Carbon Nanotubes as Gene Delivery Vectors: Review Details Endosomal Escape Mechanisms and Intracellular Fate

Efficient and safe gene delivery remains a critical challenge for therapeutic applications, particularly for conditions requiring precise genetic modulation. While viral vectors offer high transduction efficiency, their immunogenicity and safety concerns limit broader clinical adoption. Non-viral gene delivery vectors, such as Carbon Nanotubes (CNTs), present a promising alternative due to their unique physicochemical properties, including high surface area and tunable surface chemistry. However, a major hurdle for these systems is overcoming endosomal sequestration, where delivered genetic material is trapped and degraded within cellular compartments, preventing its functional release into the cytoplasm.

This review synthesized the mechanistic understanding of Carbon Nanotube (CNT)-mediated gene delivery, focusing on the critical steps from cellular uptake to intracellular fate and functional outcomes. Researchers systematically analyzed existing literature to detail how CNTs enter cells, the various strategies employed for receptor-mediated targeting through surface functionalization, and the complex challenge of achieving endosomal escape. The review also compared the efficiency of CNTs against established non-viral vectors like lipid nanoparticles (LNPs) and polymeric vectors, and outlined a comprehensive immunotoxicological evaluation framework adapted from regulatory guidelines.

The review identified four primary endosomal escape mechanisms for CNTs: (1) direct cell membrane translocation, either intrinsically due to their needle-like geometry or facilitated by cell-penetrating peptides (CPPs); (2) the proton sponge effect, typically achieved through polyamine coatings that buffer endosomal pH, leading to osmotic swelling and rupture; and (3) photothermal/photochemical internalization, where light activation triggers endosomal disruption. The efficiency of these CNT-mediated escape strategies was compared against that of lipid nanoparticle (LNP) and polymeric vectors, highlighting their distinct advantages and limitations. > The review further elucidated the complex intracellular fate of CNTs, detailing how protein corona formation, complement pathway activation, and subsequent macrophage recognition influence their biodistribution and immune consequences. Intracellular fate trajectories were directly linked to functional therapeutic outcomes: lysosomal sequestration was found to govern silencing potency, tumor tissue pharmacokinetics determined knockdown duration, and CNS biopersistence correlated with sustained microglial activation. An immunotoxicological evaluation framework was outlined, encompassing complement split product quantification, PBMC cytokine profiling, inflammasome activation assays, and in vivo immunophenotyping.