title: Self-built microdialysis probes with improved recoveries of ATP and neuropeptides.
abstract: BACKGROUND
  Microdialysis is an established technique for collecting small molecular weight substances (e.g. neurotransmitter and energy metabolites) from the extracellular space. The major element of microdialysis is the probe which contains a semi-permeable membrane and is exposed to the interstitial space. As the microdialysis technique has major advantages, e.g. versatility and use in awake animals, commercially produced probes are in great demand.
  
  
  METHODS
  We here present the design of a probe assembly step by step which will enable researchers to build custom-made probes. Probe recoveries of substances with different molecular weight (ranging from 100 to 1600 Da) were compared for three different probes (CMA 12 Elite probe, custom-made 10 kDa and 30 kDa probes). Recoveries of glucose, lactate, acetylcholine, choline, ATP and the neuropeptides angiotensin II, substance P and somatostatin are presented.
  
  
  RESULTS
  We found that the 10 kDa probe is only useful for compounds up to 1000 Da while recoveries of the CMA-12 Elite Probe are variable and apparently dependent on ionic charges of analytes. The recovery of the custom-made 30 kDa probe is highest and evidently not influenced by physicochemical parameters of analytes. In a further optimization step, we describe the use of ZipTip(®) μC-18 collection tips to replace the outlet tubing when purifying the dialysate for MALDI-MS measurements of neuropeptides.
  
  
  METHODS
  The results show that self-built microdialysis probes can be equally or more effective than commercially available probes.
  
  
  CONCLUSIONS
  Self-built microdialysis probes with large pore-membranes are capable of dialyzing ATP and neuropeptides.
authors.affiliation: Department of Pharmacology, Biocenter N260, Max-von-Laue Str. 9, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany.
authors.forename: Jana
authors.initials: J
authors.lastname: Lietsche
authors.affiliation: Department of Pharmaceutical Chemistry, Biocenter N260, Max-von-Laue Str. 9, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Gorka
authors.affiliation: Department of Pharmacology, Biocenter N260, Max-von-Laue Str. 9, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Hardt
authors.affiliation: Department of Pharmaceutical Chemistry, Biocenter N260, Max-von-Laue Str. 9, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Karas
authors.affiliation: Department of Pharmacology, Biocenter N260, Max-von-Laue Str. 9, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany. Electronic address: klein@em.uni-frankfurt.de.
authors.forename: Jochen
authors.initials: J
authors.lastname: Klein
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis / Q000378:metabolism*; D000818:Animals; D002555:Cerebrospinal Fluid / Q000737:chemistry / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D066298:In Vitro Techniques; D019344:Lactic Acid / Q000378:metabolism; D017551:Microdialysis / Q000295:instrumentation* / Q000379:methods*; D008970:Molecular Weight; D009479:Neuropeptides / Q000032:analysis / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D009479:Neuropeptides; D019344:Lactic Acid; D000255:Adenosine Triphosphate; D005947:Glucose
keywords: Acetylcholine; Custom-made probes; Glucose; Lactate; Recovery; ZipTip