PHYTOGLYCOGEN and animal glycogen are highly branched glucose polymers that function as energy storage mediums in plant and animal cells and are similar in structural features and molecular size range. These polysaccharides are composed of α-1,4-glucans, highly branched via α-1,6-glucosidic linkages. Glycogen is present in animal tissue (mainly in the liver) in the form of dense particles with diameters of 20 – 200 nm and has also been found to accumulate in microorganisms, e.g., bacteria and yeasts. An abundant source for phytoglycogen is the kernel of mutant corn (su-1), a primary genotype of commercial sweet corn. Starch branching and debranching enzymes lead to the formation of granules during biosynthesis of starch. The su-1 mutation causes the deficiency of the su-1 enzyme, which is similar to iso-amylase and debranches starch (DBE). The primary role of DBE is to trim irregular branches that inhibit the formation of starch crystals and granules. The absence of DBE leads to the formation of highly branched phytoglycogen.
Glycogen and phytoglycogen are normally considered “highly polydisperse” or heterogeneous materials. Commonly reported glycogen or phytoglycogen particle diameters are in the range of 20 – 300 nm and have either continuous or multimodal size distribution. Small, 20 – 30 nm in diameter, particles are termed β-particles and large, 100 – 300 nm in diameter, α-particles. The α-particles are considered to be composed of β-particles as a result of aggregation or clustering. Phytoglycogen is similar to animal glycogen – both for the range of molecular size distribution and the presence of α-particles.
Various methods have been developed to isolate glycogen and phytoglycogen from living organisms. Most often, the purpose was to quantify the amount of total glycogen accumulated in biological samples and, infrequently, for the purpose of using the glycogen as a product in applications. A proprietary extraction process of phytoglycogen from sweet corn is the basis for the highly purified monodisperse NanoGlys™ material.
Phytoglycogen can be easily modified with standard chemical methods. This allows for functionalizing the surface of nano-particles or for attaching active pharmaceutical ingredients (APIs), chromophores and markers to the nano-particle. The properties of the nano-material can be optimized for the specific biological environment or clinical indication.