Paper-based Analytical Devices Research Articles

Microfluidic paper-based analytical device for simultaneous determination of calcium and magnesium ions in human serum

BackgroundCalcium and magnesium ions are highly abundant and important cations in human body. At the same time, both dyscalcemia and dysmagnesemia are frequently encountered in the clinical practice. As deficiency or excess of Ca(II) or Mg(II) can cause severe symptoms, determining these ions in serum is of great importance. Concentration of these ions in biological samples is typically assayed in clinical laboratories with the use of expensive and specialized equipment. Since those methods cannot be easily adapted for self-diagnosis purposes, there is a great need to develop a convenient tool for reliable determination of calcium and magnesium in serum at the point-of-care. ResultsThe colorimetric methods employed for calcium and magnesium analysis were o-cresophtalein complexone assay and xylidyl blue assay, respectively. Analytical signal acquisition was accomplished using an ordinary flatbed scanner or smartphone and free software. For increased user-friendliness the device was optimized to perform simultaneous determination of calcium and magnesium ions in only 10 min. In the optimized conditions, the limit of detection for calcium ions was 0.09 mmol L−1, while for magnesium it was 0.04 mmol L−1. Determination of both ions requires only 4 μL of serum sample. The developed paper-based sensors were validated with control human serum samples and the obtained relative errors for majority of samples were below 20 %. SignificanceIn this paper, a microfluidic paper-based analytical device for simultaneous determination of calcium and magnesium ions in human serum is reported for the first time. Additionally, this is also the first report on colorimetric determination in serum of any of these ions in paper-based format. Simultaneous detection of both ions allows for fast and user-friendly screening of disturbance in calcium and magnesium homeostasis.

CRISPR/Cas14 and G-Quadruplex DNAzyme-Driven Biosensor for Paper-Based Colorimetric Detection of African Swine Fever Virus.

The highly contagious nature and 100% fatality rate contribute to the ongoing and expanding impact of the African swine fever virus (ASFV), causing significant economic losses worldwide. Herein, we developed a cascaded colorimetric detection using the combination of a CRISPR/Cas14a system, G-quadruplex DNAzyme, and microfluidic paper-based analytical device. This CRISPR/Cas14a-G4 biosensor could detect ASFV as low as 5 copies/μL and differentiate the wild-type and mutated ASFV DNA with 2-nt difference. Moreover, this approach was employed to detect ASFV in porcine plasma. A broad linear detection range was observed, and the limit of detection in spiked porcine plasma was calculated to be as low as 42-85 copies/μL. Our results indicate that the developed paper platform exhibits the advantages of high sensitivity, excellent specificity, and low cost, making it promising for clinical applications in the field of DNA disease detection and suitable for popularization in low-resourced areas.

High-Throughput μPAD with Cascade Signal Amplification through Dual Enzymes for arsM in Paddy Soil.

The arsM gene is a critical biomarker for the potential risk of arsenic exposure in paddy soil. However, on-site screening of arsM is limited by the lack of high-throughput point-of-use (POU) methods. Here, a multiplex CRISPR/Cas12a microfluidic paper-based analytical device (μPAD) was constructed for the high-throughput POU analysis of arsM, with cascade amplification driven by coupling crRNA-enhanced Cas12a and horseradish peroxidase (HRP)-modified probes. First, seven crRNAs were designed to recognize arsM, and their LODs and background signal intensities were evaluated. Next, a step-by-step iterative approach was utilized to develop and optimize coupling systems, which improved the sensitivity 32 times and eliminated background signal interference. Then, ssDNA reporters modified with HRP were introduced to further lower the LOD to 16 fM, and the assay results were visible to the naked eye. A multiplex channel microfluidic paper-based chip was developed for the reaction integration and simultaneous detection of 32 samples and generated a recovery rate between 87.70 and 114.05%, simplifying the pretreatment procedures and achieving high-throughput POU analysis. Finally, arsM in Wanshan paddy soil was screened on site, and the arsM abundance ranged from 1.05 × 106 to 6.49 × 107 copies/g; this result was not affected by the environmental indicators detected in the study. Thus, a coupling crRNA-based cascade amplification method for analyzing arsM was constructed, and a microfluidic device was developed that contains many more channels than previous paper chips, greatly improving the analytical performance in paddy soil samples and providing a promising tool for the on-site screening of arsM at large scales.

