Doxorubicin Loaded Polypeptide Self-assembly Aggregates Building And Research On In Vitro Anti-tumor Activity

Cancer alone with cardiovascular disease and diabetes mellitus has been three major killers to human health. Chemotherapy either alone or in combination with surgery or radiation remain the conventional treatment for tumor and tumor metastases. However, the naked drugs used in the clinic faces numerous difficulties and challenges, such as poor poor solubility in blood, rapid degradation by liver or clearance by renal, inability to achieve therapeutically effective drug concentration in tumor, severe side effects with the lack of selectivity and overwhelming toxicity further enhanced by the use of excipients and solvents, which limits the use in clinic a certain extent. One of the solutions is to encapsulate drug through nanocarriers. Nanocarriers possess good physical and chemical performance, sustained or controlled release character in vivo, protect the drug from degradation during its circulation, enhanced permeation and retention (EPR) effect and passive targeting to tumor.Polypeptide nano-assemblies amphiphiles increasingly attracted researchers’ interest among many materials for drug delivery vehicles. Generally, polypeptide amphiphiles was composed of hydrophilic poly (ethyleneglycol) (PEG) and hydrophobically derivatized polypeptide (PAA) blocks, it can spontaneously assemble in aqueous solution. Polypeptides synthesized with precise controlled polymerization have the similar characteristics to natural proteins, like favorable biocompatibility and biodegradability. Hydrophobic drugs are physical encapsulated into hydrophobic core or chemical covalently bounded to the polymer. In addition, researchers discover that charged components (DNA, plasmid or platinum II) could loaded into oppositely ionic block polymers via electrostatic interaction and it also self-assemble into core-shell nanostructures.Baesd on the above research, our lab investigated the use of novel anionic polypeptide methoxypolyethylene glycol-poly glutamic acid as the building blocks for forming nanocarriers. mPEG-PGA is a bottom-up synthetic biodegradable, and water soluble di-block copolymer. A unique feature of mPEG-PGA is its negatively charged pendant carboxyl moieties, which provide electrostatic or chelate interactions with positively charged drug molecules. Therefore, it is an ideal strategy for delivering positively charged anticancer drugs and the the drug loaded procedure using without organic solvent to ensure the safe for patients.Doxorubicin hydrochloride (DOX·HCl), is an anthracycline antitumor antibiotic, it works by intercalating DNA and commonly used in the treatment of a wide range of cancers. However, severe cardiotoxicity, myelosuppression, nephrotoxicity, and multidrug resistance caused by nacked DOX·HCl limit its therapeutic efficacy.DOX·HCl is a weak amphipathic base (pKa = 8.3), attributed entirely to primary amine group, which can be primarily exist as protonated or deprotonated. Thus DOX can exhibit either hydrophilic or hydrophobic properties by adjusting the environmental pH and show different charge.Herein, a drug delivery system is developed based anionic polypeptide-based block mPEG-PGA and cationic anticancer drug doxorubicin hydrochloride via electrostatic interaction and hydrophobic stack. mPEG-PGA block polypeptide was synthesized by ring opening polymerization, among, the major role of mPEG block to prolong circulation and PGA provided electrostatic interactions with the cationic drug DOX·HCl by pendant carboxyl groups. This ionomer complex mPEG-PGA-DOX spontaneously self-assembled into nanorods with an average size about 100～400 nm and zata potential -15.9 mV in aqueous solutions with a superior drug-loading content (50.8%) and a high loading efficiency (90.2%). In vitro release experiment indicated that DOX·HCl slowly released from the drug-loaded nanorods compared with nacked DOX·HCl solutions, and presented pH sensitive, the release rate was rapidly at acidic pH environment. In vitro cytotoxicity studies on human breast cancer cell line MCF-7 and human lung adenocarcinoma cell lineA549 suggested that mPEG-PGA-DOX have a super anti-tumor active compared with free DOX·HCl. Cellular uptake showed that mPEG-PGA-DOX uptake into MCF-7 and A549 cells easily. The drug loaded ionomer polypeptide complexs have an excellent uptake rate compared with free DOX. Hemolysis assays demonstrated that the synthetic block copolypeptide mPEG-PGA was hemocompatible. The presence of ionomer polypeptide complex mPEG-PGA-DOX could reduce the hemolysis ratio of DOX·HCl significantly. In vivo pharmacokinetics studies in wistar rats showed that mPEG-PGA-DOX nanorods exhibited excellent characteristic of drug sustained release. These features strongly supported the the interest of developing mPEG-PGA-DOX nanorods as great potential for cancer therapy.