Non-covalent Modification Research Articles

Naturally or artificially constructed nanocellulose architectures for epoxy composites: A review

AbstractApplications of carbon fiber reinforced epoxy-based composites have been highly restricted due to their high cost in the manufacturing process. Cellulose, a cheap and abundant material from nature, shows excellent mechanical property and structural stability. It shows huge potentials in substituting carbon fiber/epoxy with cellulose/epoxy composites to fulfill the great demands for composites with good performance and a reasonable price. This paper first reviews works about the preparation and regulation of cellulose materials based on the very basic concepts of top-down and bottom-up. Then research about the interfacial regulation between cellulose and epoxy has been discussed in two broad classes of covalent and non-covalent modification. Finally, the enhancement effect of cellulose reinforcement has been discussed in two broad classes of dispersive reinforcement and continuous phase reinforcement. The latter can be further divided into three classes according to the dimension feature (1D, 2D, and 3D). The results show that the nanolization of cellulose is necessary for guaranteeing the strength of composites, while the formation of macroscopic and continuous structures can ensure Young’s modulus of composites.

Click Chemistry Enabling Covalent and Non-Covalent Modifications of Graphene with (Poly)saccharides

Graphene is a material with outstanding properties and numerous potential applications in a wide range of research and technology areas, spanning from electronics, energy materials, sensors, and actuators to life-science and many more. However, the insolubility and poor dispersibility of graphene are two major problems hampering its use in certain applications. Tethering mono-, di-, or even poly-saccharides on graphene through click-chemistry is gaining more and more attention as a key modification approach leading to new graphene-based materials (GBM) with improved hydrophilicity and substantial dispersibility in polar solvents, e.g., water. The attachment of (poly)saccharides on graphene further renders the final GBMs biocompatible and could open new routes to novel biomedical and environmental applications. In this review, recent modifications of graphene and other carbon rich materials (CRMs) through click chemistry are reviewed.

Evaluation of Surface Modified Live Biotherapeutic Products for Oral Delivery.

Live biotherapeutic products (LBPs), including symbiotic and genetically engineered bacteria, are a promising class of emerging therapeutics that are widely investigated both preclinically and clinically for their oral delivery to the gastrointestinal (GI) tract. One emergent delivery strategy involves the direct functionalization of LBP surfaces through noncovalent or covalent modifications to control LBP interactions with the GI microenvironment, thereby improving their viability, attachment, or therapeutic effect. However, unlike other therapeutic modalities, LBPs are living organisms which present two unique challenges for surface modifications: (1) this approach can directly interfere with key LBP biological processes (e.g., colonization, metabolite secretion) and (2) modification can be variable due to the dynamic nature of LBP surfaces. Collectively, these factors remain uncharacterized as they relate to the oral delivery of LBPs. Herein, we leverage our previously reported surface modification platform, which enables LBP surface-presentation of targeting ligands, to broadly evaluate and characterize surface modifications on LBPs. Specifically, we evaluate how LBP growth affects the dilution of surface-presented targeting ligands and the subsequent loss of specific target attachment over time. Next, we describe key surface modification parameters (e.g., concentration, residence time) that can be optimized to facilitate LBP target attachment. We then characterize how bioconjugation influences the suitability of LBPs for oral delivery by evaluating their growth, viability, storage, toxicity against mammalian cells, and in vivo colonization. Broadly, we describe key parameters that influence the performance of surface modified LBPs and subsequently outline an experimental pipeline for characterizing and evaluating their suitability for oral delivery.

Antibacterial Layer-by-Layer Coatings for Medical Implants.

The widespread occurrence of nosocomial infections and the emergence of new bacterial strands calls for the development of antibacterial coatings with localized antibacterial action that are capable of facing the challenges posed by increasing bacterial resistance to antibiotics. The Layer-by-Layer (LbL) technique, based on the alternating assembly of oppositely charged polyelectrolytes, can be applied for the non-covalent modification of multiple substrates, including medical implants. Polyelectrolyte multilayers fabricated by the LbL technique have been extensively researched for the development of antibacterial coatings as they can be loaded with antibiotics, antibacterial peptides, nanoparticles with bactericide action, in addition to being capable of restricting adhesion of bacteria to surfaces. In this review, the different approaches that apply LbL for antibacterial coatings, emphasizing those that can be applied for implant modification are presented.

