Distribution of the Number of Polymer Chains Grafted on Nanoparticles Fabricated by Grafting-to and Grafting-from Procedures

Recent Advances in Applications of Oxidases and Peroxidases Polymer-Based Enzyme Biocatalysts in Sensing and Wastewater Treatment: A Review

Oxidase and peroxidase enzymes have attracted attention in various biotechnological industries due to their ease of synthesis, wide range of applications, and operation under mild conditions. Their applicability, however, is limited by their poor stability in harsher conditions and their non-reusability. As a result, several approaches such as enzyme engineering, medium engineering, and enzyme immobilization have been used to improve the enzyme properties. Several materials have been used as supports for these enzymes to increase their stability and reusability. This review focusses on the immobilization of oxidase and peroxidase enzymes on metal and metal oxide nanoparticle-polymer composite supports and the different methods used to achieve the immobilization. The application of the enzyme-metal/metal oxide-polymer biocatalysts in biosensing of hydrogen peroxide, glucose, pesticides, and herbicides as well as blood components such as cholesterol, urea, dopamine, and xanthine have been extensively reviewed. The application of the biocatalysts in wastewater treatment through degradation of dyes, pesticides, and other organic compounds has also been discussed.

Hybrid Polymer-Silica Nanostructured Materials for Environmental Remediation

Due to the ever-growing global population, it is necessary to develop highly effective processes that minimize the impact of human activities and consumption on the environment. The levels of organic and inorganic contaminants have rapidly increased in recent years, posing a threat to ecosystems. Removing these toxic pollutants from the environment is a challenging task that requires physical, chemical, and biological methods. An effective solution involves the use of novel engineered materials, such as silica-based nanostructured materials, which exhibit a high removal capacity for various pollutants. The starting materials are also thermally and mechanically stable, allowing for easy design and development at the nanoscale through versatile functionalization procedures, enabling their effective use in pollutant capture. However, improvements concerning mechanical properties or applicability for repeated cycles may be required to refine their structural features. This review focuses on hybrid/composite polymer-silica nanostructured materials. The state of the art in nanomaterial synthesis, different techniques of functionalization, and polymer grafting are described. Furthermore, it explores the application of polymer-modified nanostructured materials for the capture of heavy metals, dyes, hydrocarbons and petroleum derivatives, drugs, and other organic compounds. The paper concludes by offering recommendations for future research aimed at advancing the application of polymer-silica nanostructured materials in the efficiency of pollutant uptake.

A long chain-induced depletion effect for abnormal grafting in the preparation of bimodal bidisperse polymer-grafted nanoparticles

One of the challenging problems in the research field of polymer nanocomposites is how to prepare nanocomposites with high grafting density and strong ability of dispersion at the same time. For nanocomposites composed of bimodal bidisperse polymer chains and nanoparticles, the above requirements can be met by rationally adjusting the ratio of long and short polymer chains. In this study, the process of grafting bimodal bidisperse polymer chains onto the surface of nanoparticles in a grafting-to manner was investigated via computer simulation and theoretical methods. Three grafting strategies were designed: first short then long (SL) system, both short and long (Both) system and first long then short (LS) system. An abnormal phenomenon for the Both system was found by analyzing the grafting density of long and short polymer chains on the surface of nanoparticles. We speculate that the reason for this anomalous phenomenon is the "depletion effect" brought about by the long chains in the Both system. We employ the Polymer Reference Interaction Site Model (PRISM) theory to investigate this anomaly in-depth. By comparing the radial distribution function (RDF) predicted by the PRISM theory with the RDF results obtained by the molecular dynamics (MD) simulation, we found that with the increase of the number of long chains in the system, the grafting density of short polymer chains on the nanoparticle surface showed an obvious upward trend. The "depletion effect" brought by long chains was the main reason for higher short chains' grafting density of the Both system compared to the SL system. Our findings provide effective guidance for the design of nanoparticle-grafted bimodal bidisperse polymer chains and provide a theoretical basis for experimentation and production of polymer nanocomposites with better performance.

