Surface Grafting Technique Research Articles

Amidoxime functionalized mesoporous silica nanoparticles for pH-responsive delivery of anticancer drug

Abstract In recent decades, nanomedicine has attracted much attention at the forefront of nanotechnology, gaining great expectations in the biomedical sectors. Among various nanomaterials, silica nanoparticles-based drug delivery is considered effective owing to their physicochemical stability and biological compatibility. Surface grafting and chemical conversion techniques were used to create an amphoteric functional ligand known as amidoxime ligand (AL) modified mesoporous silica material (MS-AL NPs). With this technique, amidoxime ligand groups can be introduced in greater concentration to the silica surface without compromising its structure. The active surface allows for surface functionalization and integration of medicinal substances. They are widely employed in the bio-medical industry for diagnostics, target administration of drugs, bio-sensing, cellular absorption, and so on. The function of the produced MS-AL NPs as a regulated drug delivery system was studied utilizing doxorubicin (Dox) as a model anticancer drug. Using the MCF-7 cell line, the biocompatibility and cellular uptake characteristics were investigated. Considering all factors, the MS-AL NPs may be used as pH-responsive drug carriers in cancer treatment applications.

Protein-polymer bioconjugation, immobilization, and encapsulation: a comparative review towards applicability, functionality, activity, and stability.

Polymer-based biomaterials have received a lot of attention due to their biomedical, agricultural, and industrial potential. Soluble protein-polymer bioconjugates, immobilized proteins, and encapsulated proteins have been shown to tune enzymatic activity, improved pharmacokinetic ability, increased chemical and thermal stability, stimuli responsiveness, and introduced protein recovery. Controlled polymerization techniques, increased protein-polymer attachment techniques, improved polymer surface grafting techniques, controlled polymersome self-assembly, and sophisticated characterization methods have been utilized for the development of well-defined polymer-based biomaterials. In this review we aim to provide a brief account of the field, compare these methods for engineering biomaterials, provide future directions for the field, and highlight impacts of these forms of bioconjugation.

Constructing a Photothermal and Quaternary Ammonium Cation Bactericidal Platform onto SEBS for Synergistic Therapy.

Poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) with eminent elasticity, thermoplastic ability, and biological stability has aroused great interest in the medical area. However, bacteria can easily adhere to the hydrophobic SEBS surface to cause medical device-related infections. In this work, SEBS is modified to prepare the SEBS-polydopamine (PDA)-poly(lysine) quaternary ammonium derivative (PLQ) antibacterial surface by PDA deposition and surface grafting techniques to solve bacterial infections. PDA is used as an intermediate layer and presents an excellent photothermal effect. The grafted polymer PLQ has antimicrobial quaternary ammonium cation groups, which plays synergistic bactericidal therapy with PDA. The SEBS-PDA-PLQ surface almost totally suppresses the growth of bacteria with a surface bacterial survival rate of 0.05% under laser irradiation. The outstanding antibacterial activity of the SEBS-PDA-PLQ surface is attributed to the synergistic effects of the photothermal performance of PDA and quaternary ammonium cationic functional groups of PLQ. In addition, the membrane SEBS-PDA-PLQ shows good hydrophilicity, antiprotein adsorption ability, chemical stability, and biocompatibility. This antibiotic-free antimicrobial approach has great potential for practical application in solving infections associated with medical devices.

Toughening colloidal gels using rough building blocks

Colloidal gels, commonly used as mesoporous intermediates or functional materials, suffer from brittleness, often showing small yield strains on the order of 1% or less for gelled colloidal suspensions. The short-range adhesive forces in most such gels are central forces—combined with the smooth morphology of particles, the resistance to yielding and shear-induced restructuring is limited. In this study, we propose an innovative approach to improve colloidal gels by introducing surface roughness to the particles to change the yield strain, giving rise to non-central interactions. To elucidate the effects of particle roughness on gel properties, we prepared thermoreversible gels made from rough or smooth silica particles using a reliable click-like-chemistry-based surface grafting technique. Rheological and optical characterization revealed that rough particle gels exhibit enhanced toughness and self-healing properties. These remarkable properties can be utilized in various applications, such as xerogel fabrication and high-fidelity extrusion 3D-printing, as we demonstrate in this study.

