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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. [ABSTRACT FROM AUTHOR]

The germination of bacterial spores presents a considerable challenge to health and safety due to the current scarcity of cost-effective and efficient tools for their prompt identification. Addressing this critical need, our study introduces a novel paper-based ratiometric fluorescence sensor platform utilizing a composite of Eu3+-doped carbon quantum dots (CQDs) within ZIF-8 (Eu3+-CQDs@ZIF-8). This platform facilitates the rapid detection of 2, 6-pyridinedicarboxylic acid (DPA), a biomarker of bacterial spore germination. To fabricate this sensor, CQDs and Eu3+ ions were synergistically integrated into the ZIF-8 framework. The resultant composite was then applied to filter paper via screen printing technology, creating a paper-based microfluidic analytical device (μPAD). During the process of detecting DPA, strong coordination between DPA and Eu3+ ions is established, resulting in an enhanced red emission due to energy transfer through the antenna effect. Concurrently, the interaction between DPA and CQDs leads to a quenching of the CQDs' green fluorescence, enabling a ratiometric detection of DPA. The efficacy of this composite material was validated through the visualization of DPA release during spore germination. Further enhancing the platform's utility, integration with a smartphone enabled the quantification of DPA concentrations in real samples by analyzing the red-to-green (R/G) value in the detection area. Demonstrating rapid, sensitive, and precise DPA detection, the platform confirms its suitability for practical applications. Conclusively, with its compact design, straightforward preparation, and comprehensive integration, this sensor platform emerges as a promising solution for on-site spore detection, highlighting its potential for widespread testing applications. [ABSTRACT FROM AUTHOR]

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.

Cardiovascular disease is a major global public health challenge. Point-of-- care testing (POCT) technologies are crucial for the prevention, early diagnosis, and treatment of cardiovascular conditions. Numerous POCT technologies for cardiovascular disease are currently available, which include but are not limited to conventional methods, paper-based microfluidic technology, microfluidic chip technology, electrochemical detection technology, ultrasonic detection technology, and smartphone-based detection technology. Each method has a broad range of applications and performs differently across various detection scenarios. This article offers a comprehensive analysis of current POCT technologies for cardiovascular disease, assessing their effectiveness, limitations, and future development directions. The aim is to provide insights and theoretical references for innovative research and clinical applications in POCT methods for cardiovascular disease., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

The presence of fluoroquinolone (FQs) antibiotic residues in the food and environment has become a significant concern for human health and ecosystems. In this study, the background-free properties of upconversion nanoparticles (UCNPs), the high specificity of the target aptamer (Apt), and the high quenching properties of graphene oxide (GO) were integrated into a microfluidic-based fluorescence biosensing chip (MFBC). Interestingly, the microfluidic channels of the MFBC were prepared by laser-printing technology without the need for complex preparation processes and additional specialized equipment. The target-responsive fluorescence biosensing probes loaded on the MFBC were prepared by self-assembly of the UCNPs-Apt complex with GO based on π-π stacking interactions, which can be used for the detection of the two FQs on a large scale without the need for multi-step manipulations and reactions, resulting in excellent multiplexed, automated and simultaneous sensing capabilities with detection limits as low as 1.84 ng/mL (enrofloxacin) and 2.22 ng/mL (ciprofloxacin). In addition, the MFBC was integrated with a smartphone into a portable device to enable the analysis of a wide range of FQs in the field. This research provides a simple-to-prepare biosensing chip with great potential for field applications and large-scale screening of FQs residues in the food and environment. [Display omitted] [ABSTRACT FROM AUTHOR]

Here, a smartwatch for sweat monitoring was presented for perspiration analysis. The smartwatch played the part of analyzing, computing, and displaying the real‐time data with the feature of comfortable wearing and lightweight ergonomic design. Moreover, the paper‐based microfluidic patch with a three‐dimensional structure was proposed to realize the sweat collection and solve the issue of sweat accumulation. To further realizing the sweat monitoring, the potassium and sodium ion‐selective electrodes were developed by the screen‐printing technique. The experiment of on‐body monitoring the K+ and Na+ in sweat had been carried out to further demonstrate the feasibility of the smartwatch. [ABSTRACT FROM AUTHOR]

