To explore passive targeting property of Polyethylene glycol (PEG) modification of 5-fluorouracil magnetic albumin microspheres (PEG 5-Fu-MAMS) and 5-fluorouracil magnetic albumin microspheres (Fu-MAMS) for colorectal cancer tissus.

Twenty mice were randomly divided into Group 5- Fu- MAMS(n=10)and Group PEG-5-Fu-MAMS(n=10). They were injected through the vena caudalis at the dose of 8mg/kg of free drug respectively.After a magnetic field for 30 minutes, the mice were killed, the orbital cavity blood was sampled immediately.The concentrations of 5-fluorouracil in colorectal carcinoma and renal tissue and serum were determined by the high performance liquid chromatography (HPLC). The difference of the level of 5-Fu was compared with t-test.

The 5-Fu concentration of colorectal carcinoma in PEG-5-Fu-MS (51.21±2.12)μg/mL group was significantly higher than that of 5-Fu-MS group[( 33.07±8.21)μg/mL, t=78.69, P<0.05]. But the 5-Fu concentration of serum in PEG-5-Fu-MAMS [(1.69 ± 0.53)μg/mL] was significantly lower than that of 5-Fu-MAMS group[(6.78 ± 0.23)μg/mL, t=18.76, P<0.05]. The 5-Fu concentration of kidney tissue in PEG-5-Fu-MAMS group (21.1±2.3)μg/mL was significantly lower than that of the 5-Fu-MAMS group [(38.2±4.9)μg/mL, t=39.23, P<0.05)].

The study suggests that the affinity with colorectal cancer of PEG-5-FU-MASA to colorectal cancer is stronger than that of the 5-FU-MAMS .PEG-5-FU-MAMS are expected to become a new targeted therapy of colorectal cancer.