Vinculin focal adhesion of osteoblast‐like cells on PEEK coated with ultra‐thin polymer nano films

PEEK is the polymer of choice to replace metal encapsulants and other parts in active medical implants fixated into bone. The current challenge is to improve its biocompatibility with bone tissue to ultimately achieve osseointegration. PEEK sheets surfaces coated with plasma deposited nano thin polymer films using CH₄, (CH₄ + O₂) and (CH₄ + N₂) gases. PEEK samples plasma treated with nonpolymerizing gases (O₂) were also used for comparison. The adhesion performance of osteoblast like cells on the plasma‐treated PEEK surfaces and the presence of Vinculin in these cells were evaluated after long culturing period (12 days). X‐ray photoelectron spectroscopy and Auger spectroscopy were used to provide surface molecular information, surface hardness and molecular density. All plasma‐treated surfaces retained functionality after the sterilization process. PEEK surfaces with high number of oxygen functional groups and particularly oxygen rich thin polymer coating (plasma deposition using CH₄+O₂ gas mixture) resulted in strong cellular adhesion strength and large Vinculin amount. Further, osteoblast‐like cells responded better to surfaces with lower molecular density acting like another signal for cell adhesion. The osteoblast‐like cells response was weaker for surfaces with both thin films with nitrogen functional groups and nonfunctional (nonpolar) films. Furthermore, thin films rich in nitrogen functional groups repelled the cells, showed abnormal cells shape, smaller Vinculin amount and induced thicker cellular clusters with poor spread. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42181.     

Synthesis of biomimetic hyperbranched zwitterionic polymers as targeting drug delivery carriers

Novel biomimetic hyperbranched copolymers that synthesized by polymerization of zwitterionic monomer (CBB) on the surface of a hyperbranched poly(3‐ethyl‐3‐(hydroxymethyl)oxetane) (HBPO) core and used as a drug delivery carrier have been investigated by analysis of protein‐adsorption‐resistance, cytotoxicity and cell type‐specific targeting properties. The as‐synthesized biomimetic hyperbranched copolymers showed low toxicity, favorable protein resistant properties and were ultrastable in 100% fetal bovine serum. Folic acid and rodiamin‐B were conjugated to the surface of synthesized micelles to endow it with target drug delivery and fluorescence activity, respectively. Intracellular uptake and in vitro cytotoxicity of HBPO‐poly(carboxybetaine) micelles were investigated. Doxorubicin was used as a model drug for Hela cells during the experiment. All results show that the biomimetic hyperbranched copolymer is a candidate carrier for target drug delivery. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Self‐segregating hyperbranched polymer/silver nanoparticle hybrids in thermoplastic polyurethane films

Self‐segregating hyperbranched polymer (HBP) additives have been utilized to concentrate silver nanoparticles (AgNPs) at the air interface of polyurethane films. The limited spontaneous surface migration of the AgNPs was enhanced through the addition of appropriately functionalized HBPs. Both amine and thiol terminated additives were employed to allow interaction of the HBP with the nanoparticles. Both types of additives increased surface concentration of silver modestly, though the thiol‐terminated HBPs demonstrated nearly a seven‐fold enhancement of surface migration. It was also found that wholly‐aliphatic HBPs demonstrated only slightly reduced ability to bias AgNP concentration as compared to HBPs functionalized with perfluorinated chains. In addition, films containing 1% total silver concentration were tested for antimicrobial activity using the ASTM‐E 2180 protocol. Significant reduction of the microorganisms was observed for all samples, 6‐log reduction was achieved for the gram‐negative bacteria P. aeruginosa, the gram‐positive bacteria S. aureus, and the fungi C. albicans. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The effect of curvature on chondrocytes migration and bone mesenchymal stem cells differentiation

Numerous cells grow in columnar tissues and organs with different curvatures and curvature gradients. Therefore, it is necessary to study the effect of curvature on cell behavior to control and promote cell development. Herein, we prepared polydimethylsiloxane (PDMS) with different micro-nano patterns using ultraviolet soft lithography. Hydrophilic polydopamine (PDA) was modified on the PDMS surface to prepare PDMS/PDA to improve its biocompatibility. The PDMS/PDA was characterized by contact angle tester and scanning electron microscopy (SEM). The effect of curvature on bone cell migration and differentiation was studied through SEM, inverted phase contrast microscope and fluorescence microscopy. We found that different curvatures had different effects on the bone cell migration and differentiation. Chondrocytes migrated rapidly in grooves with a curvature range of 1/575–1/875 μm⁻¹. Bone mesenchymal stem cells (BMSCs) had high efficiency of differentiation into chondrocytes in the grooves with a curvature range of 1/775–1/1375 μm⁻¹. Furthermore, BMSCs showed high efficiency of differentiation into chondrocytes at the edges of micro-nano patterns with different perimeter curvatures, and the differentiation efficiency was the highest at 120° convex curvature. This work shows that curvature is a principle to be considered in bone tissue regeneration engineering and provides inspiration for future biomaterials design.     

