Platform For Surface Modification Research Articles

Carbon cloth modified by direct growth of nitrogen-doped carbon nanofibers and its utilization as electrode for zero gap flow batteries

The synthetic procedure and characterization of carbon nanofibers (CNFs) grown on carbon cloth (CC) are explored in this study, with a focus on their potential application as electrodes in vanadium redox flow batteries (VRFBs). CC offers an attractive platform for surface modification owing to its conductive properties and three-dimensional architecture, while the N-doped CNFs formed by nitrogen (N) rich composition of melamine precursor enhance wettability of electrolyte and redox reactivity of vanadium ions. Electrochemical assessments reveal that NCC electrodes significantly increase voltage efficiency (VE) and capacity retention in VRFBs compared to bare CC (BCC) electrodes. Notably, NCC demonstrates a VE of 65.9%, surpassing the 55.9% of BCC electrodes. Additionally, NCC maintains superior capacity retention under varying current densities, a crucial factor for VRFBs. Long-term stability tests over 1000 cycles highlight the NCC electrode's durability, with only a minimal decrease in VE. Post-experiment analysis confirms the structural integrity of the CNFs on the CC electrodes, validating their resilience in VRFB operations. In summary, the study introduces a novel approach for fabricating N-doped CNFs on CC, resulting in electrodes that significantly boost VRFB performance in terms of efficiency, capacity retention, and stability, marking a notable advancement in flow battery technology.

Two-dimensional superlattice films of gold nanoparticle-polystyrene composites: a bioactive platform for bone homeostasis maintenance

Osseo-integration between the implant and bone is a crucial factor to create a strong, durable bond that allows the implant to function effectively. However, regular implant surface with poor osseo-integration ability may cause aseptic loosening, resulting in the failure of implants. Herein, a serial of macroscopic one-particle thick superlattice films generated by self-assembly of diverse size of gold nanoparticles (GNPs) were termed as SFGs and were considered as bioactive implant coatings for enhancing osseo-integration. A hydroquinone-assisted seed method is established to fabricate homogenous GNPs with controllable sizes (20, 60, and 90 nm), which were further employed as building blocks to generate macroscopic one-particle thick superlattice films of GNPs (SFGs-20, SFGs-60, and SFGs-90) with the assistance of ploystryrene. The SFGs present a size-dependent performance on bone homeostasis, where SFGs-90 demonstrated the most pronounced facilitation of osteogenic differentiation of osteoblasts as well as deactivation of osteoclasts compared with SFGs-20 and SFGs-60. Considering the universal applicability of SFGs for depositing on various substrates, these SFGs with enhanced osseo-integration capabilities could serve as a bioactive platform for surface modification of orthopedic implants, effectively addressing the issue of aseptic loosening.Graphical abstractTwo-dimensional superlattice films of gold nanoparticle-polystyrene composites exhibit enhanced osteogenic-stimulation and osteoclastic-inhibition effects for regulating bone homeostasis maintenance.

Nanoscale multiply charged focused ion beam platform for surface modification, implantation, and analysis.

The PELIICAEN (Platform for the Study of Ion Implantation Controlled and Analyzed at the Nanometric Scale) setup is a unique device, both for all of its in situ ultra-high vacuum equipment (focused ion beam column, secondary electron microscope, atomic force microscope, and scanning tunneling microscope) and for its nanostructuration performances on materials. The setup has been recently equipped with its own electron cyclotron resonance ion sources, a new position-controlled platform using pneumatic vibration insulators, and a fast pulsing device. Its performances were then deeply improved, providing access to a large choice of ions, an adjustable ion implantation depth up to a few hundred nanometers, an image resolution down to 25 nm, and an ion beam size on the sample down to 100 nm. With all this equipment, the PELIICAEN setup is in the international foreground to perform and analyze ion implantation and surface modification.

A low-fouling, self-assembled, graft co-polymer and covalent surface coating for controlled immobilization of biologically active moieties

