Mild hyperthermia via gold nanoparticles and visible light irradiation for enhanced siRNA and ASO delivery in 2D and 3D tumour spheroids

The delivery of therapeutic nucleic acids, such as small interfering RNA (siRNA) and antisense oligonucleotides (ASO) into cells, is widely used in gene therapy. Gold nanoparticles (AuNPs) have proved to be effective in delivering silencing moieties with high efficacy. Moreover, AuNPs offer the possibility of spatial–temporal triggering of cell uptake through light irradiation due to their unique optical properties. Our study focuses on the use of AuNPs as improved vectorisation agents through mild photothermy triggered by visible light irradiation. This method promotes the transfection of oligonucleotides for gene silencing in 2D cells and more complex 3D spheroids. Improving gene silencing strategies in 3D cell cultures is crucial since it provides more effective in vitro models to study cellular responses that closely resemble the in vivo tumour microenvironment. We demonstrate the potential of mild photothermy by effectively silencing the GFP gene in 2D cell cultures: HCT116 and MCF-7. Then we showed that mild photothermy could be effectively used for silencing the c-MYC oncogene transcript, which is greatly overexpressed in cancer cells. A decrease of 25% and 30% in c-MYC expression was observed in HCT116 2D cells and 7-day 3D spheroids, respectively. In summary, our findings offer a novel transfection approach for gene therapy applications in 2D and 3D tumour models. This approach is based on the use of mild photothermy mediated by AuNPs combined with visible laser irradiation that might pave the way for the spatial–temporal control of gene modulation.