Organic semiconductors (OSCs) are exciting materials for bioelectronics applications, combining the soft mechanical properties of tissue with the electronic properties of semiconductors.[1] However, OSCs are typically hydrophobic and require additional adhesion layers to interface with cells, restricting control of the electronic communication at this interface. Here we demonstrate multiple surface treatment technologies that can modify the OSC surface for cell adhesion directly, without influencing its electronic properties.
OSCs were treated with nitrogen plasma ion implantation and UV-ozone for differing time periods. The surface chemistry and depth of treatment penetration were probed with XPS and surface energy measurements. Electrical properties of the films, including transport energy levels, dielectric constant, impedance and transient photoconductivity, were probed as a function of different treatment times. Neuronal cell populations were cultured onto the treated OSCs for 7 days, with anatomical biocompatibility determined via live/dead assay and functional biocompatibility determined using a neuron-specific immunolabel.
XPS analysis revealed the surface treatments creates polar functional groups on the OSC surface, which are able to tune the contact angle and persist to a penetration depth of ~15 nm. The energy level of the material HOMO at the surface decreased by 200 mV, though the bulk electrical properties remained unaffected. The surface treated films showed a substantial increase in both cell adhesion and number of live cells, with stained neurons exhibiting neurite extensions up to 140 µm after 7 days in culture, demonstrating high neural functionality.
References:
[1] C. P Sherwood, R. Crovadro, J. A. Posar, N. Brichta, M. P. Simunovic, F. Louie, P. C. Dastoor, A. M. Brichta, J. M. Cairney, N/ P. Holmes, M. J. Griffith; Adv. Mater. Interfaces, 2023, 10, 2202229.