and cytosolic localization of 5-TAMRA–labeled folate- targetednanoparticlesinRAW 264.7cells.Thereceptor specificityofthisbindingwasapparentgiventhattheFA conjugate bound to the FR-expressing macrophages and cell lines, while control dendrimer conjugates lacking folate, G5-FITC and G5-5T, failed to bind to these cells. In contrast to our previous studies in KB cells (28), however, the binding of G5-FITC-FA could only be partiallyinhibitedbyexcessfreeFA.Thereasonsforthis incomplete inhibition are not clear, but given that the control conjugates G5-FITC and G5-5T were not taken up by macrophages, it is unlikely that a portion of the uptake of the targeted conjugate was not dependent on FR . Our findings are similar to those of a previous study that showed that the uptake of FA-targeted lipo- somes was completely inhibited by free FA in FR - expressingIGROVcellsbutwasonly 50%inhibitedby free FA in FR -expressing macrophages (44). While it is tempting to speculate that polyvalent binding of the FA-targeted nanoparticle to FR -expressing macro- phages is more avid and therefore more difficult to compete with than the FR -expressing KB cells, this finding requires more extensive examination.