Smartphone-Integrated Photoacoustic Analytical Device for Point-of-Care Testing of Food Contaminant Azodicarbonamide

A SERS-based point-of-care testing approach for efficient determination of diquat and paraquat residues using a flexible silver flower-coated melamine sponge

Diquat (DQ) and paraquat (PQ) residues in food are potential hazards to consumers' health. Point-of-care testing (POCT) of them remains challenging. Based on surface-enhanced Raman spectroscopy (SERS) technology, we developed a POCT strategy for DQ and PQ on apple surface and in apple juice. A point-of-use composite was fabricated using a piece of porous melamine sponge (MS) modified with silver nanoflowers (AgNFs), combining the specificity of the SERS fingerprint and the excellent adsorption capacity of MS. Using this dual-functional AgNFs@MS, the on-site determination of the DQ and PQ residues was completed within 3 min without pretreatment. Clear trends were observed between SERS intensity and logarithmic concentrations, with r values from 0.962 to 0.984. The limit of detection of DQ and PQ were 0.14-0.70 ppb in apple juice and on apple surface. This study provides a new point-of-use alternative for rapidly detecting DQ and PQ residues in nonlaboratory settings.

Portable Hadamard-Transform Raman Spectrometer: A Powerful Analytical Tool for Point-of-Care Testing

A portable Hadamard-transform Raman spectrometer with excellent performance was fabricated consisting of a 785 nm laser, an optical filter, an optical system, a control system, and a signal processing system. As the core of the spectrometer, the optical system was composed of a slit, collimator, optical grating, reflector, digital micromirror devices (DMD), lens system, and InGaAs photodetector. Compared with a conventional dispersive Raman spectrometer, the proposed Raman spectrometer adopted the DMD and corresponding controlling device (DLPC350 control chip) to collect the Raman spectrum. Thus, in our design, the gratings are fixed, while the full Raman spectrum was collected by the deflection of the micromirror. This design can greatly improve the vibration resistance ability of the spectrometer since the gratings are not rotating during the spectrum collecting. More importantly, Hadamard-transform was used as signal processing technology, which has the ability of faster calculation, the merits of high energy input, single detector multichannel simultaneous detection (imaging) ability, and high signal-to-noise ratio (SNR). Hence, the Hadamard-transform portable Raman spectrometer has the potential to be applied in the field of point-of-care testing (POCT).

Portable Photoacoustic Analytical System Combined with Wearable Hydrogel Patch for pH Monitoring in Chronic Wounds

Timely diagnosis, monitoring, and management of chronic wounds play crucial roles in improving patients' quality of life, but clinical evaluation of chronic wounds is still ambiguous and relies heavily on the experience of clinician, resulting in increased social and financial burden and delay of optimal treatment. During the different stages of the healing process, specific and dynamic changes of pH values in the wound exudate can be used as biomarkers to reflect the wound status. Herein, a pH-responsive agent with well-behaved photoacoustic (PA) properties, nitrazine yellow (NY), was incorporated in poly(vinyl alcohol)/sucrose (PVA/Suc) hydrogel to construct a wearable pH-sensing patch (PVA/Suc/NY hydrogel) for monitoring of pH values during chronic wound healing. According to Rosencwaig-Gersho theory and the combination of 3D printing technology, the PA chamber volume and chopping frequency were systematically optimized to improve the sensitivity of the PA analytical system. The prepared PVA/Suc/NY hydrogel patch had excellent mechanical properties and flexibility and could maintain conformal contact with skin. Moreover, combined with the miniaturized PA analytical device, it had the potential to detect pH values (5.0-9.0) free from the color interference of blood and therapeutic drugs, which provides a valuable strategy for wound pH value monitoring by PA quantitation. This strategy of combining the wearable hydrogel patch with portable PA analysis offers broad new prospects for the treatment and management of chronic wounds due to its features of simple operation, time savings, and anti-interference.