Current biointerfaces aiming to steer specific biological responses frequently lack either stability due to purely electrostatic interactions, bioactivity due to unspecific conjugation chemistries, specificity due to uncontrolled biological interactions such as fouling, or cytocompatibility due to harsh and toxic coating procedures. Here, we report a versatile surface modification platform for covalent tethering of selected biomolecules. New in this approach is the particular combination of modular binding blocks as graft co-polymer. Grafted to the backbone of PAcrAmTM multiple functionalities are strategically combined: covalent (silane) and non-covalent (lysine) surface binding groups for stability and self-assembly in mild buffered solution, PEG-azide chains for low fouling properties, and specific, controlled, covalent, linking of biologically active molecules. This modular strategy overcomes the previously mentioned limitations, for instance regarding bioactivity of the biological moiety due to highly specific strain-promoted azide-alkyne cycloaddition. The successful grafting of the copolymer was confirmed by 1H NMR. The immobilization of RGD peptides was characterized by combining surface analytical techniques, such as ToF-SIMS and ellipsometry, allowing quantification of immobilized molecules over an extensive range of concentrations (0.008–1.95 pmol·cm−2). The bioactivity over this range of concentrations was confirmed by in vitro cell studies, presenting a differential endothelial cell attachment and spreading. The modified substrates enabled the formation of an interconnected monolayer of endothelial cells. Furthermore, the modular platform allowed the co-immobilization of two bioactive functional groups, RGD and biotin, on the same surface, which could be exploited for the further development of controlled multi-functional biointerfaces for diverse biological applications in the future.

Polydopamine: a bioinspired adhesive and surface modification platform

AbstractPolydopamine is a biopolymer that is gaining widespread interest as a surface modifying agent due to its simplicity of preparation, versatility and biocompatibility. The material was first described during electrochemical studies of dopamine, but recognition of its structural similarity to key components of mussel adhesive proteins, which are able to adhere to a diverse range of surfaces in water, has led to its incorporation into a host of composite materials. This review will examine some of the emerging investigations into the complex mechanism of polydopamine formation, proposed structures and potential applications, with an emphasis on its use in biomedicine. © 2021 Society of Industrial Chemistry.

Targeted antitumor comparison study between dopamine self-polymerization and traditional synthesis for nanoparticle surface modification in drug delivery

To improve the therapeutic efficacy of anticancer agents and extend their application, mussel-inspired chemical modifications have attracted considerable attention. Surface modification based on polydopamine (PDA) has been a facile and versatile method to immobilize biomolecules on substrates for targeted drug delivery. To better analyze pharmaceutical differences between PDA-based surface modification and traditional synthesis methods, we prepared two kinds of folate (FA)-targeted nanoparticles (NPs) loaded with paclitaxel (PTX). The resultant PTX-PDA-FA NPs and PTX-FA NPs represented PDA and synthesis strategies, respectively. PTX-PDA-FA NPs and PTX-FA NPs have been characterized. The particle size of PTX-PDA-FA NPs was smaller than that of PTX-FA NPs. The two kinds of NPs both exhibited long-rod morphology, good colloidal stability and sustained slow drug release. Cytotoxicity in vitro was evaluated, and antitumor efficacy was investigated against 4T1 tumor-bearing mice. The tumor targeting therapeutic index of PTX-PDA-FA NPs and PTX-FA NPs showed equivalent superior specificity compared to nontargeted groups, which indicated that FA successfully attached to the surface of NPs by the PDA method and that the antitumor effect was equivalent to that of FA-modified NPs prepared by the chemical synthesis method. These results further indicated that PDA, as a simple and effective chemical surface modification platform, could be developed and applied in targeted delivery systems.

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.

Biomimetic surface functionalization of SiO2 microspheres with catecholamine-containing poly(itaconic acid) for removal of cationic dye

In this work, we reported direct surface functionalization of SiO2 microspheres with catecholamine-containing copolymers where dopamine methacrylamide (DMA) and itaconic acid (IA) were considered as polymerizable monomers for the first time. The resultant SiO2@poly (DMA-co-IA) composites were utilized for removal of organic dyes from aqueous solution. The experimental results indicated that, the adsorption capacity of SiO2 microspheres was remarkably increased after surface modification. The maximum theoretical adsorption capacity (406.50 mg/g) of SiO2@poly (DMA-co-IA) indicated great potential in environmental remediation applications. The above-mentioned results proved that SiO2@poly (DMA-co-IA) composites have significant value in practical environment applications. More attractively, surface functionalization strategy in this work could be a universal and facile platform for surface modification of many raw materials for different applications owing to universal adhesiveness of dopamine towards different substrates.

A versatile platform for surface modification of microfluidic droplets.

To advance emulsion droplet technology, we synthesize functional derivatives of Pluronic F127 that can simultaneously act as surfactants and as reactive sites for droplet surface decoration. The amine-, carboxyl-, N-hydroxysuccinimide ester-, maleimide- and biotin-terminated Pluronic F127 allows ligand immobilization on single-emulsion or double-emulsion droplets via electrostatic adsorption, covalent conjugation or site-specific avidin-biotin interaction.

