Non-covalent Surface Modification Research Articles

Highly homogeneous and stable single-walled carbon nanotubes dispersion modified by polyvinylpyrrolidone and alkanolamine in water.

A novel noncovalent surface modification of commercial single-walled carbon nanotubes (SWCNTs) was successfully carried out by using ball grinding technology between SWCNTs and mixed dispersants (polyvinylpyrrolidone (PVP) and alkanolamine), affording a highly homogeneous and stable PA-SWCNTs dispersion in water. The homogeneous dispersibility and long storage stability were systematically investigated by transmittance spectroscopy, absorption spectroscopy, zeta potential analyzer, sedimentation photo and transmittance electron microscopy. Under the optimized conditions, the PA-SWCNTs dispersion modified with 0.7 wt% PVP and 0.25 wt% alkanolamine under the condition of total 6 h ball grinding time using paint shaker can be easily well-dispersed in water and has good storage stability, and no sedimentation is observed more than one month. From an industrial perspective, this method is green and easy to operate in industry.

Implantable polypyrrole bioelectrodes inducing anti-inflammatory macrophage polarization for long-term in vivo signal recording.

Bioelectrodes are critical components of implantable electronic devices that enable precise electrical signal transmission in close contact with living tissues. However, their in vivo performance is often compromised by inflammatory tissue reactions mainly induced by macrophages. Hence, we aimed to develop implantable bioelectrodes with high performance and high biocompatibility by actively modulating the inflammatory response of macrophages. Consequently, we fabricated heparin-doped polypyrrole electrodes (PPy/Hep) and immobilized anti-inflammatory cytokines (interleukin-4 [IL-4]) via non-covalent interactions. IL-4 immobilization did not alter the electrochemical performance of the original PPy/Hep electrodes. In vitro primary macrophage culture revealed that IL-4-immobilized PPy/Hep electrodes induced anti-inflammatory polarization of macrophages, similar to the soluble IL-4 control. In vivo subcutaneous implantation indicated that IL-4 immobilization on PPy/Hep promoted the anti-inflammatory polarization of host macrophages and significantly mitigated scarring around the implanted electrodes. In addition, high-sensitivity electrocardiogram signals were recorded from the implanted IL-4-immobilized PPy/Hep electrodes and compared to bare gold and PPy/Hep electrodes, which were maintained for up to 15 days post-implantation. This simple and effective surface modification strategy for developing immune-compatible bioelectrodes will facilitate the development of various electronic medical devices that require high sensitivities and long-term stabilities. STATEMENT OF SIGNIFICANCE: To fabricate highly immunocompatible conductive polymer-based implantable electrodes with high performance and stability in vivo, we introduced the anti-inflammatory activity to PPy/Hep electrodes by immobilizing IL-4 via non-covalent surface modification. IL-4-immobilized PPy/Hep could significantly mitigate inflammatory responses and scarring around implants by skewing macrophages to an anti-inflammatory phenotype. The IL-4-immobilized PPy/Hep electrodes could successfully record in vivo electrocardiogram signals for up to 15 days with no substantial sensitivity loss, retaining their superior sensitivity compared to bare gold and pristine PPy/Hep electrodes. Our simple and effective surface modification strategy for developing immune-compatible bioelectrodes will facilitate the development of various electronic medical devices that require high sensitivities and long-term stabilities, such as neural electrode arrays, biosensors, and cochlear electrodes.

Enhanced electromechanical behaviours of epoxidized natural rubber composites via constructing non-covalent and covalent bonds by using tannic acid and Si747

