Nitrogen-rich coatings for promoting healing around stent-grafts after endovascular aneurysm repair

Comparison of Plasma-Polymerized Thin Films Deposited from 2-Methyl-2-oxazoline and 2-Ethyl-2-oxazoline: I Film Properties

Poly(2-oxazoline) is a promising new class of polymeric materials due to their antibiofouling properties and good biocompatibility. Poly(2-oxazoline) coatings can be deposited on different substrates via plasma polymerization, which can be more advantageous than other coating methods. The aim of this study is to deposit poly(2-oxazoline) coatings using a surface dielectric barrier discharge burning in nitrogen at atmospheric pressure using 2-methyl-2-oxazoline and 2-ethyl-2-oxazoline vapours as monomers and compare the film properties. For the comparison, the antibacterial and cytocompatibility tests were peformed according to ISO norms. The antibacterial tests showed that all the deposited films were highly active against Staphylococcus aureus and Escherichia coli bacteria. The chemical composition of the films was studied using FTIR and XPS, and the film surface's properties were studied using AFM and surface energy measurement. The cytocompatibility tests showed good cytocompatibility of all the deposited films. However, the films deposited from 2-methyl-2-oxazoline exhibit better cytocompatibility. This difference can be explained by the different chemical compositions and surface morphologies of the films deposited from different monomers.

Atmospheric Pressure Plasma Polymerized 2-Ethyl-2-oxazoline Based Thin Films for Biomedical Purposes

Polyoxazoline thin coatings were deposited on glass substrates using atmospheric pressure plasma polymerization from 2-ethyl-2-oxazoline vapours. The plasma polymerization was performed in dielectric barrier discharge burning in nitrogen at atmospheric pressure. The thin films stable in aqueous environments were obtained at the deposition with increased substrate temperature, which was changed from 20 ∘C to 150 ∘C. The thin film deposited samples were highly active against both S. aureus and E. coli strains in general. The chemical composition of polyoxazoline films was studied by FTIR and XPS, the mechanical properties of films were studied by depth sensing indentation technique and by scratch tests. The film surface properties were studied by AFM and by surface energy measurement. After tuning the deposition parameters (i.e., monomer flow rate and substrate temperature), stable films, which resist bacterial biofilm formation and have cell-repellent properties, were achieved. Such antibiofouling polyoxazoline thin films can have many potential biomedical applications.

Atmospheric Pressure Plasma Polymerized Oxazoline-Based Thin Films-Antibacterial Properties and Cytocompatibility Performance

Polyoxazolines are a new promising class of polymers for biomedical applications. Antibiofouling polyoxazoline coatings can suppress bacterial colonization of medical devices, which can cause infections to patients. However, the creation of oxazoline-based films using conventional methods is difficult. This study presents a new way to produce plasma polymerized oxazoline-based films with antibiofouling properties and good biocompatibility. The films were created via plasma deposition from 2-methyl-2-oxazoline vapors in nitrogen atmospheric pressure dielectric barrier discharge. Diverse film properties were achieved by increasing the substrate temperature at the deposition. The physical and chemical properties of plasma polymerized polyoxazoline films were studied by SEM, EDX, FTIR, AFM, depth-sensing indentation technique, and surface energy measurement. After tuning of the deposition parameters, films with a capacity to resist bacterial biofilm formation were achieved. Deposited films also promote cell viability.

Poly(polyol sebacate) Elastomers as Coatings for Metallic Coronary Stents

Biocompatible polymeric coatings for metallic stents are desired, as currently used materials present limitations such as deformation during degradation and exponential loss of mechanical properties after implantation. These concerns, together with the present risks of the drug-eluting stents, namely, thrombosis and restenosis, require new materials to be studied. For this purpose, novel poly(polyol sebacate)-derived polymers are investigated as coatings for metallic stents. All pre-polymers reveal a low molecular weight between 3000 and 18 000 g mol^-1 . The cured polymers range from flexible to more rigid, with E-modulus between 0.6 and 3.8 MPa. Their advantages include straightforward synthesis, biodegradability, easy processing through different scaffolding techniques, and easy transfer to industrial production. Furthermore, electrospraying and dip-coating procedures are used as proof-of-concept to create coatings on metallic stents. Biocompatibility tests using adipose stem cells lead to promising results for the use of these materials as coatings for metallic coronary stents.

Antibiofouling Properties of Plasma-Deposited Oxazoline-Based Thin Films

Infections caused by the bacterial colonization of medical devices are a substantial problem to patients and healthcare. Biopassive polyoxazoline coatings are attracting attention in the biomedical field as one of the potential solutions to this problem. Here, we present an original and swift way to produce plasma-deposited oxazoline-based films for antifouling applications. The films developed via the plasma deposition of 2-methyl-2-oxazoline and 2-ethyl-2-oxazoline have tunable thickness and surface properties. Diverse film chemistries were achieved by tuning and optimizing the deposition conditions. Human-derived fibroblasts were used to confirm the biocompatibility of oxazoline derived coatings. The capacity of the coatings to resist biofilm attachment was studied as a function of deposition power and mode (i.e., continuous wave or pulsed) and precursor flow rates for both 2-methyl-2-oxazoline and 2-ethyl-2-oxazoline. After careful tuning of the deposition parameters films having the capacity to resist biofilm formation by more than 90% were achieved. The substrate-independent and customizable properties of the new generation of plasma deposited oxazoline thin films developed in this work make them attractive candidates for the coating of medical devices and other applications where bacteria surface colonization and biofilm formation is an issue.