Modifying Cell Membranes with Anionic Polymer Amphiphiles Potentiates Intracellular Delivery of Cationic Peptides.

Rapid, facile, and noncovalent cell membrane modification with alkyl-grafted anionic polymers was sought as an approach to enhance intracellular delivery and bioactivity of cationic peptides. We synthesized a library of acrylic acid-based copolymers containing varying amounts of an amine-reactive pentafluorophenyl acrylate monomer followed by postpolymerization modification with a series of alkyl amines to afford precise control over the length and density of aliphatic alkyl side chains. This synthetic strategy enabled systematic investigation of the effect of the polymer structure on membrane binding, potentiation of peptide cell uptake, pH-dependent disruption of lipid bilayers for endosome escape, and intracellular bioavailability. A subset of these polymers exhibited pKa of ∼6.8, which facilitated stable membrane association at physiological pH and rapid, pH-dependent endosomal disruption upon endocytosis as quantified in Galectin-8-YFP reporter cells. Cationic cell penetrating peptide (CPP) uptake was enhanced up to 15-fold in vascular smooth muscle cells in vitro when peptide treatment was preceded by a 30-min pretreatment with lead candidate polymers. We also designed and implemented a new and highly sensitive assay for measuring the intracellular bioavailability of CPPs based on the NanoLuciferase (NanoLuc) technology previously developed for measuring intracellular protein-protein interactions. Using this split luciferase class of assay, polymer pretreatment enhanced intracellular delivery of the CPP-modified HiBiT peptide up to 30-fold relative to CPP-HiBiT without polymer pretreatment (p < 0.05). The overall structural analyses show that polymers containing 50:50 or 70:30 molar ratios of carboxyl groups to alkyl side chains of 6-8 carbons maximized peptide uptake, pH-dependent membrane disruption, and intracellular bioavailability and that this potentiation effect was maximized by pairing with CPPs with high cationic charge density. These results demonstrate a rapid, mild method for polymer modification of cell surfaces to potentiate intracellular delivery, endosome escape, and bioactivity of cationic peptides.

Functionalization of carbon nanomaterials: Dispersion and thermal conductivity measurement

Carbon nanomaterials (CNs) have attracted greater deal of interest due to their precise and remarkable bodily properties. The present painting proposes to observe the Multi-walled Carbon Nanotube (MWCNT) and Multi-walled Carbon Nano-coil (MWCNC) as capability carbon nanomaterials for the nanofluids. Our effort has been devoted to analyze structural changes, dispersion and thermal conductivity measurement. Covalent and non-covalent modifications of CNs were investigated on the way to obtain accurate dispersion and conductivity.The outcomes demonstrated that very much scattered Cu/MWCNTs nanofluids with shifting grouping of Cu/MWCNTs can be combined utilizing the current technique. A most extreme warm conductivity at a low volume portion of Cu/MWCNTs has come about because of the homogeneous scattering of Cu finished MWCNTs in base liquids and arrangement of increasingly hydrophilic MWCNTs because of the connection of oxygen containing utilitarian gatherings prompting a decent co-operations of MWCNTs with another. Oxidative adjustment of nanomaterial delivered about by using corrosive remedy and achieve of oxidative ultra-sonication on improvement of beneficial at the carbon nanomaterials became explored for numerous timeframes. Structural stability has been monitored through thermo gravimetric evaluation (TGA) and morphological characterization through scanning electron microscopy (SEM). Hydrophilic effect of chemical functionalization on CNs turned into investigated by means of FT-IR and Raman spectroscopy. The heating conductivity execution of CN based totally nanofluids turned into concentrated with differed quantity quantities and temperature not exceeding (25–50 °C).

Downregulation of MDR 1 gene contributes to tyrosine kinase inhibitor induce apoptosis and reduction in tumor metastasis: A gravity to space investigation.

