Use of an intraluminal guide wire in linear microdialysis probes: effect on recovery?

Background/purpose: For microdialysis studies in the skin, laboratory-made linear probes are often used. Probes can be assembled with or without a stainless-steel guide wire in the lumen of the dialysis fibre. From a theoretical viewpoint, this will alter the performance of the probe. The aim of this study was to compare the in vitro microdialysis recovery using probes with and without an internal guide wire, employing two different model drugs and a range of perfusate flow rates.

Methods: In vitro microdialysis recovery experiments were performed with and without internal guide wires at perfusion flow rates from 1 to 15 microL/min, using either salicylic acid or metronidazole as test compounds at 5 mg/L. Phosphate buffer (pH 7.4) was used as perfusate. Dialysates were analysed by a validated HPLC assay with spectrophotometric detection.

Results: For both test compounds, the mean microdialysis recovery did not differ significantly between microdialysis probes with and without an internal guide wire at lower flow rates. At very high flow rates (10-15 microL/min), a significant difference in recovery could be seen for probes with internal guide wires when compared with probes without.

Conclusions: The use of a stabilizing internal guide wire in linear microdialysis probes did not influence the in vitro recovery of microdialysis at volumetric flow rates below 10 microL/min. These are the flow rates most frequently used for in vivo microdialysis studies in the skin.