Localised On-Demand Delivery of Nucleic Acid Therapeutics

The body naturally orchestrates response to injuries by producing a variety of bioactive cues at precisely coordinated times. However, when this response is hindered –as it is in many diseased states –this results in a lack of healing. Localised on-demand delivery of therapeutic cues that mimic natural signalling profiles can help overcome this and can be achieved by encapsulation of therapeutics in ultrasound-responsive biomaterials. Moreover, housing this delivery system within a regenerative template can further enhance efficacy. This thesis demonstrates the development of a pocketed collagen-based scaffold for the on-demand release of therapeutic nucleic acid-based nanoparticles from alginate hydrogels by application of ultrasound. As multiple therapeutics can be sequentially delivered, this platform can be adapted for applications requiring multi-stage treatments such as osteosarcoma, breast cancer bone metastasis and diabetic foot ulcers. PEI-pdna nanoparticles (for regeneration) and DNA origami nanostructures (cancer treatment), were encapsulated in ionically crosslinked hydrogels and released on-demand with ultrasound (Chapter 2). A mathematical model was developed to simulate the release of PEI-pdnananoparticles, DNA origami nanostructures and mitoxantrone (chemotherapeutic) from alginate hydrogels (Chapter 3), and it was employed to evaluate processes governing drug/hydrogel mass transport and to simulate various ultrasound regimens. Ultrasound-released DNA origami nanostructures, functionalized with doxorubicin, exhibited a therapeutic effect against breast cancer cells (Chapter 4), while the nanostructures remained structurally stable in cell culture media for 4 days. PEI-pdna ultrasound-released nanoparticles remained bioactive and transfected cells; however, protein levels were very low (Chapter 5). Investigations into the effects of the hydrogels on the polyplexes revealed de-stabilization of the PEI-pdna nanoparticles. In Chapter 6, on-demand release of Horse nanostructures from injectable alginate hydrogels embedded in pocketed scaffolds was achieved, and released structures maintained their bioactivity. This work demonstrated the development of a regenerative platform capable of releasing bioactive therapeutic nanoparticles on-demand by application of ultrasound.