P-glycoprotein (P-gp) associated multidrug resistance (MDR) represents a major failure in cancer treatment. The overexpression of P-gp is responsible for ATP-dependent efflux of drugs that decrease their intracellular accumulation. An effective downregulation of MDR1 gene using small interfering RNA (siRNA) is one of the safe and effective tools to overcome the P-gp triggered MDR. Therefore, the development of an efficient and non-toxic carrier system for siRNA delivery is a fundamental challenge for effective cancer treatment. Polyamidoamine (PAMAM) dendrimer has been used for efficient delivery of siRNA (dendriplexes) to the tumor cells but the associated toxicity problems render its use in biological applications. A non-covalent lipid modification (lipodendriplexes) is supposed to offer a promising strategy to overcome the demerits linked to the naked dendriplexes system. In the current study, we deliver siRNA, designed against MDR1 gene (si-MDR1), in colorectal carcinoma cells (Caco-2), having overexpression of P-gp, to check the role of MDR1 gene in tumor progression and multidrug resistance using two dimensional (2D) and three dimensional (3D) environment. Imatinib mesylate (IM), a P-gp substrate, was used as model drug. Our results revealed that the effective knockdown by lipodendriplexes system can significantly reduce the tumor cell migration in 2D (p<0.001) and 3D (p<0.001) cell cultures as compared to unmodified dendriplexes and si-Control groups. It was also observed that lipodendriplexes aided downregulation of MDR1 gene effectively, re-sensitized the Caco-2 cells for IM uptake and showed a significantly (p<0.001) higher apoptosis. Our findings imply that our lipodendriplexes system has a great potential for siRNA delivery, however, further in vivo application using a suitable targeted system can play a major role for better cancer therapeutics.

Cytotoxicity Effects of Water-Soluble Multi-Walled Carbon Nanotubes Decorated with Quaternized Hyperbranched Poly(ethyleneimine) Derivatives on Autotrophic and Heterotrophic Gram-Negative Bacteria.

Oxidized multi-walled carbon nanotubes (oxCNTs) were functionalized by a simple non-covalent modification procedure using quaternized hyperbranched poly(ethyleneimine) derivatives (QPEIs), with various quaternization degrees. Structural characterization of these hybrids using a variety of techniques, revealed the successful and homogenous anchoring of QPEIs on the oxCNTs’ surface. Moreover, these hybrids efficiently dispersed in aqueous media, forming dispersions with excellent aqueous stability for over 12 months. Their cytotoxicity effect was investigated on two types of gram(−) bacteria, an autotrophic (cyanobacterium Synechococcus sp. PCC 7942) and a heterotrophic (bacterium Escherichia coli). An enhanced, dose-dependent antibacterial and anti-cyanobacterial activity against both tested organisms was observed, increasing with the quaternization degree. Remarkably, in the photosynthetic bacteria it was shown that the hybrid materials affect their photosynthetic apparatus by selective inhibition of the Photosystem-I electron transport activity. Cytotoxicity studies on a human prostate carcinoma DU145 cell line and 3T3 mouse fibroblasts revealed that all hybrids exhibit high cytocompatibility in the concentration range, in which they also exhibit both high antibacterial and anti-cyanobacterial activity. Thus, QPEI-functionalized oxCNTs can be very attractive candidates as antibacterial and anti-cyanobacterial agents that can be used for potential applications in the disinfection industry, as well as for the control of harmful cyanobacterial blooms.

Peptide-inspired green synthesis of hedgehog-like CuO nanoclusters on reduced graphene oxide for non-enzymatic hydrogen peroxide sensor

Bioinspired synthesis provides a potential green method for creating functional nanomaterials on graphene supports. In this study, we demonstrate the preparation of hedgehog-like cupric oxide nanoclusters (CuONCs) on peptide-modified reduced graphene oxide (RGO-Pep) nanohybrids through a solution-phase synthesis in which the bound peptide molecules (GNNQQNYEE) mediate the non-covalent modification of GO and provide the adsorption of Cu[Formula: see text] ions and the nucleation sites for the growth of CuONCs. The synthesized RGO-Pep-CuONCs hybrids were further utilized for the modification of a glass carbon electrode to fabricate a non-enzymatic electrochemical sensor for hydrogen peroxide (H2O2). It was found that the fabricated H2O2 sensor exhibited good performances for sensing H2O2 with a detection limit of [Formula: see text]M and two wide linear detection ranges. In addition, this sensor revealed good selectivity and stability. It is expected that the strategies used in this study will be valuable to inspire the creation of various functional biomolecule- and graphene-based hybrid bionanomaterials for the applications in materials science, sensors, biomedical engineering, tissue engineering, nanotechnology, and other fields.

