Development and Applications of Deoxyribonucleic Acid- and Threose Nucleic Acid -Based Materials

Abstract

Deoxyribonucleic acid (DNA), as the most important genetic material in living organisms, has wide applications in molecular imaging and disease therapy. Using the high reaction efficiency and detection specificity between the single strand and its complementary strand, DNA based biosensors have the potential to detect their complementary DNA or Ribonucleic acid (RNA) stands effectively. This thesis is structured into two main sections: the development of a DNA aptamer sensor for enrofloxacin detection and the creation of TNA-related materials for micro-RNA-155 (miRNA-155) detection and triple-negative breast cancer (TNBC) therapy.

In chapter 2, we focused on DNA aptamers, utilizing the Systematic Evolution of Ligands by Exponential Enrichment (SELEX) method to select single-stranded DNA with high binding affinity and specificity for its target. We developed a graphene oxide (GO)-based aptasensor featuring a 30-mer enrofloxacin-binding aptamer (Enro_ap3), which exhibited exceptional selectivity for enrofloxacin. This GO aptasensor effectively distinguished enrofloxacin from a variety of structurally diverse antibiotics, demonstrating robust, cost-effective, and rapid detection capabilities in marine environments.

In chapter 3, we developed a GO-TNA biosensor which was used to detect miRNA-155. This platform employed Cyanine 3(-Cy3) modified TNA capture probes attached to GO, allowing for precise detection and imaging of target nucleic acids both in vitro and in vivo. It was capable of distinguishing single nucleotide mismatches and monitoring dynamic changes in microRNA levels. This stable and reliable platform holds considerable promise for real-time disease diagnosis and the imaging of nucleic acid molecules within living organisms.

In Chapter 4, we introduced a novel antisense approach using TNA polymers to specifically target the Akt2 and Akt3 genes to cue TNBC. Two TNA strands, anti-Akt2 and anti-Akt3, were designed to target mRNAs with exceptional enzymatic resistance, high specificity, enhanced RNA binding affinity, and improved cellular uptake. In both two-dimensional (2D) and three-dimensional (3D) TNBC cell models, these TNAs effectively suppressed the expression of target mRNA and proteins, outperforming scrambled TNA controls. When combined with lipid nanoparticles in animal models, TNA treatment further reduced tumor size and promoted apoptosis by silencing Akt genes. These findings hold promise for the clinical development of TNBC therapies tailored towards improving patient outcomes.

In chapter 5, we design a TNADNA hybridization chain reaction biosensor (TDHDS) for rapid and ultrasensitive detection of exosomal miR‑21. The probe design integrates the biochemical stability and enhanced binding affinity of TNA with an enzymeless amplification strategy, enabling rapid fluorescence recovery upon target recognition. The TDHDS exhibited remarkable stability in serum-containing environments and completed detection within 15 minutes, significantly outperforming traditional probe systems. It achieved an ultralow detection limit of 0.39 pM and demonstrated high specificity, effectively distinguishing single-nucleotide mismatches from fully complementary targets. Moreover, TDHDS successfully identified elevated miR‑21 levels in lung cancer cell-derived exosomes, with results consistent with RT‑qPCR validation. Collectively, this work establishes TDHDS as a robust, biocompatible, and accurate biosensing platform, offering promising potential for non-invasive cancer diagnostics and real-time monitoring of disease progression.

Date of Award	19 Jan 2026
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Pik Kwan Peggy LO (Supervisor)