Construction of a D-amino acid oxidase reactor based on magnetic nanoparticles modified by a reactive polymer and its application in screening enzyme inhibitors

Green synthesis of iron nanoparticles: Sources and multifarious biotechnological applications

Green synthesis of iron nanoparticles is a highly fascinating research area and has gained importance due to reliable, sustainable and ecofriendly protocol for synthesizing nanoparticles, along with the easy availability of plant materials and their pharmacological significance. As an alternate to physical and chemical synthesis, the biological materials, like microorganisms and plants are considered to be less costly and environment-friendly. Iron nanoparticles with diverse morphology and size have been synthesized using biological extracts. Microbial (bacteria, fungi, algae etc.) and plant extracts have been employed in green synthesis of iron nanoparticles due to the presence of various metabolites and biomolecules. Physical and biochemical properties of biologically synthesized iron nanoparticles are superior to that are synthesized using physical and chemical agents. Iron nanoparticles have magnetic property with thermal and electrical conductivity. Iron nanoparticles below a certain size (generally 10-20 nm), can exhibit a unique form of magnetism called superparamagnetism. They are non-toxic and highly dispersible with targeted delivery, which are suitable for efficient drug delivery to the target. Green synthesized iron nanoparticles have been explored for multifarious biotechnological applications. These iron nanoparticles exhibited antimicrobial and anticancerous properties. Iron nanoparticles adversely affect the cell viability, division and metabolic activity. Iron nanoparticles have been used in the purification and immobilization of various enzymes/proteins. Iron nanoparticles have shown potential in bioremediation of various organic and inorganic pollutants. This review describes various biological sources used in the green synthesis of iron nanoparticles and their potential applications in biotechnology, diagnostics and mitigation of environmental pollutants.

Catechol-tetraethylenepentamine co-deposition modified cellulose filter paper for α-glucosidase immobilization and inhibitor screening from traditional Chinese medicine

Cellulose filter paper (CFP) is expected to be an ideal carrier for enzyme immobilization due to its sustainability and biocompatibility. However, the interaction between the carrier and enzyme might change the spatial conformation of the enzyme and its microenvironment, and thus the flexibility of the enzyme molecule or the transport of the substrate to the active site would be hampered. In this work, a two-component system of catechol and tetraethylene pentamine was used to replace dopamine, and a polydopamine-like composite layer was deposited on the surface of CFP to introduce amino groups, which was similar to the self-polymerization-adhesion behavior of dopamine. Using polyethylene glycol diglycidyl ether with flexible spacer arms as the cross-linking agent, α-glucosidase was covalently bonded to amino-modified CFP through an epoxy ring-opening reaction. The immobilized α-glucosidase exhibited greater tolerance to pH and high temperature. After 10 repeated uses, the immobilized α-glucosidase maintained relatively high enzyme activity. Its kinetic behavior was investigated to illustrate the reliability for enzyme inhibitor screening. Finally, a screening method combining an immobilized enzyme and capillary electrophoresis analysis was proposed and applied to screening inhibitors from 11 kinds of traditional Chinese medicines, among which Chebulae Fructus, Phyllanthi Fructus and Terminaliae Relliricae Fructus exhibited strong enzyme inhibitory activities.

An overview and bibliometric analysis on the colorectal cancer therapy by magnetic functionalized nanoparticles for the responsive and targeted drug delivery

With the growing demands for personalized medicine and medical devices, nanomedicine is a modern scientific field, and research continues to apply nanomaterials for therapeutic and damaged tissue diagnosis. In this regard, substantial progress has been made in synthesizing magnetic nanoparticles with desired sizes, chemical composition, morphologies, and surface chemistry. Among these materials, nanomagnetic iron oxides have demonstrated promise as unique drug delivery carriers due to cancer treatment. This carrier could lead to responsive properties to a specific trigger, including heat, pH, alternative magnetic field, or even enzymes, through functionalization and coating of magnetic nanoparticles, along with biocompatibility, good chemical stability, easy functionalization, simple processing, and ability to localize to the tumor site with the assistance of external magnetic field. Current studies have focused on magnetic nanoparticles' utilities in cancer therapy, especially for colorectal cancer. Additionally, a bibliometric investigation was performed on the public trends in the field of the magnetic nanoparticle to drug delivery and anticancer, which represented progressing applications of these carriers in the multidisciplinary zones with a general view on future research and identified potential opportunities and challenges. Furthermore, we outline the current challenges and forthcoming research perspective for high performance and fostering advanced MNPs in colorectal cancer treatment.

