Although Camptothecin (CPT) has significant antitumor activity to lung, ovarian, breast, pancreas, and stomach cancers; lactone ring opening causes a reduction in cytotoxic activity and severe side effects in physiological conditions (pH: 7.4, 37 degrees C) due to decreased cell membrane binding, membrane diffusibility, and intrinsic potency against the topoisomerase target. Taken into consideration the targeted delivery advantage of biocompatible magnetic particles, in order to contribute to the removal of the handicap ( lactone ring opening), the current study investigated stability, release, and in vitro bioactivity of CPT in oleic acid (OA)-pluronic F127 (PL) coated iron oxide micro and nanoparticles. CPT encapsulated magnetite micro (similar to 10 mu m) and nano (similar to 30 nm) formulations were synthesized without changing their magnetic properties. Analysis of encapsulated CPT illustrated that over 99% of the lactone form was protected in the magnetic particle formulations and release of CPT from the magnetic micro and nanoparticles lasted for 9 and 4 days respectively. In addition, in a representative in vitro cytotoxicity study, CPT encapsulated OA-PL stabilized magnetite microparticles were approximately 65% more effective than free CPT to inhibit 100% cell growth on three different human liver carcinoma cell lines. Therefore, the OA-PL stabilized iron oxide formulation is ideal for achieving targeted and sustained CPT delivery in bioactive lactone form to overcome its handicaps in clinical conditions.