The microcapsules in drug delivery systems can prevent degradation of drugs and help to control the release rate. To enhance the targeted delivery effect of the microcapsules to cancer cells, some specific ligands such as folic acid (FA) are necessarily further conjugated. Herein, covalent poly(allylamine hydrochloride) (PAH) multilayers were fabricated on CaCO(3) microparticles under the cross-linking of glutaraldehyde, which were further immobilized with different amount of FA molecules via the spacer of diamino terminated poly(ethylene glycol) (PEG). As a comparison study, four types of microcapsules, i.e., the PAH capsules, the PAH capsules grafted with PEG, and the PAH capsules conjugated with two different amount of FA via the PEG spacer were prepared. Their chemical and physical structures were confirmed by infrared spectroscopy, UV-vis spectroscopy and scanning electron microscopy. In vitro cell culture found that the cellular uptake of the PAH capsules grafted with PEG was reduced significantly compared with that of the pure PAH capsules. The FA-modified microcapsules could be selectively delivered into HepG2 tumor cells which overexpress FA receptors but not into the endothelial cells. The number of HepG2 cells which ingested the FA-conjugated capsules showed a positive correlation with FA amount. The results indicate that these FA conjugated capsules have a high selectivity to be delivered to tumor cells, endowing them with a larger opportunity functioning as targeted delivery vehicle for anticancer drugs. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 3710-3716, 2011