Hydrogels and nanogels based on 2Nap-capped cationic tripeptides: influence of lysine position and siRNA delivery properties.

The delivery of therapeutic short interfering RNA (siRNA) is hindered by biological barriers such as rapid degradation and poor cellular uptake. This study investigates peptide-based nanogels (NGs) as potential delivery platforms using three N-capped tripeptides, 2NapKFF, 2NapFKF, and 2NapFFK, designed to load siRNA via electrostatic interactions. The NGs were formulated through a "top-down approach" from pH-triggered hydrogels (HGs) and stabilized by surfactants. Biophysical characterization revealed that while all tripeptides achieved ∼99% siRNA encapsulation, the position of the lysine residue significantly influenced the stability and mechanical properties of the network. The 2NapFKF system emerged as the most suitable candidate, maintaining a size (∼200 nm) compatible with parenteral administration. Biological assays on Human Embryonic Kidney (HEK293) cells confirmed biocompatibility and cytoplasmic internalization through endocytic pathways. Furthermore, the treated cells maintained normal mitotic activity, indicating no impairment of cell proliferation. These findings demonstrate that lysine-modified tripeptide NGs are safe and effective tools for gene-silencing applications.