Dielectric elastomer actuators (DEAs) are attractive for use in energy harvesting devices and soft robotics. In this study, barium titanate (BaTiO3) nanoparticles (NPs) were modified by tannic acid (TA) and 3-mercapto-propyl-ethoxy-bis(tridecyl-pentaethoxy-siloxane) (Si747) (denoted as BaTiO3-TA-Si747) via non-covalent and covalent modification. Then the as-prepared BaTiO3-TA-Si747 were incorporated into the epoxidized natural rubber (ENR) matrix (denoted as BaTiO3-TA-Si747-ENR) to prepare ENR DEA, aiming at obtaining high actuated strains at a low electric field. The TA and Si747 exhibited the partial polymeric flexibility on the surface of BaTiO3 NPs, and Si747 participated in the cross-linking reaction of ENR, resulting in a low Young's modulus and a high sensitivity coefficient of the BaTiO3-TA-Si747-ENR composites. Furthermore, TA and Si747 enhanced the interfacial interaction and compatibility between BaTiO3 NPs and the ENR matrix, which decreased the dielectric loss of the ENR composites and increased the efficiency of the energy conversion. A high actuated strain of 14.18% at 57.2 kV/mm was demonstrated by the 10 phr BaTiO3-TA-Si747-ENR composite, whereas pure ENR exhibited a value of 10.42% at 51.4 kV/mm. The combination of non-covalent and covalent surface modification using TA and Si747 is highly efficient, and it is expected to be applied at a large scale in industrial production.

Biomedical applications of solid-binding peptides and proteins.

Over the past decades, solid-binding peptides (SBPs) have found multiple applications in materials science. In non-covalent surface modification strategies, solid-binding peptides are a simple and versatile tool for the immobilization of biomolecules on a vast variety of solid surfaces. Especially in physiological environments, SBPs can increase the biocompatibility of hybrid materials and offer tunable properties for the display of biomolecules with minimal impact on their functionality. All these features make SBPs attractive for the manufacturing of bioinspired materials in diagnostic and therapeutic applications. In particular, biomedical applications such as drug delivery, biosensing, and regenerative therapies have benefited from the introduction of SBPs. Here, we review recent literature on the use of solid-binding peptides and solid-binding proteins in biomedical applications. We focus on applications where modulating the interactions between solid materials and biomolecules is crucial. In this review, we describe solid-binding peptides and proteins, providing background on sequence design and binding mechanism. We then discuss their application on materials relevant for biomedicine (calcium phosphates, silicates, ice crystals, metals, plastics, and graphene). Although the limited characterization of SBPs still represents a challenge for their design and widespread application, our review shows that SBP-mediated bioconjugation can be easily introduced into complex designs and on nanomaterials with very different surface chemistries.

Surface modification of carbon fiber with imidazolium ionic liquids

ABSTRACT Carbon fiber composites are high-performance materials commonly used in advanced applications and their performance is highly dependent on the fiber-matrix interfacial interaction. The non-polar carbon fiber surface may be modified via different techniques to improve adhesion with the polymer matrix. In this work, non-covalent surface modification of carbon fiber has been carried out using two different imidazolium ionic liquids, 1-n-butyl-3-methyl imidazolium bis(trifluoromethylsulfonyl) imide (hydrophobic) and 1-n-butyl-3-methylimidazolium chloride (hydrophilic). The treatment was performed by immersing the fiber into 10 wt. % methanolic ionic liquid solution for 10 min. Treated fibers were characterized using Fourier-transform infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy confirmed the presence of ionic liquid on the carbon fiber surface. Surface morphology of treated fibers analyzed by scanning electron microscopy showed ionic liquid moieties. Wettability of the treated carbon fiber with epoxy resin significantly increased, with a decrease in contact angle greater than 15°. Interfacial shear strength between the modified carbon fiber and epoxy increased up to 56.5% with respect to the unsized carbon fiber, being comparable with epoxy-sized fibers. Thus, the proposed surface modification has the potential to improve the interfacial performance of carbon fiber polymer composites.

Green modification of graphene dispersion with high nanosheet content, good dispersibility, and long storage stability.

In this work, an easy, green, noncovalent surface modification of pristine graphene (GR) was carried out using a single-step method between sodium carboxymethyl cellulose (CMC) and pristine GR, resulting in the formation of a modified CMC–GR (CGR) dispersion with 15% nanosheet content, the first reported in water. Results obtained from thermogravimetry analysis (TGA), Raman spectroscopy, and atomic force microscopy (AFM) confirm that the CMC modifier is successfully decorated on the pristine GR surface. Analyses of transmittance spectrum, zeta potential and transmittance electron microscopy (TEM) images reveal that the modified CGR has a high degree of dispersion. More importantly, the pristine GR is insoluble, while the modified CGR-3, mixed with 1.1 wt% CMC modifier, is easily well dispersed in water and has good flowability, and no sedimentation is observed after more than 3 months.

