Tyrosinase is a multi-copper enzyme which is widely distributed in different organisms and plays an important role in the melanogenesis and enzymatic browning. Therefore, its inhibitors can be attractive in cosmetics and medicinal industries as depigmentation agents and also in food and agriculture industries as antibrowning compounds. For this purpose, many natural, semi-synthetic and synthetic inhibitors have been developed by different screening methods to date. This review has focused on the tyrosinase inhibitors discovered from all sources and biochemically characterised in the last four decades.

https://northumbria-test.eprints-hosting.org/id/document/268389

A comprehensive review on tyrosinase inhibitors.

Abstract Functionalised hexagonal mesoporous SBA-15-type molecular sieves with pore sizes in the range 51–56 A have been prepared using non-ionic block copolymers and used for immobilisation of the enzyme trypsin. Thiol, chloride, amine, and carboxylic acid functional groups were attached by siloxypropane tethers to the siliceous surface of SBA-15 via two methods, post-synthesis grafting and in situ synthesis. Phenylsiloxane groups were also incorporated using these two methods. The resulting solids were rendered porous and used to immobilise trypsin, giving variable but in general higher retention of the enzyme molecules than was observed on unfunctionalised, purely siliceous SBA-15. The resulting supported enzyme catalysts were shown to be active and stable catalysts for the hydrolysis of N -α-benzoyl-DL-arginine-4-nitroanilide (BAPNA). The solids prepared by supporting the enzyme on thiol-functionalised SBA-15 prepared by in situ synthesis were found to be the most promising. Trypsin supported on thiol-functionalised SBA-15 was shown to be recyclable.

Enzyme Immobilization Using SBA15 Mesoporous Molecular Sieves with Functionalised Surfaces

Magnetic nanoparticles as versatile carriers for enzymes immobilization: A review.

Nanomaterials, in addition to their small size, possess unique physicochemical properties that differ from bulk materials, making them ideal for a host of novel applications. Magnetic nanoparticles (MNPs) are one important class of nanomaterials that have been widely studied for their potential applications in nanomedicine. Due to the fact that MNPs can be detected and manipulated by remote magnetic fields, it opens a wide opportunity for them to be used in vivo. Nowadays, MNPs have been used for diverse applications including magnetic biosensing (diagnostics), magnetic imaging, magnetic separation, drug and gene delivery, and hyperthermia therapy, etc. Specifically, we reviewed some emerging techniques in magnetic diagnostics such as magnetoresistive (MR) and micro-Hall (μHall) biosensors, as well as the magnetic particle spectroscopy, magnetic relaxation switching and surface enhanced Raman spectroscopy (SERS)-based bioassays. Recent advances in applying MNPs as contrast agents in magnetic resonance imaging and as tracer materials in magnetic particle imaging are reviewed. In addition, the development of high magnetic moment MNPs with proper surface functionalization has progressed exponentially over the past decade. To this end, different MNP synthesis approaches and surface coating strategies are reviewed and the biocompatibility and toxicity of surface functionalized MNP nanocomposites are also discussed. Herein, we are aiming to provide a comprehensive assessment of the state-of-the-art biological and biomedical applications of MNPs. This review is not only to provide in-depth insights into the different synthesis, biofunctionalization, biosensing, imaging, and therapy methods but also to give an overview of limitations and possibilities of each technology.

https://iopscience.iop.org/article/10.1088/1361-6528/ab4241/pdf

Magnetic nanoparticles in nanomedicine: a review of recent advances.

Compared with free enzymes, immobilized enzymes are more robust and resistant to environmental changes. In addition, with enhanced stability, immobilized enzymes can be separated from the reaction mixture and used for repeated cycles. These advantages prompt their applications in various fields. This review outlines the existing methods and easy separated support materials for enzymes immobilization. After a brief introduction on the immobilized enzyme, the immobilization methods of adsorption, entrapment, covalent attachment and cross-linking are discussed. The emphasis is given on the easy separated support materials of magnetic nanoparticles (MNPs), membranes and capillary columns. An outlook on the immobilized enzyme is given at last.

Advances on methods and easy separated support materials for enzymes immobilization

Screening of enzyme inhibitors from traditional Chinese medicine by magnetic immobilized α-glucosidase coupled with capillary electrophoresis

Tyrosinase immobilization on aminated magnetic nanoparticles by physical adsorption combined with covalent crosslinking with improved catalytic activity, reusability and storage stability.

α-Glucosidase immobilization on chitosan-enriched magnetic composites for enzyme inhibitors screening

In this work, a facile protocol for preparing an online immobilized α-glucosidase microreactor was described, and also the enzyme kinetics and inhibition kinetics of such an immobilized enzyme were studied. In this procedure, α-glucosidase was immobilized on the inner wall of the capillary treated with 3-aminopropyltriethoxysilane (3-APTES) and the homobifunctional linker glutaraldehyde (GA). With cross-linking technology, the immobilized α-glucosidase microreactor was fabricated. As the key point for studying the enzyme kinetics and inhibition kinetics of the immobilized α-glucosidase with the developed microreactor, pressure was applied as the driving force to push the reaction mixture to the detection window, and the detection wavelength was set to 405 nm at which only the formed p-nitrophenol (pNP) could be detected. More importantly, with such a detection wavelength it is unnecessary to separate the substrate from the reaction mixture by applying the alkaline inactivating background electrolyte (BGE, borate buffer, pH ≥ 9.0) which is favorable for the separation. So the incubation buffer (phosphate buffer, pH 7.0) could be used as the running buffer making the online study of the enzyme kinetics and inhibition kinetics of immobilized α-glucosidase come true. The inhibition assay was performed by using acarbose as a model inhibitor, and under the optimized conditions, the Michaelis–Menten constant (Km), inhibition constant (Ki), and half-maximal inhibitory concentration (IC50) for the immobilized α-glucosidase were determined as 0.43 mM, 30.65 μM and 99.48 μM, respectively. This study indicates, for the first time, that the immobilized α-glucosidase microreactor could be used for studying the enzyme kinetics and inhibition kinetics online.

Dong-Mei Liu

Papers

Advances on methods and easy separated support materials for enzymes immobilization

Screening of enzyme inhibitors from traditional Chinese medicine by magnetic immobilized α-glucosidase coupled with capillary electrophoresis

Tyrosinase immobilization on aminated magnetic nanoparticles by physical adsorption combined with covalent crosslinking with improved catalytic activity, reusability and storage stability.

α-Glucosidase immobilization on chitosan-enriched magnetic composites for enzyme inhibitors screening

An online immobilized α-glucosidase microreactor for enzyme kinetics and inhibition assays