Surface Functionalization Of Poly Research Articles

Surface Functionalization of Poly(lactic acid) via Deposition of Hydroxyapatite Monolayers for Biomedical Applications.

The surface modification of poly(lactic acid) (PLA) using hydroxyapatite (HAP) particles via Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) approaches has been reported. The HAP monolayer was characterized at the air/water interface and deposited on three-dimensional (3D) printed poly(lactic acid). The deposition of HAP particles using the LS approach led to a larger surface coverage in comparison to the LB method, which produces a less uniform coating because of the aggregation of the particles. After the transfer of HAP on the PLA surface, the wettability values remained within the desired range. The presence of HAP on the surface of the polymer altered the topography and roughness in the nanoscale, as evidenced by the atomic force microscopy (AFM) images. This effect can be beneficial for the osteointegration of polymeric implants at an early stage, as well as for the reduction of the adherence of the microbial biofilm. Overall, the results suggest that the LS technique could be a promising approach for surface modification of PLA by hydroxyapatite with respective advantages in the biomedical field.

Surface functionalization of poly(ether ether ketone) by wet-chemical modification with carboxylic acids and diamine

Polyaryletherketones (PAEK) are high-performance plastics with excellent mechanical properties and high thermal resistance used, e.g. as material for implants. Their molecular structure gives them a high level of chemical inertness but prevents bonding and adhesive interactions with other materials and integration into body tissue. Using the example of poly(ether ether ketone) (PEEK), we show novel synthetic routes for wet-chemical modification of the surface to create reactive carboxylic and amino groups. In a first approach, the ketone functionalities of the PEEK molecules were reduced to hydroxy groups and subsequently esterified with carboxylic acids. Using dicarboxylic acids, one acid group was bonded covalently to the PEEK surface while the other provided free acidic functionalities. In a second approach, the PEEK surface was modified in one step by reaction of the ketone group with a diamine, creating primary amino groups on the PEEK surface. All reaction products were analyzed by a powerful combination of surface sensitive X-ray photoelectron spectroscopy (XPS) and advanced infrared spectroscopic methods.

Surface functionalization of poly(dimethylsiloxane) substrates facilitates culture of pre-implantation mouse embryos by blocking non-selective adsorption.

Poly(dimethylsiloxane) (PDMS) is widely used in biomedical settings such as microfluidics for its optical transparency, castability, gas permeability and relative biocompatibility. While PDMS devices with certain modifications or treatments have been used for mammalian pre-implantation embryo culture, it is unclear why native PDMS leads to significant embryo death. In this study, we employ Nile Red as a model hydrophobic small molecule to demonstrate that significant hydrophobic sequestration occurs on native PDMS substrates even with a bovine serum albumin-containing KSOM pre-equilibration. Our results suggest that this small molecule sequestration has detrimental effects on mouse embryo development in PDMS static culture wells, with 0% blastocyst development rates from embryos cultured on native PDMS. We found that prior saturation of the PDMS culture well with water vapour only rescues about 10% of blastocyst development rates, indicating osmolality alone is not responsible for the high rates of embryo arrest. We also present a safe and simple Pluronic F127 pretreatment for PDMS substrates that successfully circumvented the harmful effects of native PDMS, achieving a blastocyst and implantation rate akin to that of our polystyrene controls. Our results call into question how researchers and clinicians can account for the alterations in medium composition and embryo secretions when using hydrophobic substrates, especially in the mammalian embryo culture setting where minimum effective concentrations of peptides and amino acids are commonplace.

Surface Functionalization of Poly(l-lactide-co-glycolide) Membranes with RGD-Grafted Poly(2-oxazoline) for Periodontal Tissue Engineering.

