Lysozyme as a flocculant-inducing agent improving the silica removal from aqueous solutions - A turbidimetric study

A Novel Cysteine-Functionalized MxOy Material as Support for Laccase Immobilization and a Potential Application in Decolorization of Alizarin Red S

Immobilization process improves the enzyme properties, like stability, activity, selectivity or specificity. In the study, a novel cysteine-functionalized MxOy (ZrO2, SiO2) material was used as a support for the immobilization of laccase from Trametes versicolor. The proposed matrix was prepared using a simple sol-gel method. The cysteine was introduced during the synthesis of a sample. Additionally, the obtained supports were modified with glutaraldehyde. The basic properties of the prepared cysteine functionalized ZrO2 and SiO2 were determined using spectroscopic, thermal, porous, electrostatic and elemental analysis. Furthermore, the obtained biocatalytic systems were used as catalysts in the oxidation of sulfonic acid. Catalytic and kinetic parameters were determined based on the proposed model reaction. Next, laccase immobilized on ZrO2- and SiO2-based materials were, for the first time, utilized in the decolorization of Alizarin Red S. In that process, the influence of duration, pH and temperature on the efficiency of decolorization was evaluated. The results show that the proposed biocatalytic systems offer good specific activity (ca. 19 U/mg) and activity retention (ca. 77%). Importantly, they can be successfully used in the decolorization of Alizarin Red S with high efficiency (above 95%).

An antifouling interface integrated with HRP-based amplification to achieve a highly sensitive electrochemical aptasensor for lysozyme detection

We report here a highly sensitive sandwich type electrochemical aptasensor for lysozyme (lys) detection by the integration of an antifouling interface with HRP-based signal amplification. The biosensing interface with antifouling ability is designed, consisting of a lys-binding aptamer (LBA), dithiothreitol (DTT) and mercaptohexanol (MCH). When lys is captured by the immobilized LBA due to the specific recognition of the aptamer, gold nanoparticles (AuNPs) functionalized with HRP and LBA (HRP-AuNP-LBA) are further conjugated to the surface-bound lys, forming a sandwich assay format. HRP catalyzes the chemical oxidation of hydroquinone (HQ) by hydrogen peroxide (H₂O₂) to produce benzoquinone (BQ) which results in a large electrochemical reduction signal of BQ. Therefore, this reduction signal measured by differential pulse voltammetry (DPV) is used to detect lys. The catalytic behavior of HRP toward the reaction between HQ and H₂O₂, together with the high loading of HRP on AuNPs, remarkably amplifies the signal. A linear relationship between the DPV response and the logarithm of lys concentration from 0.01 pg mL^-1 to 10⁵ pg mL^-1 with a detection limit of 0.003 pg mL^-1 (S/N = 3) is obtained. The proposed biosensing platform combines antifouling ability and signal amplification, resulting in high sensitivity, providing an effective way for ultrasensitive assay of protein biomarkers in complex media.