A versatile star PEG grafting method for the generation of nonfouling and nonthrombogenic surfaces

Polyethylene glycol (PEG) grafting has a great potential to create nonfouling and nonthrombogenic surfaces, but present techniques lack versatility and stability. The present work aimed to develop a versatile PEG grafting method applicable to most biomaterial surfaces, by taking advantage of novel primary amine-rich plasma-polymerized coatings. Star-shaped PEG covalent binding was studied using static contact angle, X-ray photoelectron spectroscopy (XPS), and quartz crystal microbalance with dissipation monitoring (QCM-D). Fluorescence and QCM-D both confirmed strong reduction of protein adsorption when compared to plasma-polymerized coatings and pristine poly(ethyleneterephthalate) (PET). Moreover, almost no platelet adhesion was observed after 15 min perfusion in whole blood. Altogether, our results suggest that primary amine-rich plasma-polymerized coatings offer a promising stable and versatile method for PEG grafting in order to create nonfouling and nonthrombogenic surfaces and micropatterns.

Chondroitin sulfate and epidermal growth factor immobilization after plasma polymerization: a versatile anti-apoptotic coating to promote healing around stent grafts

Bioactive coatings constitute an interesting approach to enhance healing around implants, such as stent-grafts used in endovascular aneurysm repair. Three different plasma techniques, namely NH₃ plasma functionalization and atmospheric- or low-pressure plasma polymerization, are compared to create amino groups and covalently bind CS and EGF bioactive molecules on PET. The latter presents the greatest potential. CS + EGF coating is shown to strongly decrease cell apoptosis and cell depletion in serum-free medium, while increasing cell growth compared to unmodified PET. This versatile biomimetic coating holds promise in promoting vascular repair around stent-grafts, where resistance to apoptosis is a key issue.

Biomechanical and histologic analysis in aortic endoprosthesis using fibrin glue

BACKGROUND

The absence of incorporation between endoprosthesis (EP) and the arterial wall may lead to device migration and endoleaks around the stent graft. Alternatives have been tested aiming to improve this incorporation. Fibrin glue is used in many operating procedures promoting adhesion and tissue regeneration; however, its use to improve EP incorporation by arteries is unknown.

OBJECTIVE

The objective of this study was to analyze dislodgement forces needed to extract the EPs implanted in pig aorta, compare different oversizing and fibrin glue injections, and to analyze histologic changes among groups.

METHODS

Straight EPs were implanted in the thoracic aorta of pigs using 10% oversizing plus fibrin glue in the interface between the EP and the artery (group 1), using 20% oversizing (group 2), and 10% oversizing (group 3). Fourteen days after the implant, the animals were killed to enable biomechanical analysis of the EP and to verify histologic changes of the aortic wall and its interface with the EP.

RESULTS

Group 1 showed a dislodgement force of 21.9 ± 5.3 Newton (N) being higher than the other groups and statistically significant when compared to group 3 (15.6 ± 3.6N), P = .003%. Group 2 had a higher dislodgement force and statistically more significant than group 3 (19.5 ± 7.8N). Histologic analysis showed tissue reaction with inflammatory cells and fibroblasts higher in group 1 and group 2 compared to group 3.

CONCLUSION

This study reports a large animal survival model of thoracic aortic stent graft placement by testing the impact of fibrin glue on EP incorporation. Compared to oversizing alone, fibrin glue placed between the stent graft and the arterial wall increases EP incorporation. Additional studies are needed to determine the potential utility of fibrin glue in the setting of human arterial endografts.

Fatores envolvidos na migração das endopróteses em pacientes submetidos ao tratamento endovascular do aneurisma da aorta abdominal

A migração da endoprótese é complicação do tratamento endovascular definida como deslocamento da ancoragem inicial. Para avaliação da migração, verifica-se a posição da endoprótese em relação a determinada região anatômica. Considerando o aneurisma da aorta abdominal infrarrenal, a área proximal de referência consiste na origem da artéria renal mais baixa e, na região distal, situa-se nas artérias ilíacas internas. Os pacientes deverão ser monitorizados por longos períodos, a fim de serem identificadas migrações, visto que estas ocorrem normalmente após 2 anos de implante. Para evitar migrações, forças mecânicas que propiciam fixação, determinadas por características dos dispositivos e incorporação da endoprótese, devem predominar sobre forças gravitacionais e hemodinâmicas que tendem a arrastar a prótese no sentido caudal. Angulação, extensão e diâmetro do colo, além da medida transversa do saco aneurismático, são importantes aspectos morfológicos do aneurisma relacionados à migração. Com relação à técnica, não se recomenda implante de endopróteses com sobredimensionamento excessivo (> 30%), por provocar dilatação do colo do aneurisma, além de dobras e vazamentos proximais que também contribuem para a migração. Por outro lado, endopróteses com mecanismos adicionais de fixação (ganchos, farpas e fixação suprarrenal) parecem apresentar menos migrações. O processo de incorporação das endopróteses ocorre parcialmente e parece não ser suficiente para impedir migrações tardias. Nesse sentido, estudos experimentais com endopróteses de maior porosidade e uso de substâncias que permitam maior fibroplasia e aderência da prótese à artéria vêm sendo realizados e parecem ser promissores. Esses aspectos serão discutidos nesta revisão.

Chondroitin-4-Sulfate: A Bioactive Macromolecule to Foster Vascular Healing around Stent-Grafts after Endovascular Aneurysm Repair

Deficient healing after endovascular aneurysm repair with a stent-graft is thought to be related to pro-apoptotic environment in abdominal aortic aneurysms and inertness of graft materials. We developed a bioactive coating containing chondroitin-4-sulfate and assessed its potential to improve cell adhesion, viability and resistance to apoptosis on PET surfaces. Coatings of collagen type I and CS were prepared and characterized by DMMB, FT-IR, DSC, SEM and contact angle goniometry. Preliminary cell culture experiments with vascular smooth muscle cells showed increased adhesion and viability in serum-free medium on CS-coated surfaces compared to control PET films.