Biocompatibility and Biodegradation of Sensors Enabled By Zinc Oxide Thin Films

Pooja Nanjannavar, Tanin Izadi, Vitaliy Avrutin, Nastassja Lewinski

Implantable biosensors for long term monitoring of disease biomarkers could improve survival rates and outcomes by giving individuals the ability to monitor their own health and take preemptive action against disease. However, the human body is known to reject implanted objects through foreign body reactions, biofouling, and inflammation. The objective of this study was to characterize the biodegradation rate of zinc oxide thin film coated biosensors to determine whether implanted biosensors could lead to potential cytotoxicity in human cells. We have measured the dissolution rate of zinc oxide thin films after 24 hours of incubation in cell culture media. We also tested the cytotoxicity of these extracts as well as the cytotoxicity resulting from direct contact of the coated sensor with cells. Zinc oxide concentrations in the media were measured using ICP-OES. Cytotoxicity was determined by measuring changes in metabolic activity using the tetrazolium-based MTS assay and changes in membrane integrity using the lactate dehydrogenase assay after 24 hours of exposure. Results from the tested sensor extracts show that there is little cytotoxicity (> 80% cell viability) associated with zinc oxide dissolution. Direct growth of cells on sensors preincubated with media also resulted in no observable difference in growth compared to the negative control. These findings demonstrate in vitro biocompatibility of zinc oxide thin film coated sensors for short term exposure. Future work will assess longer term biocompatibility and biostability.