Low-temperature plasma treatment-assisted layer-by-layer self-assembly for the modification of nanofibrous mats

To expand the template options of immersive electrostatic layer-by-layer self-assembly (LBL), which requires hydrophilic and protonation substrates, an environmentally friendly and simple plasma pretreatment that enhances the surface charge and wettability of superhydrophobic mats is employed to effectively assist LBL. With positively and negatively charged layers, chitosan (CS) and bovine serum albumin (BSA) were alternately deposited on the surface of polystyrene (PS) mats and oxygen (O₂) plasma-treated mats via electrostatic LBL. After the exposure of plasma gas at different time intervals, the ζ-potential values of the mats were distinct, and the value of the mats was -30.1 mV after treatment via O₂ plasma for 70 s, which was approximately 5 times higher than that of the pristine PS mats. In addition, the average surface roughness (Ra) of the O₂ plasma treated mats was 116.1 ± 12.6 nm, which was higher than that of the PS mats (87.6 ± 14.3 nm), due to the plasma etching. The water contact angle of the PS mats was 144.5 ± 1.4°, which decreased to 0° within 0.33 s after O₂ plasma treatment, proving that the modified PS mats were superhydrophilic. Compared with the mats without plasma treatment, the uniform deposition of CS and BSA on O₂ plasma-treated mats was confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Moreover, the mats with an enhanced surface charge and wettability after plasma treatment and LBL processing also exhibited low cell cytotoxicity and facilitated cell growth well.