Plasma Polymerized Allylamine Films Research Articles

From surface to bulk modification: Plasma polymerization of amine-bearing coating by synergic strategy of biomolecule grafting and nitric oxide loading

Integration of two or more biomolecules with synergetic and complementary effects on a material surface can help to obtain multi-functions for various biomedical applications. However, the amounts of biomolecules integrated and their physiological functions are compromised due to the limited surface anchoring sites. Herein, we propose a novel concept of film engineering strategy “from surface to bulk synergetic modification”. This new concept is realized by employing the surface amine groups of plasma polymerized allylamine (PPAm) film for grafting a molecule e.g., thrombin inhibitor, bivalirudin (BVLD), meanwhile its bulk amine groups is used as a universal depot for storing and releasing therapeutic nitric oxide (NO) gas as supplement to the functions of BVLD. It is demonstrated that such a “from surface to bulk synergetic modification” film engineering can impart the modified-substrates with anti-platelet and anti-coagulant dual functions, giving rise to a highly endothelium-mimetic thromboresistant property. We believe that our research provides a very promising strategy to deliver multifunctional surface versatilely that require NO release in combination with other properties, which will find broad biomedical applications in blood-contacting devices, and et al. Moreover, it also provides a brand-new film engineering strategy for tailoring surface multi-functionalities of a wide range of materials.

Young's modulus of plasma‐polymerized allylamine films using micromechanical cantilever sensor and laser‐based surface acoustic wave techniques

Mechanical properties of ultra‐thin organic films are fundamentally important in coating applications. Micromechanical cantilever sensor (MCS) and laser‐based surface acoustic wave (LA‐SAW) techniques were both used to measure Young's moduli (E) of plasma polymerized films at different humidities (H). For plasma polymerized allylamine (ppAA) films deposited at 5 W and 90 W, E of 1400 ± 350 MPa and 110 ± 20 MPa at H between 10 and 40%, and 1070 ± 250 MPa and 32 ± 10 MPa at H between 70 and 80% were measured. The LA‐SAW technique revealed E lower than 60% of that measured by MCS. The difference suggested either an enhanced swelling at the air interface or a gradient of cross‐linking density.

A Cell-Adhesive Plasma Polymerized Allylamine Coating Reduces the In Vivo Inflammatory Response Induced by Ti6Al4V Modified with Plasma Immersion Ion Implantation of Copper.

Copper (Cu) could be suitable to create anti-infective implants based on Titanium (Ti), for example by incorporating Cu into the implant surface using plasma immersion ion implantation (Cu-PIII). The cytotoxicity of Cu might be circumvented by an additional cell-adhesive plasma polymerized allylamine film (PPAAm). Thus, this study aimed to examine in vivo local inflammatory reactions for Ti6Al4V implants treated with Cu-PIII (Ti-Cu), alone or with an additional PPAAm film (Ti-Cu-PPAAm), compared to untreated implants (Ti). Successful Cu-PIII and PPAAm treatment was confirmed with X-ray Photoelectron Spectroscopy. Storage of Ti-Cu and Ti-Cu-PPAAm samples in double-distilled water for five days revealed a reduction of Cu release by PPAAm. Subsequently, Ti, Ti-Cu and Ti-Cu-PPAAm samples were simultaneously implanted into the neck musculature of 24 rats. After 7, 14 and 56 days, peri-implant tissue was retrieved from 8 rats/day for morphometric immunohistochemistry of different inflammatory cells. On day 56, Ti-Cu induced significantly stronger reactions compared to Ti (tissue macrophages, antigen-presenting cells, T lymphocytes) and to Ti-Cu-PPAAm (tissue macrophages, T lymphocytes, mast cells). The response for Ti-Cu-PPAAm was comparable with Ti. In conclusion, PPAAm reduced the inflammatory reactions caused by Cu-PIII. Combining both plasma processes could be useful to create antibacterial and tissue compatible Ti-based implants.

Optimizing Humic Acid Removal by Modifying the Surface Chemistry of Plasma Polymerized Allylamine Coated Particles

Plasma polymerized allylamine films were deposited onto quartz particles at low pressure to optimize humic acid removal by varying the plasma power, flow rate, and polymerization times. Increasing the plasma power increased the number of positively charged groups and humic acid removal. Increasing the allylamine flow rate increased the number of positively charged groups but maximum humic acid removal was observed at 6.48 sccm due to humic acid removal by positively charged and uncharged crosslinked species. Longer polymerization times increased the number of positively charged groups while similar humic acid removal resulted as the larger humic acid molecule cannot penetrate as readily into the film as the acid orange 7 used to determine the number of positively charged groups. Manipulation of the plasma parameters has shown to provide significant control over humic acid removal.