Reliable surface modification of dental plastic substrates to reduce biofouling with a photoreactive phospholipid polymer

Plastic substrates have been widely applied in clinical settings for dental treatments. These substrates should be strong enough for long‐term implantation in the oral cavity and should be resistant to biofouling. We developed a new photoreactive phospholipid polymer to reduce biofouling on dental plastics via a photochemical reaction. Poly(methyl methacrylate) (PMMA) and poly(ether ether ketone) (PEEK) were used as dental plastics. To determine the antibiofouling properties on the polymer surface, the phospholipid polymer was covalently immobilized on the substrates by UV irradiation. We evaluated the antibiofouling properties by observing the protein adsorption and cell and bacterial adhesion. Significant protein adsorption and cell adhesion appeared on the bare PMMA and PEEK substrates but decreased dramatically after surface modification with the phospholipid polymer. Thus, this photoreactive polymer shows potential for conferring dental plastics with antibiofouling properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46512.     

Effects of the surface modification of poly(amino acid)/hydroxyapatite/calcium sulfate biocomposites on the adhesion and proliferation of osteoblast‐like cells

In this study, we focused on the surface modification of a novel poly(amino acid) (PAA)/hydroxyapatite/calcium sulfate composite and the effect of its surface modification on cellular responses. The surface modification was performed by sandblasting (sample S2), calcium chloride ethanol saturated solution etching (sample S3), and formic acid etching (sample S4) followed by in vitro culturing of osteoblast‐like cells. The obtained results indicate that a new interface of the composite was formed during the modification, and the modified surface was changed with respect to its surface morphology by physical abrasion. The calcium chloride ethanol saturated solution etchant etched PAA selectively whereas forming rich calcium‐phosphate (Ca–P) apatite on the surface of S3. The formic acid etchant attacked the inorganic component without changing the PAA state. Cell attachment and cell proliferation were improved by the treatments of S2 and S3 in comparison with no treatment and the treatment of S4 © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42427.     

Synthesis of a photoimmobilizable histidine polymer for surface modification

A novel photoreactive polymer with histidine polar groups was synthesized through the copolymerization of two types of methacrylic acid, one carrying histidine groups and the other carrying azidoaniline groups. The polymer was photoimmobilized on polyester disks for surface modification. The effect of the surface modification on the hydrophilic and biofouling properties was investigated. Static contact angle measurements showed that the polymeric surface was modified to be comparatively hydrophilic in the polymer‐immobilized region. Micropattern immobilization was carried out with a photolithographic method. Atomic force microscopy measurements showed that the polymer was formed on the disks in response to ultraviolet irradiation. Protein adsorption was reduced on the polymer‐immobilized regions, and in those regions, spreading and adhesion of mammalian cells were reduced in comparison with that in nonimmobilized regions. In conclusion, a novel histidine‐containing polymer was photoreactively immobilized on a conventional polymer surface, and it had reduced interaction with proteins and cells. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Aminating modification of viscose fibers and their CO2 adsorption properties

An adsorbent for CO₂ capture was prepared by the grafting of acrylonitrile (AN) onto viscose fibers (VFs); this was followed by amination with triethylene tetramine (TETA). The effects of the reaction conditions, such as the concentrations of the monomer, initiator, and nitric acid, on the grafting degree and grafting efficiency were studied. The adsorption performance of the adsorbent for CO₂ was evaluated by fixed‐bed adsorption. The highest dynamic adsorption capacity of the adsorbent for CO₂ was 4.35 mmol/g when the amine content of the adsorbent VF–AN–TETA reached 13.21 mmol/g. Compared with the polypropylene (PP)‐fiber‐based adsorbent (PP–AN–TETA), VF–AN–TETA with hydroxyl groups on the fibers facilitated the diffusion of CO₂ and water and led to a higher CO₂ adsorption capacity than that of PP–AN–TETA. The VF–AN–TETA adsorbent also showed good regeneration performance: its CO₂ adsorption capacity could still retain almost the same capacity as the fresh adsorbent after 10 adsorption–desorption cycles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42840.     

