Enzyme based biosensors suffer from loss of activity and sensitivity. One major reason is due to large molecular weight proteins adsorbing on the surface of the sensor. These proteins affect sensor signal stability and disrupt enzyme function. Thus, one fruitful way to minimize the loss of sensor activity is to filter out large molecular weight compounds before they come in contact with the enzyme based biosensor. Further, the removal of free protein from biological solution helps to increase sensor accuracy and lifetime. Therefore, a microdialysis microneedle is introduced that is capable of excluding large MW compounds based on size. These microneedles have been integrated into a planar microfluidic system capable of sampling and analyzing biological solutions. The integrated microfluidic system includes the assembly of microneedles with on-chip flow channels and electronics together with previously designed positive displacement micropumps, microvalves and a planar electrochemical sensor for biological detection. Multichannel fluidic control for biological sampling, sensor cleansing and recalibration is demonstrated with integrated sensor operation.