[A brief history of the development of realization on insulin]

The islet cells were found in 1869 and officially named "ilots de Langerhans" in 1893. The secretions of pancreas were found to contain ingredients to control blood sugar in 1890 which was named insulin in 1909. However, it was not until 1921 that insulin was purified, which was used to treat diabetes in 1922. American scholars obtained insulin crystals firstly in 1926. Since then, increasing knowledge were found in insulin, thus arousing a rapid development of its synthesis. Furthermore, Chinese scholars synthesized crystalline of bovine insulin firstly in 1965. Due to the presence of immunogenicity in animal insulin, Novo Nordisk used recombinant DNA technology to synthesize human insulin and for clinical use in 1980s. And Tonghua Dongbao Company developed the first recombinant human insulin of China in 1998. Meanwhile, insulin injections have also been changed from the ordinary syringes to dedicated insulin syringes, from the insulin pens to the insulin pumps, and eventually to the most advanced needleless syringes. Currently, academia is endeavored in the development of non-injectable insulin formulations.