Abstract Currently, the standard method for identifying biological agents of potential threats to national security and public health, such as pathogens, virus, and toxins, mainly rely on microbiological cultivation. This method is time-consuming and it requires sophisticated equipment and well-trained personnel, which are often unavailable in remote areas or at point-of-need. Therefore, an alternative rapid, simple, and sensitive method for detecting bio-threat agents is in crucial need. We report a paper-based Vertical Flow Immunoassay (VFI) device that can overcome these limitations. The VFI device utilizes a nanoporous nitrocellulose membrane encapsulated in a stainless steel filter holder. As the sample is pushed through the membrane, which is pre-functionalized with capture antibody, a sandwich assay is formed and colorimetric signal is generated to reflect the presence of target antigens. Through theoretical analyses of antigen-antibody binding process inside a porous membrane, we identified two critical factors – membrane pore size and sample flow rate that can be optimized to improve the assay sensitivity. Then, the effects were demonstrated through experimental studies using Burkholderia pseudomallei (the causative agent of melioidosis) as a model pathogen. The B. pseudomallei VFI was based on an immunoassay targeting the B. pseudomallei surface capsular polysaccharide (CPS). The experimental results agreed well with the theory showing that increasing the flow speed (up to 1.06 mm/s) and reducing the membrane pore size (down to 0.1 µm) could improve the sensitivity by at least 5 times. The VFI's limit-of-detection for CPS spiked in buffer solution was determined to be 0.02 ng/mL. The developed VFI shows great potential as a point-of-care tool for detection of bio-threat agents in a variety of clinical and resource-restricted conditions. Graphical abstract fx1 Highlights • Paper-based vertical flow device was developed to detect bio-threat pathogens. • Limit-of-detection for B. pseudomallei surface capsular polysaccharide was 0.02 ng/mL. • Sample flow rate and membrane pore size was studied in theory and experiment. • Multiplexing diagnostic of melioidosis and anthrax was demonstrated. [ABSTRACT FROM AUTHOR]

We present a paper-based microfluidic colorimetric immunosensor for the detection of carcinoembryonic antigen (CEA), using Co 2 (OH) 2 CO 3 -CeO 2 nanocomposite with extraordinary intrinsic peroxidase like activity. The morphology and composition of the nanocomposite characterized with Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. The proposed immunosensor facilely fabricated by loading mixture of ionic liquid and chitosan functionalized primary antibodies (Ab 1 ) on the surface of paper. Compared to traditional paper based immunodevice, when ionic liquid was used the nonspecific binding protein from the paper surface was more effectively removed. Secondary antibodies (Ab 2 ) were stacked on the surface of the carboxylated Co 2 (OH) 2 CO 3 -CeO 2 nanocomposite. The immunosensor response was obtained by a color change resulting from Co 2 (OH) 2 CO 3 -CeO 2 nanocomposite catalyzing the oxidation of 3,3′,5,5′-tetramethyl benzidine in the presence of H 2 O 2 . The colorimetric sensing was accomplished on the paper, using smartphone for taking a photo and then analyzing the colors with an installed application. Detection of CEA was performed by this method with a linear range from 0.002 to 75.0 ng mL −1 and a detection limit of 0.51 pg mL −1 . In this paper we developed simple, cost-effective and portable design for sensitive immunoassay and point-of-care diagnostics of cancer marker. [ABSTRACT FROM AUTHOR]

As a powerful tool, microfluidics has been widely used in bioanalysis due to the advantages of high portability, fewer sample requirements and rapid detection time. To achieve selective and sensitive detection, enzymes are commonly used as biorecognition elements. However, enzymes used in bioanalysis still suffer from high cost and low stability. Therefore, emerging nanozymes (nanomaterials with enzyme-like characteristics) have been developed to replace enzymes to address their shortcomings. The microfluidic devices based on nanozymes have attracted a lot of interest and shown great promise in bioanalysis via a simple, rapid, and portable approach. This review focuses on recent advances in typical nanozymes and nanozymes involved in cascaded reactions used in microfluidic bioanalysis. Additionally, the future challenges and perspectives are discussed for further development. [Display omitted] • Diverse enzyme-like activities of nanozymes were particularly highlighted. • Microfluidic bioanalyses using individual nanozymes were summarized. • Microfluidic bioanalyses based on nanozymes involved in cascade reactions were summarized. • Future trends in microfluidic bioanalysis based on nanozymes were proposed. [ABSTRACT FROM AUTHOR]

