Smartphone-Assisted Protein to Creatinine Ratio Determination on a Single Paper-Based Analytical Device

Microfluidic paper-based analytical device for simultaneous determination of calcium and magnesium ions in human serum

BACKGROUND

Calcium and magnesium ions are highly abundant and important cations in human body. At the same time, both dyscalcemia and dysmagnesemia are frequently encountered in the clinical practice. As deficiency or excess of Ca(II) or Mg(II) can cause severe symptoms, determining these ions in serum is of great importance. Concentration of these ions in biological samples is typically assayed in clinical laboratories with the use of expensive and specialized equipment. Since those methods cannot be easily adapted for self-diagnosis purposes, there is a great need to develop a convenient tool for reliable determination of calcium and magnesium in serum at the point-of-care.

RESULTS

The colorimetric methods employed for calcium and magnesium analysis were o-cresophtalein complexone assay and xylidyl blue assay, respectively. Analytical signal acquisition was accomplished using an ordinary flatbed scanner or smartphone and free software. For increased user-friendliness the device was optimized to perform simultaneous determination of calcium and magnesium ions in only 10 min. In the optimized conditions, the limit of detection for calcium ions was 0.09 mmol L-1, while for magnesium it was 0.04 mmol L-1. Determination of both ions requires only 4 μL of serum sample. The developed paper-based sensors were validated with control human serum samples and the obtained relative errors for majority of samples were below 20 %.

SIGNIFICANCE

In this paper, a microfluidic paper-based analytical device for simultaneous determination of calcium and magnesium ions in human serum is reported for the first time. Additionally, this is also the first report on colorimetric determination in serum of any of these ions in paper-based format. Simultaneous detection of both ions allows for fast and user-friendly screening of disturbance in calcium and magnesium homeostasis.

Smart-detection approach for protein residues to evaluate the cleaning efficacy of reusable medical devices

BACKGROUND

Healthcare-associated infections are challenging problems to eradicate. In practice, infection prevention and control regarding the effective cleaning of reusable medical devices is performed. However, real-time monitoring of potentially contaminated devices is hindered by the complex, costly investigations and the time required.

AIM

To develop an inexpensive approach providing high-sensitivity, rapid, and low-cost protein residue determination on medical devices.

METHODS

Colourimetric reactions for protein were modified and downscaled to produce a colour product on the moving drop platform and to operate combined with our custom-built smartphone application in order to evaluate and save protein contamination data. The intensity of a product colour was detected by photographing with a smartphone camera and was proportional to the protein concentration in the linear range of 5-20 μg/mL. The protein content was processed on a custom-built smartphone application, namely PromoveCheck.

FINDINGS

The proposed procedure was highly sensitive, yielding limits of detection and limits of quantification, at 0.03 and 0.10 μg based on the Bradford reaction. It was applied to reusable medical devices, showing no significant differences from the spectrophotometric method and a correlation with the o-phthaldialdehyde method (P<0.05).

CONCLUSION

This approach demonstrates low cost, sensitivity, efficiency and traceability for investigating reusable medical device cleanliness. The PromoveCheck app can report and acquire protein content that can be used for traceability and alerts concerning questionable or discovered contaminant devices, improving the quality management of the Central Sterile Supply Department.

The colorful world of sulfonephthaleins: Current applications in analytical chemistry for "old but gold" molecules

Sulfonephthaleins represent one of the most common and widely employed reactive dyes in analytical chemistry, thanks to their stability, low-cost, well-visible colors, reactivity and possibilities of chemical modification. Despite being first proposed in 1916, nowadays, these molecules play a fundamental role in biological and medical applications, environmental analyses, food quality monitoring and other fields, with a particular focus on low-cost and disposable devices or methods for practical applications. Since up to our knowledge, no reviews or book chapters focused explicitly on sulfonephthaleins have ever been published, in this review, we will briefly describe sulfonephthaleins history, their acid-base properties will be discussed, and the most recent applications in different fields will be presented, focusing on the last ten years literature (2014-2023). Finally, safety and environmental issues will be briefly discussed, despite being quite controversial.

Paper microzone assay embedded on a 3D printed support for colorimetric quantification of proteins in different biological and food samples

This study describes the development of a paper microzone colorimetric assay embedded on a 3D printed support for quantifying total protein content in different biological matrices and foods. The aim was to develop an accurate and reliable method, ensuring at the same time the possibility of customizability, facility of use, wide applicability, and reduced analysis for both time and costs. The device consists of a 3D printed thermoplastic polyurethane support housing the detection substrate (GF/F glass microfiber). The bromophenol blue (BPB) assay was optimized in this substrate to quantify total protein content. The analytical performance, assessed through image analysis, indicated that the hue factor of the HSV colour space represents the best analytical signal (r² > 0.98%). The optimized assay ensures a sufficiently low limit of detection (0.05 mg mL^-1), and an accuracy between 92% and 95%. The bioanalytical feasibility was demonstrated through total protein concentration measurement in different biological matrices (bee venom and mouse brain tissue), and foods (soya milk, cow's milk and protein supplements). The obtained values showed a strong agreement with those derived from a standard spectrophotometric analysis. Overall, the paper microzone BPB assay may represent an important contribution to protein quantification technology and could significantly impact many areas, such as quality control analysis and pre-clinical laboratory analysis.

Paper-based optical sensors paired with smartphones for biomedical analysis

The traditional analytical methods used for biomedical analysis are expensive and not easy to handle and require sophisticated instruments, thus their application is limited in resource-limited settings. Due to their portability, low cost, and ability to be applied to different analytical techniques, paper-based analytical devices are becoming valuable tools for biomedical analysis. The integration of smartphones into analytical devices has provided the ability to build portable, cost-effective, straightforward analytical devices for biomedical analysis and mobile health. The key aim of this review is to emphasize the recent applications of PADs combined with a smartphone for the optical analysis of biomedical species. We started this review by highlighting the type of papers and their modifications with different materials to prepare the PADs. After that, this review presents various detection methods including colorimetry, fluorescence, and luminescence where the smartphone is used for read-out. In the end, we provided the recent applications of the analysis of different biomedical compounds such as cancer and cardiovascular biomarkers, metal ions, glucose, viruses, etc. We believe that the present review will attract a wide scientific community in the areas of analytical chemistry, sensors, and clinical testing.