. The developed biosensor has a linear detection range from 1 to 1000nM and a detection limit of 1.68nM. Moreover, the sensor was applied to a human urine sample and a detection limit of 2.25nM was obtained. Overall, the designed LC-based sensor is a sensitive, simple, cost effective, and selective platform for detecting 5-HT in aqueous solutions.

Surface modification strategy of boronic acids on glass substrates and its application for detecting glycated hemoglobin by liquid crystal-based sensors

Surface modification is a fundamental technique in the development of chemical sensors and biosensors. In this work, we established a strategy to incorporate boronic acids into the structure of polyethylenimine (PEI) through a multi-component reaction under microwave conditions. The presence of boronic acids on PEI was identified by NMR and IR spectroscopy. This borylated PEI polymer was coated on the glass substrate and its binding activity was tested by using 5-(diethylamino)-2-((methylimino)methyl)phenol (DAHMI) as a fluorescence tag. Moreover, the boronic acid-modified surface was applied to construct a liquid crystal (LC)-based sensor system for detecting glycated hemoglobin (HbA1C). The specific binding of HbA1C to boronic acid on glass surface lead to the reorientation of LCs, such that a dark-to-bright optical transition was observed under polarized light. Based on this mechanism, the limit of detection of the LC-based sensor for HbA1C was 100 μg/mL with good specificity. Our results demonstrated the applicability of the surface modification strategy of boronic acids on glass substrates for developing chemical sensors and biosensors.

Liquid crystal-based sensitive and selective detection of uric acid and uricase in body fluids

The abnormal levels of uric acid (UA) in body fluids are associated with gout, type (II) diabetes, leukemia, Lesch-Nyhan syndrome, uremia, kidney damage, and cardiovascular diseases. Also, the presence of uricase (UOx) symbolizes genetic disorders and corresponding complications. Therefore, the detection of UA and UOx in the body fluids is significant for clinical diagnosis. 4-Cyano-4′-pentylbiphenyl (5CB, a nematic liquid crystal (LC)) was doped with octadecyl trimethylammonium bromide (OTAB, a cationic surfactant), which formed a self-assembled monolayer at the aqueous/5CB interface. The UOx-catalyzed oxidation of UA yielded H2O2, releasing the single-strand deoxyribonucleic acid (ssDNA) from the nanoceria/ssDNA complex. The interaction of the released ssDNA with OTAB disrupted the monolayer at the aqueous/5CB interface, which resulted in a dark to bright change when observed through a polarized optical microscope. The LC-based sensor allowed the detection of UA with a linear range of 0.01–10 μM and a limit of detection (LOD) of 0.001 μM. The UA detection was also performed in human urine samples and the results were comparable to that of a standard commercial colorimetric method. Similarly, the detection of UOx was performed, with a noted linear range of 20–140 μg/mL. The LOD was as low as 0.34 μg/mL. The detection of UOx was also demonstrated in human serum samples with excellent performance. This method provides a robust sensing platform for the detection of UA and UOx and has potential for applications in clinical analysis.

Ultra-sensitive DNAzyme-based optofluidic biosensor with liquid crystal-Au nanoparticle hybrid amplification for molecular detection

Due to the specific cofactor dependence and the potent catalytic capability, DNAzymes have shown great promise in the application of biosensors. However, it poses significant challenges for researchers to enhance the sensitivities of DNAzyme-based biosensing platforms. In this work, an ultra-sensitive, label-free, and quick-responsive DNAzyme biosensor is developed based on whispering gallery mode (WGM) optofluidic resonator with a hybrid amplification from liquid crystals (LCs) and Au nanoparticles (AuNPs). When a DNAzyme is cleaved by biotargets, the event of DNA hybridization is triggered and will result in the orientation transition of LC molecules (in the resonator core). According to the quadruple amplification from the disturbance of AuNPs, the excess polarizability of adhering biomolecules, the orientation variation of LC molecules, and the WGM resonance, the spectral wavelength shift can be employed as the sensing parameter to indicate the information of biotarget. L-histidine molecules are applied as the analyte. An ultra-low detection limit at a sub-femtomole level (~ 5 × 10−16 M) has been achieved using this highly-selective biosensor, which is eight orders of magnitude lower compared to the reported LC-based L-histidine sensor. In addition to L-histidine, this proposed optofluidic scheme with LC-AuNP hybrid amplification can also extend the applicability of DNAzyme-based biosensors for the detection of various molecules.

