Tailoring Guanosine Hydrogels for Various Applications

Abstract

Supramolecular hydrogels are of current interest for their ease of use, potential biocompatibility, and reactivity to stimuli. These gel materials have found use in a number of fields ranging from drug delivery and tissue engineering to sensing and environmental remediation. For over a century, guanosine (G 1) and its derivatives have been known to form hydrogels based on self-assembled G4-quartet structures. Recent research has focused on extending the lifetime stability of these hydrogels and modifying their properties to better suit the gels for applications in multiple fields. One such method involves the mixing of G 1 (or G-derivatives) with 0.5 eq of KB(OH)4, which results in the formation of guanosine-borate (GB) diesters. The GB-diesters self-assemble into G4-quartets stabilized by K+, the G4-quartets then stack to form wires that entangle to make a fibrous hydrogel network. This thesis details modifications of this GB-hydrogel system and explores applications of the resulting hydrogels.

Modification of the 5ʹ-OH group of G 1 to form 5ʹ-deoxy-5ʹ-iodoguanosine (5ʹ-IG 2) results in a hydrogel that self-destructs via intramolecular cyclization to 5ʹ-deoxy-N3,5ʹ-cycloguanosine (5ʹ-cG 3). Guanine analog drugs can be incorporated into this hydrogel network and then released upon self-destruction of the gel.

Substitution of boric acid with benzene-1,4-diboronic acid (BDBA 4) to form hydrogels with G 1 and K+ results in hydrogels that can be crosslinked with Mg2+. These G-BDBA-Mg hydrogels have a lower critical gelator concentration (cgc) than their non-crosslinked counterparts and can be used for cell growth applications.

Utilizing binary mixtures of 8-aminoguanosine (8AmG 5) with G 1 allows for the formation of hydrogels with various salts. Hydrogels made of different salts preferentially absorb either cationic or anionic dyes from water, making them candidates for use in environmental remediation.

Other 8-substituted G-analogs, including, 8-bromoguanosine (8BrG 6), 8-iodoguanosine (8IG 7), and 8-morpholinoguanosine (8morphG 8) can be used in binary mixtures with G 1 to form gels at room temperature upon mixing with KB(OH)4. Room temperature hydrogels have potential applications in enzyme immobilization, drug encapsulation, and environmental cleanup.