Visual detection of water content in liquor with near-infrared fluorescence sensor assisted by smartphone

Water content was an essential indicator in organic solvents, and it was necessary to develop a facile, cheap and readily available tool for the real-time, specifical and sensitive detection of water content. In this work, two novel D-π-A type near-infrared fluorescence sensors (DCM-1 and DCM-2) were designed and synthesized for the detection of trace water in organic solvents. DCM-1 and DCM-2 with solvent-dependent effects and large Stokes shift (>120 nm) showed good linear "intensity-to-content" relationships in four commonly-used organic solvents, and accomplished the ultra-fast and high-accuracy detection of the trace water in organic solvents. More importantly, a portable, fast, and accurate smartphone-assisted visual assay was designed for visual quantitative detection of the water content in organic solvents with a detection limit as low as 1.028 % v/v (e.g. in ethanol) and a wide detection range (0-60 % v/v). The smartphone-based visual assay was further applied to estimate the water content in disinfection alcohol and commercial liquor, which furnished a new strategy and broad prospects to achieve the accurate onsite detection of water content.

A label-free electrochemical aptasensor based on Bi-Sb alloy materials for potential POCT of HER-2

As a prognostic biomarker for breast cancer, human epidermal growth factor receptor 2 (HER-2) is of crucial diagnostic value. Here, a label-free electrochemical aptasensor was established for the ultrasensitive detection of HER-2 using a modified electrode of Bi-Sb alloy materials (Bi-Sb AMs). The performance of the aptasensor was enhanced greatly due to the introduction of Bi-Sb alloy materials (Bi-Sb AMs) with high conductivity. Furthermore, by integrating the aptasensor with the Sensit Smart U-disk electrochemical analyzer, the point-of-care testing (POCT) for HER-2 was realized. Under the optimal experimental parameters, the POCT analyzer showed a wide linear response from 0.01 pg mL-1 to 100 ng mL-1, with a low detection limit (LOD) of 5.96 fg mL-1 for the detection of HER-2. The presented POCT analyzer exhibited good specificity, stability, and reproducibility. Benefiting from the simple operation and rapid testing, the developed analyzer will have potential application in the prognostic diagnosis and treatment of breast cancer.

Using a Smartphone-Based Colorimetric Device with Molecularly Imprinted Polymer for the Quantification of Tartrazine in Soda Drinks

The present study reports the development and application of a rapid, low-cost in-situ method for the quantification of tartrazine in carbonated beverages using a smartphone-based colorimetric device with molecularly imprinted polymer (MIP). The MIP was synthesized using the free radical precipitation method with acrylamide (AC) as the functional monomer, N,N'-methylenebisacrylamide (NMBA) as the cross linker, and potassium persulfate (KPS) as radical initiator. The smartphone (RadesPhone)-operated rapid analysis device proposed in this study has dimensions of 10 × 10 × 15 cm and is illuminated internally by light emitting diode (LED) lights with intensity of 170 lux. The analytical methodology involved the use of a smartphone camera to capture images of MIP at various tartrazine concentrations, and the subsequent application of the Image-J software to calculate the red, green, blue (RGB) color values and hue, saturation, value (HSV) values from these images. A multivariate calibration analysis of tartrazine in the range of 0 to 30 mg/L was performed, and the optimum working range was determined to be 0 to 20 mg/L using five principal components and a limit of detection (LOD) of 1.2 mg/L was obtained. Repeatability analysis of tartrazine solutions with concentrations of 4, 8, and 15 mg/L (n = 10) showed a coefficient of variation (% RSD) of less than 6%. The proposed technique was applied to the analysis of five Peruvian soda drinks and the results were compared with the UHPLC reference method. The proposed technique showed a relative error between 6% and 16% and % RSD lower than 6.3%. The results of this study demonstrate that the smartphone-based device is a suitable analytical tool that offers an on-site, cost-effective, and rapid alternative for the quantification of tartrazine in soda drinks. This color analysis device can be used in other molecularly imprinted polymer systems and offers a wide range of possibilities for the detection and quantification of compounds in various industrial and environmental matrices that generate a color change in the MIP matrix.