Tunable morphology and resistivity of ternary polymer composites of carbon black/low density polyethylene/ethylene-vinyl acetate with carbon blacks having different surface properties

Medium to extra-high voltage electrical cables typically comprise a semiconductive polymer composite layer to homogenize the electromagnetic field through the cables. The semiconductive layers usually contain a high content of carbon black (CB) for reduced electrical resistivity. In this study, we found that both the morphology and resistivity of a ternary polymer composite of CB/low density polyethylene (LDPE)/ethylene-vinyl acetate (EVA) depend on CBs used and the order of addition. Three types of CB were investigated. CB-A, which has the lowest surface energy and the most uniform surface energy profile, exhibits a strong affinity to LDPE and always segregates in the LDPE phase whether it is first added in the LDPE phase or the EVA phase. CB-B and CB-C, which have higher and less homogeneous surface energies, distribute differently with different orders of addition. We observe a significant reduction in the percolation threshold of CB-A in the CB/LDPE/EVA composite, but not with CB-B or CB-C. Adding CB-A in the LDPE phase first results in substantially lower resistivity than adding it in the EVA phase first, whereas adding CB-B or CB-C in the LDPE phase first results in higher resistivity than adding them in the EVA phase first.     

Encapsulation and delivery of protein from within poly(sulfobetaine) hydrogel beads

Advancement of therapeutic protein therapies can be hindered by their poor stability and short in vivo half-life. There is emerging evidence that biocompatible zwitterionic materials can prevent nonspecific interactions within proteins systems that contribute to protein instability. Here, zwitterionic hydrogel beads are synthesized from poly(sulfobetaine methyl methacrylate), pSB, using an inverse emulsion, free radical polymerization reaction technique. The transport properties within the zwitterionic hydrogels were characterized using ¹H NMR diffusometry. Equilibrium water content as high as 0.90 was measured for the synthesized hydrogels. Our study revealed that the pSB hydrogels are nontoxic, ion responsive, and their swelling is temperature dependent. The zwitterionic hydrogel beads were capable of undergoing lyophilization without aggregation. Hydrogel beads were loaded with a model protein, bovine serum albumin (BSA), using a postfabrication loading technique. The protein loading was studied using confocal laser microscopy, indicating homogenous protein dispersion of up to 40 μg BSA/mg hydrogel within the beads. Furthermore, the release rate of the protein from the synthesized hydrogel was studied at different crosslinker to monomer ratios. The protein encapsulated within the zwitterionic hydrogel had slower rates of thermal aggregation compared to nonencapsulated protein in solution. Furthermore, the protein-loaded inside the zwitterionic hydrogel better maintained its bioactivity.     

Improvement of the short‐ and long‐term mechanical properties of injection‐molded poly(etheretherketone) and hydroxyapatite nanocomposites

Nanocomposites of polyetheretherketone (PEEK) and hydroxyapatite (HA) nanoparticles treated with a silane coupling agent were successfully prepared by twin screw extrusion and injection molding. Some of the samples were annealed after the injection molding. The silane treatment promoted an improvement of the short‐ and long‐term mechanical properties of the nanocomposites. A higher stress and a six times higher deformation at break and a higher impact strength were observed in the silane‐treated nanocomposites when compared to the nontreated ones. The number of cycles to fail of the treated nanocomposites was almost 200% higher than the number of cycles to fail of the nontreated samples. The treatment also decreased the glass transition temperature and amount of crystallinity of the samples. This improvement in mechanical properties obtained from the silane treatment was attributed to the strengthening of the PEEK/HA interfacial bond, to the plasticization of the PEEK matrix by silane oligomers produced during the processing and to a better dispersion of the HA nanoparticles within the PEEK matrix. Samples annealing, however, diminished all these properties due to the increase in crystallinity. Studies of the short‐ and long‐term mechanical properties of these nanocomposites under physiological conditions and of the proliferation of stem cells are under way. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44476.     