Bone tissue defects resulting from periodontal disease are often treated using guided tissue regeneration (GTR). The barrier membranes utilized here should prevent soft tissue infiltration into the bony defect and simultaneously support bone regeneration. In this study, we designed a degradable poly(l-lactide-co-glycolide) (PLGA) membrane that was surface-modified with cell adhesive arginine-glycine-aspartic acid (RGD) motifs. For a novel method of membrane manufacture, the RGD motifs were coupled with the non-ionic amphiphilic polymer poly(2-oxazoline) (POx). The RGD-containing membranes were then prepared by solvent casting of PLGA, POx coupled with RGD (POx_RGD), and poly(ethylene glycol) (PEG) solution in methylene chloride (DCM), followed by DCM evaporation and PEG leaching. Successful coupling of RGD to POx was confirmed spectroscopically by Raman, Fourier transform infrared in attenuated reflection mode (FTIR-ATR), and X-ray photoelectron (XPS) spectroscopy, while successful immobilization of POx_RGD on the membrane surface was confirmed by XPS and FTIR-ATR. The resulting membranes had an asymmetric microstructure, as shown by scanning electron microscopy (SEM), where the glass-cured surface was more porous and had a higher surface area then the air-cured surface. The higher porosity should support bone tissue regeneration, while the air-cured side is more suited to preventing soft tissue infiltration. The behavior of osteoblast-like cells on PLGA membranes modified with POx_RGD was compared to cell behavior on PLGA foil, non-modified PLGA membranes, or PLGA membranes modified only with POx. For this, MG-63 cells were cultured for 4, 24, and 96 h on the membranes and analyzed by metabolic activity tests, live/dead staining, and fluorescent staining of actin fibers. The results showed bone cell adhesion, proliferation, and viability to be the highest on membranes modified with POx_RGD, making them possible candidates for GTR applications in periodontology and in bone tissue engineering.

Surface functionalization of poly(vinylidene fluoride) membrane by radiation‐induced emulsion polymerization of hydroxyethyl acrylates in an aqueous medium

AbstractDecades ago, surface modification of poly(vinylidene fluoride) (PVDF) membrane became an essential subject. The change is mainly to enhance the hydrophilicity properties of the membrane in order to increase the adsorption capacity, thus making as a novel adsorbent. This study aims to used radiation‐induced polymerization and compares the final properties of PVDF grafted hydroxyethyl acrylates (HEA) prepare by two different approaches. The PVDF‐grafted‐HEA has achieved either direct polymerization or emulsion polymerization. Tween‐20 has been used as a surfactant in emulsion polymerization. The final PVDF‐grafted poly‐HEA was analyzed using several different instruments to observe the changes in terms of morphological structure, topography properties, thermal stability, mechanical strength, and hydrophilicity. Significant differences were seen in morphology and contact angles properties. By emulsion polymerization, poly‐HEA grafted in the shape of micelles compare to by direct polymerization shown a thin homogenous layer. Thus, the surface roughness of PVDF by emulsion is higher lead to higher contact angles. Even though both approaches demonstrate significant changes in the physicochemical properties of the PVDF membrane, it is revealed that radiation‐induced direct polymerization approaches could achieve a hydrophilic PVDF‐grafted HEA.

Development of Poly(2-Methacryloyloxyethyl Phosphorylcholine)-Functionalized Hydrogels for Reducing Protein and Bacterial Adsorption.

A series of hydrogels with intrinsic antifouling properties was prepared via surface-functionalization of poly(2-hydroxyethyl methacrylate) [p(HEMA)]-based hydrogels with the biomembrane-mimicking zwitterionic polymer, poly(2-methacryloyloxyethyl phosphorylcholine) [p(MPC)]. The p(MPC)-modified hydrogels have enhanced surface wettability, high water content retention (61.0%–68.3%), and good transmittance (>90%). Notably, the presence of zwitterionic MPC moieties at the hydrogel surfaces lowered the adsorption of proteins such as lysozyme and bovine serum albumin (BSA) by 73%–74% and 59%–66%, respectively, and reduced bacterial adsorption by approximately 10%–73% relative to the unmodified control. The anti-biofouling properties of the p(MPC)-functionalized hydrogels are largely attributed to the dense hydration layer formed at the hydrogel surfaces by the zwitterionic moieties. Overall, the results demonstrate that biocompatible and antifouling hydrogels based on p(HEMA)-p(MPC) structures have promising potential for application in biomedical materials.

