Abstract
α-L-Threose nucleic acid (TNA) is a nucleic acid analogue, which is constructed by replacing pentose into threose. Its chemical simplicity and capability to exchange genetic information with deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) suggested that TNA was a potential RNA ancestor. We investigated biological properties and evaluated potency of TNA oligonucleotides to suppress the gene expression in both in vitro and in vivo conditions. TNA oligonucleotides inhibiting the expressions of green fluorescence protein (GFP) or B-cell lymphoma 2 (BcL-2) gene were synthesized and introduced into various cell lines and mice. The results demonstrated that TNA was a good replacement as an antisense oligonucleotide. It exhibited strong affinity and specificity toward the complementary nucleic acids, were highly biocompatible and non-toxic in living cells and mice, and readily entered several cell lines without the requirement of transfecting agents. In addition, TNA exhibited much stronger enzymatic resistance in in vitro conditions, compared with traditional antisense oligonucleotides.Development of two-photon photocleavable molecules is emerging because the use of two-photon excitation light source is not harmful to biological systems. It is a longer wavelength light source with lower energy which would allow for deeper tissue penetration, less photodamage to the living cells/tissues and three-dimensional control with femtoliter resolution. There have been limited studies on the development of two-photon photocleavable linkers for light-triggered strand beaks in DNA oligonucleotides. (2,7-bis-{4-Nitro-8-[3-(2-propyl)styryl]}-9,9-bis-[1-(3,6-dioxaheptyl)]-fluorene (BNSF) and (4,4’-bis-{8-[4-nitro-3-(2-propyl)-styryl]}-3,3’-dimethoxybiphenyl (BNSMB) were two molecular structures exhibiting excellent two-photon uncaging efficiency at wavelength of 800 nm. We designed and synthesized two phosphoramidite building blocks based on BNSF and BNSMB structures. Some common molecular intermediates were designed and linked to the central biphenyl core of the two molecules, resulting in a versatile and cost-effective design. They can be effectively introduced to DNA oligonucleotides via the well-established standard cyanoethylphosphoramidite chemistry on a nucleic acid synthesizer. Photolysis of these BNSF- and BNSMB-incorporated DNA oligonucleotides was achieved by both one-photon and two-photon photolysis, resulting in two short pieces of single-stranded DNA oligonucleotides.
| Date of Award | 23 Mar 2021 |
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| Original language | English |
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| Supervisor | Pik Kwan Peggy LO (Supervisor) |