Allylamine Films Research Articles

Plasma polymerized allylamine films deposited on 316L stainless steel for cardiovascular stent coatings

Coronary stents are metallic (316L stainless steel) medical devices used during balloon angioplasty to scaffold diseased arteries and prevent their reblockage. To reduce the restenosis rate, bare metal stent coating is a promising solution. The coating can protect the metallic surface of the stent from corrosion attack caused by the biological environment. In addition, according to Food and Drug Administration (FDA) the coating properties must be guaranteed even after stent expansion. The aim of this study was to develop a dry process to coat the metallic surface from the biological environment by depositing an ultra-thin, stable, cohesive and adhesive plasma polymerized allylamine (CH2=CH―CH2―NH2) coating with high selectivity towards primary amine groups. Plasma polymerized allylamine (PPAA) coatings were deposited on electropolished 316L stainless steel (316L SS) samples using a low pressure plasma reactor (70kHz). XPS (X-Ray Photoemission Spectroscopy) and FTIR-ATR (Fourier Transform Infrared-Attenuated Total Reflectance) spectroscopy measurements were used to investigate the chemical composition of the coatings. A chemical derivatization technique was employed in order to quantify the amine retention rate of the deposited films. Morphology of the films was evaluated by FE-SEM (Field Effect-Scanning Electron Microscopy) imaging. Furthermore, special attention was devoted to study the stability of the coating and its adhesion properties after plastic deformation up to 25%. The effect of the power discharge and treatment time on these properties was also investigated. Our results showed that coatings present the required adhesion and cohesion properties to be stable upon deionised (D.I.) water immersion and to resist to a stent expansion.

Influence of the Solution on Adhesion Layer Polymerized in Radio Frequency Pulsed Plasma for DNA Hybridization Assay

A radio frequency (RF) pulsed plasma polymerized allylamine (PPPAA) film as an adhesion layer to adsorb DNA probe and then hybridize with a complementary or a mismatch DNA target is investigated in this paper. The possible application of plasma polymerization film as an adhesion layer for DNA hybridization assay is evaluated by DNA hybridization reactions. It was found, by surface plasmon enhanced fluorescence spectroscopy (SPFS), that the DNA hybridization reactions in phosphate buffered saline (PBS) solution can be remarkably revealed by fluorescence signals, but it heavily depends on the solution conditions. The influence of the solution pH value and the ionic strength on the PPPAA film thickness and adsorption is explored in detail.

Structural characterization and mechanical properties of functionalized pulsed-plasma polymerized allylamine film

Due to its surface properties, especially the presence of abundant amine groups, pulsed-plasma polymerized allylamine (PPAa) is used to manufacture biosensor and modify surface of metallic biomaterials. In the present study, PPAa films on 316L medical stainless steel are prepared by pulsed radio frequency (RF) plasma polymerization using allylamine as a precursor under different duty cycles. The effect of the pulsed duty cycles on the composition, structure, surface morphology, wettability and mechanical properties of PPAa films are investigated by Fourier transform infrared (FTIR) spectroscopy, laser Raman spectra, X-ray photoelectron spectroscope (XPS), atom force microscope (AFM), contact angle measurement, nanoscratch test and substrate straining method. All results of FTIR, XPS and Raman indicate that there are more amine groups from allylamine monomer on the 20/80 film fabricated by 20% duty cycle. The wettability of the 20/80 film is higher than that of 20/30 film prepared using 40% duty cycle. AFM micrographs demonstrate no remarkable differences in the morphological characteristics, but grain size of 20/30 film is larger than that of 20/80 film. The critical force of 20/80 film is about 71.86 mN, higher than that of 20/30 film and has a better scratch resistance. It is estimated that the mechanical properties of the plasma polymerization are different.

