Genetic engineering of innate and adaptive immune cells represents a potential solution to treat numerous immune-mediated pathologies. Current immune engineering methods to introduce nucleic acids into cells with high efficiency rely on physical mechanisms such as electroporation, viral vectors, or other chemical methods. Gene delivery using non-viral nanoparticles offers significant flexibility in biomaterial design to tune critical parameters such as nano-bio interactions, transfection efficiency, and toxicity profiles. However, their clinical utility has been limited due to complex synthetic procedures, high toxicity at increased polymer (nitrogen, N) to DNA ratios (phosphate, P) (N/P ratios), poor transfection efficiency and nanoparticle stability in the presence of serum, and short-term gene expression. Here, we describe the development of a simple, polymer-based non-viral gene delivery platform based on simple modifications of polyethylenimine (PEI) that displays potent and serum-independent transfection of innate and adaptive immune cells. Cationic acetylated PEI (Ac-PEI) was synthesized and complexed with plasmid DNA (pDNA) followed by enveloping with an anionic polyelectrolyte layer of poly(ethylene-alt-maleic acid) (PEMA) to form immunoplexes (IPs). Cellular interactions and gene expression could be precisely controlled in murine RAW 264.7 macrophages, murine DC2.4 dendritic cells, and human Jurkat T cells by altering the levels of PEMA envelopment, thus providing a strategy to engineer specific cell targeting into the IP platform. Optimally formulated IPs for immune cell transfection in the presence of serum utilized high N/P ratios to enable high stability, displayed reduced toxicity, high gene expression, and a lengthened duration of gene expression (>3 days) compared to non-enveloped controls. These results demonstrate the potential of engineered IPs to serve as simple, modular, targetable, and efficient non-viral gene delivery platform to efficiently alter gene expression within cells of the immune system.
Keywords: Gene delivery; Immune cells; Nanoparticle; Polyethylenimine; Serum independent.