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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]

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]

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]

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]

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]