Surface functionalization of poly(ε-caprolactone) and poly(3-hydroxybutyrate) with VEGF

AbstractIn this study, surface modifications for the biodegradable polymers poly(ε-caprolactone) (PCL) and poly(3-hydroxybutyrate) [P(3HB)] were developed in order to improve their suitability as scaffold material for bioartificial vessel prostheses. The challenge of wet-chemical surface modifications is to avoid bulk adjustments resulting in undesired changes in mechanical properties of these polymers. Nevertheless subsequent immobilization and controlled release of potent angiogenic biomolecules like vascular endothelial growth factor (VEGF) from the polymer surface is required. In order to improve the biocompatibility of PCL and P(3HB), terminal hydroxyl groups on the surface of these polymers were generated via oxygen (O

Antimicrobial nature and healing behavior of plasma functionalized polyester sutures

This study deals with the development of bioactive poly(ethylene terephthalate) surgical suture by adopting the immobilization route with bioactive nanogels and chlorhexidine. Carbon dioxide plasma was used for the generation of carboxyl functionality on poly(ethylene terephthalate) surface for the immobilization of the bioactive components. The nanosilver nanogel was prepared using polyethylene glycol which helps in the reduction of silver ions into nanosilver as well as the stabilization of nanoparticles. The particle size of the nanogels, as evaluated by high-resolution transmission electron microscopy, was observed to be in the range of 10–50 nm. Surface functionalization of poly(ethylene terephthalate) filament was observed by attenuated total reflectance measurements and mechanical studies were investigated by Instron. Elemental analysis and surface topography were carried out by energy dispersive X-ray and atomic force microscopy. The cumulative release of silver from the dressing was found to be 68% of the total loading after 72 h. Coated sutures have excellent antimicrobial activity against both Escherichia coli and Staphylococcus aureus. In vivo wound healing and histopathology studies were carried out over a period of 72 h for skin wounds created on Swiss albino mice. Fast healing was observed in nanogel-treated wounds without any inflammatory effects on the newly generated skin. These sutures offer improved healing along with excellent antimicrobial properties and appear to be promising material against surgical infection.

Enzyme-Functionalized PLGA Nanoparticles with Enhanced Mucus Permeation Rate

The surface functionalization of poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) with various proteolytic enzymes (i.e., trypsin, papain, bromelain) via a two-step carbodiimide coupling method is presented. Depending on the initial Enzyme:NPs ratio, enzyme loadings up to 4.0 wt.%, 4.4 wt.% and 5.34 wt.% were achieved for trypsin, papain and bromelain, respectively. All three conjugated enzymes partially maintained their enzymatic activity after their coupling reaction with the NPs. NPs functionalized with papain and bromelain exhibited a three-fold higher permeability in porcine intestinal mucus compared to nonfunctionalized NPs whereas those conjugated with trypsin showed an almost two-fold higher permeability value. Measurements of the diffusion rates of intestinal mucin, using a nuclear magnetic resonance (NMR) technique, further confirmed these observations, as the enzyme-functionalized NPs were proven to be capable of disrupting the mucin gel structure. According to the reported results, the coupling of proteolytic enzymes to the PLGA NPs' surface largely increases the NPs mucus permeability, thus making it a potentially important mucus permeation strategy.

Surface Functionalization of Poly(ether imide) Membranes with Linear, Methylated Oligoglycerols for Reducing Thrombogenicity

Materials for biomedical applications are often chosen for their bulk properties. Other requirements such as a hemocompatible surface shall be fulfilled by suitable chemical functionalization. Here we show, that linear, side-chain methylated oligoglycerols (OGMe) are more stable to oxidation than oligo(ethylene glycol) (OEG). Poly(ether imide) (PEI) membranes functionalized with OGMes perform at least as good as, and partially better than, OEG functionalized PEI membranes in view of protein resistance as well as thrombocyte adhesion and activation. Therefore, OGMes are highly potent surface functionalizing molecules for improving the hemocompatibility of polymers.

Surface functionalization of poly(ε‐caprolactone) improves its biocompatibility as scaffold material for bioartificial vessel prostheses