Multifunctional Plasma-Polymerized Film: Toward Better Anticorrosion Property, Enhanced Cellular Growth Ability, and Attenuated Inflammatory and Histological Responses.

Over the past few decades, plasma surface modification technique has been widely used to selectively improve surface properties and biocompatibility of materials. In this paper, at first a simple and effective method for the deposition of plasma-polymerized allylamine films onto 316L stainless steel (SS) from an allylamine/nitrogen gas mixture was developed. These amine-rich films were characterized by grazing incidence attenuated total reflection Fourier transform infrared spectroscopy (GATR-FTIR) and X-ray photoelectron spectroscopy (XPS), and the anticorrosion properties were demonstrated by electrochemical analysis. Micro-BCA and quartz crystal microbalance with dissipation (QCM-D) results showed that the higher density of amine groups of the allylamine-nitrogen plasma-polymerized film contributes to more serum protein adsorption which may enhance the adhesion and growth of cells on biomaterials. The in vitro and in vivo anti-inflammatory evaluation was performed and it has been confirmed that these nitrogen-rich surfaces could inhibit the activation of macrophages by down-regulation of the pro-inflammatory cytokines TNF-α and IL-6, and exhibit acceptable tissue-compatibility. It was found that with the help of nitrogen, plasma-polymerized allylamine films presented superior biological properties and provided a high potential application in surface modification of biomedical substrate with desirable clinical performance.

Immobilization of DNA aptamers via plasma polymerized allylamine film to construct an endothelial progenitor cell-capture surface

The endothelial progenitor cells (EPCs) capture stent has drawn increasing attentions and become one of the most promising concepts for the next generation vascular stent. In this regard, it is of great significance to immobilize a molecule with the ability to bind EPC for rapid in vivo endothelialization with high specificity. In this work, a facile two-step method aimed at constructing a coating with specific EPC capturing aptamers is reported. The processes involves as the first-step deposition of plasma polymerized allylamine (PPAam) on a substrate to introduce amine groups, followed by the electrostatic adsorption of a 34 bases single strand DNA sequence to the PPAam surface as a second step (PPAam-DNA). Grazing incidence attenuated total reflection Fourier transform infrared spectroscopy (GATR-FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the successful immobilization of the aptamers. Quartz crystal microbalance with dissipation (QCM-D) real time monitoring result shows that about 175ng/cm2 aptamers were conjugated onto the PPAam surface. The interactions between the modified surfaces and human umbilical vein endothelial cells (ECs), smooth muscle cells (SMCs), and murine induced EPCs derived from mesenchymal stem cells (MSCs) were also investigated. It was demonstrated that PPAam-DNA samples could capture more EPCs, and present a cellular friendly surface for the proliferation of both EPCs and ECs but no effect on the hyperplasia of SMCs. Also, the co-culture results of 3 types of cells confirmed that the aptamer could specifically bond EPCs rather than ECs and SMCs, suggesting the competitive adhesion advantage of EPCs to ECs and SMCs. These data demonstrate that the EPC aptamer has large potential for designing an EPC captured stent and other vascular grafts with targeted in situ endothelialization.

Removal of Acid Orange 7 Dye from Water Via Plasma-Polymerized Allylamine-Coated Quartz Particles

A novel method of acid orange 7 (AO7) removal has been developed via the deposition of plasma-polymerized allylamine (ppAA) films on quartz particles. ppAA films were deposited at a power of 25 W, allylamine flow rate of 4.4 sccm and polymerization time of 5 to 60 min. Polymerization time had a significant effect on surface chemistry where the XPS nitrogen concentration, XPS C-O, C-N concentration, isoelectric point and the number of positively charged groups per nm2 all increased with increasing polymerization time. Increasing polymerization time increased AO7 adsorption due to greater concentrations of positively charged amine groups on the surface. The pH and initial AO7 concentration were varied to investigate their effect on AO7 adsorption. Increasing the initial AO7 concentration increased adsorption for all polymerization times. pH had a significant effect on AO7 adsorption with maximum adsorption at pH 3 and significantly less at pH values of 5–9. Regeneration of ppAA-coated quartz particles for up to 4 cycles using pH 12 Milli-Q water resulted in only slight losses in adsorption capacities. ppAA-coated particles have shown to successfully remove AO7 dye from solution and therefore demonstrate potential for use in the treatment of industrial dye wastestreams.

Influence of Particle Mass and Flow Rate on Plasma Polymerized Allylamine Coated Quartz Particles for Humic Acid Removal

Plasma polymerized allylamine films were deposited onto quartz particles for the removal of humic acid, a common water contaminant. Allylamine flow rates of 6.6 and 11.5 standard cubic centrimetres per minute (sccm) were used and the mass of particles varied from 50 to 500 g. At an allylamine flow rate of 6.6 sccm, the atomic concentration of carbon and nitrogen decreased with increasing mass of particles. The isoelectric point and number of positively charged amine groups increased as the allylamine flow rate was increased and/or the mass of particles coated was decreased. Greater humic acid removal was achieved by increasing the allylamine flow rate and/or decreasing the mass of particles coated, which will have important implications for its use in water purification.

