Paper-based Microfluidic Chip Research Articles

Development of a novel ternary MOF nanozyme-based smartphone-integrated colorimetric and microfluidic paper-based analytical device for trace glyphosate detection

Given the significant and potential fatal implications of glyphosate (GLY) residues on human health and the integrity of ecosystems, their presence has garnered substantial global concern and scrutiny. Herein, we introduced a pioneering colorimetric sensing platform, the first of its kind, based on ternary metal-organic frameworks (ZnCo-ZIFs@MIL-101(Fe)). This innovative platform enabled ultra-sensitive, affordable, portable and rapid on-site detection of GLY. This platform achieved a wider linear range for GLY of 0.02–40 μg/ml with an exhibiting remarkable detection limit of 1 ng/ml, which was attributed to the electronic hybridization of the Fe3+, Co2+, and Zn2+ metal centers of ZnCo-ZIFs@MIL-101(Fe), significantly enhancing the composite's catalytic performance. The assay was successfully employed to detect GLY in food and herb samples. Moreover, to meet the demand of in-field detection for GLY, a smartphone detection method based on ZnCo-ZIFs@MIL-101(Fe) with visual, intelligent, and portable features was fabricated. This detection concentration range of GLY was 0–1 μg/ml, and the limit of smartphone detection was 23 ng/ml. Furthermore, this sensor seamlessly integrated with smartphones and paper-based microfluidic chips (μPADs), which constructed a portable test strips-smartphone sensing platform for facilitating real-time and on-site visual quantitative detection of GLY. The detection concentration range was 0–1 μg/ml, and the limit was calculated as low as 75 ng/ml. The assay was highly adaptable in practical applications. In summary, our study paved a novel pathway for the design and utilization of multi-metal MOF nanozymes in on-site pesticide monitoring.

Paper-Based Microfluidic Device for Extracellular Lactate Detection.

Lactate is a critical regulatory factor secreted by tumors, influencing tumor development, metastasis, and clinical prognosis. Precise analysis of tumor-cell-secreted lactate is pivotal for early cancer diagnosis. This study describes a paper-based microfluidic chip to enable the detection of lactate levels secreted externally by living cells. Under optimized conditions, the lactate biosensor can complete the assay in less than 30 min. In addition, the platform can be used to distinguish lactate secretion levels in different cell lines and can be applied to the screening of antitumor drugs. Through enzymatic chemical conversion, this platform generates fluorescent signals, enabling qualitative assessment under a handheld UV lamp and quantitative analysis via grayscale intensity measurements using ImageJ (Ver. 1.50i) software. The paper-based platform presented in this study is rapid and highly sensitive and does not necessitate other costly and intricate instruments, thus making it applicable in resource-constrained areas and serving as a valuable tool for investigating cell lactate secretion and screening various anti-cancer drugs.

Rapid fabrication of modular 3D paper-based microfluidic chips using projection-based 3D printing

Rapid fabrication of modular 3D paper-based microfluidic chips using projection-based 3D printing

Rapid analysis of salbutamol residues in animal-derived food based on the fluorescence of MOFs/MIPs paper-based chips

Mimetic recognition materials for rapid and selective analysis of foodborne contamination from complex foodstuff becomes a hot research topic in the field of food safety. In this work, borate-affinity-functionalized MOF/molecularly imprinted polymer paper-based microfluidic chips (FSU-BA@MIP) were prepared by growing functionalized MOFs on paper surface with 3-carboxyphenylboronic acid (3-CPBA) as the ligands, followed by coating of a MIP layer of salbutamol (SAL) through a borate-affinity surface imprinting strategy. Using the obtained paper-based chip as a mimetic recognition and specific enrichment module, the fluorescence sensing platform achieved visual rapid quantitative analysis of SAL with a linear range of 0.1 × 10−2–5.0 mg L−1. The limits of detection and quantification were calculated to be 0.095 and 0.290 μg kg−1, respectively, and the sample loading via lateral flow aid could be completed within 30 min. The obtained MOFs/MIPs paper chips provide an effective way for the rapid analysis of harmful contaminants from different animal-derived foods.

