In vitro screening of metal oxide nanoparticles for effects on neural function using cortical networks on microelectrode arrays

Nanoparticles (NPs) may translocate to the brain following inhalation or oral exposures, yet higher throughput methods to screen NPs for potential neurotoxicity are lacking. The present study examined effects of 5 CeO₂ (5– 1288 nm), and 4 TiO₂ (6–142 nm) NPs and microparticles (MP) on network function in primary cultures of rat cortex on 12 well microelectrode array (MEA) plates. Particles were without cytotoxicity at concentrations ≤50 µg/ml. After recording 1 h of baseline activity prior to particle (3–50 µg/ml) exposure, changes in the total number of spikes (TS) and # of active electrodes (#AEs) were assessed 1, 24, and 48 h later. Following the 48 h recording, the response to a challenge with the GABA_A antagonist bicuculline (BIC; 25 µM) was assessed. In all, particles effects were subtle, but 69 nm CeO₂ and 25 nm TiO₂ NPs caused concentration-related decreases in TS following 1 h exposure. At 48 h, 5 and 69 nm CeO₂ and 25 and 31 nm TiO₂ decreased #AE, while the two MPs increased #AEs. Following BIC, only 31 nm TiO₂ produced concentration-related decreases in #AEs, while 1288 nm CeO₂ caused concentration-related increases in both TS and #AE. The results indicate that some metal oxide particles cause subtle concentration-related changes in spontaneous and/or GABA_A receptor-mediated neuronal activity in vitro at times when cytotoxicity is absent, and that MEAs can be used to screen and prioritize nanoparticles for neurotoxicity hazard.