Magnetic particles for enzyme immobilization: A versatile support for ligand screening

Enzyme inhibitors represent a substantial fraction of all small molecules currently in clinical use. Therefore, the early stage of drug-discovery process and development efforts are focused on the identification of new enzyme inhibitors through screening assays. The use of immobilized enzymes on solid supports to probe ligand-enzyme interactions have been employed with success not only to identify and characterize but also to isolate new ligands from complex mixtures. Between the available solid supports, magnetic particles have emerged as a promising support for enzyme immobilization due to the high superficial area, easy separation from the reaction medium and versatility. Particularly, the ligand fishing assay has been employed as a very useful tool to rapidly isolate bioactive compounds from complex mixtures, and hence the use of magnetic particles for enzyme immobilization has been widespread. Thus, this review provides a critical overview of the screening assays using immobilized enzymes on magnetic particles between 2006 and 2021.

Fabrication of a porous polymer membrane enzyme reactor and its enzymatic kinetics study in an artificial kidney model

A porous polymer membrane-based d-amino acid oxidase (DAAO) reactor was developed that mimicked enzymatic activity in a renal ischemia model. Using glycidyl methacrylate as a biocompatible reactive monomer, poly(styrene-glycidyl methacrylate) was synthesized via a reversible addition fragment chain transfer polymerization technique. The prepared porous polymer membrane was used as a support to effectively immobilize DAAO. Compared to DAAO modified on nonporous polymer membrane and free DAAO in solution, the constructed porous polymer membrane-based DAAO enzyme reactor displayed 3-fold and 19-fold increase in enzymolysis efficiency, respectively. In addition, a chiral ligand exchange capillary electrophoresis system for DAAO was used to study DAAO enzymatic kinetics with d,l-methionine as the substrate. The proposed porous polymer membrane-based enzyme reactor showed excellent performance both on reproducibility and stability. Moreover, the enzyme reactor was successfully applied to mimic DAAO activity in a renal ischemia model. These results demonstrated that the enzyme could be efficiently immobilized onto a porous polymer membrane as an enzyme reactor and has great potential in mimicking the enzymatic activity in kidney.

Recent applications of immobilized biomaterials in herbal analysis

Immobilization of biomaterials developed rapidly due to the great promise in improving their stability, activity and even selectivity. In this review, the immobilization strategies of biomaterials, including physical adsorption, encapsulation, covalent attachment, cross-linking and affinity linkage, were briefly introduced. Then, the major emphasis was focused on the reported various types of immobilized biomaterials, including proteins, enzymes, cell membrane and artificial membrane, living cells, carbohydrates and bacteria, used in the herbal analysis for bioactive compound screening, drug-target interaction evaluation and chiral separation. In addition, a series of carrier materials applied in biomaterials immobilization, such as magnetic nanoparticles, metal-organic frameworks, silica capillary column, cellulose filter paper, cell membrane chromatography, immobilized artificial membrane chromatography and hollow fiber, were also discussed. Perspectives on further applications of immobilized biomaterials in herbal analysis were finally presented.

Simultaneous synthesis of l-DOPA and oxidation of d-amino acid by specific coupling of a peroxidase to d-amino acid oxidase

