Two-dimensional amine-functionality gradient by plasma polymerization

• Two-dimensional gradients with wide range by two-step allylamine plasma polymerization.
• A correlation was developed to elucidate nitrogen concentration distribution.
• Investigation of the cell responses toward the distribution of nitrogen content.
• Initial stage of plasma polymerization governs the formation of the gradient.
• Flexible methodology in fabricating high throughput 2D gradient for various types of polymer.

A two-dimensional (2D) gradient was created by employing two-step diffusion-controlled plasma polymerization of allylamine on polypropylene membrane, with varied deposition durations composed of two stages. The wettability gradient was examined by water contact angle measurements which clearly demonstrated that the gradient was well manipulated by varying the treatment duration, thus controlled the surface coverage and resulted in the average water contact angle ranged from 110° to 25°. On the created 2D gradients, the cell responses toward the distribution of nitrogen content were imaged by confocal laser microscopy. Moreover, a correlation based on experimental data revealed a linear relationship between the nitrogen content and water contact angle. The addition of serum proteins assisted also the adhesion and growth of L-929 cells. The methodology in fabricating the 2D gradient demonstrated the flexibility of the plasma technique which can be further used to create different types of well-defined gradients for applications in surface functionalization, biomedical devices, and material screening.

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