Development of Multifunctional Nanomaterials Based on DNA and Nanodiamond for Biomedical and Nanotechnological Applications

Abstract

In a recent decade, two revolutionizing nanomaterials, deoxyribonucleic acid (DNA) and nanodiamond (ND) have emerged as new and attractive candidates for the applications in material engineering and nanomedicine due to their remarkable properties. Specific self-recognition property of DNA stands and a very high photostability of ND are the powerful and unique chemical and physical features, which cannot be achieved from other materials. Hence, it is very valuable to explore their possible potentials in biomedicine and nanotechnology.

Self-assembled 3D DNA nanocage is constructed in which it is incorporated with double-tailed C18 lipid chain as a transfecting agent to enhance the cellular uptake efficiency and endosome escaping capability. This study revealed this hybrid system not only exhibited efficient cellular uptake via a temperature-, energy-, and clathrin- dependent endocytotic pathway as well as membrane diffusion, but also induced the mitochondrial targeting capability. Utilizing lipid-functionalized DNA nanocages (LNCs), V-carbazole and doxorubicin (Dox) loaded onto LNCs via different loading mechanisms were selectively delivered to and released in mitochondria after enzymatic degradation of LNCs. The mitochondrial-delivery of Dox induced significant cytotoxicity and cell death in MCF-7 cell compared with free Dox localized in lysosomes.

Additionally, a reversible molecular-switching of self-assembled 2D DNA nanostructure is also designed and built. A square-shaped DNA building block was designed and constructed with four G-rich overhangs (T₄G₄T₄G₄) which are used as toeholds. This study revealed the successful polymerization of self-assembled DNA nanosquares via the formation of the intermolecular G-quadruplex folded from G-rich linkers in presence of Na⁺ and K⁺ ions and a higher thermal stability compared to duplex linkers with the same lengths. Remarkably, the reversible property of these G-rich toeholds also allowed the manipulation of assembly and disassembly of the structures by sequential addition of monovalent cations and chelating agents.

Moreover, a photostable nanodiamond (ND) system functionalized with folic acids and mitochondrial localizing sequence peptides is also designed and constructed for selective targeting of cancer cells and localization in mitochondria. This dual-ligand-functionalized ND platform not only distinguishes the cancer cells with the overexpression of folate receptors on cell membrane and localizes into mitochondria, but also efficiently transports doxorubicin into the mitochondria and induces a significant apoptosis related cell death in drug-resistance human breast adenocarcinoma cancer cell (MCF-7/ADR) Furthermore, we also demonstrated the first example of a peptide-functionalized ND-based carrier for the delivery of genetic materials to the nucleus.

A stepwise ligand-induced self-assembly approach to integrate nanodiamond and gold nanoparticle (GNP) into a single nanoplatform is also presented. By utilizing the self-assembly property of the DNA linkage and the interaction between the biotin and streptavidin, GNPs and NDs were fabricated on magnetic bead (MB) solid support in a stepwise manner and then followed by a release of a dimer structure with a relative higher yield. Remarkably, this synthetic strategy can also be applied in fabrication of different combinations of homo/hetero nanoparticle dimers with regular/irregular shapes. Additionally, these ND-GNP dimers not only exhibit significant cellular uptake, but also possess excellent colloidal stability.

Date of Award	9 Jan 2019
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Pik Kwan Peggy LO (Supervisor)