Nanozyme-Catalyzed Colorimetric Detection of the Total Antioxidant Capacity in Body Fluids by Paper-Based Microfluidic Chips.

Total antioxidants play a crucial role in human health, and detection of the total antioxidant capacity (TAC) has broad application prospects in fields such as food safety, environmental assessment, and disease diagnosis. However, a long detection time, cumbersome steps, high cost, reliance on professional equipment, and nonportability still remain significant challenges. In this work, an efficient strategy of point-of-care testing (POCT) of the TAC in body fluids by nanozyme-catalyzed colorimetric paper-based microfluidic sensors is proposed. The paper-based microfluidic sensors coupled with a smartphone can reduce testing costs and provide portability. The nanozyme prepared by the solvothermal method presents Michaelis constants of 0.11 and 0.129 mM for H2O2 and TMB, respectively. A method for immobilizing nanozymes and chromogenic agents on a paper-based microfluidic chip is established. Based on smartphone photography and image grayscale extraction, the TAC can be qualitatively detected with a detection limit and linear range of 33.4 and 50-700 μM, respectively. Furthermore, the proposed sensor can realize the one-step quantitative analysis of the TAC in body fluids (blood, saliva, and sweat) within 15 min. The proposed nanozyme-catalyzed colorimetric paper-based microfluidic sensors presented in this study exhibit promising application prospects in the fields of biochemical analysis and POCT.

Simultaneous extraction of five heavy metal ions from root vegetables via dual-frequency ultrasound-assisted enzymatic digestion

The dual-frequency ultrasound-assisted enzymatic digestion (DUED) technique was developed for synchronous green extraction of five heavy metal ions in root vegetables. The combination of α-amylase, cellulase, and papain showed significant advantageous in extracting heavy metal ions. Under optimized dual-frequency ultrasonic conditions, the extraction rates of Cr, As, Cd, Pb, and Hg in carrots reached 99.04%, 105.88%, 104.65%, 104.10%, and 103.13% respectively. And the extraction process is highly efficient, completing in just 15 min. Compared to conventional microwave-assisted acid hydrolysis method, this technique eliminates the need for high-temperature concentrated acid, enhancing its environmental sustainability while maintaining mild reaction conditions, making it ideal for biosensors application. Additionally, simultaneous extraction and detection of four heavy metals in lotus roots were successfully achieved by using DUED and a fluorescent paper-based microfluidic chip. The obtained results are consistent with those obtained using conventional methods.

Paper-based microfluidic chips for wide time range fluid control based on knife crafting and laser cutting

In recent years, paper-based microfluidic chips have emerged as a promising microfluidic platform due to their simplicity, low cost, portability, and ease of fabrication. They have been applied in various fields such as biological analysis, environmental monitoring, and medical diagnostics. However, the current paper-based chips made of nitrocellulose membrane still can be improved in liquid flow rate control. To address these issues, a novel paper-based microfluidic chip is designed to control liquid in a wide time range, and the liquid delay and acceleration control are realized by laser cutting and knife crafting respectively. Microfluidic chip’s hydrophobic boundaries can be manufactured in a one-step process using laser cutting, taking less than 10 seconds. Additionally, the structural parameters of microgrooves, which have a significant impact on flow rate, can be precisely controlled using a scalpel-based cutting platform. This enables efficient and consistent microgroove processing. Furthermore, experimental optimization of laser cutting and knife crafting parameters is performed, along with an exploration of factors influencing the delay and acceleration effects in the chip structures. The effectiveness of these processing methods is validated through practical applications. In summary, this study realizes a wide time range fluid control in paper-based microfluidic chips, which can achieve delay and acceleration in the range of −55.6% to +828.3%, thus expanding the application range of paper-based microfluidic chips.

