Produced by Nature

PolyBatics scientists have discovered a property in nature that has been engineered to deliver solutions to many bioprocess, diagnostic and therapeutic applications. Using a polymer synthase found in a wide variety of bacteria, the company has developed a platform technology that allows for the high covalently bound display of proteins on the surface of biopolymer beads (biobeads). There are several features of this platform that enable unique applications.

Polymerization of Biopolyester (proposed model)

Self-assembly

The polyester synthase takes 3-hydroxyacyl-CoA from the cytosol and polymerizes it into ever longer chains. As the chains increase in size, their hydrophobicity increases and the polymer chains begin to self-assemble into polymer particles with the enzyme covalently attached to the surface. 

Adding fusion partners to the synthase allows the company to impart various functions to the beads. To date, proof-of-concept has been shown in a wide range of ligands being diaplayed as well as enzymes, antigens, signal proteins, antibodies and antibody fragments.  In some instances, the company has produced fusion proteins with multiple functions. Our expression systems have produced biobeads that display up to three separate functions on a single bead.

Stable bond

By far the most important aspcet of the technology is the ability to display these fusion proteins on the surface of the particles with a covalent bond. A thioester bond from a cystein residue provides a stable covalent bond that allow the functional proteins to be held onto the particle. Unlike traditional chemical immobilization methods this occurs in vivo and allows for easy separation of the particles. 

In this example the particle shows the thioester bond with the cystein residue. This particular particle displays the z-binding domain of protein A in addition to three gold bindng protein (GBP) domains. Also displayed on the same bead are the z-binding and  silica binding domains.

Payload delivery

Another feature of the technology is the ability to load the hydrophobic core with signal molecules or other lipophilic payloads.

In these images the same bacterium has been tramsformed to display GFP on the surface of the beads while the inside of the beads has been loaded with Nile Red, a hydrophobic fluorophore. As can be seen, the particles have taken up the Nile Red while retaining the fluoresence of the GFP. Cell activators or other cell binding proteins could allow for the targeted delivery of payloads to specific cells.