Quantification of intracellular vector genome detection. (A) Electron micrograph of control non-transduced cells showing minimal background signal. (B) DNA hybridization signals from 4 independent cell population infections were counted and represented as total nuclear over cytoplasmic signal ratio. All cell areas containing DNA hybridization signal were systematically photographed (about 150–200 photos) and signal was carefully quantified, each time with equal surface of nuclear and cytoplasmic compartments. The p value (Mann-Whitney test) shows the results are highly statistically relevant.