Neuronal Maturation-dependent Nano-Neuro Interaction and Modulation

Abstract

Nanotechnology-enabled neuromodulation, a rapidly growing technique, is a promising minimally-invasive tool in neuroscience and engineering for both fundamental studies as well as clinical applications. However, the nano-neuro interactions at different stages of maturation of a neural network and its implications on the nano-neuromodulation remain unclear. Here, we report heterogeneous to homogenous transformation of neuromodulation in a progressively maturing neural network. Utilizing plasmonic fluors as ultrabright fluorescent nanolabels, we reveal that negative surface charge of the nanoparticles renders selective nano-neuro interaction with a strong correlation between the maturation stage of the individual neurons in the neural network and the density of the nanoparticles bound on the neurons. In stark contrast to homogeneous neuromodulation in a mature neural network reported so far, the maturation-dependent density of the nanoparticles bound to neurons in a developing neural network resulted in a heterogeneous optical neuromodulation (i.e., simultaneous excitation and inhibition of neural network activity). This study advances our understanding of nano-neuro interactions and nano-neuromodulation with potential applications in minimally-invasive technologies for treating neuronal disorders in parts of mammalian brain where neurogenesis persists throughout aging.

Plasmon-Enhanced Expansion Microscopy

“…In this study, we harnessed negatively charged plasmonicfluors comprised of IR-650 (called PF-650 henceforth) to demonstrate plasmon-enhanced expansion microscopy. 24 It has been previously reported that negatively charged nanostructures, irrespective of their size, shape, and composition, specifically bind to neurons. 25 Plasmonic-fluor-650 is realized using Au@Ag nanocuboids with an LSPR wavelength at ∼650 nm as a plasmonic nanoantenna (Figure 1B).…”

“…24,25 SEM imaging revealed random orientations of PFs on the soma and higher alignment along the length of neurites (Figure 3A). 24 As expected, we observed a bright fluorescence signal from PFs adsorbed on the neuronal cell body and neurites with minimal background, indicating the specific binding of PFs to neurons (Figure 3B). Following the ExM procedure, confocal microscopy images revealed excellent retention of the structural details across a large sample size (∼400 × 200 μm 2 in pre-ExM scale) (Figure 3C,E).…”

“…As such, we set out to demonstrate plasmon-enhanced ExM using PF-labeled hippo- campal neurons wherein PFs specifically and spontaneously bind to neurons in a maturation-dependent manner (Figure 3 and Figure S1). 24,25 SEM imaging revealed random orientations of PFs on the soma and higher alignment along the length of neurites (Figure 3A). 24 As expected, we observed a bright fluorescence signal from PFs adsorbed on the neuronal cell body and neurites with minimal background, indicating the specific binding of PFs to neurons (Figure 3B).…”