(A) Illustration of LNPs-mediated (−30)GFP-Cre protein delivery in 2D Transwell culture model. (B) The fluorescence images of the HeLa-DsRed cells seeded on the bottom of the chamber after (−30)GFP-Cre proteins alone or different LNP/GFP-Cre complexes were added into the upper chamber for 48 h. Scale bar: 200 μm. The cellular uptake (C) and DsRed expression level (D) of HeLa-DsRed cells seeded on the bottom of the chamber after (−30)GFP-Cre proteins alone or different LNP/GFP-Cre complexes were added into the upper chamber for 48 h **p < 0.01. (E) The TEER value change of the epithelial monolayer during the penetration of LNP/GFP-Cre complexes. (F) The CLSM images of immunostaining of the Transwell membrane after treated with different LNP/GFP-Cre complexes. (a) Control; (b) (−30)GFP-Cre proteins alone; LNP/GFP-Cre complexes treatment for 1 h (c), 6 h (d), 12 h (e), and 24 h (f), respectively. Red, cadherin; Blue, DAPI; Green, (−30)GFP-Cre proteins. Scale bar: 15 μm. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)