In order to obtain a lower-toxicity and higher-efficiency drug delivery system, we have focused on a multifunctional envelope-type nano device (MEND) for efficient delivery.For antitumor drug delivery of a MEND, PEGylation is a useful method that could achieve a longer systemic circulation and tumor accumulation via the enhanced permeability and retention (EPR) effect.A prerequisite for nanoparticle based drug delivery systems to be effective is that the drug payload is released at the target site.However, PEGylation inhibits cellular uptake and subsequent endosomal escape.To overcome this, we paid high interest and effort on enzyme-sensitive systems where overexpressed disease-associated enzymes are utilized to drug trigger-release.In order to enhance the tumor cell selective, we designed a opypeptide MCP that can be cleaved by the protease activity of matrix metalloproteinases (MMPs).We synthesized the sequence of MCP (GGGVPLSLYSGGGG) by using solid-phase synthesis method with a purity above 98%, which was detected by HPLC(Fig.1).When conjugated with PEG3000 and the amino group of dioleoylphosphatidylethanolamine (DOPE), TLC analysis showed that object product PEG3000-MCP-DOPE (PMD) had obtained (Fig.2,3).We prepared liposomes in different methods and incorporated PMD into liposomes (PMD-LS) at the same time.Characteristics of liposomes showed little difference in vesicle size, encapsulated efficiency and drug loading.Relatively speaking, however, PMD-LS prepared by film hydration can achieve a smaller polydispersity index than reverse evaporation method(Table 1).Our further studies will aim at achieving a higher uptake of PMD-LS in tumor cells as activated by secreted MMPs than in normal cell due to the steric hindrance effect.