Paper-based fluorescence resonance energy transfer assay (FRET) is gaining great interest in detecting macro-biological molecule. It is difficult to achieve conveniently and fast detection for macro-biological molecule. Herein, a graphene oxide (GO)-based paper chip (glass fiber) integrated with fluorescence labeled single-stranded DNA (ssDNA) for fast, inexpensive and direct detection of biological macromolecules (proteins and nucleic acids) has been developed. In this paper, we employed the Cy3/FAM-labeled ssDNA as the reporter and the GO as quencher and the original glass fiber paper as data acquisition substrates. The chip which was designed and fabricated by a cutting machine is a miniature biosensor that monitors fluorescence recovery from resonance energy transfer. The hybridization assays and fluorescence detection were all simplified, and the surface of the chip did not require immobilization or washing. A Nikon Eclipse was employed as excited resource and a commercial digital camera was employed for capturing digital images. This paper-based microfluidics chip has been applied in the detection of proteins and nucleic acids. The biosensing capability meets many potential requirements for disease diagnosis and biological analysis. [ABSTRACT FROM AUTHOR]

It is difficult to carry out multiple detection of different type of chemicals because of the different chemical microenvironment requirements. Herein, a low-cost and simple paper-based microfluidic device integrated with fluorescence labeled single-stranded DNA (ssDNA) functionalized graphene oxide sensor was developed for the multiplex determination of different types of chemical contaminants in food. In this work, Cy5 labeled corresponding functional ssDNA for different analytes associated with graphene oxide (ssDNA-GO) were employed as core detection sensors to sensitively report the presence of the different type of chemicals as well as enlarge the chemical compatibility, which made it possible to simultaneous detect multiple chemicals under a same chemical microenvironment. Paper microfluidic device can be easily fabricated and paper substrate also facilitated the integration of ssDNA-GO sensors via physical absorption. This device has been successfully applied in multiplex detection of heavy metal mercury (II) ion (Hg 2+ ) and silver (I) ion (Ag + ) and aminoglycoside antibiotics residues in food. It also provided enormous potential for applications of environmental monitoring and clinical diagnosis. [ABSTRACT FROM AUTHOR]

Microfluidics technology holds a special place in the field of biomedical and analytical chemistry thanks to its properties, such as low consumption of reagent, quick analysis time, and ease of integration. Nanotechnology makes significant progress towards high sensitive and selective detection of analytes. Compared to bulk materials, nanomaterials have distinctive properties which motivate the combination of nanoparticles with biosensors. Nanoparticle-based biosensors can bring a series of advantages in advancement high-throughput and ultrasensitive detection. In recent years, numerous studies have been done on the integration of nanomaterials with microfluidic systems. Given the scope of the nanoparticle-integrated biosensors, the purpose of this review is to provide an overview of various types of nanoparticle-integrated microfluidic biosensors. It mainly focuses on developed microfluidics-based on gold nanoparticles, graphene oxide , quantum dots, magnetic nanoparticles, carbon dots, silica nanoparticles, zinc oxide, and nanocomposites. This review summarizes the latest advancement of nanotechnology-assisted microfluidic biosensing on a smartphone for biochemical analysis. Also, the role of nanomaterials on the detection methods such as electrochemical, photoelectrochemical, electrochemiluminescent, optical piezoelectric, and so on was surveyed. In our opinion, the cooperation of microfluidic biodevices and nanoparticles is very beneficial and is expected to be effective in addressing the challenges related to microfluidic systems. [Display omitted] • Recent advances and limitations in nanotechnology-assisted microfluidic biosensing were discussed. • The analytical figures of merit of the developed methods are also evaluated. • Current improvements on the monitoring of biomarkers using microfluidic strategies were investigated. [ABSTRACT FROM AUTHOR]