Preparation,surface wetting properties,and protein adsorption resistance of well‐defined amphiphilic fluorinated diblock copolymers

Novel well‐defined amphiphilic fluorinated diblock copolymers P(PEGMA‐co‐MMA)‐b‐PC₆SMA were synthesized successfully by RAFT polymerization and characterized by FTIR, ¹HNMR and GPC. For copolymer coatings, static contact angles, θ, with water (θ_water ≥ 109.5^°) and n‐hexadecane (θ_hexadecane ≥ 68.9^°) pointed to the simultaneous hydrophobic and lipophobic characteristics of the copolymer surfaces. Dynamic contact angle measurements indirectly demonstrated that copolymer films underwent surface reconstruction upon contact with water, which results in a surface with surface coverage of polar PEG units. Moreover, the distinct nanoscale microphase segregation structures were proved by atomic force microscopy (AFM) images. Finally, using bovine serum albumin (BSA–FITC) as the model protein, copolymers exhibited excellent protein adsorption resistance. It is believed that the combination of surface reorganization and nanometer‐scale microphase segregation structure endows the excellent protein resistance for amphiphilic fluorinated copolymers. These results provide deeper insight of the effect of surface reconstruction and microphase segregation on the protein adsorption behaviors, and these amphiphilic fluoropolymers can expect to have potential applications as antifouling coatings in the field of marine and biomedical. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41167.     

Evaluating PE/PLA interfacial tension using ternary immiscible polymer blends

Blending with ethylene-based flexible polymers such as polyethylene (PE) is one of the strategies to toughen poly(lactic acid) (PLA), an inherently brittle biodegradable plastic enjoying growing demands worldwide. Interfacial tension plays a crucial role in blend formulation. Yet several literature reports on the PE/PLA interfacial tension contradict each other, giving ~5 mN/m and ~11 mN/m. In this work, we demonstrate that the PE/PLA interfacial tension is at least 9 mN/m. We use a cocontinuous PE/polystyrene (PS)/PLA ternary blend. Scanning electron microscopy (SEM) revealed complete wetting morphology with PS phase separating PE and PLA phases in the ternary blend. In addition, the complete wetting behavior was maintained at a PS volume fraction as low as 3%. This morphology together with the Harkins equation, indicate that the PE/PLA interfacial tension is higher than 10.5 ± 1.4 mN/m at 180°C.     

Synthesis of hyperbranched polybenzoxazoles and their molecular composites with epoxy resins

Hyperbranched aromatic polymers have attracted great attention recently because they combined the processability of hyperbranched polymers and the high‐level performance of aromatic polymers. Here, a one‐pot strategy for the synthesis of hyperbranched Polybenzoxazoles (HBPBOs) by polycondensation of 2,2‐Bis (3‐amino‐4‐hydroxyphenyl) hexafluoropropane and 1,3,5‐benzenetricarboxylic acid in Polyphosphoric acid was reported. The HBPBOs exhibited good solubility in organic solvents because of the branched structure and the flexible hexafluoropropane groups in main chains. The structure and terminal functional groups could be tailored by adjusting the molar ratio of two monomers. FT‐IR, NMR and XRD measurements confirmed the structure of HBPBOs, while thermogravimetric analysis (TGA), UV‐vis, and photoluminescence spectra, combined with the comparison with linear PBOs demonstrated the intriguing optical properties and good thermal stabilities of HBPBOs. The good solubility of HBPBOs also permitted their usage as molecular reinforcement for polymer composites as demonstrated in this study of HBPBOs/epoxy composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41942.     

Electrospun polymer of intrinsic microporosity fibers and their use in the adsorption of contaminants from a nonaqueous system

The smooth and uniform polymer of intrinsic microporosity (PIM‐1) fibers, which have high adsorption capacities toward organic contaminants from nonaqueous systems, were successfully obtained by electrospinning. According to the N₂ adsorption–desorption analysis, the surface area of the PIM‐1 fibers was higher than that of the PIM‐1 powder. The higher surface area of the fibers did not come from the interfiber pores but from intrafiber pores formed by the fast evaporation of the solvent in the electrospinning process. The PIM‐1 fibers had more mesopores than the PIM‐1 films. As a result, the adsorption rates of the dyes on the fibers were much higher than those on the dense films. We found that the adsorption data fitted perfectly with the pseudo‐second‐order model and intraparticle diffusion model. The adsorption mechanism between the dyes and PIM‐1 was π–π interaction. Therefore, the dye could be desorbed from PIM‐1 with toluene; this was a better π‐electron‐rich donor than the dye. In summary, we believe that the use of PIM‐1 fibers for organic solvent recovery is a green, sustainable, and efficient method, and they have a great potential for industrial applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43475.     

