Polymers have been widely used for biomedical purposes such as medical devices, tissue engineering scaffolds, and drug carriers for drug delivery system (DDS). Using polymers for such medical devices ...should be entirely sensible, as polymers are generally very soft, highly cost-effective, and relatively biocompatible. In order to encourage further development in the biocompatibility of the polymers for the enhanced use of the materials, the functionalization of the polymer surfaces has been deliberately introduced. Plasma modification is one of the most efficient ways for the surface treatment of polymers, since plasma treatment could selectively modify the chemical and the physical properties of the surface of the polymers by not affecting the original bulk characteristics of the polymers. Also, plasma surface modification offers shorter treatment time as compared with other surface modification methods. When plasma was applied to the polymer surface, functional groups, graft polymerization, coatings, and molecular crosslinking formation would be introduced with or without the change in the surface roughness of the polymer. The highly functionalized polymers by the plasma modifications would be effectively used for the materials in tissue engineering or drug delivery systems. In this paper, the fabrication and the characterization of polymers by several types of plasma treatments are reviewed, followed by the introduction of their applications to the materials in drug delivery systems and tissue engineering.
•Studies on plasma treatments of polymers for biomedical applications are reviewed.•Achievements in biocompatibility by plasma treatments are discussed.•Plasma-modified polymeric surfaces were studied for structural characterization.•Biocompatibility and mechanical property of DLC-related coatings were summarized.•Plasma technique is a promising modification tool for DDS and tissue engineering.
Plasma surface treatment was investigated as a surface modification method for a drug-eluting stent (DES) coated with polymers. Currently, the implantation of the DES is the most efficient way to ...treat a coronary artery disease. DES elutes anti-proliferative drugs that suppress proliferation of smooth muscle cells in the stented segment of the artery. Despite the impressive reduction in restenosis by DES, it still occasionally has a major disadvantage for not preventing restenosis at an implant site due to the relatively vast drug release from the stent surface in the early stages of the drug release. To solve the problem, we studied plasma treatments on the polymer surface because there would not be a substantial risk of damaging the bulk properties of the polymer and the stent by plasma surface treatments. In this study, argon, oxygen, and nitrogen were selected as working gases and poly(ethylene-co-vinyl acetate) (EVA), a hydrophobic biomedical polymer, was selected as a base drug-reservoir material for DES. Structural analyses were carried out by water contact angle measurements, X-ray photon spectroscopy (XPS), and the evaluation of the crosslinking degree of EVA polymer. It was found that the initial burst-release and the cumulative released amount of the drug were both effectively suppressed by controlling the plasma processing time. Furthermore, less effective control of the drug release was obtained by using nitrogen or oxygen plasma as a processing gas instead of argon plasma. According to the evaluation of the crosslinking degree, it was found that argon plasma could most effectively induce the crosslinking in EVA, while nitrogen and oxygen plasmas came in second and third, respectively, which corresponded to the results of the drug release experiments. It was expected that the experimental results of the plasma treatments could provide a new and alternative approach to a controllable and sustainable drug release system.
► Plasma treatment was introduced for the control of drug release from medical polymer. ► Reduction in drug release was observed by Ar, N2, and O2 plasma treatments. ► Most effective drug control was observed for Ar plasma-treated polymer. ► Ar plasma most effectively induced crosslinking on the surface of polymer. ► Degree of crosslinking in the polymer determined the drug release profile of polymer.
Application of nickel‑titanium (NiTi) alloys to medical implant devices is increasing due to their unique characteristics. However, many reports show adverse effects of corrosion of the alloys due to ...implantation in human body. To ensure good biocompatibility in the human body, fluorine-doped amorphous carbon (a-C:H:F) coating is a promising candidate. Generally, a-C:H:F coating shows poor adhesion on metallic alloys, so that silicon-incorporated interlayer is introduced between a-C:H:F and metallic alloys. However, this membrane design has a risk of delamination at the outermost interface (a-C:H:F//interlayer), and also there is a practical problem that coating time becomes long because the deposition process in multiple stages is required. Here we develop silicon and fluorine doped amorphous carbon (a-C:H:Si:F) film which exhibits high adhesion and excellent biocompatibility. One of the a-C:H:Si:F films “C2H2-doped”, which was deposited using a mixture of TMS, C2H2 and C3F8, showed higher adhesive strength than a-C:H:F with Si-interlayer and the same number of adhesive platelets and leukocytes as a-C:H:F. This result demonstrated that a single film with both adhesion of Si-interlayer and biocompatibility of a-C:H:F was fabricated. Furthermore, this a-C:H:Si:F coating can be anticipated as an effective film coating method in a practical point of view, because the film deposition is completed in one process.