Mitochondria-targeted mesoporous silica nanoparticles noncovalently modified with triphenylphosphonium cation: Physicochemical characteristics, cytotoxicity and intracellular uptake

Novel nanocomposite system based on mesoporous silica nanoparticles (MSNs) noncovalently modified with hexadecyltriphenylphosphonium bromide (HTPPB) has been prepared, thoroughly characterized and used for encapsulation of model cargo Rhodamine B (RhB). The high encapsulation efficacy of this dye by HTPPB-modified mesoporous particles was demonstrated by spectrophotometry and thermography techniques. The bioavailability of MSN@HTPPB was testified. Cytotoxicity assay revealed that a marked suppression of M−HeLa cancer cells (epithelioid carcinoma of the cervix) occurs at concentration of 0.06 μg/mL, while the higher viability of Chang liver normal cell line was preserved in the concentration range of 0.98–0.06 μg/mL. Hemolysis assay demonstrated that only 2% of red blood cells are destructed at ~ 30 μg/mL concentration. This allows us to select the most harmless compositions based on MSN@HTPPB with minimal side effects toward normal cells and recommend them for the development of antitumor formulations. Fluorescence microscopy technique testified satisfactory penetration of HTPPB-modified carriers into M−HeLa cells. Importantly, modification of the MSN with HTPPB is shown to promote efficient delivery to mitochondria. To the best of our knowledge, it is one of the first successful examples of noncovalent surface modification of the MSNs with lipophilic phosphonium cation that improves targeted delivery of loads to mitochondria.

Surface Modification of Fluorescent Nanodiamonds for Biological Applications.

Fluorescent nanodiamonds (FNDs) are a new class of carbon nanomaterials that offer great promise for biological applications such as cell labeling, imaging, and sensing due to their exceptional optical properties and biocompatibility. Implementation of these applications requires reliable and precise surface functionalization. Although diamonds are generally considered inert, they typically possess diverse surface groups that permit a range of different functionalization strategies. This review provides an overview of nanodiamond surface functionalization methods including homogeneous surface termination approaches (hydrogenation, halogenation, amination, oxidation, and reduction), in addition to covalent and non-covalent surface modification with different functional moieties. Furthermore, the subsequent coupling of biomolecules onto functionalized nanodiamonds is reviewed. Finally, biomedical applications of nanodiamonds are discussed in the context of functionalization.

Prospects for the Use of Upconverting Nanoparticles as a Contrast Agent for Enumeration of Circulating Cells in vivo.

PurposeWe recently developed a new fluorescence-based technique called “diffuse in vivo flow cytometry” (DiFC) for enumerating rare circulating tumor cells (CTCs) directly in the bloodstream. Non-specific tissue autofluorescence is a persistent problem, as it creates a background which may obscure signals from weakly-labeled CTCs. Here we investigated the use of upconverting nanoparticles (UCNPs) as a contrast agent for DiFC, which in principle could significantly reduce the autofluorescence background and allow more sensitive detection of rare CTCs.MethodsWe built a new UCNP-compatible DiFC instrument (U-DiFC), which uses a 980 nm laser and detects upconverted luminescence in the 520, 545 and 660 nm emission bands. We used NaYF4:Yb,Er UCNPs and several covalent and non-covalent surface modification strategies to improve their biocompatibility and cell uptake. We tested U-DiFC with multiple myeloma (MM) and Lewis lung carcinoma (LLC) cells in tissue-mimicking optical flow phantoms and in nude mice.ResultsU-DiFC significantly reduced the background autofluorescence signals and motion artifacts from breathing in mice. Upconverted luminescence from NaYF4:Yb,Er microparticles (UμNP) and cells co-incubated with UCNPs were readily detectable with U-DiFC in phantoms, and from UCNPs in circulation in mice. However, we were unable to achieve reliable labeling of CTCs with UCNPs. Our data suggest that most (or all) of the measured U-DIFC signal in vitro and in vivo likely arose from unbound UCNPs or due to the uptake by non-CTC blood cells.ConclusionUCNPs have a number of properties that make them attractive contrast agents for high-sensitivity detection of CTCs in the bloodstream with U-DiFC and other intravital imaging methods. More work is needed to achieve reliable and specific labeling of CTCs with UCNPs and verify long-term retention and viability of cells.

