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Xylans' unique properties make it attractive for a variety of industries, including paper, food, and biochemical production. While for some applications the preservation of its natural structure is crucial, for others the degradation into monosaccharides is essential. For the complete breakdown, the use of several enzymes is required, due to its structural complexity. In fact, the specificity of enzymatically-catalyzed reactions is guided by the surface, limiting or regulating accessibility and serving structurally encoded input guiding the actions of the enzymes. Here, we investigate enzymes at surfaces rich in xylan using surface plasmon resonance spectroscopy. The influence of diffusion and changes in substrate morphology is studied via enzyme surface kinetics simulations, yielding reaction rates and constants. We propose kinetic models, which can be applied to the degradation of multilayer biopolymer films. The most advanced model was verified by its successful application to the degradation of a thin film of polyhydroxybutyrate treated with a polyhydroxybutyrate-depolymerase. The herein derived models can be employed to quantify the degradation kinetics of various enzymes on biopolymers in heterogeneous environments, often prevalent in industrial processes. The identification of key factors influencing reaction rates such as inhibition will contribute to the quantification of intricate dynamics in complex systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

An individual nanoparticle-based plasmonic nanotechnology was used for real-time monitoring of lectin-sugar interactions, which could be designed as novel plasmonic nanobiosensors for the detection of trace concanavalin A (ConA) with high sensitivity and selectivity. The localized surface plasmon resonance (LSPR) spectra of Au@Ag nanocubes (NCs) are linearly shifted to a long wavelength with an increasing concentration of ConA. In fact, each Au@Ag NC can act as a nanobiosensor for the quantified detection of trace ConA, which enables the miniaturization of the biosensor system to nanoscale. Furthermore, the results demonstrated the perfect biosensing ability with the dual channel of dark-field microscopy images and LSPR spectra. We expect that this nanobiosensor system can provide an alternative important method for monitoring the specific binding of lectin-sugar at a single nanoparticle surface.

Modern techniques for quantifying blood group antibody-antigen interactions are very limited, especially for weaker interactions which result from low antigen expression and/or partial expression of the antigen structure. Surface plasmon resonance (SPR) detection is often used to monitor and quantify bio-interactions. Previously, a regenerable, multi-fucntional platform for quantitative RBC phenotyping of normal antigen expression using SPR detection was reported. However, detection of weaker variants were not explored. Here, this sensitivity study used anti-human IgG antibodies immobilized to a gold sensor surface to two clinically important types of weaker D variants using SPR; weak D and partial D. Positive pre-sensitised cells bind to the anti-human IgG monolayer, and the response unit (RU) is reported (>100 RU). Unbound negative cells are directly eluted (<100 RU). Weak D cells were detected between a range of 180-580 RU, due to a lower expression of antigens. Partial D cells, category D VI, were also positively identified (352-1147 RU), similar to that of normal D antigens. The detection of two classes of weaker D variants was achieved for the first time using this fully regenerable SPR platform, opening up a new avenue to replace the current subjective and arbitrary methods for quantifying blood group antibody-antigen interactions.

The most widely known blood groups, ABO and RhD, have been extensively observed as having strong antibody-antigen interactions during blood typing. However, not all interactions show the same binding affinity. The Duffy blood group system, where Fy a and Fy b antigens are the most clinically significant, are only available with an IgG antibody structure, and display weak binding interactions. While current blood typing techniques are well established, methods for quantifying the binding strength are more limited. Surface Plasmon Resonance (SPR) provides avenues for developing more robust detection methods, and serve as a sensitive quantification technique by itself. This study tested SPR for the detection of weaker antibody-antigen interactions using the Duffy blood groups, Fy a and Fy b , as a model. This study shows a minimum threshold of antibody concentration is required for successful detection. Some instances of detection were successful using concentrated commercial anti-Fy a and anti-Fy b solution during the incubation stage. However, these results were not fully reproducible. We found that a significant dissociation of the Duffy antigen-antibody complex occurs over time. A combination of factors affects the detection of the Duffy antigens using SPR; these include antibody concentration, antigen expression, and antigen structure. This results in weak, unstable and reversible antibody-antigen interactions which are currently limiting accurate and reproducible detection by SPR. Despite these issues, detection of Duffy antigens Fy a and Fy b was demonstrated using SPR; however, further development is required for SPR to become a robust clinical blood typing technique.

Promoted by the localized surface plasmon resonance nanotechnology, a simple and sensitive plasmonic aptamer nanosensor (nanoaptasensor) on an individual Au@Ag core-shell nanocube (Au@Ag NC) has been proposed for real-time monitoring of the formation process of G-quadruplex structures and label-free analysis of potassium ions (K(+) ). In particular, the analysis of the thermodynamic parameters indicates that there are two types of binding states accompanied with a remarkable change of free energy (ΔG) in the sequential folding process of telomere DNA sequence. This nanoaptasensor has raised promising applications in monitoring the dynamic process of the structural switch of the G-quadruplex., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The accurate and reliable typing of blood groups is essential prior to blood transfusion. While current blood typing methods are well established, results are subjective and heavily reliant on analysis by trained personnel. Techniques for quantifying blood group antibody-antigen interactions are also very limited. Many biosensing systems rely on surface plasmon resonance (SPR) detection to quantify biomolecular interactions. While SPR has been widely used for characterizing antibody-antigen interactions, measuring antibody interactions with whole cells is significantly less common. Previous studies utilized SPR for blood group antigen detection, however, showed poor regeneration causing loss of functionality after a single use. In this study, a fully regenerable, multi-functional platform for quantitative blood group typing via SPR detection is achieved by immobilizing anti-human IgG antibody to the sensor surface, which binds to the Fc region of human IgG antibodies. The surface becomes an interchangeable platform capable of quantifying the blood group interactions between red blood cells (RBCs) and IgG antibodies. As with indirect antiglobulin tests (IAT), which use IgG antibodies for detection, IgG antibodies are initially incubated with RBCs. This facilitates binding to the immobilized monolayer and allows for quantitative blood group detection. Using the D-antigen as an example, a clear distinction between positive (>500 RU) and negative (<100 RU) RBCs is achieved using anti-D IgG. Complete regeneration of the anti-human IgG surface is also successful, showing negligible degradation of the surface after more than 100 regenerations. This novel approach is validated with human-sourced whole blood samples to demonstrate an interesting alternative for quantitative blood grouping using SPR analysis., (Crown Copyright © 2015. Published by Elsevier B.V. All rights reserved.)