Chiral nematic liquid crystal droplets as a basis for sensor systems.

For a series of phospholipid coated calamitic nematic liquid crystal droplets (5CB, 6CB, 7CB, E7 and MLC7023) of diameter ∼18 μm, the addition of chiral dopant leaves the sign of surface anchoring unchanged. Herein we report that for these chiral nematic droplets an analyte induced transition from a Frank-Pryce structure (with planar anchoring) to a nested-cup structure (with perpendicular anchoring) is accompanied by changes in the intensity of reflected light. We propose this system as both a general scheme for understanding director fields in chiral nematic liquid crystal droplets with perpendicular anchoring and as an ideal candidate to be utilised as the basis for developing cheap, single use LC-based sensor devices.

A cationic surfactant-decorated liquid crystal-based sensor for sensitive detection of quinoline yellow

Quinoline yellow (QY) is one of the popular synthetic food colorants and in food industry greatly used. Developing accurate and simple QY detection procedures is of major considerable importance in ensuring food safety. Hence, it is important to detect this food colorant effectively to reduce risk. Herein, an innovative liquid crystal (LC)-based sensor was designed for the label-free and ultra-sensitive detecting of the QY by means of a cationic surfactant-decorated LC interface. The nematic liquid crystal in touch with CTAB revealed a homeotropic alignment, when QY was injected into the LC-cell, the homeotropic alignment consequently altered to a planar one by electrostatic interactions between QY and CTAB. The designed LC-based sensor detected QY at the too much trace level as low as 0.5 fM with analogous selectivity. The suggested LC-based sensor is a rapid, convenient and simple procedure for label-free detection of QY in food industrial and safety control application.

Liquid crystal-based aptasensor to detect ractopamine hydrochloride at a femtomolar level

We developed a liquid crystal (LC)-based aptasensor to detect ractopamine hydrochloride (RAC) at the femtomolar level by analyzing the optical texture of LCs. The LC-based sensor comprises an aptamer that reacts with cetrimonium bromide (CTAB) and RAC at the interface between the aqueous phase and the LCs. The self-assembled CTAB causes the LCs to anchor perpendicularly at the aqueous/LC interface. The ordering of the LCs at the interface between the CTAB-packed aqueous phase and LCs depends on the concentration of RAC. When the specific binding events between the aptamers and RAC were superior to the electrostatic interactions of the aptamers with CTAB, the ordering of the LCs remained in the homeotropic orientation. When the electrostatic interaction became relatively dominant, it perturbed the orientation of the LCs, changing their anchoring from homeotropic to tilted or planar. We monitored the optical response of the LCs, which depends on their ordering transitions. RAC levels as low as approximately 0.697 fg/mL (2.323fM) in phosphate-buffered saline and 0.840 pg/mL (2.813 pM) in pig urine could be detected using this aptasensor. The change in the optical texture of the LCs was quantitatively interpreted by comparing the averaged grayscale intensity data of the LC optical images. Our results indicate that this LC-based aptasensor has highly sensitivity and selectivity and can be reused.

A wireless passive pressure sensor using microstructured ferromagnetic films with tunable effective permeability

This paper presents a novel LC-based passive wireless flexible pressure sensor that employs microstructured ferromagnetic films with tunable effective permeability. The proposed device consists of a micromachined planar spiral coil and a polymer film with cilia arrays (CAs) realized by the ferrofluidic instability principle. The effective permeability of the polymer film can be tuned by deforming the CAs with externally applied pressure, which can be estimated in turn by detecting the resonant frequency of the device using the phase-dip technique. The fabrication parameters for synthesizing different dimensions and densities of CAs were investigated as well. Devices of different CA densities were measured and discussed. The measured results showed that the device quality factor and phase change both increased with applied pressure. Due to this characteristic, the proposed device is advantageous over typical capacitive LC-based devices and performs better in wireless interrogation while maintaining the sensitivity of pressure sensing.

