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In this study, we developed a point-of-care assay platform with simultaneous detection and self-calibration capabilities for multiple targets based on a microfluidic paper-based analytical device (μPAD). This system is easily manufactured using a wax printing method on chromatographic paper. The design pattern consists of a zone of detection and a calibrant zone for controlled loading using wax barriers with different thicknesses. We showed the utility and applicability of this approach by a proof-of-concept study for two clinically important markers: glucose and lactate. With the naked eye, the results could be fully distinguished and recorded to evaluate the analytical performance with a flatbed scanner. The detection limits of glucose and lactate were 0.3125 mM and 0.2975 mM, respectively, and simultaneous detection was possible from a small sample (0.4 μL) with high sensitivity. Furthermore, this device has a self-calibration function, which minimizes the influence of environmental conditions (i.e., ambient light intensity, temperature, humidity, and pressure). Therefore, the developed multiplex paper-based device is promising for clinical multianalyte point-of-care testing since it is easy to manufacture, cost-effective, user-friendly, and highly sensitive., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The research progress in the centrifugal microfluidic platform provides great opportunities for simple and effective analytical measurements in a variety of areas including biomedical engineering. In this study, we propose an optical reader that can measure the transmittance in a very sensitive and rapid manner on a hybrid paper-polymer centrifugal disc platform. This device enables real-time monitoring of multiple samples by measuring the absorbance of the light transmitted through the paper integrated on the disc between the light emitting diode (LED) and the photodiode (PD) regardless of the ambient light condition. To confirm its efficiency, we analyzed one of the blood's important indicators, glucose in a successful manner within 10 s without any additional complex image analysis. In addition, we discussed the results by comparing with the reflectance-based methods and with those of the previously reported studies by introducing a figure of merit to evaluate the performance of the assay., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Advancements in technology have led to the use of smartphones as biosensor detectors. However, it is difficult to obtain stable color information of colorimetric sensors using multiple smartphones owing to different light conditions and image correction operations. In this study, we attempted color detection of the colorimetric paper chip using smartphone-embedded light-emitting diode (LED) and simple transformation calculation. This method enables the acquisition of stable color information using different smartphones by reducing the influence of external light sources. Moreover, we studied characteristics such as convergence and distinction of detection result details by the manufacturers and smartphones. These findings suggested the necessity of classification criteria for the use of smartphones to achieve optimal detection. In addition, white and black references were used to set the standard for color correction of various light sources. Based on our results, we conclude that this approach presents the possibility of smartphone-based colorimetric detection in practical applications. Image 1 • We have attempted to quantify the bio-diagnostic assay by using various smartphones. • The effect of the external light environment is reduced by the smartphone LED and correction method. • The deviation between CMOS image sensors in various smartphones is reduced through contrast stretching method. [ABSTRACT FROM AUTHOR]

• The optical reader was developed for the colorimetric measurement of a wax printed paper-disc platform. • The device was demonstrated by simultaneous determination of glucose and lactate by in situ real-time absorbance measurement. • Analysis results can be delivered with low detection limits, high accuracy, and high specificity within 20 s. • This approach can be widely used for colorimetric quantitation where simultaneous analysis of parallel reactions is required. In this study, we developed a wax printed paper-disc centrifugal optical device platform and simultaneously detected glucose and lactate through real-time absorbance measurements. The disposable paper module was manufactured using a simple wax printing method and was incorporated into reusable discs for colorimetric monitoring. Moreover, the paper-disc's self-calibration capability minimizes the effects of ambient conditions (ambient light, temperature, humidity and measurement time, etc.), enabling quantification with high accuracy and precision. The photodiode (PD) and light-emitting diode (LED) of the developed optical devices were able to monitor the color conversion in multiple reaction zones on a rotating paper-disc in real-time, regardless of ambient light conditions. Quantitative results were available in less than 20 s and did not require any complex image analysis. The detection limits of glucose and lactate were 27.2 μ M and 29.6 μ M, respectively, and simultaneous detection of glucose and lactate was possible even with a small serum volume (1.0 μ L). Thus, the developed wax printed paper-disc centrifugal optical device platform has promising prospects for clinical multianalyte point-of-care testing due to easy manufacturing, cost-effectiveness, user-friendliness, and high sensitivity. [ABSTRACT FROM AUTHOR]