Surface wettability plays an important role in determining the function of a wound dressing. Dressings with hydrophobic surfaces are suitable for bacterial adsorption, however, a hydrophilic surface is needed to improve cell attachment for most anchorage-dependent cell types. Furthermore, the hydrophobicity/hydrophilicity of the surface can be used to direct cellular processes such as cell initial attachment, adhesion, and migration during wound healing. Thus, a surface with an ability to switch their surface wettability improves the practicality of the dressing. In this study, we propose a temporary surface wettability tuning for surface patterning utilizing plasma treatment. Polycaprolactone (PCL) and polydimethylsiloxane (PDMS) surfaces were treated with tetrafluoromethane (CF4), sulphur hexafluoride (SF6), and oxygen (O2) plasma, and the effects on the surface wettability, roughness, and chemical composition were investigated. Based on the contact angle measurement, CF4 plasma altered surface wettability of PCL and PDMS films to hydrophobic and hydrophilic, respectively. After CF4 treatment, better attachment of the primary mouse embryonic fibroblast cell (3T3) was observed on the treated PDMS surface. Embedding PCL into PDMS generated a hydrophobic-hydrophilic pattern mixture surface, which offers great potential in the tissue engineering field such as cell patterning and guidance.
2. Biomedical applications of plasma technology
Atmospheric plasma is widely used for medical and biological applications including sterilization, selective killing of tumor cells, gene transfection, and healing wounds.
Acidic and radical species generated by plasma first access a plasma membrane, the outermost layer of a cell. However, it is unclear how these plasma-induced species affect and/or permeate plasma membranes.
A phospholipid bilayer membrane was prepared on a silicon wafer in an aqueous solution, and the atmospheric plasma was irradiated with a dielectric barrier discharge (DBD) instrument.
Observation with a fluorescence microscope and an atomic force microscope revealed that pores on the order of 10 nm to 1 µm in size were formed in the lipid bilayer membrane after the plasma irradiation. Capturing these micropores in a fluid lipid membrane is a significant advantage of the artificial lipid membrane system, and quantitative analysis of the pores was achieved. The results indicate that the micropores act as paths for the non-selective leakage or transportation of solutes into and out of cells during the plasma-induced phenomenon such as sterilization and gene transfection.
The artificial plasma membrane system is valuable for studying the fundamental effects of plasma on biomolecules for establishing medical and biological applications of plasmas.