iBodies: modular synthetic polymer antibodies

The introduction of monoclonal antibodies, specifically targeting biologically important proteins, revolutionized life sciences and subsequently clinical diagnostics as well as therapeutics. Nowadays, antibodies represent indispensable tools for researchers. Despite this extraordinary success, the use of antibodies involves also several disadvantages, such as difficult chemical modification, high production costs, and limited stability. To tackle these limitations, we set out to develop an alternative recognition tool capable of binding proteins of interest - polymer-based antibody mimetics (iBodies).
iBodies consist of a N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer decorated with different small ligands that function as targeting ligands, affinity anchors and imaging probes. As targeting ligands, specific enzyme inhibitors represent the perfect choice. As an affinity tag and imaging probe, we chose biotin and the fluorophore ATTO488, respectively (Fig. 1). We prepared specific iBodies targeting several biologically relevant proteins with known inhibitors, namely glutamate carboxypeptidase II (GCPII), HIV?1 protease, carbonic anhydrase IX, aspartic proteases, and His?tagged proteins. We successfully used iBodies for enzyme inhibition and subsequently also for protein isolation, quantification and immobilization as well as live cell imaging.
Since His-tag is the most widespread affinity tag used for protein purification, anti-His-tag iBodies is eminently suitable for a wide scientific community, as anti-His-tag antibodies are known to work quite poorly. iBodies developed against particular proteins of interest might become an alternative to antibodies used either in scientific research, or diagnostics and therapy.
The system is highly flexible and modular since in theory, virtually any compound can be added to satisfy user's needs and requirements. Importantly, to create new specific iBodies binding a particular protein, a simple replacement of the inhibitor is sufficient. Moreover, iBodies are all?rounders; one type of iBodies can be used in a number of biochemical applications. Finally, iBodies enable to target related group of proteins, such as paralogs, orthologs or families of enzymes, according to the specificity of the used targeting ligand.
To conclude, the iBodies platform can be used to produce inexpensive, stable and non?animal-based antibody substitutes directed virtually toward any protein of interest with a known ligand.