Synergistic effects of ultrafine particles and graphene oxide on hydration mechanism and mechanical property of dune sand-incorporated cementitious composites

An effective method is proposed in this study to overcome the mechanical defects of dune sand-incorporated cementitious composites (DSCC). First, focused on the dispersion behavior of graphene oxide (GO) in simulated cement slurry, a GO-stabilized dispersion was prepared using noncovalent modification methods. Then, a series of tests were conducted to evaluate the effects of GO dispersion on the mechanical properties and hydration characteristics of DSCC. The results show that the DSCC specimen with full dune sand and GO content of 0.03 wt% achieved 125.41% of compressive strength and 94.9% of flexural strength of the standard sand specimen at a curing time of 28 days. In addition, the porosity and microcracks can be controlled by incorporating GO in the cement matrix. Moreover, a synergistic effect was observed between GO and ultrafine particles in dune sand, which promotes the hydration reaction and pozzolanic effect in cement matrix.

The Ubiquitin/UBL Drug Target Repertoire

Ubiquitin (Ub) and ubiquitin-like proteins (UBLs) form an indispensable regulatory layer in human cell biology [1,2]. Cascades of approximately nine activating (E1) enzymes, ~40 conjugating (E2) enzymes, and >600 (E3) ligases can covalently attach distinct topologies of Ub and some UBLs to substrate proteins. More than 100 proteases – deubiquitylating enzymes (DUBs) and deUBLylases – dynamically reverse these modifications (A–C) [1–4]. Other UBLs function mainly as noncovalent modifiers (B, bottom). Dysregulation of Ub/UBL systems is linked to various human diseases (C) [1,3–10].

Self-Assembly of Amphiphilic Compounds as a Versatile Tool for Construction of Nanoscale Drug Carriers.

This review focuses on synthetic and natural amphiphilic systems prepared from straight-chain and macrocyclic compounds capable of self-assembly with the formation of nanoscale aggregates of different morphology and their application as drug carriers. Since numerous biological species (lipid membrane, bacterial cell wall, mucous membrane, corneal epithelium, biopolymers, e.g., proteins, nucleic acids) bear negatively charged fragments, much attention is paid to cationic carriers providing high affinity for encapsulated drugs to targeted cells. First part of the review is devoted to self-assembling and functional properties of surfactant systems, with special attention focusing on cationic amphiphiles, including those bearing natural or cleavable fragments. Further, lipid formulations, especially liposomes, are discussed in terms of their fabrication and application for intracellular drug delivery. This section highlights several features of these carriers, including noncovalent modification of lipid formulations by cationic surfactants, pH-responsive properties, endosomal escape, etc. Third part of the review deals with nanocarriers based on macrocyclic compounds, with such important characteristics as mucoadhesive properties emphasized. In this section, different combinations of cyclodextrin platform conjugated with polymers is considered as drug delivery systems with synergetic effect that improves solubility, targeting and biocompatibility of formulations.

Fourier-transform ion cyclotron resonance mass spectrometry for characterizing proteoforms.

Proteoforms contribute functional diversity to the proteome and aberrant proteoforms levels have been implicated in biological dysfunction and disease. Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), with its ultrahigh mass-resolving power, mass accuracy, and versatile tandem MS capabilities, has empowered top-down, middle-down, and native MS-based approaches for characterizing proteoforms and their complexes in biological systems. Herein, we review the features which make FT-ICR MS uniquely suited for measuring proteoform mass with ultrahigh resolution and mass accuracy; obtaining in-depth proteoform sequence coverage with expansive tandem MS capabilities; and unambiguously identifying and localizing post-translational and noncovalent modifications. We highlight examples from our body of work in which we have quantified and comprehensively characterized proteoforms from cardiac and skeletal muscle to better understand conditions such as chronic heart failure, acute myocardial infarction, and sarcopenia. Structural characterization of monoclonal antibodies and their proteoforms by FT-ICR MS and emerging applications, such as native top-down FT-ICR MS and high-throughput top-down FT-ICR MS-based proteomics at 21 T, are also covered. Historically, the information gleaned from FT-ICR MS analyses have helped provide biological insights. We predict FT-ICR MS will continue to enable the study of proteoforms of increasing size from increasingly complex endogenous mixtures and facilitate the benchmarking of sensitive and specific assays for clinical diagnostics. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.