Constructing Biomimic Catalytic Coating with Controlled Nitric Oxide Release Properties by Immobilizing 3,3-Diselenodipropionic Acid on Plasma Polymerized Allylamine Film

Nitric oxide (NO) is a signaling molecule that plays a pivotal role in the diagnosis, treatment, and prevention of life threatening cardiovascular disorders. In this work, a facile method to construct catalytic coating with controlled NO release properties has been developed. The process involves in the first-step the deposition of plasma polymerized allylamine coating to introduce amine groups onto the titanium foils, followed by covalently immobilizing 3,3-diselenodipropionic acid (SeDPA), which is an organoselenium compound mimicking glutathione peroxidase-like catalytic production of NO. The NO release correlated positively with the –Se–Se– content in the functionalized film. After 15 d exposure to an NO donor, the –Se–Se– group was well retained with good biostability and ability of NO generation.

Direct amination of boron‐doped diamond by plasma polymerized allylamine film

A novel microwave pulsed‐plasma based method for the modification of the hydrogen‐terminated polycrystalline boron‐doped diamond (BDD) with a thin film of polymerized allylamine (PPAAm) is reported. A modified BDD surface is resistant to hydrolysis and delamination and is characterized by a high density of positively charged amino groups. Pulsed microwave plasma was applied to improve the degree of cross‐linking and bonding of the plasma polymeric films to BDD. The primary amino groups of the amine‐modified Si/BDD surface were coupled with antraquinone derivatives as model electroactive compounds. Synthesized thin BDD‐PPAAm films were investigated with X‐ray photoelectron spectroscopy (XPS), laser induced fluorescence (LIF) and Fourier transform infrared spectroscopy (FT‐IR). The FT‐IR studies confirm that the molecular structure of the deposited layer reproduces the monomer structure with a partial transformation of amino groups into amide and nitrile. XPS results show that PPAAm film on an Si/BDD electrode is electrochemically stable within the range of polarization potentials between −1.1 and +1.1 V. The fluorescence properties of the PPAAm modified BDD surface makes its promising for application in sensors with optical readout. At the same time, the PPAAm film's durability investigated over a wide potential range makes it ideal for electrochemical sensors.

Influence of Film Stability and Aging of Plasma Polymerized Allylamine Coated Quartz Particles on Humic Acid Removal

Plasma polymerized allylamine (ppAA) films have been successfully deposited on to the surface of quartz particles via a rotating barrel plasma reactor for humic acid removal. The films were deposited at a power of 25 W, allylamine flow rate of 4.4 sccm and polymerization times of 5 to 60 min. X-ray photoelectron spectroscopy was used to investigate the influence of short-term stirring in water and film age on surface chemistry. Stirring results in a reduction in the nitrogen concentration, which was greatest for shorter polymerization times. Film aging of up to 52 weeks appeared to result in a reduction in the concentration of C-N species. The influence of batch, recycling, and film age on humic acid removal was investigated. Humic acid removal appeared to be reproducible across three separate batches for polymerization times of 20 min or more, which was attributed to film thickness. Recycling of the ppAA films was most successful at pH 11 for up to 4 humic acid removal/regeneration cycles. Successful regeneration at pH 11 was attributed to electrostatic repulsion of the adsorbed humic acid molecules. Decreasing the pH of the regeneration solution reduced the number of successful regeneration cycles due to greater retention of adsorbed humic acid via electrostatic attraction. Film age appears to have minimal effect on humic acid removal where freshly deposited and 52-week-old films removed similar masses of humic acid. Successful production and development of ppAA coated quartz particles has resulted in a functional material that can be incorporated into a water treatment system to improve water quality.

In vitro corrosion inhibition on biomedical shape memory alloy by plasma-polymerized allylamine film

To improve the corrosion resistance of biomedical nickel titanium (NiTi) alloy, a polymeric allylamine film is deposited by plasma polymerization. The chemical composition, surface morphology, and thickness of the polymer film are investigated with X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The corrosion behavior of the coated NiTi and bare NiTi samples is compared by polarization test and electrochemical impedance spectroscopy (EIS) in simulated body fluid. The results show that the polymeric film lowers the corrosion current density and increases the polarization resistance, indicating improved corrosion resistance. The plasma polymerized coating is expected to reduce corrosion risks of biomedical NiTi alloy in clinical use.