Plasma Surface Modification of 316L Stainless Steel for Cardiovascular Stent Coating

Coronary stents are metallic (316L stainless steel) devices employed during balloon angioplasty to reopen and prevent the re-obstruction of a diseased narrowed area within a coronary artery. To reduce restenosis rate, bare metal stent coating is a promising solution. The coating can act as an anticorrosive barrier against the aggressive properties of biological environment, improving the long-term safety of the device. The goal of this study is to develop a dry process to isolate metallic surface from the biological environment by depositing a thin plasma polymerized allylamine (CH2=CH-CH2-NH2) film on the metallic surface. Plasma polymerized allylamine films were deposited on flat electropolished 316L stainless steel samples in a low pressure plasma reactor (70 kHz). Chemical composition of the coatings has been analysed as a function of the discharge power and treatment time. Moreover, special attention has been paid on the stability of the coating after immersion during 24 hours in D.I. water. Finally, to mimic stent expansion conditions, a “small punch test” has been used to investigate the adhesive properties of the coating. Our results demonstrate that is possible to deposit a stable, cohesive and adhesive plasma polymerized allylamine thin film which can be used as a coating for cardiovascular stents

Synthesis and Characterization of Organic Thin Film Using Atmospheric-Pressure Plasma Polymerization

We developed a novel method of fabricating polymer film on a substrate at atmospheric pressure using atmospheric-pressure plasma polymerization (APPP) with a laboratory-made torch-type APPP apparatus. We used allylamine and acrylic acid as model monomers to optimize the polymerization conditions and evaluate the fabricated films. The APPP films were characterized by Fourier transform infrared (FT-IR) spectroscopy, contact angle measurement, atomic force microscopy (AFM), ellipsometry, X-ray photoelectron spectroscopy (XPS), deposition rate determination, and persistence measurement. Results showed that the properties of the APPP allylamine and acrylic acid films can be controlled by adjusting the polymerization parameter of ultrahighfrequency power.

The covalent immobilization of heparin to pulsed-plasma polymeric allylamine films on 316L stainless steel and the resulting effects on hemocompatibility

For an improved hemocompatibility of 316L stainless steel (SS), we develop a facile and effective approach to fabricating a pulsed-plasma polymeric allylamine (P-PPAm) film that possesses a high cross-linking degree and a high density of amine groups, which is used for subsequent bonding of heparin. The P-PPAm film as a stent coating shows good resistance to the deformation behavior of compression and expansion of a stent. Using deionized water as an aging medium, it is demonstrated that the heparin-immobilized P-PPAm (Hep-P-PPAm) surface has a good retention of heparin. The systematic in vitro hemocompatibility evaluation reveals lower platelet adhesion, platelet activation and fibrinogen activation on the Hep-P-PPAm surface, and the activated partial thromboplastin time prolongs for about 15 s compared with 316L SS. The P-PPAm surface significantly promotes adhesion and proliferation of endothelial cells (ECs). For the Hep-P-PPAm, although EC adhesion and proliferation is slightly suppressed initially, after cultivation for 3 days, the growth behavior of ECs is remarkably improved over 316L SS. In vivo results indicate that the Hep-P-PPAm surface successfully restrain thrombus formation by growing a homogeneous and intact shuttle-like endothelium on its surface. The Hep-P-PPAm modified 316L SS shows a promising application for vascular devices.

Preparation and Multi‐Characterization of Plasma Polymerized Allylamine Films

AbstractPlasma polymerized allylamine (ppAA) films were deposited in a radio‐frequency glow discharge plasma reactor using a continuous‐wave mode and varying the discharge power from 15 to 125 W. The deposition rate reached 26 nm · min−1 and was constant within at least half an hour of process. The chemical structure and elemental composition of the deposited films were investigated by Fourier transform infrared and X‐ray photoelectron spectroscopies, whereas surface properties were analyzed by atomic force microscopy and surface free energy measurement. A special focus is given to the stability of ppAA in aqueous media and primary amine quantification. The use of fluorescent microscopy and UV‐Visible spectroscopy enabled us to detect and quantify the primary amine, respectively. All the studied parameters varied widely with enhanced power with a transition point around 50 W. Over this value, the results remain relatively unchanged.magnified image

