Biocompatibility evaluation of encapsulated silver-based printed circuits for in-vitro long-term sensing devices

Abstract

Metal-based inks, such as silver nanoparticle (AgNPs) dispersions, are standard solutions in printed electronics (PE) due to their high bulk conductivity, stability, and commercial availability. Conductive functional printed patterns have been exploited for several applications, such as (wearable) sensors, antennas, transistors, batteries. Recently, PE has also been widely investigated for biomedical and bioelectronic interfaces. In this case, the choice of biocompatible materials is crucial to ensure biological activities of the seeded cells. For instance, the release of Ag+ ions in the medium culture in in-vitro cultures, is known to induce cytotoxicity, in a dose-, size-, and time-dependent way, causing oxidative stress and eventually cellular death. Hence, an encapsulation step of the printed pattern is usually performed to reduce such risk, by inducing however additional limitations and complications on the design and production. This work investigates the biocompatibility of a commercial Aerosol Jet® Printed (AJ®P) AgNPs-based ink (Øavg,particle size = 35 nm, Ag content ~50 wt%) use to print conductive circuits for in-vitro bioelectrical sensing. Particularly, the ink was AJ® printed on the top of stereolithography (SLA) samples coated with Parylene-C, and further encapsulated with polydimethylsiloxane (PDMS).Cell viability assays were evaluated using both in adhesion and suspension cell type, such fibroblasts and B-Lymphoblastoid cell line respectively, at different time points from 7 days till 21 days to verify cellular activity and proliferation for long term usage. This work provides new insights concerning the use of encapsulated conductive AgNPs-based circuits for in-vitro long-term sensing devices.