Research Progress on the Modification Methods of Clay Minerals

Clay minerals are widely distributed in nature, and their applications have been rapidly developed in the last decade or so due to their unique physical and chemical properties. Since the most researched is the modification of clay minerals, this paper introduces the types of clay, basic structural characteristics and common modification methods. The methods of modified clay include high-temperature excitation and acid-base excitation methods to stimulate the activity of clay minerals, as well as interlayer ion exchange modification methods, clay surface grafting techniques such as sol-gel method, surface hydroxyl grafting modification and other methods, and also introduces the intercalation methods, including solution intercalation method, In situ polymerization intercalation method, etc. The applications and developments of clay minerals are summarized, from traditional industrial applications to environmental protection and high-tech nanomaterials, mainly in the automotive industry, environment-friendly materials and catalysts.

ADVANCES IN TECHNIQUES AND APPLICATIONS OF RUBBER SURFACE GRAFTING MODIFICATION

ABSTRACT To meet the requirement in the application of medical devices, composites, biomaterials, corrosion resistance, and selective adsorptions, rubber surface modification is usually indispensable. Grafting treatment is one of most significate treatment methods. In this paper, we focus on rubber surface grafting modification, including grafting techniques and applications. Different grafting methods—including monomer grafting polymerization and coupling reaction—are covered and compared briefly. The related applications of surface grafting modification techniques, such as improving compatibility of waste rubber as fillers, hydrophobicity and lipophilicity of sponge rubber for oil–water separation, biocompatibility of rubber in the medical field, and forming surface patterns, are demonstrated in detail. The new research directions of surface grafting techniques as well as main challenges in application are also discussed.

Immobilizing Bactericides on Dental Resins via Electron Beam Irradiation

Polymerizable bactericides, such as quaternary ammonium compound–based monomers, have been intensively studied as candidates for immobilizing antibacterial components on dental resin. However, they predominantly exhibit a bacteriostatic behavior, rather than bactericidal, as the immobilized components are left with insufficient molecular movement to disrupt the bacterial surface structure through contact-mediated action. In this study, we developed a novel strategy to increase the density of the immobilized bactericide and enhance its antibacterial/antibiofilm properties by combining a surface-grafting technique with electron beam irradiation. A solution of the quaternary ammonium compound–based monomer, 12-methacryloyloxydodecylpyridinium bromide (MDPB), was coated on polymethyl methacrylate (PMMA) resin specimens at the concentrations of 30, 50, and 80 wt%. The coated resins were subsequently exposed to 10 MeV of electron beam irradiation at 50 and 100 kGy, followed by thermal stabilization at 60 °C. The antibacterial effect was evaluated by inoculating a Streptococcus mutans suspension on the coated PMMA resin samples, which exhibited bactericidal effects even after 28 d of aging (P < 0.05, Tukey’s honestly significant difference test). Transmission electron microscopy and bacteriolytic activity evaluation revealed that the S. mutans cells had sustained membrane depolarization. Furthermore, the antibiofilm effects against S. mutans and bacteria collected from human saliva were assessed. The thickness and the percentage of membrane-intact cells of the S. mutans and multispecies biofilms formed on the MDPB-immobilized surfaces were significantly lower than the uncoated PMMA specimens, even after 28-d aging (P < 0.05, Tukey’s honestly significant difference test). Thus, the immobilization of antibacterial MDPB via electron beam irradiation induced rapid membrane depolarization, increasing membrane permeability and eventually causing cell death. Our strategy substantially enhances the antibacterial properties of the resinous materials and inhibits biofilm formation, therefore demonstrating significant potential for preventing infectious diseases in the oral environment.