Conjugation of antibodies and aptamers on nanozymes for developing biosensors

Nanozymes are engineered nanomaterials with enzyme-like activities. Over the past decade, impressive progresses on nanozymes in biosensing have been made due to their unique advantages of high stability, low cost, and easy modification compared to natural enzymes. For many biosensors, it is critical to conjugate nanozymes to affinity ligands such as antibodies and aptamers. Since different nanomaterials have different surface properties, conjugation methods need to be compatible with these properties. In addition, the effect of biomolecules on nanozyme activity needs to be considered. In this review, we first categorized nanozyme-based biosensors into four parts, respectively describing noncovalent and covalent modifications with antibodies and aptamers. Meanwhile, recent advances in antibody and aptamer labeled nanozyme biosensors are summarized, and the methods of their conjugation are further illustrated. Finally, conclusions and future perspectives for the development and application of nanozyme bioconjugates are discussed.

Synergistic effect of polyvinylpyrrolidone noncovalently modified graphene and epoxy resin in anticorrosion application

In this article, polyvinylpyrrolidone (PVP) was used for the noncovalent modification on the surface of graphene. Compared with covalent modification, this method maintained the original structure of graphene layers, thereby maximizing the original properties of graphene. The π–π noncovalent bond was formed between PVP and graphene by X-ray photoelectron spectroscopy analysis, indicating that PVP successfully modified graphene. The thickness of graphene layer was measured by atomic force microscopy, which showed that the distance between graphene layers was increased by 5–6 nm, and the stability of the modified graphene in N, N-dimethylformamide was remarkably improved. The obtained composite coating by combination of the modified graphene and the epoxy resin was subjected to electrochemical impedance test to obtain the best anticorrosive effect of the coating with the graphene content of 0.3 wt%. The results showed that the addition of graphene to the epoxy resin could effectively improve the anticorrosive effect. Meanwhile, the good electrical conductivity allowed the electrons which lost from the substrate to led to air or saline rapidly, thereby reducing the combination of iron ions with oxygen and the generation of corrosion products (iron oxides).

Effects of non-covalent interactions on the properties of 3D printed flexible piezoresistive strain sensors of conductive polymer composites

ABSTRACT In this work, flexible piezoresistive strain sensors of carbon nanotubes (CNT)/thermoplastic polyurethane (TPU) conductive polymer composites were prepared using fused filament fabrication (FFF) 3D printing. The constructed porous structure and highly elastic TPU matrix allow the sensors to experience strains up to 30% with great recoverability. The printed sensors exhibited a typical negative piezoresistive effect under compressive strain. The effects of non-covalent modification and loading of CNTs on the mechanical and piezoresistive behavior of sensors were investigated. The introduction of 1-pyrenecarboxylic acid (PCA) increased the dispersibility of CNTs and nanofiller-polymer interfacial interactions, resulting in the excellent sensing performance. A sensor with higher CNT content showed greater sensitivity due to generation of more conductive paths during compression. The gauge factor () of the 3 wt% CNT/PCA/TPU sensor increased by 43 and 35 times compared with the 3 wt% CNT/TPU and the 1.5 wt% CNT/PCA/TPU sensors, respectively, when strained at 26% to 30%. In addition, the printed sensor of 3 wt% CNT/PCA/TPU showed great reproducibility over 1500 loading cycles. Some applications in monitoring external loads and motion of the human body were demonstrated. This work provides important information for the property optimization and customizable fabrication of flexible piezoresistive strain sensors.

Study on the mechanism and process of a universal preparation of carbon nanotubes uniform dispersions in aqueous solution

One of the most important factors restricting the application of carbon nanotubes (CNTs) is how to uniformly disperse CNTs in liquid phase. In this paper, the mechanism of non-covalent modification of carbon nanotubes has been studied by using the method of all-atom molecular dynamics simulation, and the corresponding experiments have been carried out to verify the obtained mechanism. The results show that non-covalent modification is an effective way to disperse carbon nanotubes. The morphology of surfactants on the surface of carbon nanotubes is an important factor for stable dispersion. This research will provide a more detailed explanation for the interaction of all atoms in dispersing process and guide the dispersing experiment in order to promote the industrial application of CNTs.