Highly hydrophobic hierarchical nanomicro roughness polymer surface created by stamping and laser micromachining

This article describes the design and fabrication of hierarchical nanomicrostructured polymer surfaces with high hydrophobicity. The nanoscale roughness is achieved by stamping a ZnO nanowire film into PDMS. Subsequently, microstructures with different periodicities are created in the stamped PDMS sample by direct laser writing using femtosecond pulses. With this approach, we were able to produce hierarchical surface morphologies, composed of nano and microscale structures that exhibit water contact angles larger than 160°. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42082.     

Thermomechanical and chemorheology properties of a thermosetting acrylic/melamine clearcoat modified with a hyperbranched polymer

The work presented here aims at studying the thermomechanical and chemorheological properties of an automotive clearcoat containing an acrylic/melamine resin modified with a hyperbranched poly ester‐amide (HBP) additive. Rheological experiments were conducted at ambient (25°C) and curing temperature (140°C). Dynamic mechanical thermal analysis and hardness measurements were performed to reveal the influence of HBP content on the behavior of the cured samples. It was found that the viscosity of the resin containing HBP samples considerably decreased. Although curing degree and mechanical properties were improved at low HBP loadings, a reverse effect was seen at higher contents. Dynamic rheological results during curing showed that although low amount of HBP resulted in an early gel point (GP), higher HBP loading postponed the GP. This loading‐dependent behavior was explained by the influence of HBP on viscosity and reactivity of the system on which the curing performance was influenced oppositely. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

QCM-D assay for quantifying the swelling,biodegradation, and protein adsorption of intelligent nanogels

Environmentally responsive nanomaterials have been developed for drug delivery applications, in an effort to target and accumulate therapeutic agents at sites of disease. Within a biological system, these nanomaterials will experience diverse conditions which encompass a variety of solute identities and concentrations. In this study, we developed a new quartz crystal microbalance with dissipation (QCM-D) assay, which enabled the quantitative analysis of nanogel swelling, protein adsorption, and biodegradation in a single experiment. As a proof of concept, we employed this assay to characterize non-degradable and biodegradable poly(acrylamide-co-methacrylic acid) nanogels. We compared the QCM-D results to those obtained by dynamic light scattering to highlight the advantages and limitations of each method. We detailed our protocol development and practical recommendations, and hope that this study will serve as a guide for others to design application-specific QCM-D assays within the nanomedicine domain. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48655.     

Peculiar electrical and photoelectric behaviors in conducting multilayers: Insights into accumulative charge tunneling

Layer‐by‐layer self‐assembly is a versatile technique for the construction of well‐defined nanoarchitectures with outstanding electrical and photoelectric performances. The revelation of a potential charge‐transfer mechanism of extraordinary electrical and photoelectric behaviors is profound in the design of modern electrical and photoelectrical devices. With the aim of revealing the potential charge‐transfer mechanism in conducting multilayer films, in this study, we fabricated [poly(styrene sulfonate)/polyaniline]_n [(PSS/PANi)_n] multilayers with peculiar electrical and photoelectrical features. The fantastic increments in sheet conductivity and photoelectric response were believed to be the percolation reflection of accumulative electrons tunneled across the insulating PSS from the bottom to the top of the conjugated structure of PANi. These profound phenomena, along with simple fabrication and a well‐defined architecture, promise that the conducting multilayers will be good candidates for electronic and optoelectronic nanodevices. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40258.     

Structural,topographical, and mechanical characteristics of purified polyhydroxyoctanoate polymer

Insight into the topographic and mechanical properties of biomaterials allows for efficient selection of a material for a specific application. Here, atomic force microscopy (AFM) and force spectroscopy were exploited to reveal the topographic and mechanical characteristics of charcoal-purified, solvent-cast polyhydroxyoctanoate (PHO) film. The root mean square surface roughness of a PHO surface derived from ethyl acetate, acetone, or chloroform solution was 13.2, 11.5, or 30.9 nm, respectively, for 100 μm² AFM images. The distribution of the local Young's modulus had a maximum of 25.4, 14.1, and 12.6 MPa for PHO films obtained from ethyl acetate, acetone, and chloroform solution, respectively. The positron annihilation spectroscopy measurements allowed us to determine the free volume in the polymer film structure (9.38%). Moreover, a number of additional techniques (X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, gel permeation chromatography, NMR, infrared spectroscopy, and polarized light microscopy) were used to reveal PHO features. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47192.