Microdialysis sampling membrane performance during in vitro macromolecule collection.

Microdialysis sampling is well-established for sampling small molecules. Recently, there has been an increased interest toward collecting macromolecules using microdialysis sampling. In this work, fluorescein isothiocyanate-labeled dextrans (FITC-dextrans) with molecular weight between 10 and 70 kDa were chosen as representative molecules to study analyte mass transport properties during microdialysis sampling using different lengths (2 and 10 mm) of 100-kDa MWCO polyethersulfone membranes. Experiments were performed in both well-stirred and quiescent phosphate-buffered saline solutions as well as in a 0.3% agar solution. Different fundamental parameters affecting microdialysis sampling of macromolecules, including effective membrane diffusion coefficients, were evaluated. The applicability of the most-often-cited Bungay et al. mass transfer model was compared to experimental data for the FITC-dextrans. For the larger macromolecules, the membrane provides a significant mass transport resistance most likely caused by hindered diffusion. These experimental aspects that are critical to microdialysis sampling of macromolecules are presented.