Pulsed‐Plasma Polymeric Allylamine Thin Films

AbstractHigh surface functional groups concentration, excellent dynamical stability and mechanical properties are ideal for biomedical plasma polymers. Herein, we report a simple and effective approach to fabricating such an ideal plasma polymeric allylamine film on 316L stainless steel (SS) by pulsed plasma polymerization. The experimental results show that the concentration of the primary amine groups (NH2/C) of the plasma polymeric allylamine film was 2.4 ± 0.4%. The plasma polymeric allylamine film possesses not only high surface NH2 concentration, but also high cross‐linking degree and close‐knit network structure that could well resist hydrolysis, and dissolution in the aqueous solution. Furthermore, the plasma polymeric allylamine film was used as a stent coating that shows a good resistance to the deformation behaviour of compression and expansion of the stent.magnified image

Covalent attachment of trypsin on plasma polymerized allylamine

This paper focuses on the immobilization of a proteolytic enzyme, trypsin, on plasma polymerized allylamine (ppAA) films. The later have been deposited onto silicon substrate by means of radiofrequency glow discharge. The covalent attachment of the enzyme was achieved in three steps: ( i) activation of the polymer surface with glutaraldehyde (GA) as a linker, ( ii) immobilization of trypsin and ( iii) imino groups reduction treatment. The effects and efficiency of each step were investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Fluorescent spectroscopy was used to evaluate the change of the biological activity following the immobilization steps. The results showed that enzyme immobilization on GA-modified substrate increases the enzyme activity by 50% comparing to adsorbed enzymes, while the imino reduction treatment improves the enzyme retention by about 30% comparing to untreated samples. In agreement with XPS and AFM data, UV–vis absorption spectroscopy, used to quantify the amount of immobilized enzyme, showed that allylamine plasma polymer presents a high adsorption yield of trypsin. Although the adsorbed enzymes exhibit a lower activity than that measured for enzymes grafted through GA linkers, the highest catalytic activity obtained was for the enzymes that underwent the three steps of the immobilization process.

Production and preliminary characterization of DC plasma polymerized allylamine film (PPAA) by NRA, ERD and XPS

Due to its surface properties, especially the presence of amine groups, plasma polymerized allylamine (PPAA) is involved in a large range of applications. Most of them are related to biology and biochemistry. In this work, we demonstrate a quick and simple way to produce PPAA thin films by conventional DC magnetron sputtering. To the best of our knowledge, this is the first method not involving radiofrequency (RF) or microwave discharges. In this paper, we show preliminary characterizations on the produced films (bulk analysis) carried out by ion beam techniques. The Hydrogen content in the whole layers was measured by ERD. The surface composition was probed by XPS on pentafluorobenzaldehyde (PFBA) derivatized films: the maximum concentration of amine groups is 1.6%.

Characteristics of polyimide-based composite membranes fabricated by low-temperature plasma polymerization

Composite membranes were prepared by the deposition of plasma-polymerized allylamine films onto a porous polyimide substrate. The relationship between the plasma conditions and the membrane characteristics was described in terms of monomer flow rate, plasma discharge power, plasma polymerization time, and so on. Scanning electron microscope (SEM) images indicate that the thickness of the plasma polymer layer increased and the membrane skin pore size decreased gradually with the increasing of plasma polymerization time. Fourier transform infrared (FTIR) spectra demonstrate the appearance of amine groups in the plasma deposited polymer and the contact angle measurements indicate that the hydrophilicity of the membrane surfaces increased significantly after plasma polymerization. The composite membranes can reject salt from sodium chloride feed solution, and membrane separation performance depends strongly on the plasma conditions applied during the preparation of the plasma deposited polymer films.

Surface Characterization of Biopolymer Micropatterns Processed by Ion‐Beam Modification and PECVD

AbstractThe surface properties of poly(ethylene glycol) (PEG) and allylamine (ALL) have been used to create biomedical micropatterns by exploiting the antifouling character of ion beam‐treated PEG and the biofunctional properties of ALL films deposited using plasma‐enhanced (PE) CVD. For integration, the PEG film can be etched through a mask to subsequently deposit ALL in the formed cavities. Imaging mode X‐ray photoelectron spectroscopy (XPS) corroborates the contrasting chemistry, while time of flight secondary ion mass spectroscopy (ToF‐SIMS) demonstrates a net heparin adsorption inhibition onto PEG. The performance of the micropatterned platforms is supported by the selective response of L929 mouse fibroblasts.