Construction and hemocompatibility study of highly bioactive heparin‐functionalized surface

A simple method is developed to construct anticoagulant surfaces via passive adsorption of heparin onto the protonated plasma-polymerized allylamine (PPAam) films from phosphate-buffered saline (PBS). These protonated PPAam surfaces are found to have high affinity to heparin. Importantly, the heparin-functionalized PPAam (Hep-PPAam) surfaces show good retention of heparin after long-term immersion in PBS. The Hep-PPAam surface prolongs the activated partial thromboplastin time for about 20 s as compared to 316L stainless steel even though the adsorption amount of heparin is only about 300 ng/cm(2). This indicates that the heparin bound to the protonated PPAam surfaces in this way maintains a high bioactivity. Blood platelet adhesion and activation on this surface is remarkably reduced and adsorption and activation of fibrinogen is inhibited. Thus, Hep-PPAam surface modification leads to a significant improve of the hemocompatibility.

Plasma polymerized allylamine coated quartz particles for humic acid removal

Allylamine plasma polymerization has been used to modify the surface of quartz particles for humic acid removal via an inductively coupled rotating barrel plasma reactor. Plasma polymerized allylamine (ppAA) films were deposited at a power of 25W, allylamine flow rate of 4.4sccm and polymerization times of 5–60min. The influence of polymerization time on surface chemistry was investigated via X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectrometry (ToF-SIMS) and electrokinetic analysis. Acid orange 7 adsorption/desorption quantified the number of surface amine groups. Humic acid removal via ppAA quartz particles was examined by varying pH, removal time, humic acid concentration, and particle mass. Increasing the polymerization time increased the concentration of amine groups on the ppAA quartz surface, thus also increasing the isoelectric point. ToF-SIMS demonstrated uniform distribution of amine groups across the particle surface. Greatest humic acid removal was observed at pH 5 due to electrostatic attraction. At higher pH values, for longer polymerization times, humic acid removal was also observed due to hydrogen bonding. Increasing the initial humic acid concentration increased the mass of humic acid removed, with longer polymerization times exhibiting the greatest increases. Plasma polymerization using a rotating plasma reactor has shown to be a successful method for modifying quartz particles for the removal of humic acid. Further development of the plasma polymerization process and investigation of additional contaminants will aid in the development of a low cost water treatment system.

A multi-ion beam microanalysis approach for the characterization of plasma polymerized allylamine films

A full characterization of plasma polymerized biofunctional films requires the use of multi-analytical approaches to determine the chemical composition, topography and potential interaction mechanisms of such films with biomolecules and cells. In this work we aim at underlining the versatility of ion-based techniques to contribute to the chemical characterization of plasma polymerized surfaces. The simultaneous use of energy recoil detection (ERD) and Rutherford backscattering (RBS) spectroscopies with incident He ions is an example of this versatility. Performing sequential measurements and the use of correlating computing tools for ERD-RBS interpretation allows providing in-depth concentration profiles of light elements, including namely hydrogen. More accurate analysis of light elements in polymer films can be increased by looking for particular ions with resonant backscattering responses (i.e., non-Rutherford Scattering). In particular, proton beams of 1.765 MeV are used to increase the detection of C and N, and particular incidence and detector angles to diminish the Si substrate contribution. These analytical tools have been applied to allylamine films and multi-layers crosslinked in a capacitive plasma onto both Si and porous Si substrates.

Chemical reactivity of plasma polymerized allylamine (PPAA) thin films on Au and Si: Study of the thickness influence and aging of the films

In this work, we investigate the surface reactivity of substrates coated with thin layers (estimated thickness ≤30nm) of plasma polymerized allylamine films (PPAA), an amine-functionalized polymer deposited by plasma-enhanced chemical vapor deposition (PECVD) with radiofrequency (RF) discharges. Our results show that very thin layers, or islands, can retain on their surface molecules that are able to react through their NH2 functions. We have tested and assessed by X-Ray Electron Spectroscopy (XPS) and Quartz Crystal Microbalance (QCM) the surface density of chemical functions vs. layer thicknesses by using chemical derivatization with two types of agents: imine formation by a reaction of primary amine from the coating with aldehyde (Pentafluorobenzaldehyde, PFBA) and amide-bond formation by reaction with an activated carboxylic group (Succinimidyl Succinate Terminated Polyethylene glycol, EGSS). Results show that the PPAA coatings—even for very thin layers of a few nanometers—promote the chemisorption of the tagging molecules. The aging under air and evolution of reactive amine surface concentration with time under air are also presented.

Organic Gas Sorption on Plasma-Polymerized Allylamine Films Coated with Quartz Crystal Microbalance

Organic Gas Sorption on Plasma-Polymerized Allylamine Films Coated with Quartz Crystal Microbalance

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.

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