Covalent and Non-covalent Functionalized Nanomaterials for Environmental Restoration

Nanotechnology has emerged as an extraordinary and rapidly developing discipline of science. It has remolded the fate of the whole world by providing diverse horizons in different fields. Nanomaterials are appealing because of their incredibly small size and large surface area. Apart from the naturally occurring nanomaterials, synthetic nanomaterials are being prepared on large scales with different sizes and properties. Such nanomaterials are being utilized as an innovative and green approach in multiple fields. To expand the applications and enhance the properties of the nanomaterials, their functionalization and engineering are being performed on a massive scale. The functionalization helps to add to the existing useful properties of the nanomaterials, hence broadening the scope of their utilization. A large class of covalent and non-covalent functionalized nanomaterials (FNMs) including carbons, metal oxides, quantum dots, and composites of these materials with other organic or inorganic materials are being synthesized and used for environmental remediation applications including wastewater treatment. This review summarizes recent advances in the synthesis, reporting techniques, and applications of FNMs in adsorptive and photocatalytic removal of pollutants from wastewater. Future prospects are also examined, along with suggestions for attaining massive benefits in the areas of FNMs.

Surface ligand rigidity modulates lipid raft affinity of ultra-small hydrophobic nanoparticles: insights from molecular dynamics simulations

Differential preferences between lipids and proteins drive the formation of dynamical nanoscale membrane domains (lipid rafts), which play key roles in the proper functioning of cells. On the other hand, due to the potent physicochemical properties of nanoparticles (NPs), they have been widely used in drug delivery, bio-imaging and regulating various essential biological processes of the cells. Hence, in this work, we aim to design ultra-small hydrophobic NPs with tunable raft affinity, which is supposed to partition into the hydrophobic region of lipid membranes and be able to regulate the dynamics of the lipid raft domains. A series of μs-scale coarse-grained molecular dynamics simulations and umbrella sampling free energy calculations were performed to investigate the role of surface ligand rigidity of ultra-small hydrophobicNPs in their raft affinity. Our results indicated that the preferred localization of NPs can be tuned by adjusting their surface ligand rigidity. Generally, rigid NPs tended to target the raft domain, while soft NPs preferred the interface of the raft and non-raft domains. The free energy analysis further indicated that the surface ligand rigidity of NPs can enhance their targeting to lipid raft domains. Besides, we found that these ultra-small NPs had no significant effects on the phase separation of the lipid membrane although they might cause some local interference to surrounding lipids. These results indicate that the targeting to the lipid raft domain can be achieved by the surface ligand rigidity of NPs, which provides helpful insights for further regulations of lipid raft-mediated biological processes.

Investigating the structure and self-assembly behavior of starch-g-VAc in starch-based adhesive by combining NMR analysis and multi-scale simulation

This work investigated the structure and self-assembly behavior of grafted starch (GS) prepared by grafting vinyl acetate (VAc) on the starch molecule. Our preliminary structure characterization, NMR, and quantum mechanical simulation demonstrated the C2 of the glucose unit as the main grafting site. The grafting frequency and chain length (starch, VAc) were calculated based on the result of gel permeation chromatography. Molecular dynamics simulation showed that, when compared with native starch, GS had less hydrogen bonding interaction, lower orderness, and higher extensibility, which were supported by the experimental results. In dissipative particle dynamics simulation, GS was shown to self-assemble into a core-shell structure (latex) and form a bridge structure with cross-linking interaction. The overall results indicate that chain entanglement and hydrogen bonding interaction of starch play a significant role in adhesive curing. This research provides a novel insight into the grafting and molecular interaction mechanism in the GS adhesive system.

