DHD-K12 cells expressing β-gal. DHD-K12 cells were transiently transfected with a plasmid vector expressing LacZ gene. Twenty-four hours after transfection, cells were checked for expression of β-gal through the development of blue colour. Cells expressing β-gal (mark with an arrow-head) ranged between 50% and 60% without significant cell death. The images (20x) was captured using Spot RT software version 3.0 (Diagnostic Instruments, inc) using a conventional inverted microscope.