Glutamic Acid Modified Gold Nanorod Sensor for the Detection of Calcium ions in Neuronal Cells

Calcium (Ca²⁺) ions play a crucial role in the functioning of neurons, governing various aspects of neuronal activity such as rapid modulation and alterations in gene expression. Ca²⁺ signaling has a significant impact on the development of diseases and the impairment of neuronal functions. Herein, the study reports a Ca²⁺ ion sensor in neuronal cells using a gold nanorod. The gold nanorod (GA-GNR) conjugated glutamic acid developed in the study was used as a nano-bio probe for the experimental and in vitro detection of calcium. The nanosensor is colloidally stable, preserves plasmonic properties, and shows good viability in neuronal cells, as well as promoting neuron cell line growth. The cytotoxicity and cell penetration of the nanosensor are studied using Raman spectroscopy, brightfield and darkfield microscopy imaging, and MTT assays. The quantification of Ca²⁺ ions in neuronal cells is determined by monitoring the surface plasmon resonance (SPR) of the GA-GNR. The change in the intensity profile in the presence of Ca²⁺ incubated neurons was effectively used to develop a portable prototype of an optical Ca²⁺ sensor, proposing it as a tool for neurodegenerative disease diagnosis and neuromodulation evaluation.