Supramolecular chemistry of carbon nano-onions.

Carbon nano-onions (CNOs) are concentric multi-layered fullerenes. Their shape, size and layer count depends on the method of preparation. Their low cytotoxicity allows for high applicability in the biomedical field, in particular, nanomedicine. However, an adequate dispersion of particles in aqueous media is required for the most effective use in this application. Given the hydrophobic nature of pristine CNOs, as is the case with most carbon nanomaterials, they show poor water solubility. Non-covalent functionalisation can be utilised to alter their dispersibility properties, without affecting the intrinsic properties of the sp2 nanomaterial. The use of CNOs in the field of nanomedicine also requires consideration of drug release at the target site. As covalent bonds are inadequate for this purpose, attention is brought towards non-covalent interactions as a viable option for targeted release. This minireview outlines the different methods and approaches for non-covalent modifications of CNOs reported in the literature.

Research Progress on Graphene/Polymer Composites with Non-covalent Surface Modification

Research Progress on Graphene/Polymer Composites with Non-covalent Surface Modification

Surface modification of hexagonal boron nitride nanomaterials: a review

Hexagonal boron nitride (h-BN) nanomaterials, such as boron nitride nanotubes, boron nitride nanofibers, and boron nitride nanosheets, are among the most promising inorganic nanomaterials in recent years. Their unique properties, including high mechanical stiffness, wide band gap, excellent thermal conductivity, and thermal stability, suggest many potential applications in various engineering fields. In particular, h-BN nanomaterials have been widely used as functional fillers to fabricate high-performance polymer nanocomposites. Like other nanomaterials, prior to their utilization in nanocomposites, surface modification of h-BNs is often necessary in order to prevent their strong tendency to aggregate, and to improve their dispersion and interfacial properties in polymer nanocomposites. However, the high chemical inertness and resistance to oxidation of h-BNs make it rather difficult to functionalize h-BNs. The methods frequently used to oxidize graphitic carbon nanomaterials are not quite successful on h-BNs. Therefore, many novel approaches have been studied to modify h-BN nanostructures. In this review, different surface modification strategies were discussed including various covalent and non-covalent surface modification strategies through wet or dry chemical routes. Meanwhile, the effects of these surface modification methods on the resulting material structures and properties were also reviewed. At last, a number of theoretical studies on the reactivity of h-BNs with different chemical agents have been conducted to explore new surface modification routes, which were also addressed in this review.

Surface modification of reduced graphene oxide through successive ionic layer adsorption and reaction method for redox dominant supercapacitor electrodes

Non-covalent surface modification technique, where the pre-reduction of graphene oxide (GO) was carried out to recover the π-π conjugation, was performed through a successive ionic layer adsorption and reaction (SILAR) method for preparing redox dominant supercapacitor electrodes. The π-π conjugation of reduced graphene oxide (RGO) facilitated non-covalent interaction with sulfanilic acid azo-chromotrop (SA) to develop electrolyte accessible layer-by-layer (LL) assembly of RGO and SA (LSARGO). In comparison, RGO was modified with SA through continuous stirring of SA and GO, followed by the post reduction technique and designated as NSARGO. The LSARGO revealed higher surface area, electrical conductivity and electrochemical performances than the NSARGO. Sharp redox peaks with well cathodic peak current density vs. square root of the scan rate slope value indicated a redox dominant LSARGO electrode, which was further confirmed by the specific capacitance (SC) values, calculated from the cyclic voltammetry and galvanostatic charge–discharge (GCD) curves in three electrode configuration. The electrochemical impedance spectroscopy study also revealed that the LSARGO provided more redox dominant supercapacitor characteristics as compared to NSARGO. The LSARGO exhibited a SC of ∼1023Fg−1 at scan rate of ∼10mVs−1. The fabricated asymmetric supercapacitor device (ASC) showed an elevated energy and power density of ∼80Whkg−1 and 17,500Wkg−1, respectively. The ASC experienced high GCD cyclic stability of ∼84% after 10,000 cycles.

