Stimuli-Responsive Carbon Nanotubes for On-Demand Cancer Therapy: A Review.

Stimuli-responsive carbon nanotubes (CNTs) have emerged as transformative nanocarriers in precision oncology due to their unique physicochemical, optical, and mechanical properties, enabling controlled, targeted drug delivery. This review presents a comprehensive analysis of CNT-based systems engineered to respond to specific internal (pH, redox, and enzymatic) and external (light, temperature, magnetic, and ultrasound) stimuli for on-demand cancer therapy. The discussion covers synthesis methods, structural differences between single- and multi-walled CNTs, and diverse functionalization strategies that enhance solubility, biocompatibility, and stimuli responsiveness. The crucial advances in CNT-based delivery systems demonstrate their ability to achieve spatiotemporal control over drug release, improve tumour penetration, and minimize systemic toxicity through mechanisms such as pH-triggered drug detachment, GSH-mediated redox cleavage, and NIR-induced photothermal ablation. Integrating CNTs with polymers, peptides, and metal nanoparticles further enables multimodal applications, including chemo-photothermal, chemo-immuno, and gene therapies. Despite remarkable progress, challenges remain in understanding long-term pharmacokinetics, immunogenicity, and biodistribution, as well as in establishing standardized synthesis and regulatory frameworks. The review highlights emerging trends such as AI-driven CNT design, predictive pharmacokinetic modelling, and personalized nanomedicine, emphasizing their potential to revolutionize cancer treatment by achieving precise, adaptive, and patient-specific therapy.