Advantages of Calcitonin complexed with SA liposome

Polypeptide drugs interact with target cells, but there are concomitant side effects and toxicity to normal cells. Consequently, their applications and dosage usually have to be limited. Clinical application of peptide drugs must meet the requirements at low toxicity, potency enhancement and dosage reduction. Liposome is a successful example of Various carrier systems that are used to lower toxicity, enhance potency and prolong half-lives [1]. Drugs encapsulated in liposomes have been applied for treatment and substantial effects have been observed, e.g. lower toxicity or side-effects. In the present study, SA liposome was used to improve the effect of peptide drugs in vivo. Favorable results were obtained, such as resist once to degradation, higher halflife, and better absorption. Cationic liposome is one kind of liposome with a positively charged surface. Peptide drugs can interact with cationic liposomes by been encapsulated inside the liposome. The positive charges on the surface of cationic liposomes can affect static electricity absorption with the negative charged segment of polypeptide drugs. Also, the hydrophobic polypeptide residue can insert into the lipid bilayer. Compared to normal liposomes, cationic liposome as a drug carrier, has the advantage of stronger affinity with the negatively charged cell surface, thus facilitating drug absorption. The SA liposome, which we invented, contains stearylmine and DOPE, both of which are naturally occurring lipids, and has low immunogenicity and high stability [2]. Calcitonin, an important peptide hormone secreted by thyroid gland C cells, regulates calcium metabolism and skeletal metabolism in vivo [3]. Due to its conspicuous biological activity which can be measured sensitively, and its stability, we selected sCT (salmon calcitonin) and two kinds of hCT (human calcitonin) analogues as peptide model to study the interaction with SA liposome.