(600d) Designing Gels with Memory for Drug Delivery: Manipulating Transport and Binding Properties by Altering Structural and Reaction Parameters

Control of molecular scale events is leading to new and exciting developments in the field of biomaterial engineering and science. Macromolecular memory or template imprinting within polymer networks are due to two synergistic effects: (i) shape specific cavities that match the template molecule, which provide stabilization of the chemistry in a crosslinked matrix, and (ii) chemical groups oriented to form multiple non-covalent complexation points with the template. The enhancement in binding characteristics and delayed release properties of imprinted networks, observed in our work by altering reaction parameters, has been hypothesized to be due to improved structural homogeneity of the binding sites and a global energy minimum of the spatial arrangement of polymer chains. This work demonstrates the effect of template molecules that non-covalently interact with chain building monomers on the distribution of the resulting polymer chains and the subsequent binding and transport properties of the corresponding weakly crosslinked, imprinted gels.

Poly(methacrylic acid) homopolymers and poly(MAA-co-EGDMA) gels were created using conventional as well as living/controlled free-radical polymerization reactions. Multiple polymer chains and gels were created by varying the template concentration (template/functional monomer ratio) and the iniferter/conventional photoinitiator concentration. Template binding affinity and capacity were calculated via established binding isotherms while kinetic chain length distributions of the linear chains were studied using gel permeation chromatography. The results demonstrate a sharp increase followed by a gradual decrease in kinetic chain length of polymer chains with increasing template concentration. In addition, binding studies performed on the imprinted polymer networks yielded the imprinting efficiency of the polymer. The results confirm that improved structural homogeneity of template binding sites and a global energy minimum of the spatial arrangement of polymer chains lead to enhanced binding parameters and delayed template release. This work will lead to a new generation of tailorable drug delivery biomaterials which can be designed from the molecular scale to yield exquisite control over controlled release properties.