Utility of photoacoustic imaging, an advanced drug delivery approach and drug discovery for corneal neovascularisation diagnosis and treatment

Abstract

The ever-evolving photoacoustic imaging (PAI) technique and nanotechnology have shown tremendous opportunities for improving various biomedical applications such as cancer diagnosis, molecular imaging, and advanced drug delivery strategy. The utilisation of these techniques drives the biomedical field into the next era by providing precise diagnosis and drug delivery strategies in different biomedical applications. This thesis aims to address and tackle issues associated with corneal neovascularisation (CNV) using PAI and nanotechnology to provide objective analysis and enhance ocular drug absorption. Furthermore, a newly developed focal adhesion kinase (FAK) inhibitor was investigated for its feasibility as a CNV treatment. This serves as a first attempt to lay a foundation for its future application in ocular disease treatment. In chapter three, the PAI technique was applied with in vivo alkali-induced CNV model to examine its potential in identifying and quantifying haemoglobin species within the diseased cornea. In vivo results demonstrated that the PAI could identify and quantify haemoglobin species based on their corresponding wavelengths. Furthermore, the PA signal quantification revealed an increase across different PA signal parameters, which matches the severity observed in the slit-lamp examination. Thus, this offers an objective and quantitative approach for future ocular disease examination. Furthermore, this study also demonstrated the feasibility of employing metformin eye drops to combat CNV. Conventional ocular drug delivery approaches often suffer from poor bioavailability due to the natural ocular barrier, which hampers the treatment outcome. In particular, hydrophobic drugs have difficulty penetrating the cornea through topical administration and exert their medicinal effect. The emergence of a polymeric nanoparticle drug delivery system is a potential solution to this problem. In chapter four, we developed a polymeric nanocarrier conjugated with cell-penetrating peptides for enhanced ocular drug delivery. The system employed a hydrophobic drug as a model drug while the surface of the nanoparticle was modified with octa-arginine (R8) peptide. The optimized nanocarrier showed an overall negative charge (-6.55 ± 0.94 mV) with size of 185.2 ± 4.45 nm. In vitro analysis revealed the nanocarrier possessed sustained-release property while enhanced absorption was observed with confocal microscopy. Furthermore, the cell-penetrating peptide assisted in the penetration of the nanocarrier to human umbilical vein endothelial cells (HUVECs) after incubation. Benefitting from these properties, in vivo experiments with the nanocarrier, showed outstanding treatment performance compared to control groups. Overall, the data presented in this work demonstrated the potential of surface-decorated nanocarrier in the ocular drug delivery aspect. In chapter five, the efficacy of a newly developed focal adhesion kinase (FAK) inhibitor (KX2-4245) was investigated in the CNV model. Disruption of anti-angiogenic and pro-angiogenic factors in the cornea leads to the sprouting of blood vessels, resulting in CNV formation. Several angiogenic contributors, such as VEGF and FAK, have previously been identified. In this work, an MTT assay was conducted to probe the cell viability after KX2-4245 treatment. Quantitative analysis revealed that no cytotoxicity could be observed at a concentration of 2 nM or below. Furthermore, the KX2-4245 showed an anti-angiogenic effect in the experimental CNV model and is well-tolerated through topical administration. The data presented in this work lays a foundation for its future utility in treating ocular diseases associated with angiogenesis. Overall, these findings provide a solution to tackle existing problems associated with ocular imaging and administration methods.