A digital bar pH indicator based on a microfluidic paper-based analytical device

A pH value of an aqueous medium is an essential parameter in the environment and biology. Nowadays, it is possible to measure using a colorimetric pH paper or an electrochemical pH meter. However, since the two methods have drawbacks of the limited precision in pH determination and the careful management of a glass membrane electrode, respectively, it still remains as a challenge to discover a user-friendly, reliable pH-measuring device. Herein, a novel digital bar pH indicator was developed using a microfluidic paper-based analytical device (μPAD) to determine with the naked eye the pH value of an aqueous sample. The fabricated digital indicator consists of seven independent pH sensors displaying a color change from yellow to greenish blue above specific pH values. These sensing elements were vertically aligned to form a bar shape, and their color-changing pH points were regulated to increase upward from 4.5 to 7.5 with an interval of 0.5 units. For fast and simultaneous detection of the colorimetric sensors, sample addition to an inlet of the μPAD was quickly transported vertically along a hollow paper channel, horizontally divided, and arrived at the detection zones at similar times via delay channels. Through independent experiments, control of the color-changing pH point and flow rate were confirmed by addition of a surfactant additive into the pH indicator and inserting empty spaces in a flow channel, respectively. Reliable operation of the fabricated μPAD was verified using standard pH buffer samples. Finally, the feasibility of our digital bar pH indicator was successfully demonstrated for determining the pH value of a urine sample under the resolution of 0.5 units.

Two-dimensional metal-organic framework nanozyme-mediated portable paper-based analytical device for dichlorophen assay

The metal-organic frameworks (MOFs) nanozyme-mediated paper-based analytical devices (PADs) have shown great potential in portable visual determination of phenolic compounds in the environment. However, most MOF nanozymes suffer from poor dispersibility and block-like structure, which often prompts deposition and results in diminished enzymatic activity, severely hindering their environmental applications. Here, we proposed colorimetric PADs for the visual detection of dichlorophen (Dcp) based on its significant inhibitory effect on the two-dimensional (2D) MOF nanozyme activity. Specifically, we synthesized a 2D Cu TCPP (Fe) (defined as 2D-CTF) MOF nanozyme exhibiting excellent dispersibility and remarkable peroxidase-like (POD-like) activity, which could catalyze the oxidation and subsequent color change of 3,3′,5,5′-tetramethylbenzidine even under neutral conditions. Notably, the POD-like activity of 2D-CTF demonstrated a unique response to Dcp because of the occupation of Fe–N4 active sites on the 2D-CTF. This property enables the use of 2D-CTF as a highly efficient catalyst to develop colorimetric PADs for naked-eye and portable detection of Dcp. We believe that the proposed colorimetric PADs offer an efficient method for Dcp assay and open fresh avenues for the advancement of colorimetric sensors for analyzing of phenolic toxic substances in real samples.

Superhydrophobic eggshell for fabrication of hydrophobic barrier of paper-based analytical device for colorimetric determination of ammonium ion in water

This work demonstrates the first application of the superhydrophobic eggshell as an environmental-friendly material for fabricating the hydrophobic barrier of a paper-based analytical device (PAD). The eggshell surface was modified by mixing the pulverized chicken eggshell biowaste with stearic acid and a polystyrene binder to accomplish superhydrophobicity. The PAD (10 × 10 mm2) is comprised of the circular-shaped hydrophilic reservoir (Ø 5 mm). The liquid barrier was fabricated by painting both the topside and the underside of the filter paper with the dispersed superhydrophobic eggshell solution. The SEM images revealed that the microsized superhydrophobic eggshell particles absorbed onto the porous surface of the cellulose fibril. A coated surface with a water contact angle of 155.39° ± 1.02° (n = 10) on the paper substrate was achieved, and this indicated superhydrophobicity. The eggshell barrier enabled excellent water and chemical resistance. The fabricated PAD was applied for the colorimetric determination of ammonium cations (NH4+), based on the modified Berthelot reaction. Samples and chromogenic solutions were aliquoted onto the hydrophilic reservoir, with subsequent capture of the optical image of the stable, green-colored product by a smart phone under a light-controlled studio. The green color intensities were evaluated by ImageJ™ and plotted against the standard NH4+ concentrations. A wide linear calibration range 5.0 to 100 mg N/L was achieved with good linearity (r2 > 0.99). The PAD confirmed satisfied analytical recovery (Mean ± SD: 100.6 % ± 0.97, n = 11 samples) and high precision (RSD = 0.85 %: 10-PAD replicate measurements of 1.0 mg N/L). The limit of detection (3 SD of blank/slope) of 1.05 mg N/L was found sensitive enough to monitor the NH4+ contents in freshwater. The results, determined by the developed PAD and ion chromatography, showed no significant difference under the statistical paired t-test at 95 % confidence (tstat = -1.80, tcri = 2.57, n = 6 samples).