Within this study, chemically modified polymer surfaces were to be developed, which should enhance the subsequent immobilization of various bioactive substances. To improve the hemocompatibility and endothelialization of poly(ε-caprolactone) (PCL) intended as scaffold material for bioartificial vessel prostheses, terminal amino groups via ammonia (NH₃) plasma, oxygen (O₂) plasma/aminopropyltriethoxysilane (APTES), and 4,4'-methylenebis(phenyl isocyanate) (MDI)/water were provided. Then, immobilization of the anti-inflammatory and antithrombogenic model drug acetylsalicylic acid (ASA) and vascular endothelial growth factor (VEGF) were performed by employing N,N-disuccinimidyl carbonate (DSC) as crosslinker. Contact angle and fluorescence measurements, X-ray photoelectron spectroscopy and infrared spectroscopy confirmed the surface modification. Here the highest functionalization was observed for the O₂ plasma/APTES modification. Furthermore, biocompatibility studies demonstrated that the surface reactions have no negative influence, neither on the viability of L929 mouse fibroblasts, nor on primary or secondary hemostasis. Release studies showed that the immobilization of ASA and VEGF on the modified PCL surface via DSC is greatly improved compared to the adsorption-only reference. The advantage of DSC is that it immobilizes both bioactive substances via non-hydrolyzable and/or hydrolyzable covalent bonding. The highest ASA loading and cumulative release was detected using NH₃ plasma-activated PCL samples. For VEGF, the O₂ plasma/APTES-modified PCL samples were most efficient with regard to loading and cumulative release. In conclusion, both modifications are promising methods to optimize PCL as scaffold material for bioartificial vessel prostheses.

Stimuli–responsive track-etched membranes via surface-initiated controlled radical polymerization: Influence of grafting density and pore size

The surface-functionalization of poly(ethylene terephthalate) track-etched membranes of different nominal pore sizes (400, 1000 and 3000 nm) with stimuli–responsive poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) via surface-initiated (SI) atom transfer radical polymerization (ATRP) was performed. Variations of grafting density and grafted chain length were achieved by variation of synthesis conditions. It could be clearly demonstrated that mixtures of reaction solutions containing different ratios of acyl bromides, only one bearing the initiator group necessary for the SI ATRP, led to different initiator group densities on the resulting track-etched membrane surface which had been verified by X-ray photoelectron spectroscopy. Moreover the mass increase as function of reaction time strongly correlated with the amount of initiator bound to the membrane surface indicating that the ATRP reaction was not limited by monomer diffusion into the pores. Scanning electron microscopy images and permporometry measurements indicated an even functionalization on the entire membrane surface which was the basis for further investigations. The stimuli–responsive properties of PDMAEMA grafted track-etched membranes were studied by permeability measurements with citrate and glycine buffers as function of pH (2 and 10) and temperature (25 and 60 °C). By that the barrier properties of the membranes could be effectively changed in two steps. The results agree with the expectation that a change in grafting density and chain length has an effect on the stimuli–responsive properties of the membrane. Results for membranes having similar degrees of grafting clearly showed that the reversible swelling of grafted polymeric layers was more pronounced for lower grafting density.

Surface Functionalization of a Poly(vinylidene fluoride): Effect on the Adhesive and Piezoelectric Properties

We studied the effect of the surface functionalization and crystalline phase change of poly(vinylidene fluoride) (PVDF) films on their adhesion and piezoelectric properties. The surface modification of PVDF was carried out with ion beam and/or plasma treatment. These surface modifications were found to alter the interfacial strength between PVDF and metal electrodes and the crystal structure of the piezoelectric PVDF film. A remarkable improvement was found in the interfacial adhesion of the films with thermally deposited metal electrodes, but some piezoelectricity of PVDF film was lost due to the changes in the crystal phase. The proper treatment condition for enhancing the adhesion and retaining piezoelectric structure was suggested.

Surface Functionalization of Poly(Ethylene Terephthalate) for Biomolecule Immobilization by Ion Implantation

Surface Functionalization of Poly(Ethylene Terephthalate) for Biomolecule Immobilization by Ion Implantation

Surface functionalization of poly(lactic acid) film by UV‐photografting of N‐vinylpyrrolidone

AbstractThe photoinitiated grafting of N‐vinylpyrrolidone (NVP) onto poly(lactic acid) (PLA) film with the use of benzophenone (BP) as the initiator, modified the natural hydrophobic PLA behavior to an hydrophilic film with desirable wettability. The surface photografting parameters‐percent conversion of monomer to overall photopolymerization (Cp), percent conversion of monomer to the photograft polymerization (Cg), and grafting efficiency (Eg) were calculated. The resulting film surface was analyzed using ATR‐FTIR and UV spectroscopy, derivative spectroscopy and water contact angle. Besides, we demonstrated that the grafted polyvinylpyrrolidone chains could easily react with iodine to form a complex as the homopolymer does with antibacterial activity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Surface functionalization of poly(d,l-lactic acid) nanoparticles with poly(ethylenimine) and plasmid DNA by the layer-by-layer approach

