Developing a Portable Autofluorescence Detection System and Its Application in Biological Samples.

Advanced glycation end-products (AGEs) are complex compounds closely associated with several chronic diseases, especially diabetes mellitus (DM). Current methods for detecting AGEs are not suitable for screening large populations, or for long-term monitoring. This paper introduces a portable autofluorescence detection system that measures the concentration of AGEs in the skin based on the fluorescence characteristics of AGEs in biological tissues. The system employs a 395 nm laser LED to excite the fluorescence of AGEs, and uses a photodetector to capture the fluorescence intensity. A model correlating fluorescence intensity with AGEs concentration facilitates the detection of AGEs levels. To account for the variation in optical properties of different individuals' skin, the system includes a 520 nm light source for calibration. The system features a compact design, measuring only 60 mm × 50 mm × 20 mm, and is equipped with a miniature STM32 module for control and a battery for extended operation, making it easy for subjects to wear. To validate the system's effectiveness, it was tested on 14 volunteers to examine the correlation between AGEs and glycated hemoglobin, revealing a correlation coefficient of 0.49. Additionally, long-term monitoring of AGEs' fluorescence and blood sugar levels showed a correlation trend exceeding 0.95, indicating that AGEs reflect changes in blood sugar levels to some extent. Further, by constructing a multivariate predictive model, the study also found that AGEs levels are correlated with age, BMI, gender, and a physical activity index, providing new insights for predicting AGEs content and blood sugar levels. This research supports the early diagnosis and treatment of chronic diseases such as diabetes, and offers a potentially useful tool for future clinical applications.

A portable ascorbic acid in sweat analysis system based on highly crystalline conductive nickel-based metal-organic framework (Ni-MOF).

Conductive metal-organic frameworks can provide unique porous structures, large pore volumes, many catalytically active sites and high crystallinity, and so are becoming increasingly important and attractive as electrocatalytic materials. The present work synthesized nanorods of the conductive compound Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2 (Ni3(HITP)2) with a high degree of crystallinity from HITP ligands and Ni2+ ions. Screen-printed electrodes made with this material were employed to fabricate an enzyme-free sensor for the detection of ascorbic acid (AA). The sensor exhibited good catalytic activity during the electrocatalytic analysis of AA in alkaline media, attributed to the synergistic effect of highly active Ni-N4 catalytic sites in the nanorods, the two-dimensional superimposed honeycomb lattice of the Ni3(HITP)2, and the large specific surface area of this material. The latter property facilitated efficient electron transfer during catalytic oxidation. A portable electrochemical AA detection system was developed using Ni3(HITP)2 as the electrode material together with application-specific integrated circuits and a smartphone application with App. Good sensing performance was obtained, including a wide linear range (2-200 µM) with high sensitivity (0.814 µA µM-1 cm-2), and low detection limit (1 µM). This system can be used to monitor AA levels and trends in sweat to assess vitamin C intake as a part of personal health management.

Microfluidic paper-based chip platform for benzoic acid detection in food.

An integrated microfluidic platform comprising a microfluidic paper-based analytical device (µPAD) and a portable detection system is proposed for the concentration detection of benzoic acid via Janovsky reaction theory. In the proposed approach, the reaction zone of the µPAD is implanted with 5 N sodium hydroxide and dried at 30 °C for 20 min. The benzoic acid sample is derived to 3,5-Dinitrobenzoic acid using KNO3 and H2SO4 at 40 °C for 40 min and is then dripped on the reaction zone of the µPAD. Finally, the µPAD is transferred to the portable detection system and heated at a temperature of 45 °C for 20 min on a hot plate to prompt a Janovsky reaction. The resulting color change of the detection zone is observed using a CMOS camera. The reaction color image is delivered to a smartphone via a connector and the benzoic acid concentration is determined using self-written RGB analysis software. The experimental results obtained using control samples with known benzoic acid concentrations in the range of 500-4000 ppm show that the R(ed) + B(lue) intensity (Y) and benzoic acid concentration (X) are related as Y =  -0.0264 X + 408.79. Moreover, the correlation coefficient is equal to R2 = 0.9953. The proposed detection platform is used to measure the benzoic acid concentrations of twenty-one commercial food samples. It is shown that the concentration measurements deviate by no more than 6.6% from those obtained using a standard HPLC macroscale method. Overall, the results presented in this study show that the proposed integrated microfluidic paper-based chip platform provides a compact and reliable tool for benzoic acid concentration measurement purposes.