Stabilization of Plasma-Polymerized Allylamine Films by Ethanol Extraction

The effect of ethanol extraction on plasma-polymerized allylamine (PPAA) films was investigated by measuring their thickness change using surface plasmon resonance (SPR) spectroscopy and optical waveguide spectroscopy (OWS). It was found that much of the freshly deposited PPAA films is lost upon ethanol treatment. The decrease in PPAA thickness is related to the plasma input power, the monomer vapor pressure, and the thickness of the deposited films. Despite the relatively high loss in film thickness, the densities of the amine groups in the extracted PPAA are comparable to those of fresh films, as seen by Fourier transform infrared (FT-IR) spectroscopy. The results of this study are of specific importance with respect to the biomedical application of plasma-polymerized functional thin films, in which the stability of a plasma polymer in contact with aqueous media is essential.

Chemical structure and surface morphology of plasma polymerized-allylamine film

In this study, we conducted the plasma polymerization of allylamine using radio frequency (RF) glow discharge with continuous wave (CW) in order to make an organic thin film with an amine functional group retained. Allylamine as a monomer was deposited on a glass in a bell-jar type plasma reactor and polymerized to plasma-polymerized allylamine (PPAa). The parameter to control the property of plasma polymer was input power at other conditions remaining constant. The chemical structure and the surface morphology of plasma-polymerized allylamine (PPAa) film were characterized by contact angle measurement, Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM). The property of PPAa film was highly dependent upon the plasma input power. The input power, which determines the plasma density, results in a property of PPAa thin film such as hydrophilicity, high retention of functionality of PPAa’s surface. Surface energy calculated by contact angle measurement indicated that increasing input power (from 30W to 90W) decreased the hydrophilic property of PPAa due to loss of amine functional group and high cross-linking. The increase of the energy causes the films to be harder. ATR-FTIR and XPS results showed that high input energy fragmented the amine group from monomer with increasing nitrogen atomic content and nitrile group. The high retention of amine groups seems mainly favored by low input power (<30 W). From thickness measurement usingα-stepper, the deposition rates were 0.43, 0.83, 1.11, 1.37 nm/s at 30, 50, 70, 90W, respectively. The change of surface morphology of plasma-polymerized thin films was investigated after soaking the PPAa film into ethanol. Due to weak adhesion with substrate and internal stress in plasma polymer film, the surface morphology of PPAa film revealed some irregular network pattern.

Surface stress control using ultraviolet light irradiation of plasma-polymerized thin films

We investigated the surface stress change of plasma-polymerized allylamine films on 2μm thick silicon micromechanical cantilever substrates induced by ultraviolet light (UV) irradiation. Compressive surface stress was generated during the UV irradiation of the plasma-polymerized films in a dry environment, whereas tensile stress was measured in a humid environment. Fourier transform infrared spectroscopic analysis indicated two mechanisms taking place depending on the environmental conditions. These were attributed to crosslinking and oxidation reactions of the plasma polymer. UV irradiation of plasma polymerized allylamine films at defined humidity suggests a feasible method for achieving tensile and compressive surface stress patterning.

Surface Analysis of Plasma Deposited Polymer Films, 7

AbstractSummary: Plasma deposited allylamine films were studied by “in situ” ToF‐SSIMS, XPS and NEXAFS Spectroscopy before exposure to ambient air. The influence of external plasma parameters such as duty cycle, plasma power, and monomer flow rate on (i) unsaturation, (ii) branching and cross‐linking, (iii) nitrogen surface concentration and (iv) retention of amino groups was investigated. Harder plasma conditions, which can be obtained when high duty cycles, high plasma power, and low monomer flow rates are employed, increase the unsaturated, branched and cross‐linked character of the plasma deposited films, while the surface concentration of N as well as the retention of the monomer's amino group decrease. As proven by NEXAFS findings and cross‐checked by ToF‐SSIMS results, the allylamine monomer's primary amino groups are partially transformed into other nitrogen functionalities during its plasma polymerization. Amongst them imines and nitriles are the conversion products with the highest probabilities of formation. Another conversion channel is the formation of nitrogen species not participating in the film growth. This is the reason for an increased N loss in plasma deposited allylamine films as observed independently by XPS and ToF‐SSIMS when the plasma parameters are changed from mild to hard.Summations of π*(CN) and π*(CN) resonance intensities for NEXAFS N K‐edge spectra measured with plasma deposited allylamine films vs. variation of duty cycle, or power.magnified imageSummations of π*(CN) and π*(CN) resonance intensities for NEXAFS N K‐edge spectra measured with plasma deposited allylamine films vs. variation of duty cycle, or power.

