Analysis of complexes of metabolites with europium tetracycline using capillary electrophoresis coupled with laser-induced luminescence detection

Simple and rapid detection of tyrosinase activity with the adjustable light scattering properties of CoOOH nanoflakes

Tyrosinase (TYR), as an important biological enzyme, has been widely used in synthetic biology, medical hairdressing, environmental detection, biological sensors, and other fields. In clinical practice, tyrosinase activity is an important indicator for detecting melanoma. Therefore, the detection of tyrosinase activity is of great importance. Based on the polyphenol oxidase activity of tyrosinase, a simple and rapid detection method was proposed based on the adjustable light scattering properties of cobalt hydroxyl oxide nanoflakes (CoOOH NFs). It was found that the amount and size of CoOOH NFs decreased due to the redox reaction mediated by catechol (CC), resulting in a lower light scattering signal of CoOOH NFs. However, in the presence of tyrosinase, catechol was oxidized to a quinone structure, resulting in the reduced decomposition of CoOOH NFs and recovered light scattering signal, which was developed for the quantitative detection of tyrosinase activity. It was found that in the range of 10-400 U/L, the light scattering intensity was correlated linearly with tyrosinase activity, and the limit of detection was 6.71 U/L (3σ/k). To verify the feasibility of the proposed method in clinical samples, the spiked recovery experiments were carried out with human serum samples, which showed recovery rates between 93.0% and 104.6%, suggesting the high accuracy. The proposed assay provides a simple and rapid method for detection of a natural enzyme based on the adjustable light scattering properties of CoOOH nanoflakes, which lays the foundation for the development of various enzyme sensing applications in the future.

Size-dependent light scattering of CoOOH nanoflakes for convenient and sensitive detection of alkaline phosphatase in human serum

As a natural enzyme, alkaline phosphatase (ALP) plays an essential role in clinicopathological examinations and biomedical research, and is capable of hydrolyzing the phosphate group of l-ascorbic acid-2-phosphate (AAP) to yield l-ascorbic acid (L-AA). L-AA reduced cobalt oxyhydroxide (CoOOH) nanoflakes to Co²⁺ , leading to a smaller size and weaker light scattering, which could be monitored by electron microscopic images and optical spectra. The indirect detection of ALP was achieved by the reduced light scattering signal of CoOOH nanoflakes. Under optimal conditions, the decrease in scattering intensity was proportional to the ALP concentration over the range 0.1-160 U/L and the detection limit was 0.034 U/L (3σ/k). Compared with other assays, this proposed light scattering method was more convenient and economic for ALP sensing. The method was successfully applied to ALP analysis in human serum samples, and was similar to the results obtained by commercial kits.

Citrate analysis using capillary electrophoresis and complexation with Eu3+-tetracycline

A sensitive assay for citrate was developed. Citrate was incubated with 50 μM Eu³⁺-tetracycline and the complex separated using capillary electrophoresis utilizing post-column laser-induced luminescence detection in a sheath flow cuvette. Signal was linear with citrate concentration from 10 μM to 200 nM. Injection volumes were 320 pL. For the 200 nM sample, this corresponds to the injection of 64 amoles of citrate. Separation time was < 90 s with a total run time of 5 min. As an application the method was used to analyze citrate in agricultural and medicinal products. The method was also used to develop an assay for the enzyme citrate synthase.