Study of the stability of dopamine encapsulated in TiO2 and TiO2/ 15-crown-5 ether matrix

Dopamine (DA) is the most important catecholamide in the brain, as it is the most abundant and the precursor of other neurotransmitters; it is a highly reactive molecule, which is usually stored inside synaptic vesicles where it is stabilized by the existing low pH However, free cytosolic dopamine easily auto-oxidizes, generating reactive oxygen species. It is also known that the loss of dopaminergic neurons in the substantia nigra is the primary cause of Parkinson's Disease. The purpose of the present study was to prolong the stability of DA, delaying its oxidation by encapsulating it in a TiO2 matrix, giving rise to a TiO2/DA composite prepared by sol-gel. A second sample was obtained by adding 15-crown-5 ether (15C5) to the previous sample (TiO2/DA/15C5). The oxidation process was analyzed by monitoring the color of the solution, optical absorption, and infrared spectroscopy. The color change of the solution from bright orange to dark brown indicated that the oxidation process had begun. In the TiO2/DA sample, complete oxidation of the sample was delayed for 30 days. In the TiO2/DA/15C5 sample, complete oxidation was delayed for 47 days. Transmission electron microscopy showed that TiO2/DA/15C5 had partial crystallization, with anatase and rutile nanocrystals with sizes between 2 and 4.5 nm. Encapsulated DA/ 15C5 may be used as a longer alternative treatment for patients with depression or Parkinson's disease.