3,4 Dihydroxy phenyl l-alanine (L-DOPA) is the gold standard Parkinson's disease therapy. A heme-dependent peroxidase (HDP) catalyzes the ortho-hydroxylation of l-tyrosine to l-DOPA using H₂O₂ as the co-substrate. d-amino acid oxidase (DAAO) catalyzes the oxidative deamination of d-amino acids (e.g. d-alanine), and H₂O₂ is evolved. However, both the enzymes DAAO and HDP can be inactivated by H₂O₂ during the catalysis. In situ generation and utilization of H₂O₂ can siginificatly reduce the inactivation by H₂O₂. HDP exists as a monomer and DAAO is a dimeric enzyme. Herein, the C-terminus of HDP was specifically ligated to the N-terminus of the DAAO subunit with native peptide through the in vivo monomer-subunit splicing. In the splicing product HDP&DAAO, HDP is close to the DAAO subunit at a molecular distance, and the transfer of H₂O₂ from DAAO to HDP is facilitated. In addition, HDP&DAAO exhibited a higher stability than HDP. Kinetics analysis showed that both the substrates l-tyrosine and d-alanine obey the Michaelis-Menten kinetics. For the deamination of d-alanine, the catalytic efficiency of HDP&DAAO is 3.05 times that of DAAO. For the sybthesis of l-DOPA from l-tyrosine, the catalytic efficiency of HDP&DAAO is 1.58 times that of HDP. Furthermore, HDP&DAAO was encapsulated within a Znic-based coordination polymer (Zn-CP). The morphorogy of HDP&DAAO/Zn-CP can be regulated by the enzyme concentration, the catalytic efficiency of the conjugates was found to be dependent on the morphorogy. The conjugates HDP&DAAO/Zn-CP exhibited a higher catalytic efficiency than free HDP&DAAO.

Advances in enzyme substrate analysis with capillary electrophoresis

Capillary electrophoresis provides a rapid, cost-effective platform for enzyme and substrate characterization. The high resolution achievable by capillary electrophoresis enables the analysis of substrates and products that are indistinguishable by spectroscopic techniques alone, while the small volume requirement enables analysis of enzymes or substrates in limited supply. Furthermore, the compatibility of capillary electrophoresis with various detectors makes it suitable for KM determinations ranging from nanomolar to millimolar concentrations. Capillary electrophoresis fundamentals are discussed with an emphasis on the separation mechanisms relevant to evaluate sets of substrate and product that are charged, neutral, and even chiral. The basic principles of Michaelis-Menten determinations are reviewed and the process of translating capillary electrophoresis electropherograms into a Michaelis-Menten curve is outlined. The conditions that must be optimized in order to couple off-line and on-line enzyme reactions with capillary electrophoresis separations, such as incubation time, buffer pH and ionic strength, and temperature, are examined to provide insight into how the techniques can be best utilized. The application of capillary electrophoresis to quantify enzyme inhibition, in the form of KI or IC50 is detailed. The concept and implementation of the immobilized enzyme reactor is described as a means to increase enzyme stability and reusability, as well as a powerful tool for screening enzyme substrates and inhibitors. Emerging techniques focused on applying capillary electrophoresis as a rapid assay to obtain structural identification or sequence information about a substrate and in-line digestions of peptides and proteins coupled to mass spectrometry analyses are highlighted.

Recent advances in screening of enzymes inhibitors based on capillary electrophoresis

Capillary electrophoresis with many advantages plays an important role in pharmaceutical analysis and drug screening. This review gives an overview on the recent advances in the developments and applications of capillary electrophoresis in the field of enzyme inhibitor screening. The period covers 2013 to 2017. Both the pre-capillary enzyme assays and in-capillary enzyme assays which include electrophoretically mediated microanalysis (EMMA) and immobilized enzyme microreactor (IMER) are summarized in this article.

Magnetite Core-Shell Nanoparticles in Nondestructive Flaw Detection of Polymeric Materials