Digitally Controlled Printing of Bioink Barriers for Paper-Based Analytical Devices: An Environmentally Friendly One-Step Approach.

The patterning of hydrophilic paper with hydrophobic materials has emerged as an interesting method for the fabrication of paper-based devices (PADs). Herein, we demonstrate a digitally automated, easy, low-cost, eco-friendly, and readily available method to create highly hydrophobic barriers on paper that can be promptly employed with PADs by simply using a bioink made with rosin, a commercially available natural resin obtained from conifer trees. The bioink can be easily delivered with the use of a ballpoint pen to produce water- and organic solvent-resistant barriers, showing superior properties when compared to other methods such as wax-printing or permanent markers. The approach enables the pen to be attached to a commercially available cutting printer to perform the semiautomated fabrication of hydrophobic barriers for PADs. With the aid of digitally controlled optimization, together with features of machine learning and design of experiments, we show a thorough investigation on the barrier strength that can be further adjusted to the desired application's needs. Then, we explored the barrier sturdiness across various uses, such as wide range aqueous pH sensing and the harsh acidic/organic conditions needed for the colorimetric detection of cholecalciferol.

Fabrication of flexible paper-based conducting molecularly imprinted polymer as analytical devices: Electrochemically assisted solid phase microextraction and selective flexible sensor for determination of naproxen

An electrochemical method is presented for the preparation of paper-based conductive molecular imprinted polymer (CMIP) film as a recognition element of a sensor and a selective absorber in separation methods. The paper became conductive by chemically incorporating polypyrrole (PPy) doped with anion dopant. The effects of the anion dopant and oxidant type on the conductivity of the modified paper were studied. Afterward, a CMIP film based on PPy and an anionic drug as a template was electrochemically synthesized on conductive paper surface, which was then utilized as a selective sorbent for electrochemically assisted solid phase microextraction (EC-SPME) and a recognition element in fabricating flexible drug-selective sensor. Factors affecting the performance of the paper-based EC-SPME device were studied in naproxen (NAP) analysis. All quantitative analytical parameters in the EC-SPME device were obtained by UV–vis absorption spectroscopy. Under the optimal conditions, linearity was achieved within the range of 2.0 × 10−7–2.0 × 10−5 mol/L with determination coefficient (R2 = 0.99) and the limit of detection (LOD) was 0.6 × 10−7mol/L. Moreover, a fabricated paper-based NAP-selective sensor, showed Nernstian response slopes of −61.6 ± 0.5 mV decade−1 over the linear range of 4.0 × 10−7–1.0 × 10−2 mol/L and LOD was 2.0 × 10−7 mol/L. The applicability and efficiency of the paper-based analytical devices were investigated for NAP determination as a model drug in human serum samples. The recoveries were obtained in the range of 90.0–103.0 %. Accordingly, paper-based CMIPs were found to be a novel fabrication method for efficient, selective, flexible and cost-effective material for analytical devices.

An enrichment system for glycoproteins using microfluidic paper-based analytical device with colorimetric detection

We introduce a facile method for glycoprotein enrichment, separation, and detection using microfluidic paper-based analytical devices (μPADs). The μPADs comprise two distinct components: the enrichment region (Chip I) and the detection section (Chip II). The reusable Chip I is fabricated by immobilizing 3-aminophenylboronic acid (APBA) onto a circular paper substrate, demonstrating exceptional glycoprotein affinity. In disposable Chip II, glycoproteins react with periodic acid, generating carbonyl compounds that produce a purple-colored product upon reacting with the Schiff reagent. Alterations in color intensity are captured using an ordinary cell phone and are subsequently analyzed using Photoshop software. Observations note a linear increase in average color intensities from 1.0 × 10−3 to 5.0 × 10−3 mol/L, with an R2 value of 0.9927. The relative standard deviations (RSDs) of inter-day (n = 5) and intra-day (n = 5) assessments stand at 1.5 % and 1.4 %, respectively. Our proposed approach can effectively enrich an ovalbumin (OVA) solution with concentrations as low as 1.0 × 10−11 mol/L, resulting in enrichment rates of 107 to 108 times. The interference deviations of five substances relative to OVA lie within the range of − 2.0 % to + 2.0 %. The methodology successfully enriches glycoproteins from egg white samples diluted by a factor of 1 × 106, demonstrating that the proposed method is remarkably suitable for enriching glycoproteins from authentic samples.

