Effect of the concentration of water on dopamine occluded in nanostructured silica reservoirs for the treatment of Parkinson disease
T. López, D. Esquivel, E. Ortiz, R. González.
Universidad de Gunajuato, MX
Keywords: sol-gel, silica, dopamine, controlled release
Abstract:Parkinson’s disease (PD) is a progressive neurodegenerative age related disease. PD shows characteristic symptoms such as slow movement, bradykinesia, tremors and rigidity; due to the loss of dopaminergic neurons in the sustantia nigra pars compacta in the midbrain. Dopamine is responsible for many functions in the brain such as motor activity, motivation and reward. Up to now the treatment of PD is performed through the use of the natural precursor of dopamine, L-Dopa, because dopamine cannot cross the blood-brain-barrier (BBB) and is rapidly oxidized to dopaquinone. This is the reason as to why Parkinson’s disease may progress either rapidly or gradually over time. The aim of this research was to implant a reservoir capable of releasing dopamine directly into an area of the brain where the damaged tissue is located. The molecule was stabilized in a new nanostructured and functionalized sol-gel silica reservoir. In order to release the correct dose, the concentration of water was varied from 5 to 40 mol/mol of TEOS. The SiO2-Dopamine systems obtained were characterized by N2 adsorption, 13C NMR and FTIR spectroscopy. The controlled drug release profiles were then performed by UV spectroscopy. The brain tissue biocompatibility tests were performed using stereotactic surgery. The textural analyses show the existence of a maximum surface area of 508 m2/g, when the water concentration used to prepare the silica network was 25 mol/mol of TEOS. The mean pore diameter varied between 5-10 nm. The stability of dopamine in the matrix was probed using FTIR. Bands at 2500, 2600 and 2700 cm-1 are assigned to the N-H, C-H and C-O-H vibrations of dopamine. A fast sustained dopamine delivery was observed for 72 hours, after this, the delivery showed pseudo order zero kinetics. These results suggest that SiO2-dopamine reservoirs may be a good alternative for the treatment of Parkinsons disease.