Nondestructive flaw detection in polymeric materials is important but difficult to achieve. In this research, the application of magnetite nanoparticles (MNPs) in nondestructive flaw detection is studied and realized, to the best of our knowledge, for the first time. Superparamagnetic and highly magnetic (up to 63 emu/g) magnetite core-shell nanoparticles are prepared by grafting bromo-end-group-functionalized poly(glycidyl methacrylate) (Br-PGMA) onto surface-modified Fe₃O₄ NPs. These Fe₃O₄-PGMA NPs are blended into bisphenol A diglycidylether (BADGE)-based epoxy to form homogeneously distributed magnetic epoxy nanocomposites (MENCs) after curing. The core Fe₃O₄ of the Fe₃O₄-PGMA NPs endows the MENCs with magnetic property, which is crucial for nondestructive flaw detection of the materials, while the shell PGMA promotes colloidal stability and prevents NP aggregation during curing. The eddy current testing (ET) technique is first applied to detect flaws in the MENCs. Through the brightness contrast of the ET image, surficial and subsurficial flaws in MENCs can be detected, even for MENCs with low content of Fe₃O₄-PGMA NPs (1 wt %). The incorporation of Fe₃O₄-PGMA NPs can be easily extended to other polymer and polymer-based composite systems and opens a new and very promising pathway toward MNP-based nondestructive flaw detection in polymeric materials.

Polydopamine Grafted Porous Graphene as Biocompatible Nanoreactor for Efficient Identification of Membrane Proteins

Functional nanomaterials, used as nanoreactors, have shown great advantages in a variety of applications in biomedical fields. Herein, we designed a novel nanoreactor system toward the application in membrane proteomics by using polydopamine-coated nanoporous graphene foams (NGFs-PD) prepared by a facile in situ oxidative polymerization. Taking advantage of the unique 3-D structure and surface functionalization, NGFs-PD can quickly adsorb a large amount of hydrophobic membrane proteins dissolved in sodium dodecyl sulfonate (SDS)/methanol and hydrophilic trypsin in aqueous solution, and then confine the proteolysis in the nanoscale domains to fasten the reaction rate. Therefore, the current nanoreactor system combines the multifunctions of highly efficient solubilization, immobilization, and proteolysis of membrane proteins. With the nanoreactor, digestion of standard membrane proteins can be finished in 10 min. 893 membrane proteins were identified from human glioma cells (U251). All these superiorities indicate that the biocompatible NGFs-PD nanoreactor system is of great promise to facilitate high-throughput membrane proteomic analysis.

Improving the sensitivity in chiral capillary electrophoresis

CE is known for being one of the most powerful analytical techniques when performing enantioseparations due to its numerous advantages such as excellent separation efficiency and extremely low solvents and reagents consumption, all of them derived from the capillary small dimensions. Moreover, it is worth highlighting that unlike in chromatographic techniques, in CE the chiral selector is generally within the separation medium instead of being attached to the separation column which makes the method optimization a more versatile task. Despite its numerous advantages, when using UV-Vis detection, CE lacks of sensitivity detection due to its short optical path length derived from the narrow separation capillary. This issue can be overcome by means of different approaches, either by sample treatment procedures or by in-capillary preconcentration techniques or even by employing detection systems more sensitive than UV-Vis, such as LIF or MS. The present review assembles the latest contributions regarding improvements of sensitivity in chiral CE published from June 2013 until May 2015, which follows the works included in a previous review reported by Sánchez-Hernández et al. [Electrophoresis 2014, 35, 12-27].

Poly(2-vinyl-4,4-dimethylazlactone)-functionalized magnetic nanoparticles as carriers for enzyme immobilization and its application

Fabrication of various efficient enzyme reactors has triggered increasing interests for its extensive applications in biological and clinical research. In this study, magnetic nanoparticles were functionalized by a biocompatible reactive polymer, poly(2-vinyl-4,4-dimethylazlactone), which was synthesized by reversible addition-fragmentation chain transfer polymerization. Then, the prepared polymer-modified magnetic nanoparticles were employed as favorable carriers for enzyme immobilization. l-Asparaginase was selected as the model enzyme to fabricate the enzyme reactor, and the prepared enzyme reactor exhibited high loading capacity of 318.0 μg mg(-1) magnetic nanoparticle. Interestingly, it has been observed that the enzymolysis efficiency increased slightly with the lengthened polymer chain, resulting from the increased immobilization amount of enzyme. Meanwhile, the immobilized enzyme could retain more than 95.7% activity after 10 repeated uses and maintain more than 72.6% activity after 10 weeks storage. Moreover, an extracorporeal shunt system was simulated to estimate the potential application capability of the prepared l-asparaginase reactor in acute lymphoblastic leukemia treatment.