Multimodal nanoparticles (gold in polylactide) and their effect on three-dimensional cell cultures as organ models

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We will synthesise multimodal nanoparticles that can be tracked in the cell and detected in the endo-lysosome by specific fluorescence labels. This will be achieved by covalently binding fluorescently labelled biomolecules to small gold nanoparticles (diameter approx. 10 nm) where their fluorescence is quenched. These will be incorporated into polylactide-co-glycolide (PLGA) particles (estimation: approximately 10 gold nanoparticles within a single PLGA particle with a diameter of around 100 nm). The PLGA envelope will also be covalently functionalised with fluorescent dyes. The cellular uptake of the multimodal nanoparticles will be studied quantitatively using 3D cell culture models (crypt organoids and tumour spheroids) by in situ confocal laser scanning microscopy. We will focus on the pathway of the nanoparticles inside the complex cell network of the 3D cell culture or organoids and investigate the impact of the multimodal nanoparticles and biomolecules. Biomolecules for gene silencing (siRNA) will be conjugated to the gold nanoparticles to achieve a biological effect. First, the gene silencing of fluorescent eGFP as model protein will be investigated, followed by the gene silencing of important inflammatory disease mediators, such as TNF-α, KC, IP 10, and the apoptosis-inhibiting survivin as an additional protein model. The nanoparticle-mediated gene silencing of survivin will prove and extend our concept to another therapeutically relevant target.In summary, we aim for a better understanding of the biological effects of functional nanoparticles, covering inter alia the questions of dose, pathway, and fate. Three-dimensional cell culture models shall serve as bridge between "classical" two-dimensional cell cultures and animal models. We also want to achieve a quantitative validation of two-dimensional and three-dimensional cell culture models with respect to biologically active nanoparticles.