Rheological and Morphological Properties of Non-Covalently Functionalized Graphene-Based Structural Epoxy Resins with Intrinsic Electrical Conductivity and Thermal Stability.

In this paper, a non-covalent π–π interaction between graphene nanoparticles (G) and a pyrene-based molecule (py) has been successfully accomplished to give the functionalized nanofillers (G-py). The proposed modification has proven to be a winning solution aimed at safeguarding the graphene’s notable electronic properties, while promoting a more effective nanofiller dispersion attributable to a decrease in viscosity with consequent improvement of the rheological properties of the formulated nanocomposites filled with G-py. The electrical current maps of the G-py based epoxy composites, loaded with filler weight percentages both above and below the electric percolation threshold (EPT), were obtained by tunneling atomic force microscopy (TUNA) technique. The possibility to detect low currents also for the sample at lower concentration (0.1 wt%) confirms the good electrical performance of the nanocomposites and, consequently, the successful performed functionalization. The non-covalent modification significantly improves the thermal stability of the unfunctionalized G of about 70 °C, thus causing an increase in the composite oxidative thermostability since the evolution of CO2 shifts to higher values. Moreover, non-covalent functionalization proved to be impactful in imparting an overall enhancement of the nanocomposite mechanical properties due to good bonding between graphene and epoxy matrix, also showing a greater roughness which is decisive in influencing the interface adhesion efficiency.

Non-covalent modification of boron nitride nanoparticle-reinforced PEEK composite: Thermally conductive, interfacial, and mechanical properties

A non-covalent modified boron nitride(n-CMBN) was obtained by non-covalent modification successfully and used to prepare poly(ether ether ketone)(PEEK) composites. The non-covalent modifier is polyetherimide(PEI), which has high compatibility with PEEK. Particularly, only a small amount of PEI was used to modify BN, which made the thermal conductivity of 30 wt% n-CMBN/PEEK reached 1.01 W·(m·K)−1, 16% higher than that of BN/PEEK. Modified Hashin-Shtrikman model demonstrated that n-CMBN/PEEK possessed 7% lower total thermal resistance compared with BN/PEEK. Moreover, the tensile strength and elongation at break remains above 99.0 MPa and 14.6% respectively, demonstrating the relatively good mechanical properties in high thermally conductive composites. The introduction of 10 wt% n-CMBN decrease the friction coefficient of PEEK composites, which was as low as 0.33 of 30% lower than that of PEEK. In addition, the 5% weight loss temperature were above 557 °C, exhibiting the excellent heat resistant.

An Optimized Strategy for Self-Assembly of Carbon Nanotubes Arrays: From the Perspective of Molecular Dynamics Simulation and Experiments

Hydrophilic/hydrophobic self-assembly has been recognized as one of the effective strategies for assembling carbon nanotubes (CNTs) arrays, but it takes a long time to accomplish this task. So since the emergence of this method, scientists have been exploring how to shorten the assembly process. Meanwhile, up to now, little progress has been made on the mechanism of patterned self-assembly of CNTs. In this paper, in view of the proposal that the assembly of CNTs is able to be accomplished only by hydrophilic functionalization of the substrate, the feasibility of this scheme is verified by molecular dynamics simulation and experiments. Specifically speaking, single-walled carbon nanotubes (SWNTs) with better properties are taken as the research object, and the morphology of surfactant molecule on the surface of SWNTs after non-covalent modification, the optimal model of hydrophilic functionalized substrates (H-substrates) and the morphological changes after the interaction between modified SWNTs (M-SWNTs) and H-substrates are studied by molecular dynamics simulation. At the same time, experiments corresponding to the simulation steps are carried out. The results show that only hydrophilic functionalization of the substrate can also complete the assembly of CNTs, in which the electrostatic attraction between surfactant molecules and H-substrates is the driving force for self-assembly of SWNTs onto hydrophilic surface, and intervention of H2O molecules between M-SWNTs and bare SiO2 substrates is the main reason why SWNTs cannot be assembled onto bare SiO2 surface. The results provide an optimization strategy for the fabrication of CNTs arrays based on self-assembly method.