Surface modification of microfluidic droplets

Event Abstract Back to Event Surface modification of microfluidic droplets Weiqian Jiang1, Mingqiang Li1 and Kam W. Leong1 1 Columbia University, Biomedical Engineering, United States Introduction: Microfluidics reliably produces single and multiple emulsions with uniform size that can be applied in a wide variety of fields, such as material synthesis[1], single-cell analysis[2],[3], protein crystallization[4], enzymatic activity assay[5]-[7], and bacterial or mammalian cell culture[8],[9]. Among many other applications, drug delivery using microfluidic droplets is attractive due to their manipulability and versatility for encapsulation and release of both polar and non-polar drugs. However, the lack of chemical reactivity and selectivity of commercial surfactants, which are on the interface of droplets and involved in their stabilization, limits functionalization and manipulation of surface properties of the droplet-based drug delivery system. In the present study, we present an efficient method to surface-functionalize microfluidic droplets by modifying hydroxyl—the terminal group of the surfactant Pluronic F-127—into amino, carboxyl, N-hydroxysuccinimide ester (NHS), maleimide and biotin. We propose that these functional derivatives of Pluronic F-127 can act as surfactants for microfluidic droplets and achieve surface modifications via electrostatic adsorption, covalent conjugation and site-specific avidin-biotin interaction, respectively. Materials and Methods: The amino (NH2), carboxyl (COOH), N-hydroxysuccinimide ester (NHS), maleimide (MAL) and biotin-terminated Pluronic F-127s were prepared through chemical modification of the hydroxyl groups of F-127. Monodisperse oil-in-water (O/W) or water-in-oil-in-water (W/O/W) microdroplets were generated by using polydimethylsiloxane (PDMS) microfluidic chips in the presence of one or multiple functional surfactants and fluorinated oil HFE-7500. FITC-labeled heparin, Cy3-labeled poly (ethylenimine) (PEI), amino-containing doxorubicin, thiol-containing 5-((2-(and 3)-S-(acetylmercapto) succinoyl)amino) fluorescein and Texas Red-labeled streptavidin were used as model molecules for surface modification of F-127-NH2, F-127-COOH, F-127-NHS, F-127-MAL and F-127-Biotin-stabilized droplets, respectively. Results and Discussion: The above five derivatives of F-127 can act as surfactants to stabilize the droplet interface and prevent coalescence of both single and double emulsions, demonstrating that terminal modification of F-127 will not affect its inherent properties as a surfactant. Droplets with positively or negatively charged surface were produced when amino or carboxyl-terminated F-127 was used as the surfactant during the generation process in the microfluidic chip, respectively. Subsequently, dye-labeled anionic heparin and cationic PEI could coat the droplets by electrostatic interaction as evidenced by fluorescence signals on the surface of the droplets (Fig. 1A). The NHS and maleimide-modified droplets can anchor amino and thiol-containing model fluorescence dye on the surface via amidation and thiol-maleimide “click” reaction, respectively (Fig. 1B). In another scenario of modification, streptavidin could be attached to the surface of droplets stabilized with biotin-functionalized surfactant. The above three types of interaction/reaction are highly efficient and orthogonal, offering potential for multiple modifications simultaneously. To the best of our knowledge, this is the first example reported on surface modification of microfluidic droplets by using end-group-functionalized surfactants. Conclusion: We have developed a versatile and efficient platform for surface modification of microfluidic droplets based on functional F-127 surfactants. The present work also suggests that surface modification is a promising technique for fabricating microfluidic droplet-based multifunctional drug delivery systems with tunable surface properties. Support to this research by NIH and AO Foundation is acknowledged

Surface chemistry gradients on silicone elastomers for high-throughput modulation of cell-adhesive interfaces.

Combinatorial and high-throughput approaches to screening cell responses to material properties accelerate the speed of discovery and facilitate the identification of cell instructive cues or trends that may be missed by discrete sampling. However, these technologies have not yet been widely applied to materials with tissue-like stiffness. The fabrication of monotonically varying surface chemistry gradients on polydimethylsiloxane, an elastic biomaterial, and the influence of these engineered surfaces on protein adsorption and adherent cell morphology were explored in this study. Crosslinked networks of polydimethylsiloxane were functionalized with a hydrophobic self-assembled monolayer and then modified by spatiotemporally regulated ultraviolet ozonolysis to obtain gradients of oxygenated species ranging from ∼10° to ∼100° in water contact angle. Automated microscopy and image analysis of fibroblast cell morphology revealed a strong correlation between cell spreading and hydrophobicity. However, structural and functional analysis of the fibronectin interface indicated a proportional increase in cell spreading with adsorption, but a biphasic relationship with fibronectin conformation, underscoring the complexity of the adhesive interface. This work demonstrates the development of an elastomer surface modification platform that can be extended to future combinatorial studies of biological responses to chemical and mechanical material properties.

