hUC-MSCs maintain their differentiation potential and efficiently express the eGFP reporter gene after nonviral and viral magselectofection. For nonviral magselectofection, we labeled 2.5 × 10⁶ hUC-MSCs using CD105 MicroBeads and magselectofected them with the magnetic lipoplexes SO-Mag2/DFGold/eGFP. Two days after magselectofection, the cells were stimulated using an osteogenic medium; and 18 days after stimulation, the cells were analyzed using alizarin red staining. (A) FACS data relating to the percentage of the eGFP⁺ cells at different time points after magselectofection. (B) Bright-field and fluorescence (490/509 nm) microscopy images of hUC-MSCs 7 days after magselectofection. Bar represents 500 μm. Objective Achroplan 4×/0.10 NA. (C) Microscopy images of the untreated (Untx) stimulated hUC-MSCs and the nonstimulated and stimulated hUC-MSCs 20 days after magselectofection. Bar represents 200 μm. Objective Achroplan 10×/0.25 NA Phl. For viral magselectofection, we labeled 10⁶ hUC-MSCs using CD105 MicroBeads and magselectofected them with the lentiviral magnetic complexes SOMag2/LV.eGFP. (D) FACS data relating to the percentage of eGFP⁺ hUC-MSCs versus the time after transduction (left graph) at different iron/lentivirus particle ratios in terms of fg Fe/VP with an MOI of 1 and (right graph) at a fixed Fe/VP ratio of 20 fg Fe/VP at different MOIs. (E) Fluorescence microscopy (490/509 nm) images of the hUC-MSCs 7 days after magselectofection with different MOIs at 20 fg Fe/VP. Objective Achroplan 10×/0.25 NA Phl. (F) Two days after magselectofection, the cells were stimulated using an osteogenic medium; and 18 days after stimulation, the cells were analyzed using alizarin red staining. Bright-field microscopy images of the magselectofected stimulated (differentiated) and nonstimulated hUC-MSCs 20 days after magselectofection with different MOIs at 20 fg Fe/VP. Objective Achroplan 4×/0.10 NA.