A pump-free paper/PDMS hybrid microfluidic chip for bacteria enrichment and fast detection

Developing portable and sensitive biosensors for bacteria detection is highly demanded due to their association with environmental and food safety. Paper-based microfluidic chip is the suitable candidate for constructing pump-free biosensor since paper is hydrophilic, low-cost and easy to use. However, the contradiction between sensitivity and small sample volume seriously affects the application of paper-based chip for bacteria detection. Here, a new microfluidic biosensor, combining large PDMS reservoir for sample storage, hydrophilic paper substrate for pump-free water transport, coated microspheres for bacteria capture and super absorbent resin for water absorption, is designed for the detection of bacteria in aqueous samples. Once the sample solution is introduced in the reservoir, water will automatically flow through the gaps between microspheres and the target bacteria will be captured by the aptamer coated on the surface. To facilitate PDMS reservoir bonding and ensure water transport, the upper side of paper substrate is coated with Polyethylenimine modified PDMS and the bottom side is kept unchanged. After all the solution is filtrated, fluorescent dye strained bacteria are enriched on the microspheres. The fluorescent intensity representing the number of bacteria captured is then measured using a portable instrument. Through the designed microfluidic biosensor, the bacteria detection can be achieved with 2 mL sample solution in less than 15 min for water or 20 min for diluted milk. A linear range from 10 CFU/mL to 1000 CFU/mL is obtained. The paper-based 3D biosensor has the merits of low-cost, simple operation, pump-free and high sensitivity and it can be applied to the simultaneous detection of multiple bacteria via integrating different aptamers.

Paper-based microfluidic chip for sweat volume, ECG and EMG monitoring

With the development of wearable devices, the application of non-invasive wearable devices to monitor sweat in real time is the most important for human health. Here, a paper-based microfluidic chip for monitoring of sweat loss during exercise is proposed. Highly absorbent rice paper is selected as the paper-based material, and the capillary action of the paper base is used to actively adsorb sweat, and it can be used repeatedly. As the electrode material, the conductive cloth has good tensile properties and bending resistance, which ensures that the change of resistance is caused by the amount of sweat entering. Other materials of the chip are highly hydrophobic, ensuring that all sweat will be absorbed by the paper base. The sweat volume monitored by the microfluidic chip in real time is 0.5μl-225μl. Compared with rigid electrodes and wet electrodes, the application of flexible electrodes allows the chip to fit well with the skin, the ECG waveform is clearer and has greater amplitude, and the EMG is smoother and has a greater signal-to-noise ratio.

Quantitative analysis for sweat-absorbing times of paper-based microfluidic chips

Quantitative analysis for sweat-absorbing times of paper-based microfluidic chips

Paper-Based Microfluidic Chips for Food Hazard Factor Detection: Fabrication, Modification, and Application.

Food safety and quality are paramount concerns for ensuring the preservation of human life and well-being. As the field of food processing continues to advance, there is a growing interest in the development of fast, instant, cost-effective, and convenient methods for detecting food safety issues. In this context, the utilization of paper-based microfluidic chips has emerged as a promising platform for enabling rapid detection, owing to their compact size, high throughput capabilities, affordability, and low resource consumption, among other advantages. To shed light on this topic, this review article focuses on the functionalization of paper-based microfluidic surfaces and provides an overview of the latest research and applications to colorimetric analysis, fluorescence analysis, surface-enhanced Raman spectroscopy, as well as their integration with paper-based microfluidic platforms for achieving swift and reliable food safety detection. Lastly, the article deliberates on the challenges these analytical methods and presents insights into their future development prospects in facilitating rapid food safety assessment.

Molecular imprinting-based indirect fluorescence detection strategy implemented on paper chip for non-fluorescent microcystin

Fluorescence analysis is a fast and sensitive method, and has great potential application in trace detection of environmental toxins. However, many important environmental toxins are non-fluorescent substances, and it is still a challenge to construct a fluorescence detection method for non-fluorescent substances. Here, by means of charge transfer effect and smart molecular imprinting technology, we report a sensitive indirect fluorescent sensing mechanism (IFSM) and microcystin (MC-RR) is selected as a model target. A molecular imprinted thin film is immobilized on the surface of zinc ferrite nanoparticles (ZnFe2O4 NPs) by using arginine, a dummy fragment of MC-RR. By implementation of IFSM on the paper-based microfluidic chip, a versatile platform for the quantitative assay of MC-RR is developed at trace level (the limit of detection of 0.43 μg/L and time of 20 min) in real water samples without any pretreatment. Importantly, the proposed IFSM can be easily modified and extended for the wide variety of species which lack direct interaction with the fluorescent substrate. This work offers the potential possibility to meet the requirements for the on-site analysis and may explore potential applications of molecularly imprinted fluorescent sensors.

