Among the most common causes of death in the world, neurological diseases are one of the heaviest burdens for humanity. To guarantee a better quality of life, we would like to understand them and cure them. Genetically Encoded Voltage Indicators (GEVIs) are powerful optogenetic tools that enable the all-optical measurement of membrane potential in neurons. However, visualizing the subcellular localization of these fluorescent proteins is limited by the diffraction of light. Because of this strict limit, accurate modeling of the electrical signals in dendritic spines and subcellular structures is still a subject of debate. Plasmonic enhancement using gold nanoparticles is a promising novel solution to selectively obtain optical signals reporting synaptic transmission. The coupling between gold nanoparticles and fluorescent proteins can lead to locally higher quantum yields and consequently to brighter diffraction-limited spots. In this work a complete approach from simulations to biological application has been taken. Colloidally grown gold nanostars have been characterized, computationally modelled and tested on HEK cells expressing an Archaerhodopsin-based GEVI. The results discussed highlight the tunability and the stability of such nanoparticles, as well as some practical limitations to overcome in future experiments. The proof-of-principle could unlock a novel, powerful tool for neuroscience.