This study aims at developing biocompatible starch based gene carriers with good gene delivery and transfection efficacy. By controlling the molecular weight and aggregation behavior of spermine modified cationic starch (CS) molecules, nanocomplexes spontaneously formed through electrostatic interaction using CS and plasmid pAcGFP1-C1 (pDNA) displaying different structural changes (particle size, zeta potential, shape, compactness) response to the simulated intracellular pH variation. Results indicated that CS2 with weight average molecular weight (Mw) of 6.337 × 10⁴ g/mol displayed relatively higher transfection efficacy (~30%) in HepG2 cells than others and revealed significantly low cytotoxicity. By simulating the intracellular pH variation, Dynamic Light Scattering (DLS) and Small Angle X-ray Scattering (SAXS) results demonstrated that CS2 could bind to pDNA tightly and form nanocomplexes with smaller and compact internal aggregate structure at acidic conditions, which facilitated the effective pDNA protection under endosome pH change, while larger and loose internal aggregate structure at physiological pH which promoted the disintegration of CS2/pDNA nanocomplexes. Therefore, CS with suitable Mw of around 6.0 × 10⁴ g/mol represents a potential gene carrier for gene delivery. This study also demonstrated that controlling the internal nanostructure change of polymer/gene nanocomplexes could provide guidance in designing effective starch based gene carriers.

Background/Objectives: Chlorogenic acid (CGA), a potent antioxidant polyphenol, scavenges reactive oxygen species (ROS) and ameliorates oxidative stress-induced dermal extracellular matrix deterioration. However, its high hydrophilicity causes poor stratum corneum partitioning, insufficient dermal retention and low bioavailability. This study aimed to develop a surfactant-optimized, palmitoyl pentapeptide-4 (PP-4)-functionalized ethosomal system to enhance dermal retention and skin-protective efficacy of CGA. Methods: Binary nonionic surfactants were employed to optimize ethosome performance, followed by noncovalent PP-4 bilayer functionalization. Vesicle physicochemical properties and molecular interactions were characterized. Ex vivo skin permeation, cellular uptake, cytoprotection, intracellular ROS scavenging, and extracellular matrix-related gene expression were evaluated. Results: Surfactant-optimized ethosomes (CGA-ES, ~146 nm, −2.0 mV) exhibited higher encapsulation efficiency (92 ± 2%) and superior transdermal permeation versus surfactant-free vesicles. Subsequent PP-4 insertion reduced particle size to ~137 nm, reversed charge to +6.7 mV, and retained favorable encapsulation (83 ± 2%), forming mixed unilamellar–multilamellar structures. FTIR revealed the formation of hydrogen-bonded networks at phospholipid interfaces, underpinning superior colloidal uniformity and stability. The modified vesicles achieved enhanced total skin deposition and 1.2-fold higher dermis targeting efficiency compared with CGA-ES, along with improved cellular internalization, superior cytoprotection, and 2.4-fold stronger ROS scavenging under oxidative stress. The system effectively suppressed oxidative stress-induced upregulation of matrix metalloproteinase-1 and -3 (MMP-1/MMP-3) and restored type I collagen expression. Blank PP-4-modified ethosomes verified intrinsic peptide bioactivity, demonstrating complementary protection between CGA and PP-4. Conclusions: Binary-surfactant optimization enhances ethosomal colloidal performance and skin permeation. PP-4-mediated bilayer remodeling further promotes intradermal deposition. This dual-functional nanoplatform achieves combined skin-protective effects of CGA and surface-bound PP-4, providing a formulation basis for further in vivo evaluation and a potential strategy for topical delivery of hydrophilic polyphenols.