Nanodiamonds-induced effects on neuronal firing of mouse hippocampal microcircuits

TL;DR

This study investigates how fluorescent nanodiamonds affect hippocampal neuron activity, revealing decreased synaptic event frequencies and altered action potential properties, with implications for their use in biomedical applications.

Contribution

It provides novel insights into the electrophysiological effects of nanodiamonds on neuronal networks, highlighting specific changes in firing and synaptic activity.

Findings

FNDs reduce inhibitory and excitatory miniature postsynaptic current frequencies.

FNDs decrease neuronal firing rates by approximately 36%.

Burst synchronization remains unaffected by FND exposure.

Abstract

Fluorescent nanodiamonds (FND) are carbon-based nanomaterials that can efficiently incorporate optically active photoluminescent centers such as the nitrogen-vacancy complex, thus making them promising candidates as optical biolabels and drug-delivery agents. FNDs exhibit bright fluorescence without photobleaching combined with high uptake rate and low cytotoxicity. Focusing on FNDs interference with neuronal function, here we examined their effect on cultured hippocampal neurons, monitoring the whole network development as well as the electrophysiological properties of single neurons. We observed that FNDs drastically decreased the frequency of inhibitory (from 1.81 Hz to 0.86 Hz) and excitatory (from 1.61 Hz to 0.68 Hz) miniature postsynaptic currents, and consistently reduced action potential (AP) firing frequency (by 36%), as measured by microelectrode arrays. On the contrary, bursts synchronization was preserved, as well as the amplitude of spontaneous inhibitory and excitatory events. Current-clamp recordings revealed that the ratio of neurons responding with AP trains of high-frequency (fast-spiking) versus neurons responding with trains of low-frequency (slow-spiking) was unaltered, suggesting that FNDs exerted a comparable action on neuronal subpopulations. At the single cell level, rapid onset of the somatic AP ("kink") was drastically reduced in FND-treated neurons, suggesting a reduced contribution of axonal and dendritic components while preserving neuronal excitability.