Insulin is a hormone that controls blood glucose levels produced by the beta cells in the pancreas. As a medication, insulin was discovered by Frederick Banting and Charles Best in 1921, for which they were awarded a Nobel Prize in 1923. The insulin production process involves manipulating the biological precursor to insulin and cultivating it inside bacteria.
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The differences between animal-derived insulin and human insulin
Insulin injections are used for managing blood sugar levels in individuals who can’t naturally produce insulin. For many years insulin was derived from animals, mainly porcine or bovine pancreases, but the production of human insulin became a more popular alternative since its discovery in the 1980s. Manufacturing biosynthetic human insulin via gene technologies is a preferred method for not having to depend on animals as well as the possibility to produce unlimited amounts by multiplying the insulin gene inside bacteria.
Aside from production efficiency, as extracting large amounts from animal tissue is challenging, some issues with animal-derived insulin production are related to the raw animal tissues and diseases such as Bovine Spongiform Encephalopathy (BSE) and Transmissible Spongiform Encephalopathy (TSE) and possible cross-contamination through injections. Furthermore, the chemical differences between human and animal insulin can lead to antibody attacks, inactivation and inflammation.
However, a shortage of animal-sourced insulin in developed countries is a concern for a small number of individuals who experience severe hypoglycemic episodes when using biosynthetic insulin, and generally feel healthier when undergoing an animal-derived insulin treatment.
The steps and technology in recombinant insulin production processes
Recombinant DNA is a technology for the large-scale production of insulin by inserting the human gene which carries codes for the protein insulin into a plasmid of a simple bacteria, most commonly Escherichia coli. Producers then add ligase, an enzyme that acts like glue to help the plasmid stick to the bacterium’s DNA. The bacteria undergo a fermentation process inside a large fermentation tank, where millions of bacteria replicate every 20 minutes. The insulin harvest starts by adding a mixture of lysozyme which digests the outer layer of the cell wall and a detergent mixture which separates the fatty cell wall membrane.
The insulin is separated from the bacterium’s DNA with the help of a cyanogen bromide treatment which splits protein chains at the methionine residues. An oxidizing agent is added and the mixture is placed in a centrifuge to separate cell components. The DNA mixture is purified by using one of the following techniques: ion-exchange column, reverse-phase high-performance liquid chromatography or a gel filtration chromatography column. Finally, the purified substance is ready for medical use.
The future of insulin patents and treatment delivery
Although the use of insulin pens is practical due to their reusable nature, ability to increase patient compliance and accuracy, there are innovative solutions to enhance the delivery of insulin in the future. An alternative would be oral application, however, scientists are looking for ways to avoid enzymatic degradation upon consumption. Solutions can be found in nanoparticle-based approaches which protect insulin from gastrointestinal conditions and enhance the permeability of the enzyme.
A further option is the bioresponsive insulin delivery system, which accelerates insulin release with increasing glucose levels. Furthermore, manufacturers are working on the production of inhaled insulin devices, with insulin particles small enough to reach the deep lung and pass into the bloodstream. Another aerosol option is buccal insulin, a spray absorbed through the inner cheek wall. Finally, absorbing insulin through the skin with the help of insulin patches is another idea in development.
Transgenic plants as a solution for high demand
The insulin production process and its current manufacturing technologies struggle to keep up with the steadily increasing demand for affordable insulin due to a rising number of patients with diabetes. One of the most effective alternatives is the manufacture of recombinant human insulin from the plant Arabidopsis Thaliana and its oilseeds. Plant-based insulin is easy to produce, cost-effective, free from human pathogens and involves high-quality protein processing.
The oilseeds are genetically engineered with the recombinant protein targeting oil bodies and then processed by separating oil bodies via liquid-liquid phase to reduce chromatography steps in the purification of insulin. Transgenic plants can produce a high level of biologically active proinsulin and it can further be enzymatically treated in vitro which is an economic method for mass production.