Pb(II) inhibits CRISPR/Cas12a activation and application for paper-based microfluidic biosensor assisted by smartphone

A simple and low-cost paper-based microfluidic biosensor has been developed for on-site detection of Pb(II) by using CRISPR-Cas12a assisted smartphone device. Pb(II) induced G-quadruplex can inhibit the activation of the CRISPR-Cas12a system and subsequently prevent the cleavage of single-stranded DNA around gold nanoparticles. Thus, the resultant dispersed gold nanoparticles will flow into the detection zone and be subsequently captured by DNA nano-flowers in the detection zone of the paper-based microfluidic chip, resulting in the corresponding color change. The R/G values analyzed through our established SmartIons APP, correlate well with Pb(II) concentrations with a linear detection range of 0.1 μM - 10 μM and a lowest detection limit of 18.3 nM. The paper-based microfluidic biosensor exhibits high specificity, good anti-interference ability, stability and applicability. In view of low cost, easy customization and multiple channel, paper-based microfluidic biosensor has great potential for the on-site detection of Pb(II).

A novel colorimetric and fluorescent dual-mode 3D paper-based microfluidic aptasensor for the point-of-care detection of sulfadimethoxine

Sulfadimethoxine antibiotics (SDM) are commonly used in aquatic foods to inhibit bacteria, but their residues in aquatic food pose certain risks to public health. Herein, we developed a systematic portable biosensing platform for SDM, which comprised a dual-mode three-dimensional paper-based microfluidic chip (3D-μPAD), a dual-light portable device, and a smartphone application for obtaining results. The detection principle of the dual-mode 3D-μPAD was based on the aggregation of Ag NPs without the protection of aptamers and the inner filter effect (IFE) between Mg, N-CDs and Ag NPs. With the addition of SDM, the significant change of two signals can be sensitively recognized in the portable device and calculated by a self-developed mini program in the smartphone to obtain the detection results. Under optimal conditions, SDM was sensitively detected in the range of 10–1000 ng/mL with an estimated limit of detection (LOD) of 0.13 ng/mL and 0.21 ng/mL in fluorescence and colorimetric modes, respectively. Moreover, this platform was successfully applied to determine SDM in fish with recoveries of 96.7%− 113.6% and 98.2%− 105.1%, respectively. This method has the advantages of low detection cost, low reagent consumption, and unlimited instruments and operators, which better fulfills the point-of-care needs of hazards analysis in food.

A portable multi-channel fluorescent paper-based microfluidic chip based on smartphone imaging for simultaneous detection of four heavy metals

Due to the excessive contamination of heavy metals pollution, it is very urgent and necessary to develop a real-time detection method for the heavy metals in food. As a target sensing device, a paper-based microfluidic device (μPAD) has the advantages of simplicity, low-cost, and portability. In this study, a self-driven microfluidic paper-based chip was first developed for the simultaneous detection of four targets. The channels on the microfluidic chip were prepared by using wax printing and automatic screen printing on the filter paper, where liquid flowed by capillary force without pump assistance. Based on the specific binding ability of aptamers to heavy metals, a “turn-on” fluorescence aptasensor for the simultaneous detection of four heavy metal ions was developed on the proposed multi-channel device via smartphone imaging. The obtained fluorescence images were digitized into RGB color values by Image J software, and an M-mode was established to realize the quantitative detection of heavy metal ions. Under optimal conditions, the limits of detection for lead(II), mercury(II), cadmium(II), and arsenic(III) were 4.20 nM, 1.70 nM, 2.04 nM, and 1.65 nM, respectively. Furthermore, the aptasensor was successfully applied to the quantitative detection of four heavy metal ions in apple and lettuce samples with recovery rates of 84.0%–104.1%.

