Literatura científica selecionada sobre o tema "Plasma activation grafting"

The present study utilized the capability of ambient-temperature plasma in modifying the surface properties of materials to activate the polyethylene terephthalate (PET) fiber surfaces. The effects of different plasma treatment parameters (such as plasma power, treatment time) and grafting parameters (such as grafting temperature, acrylic acid monomer concentration, grafting time) on the activation and grafting of the PET fibers were studied. The feasibility of applying ambient-temperature plasma combined with grafting technology for the preparation of ion exchangers in the heavy metal containing wastewater treatment was evaluated.

Abstract An active screen plasma system (ASPS) was used for the surface activation of poly(lactic acid) (PLA) as a pretreatment before the oxidative graft polymerization of polyaniline (PANI). In ASPS, the plasma glow discharge occurs outside the grid, and the samples to be treated are placed inside the cage where they are subjected to a floating potential (about −12 V). An increase in hydrophilicity was observed for all samples after Ar plasma treatment. In addition, a decrease in thermal stability and changes in crystallization behavior were observed for PLA samples treated for a longer time. After PANI graft polymerization, smoothing of the surface topography was noticed in samples treated for short time periods. Such a change in the topography, in addition to surface activation, provides better conditions for subsequent PANI grafting.

Reverse osmosis (RO) membranes represent a strategic tool for the development of desalination and water treatment processes. Today’s global needs for clean water supplies show stressing circumstances to secure this supply, relying upon desalination and wastewater treatment and reuse, especially in Egypt and the Middle East. However, chlorine attack and fouling of polyamide layers, the active (selective) layers of RO membranes, are representing a great obstacle to seriously spreading the use of this technology. One promising way of fouling control and chlorine resistance is surface modification using grafting by plasma or vacuum ultraviolet (VUV) irradiation as a layer-by-layer assembly on polyamide membranes. Several studies have shown the effect of grafting by plasma using methacrylic acid (atmospheric pressure plasma) and showed that grafted coatings can improve PA membranes toward permeation compared with commercial ones with fouling behavior but not chlorine resistance. In this work, the techniques of layer-by-layer (LBL) assembly for previously prepared PA RO membranes (3T) using a mixed-base polymer of polysulfone and polyacrylonitrile in the presence of nanographene oxide (GO) without chemical grafting and with chemically grafted poly-methacrylic acid (3TG) were used. Membranes 3T, 3TG, a blank one (a base polymer membrane only was surface modified using VUV activation (AKT), and one with a grafted layer with polyethylene glycol (VUV-PEG) were prepared. These were then compared with polydimethylsiloxane (VUV-PDMS) and another surface modification with low-pressure plasma using acrylic acid (acryl) and hexadimethyl siloxane (GrowPLAS). The tested membranes were evaluated by short-term permeation and salt rejection experiments together with fouling behavior and chlorine resistance. A clear improvement of chlorine resistance and antifouling was observed for 3T membranes under plasma treatment, especially with the grafting with polyacrylic acid. Better antifouling and antichlorine behaviors were achieved with the vacuum UV treatment.

Background. This prospective randomized study compared the inflammatory response in patients undergoing elective on-pump and off-pump coronary artery bypass grafting. Patients and methods. Forty-four patients undergoing elective coronary artery bypass grafting were recruited with 22 patients randomized to on-pump heart surgery and 22 patients to off-pump coronary bypass surgery. Plasma levels of C3bc, the terminal SC5b-9 complement complex, myeloperoxidase, β -thromboglobulin and prothrombin fragment F1 + 2 were measured before the operation, intraoperatively, at termination of the operation, and two hours post-operatively. Results. Complement was markedly activated in the on-pump group as indicated by a significant increase in C3bc and SC5b-9 (p < 0.001 for both), whereas no complement activation was seen in the off-pump group (p = 0.001 between the groups). In contrast, both groups showed significant activation of neutrophils, platelets and coagulation, as indicated by an early increase in myeloperoxidase and a post-operative increase in β-thromboglobulin and F1 + 2, respectively. Notably, there were no inter-group differences with regard to neutrophil and platelet activation, whereas coagulation activation was more pronounced in the off-pump group (p < 0.01). Conclusions. Off-pump surgery completely eliminated the heart-lung machine-induced complement activation. Neutrophils and platelets were equally activated in both groups, whereas coagulation was enhanced post-operatively in the off-pump group. Perfusion (2007) 22, 251—256.