Large scale synthesis of silane functionalized near-superhydrophobic aluminium hydroxide particles via facile surface grafting technique

Herein, we report a facile, large-scale synthesis approach to develop near-superhydrophobic crystalline single phase aluminium hydroxide (Al(OH)3/AH) particles via surface-grafting mediated functionalization using vinyltrimethoxysilane. The obtained XRD pattern and ATR-IR spectrum of the functionalized-AH (F-AH) showed the characteristic peaks corresponding to the existence of silane. The room temperature water contact angle (WCA) measurements revealed that the hydrophilic surface of AH (32.2°) is switched to near-superhydrophobic surface after the functionalization with WCA of 137.4°. Furthermore, the temperature dependent WCA studies at lower (∼10 °C), middle (∼50 °C) and higher temperatures (∼80/90 °C) showed that the silane-functionalization is stable and provides temperature independent near-superhydrophobic surface.

Study on wettability of plasma spray coated oxide ceramic for hydrophobicity

Many industrial applications require hydrophobic surfaces with high-temperature compatibility. Ceramic surfaces, which have excellent endurance for high-temperature, are generally hydrophilic. For such applications, the required hydrophobicity is induced in ceramic surfaces with suitable polymeric agents by using different surface grafting techniques. To avoid the costly grafting process, suitable hydrophobic ceramic surfaces have to be designed for direct use in such applications. Rare earth oxides show hydrophobicity due to their electronic configurations. Hence, for the selection of hydrophobic ceramic material for real engineering components, three plasma spray-coated surfaces have been characterized for their water contact angle. In this study, yttria (Y2O3) was used as a rare earth oxide along with yttria stabilized zirconia (YSZ) and alumina (Al2O3) for comparison of surface properties. The dependence of contact angle on various experimental parameters was established. It was observed that cleaning with water induces temporary hydrophobicity in alumina even after baking at 180 °C. Yttria coating was found to be distinctly hydrophobic with the contact angle more than 115°. The hydrophobic behaviour of yttria was found to be permanent and does not degrade with environmental exposure. The apparent surface energies of the samples were estimated based on acid-base theory. The apparent surface energies of the studied samples were found to be in the range of 35 mJ/m2 to 42 mJ/m2.

Amine-modified kaolinite clay preserved thyroid function and renal oxidative balance after sub-acute exposure in rats.

Kaolinite clay is an abundant natural resource in Nigeria with several industrial applications. Incidentally, the wide-scale use of kaolinite clay is hampered by its small surface area. The objective of this study was to assess the effects of amine-modified clay on electrolyte, thyroid, and kidney function markers. Modification of kaolinite clay with an amine functional group was achieved using surface grafting technique. Characterization with a scanning electron microscope and Brunauer-Emmett Teller surface area analyzer confirmed this modification. However, there is sparse information on the effect of amine-modified kaolinite clay on electrolyte homeostasis, thyroid, and renal function. Rats were administered amine-modified kaolinite clay at the doses of 1, 2, and 5mg/kg body weight. After 14days of repeated-dose treatment, there were no significant changes in levels of albumin, uric acid, triiodothyronine, thyroxine, ratio of triiodothyronine to thyroxine, and relative kidney organ weight. Furthermore, there were no changes in the concentration of potassium, although amine-modified kaolinite clay significantly decreased sodium, calcium, and total cholesterol levels. Amine-modified kaolinite clay, at all treatment doses, also preserved the renal histoarchitecture and oxidative balance in rats. This study reports on the effect of amine-modified kaolinite clay on renal markers and thyroid function, and further deepens our understanding of their biochemical action. This baseline data may boost the prospect of using amine-modified kaolinite clay in the treatment of contaminated water.

Highly Selective Electrochemiluminescence Sensor Based on Molecularly Imprinted-quantum Dots for the Sensitive Detection of Cyfluthrin.

A highly selective and sensitive molecularly imprinted electrochemiluminescence (MIECL) sensor was developed based on the multiwall carbon nanotube (MWCNT)-enhanced molecularly imprinted quantum dots (MIP-QDs) for the rapid determination of cyfluthrin (CYF). The MIP-QDs fabricated by surface grafting technique exhibited excellent selective recognition to CYF, resulting in a specific decrease of ECL signal at the MWCNT/MIP-QD modified electrode. Under optimal conditions, the MIECL signal was proportional to the logarithm of the CYF concentration in the range of 0.2 µg/L to 1.0 × 103 µg/L with a determination coefficient of 0.9983. The detection limit of CYF was 0.05 µg/L, and good recoveries ranging from 86.0% to 98.6% were obtained in practical samples. The proposed MIECL sensor provides a novel, rapid, high sensitivity detection strategy for successfully analyzing CYF in fish and seawater samples.

