# Evaluation of Lipid Nanoparticles as Vehicles for Optogenetic Delivery in Primary Cortical Neurons

## TL;DR

This study explores lipid nanoparticles as a non-viral method for delivering optogenetic genes to neurons, showing potential as an alternative to viral vectors.

## Contribution

The study introduces lipid nanoparticles as a viable non-viral delivery system for optogenetics in cortical neurons.

## Key findings

- Lipid nanoparticles showed higher transfection efficiency than lipofectamine in most treatments.
- Neuron morphology and cell viability were not significantly affected by lipid nanoparticles.
- Electrophysiological parameters were altered, indicating potential for functional optogenetic control.

## Abstract

Background: Gene therapy has experienced significant development since its origin decades ago, resulting in therapies for a wide range of diseases. In this context, optogenetics has emerged as a promising therapy for treating diseases in a precise spatiotemporal way using light. Transporting optogenetic genes to target cells is achieved using viral vectors, specifically AAV vectors. These vectors present limited cargo capacity, and a large percentage of the population carries AAV neutralizing antibodies. In this regard, lipid nanoparticles can overcome some of the previously mentioned problems of AAV vectors, making them prime candidates for optogenetic delivery. Methods: In this study, we evaluated their suitability for the delivery of the ChrimsonR plasmid in neurons in vitro. Results: In rat cortical neurons, in most of the concentrations tested, there was no reduction in several neuron morphological parameters that we measured when compared to another non-viral nanoparticle called lipofectamine. Transfection efficiency was significantly higher compared to lipofectamine in almost all treatments. Further in vitro analysis showed that electrophysiological parameters were altered, with reduced signal amplitudes; however, cell viability assays showed no decline in cell viability. Conclusions: These results demonstrate that lipid nanoparticles represent a promising non-viral platform for optogenetic delivery, though formulation optimization is required to achieve full functional efficacy.