Abstract: Abstract:Objective To construct the immunoliposomal Paclitaxel tagged with trastuzumab F(ab′)2 and to investigate its killing effects on human colorectal cancer cells in vitro. Methods Liposomal paclitaxel was made in a reversal-phase evaporation method and trastuzmab F(ab′)2 was obtained by cutting the J hinge at the Fc side of the antibodies with pepsin，then the trastuzmab F(ab′)2 and the liposomal Paclitaxel were linked together.The figures of immunoliposomes were observed by TEM and their size distribution was measured by graphics software.The encapsulation efficiency of the immunoliposomes was estimated by RP-HPLC.The immune activity of immunoliposomes was evaluated using the fluorescence microscopy after the fluorescent immunoliposomes or liposomes were incubated together with HT-29 cells.Apoptotic index of the HT-29 cells was measured using MTT assay. Results The immunoliposomal Paclitaxel tagged with trastuzumab F(ab′)2 that was constructed in vitro had an average diameter of 210 nm, and that the diameters under 200 nm accounted for 91.37% of the total.The encapsulation efficiency and stability of the immunoliposomal Paclitaxel tagged with trastuzumab F(ab′)2 were perfect and the immunoliposome was superior to liposome at the identification capability to HT-29 cells in the same condition.Immunoliposomal Paclitaxel tagged with trastuzumab F(ab′)2 can kill the HT-29 cells in a time-dependent manner(P<0.01). Conclusion The immunoliposomal Paclitaxel tagged with trastuzumab F(ab′)2 was constructed successfully and it can kill the HT-29 cells effectively in vitro.