Coating bio-nanofilm on PDMS through layer-by-layer self-assembly

PDMS is a popular biomaterial, and its surface modification with biocompatible ultrathin films may have potential applications in many biomedical areas. The technique of electrostatic Layer-by-Layer (LbL) assembly of polyions has been widely used in recent years to form ultrathin films. In this study, cationic Poly(ethyleneimine) (PEI) and anionic poly(styrene sulfonate) (PSS) were alternately adsorbed onto PDMS through LbL self-assembly. Then poly-D-lysine, gelatin, collagen, fibronectin, laminin, hyaluronic acid, and heparin were coated on PDMS through LbL assembly by alternate adsorption with oppositely charged polyelectrolytes. The film coated on PDMS was hydrophilic compared to the PDMS substrate, as verified through contact angle measurement. The film thickness could be controlled precisely with an accuracy of nanometers by varying the number of layers. The protein nanofilm was biocompatible, enabling endothelial cells, nerve cells, hepatocytes, or smooth muscle cells to adhere and grow. No cell growth was found on the unmodified PDMS substrate.