Abstract Poly( d , l -lactic acid) (PLA) particles, obtained by the emulsification–diffusion process, were surface modified by electrostatic interactions with cationic poly(ethylenimine) (PEI). The charge inversion was evidenced by zeta potential measurements and the adsorption isotherms of PEI were established. No flocculation was observed by Quasi-Elastic Light Scattering (QELS) or Scanning Electron Microscopy (SEM) so long as the PEI amount in the adsorption medium was close to the surface saturation. With water as an adsorption medium, low PEI loading levels were achieved but, when salt was added, higher amounts of polymer were immobilized at the surface of the PLA particles, as proved by the positive value of the zeta potentials (+20–30 mV). Highly cationized latex particles complexed plasmid DNA under a compacted conformation, as evidenced by the ethidium bromide displacement results, similar to the PEI free in solution. With particles obtained by PEI adsorption from water, low amounts of DNA were loaded on the surface and the level of compaction was low.

Surface Functionalization of Poly(tetrafluoroethylene) Films via Consecutive Graft Copolymerization with Glycidyl Methacrylate and Aniline

Chemical modification of argon-plasma-pretreated poly(tetrafluoroethylene) (PTFE) film by UV-induced surface graft copolymerization with glycidyl methacrylate (GMA), followed by epoxide-ring-opening reaction with aniline (An), and finally oxidative graft polymerization with aniline had been carried out to render the PTFE surface conductive. The surface composition and microstructure of the graft-copolymerized PTFE films were studied by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The graft concentration of the GMA polymer and An polymer increased with increasing concentration of the respective monomer used for graft polymerization. Ethanol, when used as a solvent, catalyzed the coupling reaction of epoxide with An and should be of more than 40 vol % in concentration to achieve the optimum effect. The physicochemical characteristics of the polyaniline (PANI) chains grafted onto PTFE film surface were grossly similar to those of the PANI homopolymer. The surface resistance of the aniline graft-polymerized PTFE film was reduced to the order of about 104 Ω/square, in comparison to the value of 1016 Ω/square for the pristine PTFE film.

Solventless Attachment of Long-Chain Molecules to Poly(ethylene-alt-maleic anhydride) Copolymer Surfaces

Surface functionalization of poly(ethylene-alt-maleic anhydride) copolymer films with trifluoroethylamine and amine terminated polyethers (Jeffamines) to form amide linkages has been shown to proceed to high levels of conversion.

Surface Functionalization of Poly(ethylene) with Succinic Anhydride: Preparation, Modification, and Characterization

Succinic anhydride groups have been introduced on the surface of and in bulk poly(ethylene) film by a mild photochemical process. These groups on the poly(ethylene) film undergo facile transformation to various functional groups such as acids, esters, or amides by reaction with water, amine compounds, or PEG, etc. The surface functionality has been quantitatively estimated by using gravimetry, ATR-FTIR, XPS, and UV−visible spectroscopy. Surface hydrophilicity was characterized by contact angle goniometry. The poly(ethylene) bound to the azobenzene group, exhibiting interesting responses to external stimuli such as photoinduced and thermally induced E:Z isomerization.

Surface Functionalization of Poly(ethylene terephthalate) Film and Membrane by Controlled Wet Chemistry: Chemical Characterization of Carboxylated Surfaces

Surface functionalization of poly(ethylene terephthalate) (PET) film or track-etched membrane was performed using the methods of organic synthesis conducted at the solid-liquid interface. Basic hydrolysis in aqueous acetonitrile followed by permanganate oxidation in diluted sulfuric acid created new carboxylic chain-ends. These reactive functions were assayed as follows: (i) activation with water soluble carbodiimide; (ii) coupling to 3 H-labeled amino acids; and (iii) liquid scintillation counting of the sample-associated radioactivity. Some samples were also analyzed by X-ray photoelectron spectroscopy. Depending on the experimental conditions (temperature and duration of treatment), about 1-2% of the surface repeated units could be functionalized without deterioration of the polymer bulk. This study establishes the best conditions for the covalent anchorage of bioactive substances on the PET surface.