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An electrochemical-biosensor (EC-biosensor) microchip consisting of screen-printed electrodes and a double-layer reagent paper detection zone impregnated with amaranth is proposed for the rapid determination of microalbuminuria (MAU) in human urine samples. Under the action of an applied deposition potential, the amaranth is adsorbed on the electrode surface and the subsequent reaction between the modified surface and the MAU content in the urine sample prompts the formation of an inert layer on the electrode surface. The inert layer impedes the transfer of electrons and hence produces a drop in the response peak current, from which the MAU concentration can then be determined. The measurement results obtained for seven artificial urine samples with known MAU concentrations in the range of 0.1–40 mg/dL show that the measured response peak current is related to the MAU concentration with a determination coefficient of R2 = 0.991 in the low concentration range of 0.1–10 mg/dL and R2 = 0.996 in the high concentration range of 10–40 mg/dL. Furthermore, the detection results obtained for 82 actual chronic kidney disease (CKD) patients show an excellent agreement (R2 = 0.988) with the hospital analysis results. Overall, the results confirm that the proposed detection platform provides a convenient and reliable approach for performing sensitive point-of-care testing (POCT) of the MAU content in human urine samples.

A microfluidic colorimetric detection (MCD) platform consisting of a sliding hybrid PMMA/paper microchip and a smart analysis system is proposed for the convenient, low-cost and rapid analysis of human urine and whole blood samples. The sliding PMMA/paper microchip comprises a PMMA microfluidic chip for sample injection and transportation, a paper strip for sample filtration (urine) or separation (blood), and a sealed paper-chip detection zone for sample reaction and detection. In the proposed device, the paper-chip is coated with bicinchoninic acid (BCA) and biuret reagent and is then assembled into the PMMA microchip and packaged in aluminum housing. In the detection process, the PMMA/paper microchip is slid partially out of the housing, and 2 μL of sample (urine or whole blood) is dripped onto the sample injection zone. The chip is then slid back into the housing and the sample is filtered/separated by the paper strip and transferred under the effects of capillary action to the sealed paper-chip detection zone. The housing is inserted into the color analysis system and heated at 45 °C for 5 min to produce a purple-colored reaction complex. The complex is imaged using a CCD camera and the RGB color intensity of the image is then analyzed using a smartphone to determine the total protein (TP) concentration of the sample. The effectiveness of the proposed method is demonstrated using TP control samples with known concentrations in the range of 0.03–5.0 g/dL. The detection results obtained for 50 human urine samples obtained from random volunteers are shown to be consistent with those obtained from a conventional hospital analysis system (R2 = 0.992). Moreover, the detection results obtained for the albumin (ALB) and creatine (CRE) concentrations of 50 whole blood samples are also shown to be in good agreement with the results obtained from the hospital analysis system (R2 = 0.982 and 0.988, respectively).

An integrated microfluidic Au nanoparticle (AuNP) aptasensor device is proposed for monitoring the concentration of potassium (K

Focusing particles into a tight stream is critical for many microfluidic particle-handling devices such as flow cytometers and particle sorters. This work presents a fundamental study of the passive focusing of polystyrene particles in ratchet microchannels via direct current dielectrophoresis (DC DEP). We demonstrate using both experiments and simulation that particles achieve better focusing in a symmetric ratchet microchannel than in an asymmetric one, regardless of the particle movement direction in the latter. The particle focusing ratio, which is defined as the microchannel width over the particle stream width, is found to increase with an increase in particle size or electric field in the symmetric ratchet microchannel. Moreover, it exhibits an almost linear correlation with the number of ratchets, which can be explained by a theoretical formula that is obtained from a scaling analysis. In addition, we have demonstrated a DC dielectrophoretic focusing of yeast cells in the symmetric ratchet microchannel with minimal impact on the cell viability.

Sodium dehydroacetate (NADH) has good antibacterial effects and is widely used as a preservative in dairy products. However, NADH is toxic in large amounts, so it must be added to food in accordance with regulations. Accordingly, the current study has developed a microfluidic analysis detection (MAD) system for the determination of NADH in foods incorporating a microfluidic PMMA-paper chip and a smart analysis device. In this system, the extracted NADH sample is dropped into the sample chamber of the microfluidic PMMA-paper chip and is then wicking/filtering through paper strips and transferred to a detection zone embedded with Fe-Alum reagent. The chip is heated at 35 °C for 5 min to produce a compound reaction and the color compound image acquired by a camera is then transmitted wirelessly to a smartphone, where the NADH concentration is obtained by the intensity inversion of RGB analysis. A standard calibration curve is determined using NADH control samples with concentrations in the range of 30–5000 ppm. The feasibility of the proposed MAD system is then evaluated by analyzing the NADH concentrations of 15 commercial dairy products. It is shown that the measured values deviate from those obtained using an official high performance liquid chromatography (HPLC) method by no more than 5.0%.

A novel detection system consisting of a three-dimensional (3-D) sliding hybrid microchip (SHM) and a smart analysis device is presented to determine the phosphorus concentration in whole blood samples. The novelty of the SHM detection system includes filtering whole blood directly into serum, reacting different reagents in stages, performing a closed-type reaction to prevent evaporation of the test sample and uniform heating. The SHM is fabricated on PET and PMMA substrates and incorporates a sample injection zone, a filter paper-strip, two paper-chip reagent zones (reagent A and reagent B), and a detection zone. In the proposed detection method, 6 μL of whole blood sample is injected into the sample chamber and is filtered / separated by the paper-strip as it diffuses toward reagent zone A under the effects of capillary action. After 1 min, the sliding mechanism of the SHM is activated such that reagent zone B is positioned over reagent zone A in the detection/reaction zone. The SHM is then inserted into the smart analysis device and heated at 35°C for 4 min to prompt a modified molybdenum blue reaction. Finally, the blood phosphorus concentration is measured through a colorimetric method performed by a self-developed color analysis app installed on a smartphone. The feasibility of the current SHM detection system is demonstrated by the known control serum phosphorus concentrations ranging from 0.1–9 mg/dL. It is shown that the total R + B + G color intensity of the reaction complex image (Y) is linearly related to the serum phosphorus concentration (X) as Y = -31.502X + 600.740. The coefficient of determination (R2) and detection limit are 0.9936 and 0.06 mg/dL, respectively. The phosphorus concentration detection results obtained using the current SHM system for the whole blood samples of 100 real-world chronic kidney disease (CKD) patients are shown to be in excellent consistent with the detection results acquired through a macroscopic technique. Overall, the current SHM detection system provides a rapid and reliable method to detect the phosphorus concentration in whole blood samples.