This tribute to Dr. Ulrich (“Uli”) Kogelschatz is timed to coincide with the 20th anniversary of an article by him in this journal, the review paper that has become a “must read” in the field of ...non-thermal atmospheric pressure plasmas. This author reminisces about how personal and professional contacts with Uli have impacted his own research to this day, done by outlining a few selected examples.
Low‐pressure plasma co‐polymerisation of binary gas mixtures of ethylene and ammonia was investigated in order to deposit N‐rich plasma polymer coatings for biomedical applications. Deposition ...kinetics and relevant surface characteristics were investigated as a function of r.f. power, gas pressure, and NH3/C2H4 ratio. Physico‐chemical properties of the coatings were determined by surface‐sensitive techniques: for example, total nitrogen concentrations up to 40 at.‐% were measured by XPS, while those of primary amines were determined by chemical derivatisation followed by XPS analysis. L‐PPE:N films were further characterised by UV‐vis and IR spectroscopic ellipsometry and by CAG.
We report on a methodology for measuring the energy dissipated per AC high voltage cycle in a cold atmospheric pressure plasma jet (CAPJet). This method is adapted from research by Nisol et al. on ...plasma polymerization of hexamethyldisiloxane (HMDSO) organosilicon vapor in a large area planar dielectric barrier discharge (DBD) reactor. Here too, we measured ΔEg, the energy difference with and without small HMDSO vapor concentrations in the argon carrier gas flow. From ΔEg we then derived Em, the energy per molecule, and compared values with those of Nisol. Good agreements were found, including in film structures determined from attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectra, thus suggesting that realistic Em values can be successfully obtained also for the CAPJet case.
Methodology for determining Eg, the energy dissipated per cycle of applied AC high voltage, Va(f), has successfully been extended from planar atmospheric pressure (AP) dielectric barrier discharge (DBD) geometry to a Cold AP plasma jet (CAPJet). Subsequent evaluations of ΔEg and Em, the energy per reagent molecule in Ar carrier gas flow, also agree with Nisol et al.'s published results for hexamethyldisiloxane (HMDSO), as do attenuated total reflectance (ATR) Fourier‐transform infrared (FTIR) spectra of PP‐HMDSO thin film deposits.
Low-temperature plasma science and technology has made enormous strides during the past half-century. To a significant extent, the driver has been integrated circuit (IC) processing, because without ...plasma-based etching and deposition techniques, the progression of Moore’s law would have ceased its course long ago. Scientific and technological advances no less spectacular than those in the IC sector, and of comparable economic impact, have occurred in the area of
plasmas and polymers
, where a third process type, surface modification, can be added to those, etching—or ablation, and deposition, mentioned above. In this article, we start by listing a number of particular features associated with the exposure of polymers to low-temperature plasmas, for example the liberation of volatile molecular fragments from the surface due to bond scissions, the accompanying creation of free radicals, cross-linking and grafting reactions induced by this and by vacuum-ultraviolet photon irradiation from excited species in the plasma, etc. All these aspects are of far lesser impact, if any at all, when the same plasmas are in contact with inorganic surfaces. We then list some high-volume industrial processes and operational details drawn from diverse economic sectors. These are accompanied by detailed example-cases from our own laboratories, based on both low- and atmospheric-pressure low-temperature plasma processes.
Bone is a frequent site of tumor metastasis. The bone-tumor microenvironment is heterogeneous and complex in nature. Such complexity is compounded by relations between metastatic and bone cells ...influencing their sensitivity/resistance to chemotherapeutics. Standard chemotherapeutics may not show efficacy for every patient, and new therapeutics are slow to emerge, owing to the limitations of existing 2D/3D models. We previously developed a 3D interface model for personalized therapeutic screening, consisting of an electrospun poly lactic acid mesh activated with plasma species and seeded with stromal cells. Tumor cells embedded in an alginate-gelatin hydrogel are overlaid to create a physiologic 3D interface. Here, we applied our 3D model as a migration assay tool to verify the migratory behavior of different patient-derived bone metastasized cells. We assessed the impact of two different chemotherapeutics, Doxorubicin and Cisplatin, on migration of patient cells and their immortalized cell line counterparts. We observed different migratory behaviors and cellular metabolic activities blocked with both Doxorubicin and Cisplatin treatment; however, higher efficiency or lower IC50 was observed with Doxorubicin. Gene expression analysis of MDA-MB231 that migrated through our 3D hybrid model verified epithelial-mesenchymal transition through increased expression of mesenchymal markers involved in the metastasis process. Our findings indicate that we can model tumor migration in vivo, in line with different cell characteristics and it may be a suitable drug screening tool for personalized medicine approaches in metastatic cancer treatment.
The method we have developed for understanding energetic exchanges between precursor molecules and argon (Ar) carrier gas in a dielectric barrier discharge (DBD) has much‐proven merit. The present ...article focuses on hydrofluoromethanes, CHxFy. The precursors (‰ concentrations) were mixed with Ar in a 20 kHz, 8 kV (peak‐to‐peak) DBD. For each compound, Em, the energy absorbed per molecule, was plotted as a function of precursor flow rate. Besides the determination of Em, we have used optical emission spectroscopy as a diagnostic of the plasma physicochemistry. The influence of chemical structure has been investigated by depositing thin plasma polymer coatings; we have measured their deposition rates and water contact angles, which have been correlated with Em values and X‐ray photoelectron spectroscopy measurements.
Dielectric barrier discharge experiments at atmospheric pressure with an argon carrier gas and five hydrofluoromethane molecules, CHxFy (0 ≤ x ≤ 4; y = 4 – x) have been used to measure the energy absorbed from the plasma by each molecule. The influence of H/F ratio has been examined with respect to optical emission spectroscopy, plasma polymer (PP) film growth, and properties (X‐ray photoelectron spectroscopy‐derived composition, water contact angle) of resulting PP coatings.
Metastatic cancers can be highly heterogeneous, show large patient variability and are typically hard to treat due to chemoresistance. Personalized therapies are therefore needed to suppress tumor ...growth and enhance patient's quality of life. Identifying appropriate patient-specific therapies remains a challenge though, due mainly to non-physiological in vitro culture systems. Therefore, more complex and physiological in vitro human cancer microenvironment tools could drastically aid in development of new therapies. We developed a plasma-modified, electro-spun 3D scaffold (PP-3D-S) that can mimic the human cancer microenvironment for customized-cancer therapeutic screening. The PP-3D-S was characterized for optimal plasma-modifying treatment and scaffolds morphology including fiber diameter and pore size. PP-3D-S was then seeded with human fibroblasts to mimic a stromal tissue layer; cell adhesion on plasma-modified poly (lactic acid), PLA, electrospun mats vastly exceeded that on untreated controls. The cell-seeded scaffolds were then overlaid with alginate/gelatin-based hydrogel embedded with MDA-MB231 human breast cancer cells, representing a tumor-tissue interface. Among three different plasma treatments, we found that NH
plasma promoted the most tumor cell migration to the scaffold surfaces after 7 days of culture. For all treated and non-treated mats, we observed a significant difference in tumor cell migration between small-sized and either medium- or large-sized scaffolds. In addition, we found that the PP-3D-S was highly comparable to the standard Matrigel® migration assays in two different sets of doxorubicin screening experiments, where 75% reduction in migration was achieved with 0.5 μM doxorubicin for both systems. Taken together, our data indicate that PP-3D-S is an effective, low-cost, and easy-to-use alternate 3D tumor migration model which may be suitable as a physiological drug screening tool for personalized medicine against metastatic cancers.
PDF