Preparation of PEGylated poly(vinylidene fluoride) porous membranes with improved antifouling property

Antifouling poly(vinylidene fluoride) (PVDF) porous membranes have been fabricated via blending method with poly(ethylene glycol) (PEG)-containing additives and surface grafting technique. Although, it is still a great challenge to simplify the modification processes. Here, a simple process is introduced to fabricate antifouling PVDF porous membranes based on the in situ cross-linking polymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA) in the casting solutions and the classical non-solvent induced phase separation (NIPS) technique. The surface chemical compositions of the prepared PEGylated PVDF membranes were characterized by x-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The results confirmed that poly(PEGMA) (PPEGMA) chains have been synthesized and immobilized on the membrane surfaces, leading to enhanced hydrophilicity. With increasing PEGMA content, the membrane surfaces changed from the slim fiber-like structure to the sheet morphology with large roughness, meanwhile the finger-like structure elongated in terms of the cross-section morphology. Furthermore, after introducing PPEGMA chains, the flux recovery rate increased to 90.3 ± 2.8% after 3 cycles, indicating improved antifouling ability. The present work provides a convenient method for fabrication antifouling porous membranes for water treatment and purification in large scale.

Poly(lactide-co-glycolide) grafted hyaluronic acid-based electrospun fibrous hemostatic fragments as a sustainable anti-infection and immunoregulation material.

Poly(lactide-co-glycolide) (PLGA) copolymers are promising synthetic materials in the biomedical field. However, in wound management, their hydrophobic properties limit their further application because of their poor adhesion to the surface of moist wounds. Furthermore, the lack of hemostatic materials with sustainable anti-infection and immunoregulation functions remains a highly significant clinical problem, as commercially available hemostatic products, such as Arista™, Celox™ and QuikClot™, do not have sufficient infection prevention and immunoregulation properties. Herein, we employ electrospinning, ammonia dissociation and surface grafting techniques to develop a series of PLGA-based hemostatic materials, including a PLGA electrospun fibrous membrane, PLGA-NH2 fibrous particles and PLGA-hyaluronic acid fibrous fragments (PLGA-HA FFs). Notably, we load azithromycin on the PLGA-HA FFs to endow them with anti-infection and immunoregulation properties. The hemostatic mechanism analysis demonstrates that the PLGA-HA FFs show superior hemostasis performance compared to traditional gauzes. The results show that the PLGA-HA FFs can act as a versatile platform with high encapsulation of azithromycin (83.03% ± 2.81%) and rapid hemostasis (28 ± 2 s) as well as prominent cytocompatibility towards L929 cells, RAW 264.7 cells and red blood cells. We believe that the current research proposes a possible strategy to synthesize materials that achieve not only safe and effective hemostasis, but also have anti-infection and immunoregulation properties for the development of further hemostatic products.

Development of a selective fluorescence nanosensor based on molecularly imprinted-quantum dot optosensing materials for saxitoxin detection in shellfish samples

Abstract A new type of molecularly imprinted silica layers appended to quantum dots (MIP-QDs) for saxitoxin (STX) was fabricated through the surface grafting technique. The MIP-QDs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FT-IR), and imprinting and selective fluorescence quenching properties in different solutions. Results demonstrated that the synthesized MIP-QDs exhibited excellent selective fluorescence quenching to STX because of the complementary imprinted cavities on the surface of MIP-QDs. Furthermore, a fluorescence nanosensor based on MIP-QDs was fabricated for the selective detection of STX under optimal experimental conditions. A good linear relationship in the range of 20.0-100.0 μg/L with a correlation coefficient of 0.9988 was obtained. Excellent recoveries ranging from 89.4% to 102.4% with the RSD below 6.3% were obtained for the shellfish samples at three spiked levels of STX. The detection limit of STX in shellfish samples was 0.3 μg/kg. The results indicated that the developed fluorescence nanosensor was highly selective and sensitive enough to detect STX in shellfish samples.

