Increased block copolymer length improves intracellular availability of protein cargo

Amphiphilic protein transduction domain mimics (PTDMs) ranging from 15 to 120 repeat units in length were studied for their abilities to non-covalently bind and deliver proteins into Jurkat T cells. While shorter PTDMs facilitated greater EGFP and IgG internalization, longer block copolymers promoted heightened activity of Cre recombinase post-delivery, editing up to 60% of cells. Higher cargo activity devoid of higher cellular internalization implies that longer PTDMs improve the intracellular availability (IA) of the cargo, that is, the fraction of native protein successfully delivered and released at the target site. Dynamic light scattering of PTDM : IgG complexes revealed that increasing the carrier to cargo ratio yielded progressively larger aggregates with the shortest PTDM (up to ∼1 μm), but no change in complex size with the longest amphiphile (∼50 nm). Thus, employing longer PTDMs for protein delivery may be a useful tool for stabilizing non-covalent complex size, particularly given that smaller nanoparticles correlated with enhanced cargo activity.