Antibiotics are used largely in agriculture and animal farming. As a result, antibiotic residues are found in food products as well as pharmaceutical industries and farming wastes. Since consumption of food products contaminated with antibiotic in excessive residuals causes severe environmental risks, our study here aims to detect the residues level of selected antibiotics in milk and egg. For monitoring of the antibiotic residues in various food diaries, low-cost, simple and rapid methods are required. This paper reports fabricating a disposable microfluidic paper-based analytical device for detection and discrimination of 8 antibiotics. This small but efficient device works based on combination of paper microfluidics, sensor array concept (an array of metallochromic complexes, which provides an optical tongue, and chemometrics data analysis. The discrimination is based on differential interaction of the antibiotics with 5 metal-indicator complexes and displacing the chromogenic indicators. This resulted in specific color changes for each antibiotic. The discriminant models obtained by employing linear discriminant analysis could discriminate antibiotics in real samples of milk and egg white and yolk at concentrations of as low as 5.0 mg L−1 with 100% accuracy. Also, semi-quantitative analysis was provided to detect trace amounts of the antibiotics (1.0 mg L−1). [Display omitted] • A μPAD in an array format of metallochromic complexes to provide an opto-electronic tongue. • The discrimination is based on differential interaction of the antibiotics with 5 metal-indicator complexes. • The μPAD results in specific color changes (colorimetric signature) for each antibiotic. • LDA could discriminate antibiotics in real samples of milk and egg white and yolk. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based sensors as a new type of microsample detection technology are widely used in medical diagnosis, environmental monitoring, and food safety testing. Inkjet printing has the advantages of simplicity, speed, flexibility, high resolution, low cost, and efficient mass production and has become one of the most cutting-edge technologies in the manufacture of paper-based sensors. In this work, a fully inkjet printing preparation method was proposed for paper-based sensors, which can achieve high-precision, multichannel, and visual fluorescence detection. Three kinds of fluorescent carbon dots (CDs; r-CDs, b-CDs, and y-CDs) were fabricated into inkjet ink by adding a suitable ratio of solvent, PEG, and surfactant FS3100 to control its viscosity, surface tension, and other influencing factors, obtaining the best-visualized fluorescence response on paper. To optimize the full inkjet printing process of the paper-based sensor, we studied the influence of factors such as the hydrophobic material AKD formula, postprocessing conditions, and the structure of the hydrophilic and hydrophobic channels on the paper-based detection accuracy, and it was found that proper AKD concentration, curing time, and temperature can make AKD fully react with paper-based surface groups and produce more hydrophobic groups on the surface and inside of the filter paper, which can form paper-based microfluidic sensors with clear boundaries and fast transmission speed at low cost and high efficiency. The fabricated sensor is used for the fluorometric determination of vitamin C (AA), NO 2 - , and sunset yellow (SY) at the same time, and the limits of visual detection by eyes are 6 mmol/L (NO 2 - ), 60 μmol/L (SY), and 40 mmol/L (AA). The mechanism of inkjet printing is investigated in detail, which is simple, reliable, and easy to realize mass production and can realize highly sensitive, on-site, and visual detection for food additives.

Paper is increasingly recognized as a portable substrate for cell culture, due to its low-cost, flexible, and special porous property, which provides a native cellular 3D microenvironment. Therefore, paper-based microfluidics has been developed for cell culture and biomedical analysis. However, the inability of continuous medium supply limits the wide application of paper devices for cell culture. Herein, a paper-based microfluidic device is developed with novel folded paper strips as wick-like structure, which is used for medium self-driven perfusion. The paper with patterns of hydrophilic channel, culture areas, and hydrophobic barrier could be easily fabricated through wax-printing. After printing, the hydrophilic paper strip at the periphery of the lower layer is then folded at 90° and extended into the medium container for continuous automatic supply of medium to the cell culture area. Tumor cells cultured in the paper device are tested for anti-cancer drug screening. Visualized cell viability and chemical sensitivity testing can be achieved by colorimetry combined with simple smartphone imaging, effectively reducing precision instrument dependence. The wick paper-based microfluidic device for cell culture endows the method the advantages of lower cost, ease-of-operation, miniaturization, and shows a great potential for large-scale cell culture, antibody drug production, and efficient screening., (© 2020 Wiley-VCH GmbH.)