(364a) Selective Recognition of Angiotensin II

The overexpression of several peptides and proteins in the body often lead to catastrophic physiological conditions. Ultimately it would be beneficial to be able to reduce the circulation of these peptides. One possible method of achieving this is by creating systems that use synthetic biomaterials to mimic natural biological recognition processes. By using synthetic biomaterials, one can design the next generation of materials for therapeutic and diagnostic devices by overcoming barriers posed by natural macromolecules and ligands, which are expensive and relatively unstable. These recognitive polymer systems can be fabricated with molecular architectures possessing specific chemical moieties that provide a framework for selective recognition of a target analyte in aqueous environments. A particular peptide that would benefit from a system such as this is angiotensin II. This is an octapeptide hormone which has been implicated in arterial fibrosis when present in increased levels. This paper reports on a novel recognitive system that uses synthetic biomaterials in order to recognize and capture the undesirable anaylte. Our method uses configurational biomimesis which produces polymeric surfaces or polymeric recognitive networks that have three dimensional, stereospecific binding micro- and nanocavities based on the given template molecule angiotensin II. To achieve destruction of the overexpressed peptide for further therapeutic effects, we have incorporated biodegradable components into the polymer backbone which creates an acidic microenvironment upon hydrolytic cleavage at ester bonds. This microenvironment will therefore create suitable conditions to destroy the peptide.

Imprinted polymer networks were prepared by fast, UV-initiated, free radical polymerization reactions of acrylamide (Sigma-Aldrich) as the functional monomer, poly(ethylene glycol) dimethacrylate (Sigma-Aldrich) as the crosslinking agent, and angiotensin II as the template molecule. To determine the integrity of the three dimensional binding cavities, dynamic swelling studies were performed with polymer disks under physiological conditions of 37°C and pH of 7. To analyze the effectiveness of the imprinting process, recognitive/binding studies using angiotensin II and its derivative SVAangiotensin, were conducted by HPLC. In order to optimize the repeated recognition (rebinding) of angiotensin II, the molar ratio of template to functional monomer was varied. The various ratios experimented with were 1:8, 1:16 and 1:32. The cross-linking ratio was also varied from 10% to 80%. The polymer networks were then analyzed by scanning electron microscopy. The angiotensin II was then placed in various acid compositions and analyzed by electron spray ionization (ESI) mass spectroscopy in order to determine its integrity in the presence of an acidic microenvironment.

The recognition studies showed that the networks imprinted for angiotensin II were more selective and recognized angiotensin II more effectively than the non-imprinted polymers. In a competitive binding study, the imprinted networks were also more selective for angiotensin II than its derivative peptide SVA angiotensin.

It can also be seen from studies that the peptide angiotensin II can be degraded in the presence of glycolic acid. ESI mass spectroscopy compares pure angiotensin II with angiotensin II that has been incubated for 24 hours in glycolic acid. It shows that the pure 1046 peak is almost completely gone after the incubation.

The recognitive systems that have been developed show higher selectivity towards angiotensin II than other derivative peptides. We have also shown that angiotensin II can be destroyed when glycolic acid is present, and we believe this can ultimately have a therapeutic effect. The synergistic effect of the recognition, capturing and destruction of the peptide ultimately offers promise for novel drug delivery systems.

Supported by a grant from the National Science Foundation and by the UT NSF/IGERT Program