Current diagnostics and biomarkers for arboviral infections (a review on Dengue, Zika, West Nile and Chikungunya viruses)

Arboviral infections, transmitted to humans primarily through arthropod vectors, constitute a significant global health threat. Arboviruses, such as Dengue, Zika, Chikungunya, and West Nile viruses, continue to cause widespread outbreaks, necessitating advanced diagnostic tools. Emerging technologies including Lab On A Chip (LOC), Lab On A Disc (LOAD), Microfluidic Paper-Based Analytical Devices (µPADS), Lateral Flow Devices, CRISPR-CAS 12/13, Quartz crystal microbalance (QCM), and Nano-Technology are evaluated for their potential to enhance arboviral diagnosis, offering rapid, accurate, and point-of-care solutions. Furthermore, the identification of robust biomarkers, including Inflammatory Cytokines, Antibodies, Endothelial Activation Products and Indicators of Tissue or Organ Damage, is crucial for improving the understanding of disease pathogenesis, prognosis, and treatment response. A comprehensive analysis of potential diagnostics and biomarkers for arboviral infections sheds light on the evolving strategies to combat these medically significant diseases, ultimately contributing to more effective surveillance, diagnosis and management worldwide.

Smartphone-Based Colorimetric Microfluidic Paper-Based Analytical Device for On-Site Detection of Calcium Ions in Milk Samples

Milk is a major dietary source of calcium; thus, accurate and precise quantification of calcium in milk and other dairy products is necessary for quality control. Conventional instrumental methods are sensitive and accurate but require expensive instrumentation, sample pretreatment, skilled personnel, and a long detection time. Herein, a microfluidic paper-based analytical device (µPAD) was developed to quantify calcium ions (Ca2+) in milk using a smartphone as a detector. The method utilized a complexometric reaction between Ca2+ and ethylene diamine tetraacetic acid with murexide as an indicator. The response was the average color intensity at the detection zones measured using the Color Picker application. The proposed µPAD exhibited a good linear detection range (1 to 10 mM), a low detection limit of 0.42 mM, and a short analysis time of 2 min. The determination of Ca2+ in milk samples using the proposed µPAD was consistent with a potentiometric method. The proposed µPAD demonstrates many advantages, including rapid detection, acceptable accuracy, low cost, low sample volume, and suitability for on-site quantification of Ca2+ in real samples.

Wax screen-based fabrication of paper devices for the determination of iron in particulates of selected welding fumes in Addis Ababa, Ethiopia

In this study a paper-based analytical device was developed using screen printing technique for the determination of particulate iron from welding fumes. The operational parameters such as volume and concentration of 1,10-phenanthroline, volume and concentration of hydroxylamine were optimized by the Box Behnken Design (BBD) using Minitab. Additionally, the µ-PAD's sample solution holding capacity and reaction time were also optimized. Under the optimized condition, particulate metal concentrations were colorimetrically quantified usinga handheld mobile phone and image processing software, ImageJ. Very good analytical performance such as good linearity of the calibration curve and better selectivity was observed by the developed method. The limit of detection for Fe3+ assay was 4.6 mg/L; which is adequate to determine the threshold concentration limit of particulate iron set by the regulatory bodies (6 mg/L). The µ-PAD revealed 95-99% recovery compared with the UV-Vis spectrophotometry (98-100%). Furthermore, welding fume samples were collected in Addis Ababa over five days, using mixed cellulose ester filters and the findings show a high concentration that exceeds the standard levels. Analyzing particulate iron with µ-PADs yielded results consistent with UV-Vis spectrophotometry, suggesting µ-PADs' potential application for occupational particulate iron exposure measurement, eliminating the need for expensive analytical devices.
 KEY WORDS: µ-PADs, Particulate iron, Response surface methodology, Wax screen-printing, Welding fume, Colorimetric detection
 Bull. Chem. Soc. Ethiop. 2024, 38(3), 563-576. 
 DOI: https://dx.doi.org/10.4314/bcse.v38i3.2 

A smartphone-integrated aptasensor for pesticide detection using gold-decorated microparticles.

