The atmospheric pressure glow discharge torch (APGD-t) is a miniature pulsed RF (13.56 MHz) plasma source specifically designed to efficiently produce and transport reactive species to and interact with biological samples. When applied to adherent cell cultures, the APGD-t is capable of inducing temporary cell permeabilization. In this work, we evaluate the maximum radius of macromolecules able to enter into HeLa cells following a plasma treatment using a size exclusion approach with dextran molecules. We observe that this maximum radius is below 6.5 nm. We also show that no degradation occurs when a plasmid DNA suspended in culture media is plasma-treated at the operating conditions leading to cell permeabilization. The plasma-assisted DNA transfection of the HeLa cells with the hrGFP-II-1 plasmid using the APGD-t is demonstrated. Local transfection efficiencies obtained are as high as 35%.