Surface-Capped Protein Nanoparticles for Nonviral Gene Delivery

Developing simple, safe, and efficient nonviral delivery systems remains a significant challenge in bioengineering. Nanoparticles offer promising gene delivery capabilities with reduced toxicity; however, long-standing challenges related to effective plasmid encapsulation and delivery exist. Here, we report a novel protein-based nanoparticle platform prepared by electrohydrodynamic jetting that features effective plasmid encapsulation and release. The protein, serum albumin, acts as the structural component of the nanoparticle and encapsulates the plasmid. To avoid chemical cross-linking, the protein-based nanoparticles are surface-capped via interfacial complexation with a polycationic polymer. Surface-capped protein nanoparticles (scPNPs) show excellent stability for 12 days at physiological pH values and have exceptionally high payload ratios of 10% to 40% wt/wt, corresponding to 28-99 plasmids per scPNP. The uptake efficiency of scPNPs exceeds 95% and engages macropinocytosis and clathrin-mediated endocytosis pathways. When optimizing nonviral gene therapies, either the payload or the nanoparticle dosage can be varied. For scPNPs, increasing the nanoparticle dosage is more effective than increasing the payload, resulting in a 1.6-fold increase in transfection rate for identical plasmid amounts. To demonstrate their translational potential, scPNPs were used to effectively encapsulate messenger RNA (mRNA) and transfect primary human T cells, while maintaining high cell viability. This work both advances the fundamental understanding of design choices when optimizing nanoparticle-based gene delivery and demonstrates the potential of scPNPs for cell therapies.