Noncovalent Surface Modification of Cellulose Nanopapers by Adsorption of Polymers from Aprotic Solvents.

Basic adsorption of hydrophobic polymers from aprotic solvents was introduced as a platform technology to modify exclusively the surfaces of cellulose nanopapers. Dynamic vapor sorption demonstrated that the water vapor uptake ability of the nanopapers remained unperturbed, despite strong repellency to liquid water caused by the adsorbed hydrophobic polymer on the surface. This was enabled by the fact that the aprotic solvents used for adsorption did not swell the nanopaper unlike water that is generally applied as the adsorption medium in such systems. As case examples, the adsorptions of polystyrene (PS) and poly(trifluoroethylene) (PF3E) were followed by X-ray photoelectron spectroscopy and water contact angle measurements, backed up with morphological analysis by atomic force microscopy. The resulting nanopapers are useful in applications like moisture buffers where repellence to liquid water and ability for moisture sorption are desired qualities.

Functionalized graphene oxide-reinforced electrospun carbon nanofibers as ultrathin supercapacitor electrode

Graphene oxide has been used widely as a starting precursor for applications that cater to the needs of tunable graphene. However, the hydrophilic characteristic limits their application, especially in a hydrophobic condition. Herein, a novel non-covalent surface modification approach towards graphene oxide was conducted via a UV-induced photo-polymerization technique that involves two major routes; a UV-sensitive initiator embedded via pi-pi interactions on the graphene planar rings, and the polymerization of hydrophobic polymeric chains along the surface. The functionalized graphene oxide successfully achieved the desired hydrophobicity as it displayed the characteristic of being readily dissolved in organic solvent. Upon its addition into a polymeric solution and subjected to an electrospinning process, non-woven random nanofibers embedded with graphene oxide sheets were obtained. The prepared polymeric nanofibers were subjected to two-step thermal treatments that eventually converted the polymeric chains into a carbon-rich conductive structure. A unique morphology was observed upon the addition of the functionalized graphene oxide, whereby the sheets were embedded and intercalated within the carbon nanofibers and formed a continuous structure. This reinforcement effectively enhanced the electrochemical performance of the carbon nanofibers by recording a specific capacitance of up to 140.10F/g at the current density of 1A/g, which was approximately three folds more than that of pristine nanofibers. It also retained the capacitance up to 96.2% after 1000 vigorous charge/discharge cycles. This functionalization technique opens up a new pathway in tuning the solubility nature of graphene oxide towards the synthesis of a graphene oxide-reinforced polymeric structure.

The Influence of Surfactant Structure and Geometry on Nanotoxicity and Dispersion of Carbon Nanotubes

Graphene, nanotubes and fullerenes, also known as carbon nanomaterials (CN), because of the their unique properties have potential applications not only in preparation of new composite materials or in electronics, but they can be also components of drug delivery systems. However, the applications of CN in life sciences or biomedicine require stable dispersions of these materials in water. The hydrophobic nature of CN causes serious problems with their separation in water solutions. Our study is aimed to find a way of dispersing such CN systems in water, by the use of non-covalent surface modification via different surfactants. In this work we focused on the use of trimeric, dimeric and monomeric surfactants fornon-covalent surface modification of selected carbon nanotubes. The toxicity of these systems (aqueous solutions of CN with surfactants and surfactants solutions) towards selected cell cultures (e. g. HeLa cells) was also tested. The surfactants studied can interact with carbon nanotubes in a number of different modes: hydrophobic interactions (surfactant chains with CN side walls) or π-π interactions (aromatic rings of surfactants with CN surface). Infrared spectroscopy and atomic force microscopy were used for characterization of the systems studied. Finally, we focused on mechanical properties of cells exposed to surfactants and CN. This study was supported by the Ministry of Science and Higher Education (Poland), within the project “Najlepsi z najlepszych!” (DEC - POWR.03.03.00-00-P001/15).

