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Rapid, simple, and sensitive analysis of relevant proteins is crucial in many research areas, such as clinical diagnosis and biomarker detection. In particular, clinical data on cancer biomarkers show great promise in forming reliable predictions for early cancer diagnostics, although the current analytical systems are difficult to implement in regions of limited recourses. Paper-based biosensors, in particular, have recently received great interest because they meet the criteria for point-of-care (PoC) devices; the main drawbacks with these devices are the low sensitivity and efficiency in performing quantitative measurements. In this work, we design a low-cost paper-based nanosensor through plasmonic calligraphy by directly drawing individual plasmonic lines on filter paper using a ballpoint pen filled with gold nanorods (AuNR) as the colloidal ink. The plasmonic arrays were further successively coated with negatively and positively charged polyelectrolyte layers employed as dielectric spacers to promote the enhancement of the emission of carboxyl-functionalized quantum dots (QD)—previously conjugated with specific antibodies—for indirect detection of the carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5). The efficiency, sensitivity, as well as the specificity of our portable nanosensor were validated by recording the luminescence of the QD@Ab complex when different concentrations of CEACAM5 were added dropwise onto the calligraphed plasmonic arrays. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fabrication of paper disc interfaced immunodevice for detecting diverse biomarker. • Highly sensitive and affordable disease detection tool. • Validated with range of spiked and real samples. • Universal sensing ability was accessed using C-reactive protein and potato viruses. The detection of specific biomarkers is used in various phases of the diagnosis of plant and human diseases, from prognosis to monitoring. Herein, we report a Prussian blue nanocube-modified immunodevice interfaced with a paper disc for the detection of plant biomarkers via streptavidin-biotin recognition. The detection ability of the immunodevice was assessed using Potato virus X as a model biomarker and analyzed using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. The immunodevice displayed excellent performance for Potato virus X detection with a detection limit of 0.92 nM (3S/N). The selectivity of the fabricated Potato virus X immunodevice was investigated using closely associated antigens, such as potato aucuba mosaic virus, Potato virus Y, and Potato virus A. The Potato virus X immunodevice exhibited ∼ 90 % recovery in spiked complex plant samples with a relative error of ∼ 9 %. Furthermore, the immunodevice was used to screen for Potato virus X in 10 samples from potato tubers and leaves. The paper-disc-interfaced immunodevice was also evaluated by detecting other biomarkers, such as potato aucuba mosaic virus in plant diseases and C-reactive protein in human ones. This immunodevice may allow the on-site monitoring of diverse biomarkers by simplifying the current point of care diagnostic tools. [ABSTRACT FROM AUTHOR]

The lack of sensitivity is a major problem among microfluidic paper-based analytical devices (μPADs) for early disease detection and diagnosis. Accordingly, the present study presents a method for improving the enrichment factor of low-concentration biomarkers by using shallow paper-based channels realized through a double-sided wax-printing process. In addition, the enrichment factor is further enhanced by exploiting the ion concentration polarization (ICP) effect on the cathodic side of the nanoporous membrane, in which a stationary sample plug is obtained. The occurrence of ICP on the shallow-channel μPAD is confirmed by measuring the current–voltage response as the external voltage is increased from 0 to 210 V (or the field strength from 0 to 1.05 × 104 V m−1) over 600 s. In addition, to the best of our knowledge, the electroosmotic flow (EOF) speed on the μPAD fabricated with a wax-channel is measured for the first time using a current monitoring method. The experimental results show that for a fluorescein sample, the concentration factor is increased from 130-fold in a conventional full-thickness paper channel to 944-fold in the proposed shallow channel. Furthermore, for a fluorescein isothiocyanate-labeled bovine serum albumin (FITC-BSA) sample, the proposed shallow-channel μPAD achieves an 835-fold improvement in the concentration factor. The concentration technique presented here provides a novel strategy for enhancing the detection sensitivity of μPAD applications. [ABSTRACT FROM AUTHOR]

This manuscript describes the development and clinical testing of a paper-based, metabolic assay designed for rapid, semi-quantitative measurement of organophosphate poisoning. Paper-based platforms, including point-of-care devices and 96-well plates, provided semi-quantitative information regarding the concentration of AchE (a biomarker for organophosphate poisoning). The paper-based 96-well-plate developed and implemented in this study was used to measure the level of organophosphate poisoning in three different clinical patients. Results were comparable to those obtained using conventional hospital methods currently considered the “gold standard”. This diagnostic device offers several advantages over conventional methods, including short operating time (twice as fast as conventional methods), procedure simplicity, and reduced fabrication cost. With further commercialization efforts, the methods described in this manuscript could be applied to a wide range of potential diagnostic applications in the field. [ABSTRACT FROM AUTHOR]