The increasing incidence of environmental concerns related to excessive use of pesticides, such as imidacloprid and carbendazim, poses risks to pollinators, water bodies, and human health, prompting regulatory scrutiny and bans in developed countries. In this study, we propose a portable smartphone-based biosensor for rapid and label-free colorimetric detection by using the gold-decorated polystyrene microparticles (Ps-AuNP) functionalized with specific aptamers to imidacloprid and carbendazim on amicrofluidic paper-based analytical device (μ-PAD). Four aptamers were selected for the detection of these pesticides and their sensitivity and selectivity performancewas evaluated. The sensitivity results show a detection limit for imidacloprid of 3.12ppm and 1.56ppm for carbendazim. The aptamers also exhibited high selectivity performance against other pesticides, such as thiamethoxam, fenamiphos, isoproturon, and atrazine. However, the platform presented cross-selectivity when detecting imidacloprid, carbendazim, and linuron, which is discussed herein. Overall, we present a promising platform for simple, on-site, and rapid colorimetric screening of specific pesticides, while highlighting the challenges of aptasensors in achieving selectivity amidst diverse molecular structures.

Integrating Paper-Based Microfluidics and Lateral Flow Strip into Nucleic Acid Amplification Device toward Rapid, Low-Cost, and Visual Diagnosis of Multiple Mycobacteria.

Efficient diagnosis of mycobacterial infections can effectively manage and prevent the transmission of infectiousdiseases. Unfortunately, existing diagnostic strategies are challenged by long assay times, high costs, and highly specialized expertise to distinguish between pulmonary tuberculosis (PTB) and nontuberculous mycobacterial pulmonary diseases (NTM-PDs). Herein, in this study, an optimized 3D paper-based analytical device (µPAD) is incorporated with a closed lateral flow (LF) strip into a loop-mediated isothermal amplification (LAMP)device (3D-µPAD-LF-LAMP) for rapid, low-cost, and visual detection of pathogenic mycobacteria. The platform's microfluidic featureenhanced the nucleic acid amplification, thereby reducing the costs and time as compared to boiling, easyMAG, and QIAGEN techniques. Moreover, the LF unitis specifically designed to minimize aerosol contamination for a user-friendly and visual readout. 3D-µPAD-LF-LAMP is optimized and assessed using standard strains, demonstrating a limit of detection (LOD) down to 10 fgreaction-1 . In a cohort of 815 patients, 3D-µPAD-LF-LAMP displays significantly better sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and diagnostic accuracy than conventional bacterial culture and Xpert techniques. Collectively, 3D-µPAD-LF-LAMP demonstrates enhanced accessibility, efficiency, and practicality for the diagnosis of multiple pathogenic mycobacteria, which can be applied across diverse clinical settings, thereby ultimately improving public health outcomes.

An electrochemical paper-based analytical device with facile carbon fiber-sewed electrodes for highly sensitive detection of hydrogen peroxide in real water

A novel and facile method by sewing low-cost fiber electrodes on paper is proposed to fabricate electrochemical paper-based analytical devices (ePADs). Prussian Blue (PB) and Ag/AgCl were deposited on carbon fibers to prepare the working and reference electrodes. The hydrophilic carbon fiber was employed as the counter electrode. All electrodes were sewed on the paper substrate. The linear voltammetry scanning (LSV) and physical characterization results showed that the physico-chemical characteristics of the prepared electrode were maintained after sewing. As a proof of concept, the ePAD fabricating by sewing was used to detect hydrogen peroxide (H2O2). The limit of detection (LOD) achieved 0.9 µM and the ePAD possessed high anti-interference ability to a variety of common ions and biological molecules. Additionally, the robustness of the ePADs against bending (error 6.2 %) manifested that the ePAD had excellent practical applicability. The good reproducibility (3.65 %) displayed by the current responses confirmed that this strategy can be profitably adopted to easily assemble ePADs in a highly flexible manner. In addition, a user-friendly reagent-free ePAD was proposed to determine the content of H2O2 in real water sample without treatment. The good recovery percentage (95.7–99.7 %) demonstrated the high feasibility of the reagent-free ePAD with facile carbon fiber-sewed electrodes in the detection of H2O2 from complex water samples. These results confirm that the sewing method is feasible and promising. This work provides a new insight into fabrication of highly sensitive and highly selective ePADs with fiber electrodes.

