Plasma treatment of polystyrene (PS) culture dishes enhances cell adhesion

Cell culture is the most core and fundamental technology in biotechnology; A culture dish is a laboratory vessel used for culturing microorganisms or cells. Currently, disposable plastic culture dishes are widely used in many fields such as biology, medicine, and chemical engineering. Plastic products have become the preferred polymer materials for experimental analysis in industries such as biology and medicine due to their low price.

The current disposable plastic culture dishes, such as polystyrene (PS), have many advantages, such as high transparency, excellent rigidity, low cost, non toxicity, good resistance to solvents and electrical insulation, excellent surface glossiness, and good processability. However, when polystyrene is applied in fields such as biomedicine, due to its hydrophobic surface, it cannot fully meet the biocompatibility and high biological functional requirements required as a biomedical material, making it very difficult to use for adherent culture of bacteria and cells. Usually, surface treatment is required before use to improve the hydrophilicity, hydrophobicity, and biocompatibility of the material surface, in order to broaden the application range of polystyrene materials. The hydrophilicity and hydrophobicity of polystyrene surface can affect the adhesion and binding of polymers to molecules in contact with its surface.

To address these issues, low-temperature plasma surface modification technology has been widely applied in biomedical materials due to its unique advantages.

PS culture dish plasma treatment

Plasma contains a large number of high-energy particles, such as electrons, ions, free radicals, and some neutral substances. Although these active particles have a short lifespan, they are very active and can easily undergo chemical reactions with other substances in the system. Therefore, plasma can be used for surface treatment of materials. The energy of active particles in low-temperature cold plasma is sufficient to break the chemical bonds of molecules, but it does not cause the material surface to overheat, and is still applicable to some high-temperature unstable polymers. In addition, plasma treatment of material surfaces only affects depths of a few nanometers below the surface, without damaging the internal structure of the material or altering its optical properties. Secondly, plasma treatment does not produce toxic chemicals, making the plasma surface treatment process safe, reliable, non-toxic, and environmentally friendly.

Comparison of droplet angles before and after PS oxygen plasma treatment

Figure 1 Comparison of droplet angles before and after plasma treatment of polystyrene

From Figure 1, it can be seen that the contact angle of PS culture dishes without plasma treatment is very large. After plasma treatment, the droplet angle becomes very small, and the PS surface reaches a superhydrophilic state.

For polystyrene (PS), its chemical structure includes a benzene ring, which is usually not biocompatible due to its lack of natural expression in the human body. Oxygen plasma can effectively destroy these benzene rings and replace them with oxygen-containing groups such as hydroxyl and carbonyl groups (Figure 2).

Figure 2 Plasma oxidation of polystyrene

After plasma treatment, the surface energy of polystyrene (PS) culture dishes will increase, the surface morphology will become rough, and the chemical composition will also change. The surface will introduce oxygen-containing functional groups such as hydroxyl OH and carboxyl COOH, which can significantly improve the hydrophilicity and biocompatibility of the material, thereby increasing the adhesion of cells or proteins to the polymer surface.