Synergistic Effects in Thermoplastic Polyurethanes Incorporating Hybrid Carbon Nanofillers

Abstract In this study thermoplastic polyurethane (TPUs) nanocomposites incorporating carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) were prepared via melt blending and compression molding and CNT dispersion was optimized by using non-covalent surface modification (surfactant). Filler dispersion was further improved by combining two fillers with different geometric shape and aspect ratio in hybrid filler nanocomposites. Synergistic effects were observed in the TPU-GNP-CNT hybrid composites, especially when combining GNP and CNT at a ratio of 6 : 4, showing higher tensile modulus and strength with respect to the systems incorporating individual CNTs and GNPs at the same overall filler concentration. This improvement was attributed to the interaction between CNTs and GNPs limiting GNP aggregation and bridging adjacent graphene platelets thus forming a more efficient network. Hybrid systems also exhibited improved creep resistance and recovery ability. Morphological analysis carried out by scanning electron microscopy (SEM) indicated that the hybrid nanocomposite presented slightly smaller and more homogeneous filler aggregates. The well-dispersed nanofillers also favored higher phase separation in TPU, as indicated by atomic force microscopy (AFM), resulting in a better microstructure able to enhance the load transfer and maximize the mechanical and viscoelastic properties.

Melt Compounding of Thermoplastic Polyurethanes Incorporating 1D and 2D Carbon Nanofillers

ABSTRACTThermoplastic polyurethane nanocomposites incorporating carbon nanotubes and graphene nanoplatelets were prepared through melt blending and compression molding, and the compounding process was optimized taking into account the different physical properties of one-dimensional carbon nanotubes and two-dimensional graphene nanoplatelets. Filler dispersion was further improved in the case of carbon nanotubes by noncovalent surface modification using a specific surfactant. The well-dispersed nanofillers favored enhanced phase separation in the thermoplastic polyurethane, leading to a better microstructure, which is able to improve the load transfer and maximize the tensile and viscoelastic properties.

Nanostructured multilayer thin films of multiwalled carbon nanotubes/gold nanoparticles/glutathione for the electrochemical detection of dopamine

In the present study, multiwalled carbon nanotubes (MWCNTs), gold nanoparticles (AuNPs), and glutathione (GSH) were used to fabricate multilayer nanoscale thin films. The composite thin films were fabricated by layer-by-layer technique as the films were constructed by the alternate deposition of cationic and anionic polyelectrolytes. The MWCNTs were modified via a noncovalent surface modification method using poly(diallydimethylammonium chloride) to form a cationic polyelectrolyte. An anionic polyelectrolyte was prepared by the chemical reduction of HAuCl4 using sodium citrate as both the stabilizing and reducing agent to form anionic AuNPs. GSH was used as an electrocatalyst toward the electro-oxidation of dopamine. The constructed composite electrode exhibits excellent electrocatalytic activity toward dopamine with a short response time and a wide linear range from 1 to 100 μmol/L. The limits of detection and quantitation of dopamine are (0.316 ± 0.081) μmol/L and (1.054 ± 0.081) μmol/L, respectively. The method is satisfactorily applied for the determination of dopamine in plasma and urine samples to obtain the recovery in the range from 97.90% to 105.00%.

Permselective 2D-polymer-based membrane tuneable by host-guest chemistry.

A permselective membrane with a non-covalently tailorable surface has been fabricated by deposition of a cucurbit[6]uril-based 2D polymer film onto a simple support membrane. Tuneable permselectivity of this membrane has been achieved through non-covalent surface modification using the remarkable host-guest chemistry of the incorporated cucurbit[6]uril units.