Supramolecular Biomaterials

Supramolecular Biomaterials

The non-covalent association of molecules is a ubiquitous feature of life. Protein scaffolds, components of the extracellular matrix, and even duplexed nucleic acids all undergo supramolecular assembly. To generate synthetic self-assembled nanostructures, a wide variety of small molecule motifs have been developed that utilize hydrogen bonding, electrostatics, and hydrophobic interactions to contribute to the assembly process. Growing interest in the regulation of supramolecular assembly has produced a variety of responsiveness motifs. The governing effect of these motifs is exerted through physical and chemical cues such as ultrasound, temperature, pH, reduction and oxidation, and enzymatic responsiveness. Enzymes are ideal for the regulation of supramolecular interactions as they allow the mimicry of biological systems. They are catalytic in nature, able to be regulated by various biomolecules and ligands, and are biocompatible.

To create a responsive and tunable self-assembly system, we have developed Histidine Triad Nucleotide Binding Protein 1 (HINT1) responsive nucleoside phosphoramidate pro-gelators (PPGs). HINT1 has been well characterized as a nucleoside phosphoramidase and acyl-adenylate hydrolase. At PPG concentrations above the critical micelle concentration and below the gelation point, these molecules assemble into highly regular nanofibers resulting in bulk viscous liquid formation. Utilizing HINT1, the self-assembling peptides may be released from the blocking effect of nucleoside phosphoramidate moieties which induces the soluble nanofibers to condense into highly associated nanofiber bundles observed by electron microscopy. The structural transition to nanofiber crosslinking at the nanoscale results in bulk material gelation. We have utilized chemical biological tools in conjunction with small amplitude oscillatory rheometry to further characterize the role of HINT1 in the observed gelation event. Small molecule inhibitors and catalytically dead HINT1 mutants were used to investigate the role of HINT1 active site and catalytic activity on the regulation of PPG assembly. Inhibitors have been shown to block HINT1 activity on PPG substrates, and Hint1 H112N catalytically dead mutant has been shown to be unable to activate self-assembly. Our goal is to develop an adaptable system for the construction of biologically responsive materials that may be assembled in situ in response to HINT1 activity or by their own unique properties. Our hope is to apply these highly versatile materials to tissue engineering and drug delivery.

Key Accomplishments:

• Development of nucleoside phosphoramidate supramolecular nanofibers.

• Demonstration of HINT1 responsive hydrogels with nucleotide dependent morphologies.

• Demonstration that nucleoside phosphoramidate supramolecular nanofibers prepared with gemcitabine are able to kill cancer cells in in vitro.

• Defined and characterized the role of the nucleobase on nucleoside phosphoramidate supramolecular nanofiber assembly using physical and chemical studies.