Nano thick poly(ε-caprolactone)-poly(ethylene glycol) coatings developed by catalyst-free plasma assisted copolymerization process for biomedical applications

Poly(epsilon-caprolactone)-poly(ethylene glycol) (PCL-co-PEG) copolymers have great potential applications in the fields of nanotechnology, tissue engineering, pharmaceutics and medicinal chemistry. In the present work we have developed, for the first time, nanothick, amphiphilic and biodegradable PCL-co-PEG coatings by catalyst-free ROP of epsilon-caprolactone (epsilon-CL), in the presence of diethylene glycol dimethyl ether (DEGME) via a single-step soft plasma-polymerization process. A low-pressure inductively excited RF (13.56 MHz) discharge was used operating in the pulsed mode with argon as the carrier gas. Experiments were performed at different epsilon-CL : DEGME monomer feed ratios and effective plasma power. The resulting PCL-co-PEG coatings were characterized by FTIR-ATR, XPS and ellipsometry. The PCL-co-PEG coatings deposited at P-eff = 1 W exhibited an excellent stability against soaking in water. The chain propagation and molecular weight of copolymers were determined by H-1 NMR spectroscopy and MALDI ToF measurements. Human bone marrow endothelial cells (HBMEC), human ovarian carcinoma cells (NIH:OVCAR-3) and embryologic fibroblast (HF) were cultured in physiological conditions and were seeded in a microplate which was loaded with autoclaved coated glass cover slips for different time durations. The cell adhesion to the surface was determined by using an inverted microscope and SEM image analysis. The results showed that by gradually varying the epsilon-CL : DEGME partial pressure ratios of the monomers from 100 to 25%, the cell adhesion followed the same trend. The global objective of this work was to tailor the surface properties of PCL by copolymerizing it with PEG in the soft pulsed plasma environment to improve its applicability in tissue engineering and biomedical science.