A Versatile Strategy for Unimolecular Micelle-Derived Hollow Polymer Nanoparticles as General Nanoreactors

We reported the synthesis of a well-defined hollow polymer nanoparticle derived from star-shaped unimolecular micelles. β-Cyclodextrin was first applied as an efficient macroinitiator to prepare a star-shaped PCL via ring-opening polymerization (ROP). Then, the star-shaped PCL was modified to be a macro-RAFT agent for photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization of S-Cl monomers. The prepared unimolecular micelles can be photocross-linked under UV irradiation after a simple nucleophilic substitution reaction, which made -Cl groups to be -N₃ groups. After the selective removal of the PCL core, hollow polymer nanoparticles were achieved and exhibited to be a general nanoreactor strategy for the fabrication of nanocrystals with well-controlled architectures. Compared with unimolecular micelle templates, the nanocrystals prepared by hollow templates are absolutely pure as no polymer chains are embedded in the inorganic nanocrystals. In addition, by changing the concentration of the precursor, the structure of the nanocrystal can be changed from a normal spherical structure to a hollow structure.

Optimization of hydrophobic nanoparticles to better target lipid rafts with molecular dynamics simulations

Due to different interactions between lipids and proteins, a plasma membrane can segregate into different membrane domains. Among them, ordered functional membrane domains are defined as "lipid rafts", which play key roles in many biological processes (e.g., signal transduction, endocytosis, etc.) in the cell. Hence, it will be of much biological significance to monitor and even regulate the dynamics of lipid rafts. In this work, we designed a ligand-modified spherical nanoparticle with coarse-grained molecular dynamics simulations, which can be encapsulated into the hydrophobic region of the lipid membrane and specifically target either raft or non-raft membrane domains. The preferred localization of the nanoparticle can be tuned by adjusting ligand hydrophobicity, length and density. Generally, more hydrophobic nanoparticles tend to target the raft domain, while less hydrophobic nanoparticles prefer the non-raft domain. Besides, ligand length and density jointly determine the exposure of nanoparticle cores and thus affect the roles of ligands in nanoparticles' final localization. Our results may provide insights into the experimental design of functional nanoparticles, targeting the lipid raft and regulating its dynamics.

Nanoparticle heterogeneity: an emerging structural parameter influencing particle fate in biological media?

Drug nanocarriers' surface chemistry is often presumed to be uniform. For instance, the polymer surface coverage and distribution of ligands on nanoparticles are described with averaged values obtained from quantification techniques based on particle populations. However, these averaged values may conceal heterogeneities at different levels, either because of the presence of particle sub-populations or because of surface inhomogeneities, such as patchy surfaces on individual particles. The characterization and quantification of chemical surface heterogeneities are tedious tasks, which are rather limited by the currently available instruments and research protocols. However, heterogeneities may contribute to some non-linear effects observed during the nanoformulation optimization process, cause problems related to nanocarrier production scale-up and correlate with unexpected biological outcomes. On the other hand, heterogeneities, while usually unintended and detrimental to nanocarrier performance, may, in some cases, be sought as adjustable properties that provide NPs with unique functionality. In this review, results and processes related to this issue are compiled, and perspectives and possible analytical developments are discussed.

Polymer-grafted nanoparticles prepared via a grafting-from strategy: a computer simulation study

Nanoparticles (NPs) grafted with polymer chains prepared via a grafting-from strategy are studied through coarse-grained molecular dynamics simulations combined with our stochastic reaction model. A system involving multiple individual NPs, with grafting-from processes for all the NPs induced simultaneously, is simulated, so that chain growth competition on the same NP, as well as between neighbouring NPs, are both naturally considered. Our results imply that there should be an optimized range of NP sizes, as compared to monomer size, in which initiator sites are most easily induced. Besides, when the initiator density is high, a shielding effect from the sparse long chains on the most short chains or initiators evidently yields an extremely unbiased distribution of chains. We also adopt a representative polymer-tethered NP prepared via a grafting-from strategy to study the potential of mean force between NPs, so that the dispersion and stabilization abilities of such polymer-grafted NPs in a polymer matrix can be generally predicted during the preparation of polymer nanocomposite materials. Our study helps to elucidate the cause of chain dispersity during the grafting-from process and could act as a guide for better design and to improve the performance of polymer nanocomposites.