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•Single-layered silicon and fluorine doped amorphous carbon (a-C:H:Si:F) films were fabricated from TMS, C3F8 and C2H2.•The properties and structures of a-C:H:Si:F films were controlled by source gas flow rate.•The a-C:H:Si:F film whose Si and F was optimally controlled showed both excellent adhesive strength and biocompatibility.
OBJECTIVE: To retrospectively evaluate the clinical outcomes of pre-operative endovascular coil embolisation (ECE) for chronic pulmonary aspergillosis (CPA).METHODS: We evaluated surgical patients ...with CPA between November 2016 and April 2020. Pre-operative ECE for
CPA with severe adhesions was selectively performed to reduce intra-operative blood loss. ECE procedures, operative procedures, intra-operative blood loss and complications were evaluated.RESULTS: Twenty-eight patients (21 males and 7 females; median age: 55 years) were included
in the study. Of the 28 patients, 8 (28.6%) underwent pre-operative ECE. Technical success rate in pre-operative ECE was 100%. The median time required for ECE procedures was 123 min. The median number of vessels embolised per procedure was 2.5. The median period between embolisation and surgery
was 5 days. Major complications were observed in three patients (10.7%). There were no significant differences between patients with and without pre-operative ECE in operative time (284 vs. 365 min, respectively, P = 0.7602) and intra-operative blood loss (294 vs. 228 mL, respectively,
P = 0.8987).CONCLUSIONS: Pre-operative ECE for CPA appears to be feasible and safe; however, its role in reducing intra-operative blood loss needs further investigation.
This study aims at reproducing deformation-induced kink morphologies, together with the recently-reported AE measurement-based energy releasing characteristics, based on FTMP (Field Theory of ...Multiscale Plasticity)-incorporated crystal plasticity finite element simulation for single crystal Mg under c-axis plane strain compression condition. Two models either with the well-defined deformation twin system or a rank-1 connection-based kink system are considered, respectively, as the projection direction for the incompatibility tensor to be used in the constitutive model. The twin model yields “kink-like morphology” of growing kind, but fails to capture one of the energy releasing characteristics. The kink model, on the other hand, is demonstrated to be able to reproduce basically all the features, i.e., not only the “kink” morphology but also the AE energy-based features.
The hemocompatibility of plasma-treated, silicon-incorporated, diamond-like carbon (Si-DLC) films was investigated. Si-DLC films with a Si concentration of 2
at.% were prepared on Si (100) or Nitinol ...substrates using a capacitively coupled radiofrequency plasma-assisted chemical vapor deposition method using a mixed gas of benzene (C
6H
6) and diluted silane (SiH
4:H
2
=
10:90). The Si-DLC films were then treated with O
2, CF
4 or N
2 glow discharge for surface modification. The plasma treatment revealed an intimate relationship between the polar component of the surface energy and its hemocompatibility. All in vitro characterizations, i.e. protein absorption behavior, activated partial thromboplastin time measurement and platelet adhesion behavior, showed improved hemocompatibility of the N
2-- or O
2-plasma-treated surfaces where the polar component of the surface energy was significantly increased. Si–O or Si–N surface bonds played an important role in improving hemocompatibility, as observed in a model experiment. These results support the importance of a negatively charged polar component of the surface in inhibiting fibrinogen adsorption and platelet adhesion.
This study targets dynamic behavior of interacting dislocations associated with PSB (Persistent Slip Bands) ladder structures, ultimately responsible for fatigue crack initiations, based on FTMP ...(Field Theory of Multiscale Plasticity), applied to simulation results by dislocation dynamics. Focus is place on the stable/unstable of the dislocation systems in terms of FTMP-based incompatibility tensor field in particular via the attendant phase-space trajectories (PhS-Ts). The stable responses are shown to be manifested as the limit-like loci on the PhS-Ts, whereas the unstable responses mainly due to cross slip-driven vacancy-type debris loop generations are specifically represented by the incompatibility rate, i.e., the quantity well correlate the frequency of the debris loop formations. The incompatibility rate, used here as the ordinate of the PhS-Ts, can be interpreted as the creation/annihilation rate of edge dislocation pairs, in the FTMP-based context, which corroborates the correlation result.
