Evaluation Of In-channel Amperometric Detection Using A Dual-channel Microchip Electrophoresis Device And A Two-electrode Potentiostat For Reverse Polarity Separations

In-channel amperometric detection combined with dual-channel microchip electrophoresis is evaluated using a two-electrode isolated potentiostat for reverse polarity separations. The device consists of two separate channels with the working and reference electrodes placed at identical positions relative to the end of the channel, enabling noise subtraction. In previous reports of this configuration, normal polarity and a three-electrode detection system were used. In the two-electrode detection system described here, the electrode in the reference channel acts as both the counter and reference. The effect of electrode placement in the channels on noise and detector response was investigated using nitrite, tyrosine, and hydrogen peroxide as model compounds. The effects of electrode material and size and type of reference electrode on noise and the potential shift of hydrodynamic voltammograms for the model compounds were determined. In addition, the performance of two- and three-electrode configurations using Pt and Ag/AgCl reference electrodes was compared. Although the signal was attenuated with the Pt reference, the noise was also significantly reduced. It was found that lower LOD were obtained for all three compounds with the dual-channel configuration compared to single-channel, in-channel detection. The dual-channel method was then used for the detection of nitrite in a dermal microdialysis sample obtained from a sheep following nitroglycerin administration.363441448Manz, A., Harrison, D.J., Verpoorte, E.M.J., Fettinger, J.C., Paulus, A., Luedi, H., Widmer, H.M., (1992) J. Chromatogr., 593, pp. 253-258Harrison, D.J., Manz, A., Fan, Z., Luedi, H., Widmer, H.M., (1992) Anal. Chem., 64, pp. 1926-1932Jacobson, S.C., Hergenroder, R., Koutny, L.B., Warmack, R.J., Ramsey, J.M., (1994) Anal. Chem., 66, pp. 1107-1113Arora, A., Simone, G., Salieb-Beugelaar, G.B., Kim, J.T., Manz, A., (2010) Anal. Chem., 82, pp. 4830-4847West, J., Becker, M., Tombrink, S., Manz, A., (2008) Anal. Chem., 80, pp. 4403-4419Auroux, P.-A., Iossifidis, D., Reyes, D.R., Manz, A., (2002) Anal. Chem., 74, pp. 2637-2652Mark, J.J.P., Scholz, R., Matysik, F.-M., (2012) J. Chromatogr. A, 1267, pp. 45-64Ghanim, M.H., Abdullah, M.Z., (2011) Talanta, 85, pp. 28-34Coltro, W.K.T., Lima, R.S., Segato, T.P., Carrilho, E., Pereira de Jesus, D., Lucio do Lago, C., Fracassi da Silva, J.A., (2012) Anal. Methods, 4, pp. 25-33Martín, A., Vilela, D., Escarpa, A., (2012) Electrophoresis, 33, pp. 2212-2227Scott, D.E., Grigsby, R.J., Lunte, S.M., (2013) Chem. Phys. Chem., 14, pp. 2288-2294Chen, G., Lin, Y., Wang, J., (2006) Talanta, 68, pp. 497-503Berg, C., Valdez, D.C., Bergeron, P., Mora, M.F., Garcia, C.D., Ayon, A., (2008) Electrophoresis, 29, pp. 4914-4921Gunasekara, D.B., Hulvey, M.K., Lunte, S.M., (2011) Electrophoresis, 32, pp. 832-837Lacher, N.A., Lunte, S.M., Martin, R.S., (2004) Anal. Chem., 76, pp. 2482-2491Mecker, L.C., Filla, L.A., Martin, R.S., (2010) Electroanalysis, 22, pp. 2141-2146Kovarik, M.L., Li, M.W., Martin, R.S., (2005) Electrophoresis, 26, pp. 202-210Wu, C.-C., Wu, R.-G., Huang, J.-G., Lin, Y.-C., Chang, H.-C., (2003) Anal. Chem., 75, pp. 947-952Martin, R.S., Ratzlaff, K.L., Huynh, B.H., Lunte, S.M., (2002) Anal. Chem., 74, pp. 1136-1143Gunasekara, D.B., Hulvey, M.K., Lunte, S.M., Fracassi da Silva, J.A., (2012) Anal. Bioanal. Chem., 403, pp. 2377-2384Chen, C., Hahn, J.H., (2007) Anal. Chem., 79, pp. 7182-7186Chen, C.-P., Teng, W., Hahn, J.-H., (2011) Electrophoresis, 32, pp. 838-843Chen, C., Hahn, J., (2011) Environ. Chem. Lett., 9, pp. 491-497Zhang, G., Du, W., Liu, B.-F., Hisamoto, H., Terabe, S., (2007) Anal. Chim. Acta, 584, pp. 129-135Hulvey, M.K., Frankenfeld, C.N., Lunte, S.M., (2010) Anal. Chem., 82, pp. 1608-1611Wallenborg, S.R., Dorholt, S.M., Faibushevich, A., Lunte, C.E., (1999) Electroanalysis, 11, pp. 362-366Contento, N., Bohn, P., (2014) Microfluid Nanofluid, 17, pp. 1-1

Microfluidic/HPLC combination to study carnosine protective activity on challenged human microglia: Focus on oxidative stress and energy metabolism

Carnosine (beta-alanyl-L-histidine) is a naturally occurring endogenous peptide widely distributed in excitable tissues such as the brain. This dipeptide possesses well-demonstrated antioxidant, anti-inflammatory, and antiaggregation properties, and it may be useful for treatment of pathologies characterized by oxidative stress and energy unbalance such as depression and Alzheimer's disease (AD). Microglia, the brain-resident macrophages, are involved in different physiological brain activities such synaptic plasticity and neurogenesis, but their dysregulation has been linked to the pathogenesis of numerous diseases. In AD brain, the activation of microglia towards a pro-oxidant and pro-inflammatory phenotype has found in an early phase of cognitive decline, reason why new pharmacological targets related to microglia activation are of great importance to develop innovative therapeutic strategies. In particular, microglia represent a common model of lipopolysaccharides (LPS)-induced activation to identify novel pharmacological targets for depression and AD and numerous studies have linked the impairment of energy metabolism, including ATP dyshomeostasis, to the onset of depressive episodes. In the present study, we first investigated the toxic potential of LPS + ATP in the absence or presence of carnosine. Our studies were carried out on human microglia (HMC3 cell line) in which LPS + ATP combination has shown the ability to promote cell death, oxidative stress, and inflammation. Additionally, to shed more light on the molecular mechanisms underlying the protective effect of carnosine, its ability to modulate reactive oxygen species production and the variation of parameters representative of cellular energy metabolism was evaluated by microchip electrophoresis coupled to laser-induced fluorescence and high performance liquid chromatography, respectively. In our experimental conditions, carnosine prevented LPS + ATP-induced cell death and oxidative stress, also completely restoring basal energy metabolism in human HMC3 microglia. Our results suggest a therapeutic potential of carnosine as a new pharmacological tool in the context of multifactorial disorders characterize by neuroinflammatory phenomena including depression and AD