Observing morphological characteristics in mature neurons of adult OTBS. A) Confocal image of neighbouring pyramidal cells, which were treated with the 40 nm particles, shows long axons oriented towards the cortex as seen by EYFP expression at 5 days post transfection. Scale bar: 25 μm. B) Another confocal image showing a population of pyramidal cells having their soma present in the CA1 region of the brain 5 days following EYFP transfection with the 40 nm particles. The radiating arborescence of neurites formed within the adult brain can clearly be seen. Cells were also stained with DAPI. Scale bar: 10 μm. C) Confocal image of another pyramidal cell 5 days following transfection with 40 nm particles showing EYFP expression. The soma also rests within the densely populated CA1 region of the hippocampus while the neurites branch out towards their respective synaptic interfaces. Cells were also stained with DAPI. Scale bar: 10 μm. This transfection procedure adequately preserves the morphological characteristics and architecture of mature neurons within these ex vivo adult OTBS.