To investigate how these chemical structural differences affect polyplex assembly, we first assessed the morphologies of LPEI and BPEI polyplexes. Figure shows the TEM images for LPEI, BPEI, and DNA controls, as well as LPEI and BPEI polyplexes at an N/P ratio of 2. The images indicate that LPEI, BPEI, and DNA exhibit fibrous morphologies (Figure ). However, adding the PEI systems to DNA results in nanoparticles with spherical morphologies (Figure and), indicating the formation of polyplexes . Although both LPEI and BPEI form similar spherical structures, some distinct differences are observed. The images show that LPEI leads to polyplexes with less compact DNA structures, as indicated by the presence of free DNA on the periphery of the polyplexes (Figure , red arrow). In contrast, BPEI forms polyplexes with more compact DNA structures that are not exposed on the exterior of the particles (Figure ). Additionally, BPEI complexes exhibit significantly greater aggregation than LPEI complexes.