Non-viral intracellular platform for cell therapy applications

Biological molecules, including DNA, proteins and peptides can act as therapeutic agents. When efficiently delivered to cells, they have the potential to modify cell behaviour. The successful delivery of these molecules to cells can be used as a basis for cell therapies, whereby the modified cells are introduced into patients to treat disease. However, inefficient delivery to the cytosol, often cause by the degradation of lysosomes after entering the endocytic pathway, has hampered progress in this area. Existing technologies to improve delivery, namely viral vectors, have led to increased cell toxicity and safety concerns surrounding their use. Thus, there is a need for an effective non-viral intracellular delivery platform. pH-responsive polymers mimic the highly efficient intracellular delivery mechanism of viruses. By triggering endosomal membrane disruption at acidic pH's, the payload is released into the cytosol, increasing intracellular delivery efficiency. PLP-NDA is a Poly (L-lysine isophthalamide) derived polymer, synthesised and developed in the Chen group, that exhibits pH-responsive and membrane disruptive behaviour. This project aims to use PLP-NDA as a non-viral intracellular delivery platform for cell therapy applications. The objective is to use a simple delivery method by which the cells of interest are co-incubated with the target payload and polymer to facilitate delivery. In this report, PLP-NDA was synthesised and its pH-responsive membrane destabilising activity assessed using haemolysis. Intracellular uptake was evaluated through flow cytometry studies using FITC-dextran as a model payload. PLP-NDA displayed limited haemolysis at pH 7.4 but increased membrane destabilising activity with a decrease in pH, reaching its maximum haemolytic potential at endosomal pH. Further, PLP-NDA improved the intracellular delivery of FITC-dextran compared to when treated in the absence of polymer. Whilst further investigation is still required to understand the full capabilities of PLP-NDA as an intracellular delivery platform, the results highlight that PLP-NDA has great potential to be used for cell therapy applications.