RESUMO
Here we compare the amount and the morphology of Au nanostructures electrodeposited from a solution containing 2.5 x 10(-4) M AuCl(4)(-) and 0.1 M cetyltrimethylammonium bromide (CTAB) onto nonseeded and Au-nanoparticle (NP)-seeded mercaptopropyltrimethoxysilane (MPTMS)-functionalized glass/indium tin oxide (glass/ITO) electrodes as a function of the electrode potential and deposition time. The method is similar to the previously reported seed-mediated chemical synthesis of Au nanorods (NRs) in solution and on surfaces, except that we replace the chemical reducing agent (ascorbic acid) with the electrochemical potential. The deposition can be classified into three different potential ranges on the nonseeded and seeded electrodes on the basis of the amount of Au deposited and the morphology of the deposited nanostructures. On the nonseeded glass/ITO/MPTMS electrode, at potentials ranging from -0.30 to -0.20 V, there are a significant number of Au deposits on the surface with mainly branched morphology. At deposition potentials ranging from -0.10 to 0.27 V, there is very little deposition of Au but the few deposits also have a branched morphology. At 0.27 V and higher, there is no Au deposition on the glass/ITO/MPTMS electrode. Because Au seeds catalyze Au deposition, the three potential ranges, the amount of Au, and the morphologies are quite different on the glass/ITO/MPTMS/Au NP seed electrodes compared to those on the nonseeded glass/ITO/MPTMS electrodes. There is a significant amount of Au (more than on the nonseeded electrode) on the surface over a wider range of potentials from -0.30 to 0.27 V, and they have spherical morphology. From 0.30 to 0.35 V, less Au deposits on the electrode and there are 5-15% Au NRs on the surface in addition to spherical NPs. Above 0.35 V, there is no Au deposition on the glass/ITO/MPTMS/Au seed electrode. For depositions within the potential range of 0.30 to 0.35 V on glass/ITO/MPTMS/Au seed electrodes, the size and shape distributions of the Au nanostructures, including NRs, are similar to those previously synthesized by chemical seed-mediated growth in solution and directly on nonconductive surfaces. The yield, length, and aspect ratio of the Au NRs depend on the deposition time; the average length ranges from about 100 to 400 nm for times of 30 to 120 min. The electrochemical seed-mediated growth of Au is optimal from 0.30 to 0.35 V versus Ag/AgCl under our conditions, which could be useful for enhancing the signal in sensing strategies that employ Au NPs as optical or electrochemical tags.
RESUMO
Glial cell-line derived neurotrophic factor (GDNF) has demonstrated robust effects on dopamine (DA) neuron function and survival. A post-translational processing model of the human GDNF proprotein theorizes the formation of smaller, amidated peptide(s) from the proregion that exhibit neurobiological function, including an 11-amino-acid peptide named dopamine neuron stimulating peptide-11 (DNSP-11). A single treatment of DNSP-11 was delivered to the substantia nigra in the rat to investigate effects on DA-neuron function. Four weeks after treatment, potassium (K+) and D-amphetamine evoked DA release were studied in the striatum using microdialysis. There were no significant changes in DA-release after DNSP-11 treatment determined by microdialysis. Dopamine release was further examined in discrete regions of the striatum using high-speed chronoamperometry at 1-, 2-, and 4-weeks after DNSP-11 treatment. Two weeks after DNSP-11 treatment, potassium-evoked DA release was increased in specific subregions of the striatum. However, spontaneous locomotor activity was unchanged by DNSP-11 treatment. In addition, we show that a single treatment of DNSP-11 in the MN9D dopaminergic neuronal cell line results in phosphorylation of ERK1/2, which suggests a novel cellular mechanism responsible for increases in DA function.