Research on Competitive Enzymatic Hydrolysis-Assisted Liquid Crystal-based Acetylcholine Sensor

1. 报道了一种基于液晶的简单、低成本、无标记的检测乙酰胆碱的方法。 2. 氯化十四酰胆碱与乙酰胆碱发生竞争性的酶解反应，引起液晶分子在界面上的排列方式及液晶的光学形貌发生了改变。 3. 乙酰胆碱的检测限低至14.5 nmol/L。 4. 基于液晶实现了对乙酰胆碱高灵敏度、高特异性的检测。 A simple, convenient and label-free approach was developed for detection of acetylcholine (ACh) based on competitive enzymatic hydrolysis by use of liquid crystals (LCs) as a sensing medium. Self-assembled monolayers of myristoylcholine (Myr) were obtained at the aqueous/LC interface when the surfactants were in contact with LCs, resulting in a perpendicular orientation of LCs at the interface. Thus, LCs displayed a dark optical image. However, enzymatic hydrolysis of Myr by acetylcholinesterase (AChE) disturbed the Myr monolayers, which led to a horizontal orientation of LCs at the interface, thereby inducing a dark-to-bright shift of the LCs optical appearance. Interestingly, as ACh was also a substrate of AChE, the bright appearance of LCs was prevented when incubating the mixture of AChE and ACh with Myr decorated aqueous/LC interface due to the competitive enzymatic hydrolysis between Myr and ACh by AChE. By using this strategy, ACh could be detected selectively and sensitively, with a broad linear range from 0.01 μmol/L to 1 mmol/L and a low detection limit of 14.5 nmol/L. The results showed that the competitive enzymatic hydrolysis-assisted LC-based sensor had potential applications in ACh detection. A simple, low-cost and label-free assay was reported for detection of acetylcholine (ACh) based on liquid crystals (LCs). Variations in the arrangement and optical appearance of LCs are due to the competitive enzymatic hydrolysis between myristoylcholine (Myr) and ACh by acetylcholinesterase (AChE). By using this strategy, highly sensitive and highly specific detection of ACh is achieved.

An acetylcholinesterase-based biosensor for the detection of pesticides using liquid crystals confined in microcapillaries

Here, we demonstrate a capillary-sensing platform based on liquid crystals (LCs) confined in microcapillaries for simple and sensitive detection of acetylcholinesterase (AChE) and its inhibitors. LC droplets were formed through sequential injection of LCs and an aqueous solution into trichloro(octyl)silane (OTS)-treated microcapillaries. When the confined LC droplets make contact with a cationic surfactant solution, myristoylcholine chloride (Myr), the formation of a Myr monolayer at the aqueous/LC interface induces a horizontal orientation of the LCs at the interface along the microcapillary, producing an optical LC droplet texture of a four-petal shape. On the other hand, AChE can catalyze the hydrolysis of Myr into choline and myristic acid. The hydrolyzed Myr is unable to form a monolayer at the aqueous/LC interface, and therefore the confined LC droplets exhibit two bright-lined optical images when in contact with the pre-incubated mixture of Myr and AChE, corresponding to the homeotropic orientation of LCs at the interface. However, in the presence of AChE-inhibiting pesticides, such as fenobucarb and malathion, the activity of AChE is inhibited, and thus, the enzymatic hydrolysis of Myr cannot occur. As a result, the confined LC droplets present the four petal-shaped optical images when in contact with the pre-incubated mixture of Myr, AChE, and pesticides. Based on this principle, an LC-based microcapillary sensor was developed and utilized for the detection of pesticides. Using this sensing platform, fenobucarb and malathion were detected at limits of 5 pg/mL and 2.5 pg/mL, respectively. Moreover, the proposed biosensor was successfully applied to the determination of pesticides in real river water. Therefore, this LC-based microcapillary sensor is a promising platform for simple, rapid, and label-free detection of pesticides with very high sensitivity.

Simple, sensitive technique for α-amylase detection facilitated by liquid crystal-based microcapillary sensors

Here, we describe a novel sensor that uses microcapillary-confined liquid crystals (LC) and a host-guest inclusion complex, β-cyclodextrin/sodium dodecyl sulfate (β-CD/SDS), to detect α-amylase. All LC droplets confined within the microcapillaries were planar-oriented at the LC-aqueous interface where they came into contact with the non-surfactant solution. In contrast, when the LC droplets come into contact with a surfactant solution (SDS aqueous solution), the surfactant molecules anchor the LC droplets and induce a homeotropic orientation. The degradation of β-CD in the host-guest inclusion complex by α-amylase releases free SDS molecules and facilitates a change in LC orientation, from planar to homeotropic, which corresponds with the development of two bright lines and four petal-shaped optical images. This LC-based microcapillary sensor has a limit of detection (LOD) of 100 ng/mL for α-amylase in aqueous solutions and 500 ng/mL in urine samples. Our sensor exhibits good specificity, sensitivity, and long-term stability for α-amylase, and it provides an uncomplicated, cost-competitive, and non-labeled technique for the detection of α-amylase in both aqueous solutions and human urine samples. Furthermore, the results show an effective detection of α-amylase in human urine samples, demonstrating the feasibility of this sensor in practical applications.