A rapid and sensitive smartphone colorimetric sensor for detection of ascorbic acid in food using the nanozyme paper-based microfluidic chip

Ascorbic acid is very important to human health because of its excellent antioxidant effect. Developing sensitive and on-site detection methods is therefore in high demand. In this work, a portable paper-based colorimetric sensor with a smartphone platform with an ultrahigh sensitivity has been designed for on-site and quantitative analysis of ascorbic acid based on AuNPs nanozyme activity. The developed excellent peroxidase-like nanozymes, could effectively catalyze the oxidation of chromogenic substrates by H2O2. Herein, the AuNPs nanozyme activity are embedded on paper pieces to construct paper-based microfluidic chips for visual detection. Meanwhile, a smartphone platform is integrated for the signal readout. Using ascorbic acid as an analyte model, the proposed paper-based analysis platform shows a reliable and sensitive detection of ascorbic acid with a low detection limit of 0.406 μmol/L. The platform also works well in various real samples. This analysis method is facile in design, showing a great application potential for on-site and mass screening of ingredients in the environment and in foods.

A hinged paper-based microfluidic chip for quantitative detection of lead ions with naked eyes

A hinged paper-based microfluidic chip for quantitative detection of lead ions with naked eyes

Low-cost, portable, on-site fluorescent detection of As(III) by a paper-based microfluidic device based on aptamer and smartphone imaging.

A turn-on fluorescent aptasensor based on a paper-based microfluidic chip was developed to detect arsenite via aptamer competition strategy and smartphone imaging. The chip was prepared by wax-printing hydrophilic channels on filter paper. It is portable, low-cost, and environmentally friendly. Double-stranded DNA consisting of aptamer and fluorescence-labeled complementary strands was immobilized on the reaction zone of the paper chip. Due to the specific strong binding between aptamer and arsenite, the fluorescent complementary strand was squeezed out and driven by capillary force to the detection area of the paper chip, so that the fluorescent signal arose in the detection area under the excitation wavelength of 488nm. Arsenite can be quantified by using smartphone imaging and RGB image analysis. Under the optimal conditions, the paper-based microfluidic aptasensor exhibited excellent linear response over a wide range of 1 to 1000nM, with a detection limit as low as 0.96nM (3σ).

Detection of IgG protein in human urine based on vertical flow paper microfluidic chip

The kidney is the body's most important organ and the protein components in urine could be detected for diagnosing certain diseases. The amount of IgG protein in urine could be used to determine the degree of kidney function damage. IgG protein in human urine was detected by vertical flow paper-based microfluidic chip, double-antibody sandwich immunoreaction, and cell phone image processing. The results showed that using an IgG antibody concentration of 500 μg/mL and a gold standard antibody concentration of 100 μg/mL, the image signal showed a good linear relationship in the range of IgG concentration of 0.2-3.2 μg/mL, with R2=0.973 3 achieved. A complete set of detection devices were designed and the detection method showed good non-specificity.

Capillary flow velocity profile analysis on paper-based microfluidic chips for screening oil types using machine learning

We conceived a novel approach to screen oil types on a wax-printed paper-based microfluidic platform. Various oil samples spontaneously flowed through a micrometer-scale channel via capillary action while their components were filtered and partitioned. The resulting capillary flow velocity profile fluctuated during the flow, which was used to screen oil types. Raspberry Pi camera captured the video clips, and a custom Python code analyzed them to obtain the capillary flow velocity profiles. 106 velocity profiles (each with 125 frames for 5 s) were recorded from various oil samples to build a training database. Principal component analysis (PCA), support vector machine (SVM), and linear discriminant analysis (LDA) were used to classify the oil types into heavy-to-medium crude, light crude, marine fuel, lubricant, and diesel oils. The second-order polynomial SVM model with PCA as a pre-processing step showed the highest accuracy: 90% in classifying crude oils and 81% in classifying non-crude oils. The assay took less than 30 s from the sample to answer, with 5 s of the capillary action-driven flow. This simple and effective assay will allow rapid preliminary screening of oil types, enable early tracking, and reduce the number of suspect samples to be analyzed by laboratory fingerprinting analysis.