Platelet interactions with polyurethane nanocomposites: effect of organic modifier terminal functionality

Surface modification is a flexible approach for manipulating blood–material interactions with the advantage that many different forms of devices can be modified without changing the bulk material properties. This study hypothesises that organic modifiers (OMs) used to prepare silicates for incorporation into polyurethane (PU) nanocomposites can migrate and be expressed on the PU surface and directly affect biological interactions. Two OMs of equivalent chain length with COOH or CH3 end groups were used, and their surface expression was measured. Results suggested that surface expression occurred only in nanocomposites with methyl modified silicates. Platelet adhesion to the CH3 and COOH modified nanocomposites showed significantly lower adhesion on the CH3 nanocomposites. Similarly, platelet activation was lower on CH3 nanocomposites as indicated by morphological differences in degree of spreading. Finally, surface roughness showed little correlation between material type and platelet adhesion, indicating that roughness was not a significant factor influencing platelet interactions. This study proposes that a nanocomposite approach with migrating OMs can provide an elegant platform for surface modification of polymers for biomedical applications.

One-step preparation of vinyl-functionalized material surfaces: a versatile platform for surface modification

A simple approach has been developed to functionalize various substrates, such as gold and polyvinylchloride, with dopamine methacrylamide—a molecule with adhesive properties that mimic those of mussels—to produce a versatile and general platform for subsequent surface modification. With active double bonds on the surface, various polymers, such as poly([2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide (PMEDSAH) and poly(N-vinylpyrrolidone) (PVP), can be grafted by conventional radical polymerization. Double bond surface functionalization and subsequent polymer grafting have been verified by static water contact angle, Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements. Protein adsorption assays showed that the polymer-modified substrates have good protein-resistant properties. Considering the advantages of facility, versatility and substrate-independence, this method should be useful in designing functional interfaces for bioengineering applications.

Modulation of RGD-Functionalized Polyelectrolyte Multilayer Membranes for Promoting Osteoblast Function

Layer-by-layer deposition of polyelectrolyte multilayer (PEM) membranes has recently been applied successfully to a number of biomedical applications. This simple and versatile technique provides a broad surface modification platform, for example, for the display of biomolecules such as cell-adhesion peptides. In this work, we investigated the effects of PEM coatings on RGD-immobilization and osteoblast cell culture. RGD-containing peptides were conjugated to the amino groups of poly(allylamine hydrochloride) (PAH), and then adsorbed on top of 10-layer PAH/poly(acrylic acid) (PAA) multilayer membranes that were assembled at either pH 2.0 or pH 6.5. MG63 osteoblast-like cells were then seeded and cultured on the RGD-conjugated surfaces. We found that the cells adhered to and grew better on the RGD-conjugated PEM membranes. Furthermore, the cells grew better on the RGD-conjugated PEM coatings assembled at pH 6.5 than those assembled at pH 2.0. On the other hand, MG63 cells exhibited better differentiated phenotype on the pH 2.0 coatings compared to the pH 6.5 coatings with respect to alkaline phosphatase activity and calcium deposition, while cells did not express osteoblast phenotype on the PAH surfaces. These results clearly show that the base PEM membranes play an important role in RGD-immobilization and osteoblast functions.

Selective surface modification of free-standing polysaccharide nanosheet with micro/nano-particles identified by structural color changes

The chemical and physical modification of a material surface is important for practical applications. In this study, we utilized the bilateral nature of a free-standing polysaccharide nanosheet as a platform for surface modification, selectively modifying the upper and lower surfaces with different sizes of latex beads. By means of a water-soluble sacrificial layer, we adsorbed latex beads with the diameter of 200 nm onto the obverse surface of the polysaccharide nanosheet as well as latex beads with that of 2 μm onto the reverse side. The optical characteristics of the nanosheet were analyzed on the basis of ‘thin film interference theory’ by making stepwise increments in thickness through sequentially overlaying free-standing 30-nm polysaccharide nanosheets onto a SiO 2 substrate. The surface of the polysaccharide nanosheet was quite flat and smooth. Having confirmed by optical and scanning electron microscopy that we had achieved selective surface modification of the polysaccharide nanosheet with micro/nano-latex beads, we noted a unique optical property when the nanosheet was adsorbed on the SiO 2 substrate. The localization of the beads on the nanosheet surface produced structural colors in the films due to an optical interference. This selective surface modification technique will be utilized to create ‘smart’ nanocomposites possessing different surface functions.