In vitro characterization of microdialysis sampling of macromolecules

Experiments were performed to characterize the in vitro collection of macromolecules using microdialysis. Fluorescently labeled proteins and dextrans ranging from 3000 to 150 000 were sampled using a 10-mm, 100 000 molecular weight cutoff, polyethersulfone microdialysis probe. Published models describing microdialysis mass transport of small molecules were examined to determine their appropriateness for sampling of macromolecules. Collection efficiencies, reported as relative recoveries, for macromolecules from 3000 to 70 000 ranged from 5 to 44%. Collection efficiencies determined for microdialysis sampling of macromolecules follow the functionality of published models, although experimental mass transport resistances are to some extent smaller than predicted. Implications of the current study for in vivo microdialysis sampling of cytokines and growth factors are discussed.