Paper, a cheap and ubiquitous material, has great potential to be used as low-cost, portable and biodegradable platform for chemical and biological sensing application. In this paper, we are exploring a low-cost, flexible and reliable method to effectively pattern paper for capturing optical dyes and for flow-based delivery of target samples for colorimetric chemical sensing. In this paper, we target the detection of ammonia (NH 3 ) and carbon dioxide (CO 2 ), two of the important environmental and health biomarkers. By functionalizing the paper platform with diverse cross-reactive dyes sensitive to NH 3 and CO 2 , their selective sensing within a certain pH range, as well as their detection at different concentrations can be achieved. The images of paper based device were captured by a flatbed scanner and processed in MATLAB ® using a RGB model and PCA for quantitative analysis. Paper based devices with readout using ubiquitous consumer electronic devices (e.g. smartphones, flatbed scanner) are considered promising approaches for disease screening in developing countries with limited resources. [ABSTRACT FROM AUTHOR]

Abstract: Paper based colorimetric biosensing platform utilizing cross-linked siloxane 3-aminopropyltriethoxysilane (APTMS) as probe was developed for the detection of a broad range of targets including H2O2, glucose and protein biomarker. APTMS was extensively used for the modification of filter papers to develop paper based analytical devices. We discovered when APTMS was cross-linked with glutaraldehyde (GA), the resulting complex (APTMS–GA) displays brick-red color, and a visual color change was observed when the complex reacted with H2O2. By integrating the APTMS–GA complex with filter paper, the modified paper enables quantitative detection of H2O2 through the monitoring of the color intensity change of the paper via software Image J. Then, with the immobilization of glucose oxidase (GOx) onto the modified paper, glucose can be detected through the detection of enzymatically generated H2O2. For protein biomarker prostate specific antigen (PSA) assay, we immobilized capture, not captured anti-PSA antibody (Ab1) onto the paper surface and using GOx modified gold nanorod (GNR) as detection anti-PSA antibody (Ab2) label. The detection of PSA was also achieved via the liberated H2O2 when the GOx label reacted with glucose. The results demonstrated the possibility of this paper based sensor for the detection of different analytes with wide linear range. The low cost and simplicity of this paper based sensor could be developed for “point-of-care” analysis and find wide application in different areas. [Copyright &y& Elsevier]

This article describes the use of microfluidic paper-based analytical devices (μPADs) to perform quantitative chemical assays with internal standards. MicroPADs are well-suited for colorimetric biochemical assays; however, errors can be introduced from the background color of the paper due to batch difference and age, and from color measurement devices. To reduce errors from these sources, a series of standard analyte solutions and the sample solution are assayed on a single device with multiple detection zones simultaneously; an analyte concentration calibration curve can thus be established from the standards. Since the μPAD design allows the colorimetric measurements of the standards and the sample to be conducted simultaneously and under the same condition, errors from the above sources can be minimized. The analytical approach reported in this work shows that μPADs can perform quantitative chemical analysis at very low cost. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We first reported a novel visualized instrument-free signal conversion method on paper for cardiovascular biomarker detection based on the coffee-ring effect (CRE). Our strategy was based on the principle that cTnI was captured by DNA probe decorated detection antibody to form sandwich complex, which could hybridize with H1 probes to form G-quadruplex DNAzyme. As a peroxidase mimic, G-quadruplex DNAzyme could catalyze colorimetric reaction and generate colored products, which were converted to the end edge of the paper by evaporation-driven flow, forming a visible colored band. Hence, the resulted colored signals were converted to distance signal by CRE, so that the quantification of cTnI could be measured easily only by a ruler. Our results demonstrated that the length of the colored bands was proportional to the concentration of cTnI, with a limit of detection of 1.0 pg/mL. Furthermore, this strategy not only showed advanced performance to discriminate cTnI from complex samples but also exhibited high accuracy with standard method in real sample. Hence, these results demonstrated that this method established a promising equipment-free and visualized platform for detecting various kinds of genetic diseases and biomarkers, further promoting the development of point-of-care testing (POCT) in biomedicine. • A visual Cardiovascular Biomarker detection strategy was developed. • The resulted colored signals were converted to distance signal by CRE. • This method developed equipment-free and visualized platform. [ABSTRACT FROM AUTHOR]