The aim. To evaluate the clinical outcomes and features of the state of the platelet-plasma and vascular hemostasis in patients (pts) with unstable angina and coronary artery bypass grafting (CABG) on-pump and off-pump for the correction of antithrombotic therapy and reduce the number of postoperative cardiovascular events. Material and methods. The study included 146 pts with unstable angina (UA) with a surgical treatment strategy. CG amounted to 106 pts with CABG and a standard approach to drug maintenance. MG comprised 40 pts with CABG and a personalized approach to antithrombotic therapy. Results. In CABG off-pump in pts with UA, an increased in platelet aggregation and activation of platelet hemostasis occurs on the 2nd day of the postoperative period, in CABG on-pump on the 5-7th day. Activation of plasma hemostasis had laboratory manifestations on the 5-7th day of the postoperative period, and is most pronounced in CABG on-pump, compared with CABG off-pump. After 1 month of control, 38,7% pts with UA and CABG were characterized by the presence of high residual platelet reactivity against the background of standard antiplatelet treatment, of which 23,6% retained activation of plasma hemostasis, which is manifested in excess of the normal level of D-dimers, as well as an increased in peak thrombin concentration and endogenous thrombin potential. Patients with UA and CABG who underwent correction of antithrombotic therapy differed from patients with a standard approach to treatment with a significantly lower number of repeated cardiovascular events over 2 years of follow-up (5% versus 22.6%).

Donor–acceptor Stenhouse adducts (DASAs) are gaining attention from organic and material chemists due to their visible light-stimulated photochromic properties. In this report, we present a facile method for grafting coloured triene on polycarbonate surface, without involving any pre-treatments like plasma activation, etc. The chemoselectivity of carbonate with a primary amine and Meldrum's activated furan (MAF) with polymer bound secondary amine has been exploited to graft photoswitchable DASA on the polymer surface. Primary, secondary and tertiary amine-functionalized polycarbonate surfaces have been prepared to evaluate the reactivity of amine with MAF.

This paper provides a comprehensive overview of nanofibrous structures for tissue engineering purposes and the role of non-thermal plasma technology (NTP) within this field. Special attention is first given to nanofiber fabrication strategies, including thermally-induced phase separation, molecular self-assembly, and electrospinning, highlighting their strengths, weaknesses, and potentials. The review then continues to discuss the biodegradable polyesters typically employed for nanofiber fabrication, while the primary focus lies on their applicability and limitations. From thereon, the reader is introduced to the concept of NTP and its application in plasma-assisted surface modification of nanofibrous scaffolds. The final part of the review discusses the available literature on NTP-modified nanofibers looking at the impact of plasma activation and polymerization treatments on nanofiber wettability, surface chemistry, cell adhesion/proliferation and protein grafting. As such, this review provides a complete introduction into NTP-modified nanofibers, while aiming to address the current unexplored potentials left within the field.

