Nikou Rahbari Asr

Topic

The Role of Interactions between Cucurbit[7]uril and Small Molecules in the Sodium Deoxycholate Hydrogel

Department of Chemistry

Date & location

• Thursday, September 19, 2024
• 2:00 P.M.
• Elliott Building, Room 305

Examining Committee

Supervisory Committee

• Dr. Cornelia Bohne, Department of Chemistry, University of Victoria (Supervisor)
• Dr. David Leitch, Department of Chemistry, UVic (Member)
• Dr. Stephanie Willerth, Department of Mechanical Engineering, UVic (Outside Member)

External Examiner

• Dr. Alexandre Brolo, Department of Chemistry, UVic

Chair of Oral Examination

• Dr. Patrick von Aderkas, Department of Biology, UVic

Abstract

The structure of bile salts has hydrophilic (hydroxyl groups) and hydrophobic (alkyl groups) regions, resulting in amphiphilic properties. Bile salts can form aggregates and these aggregates can act as supramolecular hosts for small molecules and encapsulate guest molecules within their structure. Unlike other bile salts, sodium deoxycholate (NaDC), can form supramolecular hydrogels through molecular self-assembly processes by adjusting the pH to around neutral and controlling the temperature.

The aim of this work, was to investigate how cucurbit[7]uril (CB[7]), affects the properties of NaDC hydrogel. Cucurbit[n]urils (CB[n]s) are a family of macrocyclic molecules characterized by their pumpkin-shaped structure and a symmetrical hydrophobic cavity. By studying the interactions of CB[7] in NaDC hydrogels, the aim was to understand the potential role of CB[7] in modifying the hydrogel's properties and to determine if CB[7] can serve as a carrier for guest molecules from the NaDC hydrogel to the surrounding medium. To gain a better understanding of the effect of CB[7] and its localization within the NaDC gel, two projects were developed.

The objective of the first project was to study how the presence of NaDC aggregates affects the binding dynamics of berberine, a natural isoquinoline alkaloid fluorophore, with the host CB[7] in the presence of mobile aggregates of the NaDC. The presence of NaDC aggregates creates a more heterogeneous environment for the host-guest interactions, potentially affecting the dissociation of berberine from CB[7]. The results showed that the addition of NaDC aggregates changed the distribution of berberine, causing berberine to bind to both CB[7] and NaDC aggregates. The results also revealed that the addition of NaDC aggregates to the berberine@CB[7] complex accelerated the apparent dissociation rate constant of berberine from CB[7].

The objective of the second project was to understand how the presence of CB[7] affects the structure of the NaDC hydrogel and the release of a small molecule from the hydrogel into the surrounding medium, and how this effect differs from the effect of cucurbit[6]uril (CB[6]). To study these effects, I studied the hydrogel's structure using berberine, a hydrophobic and positively charged guest, and rhodamine 6G, a hydrophilic and positively charged dye. The release of rhodamine 6G from the NaDC hydrogel into the surrounding medium was also studied in the presence of CB[7] and CB[6]. The results showed that the presence of CB[7] in the NaDC hydrogel caused the transformation of the spherical aggregates into elongated structures, whereas CB[6] led to the formation of fibrous structures, as observed in previous research conducted by our group. Also, the release profile of rhodamine 6G from the NaDC hydrogel was not significantly affected by the addition of either CB[6] or CB[7].