Hydrophobic barrier-free laminated paper-based analytical device (LPAD) using a diameter-based measurement for determination of iodide in pharmaceutical products

This work presents, for the first time, an exploitation of an argentometric Mohr's method for iodide detection using diameter-based measurement on laminated paper-based analytical device (LPAD). Our LPAD is simplified fabricated with no required hydrophobic barrier for patterning a detection flow channel. In the absence of a flow channel, the liquid is imbibed radially into the filter paper outward from the small center inlet hole. This imbibition leads to the measurement of diameter after the formation of the precipitation product. For LPAD, a rectangular piece of Whatman filter paper is cut and positioned between a top laminating sheet, which has a hole punched for inlet, and a bottom laminating sheet. The central inlet hole enables access to the liquid on the paper. For iodide analysis, silver nitrate is dispensed first, followed by the iodide standard/sample. This process leads to the formation of pale-yellow silver iodide solids on the paper. The chromate indicator solution is subsequently loaded to the paper. The color of the chromate solution imparts a tint to the circular band of silver iodide solids, resulting in an intense yellow color. When the silver iodide precipitates are stained, the chromate solution typically serves as an indicator, chemically reacting to an excess silver nitrate solution moistened on paper. This reaction generates an outer reddish-brown ring of silver chromate. The distinct color contrast between the intense yellow (tinted silver iodide) and reddish-brown (silver chromate) allows for clear observation of the measurement boundary, facilitating diameter-based measurements of the circular band of silver iodide. We demonstrate the applicability in analysis of pharmaceutical KI tablets. The quantitative results obtained from diameter-based measurement LPAD show good agreement with those obtained from the potentiometric method. Our hydrophobic barrier-free LPAD is rapid, cost-effective, low liquid consumption and applicable for onsite analysis.

A novel premixing strategy for highly sensitive detection of nitrite on paper-based analytical devices

BackgroundNitrite has been involved in many food processing techniques and its excessive consumption is closely related to the development of different diseases. Therefore, highly sensitive detection of nitrite is significant to ensure food safety. ResultThis study presents a simple and novel strategy for the highly sensitive detection of nitrite in food using paper-based analytical devices (PADs). In this proposed strategy, the nitrite present in the sample undergoes efficient diazotization when initially mixed with sulfanilamide solution before reacting with N-(1-naphthyl) ethylenediamine dihydrochloride (NED) coated on the detection region of the PAD, leading to the maximum production of colored azo compounds. Specifically, within the concentration range of 0.1–20 mg/L, the LOD and LOQ for the nitrite assay using the premixing strategy are determined as 0.053 mg/L and 0.18 mg/L, respectively which significantly surpass the corresponding values of 0.18 mg/L (LOD) and 0.61 mg/L (LOQ) achieved with the regular Griess reagent analysis. SignificanceThe study highlights the critical importance of the premixing strategy in nitrite detection. Under optimized conditions, the strategy demonstrates an excellent limit of detection (LOD) and limit of quantification (LOQ) for nitrite detection in eight different meat samples. In addition to its high precision, the strategy is applicable in the field of nitrite analysis. This strategy could facilitate rapid and cost-effective nitrite analysis in real food samples, ensuring food safety and quality analysis.

Paper based molecularly imprinted SERS substrate for early detection of lysophosphatidic acid in ovarian cancer

The current study is related to fabrication of point-of-care molecularly imprinted paper-based analytical devices, specifically related to ovarian cancer early stage detection. The task involves creating a paper coated with silver nanoparticles (AgNPs) that can be used as a transducer via surface enhanced Raman spectroscopy (SERS) to detect the threshold level of the biomarker lysophosphatidic acid (LPA) as a template molecule to diagnose ovarian cancer. MIPs are synthetic receptors designed for a targeted molecule which are prepared from polymers in the presence of target such as small molecules, proteins or cells etc. Removal of the template results in cavities which are structurally and electrostatically complementary to the template molecule. The molecularly imprinted polymer (MIP) layer was anchored on vinyl trimethoxy silane modified-paper, which served as a detector by hydrolytically modifying the paper surface with vinyl trimethoxy silane. To detect LPA in serum samples for ovarian cancer, MIP-paper based on SERS was developed. Patients with benign ovarian tumors had an LPA level of 7.73 μM whereas those with ovarian cancer have a level of 16.99 μM. A healthy person's LPA level is 2.92 μM. Consequently, the rise in LPA levels may aid in the early detection of ovarian cancer. The study refers to the use of a point of care device to diagnose ovarian cancer early, which should be simple, effective, and cost-effective. The analytical tool in the study is a sensor with high selectivity and sensitivity, quick assay times, and inexpensive costs. For LPA in serum, the binding constant of modified paper-based MIP ranges from 11.00 μM to 0.08 μM. The amalgamation of nanoparticles on 2D-paper with MIP have lead to develop sensor which can effectively select LPA in untreated real samples like serum.