We have previously reported that fluorine-incorporated amorphous carbon (a-C:H:F) coating dramatically reduced the number and activation of adherent platelets in contact with human blood. In order to ...convert a-C:H:F coating into a commercial reality, it is necessary to estimate its life span and the sustainability of antithrombogenic properties using accelerated aging tests under various temperature conditions. The purpose of this study was to investigate the effect of different temperature conditions using accelerated aging tests on the antithrombogenic properties of a-C:H:F.
The a-C:H:F film was deposited on silicon substrates from a mixture of acetylene and octafluoropropane using the inductively coupled plasma enhanced chemical vapor deposition method. The a-C:H:F coated substrates were then stored at room temperature, 55°C, 70°C and 90°C, respectively. The surface chemical compositions of a-C:H:F film were examined using X-ray photoelectron spectroscopy (XPS). The antithrombogenic properties were evaluated through incubation with platelet-rich plasma isolated from human whole blood, and the properties of adhesion between film and metallic stents were evaluated by examining before-and-after balloon expansion. The XPS analysis showed that the relative amount of fluorine atoms slightly decreased and the amount of oxygen increased over time on the surface of a-C:H:F samples. Furthermore, the change in chemical composition was the most prominent in the samples stored at 90°C. However, no significant difference in the number of adherent platelets were observed among a-C:H:F coated sample surfaces after accelerated aging tests, suggesting that changes in chemical composition due to elapsed time and temperature changes do not significantly affect the antithrombogenic properties. Furthermore, the stability of the adhesive properties on a-C:H:F coated stents was revealed, because there were no cracks or instances of delamination on any a-C:H:F coated stent surfaces after expansion.
This work demonstrated that excellent antithrombogenic properties of a-C:H:F were maintained over time at each temperature, and thus a-C:H:F film could be utilized as a coating material for medical device commercialization.
We report that the antithrombogenic and adhesive properties of fluorine-incorporated amorphous carbon (a-C:H:F) are stable even after accelerated aging tests, and thus a-C:H:F film could be utilized as a coating material for medical device commercialization.
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•Fluorine concentration of a-C:H:F film decreased as a-C:H:F film was thermal aged.•Antithrombogenicity of a-C:H:F was maintained over time at any temperature.•Antithrombogenic a-C:H:F film could be utilized for device commercialization.
The goal of our study was to evaluate the diagnostic performance of percutaneous lung biopsy under CT-fluoroscopic guidance for ground-glass opacity (GGO) lesions.
85 percutaneous needle lung ...biopsies were performed in 73 patients. Specimens were obtained by core biopsy utilising an automated cutting needle and were evaluated histologically. Final diagnosis was confirmed by independent surgical pathology, independent culture results or clinical follow-up.
Rates of adequate specimens obtained and of precise diagnosis by needle biopsy were 92.9% (79/85) and 90.6% (77/85) of evaluated lung lesions, respectively. Precise diagnosis was achieved in 87.1% (27/31) of lesions ≤10 mm in diameter, 90.0% (36/40) of lesions >10 mm to ≤20 mm and 100.0% (14/14) of lesions >20 mm. Precision in diagnosing GGO lesions according to the GGO component was 73.9% (17/23) for pure GGO lesions and 96.8% (60/62) for part-solid GGO lesions. Obtaining a precise diagnosis did not differ significantly according to the lesion size (p=0.3840), but differences were significant according to the GGO component (p=0.0047). Malignancy was accurately diagnosed in 35 of 36 malignant lesions for which surgery was later performed. The specific cell type determined from specimens obtained by needle biopsy was exactly the same as the final histological diagnosis obtained after surgery in 20 lesions.
Tissue-core lung biopsy under CT-fluoroscopic guidance for a GGO lesion provides a high degree of diagnostic accuracy but is less reliable for determining the specific cell type.
Percutaneous lung biopsy under CT-fluoroscopic guidance for GGO is useful in differentiating malignancy.
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