STW gas sensors using plasma-polymerized allylamine

Gas sensors generally consist of two major components: a gas recognition element which provides the specificity and selectivity of the measurement and a physical transducer which translates the gas absorption or desorption event into electronic signal. In this paper, plasma polymerized allylamine (PPAa) film is used as a gas recognition element and a surface transverse wave (STW) device is used as a physical transducer. It is confirmed that STW sensor devices coated with PPAa films provide high sensitivity for moisture. The STW sensor device with a 63 nm PPAa film provided twenty four times higher sensitivity than that of a non-coated STW device. In addition, the chemical structure of PPAa films is characterized by the FT-IR and the contact angle measurement.

Swelling signals of polymer films measured by a combination of micromechanical cantilever sensor and surface plasmon resonance spectroscopy

Swelling of plasma-polymerized allylamine (PPAA) films has been investigated by using a combination of micromechanical cantilever sensor (MCS) and surface plasmon resonance (SPR) spectroscopy. The bending responses of the polymer-coated MCS were compared with simultaneously measured reflectivity changes recorded by SPR for both, highly and low crosslinked plasma-polymerized films in N 2 atmospheres with different humidity. Signals attributed to reversible swelling for both plasma polymers were obtained. With increasing the humidity, the thickness increase of a highly crosslinked film was lower than that of a low crosslinked film. In contrast, the MCS coated with a highly crosslinked film exhibited a larger deflection. This demonstrates that a plasma-polymerized allylamine film of higher crosslink density can transduce more efficiently the swelling to the MCS bending than a film of lower crosslink density under identical environmental conditions.

X-Ray and Neutron Reflectometry Study of Glow-Discharge Plasma Polymer Films

Radio-frequency glow-discharge plasma polymer thin films of allylamine (AA) and hexamethyldisiloxane (HMDSO) were prepared on silicon wafers and analyzed by a combination of X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), X-ray reflectometry (XRR), and neutron reflectometry (NR). AFM and XRR measurements revealed uniform, smooth, defect-free films of 20-30 nm thickness. XPS measurements gave compositional data on all elements in the films with the exception of hydrogen. In combination with XRR and NR, the film composition and mass densities (1.46 and 1.09 g cm(-)(3) for AA and HMDSO, respectively) were estimated. Further NR measurements were conducted with the AA and HMDSO films in contact with water at neutral pH. Three different H(2)O/D(2)O mixtures were used to vary the contrast between the aqueous phase and the polymer. The amount of water penetrating the film, as well as the number of labile protons present, was determined. The AA film in contact with water was found to swell by approximately 5%, contain approximately 3% water, and have approximately 24% labile protons. The HDMSO polymer was found to have approximately 6% labile protons, no thickness increase when in contact with water, and essentially no solvent penetration into the film. The difference in the degree of proton exchange within the films was attributed to the substantially different surface and bulk chemistries of the two films.

Microstructural evolution of allylamine polymerized plasma films

The present paper deals with the characterization of plasma polymerized allylamine films. The films were characterized using a large panel of techniques such as Fourier transformation infrared spectroscopy, X-ray photoemission spectroscopy and ellipsometry. The film microstructure was investigated as a function of the deposition power while other process parameters (gas mixture flow, pressure) were kept constant. The microstructure shows a strong dependence on the deposition power. A power transition has been identified outlining two deposition modes in agreement with a growth model developed for carbon nitride thin films. Conditions of deposition closed to this transition provide a film microstructure interesting for absorption and adhesion of biomolecules i.e. high NH 2 content, high porosity and high deposition rate.