Evaluation of a Portable Microchip Electrophoresis Fluorescence Detection System for the Analysis of Amino Acid Neurotransmitters in Brain Dialysis Samples

Abstract

A portable fluorescence detection system for use with microchip electrophoresis was developed and compared to a benchtop system. Using this system, six neuroactive amines commonly found in brain dialysate—arginine, citrulline, taurine, histamine, glutamate, and aspartate—were derivatized offline with naphthalene-2,3-dicarboxaldehyde/cyanide, separated electrophoretically, and detected by fluorescence. Limits of detection for the analytes of interest were 50nM – 250nM for the benchtop system and 250 nM – 1.3 μM for the portable system, both of which were adequate for analyte determination in brain microdialysis samples. The portable system was then demonstrated for the detection of the same six amines in a rat brain microdialysis sample.

Monitoring carnosine uptake by RAW 264.7 macrophage cells using microchip electrophoresis with fluorescence detection

“…A separation of carnosine from the most abundant amino acids reported to be in macrophage cells was developed using standards. 24 The separation employed an all-glass 15-cm glass microchip with a BGE of 20 mM sodium borate (pH 9.2) and a field strength of 420 V/cm. None of the abundant amino acids co-migrated with carnosine under these optimal separation conditions (Fig.…”

“…24 Briefly, a 445-nm PhoxX diode laser (Market Tech, Scotts Valley, CA, USA) was coupled to an Eclipse Ti-U inverted microscope (Nikon Instruments Inc., Melville, NY, USA) via a fiber optics cable. As CBI derivatives have an emission maximum of 490 nm, 23 the emission light was filtered through a long-pass edge filter with a 480 nm cutoff before being focused onto a photomultiplier tube (Hammatsu Corporation, Bridgewater, NJ, USA).…”

“…These CBI derivatives have previously been used for the detection of biogenic amines by ME-LIF. 24–26 …”

Separation-Based Methods Combined With Microdialysis Sampling for Monitoring Neurotransmitters and Drug Delivery to the Brain

“…The initial report of this portable system compared it to a traditional benchtop system for the offline analysis of NDA/CN -derivatized amino acid neurotransmitters in rat brain microdialysate samples. While the port able system does suffer from higher limits of detection and quantitation than the benchtop system, it was still possible to detect basal levels of six amino acids in brain microdialysate in under 250 seconds (Figure 1.11B) (Oborny et al, 2016). Efforts are ongoing to couple this separation and detection scheme to previously reported online microdialysis sampling and derivatization (Nandi et al, 2013).…”

“…Currently, this system employs microdialysismicrochip electrophoresis with light emitting diodeinduced fluorescence detection (Oborny et al, 2016). As discussed in Section 1.4.3, microchip electrophoresis enables the fast separation of small volume samples on a microchip platform, which makes it amenable to clinical analysis.…”