Analytical biochemistry最新文献

In recent years, important efforts have been made to elucidate the mechanisms of epigenetic regulation, and one of the most studied epigenetic modifications was DNA methylation/demethylation. In this study, the voltammetric behaviour of 5-hydroxymethylcytosine was studied in the pH range of 2.00–11.00 using pencil graphite electrodes by differential pulse and square wave voltammetry. The effect of buffer solutions, scan rate, square wave voltammetry parameters, and stripping conditions on the voltammetric responses of 5-hydroxymethylcytosine were performed. The electrochemical oxidation process of 5-hydroxymethylcytosine on the pencil graphite electrode was realized under adsorption control. In human urine, by square wave stripping voltammetry, 5-hydroxymethylcytosine was quantified in a concentration range of 1.00 × 10⁻⁵ M-2.00 × 10⁻⁴ M. The proposed method was tested in the presence of cytosine in human urine. The recovery value of 5-hydroxymethylcytosine was found to be 99.57 %.

The integration of fiber optics and plasmonic sensors is promising to improve the practical usability over conventional bulky sensors and systems. To achieve high sensitivity, it typically requires fabrication of well-defined plasmonic nanostructures on optical fibers, which greatly increases the cost and complexity of the sensors. Here, we present a fiber-optic sensor system by using chemical absorption of gold nanoparticles and a replaceable configuration. By functioning gold nanoparticles with aptamers or antibodies, we demonstrate the applications in chemical sensing using two different modes. Measuring shift in resonance wavelength enables the Pb²⁺ detection with a high linearity and a limit of detection of 0.097 nM, and measuring absorption peak amplitude enables the detection of E. coli in urinary tract infection with a dynamic range between 10³ to 10⁸ CFU/mL. The high sensitivity, simple fabrication and disposability of this sensing approach could pave the way for point-of-care testing with fiber-optic plasmonic sensors.

Our study delved into the intricate dynamics of antifungal susceptibility testing for Candida spp., employing a Design of Experiments approach. We systematically investigated the influence of pH, temperature, inoculum size, and glucose concentration on both growth patterns and inhibitory concentrations of Candida spp. Our findings underscore the nuanced interplay between these factors, revealing significant impacts on susceptibility outcomes. Notably, even minor adjustments in these parameters yielded substantial variations in growth and inhibitory concentrations, underscoring the critical importance of meticulous control over growth conditions in antifungal susceptibility testing protocols. Each Candida isolates exhibited unique susceptibility profiles, necessitating tailored culture conditions for accurate testing. Our study sheds light on the variability inherent in Candida spp. growth patterns and emphasizes the need for standardized protocols to ensure consistency across laboratories. By leveraging the design of experiments, our research provides a systematic framework for unraveling the complexities of antifungal susceptibility testing, offering valuable insights for optimizing testing protocols and informing clinical decision-making in antifungal treatment. These findings represent a significant step towards enhancing the efficacy and reliability of antifungal susceptibility testing in clinical practice.

A number of drugs based on recombinant erythropoietin contain human serum albumin as an auxiliary component. The presence of this protein hinders the proper control of the drug quality in accordance with the requirements of regulating agencies. We propose the novel method for separation of recombinant erythropoietin (epoetin beta) and human serum albumin. It is based on the subsequent use of hydrophobic sorbent and anion exchange resin placed in gravity flow columns (without the use of spin-columns). The proposed approach makes it possible to concentrate and purify the preparations containing the epoetin beta both at high and at minimal concentrations (the ratio of the amount of albumin and erythropoietin in the used preparations can reach 125:1). The average yield of epoetin beta after the use of hydrophobic sorbent and anion exchange resin was 75 % and 97 %, respectively. It was shown that the determined conditions of sample preparation had no affect on the content of the epoetin beta in the product.

Extensive investigations are being conducted on gold nanoparticles focusing on their applications in biosensors, laser phototherapy, targeted drug delivery and bioimaging utilizing advanced detection techniques. In this work, an electrochemical sensor was developed based on graphite carbon nitride supported gold nanoparticles. Carbon nitride supported gold nanoparticles (Au–CN) was synthesized by applying a deposition-precipitation route followed by a chemical reduction technique. The composite system was characterized by X-ray diffraction and X-ray photo electron spectroscopy methods. Electron microscopy analysis confirmed the formation of gold nanoparticles within the size range of 5–15 nm on the carbon nitride support. Carbon nitride supported gold based sensor was employed for the electrochemical detection of iodide ion and l-cysteine. The limit of detection and sensitivity of the sensor was attained 8.9 μM and 0.96 μAμM⁻¹cm⁻², respectively, for iodide ion, while 0.48 μM and 5.8 μAμM⁻¹cm⁻², respectively, was achieved for the recognition of cysteine. Furthermore, a paper-based electrochemical device was developed using the Au–CN hybrid system that exhibited promising results in detecting iodide ions, highlighting its potential for economic and portable device applications.