Aptasensor Integrated with Two-Dimensional Nanomaterial for Selective and Sensitive Electrochemical Detection of Ketamine Drug.

Ketamine is one of the most commonly abused drugs globally, posing a severe risk to social stability and human health, not only it is being used for recreational purposes, but this tasteless, odourless, and colourless drug also facilitates sexual assaults when it is mixed with drinks. Ketamine abuse is a threat for safety, and this misuse is one of the main uses of the drug. The crucial role of ketamine detection is evident in its contributions to forensic investigations, law enforcement, drug control, workplace integrity, and public health. Electrochemical sensors have gained considerable interest among researchers due to their various advantages, such as low cost and specificity, and particularly screen-printed paper-based electrode (SPBE) biosensors have gained attention. Here, we reported an ePAD (electrochemical paper-based analytical device) for detecting the recreational drug ketamine. The advantages of using a paper-based electrode are that it reduces the electrode's production costs and is disposable and environmentally friendly. At the same time, nanographite sheets (NGSs) assisted in amplifying the signals generated in the cyclic voltammetry system when ketamine was present. This ePAD was developed by immobilizing a ketamine aptamer on NGS electrodes. The characterization of proper synthesized NGSs was performed by Scanning Electron Microscopy (SEM), XRD (X-ray Diffraction), Fourier-transform infrared spectroscopy (FTIR), and UV-Vis spectroscopy. Electrochemical techniques, including cyclic voltammetry (CV) and linear sweep voltammetry (LSV), were employed to validate the results and confirm each attachment. Furthermore, the versatility of the proposed sensor was explored in both alcoholic and non-alcoholic beverages. The developed sensor showed a low LOD of about 0.01 μg/mL, and the linear range was between 0.01 and 5 μg/mL. This approach offers a valid diagnostic technique for onsite service with minimal resources. This cost effective and portable platform offers desirable characteristics like sensitivity and selectivity and can also be used for POC (point of care) testing to help in the quick identification of suspicious samples and for testing at trafficking sites, amusement parks, and by the side of the road.

Determination of Quercetin in Iraqi Green Walnut Husk via Green Ionic Liquid-Based Digestion Extraction and Gel Filtration Procedures-Spectrophotometry and Microfluidic Paper-Based Analytical Platform Detection

This study was conducted to extract, isolate and quantify Quercetin from Iraqi green walnut husk (GWH) using a novel ionic liquid-based digestion extraction and gel filtration procedure coupled with visible spectrophotometry detection and compared with a novel microfluidic paper-based analytical device (µPADs) aiming for an economic, and green method. 1-butyl-3-methylimidazolium chloride (BMIMCl) aqueous solution was used as a green solvent alternative to conventional organic solvents due to their impressive solvation properties. The results showed that 100 mg of plant husk required 15 mL of BMIMCl solvent, and 30 minutes of digestion at 75° C, which involves a simpler, and greener extraction method compared with other extraction methods. Under optimal conditions, Quercetin was isolated using a gel filtration technique, and further investigations were conducted using high-performance liquid chromatography and Fourier-transmitted infrared to confirm the isolation of Quercetin. Aluminum chloride assay was selected to determine the concentration of Quercetin giving a linearity of 10-100 mg L-1 and correlation coefficient of 0.9369 and 0.7917 for spectrophotometric and µPADs methods, respectively. The antioxidant activity of isolated Quercetin showed good antioxidant activity and the ANOVA test was used to compare µPADs method with the spectrophotometric method and the results showed that there was no statistically significant difference between the two methods. In conclusion, BMIMCl solvent provides an excellent safe and suitable solvent for the extraction of phytochemicals from botanical drugs. In addition, the µPADs platform has been approved for its superiority against traditional methods for analytical purposes due to its green characteristic.