Plasma polymerization for biomedical applications: A review

Plasma polymers have long been of interest as thin film coatings on biomedical devices and products, to generate desirable surface properties for favorable bio-interfacial interactions. Plasma polymers have also been used as platforms for the covalent immobilization of bioactive molecules. More recently, additional aspects have been investigated, such as selective prevention of adhesion of microbial pathogens, either via plasma polymers per se or including antimicrobial drugs. Plasma polymers have also been investigated for the release of silver ions and small organic molecules. Complementing low-pressure plasma approaches, processes at atmospheric pressure have attracted interest recently, including for nano/biocomposite coatings. This contribution reviews the use of plasma polymers for intended biomedical applications, with a focus on more recent topic areas

Novel bimetallic 1%M-Fe/Al2O3-Cr2O3 (2:1) (M = Ru, Au, Pt, Pd) catalysts for Fischer-Tropsch synthesis

The main objective of this work was to study the physicochemical and catalytic properties of bimetallic supported catalysts [1%M-Fe/Al2O3-Cr2O3 (2:1) (M = Ru, Au, Pt, Pd)] in Fischer-Tropsch synthesis. Furthermore, the study investigated the effect of noble metal addition to iron-supported catalysts on their physicochemical properties and reactivity. The physicochemical properties of the catalysts were studied using a range of characterization techniques such as X-ray diffraction (XRD), temperature-programmed reduction (TPR-H2), temperature-programmed desorption of ammonia (TPD-NH3) and BET (Brunauer – Emmett - Teller method). The activity tests were performed by Fischer-Tropsch synthesis in a high-pressure fixed-bed reactor using a gas mixture of H2 and CO with a molar ratio of 1:1. The correlation between the physicochemical properties of the investigated catalysts and their catalytic performance in CO hydrogenation was also investigated. The reactivity results showed that the most active system exhibited a high specific surface area, the highest total acidity and was the most reducible catalyst compared to the other catalysts tested. In addition, the Au–Fe system showed high selectivity towards liquid product formation during CO hydrogenation

Antibacterial Properties of Silver-Loaded Plasma Polymer Coatings

In a previous paper, we proposed new silver nanoparticles (SNPs) based antibacterial coatings able to protect eukaryotic cells from SNPs related toxic effects, while preserving antibacterial efficiency. A SNPs containing n-heptylamine (HA) polymer matrix was deposited by plasma polymerization and coated by a second HA layer. In this paper, we elucidate the antibacterial action of these new coatings. We demonstrated that SNPs-loaded material can be covered by thin HA polymer layer without losing the antibacterial activity to planktonic bacteria living in the near surroundings of the material. SNPs-containing materials also revealed antibacterial effect on adhered bacteria. Adhered bacteria number was significantly reduced compared to pure HA plasma polymer and the physiology of the bacteria was affected. The number of adhered bacteria directly decreased with thickness of the second HA layer. Surprisingly, the quantity of cultivable bacteria harvested by transfer to nutritive agar decreased not only with the presence of SNPs, but also in relation to the covering HA layer thickness, that is, oppositely to the increase in adhered bacteria number. Two hypotheses are proposed for this surprising result (stronger attachment or weaker vitality), which raises the question of the diverse potential ways of action of SNPs entrapped in a polymer matrix

Nanotopography mediated osteogenic differentiation of human dental pulp derived stem cells

Advanced medical devices, treatments and therapies demand an understanding of the role of interfacial properties on the cellular response. This is particularly important in the emerging fields of cell therapies and tissue regeneration. In this study, we evaluate the role of surface nanotopography on the fate of human dental pulp derived stem cells (hDPSC). These stem cells have attracted interest because of their capacity to differentiate to a range of useful lineages but are relatively easy to isolate. We generated and utilized density gradients of gold nanoparticles which allowed us to examine, on a single substrate, the influence of nanofeature density and size on stem cell behavior. We found that hDPSC adhered in greater numbers and proliferated faster on the sections of the gradients with higher density of nanotopography features. Furthermore, greater surface nanotopography density directed the differentiation of hDPSC to osteogenic lineages. This study demonstrates that carefully tuned surface nanotopography can be used to manipulate and guide the proliferation and differentiation of these cells. The outcomes of this study can be important in the rational design of culture substrates and vehicles for cell therapies, tissue engineering constructs and the next generation of biomedical devices where control over the growth of different tissues is required

Polymeric Nanosuspensions for Enhanced Dissolution of Water Insoluble Drugs

The aim of the present research is to formulate and evaluate polymeric nanosuspensions containing three model water insoluble drugs, nifedipine (NIF), carbamazepine (CBZ), and ibuprofen (IBU) with various physicochemical properties. The nanosuspensions were prepared from hydroxypropyl methylcellulose (HPMC) and polyvinylpyrrolidone (PVP) by a cosolvent technique with polyethylene glycol (PEG-300) and water as the cosolvents. Physicochemical and morphological characteristics of the nanosuspensions (particle size, polydispersity index, and crystallinity) have been correlated with the drug release behaviour. The effects of polymer, drug ratio on the physical, morphological, and dissolution characteristics of the drugs are reported. Drug release is significantly enhanced from the nanosuspensions; for example, the maximum NIF, IBU, and CBZ concentrations after 8-hour dissolution are increased approximately 37, 2, and 1.2 times, respectively, in comparison with the pure powdered drugs. Based on this solubilization enhancement performance, the nanosuspensions have potential for increasing the orally dosed bioavailability of NIF, IBU, and CBZ

Plasma Polymer Coatings To Direct the Differentiation of Mouse Kidney-Derived Stem Cells into Podocyte and Proximal Tubule-like Cells

Kidney disease is now recognised as a global health problem and is associated with increased morbidity and mortality, along with high economic costs. To develop new treatments for ameliorating kidney injury and preventing disease progression, there is a need for appropriate renal culture systems for screening novel drugs and investigating the cellular mechanisms underlying renal pathogenesis. There is a need for in vitro culture systems that promote the growth and differentiation of specialised renal cell types. In this work, we have used plasma polymerisation technology to generate gradients of chemical functional groups to explore whether specific concentrations of these functional groups can direct the differentiation of mouse kidney-derived stem cells into specialised renal cell types. We found that amine-rich (-NH2) allylamine-based plasma polymerised coatings could promote differentiation into podocyte-like cells, whereas methyl-rich (CH3) 1,7-octadiene-based coatings promoted differentiation into proximal tubule-like cell (PTC). Importantly, the PT-like cells generated on the substrates expressed the marker megalin and were able to endocytose albumin, indicating that the cells were functional

Plasma polymers from oregano secondary metabolites: Antibacterial and biocompatible plant-based polymers

Bacterial infection of chronic wounds is a major healthcare problem that affects the quality of life of millions of patients worldwide and leads to a substantial healthcare cost burden. This project focused on the manufacture of a potential wound healing agent. Plasma polymers from oregano secondary metabolites (PP-OSMs) were fabricated by radiofrequency plasma-enhanced chemical vapor deposition (RF-PECVD) in continuous and pulse plasma modes at room temperature. The surface, biocompatibility, and antibacterial properties of the PP-OSMs were investigated. Polymers fabricated by RF-PECVD retained the functional groups of OSMs, promoted human dermal fibroblast adhesion, inhibited Staphylococcus aureus attachment, and eliminated Pseudomonas aeruginosa. The PP-OSM coatings are potential candidates for use in medical applications where cell biocompatibility and antibacterial properties are required