In vivo sampling using loop microdialysis probes coupled to a liquid chromatograph

Area of Science:

• Biomedical Engineering
• Pharmacokinetics
• Analytical Chemistry

Background:

• Traditional microdialysis probes (1-4 mm membranes) are optimized for neuroscience.
• Subcutaneous tissue sampling requires probes with higher relative recovery.
• Longer membrane probes (20-100 mm) offer potential for improved subcutaneous sampling.

Purpose of the Study:

• To characterize and optimize microdialysis probes for subcutaneous tissue applications.
• To evaluate the impact of probe design parameters on sampling performance.
• To explore the utility of optimized probes for in vivo therapeutic drug monitoring.

Main Methods:

• Investigated "straight through" and "loop type" probe configurations.
• Examined effects of membrane area, probe size, tubing dimensions, and flow rate.
• Compared polyacrylonitrile and regenerated cellulose membrane fibers of varying geometries (3-10 cm length).
• Varied inlet/outlet tubing inner diameter (25-110 microns) and length (10-50 cm).

Main Results:

• Longer membrane probes (20-100 mm) demonstrated increased relative recovery compared to shorter probes.
• Optimized probe configurations achieved relative concentration recovery >50% at flow rates >5 microliters/min.
• Identified key parameters influencing relative recovery, collection rate, and bulk flow.

Conclusions:

• Microdialysis probes with larger membrane surface areas are effective for subcutaneous tissue sampling.
• Optimized probe designs facilitate higher recovery rates essential for therapeutic drug monitoring in vivo.
• This approach enables effective monitoring of drug concentrations in subcutaneous tissue of awake animals.