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Artificial Golgi organelle

08/04/2009
Erin Podolak

The organelle prototype has succeeded in producing heparin, a widely used anticoagulant and blood thinner, in laboratory tests.

Scientists at Rensselaer Polytechnic Institute and the University of North Carolina, Chapel Hill have developed an artificial Golgi apparatus, the cellular structure that regulates hormones and enzymes to facilitate normal body functions. The artificial Golgi apparatus is composed of a network of sacs like natural Golgi apparatus and enzymatically modifies glycosaminoglycans, specifically heparin sulfate chains immobilized onto magnetic nanoparticles.

“We believe that the development of artificial organelles, such as the Golgi, will help us better understand organelles and how the natural Golgi is capable of controlling glycosylation, the most complex posttranslational modification of proteins,” said Robert Linhardt, professor at Rensselaer Polytechnic Institute

The team of researchers used digital microfluidics, recombinant enzyme technology, and magnetic naoparticles to create the functional prototype. Digital microfluidics uses open droplet movement that occurs through the process of electro-wetting on a 2D platform. Digital microfluidic chips consist of an array of electrodes covered by an insulator and then a hydrophobic layer. “This development will allow us to test the parameters that impact glycan structure and function,” said Linhardt.

The biosynthesis of heparin sulfate involves an array of glycosyl transferases, epimerase and sulfotransferases, which the team was able to mimic. Sulfo groups were transferred from adenosine 3′-phosphate and 5′-phosphosulfate to the 3-hydroxyl group of the D-glucosamine residue in an immobilized heparin sulfate chain, using D-glucosaminyl 3-O-sulfotransferase.

Currently humans treated with heparin receive the anticoagulant from animal sources. “We plan to use our artificial organelle to help us design a method to prepare a bioengineered heparin to replace animal-sourced heparin,” said Linhardt. According to Linhardt, contaminated heparin prepared from pig intestines caused the deaths of a number of Americans last year. “We believe that the time is right to separate the food chain from the drug chain and prepare heparin entirely in a controlled pharmaceutical manufacturing facility,” said Linhardt.

The method demonstrated by the researchers realistically shows the ability of scientists to study the effects of multi-enzyme systems on the structure of glycan products for heparin sulfate based studies. The researchers were prompted to create the artificial Golgi apparatus because it is impossible to obtain a full understanding of the control and regulation of heparin sulfate when studying the in vitro enzymatic synthesis, in the absence of a Golgi body.

The project, considered high-risk, was funded by the National Science Foundation. Research on the Golgi apparatus project will continue, looking at more complex devices capable of on-chip sampling and analysis, and multi-enzyme synthesis. The paper, “Toward an Artificial Golgi: Redesigning the Biological Activities of Heparan Sulfate on a Digital Microfluidic Chip” was published in the Journal of the American Chemical Society.

Keywords:  Golgi Heparin Research