Carbon Quantum Dots: Synthesis, Characterization and Their Application in Neuronal Photostimulation
Neurostimulation has shown to be useful in clinical medicine. It can be accomplished by pharmacological, genetic, electrical, optical, and magnetic techniques, with demonstrated efficacy in the treatment of Parkinson's disease and other neuropsychiatric diseases. The conventional way for stimulation of neural tissues is through electrical stimulation using implanted electrodes. Instead, photostimulation provides effective non-invasive routes for controlling and manipulating neural activity with high spatiotemporal resolution, without the mechanical instability and surgical difficulties of electrical components. In this regard, photoactive nanomaterials like quantum dots (QDs) offer adjustable compositional and electronic properties that can meet the biocompatibility and charge transport requirements of neural interfaces. However, little attention has been paid to their potential in neurostimulation. Even though the outstanding properties of Cd, Pb and Hg based QDs make them ideal photoactive materials, their use in biointerfaces raises concerns about the biocompatibility. In contrast, Carbon QDs could offer a non-toxic alternative while preserving the optical properties of QDs containing heavy metals. Herein, the application of biocompatible Carbon QDs as a non-invasive alternative for neural stimulation is explored. In this work, photoluminescent Carbon QDs were obtained by the alkali-assisted electrochemical method controlling the size and thus optoelectronic properties by varying the applied current. The optical properties of the synthesized Carbon QDs were characterized by UV-Vis and photoluminescence spectroscopy, their size by Dynamic Light Scattering, and morphology by Fourier transform and Raman spectroscopies. A study of the conductivity in the THz regime found that when illuminated with UV light, Carbon QDs showed an increase in their conductivity. Upon incorporation of Carbon QDs in hippocampal neurons, the findings indicate excellent biocompatibility and an increment of ten percent in neuronal activity. The author suggests that QD-based photoactivation could offer a noninvasive alternative for next generation neurostimulation devices to treat neurological disorders.