Hybrid carriers were successfully synthesized by chemically binding OH-terminated fourth generation poly(amido amine) dendrimer and folic acid on graphene oxide (GO) with a size of 100 nm, and their drug carrier ability was compared with hybrids of 1500 nm GO. The small hybrid carriers possessed a 1.3 times lower loading capacity (1.43 g/g(GO)) for doxorubicin (DOX) than the large hybrid carriers. However, the amount (86%) of DOX released at pH 5.5 from the small hybrids after 72 h was 1.14 times larger than from the large hybrids. This difference could be due to the extent of pi-pi interaction between DOX and the graphitic domain on GO. In vitro MU assays revealed that the small hybrids led to higher cell viability than 63% at 0.75 mu g/ml in HeLa human cervical cancer cells. An investigation of the intracellular uptake of hybrid carriers revealed the efficient internalization of small hybrids in the HeLa cells (97% at 62.5 mg/ml). Taken together, these results indicate that the small hybrids consisting of 100 nm GO carrier can successfully load and deliver the anticancer drug DOX into HeLa cells. In the carriers, dendrimer had a role of stable suspension of the hybrids in water, and folic acid acted as an effective anchoring of the hybrids on HeLa cells. The present investigation highlights the potential use of these hybrid materials as nanocarriers with high loading and releasing efficiency for the delivery of anticancer drugs to tumor cells. (C) 2015 Elsevier B.V. All rights reserved.