Poly(vinylphosphonic acid) adsorbed onto chromium (III) oxide/hydroxide colloid as a model surface for polymer modified stainless steel

Use of 316L stainless steel, with its highly stable chromium oxide passive layer, is ubiquitous in medical and food industry environments. There is little data in the literature on the ability of stainless steel to absorb multifunctional polymer layers which might impart different surface properties. Current research in this area focuses on layer by layer deposition and surface grafting techniques which are possibly too expensive and slow outside of the laboratory. The development of an absorbable polymer system is more favourable, but requires sufficiently adhesive functional groups which anchor the polymer to the surface and remain robust under aqueous conditions.A screen of likely binding groups showed that polyphosphonates were the most promising in terms of binding stability. To gain a better understanding of the binding mechanisms and adhesive tenacity of the trial polymers onto stainless steel a model surface of a chromium oxide colloid was used. In-situ attenuated total reflection infrared spectroscopy with real time monitoring of the formation of metal oxide surface complexes was used to follow the kinetics of the binding and desorption. This also provided meaningful quantitative data on complex formation, and possible identification of the binding modes present at the metal oxide surface groups.

Surface grafting of poly(pentafluorostyrene) on the iron and iron oxide particles via reversible addition fragmentation chain transfer (RAFT) polymerization

ABSTRACTA surface grafting technique is reported for synthesis of poly(pentafluorostyrene) via reversible addition fragmentation chain transfer onto iron (iron oxide) particles. 4‐Methoxydithiobenzoate is used for the RAFT chain transfer agent. The molecular weight, surface morphology, thickness, thermal properties, and monomer conversion of the grafted polymer are reported. The grafted poly(pentafluorostyrene)–iron particles show a higher thermal transition temperature compared to the nongrafted polymer because it is speculated that the covalent bond between the polymer backbone and the surface of the iron particles restricts the molecular mobility. The monomer conversion increases in proportion to the amount of chain transfer agent (CTA) concentration at early polymerization time. The grafted poly(pentafluorostyrene) shows a “hairy” like polymer architecture with fibril thickness in the range of 80 to 100 nm. A thin coating is expected to maintain the magnetic saturation properties of iron particles. To the best of our knowledge, this is the first time that poly(pentafluorostyrene) has been grafted onto the iron particles utilizing RAFT and 4‐methoxydithiobenzoate as a CTA. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44898.

HIPEs template: Towards the synthesis of polymeric catalysts with adjustable porous structure, acid–base strength and wettability for biomass energy conversation

Due to its widely available, inexpensive, renewable and carbon–neutral properties, biomass of cellulose is considered to be the most promising candidate to produce 5-hydroxymethylfurfural (HMF). In this work, high internal phase emulsions (HIPEs) templating methodology, subsequent ion-exchange, and the surface grafting technique are combined to synthesize macroporous, acid–base bifunctional, and superhydrophobic polymeric solid catalyst for the production of HMF from cellulose in a one-pot manner. The catalyst are well characterized by field emission scanning electron microscopy, fourier transform infrared spectroscopy, 13C solid-state nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, pyridine fourier transform infrared spectroscopy and NH3/CO2 temperature-programmed desorption. Results of characterization demonstrated that the as-prepared catalyst possesses average void diameter at 12.5μm, interconnecting pore diameter at 2.8μm, contact angle at 150°, acid strength at 3.034mmolg−1 and base strength at 1.379mmolg−1, respectively. By simply varying the parameters of HIPEs templates (i.e., the volume fraction of the internal phase and surfactant concentration), the molar ratio between acid/base monomer and the grafted amount of 1-dodecanethiol, the pore structure, acid and base strengths, wettabilities of catalyst can be easily adjusted. Results of catalytic experiments involving cellulose-to-HMF conversion indicated that as-prepared catalyst can effectively improve the reaction rate, increase the HMF yield and prohibit the hydration of HMF to by-products. And remarkable HMF yield of 49.5% and selectivity of 55.9% can be obtained from 100mg cellulose under the optimal conditions. Furthermore, catalyst can be easily recovered and reused at least five times without significant loss of catalytic activity. This work represents a continuation of efforts for fabrication and application on multi-functional heterogeneous catalyst for excellent conversion of one-pot cellulose to HMF.