Liquid crystal-based optical sensor for the detection of cysteine through competitive host-guest inclusion

ABSTRACT A β-cyclodextrin (β-CD) inclusion complex containing L-cysteine (CYS) as a guest was prepared by freeze drying method. Formation of the inclusion complex was confirmed by powder X-ray diffraction pattern, Fourier-transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy. The interaction between CYS and β-CD was also analysed by conductivity measurement in aqueous solution. Thereafter, we developed a liquid crystal (LC)-based sensor system to detect CYS in aqueous solution following the principle of competitive host–guest inclusion. Here the guests sodium dodecyl sulphate (SDS) and CYS compete for the same hydrophobic cavity of host β-CD. The dark optical image observed by polarising optical microscope confirms that CYS forms inclusion complex with β-CD leaving SDS free which aligns LCs homeotropically. The constructed LC-based sensor could detect CYS up to 30 µM in aqueous solution. Moreover the practical approach of this system was validated by sensing CYS in human serum.

Liquid-crystal-droplet-based Monitoring System for Water-soluble Inorganic Acidic Gases from the Atmosphere

A liquid crystal (LC)-based pH sensor for real-time monitoring of variations in localized pH values near the LC droplets was developed, and its applicability for the detection of acidic gases was explored. It was found that 4-cyano-4′-pentylbiphenyl (5CB), when doped with hexanoic acid (HA), shows a bright-fan-shaped (planar orientation of LCs) to dark-cross (homeotropic orientation of LCs) optical response to a minimal change of the pH value (from 6.5 to 6.6). The fast and intensive pH-driven optical response can be explained mainly with the orientational transitions of 5CB, induced by the protonation and deprotonation of HA at the interface of aqueous/LC droplet. Because of its high pH sensitivity, the LC-based sensor was further exploited for monitoring the local pH changes, which were originated from concentration changes of acidic gases. The results suggested that at an industrial scale/production environment, the sensor shows excellent performance for long-term monitoring and sensing of acidic gases. This type of LC-based sensor may find to fulfill its applicability potential in the trace measurement of acidic gases.

Liquid crystal-based sensor system for detecting formaldehyde in aqueous solutions

We developed a liquid crystal (LC)-based sensor system for detecting formaldehyde in aqueous solutions. In this system, nematic LCs were doped with 4′-pentyl-4-biphenylamine (PBA), which acts as the amphiphilic molecule to align at LC/aqueous interface. Such alignment induced the homeotropic orientation of LCs and a dark signal was observed under polarized light. Formaldehyde in the aqueous solutions would react with the amine group of PBA to form corresponding imine, which reduced the amount the PBA at LC/aqueous interface. As a result, the orientation of LCs was disrupted and a dark-to-bright transition of the LC images was observed. By using this mechanism, 0.5 mM of formaldehyde can be detected in 10 min with good selectivity. Moreover, we demonstrated that this system can be applied to detect formaldehyde in commercial facial toners with the limit of detection (LOD) of 30 mM, which is below the safety level of cosmetic products regulated by USA and the European Union. Because the LC-based sensor system is cost-effective and easy to use, while its signals can be simply differentiated through the naked-eye under ambient light, it shows great potential for the applications of formaldehyde detection in the daily necessities for general family.

Liquid crystal-based capillary sensory platform for the detection of bile acids

Bile acids directly related to liver and intestinal function are used as indicators of hepatobiliary and intestinal diseases. Here, we have designed and realized a capillary sensory platform for the detection of bile acids using liquid crystals (LCs). LC droplets confined in micro-capillaries are homeotropically aligned at the surfactant-packed LC/aqueous interface. However, the competitive adsorption of bile acids disrupts the surfactant packing at this interface and triggers the orientational transition of the LC droplets from homeotropic to planar at the interface, followed by changes in optical images captured by polarized light microscopy. With this sensing system, we could successfully detect three main types of bile acids and further examine the effects of the pH of the solution and chain-length of the surfactant molecules on the detection of bile acids. Interference experiment with ascorbic acid confirms the feasibility of this bile acids detection approach. Our research suggests that this LC-based capillary sensor is a sensitive, simple, and potential tool for the detection of bile acids without the need for complicated processes and expensive equipment.