PhD Oral Qualifying Examination : Precise functionalization of DNA on gold nanoclusters: Synthesis, Properties and Applications

Speaker Genji Srinivasulu Yuvasri (Supervisor: A/Prof Xie Jianping)

Host Department of Chemical and Biomolecular Engineering

Date/Time 09 Mar - 09 Mar, 10.00AM



Breast cancer being the second most common form of cancer reported worldwide with rough estimation of 2,68,670 new cases in United States in 2018 only, could be cured when diagnosed at its early stage. Nanomedicine serves to be an efficient alternative to conventional cancer treatments due to the well-studied material chemistry and technological advancements. Though many novel materials are designed for cancer diagnosis in-vitro and in-vivo, gold plays a much satisfying role due to its rich history-based data in treating dreadful diseases such as arthritis, HIV and cancer. Gold nanoparticles have been used in past decades for specific targeting and treating of cancerous cells, but the success rate been very low for its in-vivo applications due to its large hydrodynamic diameter with poor renal clearance and very limited bio-distribution attributing to its lack of interfacial control. To achieve in-depth structural understanding of nanomaterial with high interfacial control, thiolated DNA protected atomically precise gold nanoclusters Au25SR18 has been chosen as our model system due to its enriched physicochemical properties. Precise functionalization of DNA on the surface of gold nanoclusters are of high significance to enhance hybridization efficiency of DNA for better control on nanocluster crystallization and to avoid long standing protein corona issues for enhancing its specific targeting and therapeutic properties.

Preliminary work on ligand shell engineering has done to understand the gold-sulphur interface and to tune the ligand composition with high spatial control. To bring about ligand focusing, in-

situ functionalization (NaOH mediated NaBH4 reduction) protocol has been adopted and proposed that by differentiating the stability, tuning the chirality and using the steric property of the attached bi-ligands, the precise addressability of DNA onto the surface of bi-thiolate protected gold nanoclusters could be achieved. Initially, model ligands such as mercaptohexanoic acid (MHA) and cysteamine hydrochloride(Cystm) have been used to accomplish ligand focusing. From this preliminary work, could observe slight narrowing in the ligand composition range from (11-14) (7-4) to (13-14) (5-4). Fine tuning of the reaction conditions, such as the use of mild reducing agent, varying pH, temperature and aging cycle would ultimately lead us to find the pathway to precisely focus DNA on to the surface of bi-thiolate protected gold nanoclusters.