Heparin-immobilized beads were compared against antibody-immobilized beads for improving the collection of targeted cytokines through microdialysis sampling probes. Heparin offers an advantage over antibodies with respect to its stability and cost. The cytokines, MCP-1 and RANTES, exhibited increased flux through the probes when either heparin-immobilized or antibody-immobilized beads were included in the perfusion fluid.This suggests that heparin-immobilized beads may be a viable alternative to antibody-immobilized beads to increase the flux of select cytokines during microdialysis sampling.