Carbon Nanotubes in Quercetin-Based Cancer Treatment: A Comprehensive Review

Cancer remains one of the leading causes of mortality worldwide despite substantial advances in diagnosis and therapeutic interventions. Conventional chemotherapy often suffers from poor selectivity, multidrug resistance, systemic toxicity, and inadequate bioavailability of anticancer agents. Nanotechnology has emerged as a promising strategy to overcome these limitations. Among various nanocarriers, carbon nanotubes (CNTs) possess unique physicochemical properties including high surface area, excellent cellular penetration, tunable functionalization capability, and remarkable drug-loading efficiency. Quercetin, a naturally occurring flavonoid widely distributed in fruits and vegetables, exhibits potent antioxidant, anti-inflammatory, antiproliferative, and pro-apoptotic activities against several cancers. However, its clinical application is limited due to poor aqueous solubility, rapid metabolism, low bioavailability, and instability. CNT-mediated drug delivery systems have shown considerable potential in enhancing the therapeutic efficacy of quercetin by improving solubility, targeted delivery, sustained release, and intracellular uptake. Functionalized CNTs conjugated with quercetin demonstrate enhanced cytotoxicity against various cancer cell lines including breast, lung, colon, prostate, and liver cancers. This review discusses the structure and properties of CNTs, pharmacological activities of quercetin, mechanisms of anticancer action, methods of CNT functionalization, quercetin-loaded CNT formulations, therapeutic applications, toxicity concerns, current challenges, and future perspectives in cancer treatment. The review highlights recent advances in CNT-based quercetin nanocarriers as a promising platform for targeted and effective cancer therapy.