Synthesis and characterization of Fe3O4/poly(lactide‐co‐glycolide) composite and its coating effects on magnesium alloy

The Fe3O4/poly(lactide‐co‐glycolide) (PLGA) composites were prepared via a surface grafting technique. Initially, the poly(lactic acid) oligomer was synthesized and surface‐grafted to Fe3O4 nanoparticles. Then, the grafted Fe3O4 particles were compounded with PLGA matrix by a simple solution blending method. The grafted Fe3O4 particles presented enhanced compatibility with PLGA matrix and the composites indicated enhanced dynamic mechanical performance. Electrochemical tests showed that the Fe3O4/PLGA composite coating can help improve the impedance of magnesium samples by 100–300%, and the impedance of the metal may be tunable by altering the components ratio of LA/GA within PLGA matrix. The composites may have potential application for magnesium alloy used in degradable medical implants. POLYM. COMPOS., 37:1369–1374, 2016. © 2014 Society of Plastics Engineers

Selective adsorption of lead(II) from aqueous solution by ion-imprinted PEI-functionalized silica sorbent: studies on equilibrium isotherm, kinetics, and thermodynamics

A new ion-imprinted poly(ethyleneimine)(PEI)-functionalized silica sorbents were synthesized by a hydrothermal-assisted surface grafting technique with Pb(II) as the template, PEI as the functional molecular, and epichlorohydrin as the cross-linking agent for the selective adsorption of Pb(II) from aqueous solution, and was characterized by FTIR, SEM, TGA-DTA, nitrogen adsorption, and the static batch experiment. Static adsorption experiment results showed that Pb(II)-imprinted PEI-functionalized silica sorbents had high static adsorption capacity of 60.4 mg g−1, reached an equilibrium state within 20 min, displayed stable adsorption ability for Pb(II) ions in the range of pH 4–8, had satisfactory selectivity toward Pb(II) and could be used repeatedly. Compared with Freundlich and Dubinin–Radushkevich isotherms, equilibrium data fitted to Langmuir adsorption model. The kinetic process of adsorption followed a pseudo-second-order model compared to pseudo-first-order, Elovich and intraparticle diffusion models. Negative values of ΔG° indicated spontaneous adsorption and the degree of spontaneity of the reaction increased with increasing temperature. Positive values of ΔH° showed that the adsorption process was endothermic in the experimental temperature range. The results indicated that Pb(II)-imprinted PEI-functionalized silica sorbents could be employed as an effective material for the selective adsorption of Pb(II) ions from aqueous solutions.

Adsorption of lead(II) from aqueous solution using a poly(ethyleneimine)‐functionalized organic–inorganic hybrid silica prepared by hydrothermal‐assisted surface grafting method

ABSTRACTThe poly(ethyleneimine) (PEI)‐functionalized organic–inorganic hybrid silica was prepared by a hydrothermal‐assisted surface grafting technique. Static adsorption experiment results showed that PEI‐functionalized hybrid silica had high static adsorption capacity of 68.1 mg g−1, which was 1.3 times as much as that of the sorbents by conventional heating method. PEI‐functionalized hybrid silica displayed stable adsorption ability for Pb(II) ions in the range of pH 4–8. An equilibrium state was reached within 30 min. Freundlich and Langmuir adsorption isotherm models were used to fit the equilibrium data, and it was found that the Langmuir adsorption model provided good fit. Kinetic studies indicated that the adsorption followed a pseudo‐second‐order model. Various thermodynamic parameters, such as ΔGo, ΔHo and ΔSo, were evaluated with results indicating that this system was a spontaneous and endothermic process. The results indicated that PEI‐functionalized hybrid silica could be employed as an effective material for the adsorption of Pb(II) ions from aqueous solutions. © 2014 Curtin University of Technology and John Wiley &amp; Sons, Ltd.