SummaryAprotinin reduces blood loss following cardiopulmonary bypass operations (CPB) by the prevention of hyperfibrinolysis. Its influence on circulating platelets is uncertain. In this prospective trial we investigated activation, adhesion, and aggregation receptors on the platelet surface in 20 patients who underwent elective coronary artery bypass grafting. These patients were randomly assigned to receive either a high dose of aprotinin or placebo. Flow cytometry was performed to determine platelet activation [P-selectin, glycoprotein (GP) 53], adhesive (GP Ib), and aggregatory (GP IIb-IIIa) receptors on circulating platelets, before, during, and after CPB. Aprotinin had neither a significant effect on platelet activation nor on adhesive and aggregatory receptors. Plasma levels of D-dimers were measured before and after CPB to assess fibrinolytic activity. D-dimers following CPB and chest tube drainage were significantly less in the aprotinin group. We conclude that aprotinin reduces blood loss by its effect on fibrinolysis but has no direct influence on platelet function.

Les huiles essentielles sont des candidates biosourcées potentielles pour être greffées sur des surfaces polymères afin de lutter contre les infections bactériennes, soit en restreignant la croissance des bactéries (effet bactériostatique), soit en tuant les cellules bactériennes (effet bactéricide). Cette thèse porte sur la modification de molécules terpénoïdes destinées à être greffées sur des surfaces polymères activées. Nous visons à greffer des molécules d’huiles essentielles modifiées sur des surfaces polymères par des liaisons covalentes fortes, facilitées par la technologie de traitement au plasma. Le citronellol (CT) et le géraniol (GR) ont été choisis pour leur activité antimicrobienne et ont été modifiés avec succès afin d’obtenir une meilleure réactivité pour la greffe sur polymère. Ils ont été transformés en CT-oxyde et GR-oxyde grâce à une méthode d’oxydation chimio-enzymatique accessible et respectueuse de l’environnement. Des tests microbiologiques ont été réalisés pour évaluer les effets antibactériens de CT et GR avant et après modification. Trois espèces bactériennes ont été utilisées: Escherichia coli, Staphylococcus aureus et Corynebacterium glutamicum. Les résultats ont montré que les effets antibactériens subsistaient après l’époxydation; les molécules testées ont démontré des activités antibactériennes en ciblant les enveloppes cellulaires bactériennes, en perturbant l’intégrité des membranes et en modifiant l’hydrophobicité. Ces actions ont conduit à l’inhibition de la croissance bactérienne ou à la mort des bactéries, comme l’ont révélé les mesures de potentiel Zeta, les images obtenues par microscopie électronique à balayage et les évaluations de l’énergie de surface. Notre étude a conclu à l’efficacité antibactérienne des CT-ox et GR-ox contre les trois souches bactériennes. En outre, ces molécules terpénoïdes modifiées présentent un potentiel de greffe sur des surfaces polymères, conférant ainsi aux polymères des propriétés antimicrobiennes
Essential oils are potential biosourced candidates to be grafted on polymer surfaces to fight against bacterial infections by either restricting the growth of bacteria (bacteriostatic effect) or killing bacterial cells (bactericidal effect). This thesis deals with the modification of terpenoid molecules intended to be grafted on polymer-activated surfaces. We eager to graft modified EO molecules onto polymer surface through strong covalent bonding, facilitated by plasma treatment technology. Citronellol (CT) and geraniol (GR) were chosen for their antimicrobial activity and were successfully modified to obtain better reactive function towards polymer grafting. They were transformed into CT-oxide and GR-oxide through an accessible and green chemo enzymatic oxidation method. Microbiological tests were undertaken to estimate the antibacterial effects of CT and GR before and after modification. Three bacterial species have been used: Escherichia coli, Staphylococcus aureus and Corynebacterium glutamicum. The results showed that antibacterial effects remained after epoxidation, tested molecules exhibited antibacterial activities by targeting bacterial cell envelopes, disrupting membrane integrity, and altering hydrophobicity. These actions led to the inhibition of bacterial growth or death of the bacteria, as evidenced by Zeta Potential measurements, Scanning Electron Microscopy imaging, and surface energy assessments. Our study conclusively confirmed the antibacterial effectiveness of CT-ox and GR-ox against three bacterial strains. Furthermore, those modified terpenoid molecules have potential to graft on the polymer surface and provide polymer antimicrobial property