To overcome the cardiotoxicity of doxorubicin, a self-assembled pH/enzyme-responsive system was developed. Cationic gelatin combined polyGC-DOX intercalation tightly to form compact nanoscale complexes (CPX1) which then combined by a pH-sensitive pegylated alginate to form CPX2. CPX2 could be digested and release DOX under the co-digestion of gelatinase (GA) and Dnase I when pH < 6.9. More importantly, tumor homogenate supernatant (THS) could effectively release DOX from CPX2 while the plasma and liver homogenate supernatant (LHS) could not, which was confirmed by an in vivo test. The results indicated that this formulation had the tumor-specific drug-release effect. This effect resulted in an increased drug concentration in tumor tissue and decreased content in heart and liver. The changed bio-distribution of DOX delivered by CPX2 greatly enhanced the anti-cancer activity and reduced the cardiotoxicity of the drug. The anti-cancer efficiency of DOX delivered by CPX2 is more than 2 times of the free doxorubicin, and the mortality caused by the high-dose DOX was completely prevented by CPX2. All results suggested that this easy-manufactured, cost-effective nanocomplex holds great promise to be developed into a formulation of doxorubicin and the other anthracyclines with high anti-cancer activity and low cardiotoxicity.
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