Application of reduced graphene oxide in the photolithography process of biodegradable composite to improve its electrical conductivity

Introduction

The combination of single-walled carbon nanotubes (SWCNTs) and reduced graphene oxide (rGO) in the photoresist minimizes the amount of carbon particles. While developing neuroimplants designed to restore damaged neural networks or modulate pain transmission, the key requirements are both biocompatibility and electrical conductivity.

Methods

Photolithography of the composite was performed with an ytterbium laser at a wavelength of 1035 nm with pulses of 100 ns duration, repetition rate of 30 kHz and power of ~550 mW. The photoresist used was SWCNT 0.6 mg/mL, rGO 0.6 mg/mL and SWCNT (0.3 mg/mL)/rGO (0.3 mg/mL). The final biohybrid structure contains proteins, chitosan and eosin Y. The formation of the structure was simulated by the molecular dynamics method with SEM monitoring.

The specific electrical conductivity of 15 5×5 mm layers was determined using the four-probe method. Biodegradation was estimated by the mass of the swollen sample in an isotonic sodium chloride solution and dried, with the following enzymes: lipase - 25,000 PhEur; amylase - 18,000 PhEur and protease - 1000 PhEur. In vitro biocompatibility studies were conducted with the Neuro 2A cell line with the MTT test for 72 hours.

Results

Specific conductivity: 17 mS/cm (rGO), 19 mS/cm (SWCNT) and 35 mS/cm (SWCNT/rGO). The mass loss of the SWCNT/rGO sample was 40%, the swelling increased by 20%, and the optical density (OD) of the MTT test was 0.76. Control cover glass OD=0.62. Enzymes degraded the sample in a week. Simulation and SEM confirmed laser-induced rearrangement of SWCNTs with RGO into single nanostructures with the formation of non-hexagonal carbon elements.

Conclusions

The composite developed in the process of degradation can be replaced by biological tissue during this period with the maintenance of electrical conductivity.

Funding: The work was supported by the Ministry of Education and Science of the Russian Federation (project FSMR-2024-0003).