The Transformation of Natural Products into Engineering Polymers & Functional Nanoscopic Objects

Karen L. Wooley
Texas A&M University
Thursday, March 6, 2014
Duke University, Schiciano B | 4:30pm

 

A primary interest in the Wooley laboratory is the production of functional polymers from renewable sources that are capable of reverting to those natural products once their purpose has been served. This presentation will highlight synthetic strategies for the development of polymer materials, which can be produced by relatively simple approaches from complex polyhydroxyl natural products and can be made to exhibit a range of properties, based upon the monomeric building blocks and carbonate or phosphoester linkages. Although Nature has several examples of engineering-type construction materials (e.g. cellulose, chitin, etc.) that are degradable, resorbable and recyclable, most synthetic materials are designed to be derived from renewable resources and degradable or from petrochemicals and perform as an engineering material. In one direction, polyhydroxyl natural products as the monomeric building blocks are combined with carbonates, found in common engineering materials, as the linkages. Hydrolytic degradation will produce the polyhydroxyl compound plus carbon dioxide. Four classes of natural monomers, D-glucose,1 quinic acid,2 ferulic acid and quercetin, are being evaluated for the construction of polycarbonates. The polyhydroxyl natural product monomers provide reactive hydroxyl groups for establishment of the polycarbonate backbones and their rigid cyclic core units together with the polar, hydrogen-bonding hydroxyl groups in the resulting polycarbonates are expected to lead to strong and tough materials for engineering, biomedical and other applications, where the combined properties and degradation potential can be utilized. In a second direction, phosphoester linkages are utilized, again borrowing from Nature, in the use of phosphoesters commonly found in biological macromolecules, such as DNA or RNA. Polyphosphoester-based block copolymers3 that can be produced rapidly and then undergo multiple chemical transformations and direct assembly in water into functional nanomaterials are serving as a platform for several directions toward their development as biomedical devices for the treatment of lung infections and osteosarcoma lung metastases. Block copolymers that are comprised of combinations of phosphoester and carbonate backbones have been observed to assemble supramolecularly in aqueous solution into micellar-type aggregates that exhibit LCST characteristics.4 If time allows, recent developments toward the preparation of functional polypeptides and their assemblies5 will also be described. Much of the work that will be discussed is unpublished, so that the most recent results will be highlighted. As this work is in progress, it is expected that the physical, mechanical, supramolecular assembly and stability properties will be tuned by the chemical compositions and structures, controlled by the advancement of synthetic methodologies by which to prepare such materials.

1 Mikami, K.; Lonnecker, A. T.; Gustafson, T. P.; Zinnel, N. F.; Pai, P.-J.; Russell, D. H.; Wooley, K. L. “Polycarbonates Derived from Glucose via an Organocatalytic Approach”, J. Am. Chem. Soc., 2013, 135(18), 6826- 6829.
2 Besset, C. J.; Lonnecker, A. T.; Streff, J. M.; Wooley, K. L. “Polycarbonates from the Polyhydroxy Natural Product Quinic Acid”, Biomacromolecules, 2011, 12(7), 2512-2517. 

3 (a) Zhang, S.; Zou, J.; Zhang, F.; Elsabahy, M.; Felder, S.; Zhu, J.; Pochan, D. J.; Wooley, K. L. “Rapid and versatile construction of diverse and functional nanostructures derived from a polyphosphoester-based biomimetic block copolymer system”, J. Am. Chem. Soc., 2012, 134(44), 18467-18474. (b) Elsabahy, M.; Zhang, S.; Zhang, F.; Deng, Z. J.; Lim, Y. H.; Wang, H.; Parsamian, P.; Hammond, P. T.; Wooley, K. L. “Surface Charges and Shell Crosslinks Each Play Significant Roles in Mediating Degradation, Biofouling, Cytotoxicity and Immunotoxicity for Polyphosphoester-based Nanoparticles”, Scientific Reports, 2013, 3 : 3313, 1-10. (c) Zou, J.; Zhang, F.; Zhang, S.; Pollack, S. F.; Elsabahy, M.; Fan, J.; Wooley, K. L. “Poly(ethylene oxide)-block-polyphosphoester-graft-paclitaxel Conjugates with Acid-labile Linkages as a pH-Sensitive and Functional Nanoscopic Platform for Paclitaxel Delivery”, Adv. Healthcare Mater., 2013, early view, DOI: 10.1002/adhm.201300235.

4 Gustafson, T. P.; Lonnecker, A. T.; Heo, G. S.; Zhang, S.; Dove, A. P.; Wooley, K. L. “Poly(ᴅ-glucose carbonate) Block Copolymers: A platform for natural product-based nanomaterials with solvothermatic characteristics”, Biomacromolecules, 2013, 14(9), 3346-3353.
5 Fan, J.; Zou, J.; He, X.; Zhang, F.; Zhang, S.; Raymond, J. E.; Wooley, K. L. “Tunable mechano-responsive organogels by ring-opening copolymerizations of N-carboxyanhydrides”, Chem. Sci., 2014, 5, 141-150.