Plasma polymer surfaces for cell expansion and delivery

The purpose of this review is to explore the development, applications and outcomes of using plasmadeposited (polymeric) surfaces as culture and delivery vehicles for cells in the replacement, repair and regeneration of damaged tissues. After a brief introduction to biomaterials and cell therapy, examples of the use of plasma polymerization in surface engineering are presented. The use of these surfaces for both in vitro cell culture and ex vivo delivery is reviewed with a particular emphasis on the epithelium. The review concludes with a look at some of the emerging and potential future directions for this technology in mediating cell-surface interactions.

Generation of reactive oxygen species from porous silicon microparticles in cell culture medium

Nanostructured (porous) silicon is a promising biodegradable biomaterial, which is being intensively researched as a tissue engineering scaffold and drug-delivery vehicle. Here, we tested the biocompatibility of non-treated and thermally-oxidized porous silicon particles using an indirect cell viability assay. Initial direct cell culture on porous silicon determined that human lens epithelial cells only poorly adhered to non-treated porous silicon. Using an indirect cell culture assay, we found that non-treated microparticles caused complete cell death, indicating that these particles generated a toxic product in cell culture medium. In contrast, thermally-oxidized microparticles did not reduce cell viability significantly. We found evidence for the generation of reactive oxygen species (ROS) by means of the fluorescent probe 2′,7′-dichlorofluorescin. Our results suggest that non-treated porous silicon microparticles produced ROS, which interacted with the components of the cell culture medium, leading to the formation of cytotoxic species. Oxidation of porous silicon microparticles not only mitigated, but also abolished the toxic effects. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2010

Nanopore gradients on porous aluminum oxide generated by nonuniform anodization of aluminum

A method for surface engineering of structural gradients with nanopore topography using the self-ordering process based on electrochemical anodization of aluminum is described. A distinct anodization condition with an asymmetrically distributed electric field at the electrolyte/aluminum interface is created by nonparallel arrangement between electrodes (tilted by 45°) in an electrochemical cell. The anodic aluminum oxide (AAO) porous surfaces with ordered nanopore structures with gradual and continuous change of pore diameters from 80 to 300 nm across an area of 0.5-1 cm were fabricated by this anodization using two common electrolytes, oxalic acid (0.3 M) and phosphoric acid (0.3 M). The formation of pore gradients of AAO is explained by asymmetric and gradual distribution of the current density and temperature variation generated on the surface of Al during the anodization process. Optical and wetting gradients of prepared pore structures were confirmed by reflective interferometric spectroscopy and contact angle measurements showing the ability of this method to generate porous surfaces with multifunctional gradients (structural, optical, wetting). The study of influence of pore structures on cell growth using the culture of neuroblastoma cells reveals biological relevance of nanopore gradients and the potential to be applied as the platform for spatially controllable cell growth and cell differentiation.

Surface hydrophilic modification of RO membranes by plasma polymerization for low organic fouling

Triethylene glycol dimethyl ether (triglyme), a polyethylene glycol (PEG)-like hydrophilic polymer, was deposited by plasma polymerization to reduce RO membrane's organic fouling tendency. This method has the great advantage of achieving modification in one single step. A series of plasma deposition experiments were undertaken. The successful coating of the polymer was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. Water contact angle measurements and permeation experiments using a protein solution were conducted to evaluate the change of hydrophilicity and anti-fouling properties. Salt rejection tests were performed to evaluate membrane performance. A reduction in contact angles from 32° to 7° was achieved for the treated membranes, indicating enhanced hydrophilicity. The permeation experiments revealed that the modified membranes achieved an excellent maintenance of flux compared to the untreated membranes. Specifically, after 210 min of filtration, no flux decline was found for the modified membranes, while a 27% reduction of the initial flux was observed for the untreated membrane. Flux recovery after cleaning by water only was up to 99.5% for the modified membranes, while for the untreated it was only 91.0%. The surface hydrophilic modification of RO membranes by plasma polymerization has shown a clear improvement in membrane anti-fouling performance.

Surface protein gradients generated in sealed microchannels using spatially varying helium microplasma

Spatially varied surface treatment of a fluorescently labeled Bovine Serum Albumin (BSA) protein, on the walls of a closed (sealed) microchannel is achieved via a well-defined gradient in plasma intensity. The microchips comprised a microchannel positioned in-between two microelectrodes (embedded in the chip) with a variable electrode separation along the length of the channel. The channel and electrodes were 50 μm and 100 μm wide, respectively, 50 μm deep, and adjacent to the channel for a length of 18 mm. The electrode separation distance was varied linearly from 50 μm at one end of the channel to a maximum distance of 150, 300, 500, or 1000 μm to generate a gradient in helium plasma intensity. Plasma ignition was achieved at a helium flow rate of 2.5 ml/min, 8.5 kVpk-pk, and 10 kHz. It is shown that the plasma intensity decreases with increasing electrode separation and is directly related to the residual amount of BSA left after the treatment. The plasma intensity and surface protein gradient, for the different electrode gradients studied, collapse onto master curves when plotted against electrode separation. This precise spatial control is expected to enable the surface protein gradient to be tuned for a range of applications, including high-throughput screening and cell-biomolecule-biomaterial interactions

Retrospective Study of Reported Adverse Events Due to Complementary Health Products in Singapore From 2010 to 2016

The objective of this study is to collate and analyse adverse event reports associated with the use of complementary health products (CHP) submitted to the Health Sciences Authority (HSA) of Singapore for the period 2010–2016 to identify various trends and signals for pharmacovigilance purposes. A total of 147,215 adverse event reports suspected to be associated with pharmaceutical products and CHP were received by HSA between 2010 and 2016. Of these, 143,191 (97.3%) were associated with chemical drugs, 1,807 (1.2%) with vaccines, 1,324 (0.9%) with biological drugs (biologics), and 893 (0.6%) with CHP. The number of adverse event reports associated with Chinese Proprietary Medicine, other complementary medicine and health supplements are presented. Eight hundred and ninety three adverse event reports associated with CHP in the 7-year period have been successfully collated and analyzed. In agreement with other studies, adverse events related to the “skin and appendages disorders” were the most commonly reported. Most of the cases involved dermal allergies (e.g., rashes) associated with the use of glucosamine products and most of the adulterated products were associated with the illegal addition of undeclared drugs for pain relief. Dexamethasone, chlorpheniramine, and piroxicam were the most common adulterants detected. Reporting suspected adverse events is strongly encouraged even if the causality is not confirmed because any signs of clustering will allow rapid regulatory actions to be taken. The findings from this study help to create greater awareness on the health risks, albeit low, when consuming CHP and dispelling the common misconception that “natural” means “safe.” In particular, healthcare professionals and the general public should be aware of potential adulteration of CHP. The analysis of spontaneously reported adverse events is an important surveillance system in monitoring the safety of CHP and helps in the understanding of the risk associated with the use of such products. Greater collaboration and communication between healthcare professionals, regulators, patients, manufacturers, researchers, and the general public are important to ensure the quality and safety of CHP