A cell-compatible conductive film from a carbon nanotube network adsorbed on poly-L-lysine

Single-walled carbon nanotubes (SWNTs) have shown promise for use in organic electronic applications including thin film transistors, conducting electrodes, and biosensors. Additionally, previous studies found applications for SWNTs in bioelectronic devices, including drug delivery carriers and scaffolds for tissue engineering. There is a current need to rapidly process SWNTs from solution phase to substrates in order to produce device structures that are also biocompatible. Studies have shown the use of surfaces covalently functionalized with primary amines to selectively adsorb semiconducting SWNTs. Here we report the potential of substrates modified with physisorbed polymers as a rapid biomaterials-based approach for the formation of SWNT networks. We hypothesized that rapid surface modification could be accomplished by adsorption of poly-L-lysine (PLL), which is also frequently used in biological applications. We detail a rapid and facile method for depositing SWNTs onto various substrate materials using the amine-rich PLL. Dispersions of SWNTs of different chiralities suspended in N-methylpyrrolidinone (NMP) were spin coated onto various PLL-treated substrates. SWNT adsorption and alignment were characterized by atomic force microscopy (AFM) while electrical properties of the network were characterized by 2-terminal resistance measurements. Additionally, we investigated the relative chirality of the SWNT networks by micro-Raman spectroscopy. The SWNT surface density was strongly dependent upon the adsorbed concentration of PLL on the surface. SWNT adsorbed on PLL-treated substrates exhibited enhanced biocompatibility compared to SWNT networks fabricated using alternative methods such as drop casting. These results suggest that PLL films can promote formation of biocompatible SWNT networks for potential biomedical applications.