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Introduction
Cancer accounts for almost 10 million deaths annually and is the second most recurrent cause of mortality after cardiovascular disorders [1]. Despite the availability of various treatment modalities, one in six cancer patients succumb to it [2]. Poor treatment efficacy is the primary reason for such a high rate of mortality among cancer patients. Chemotherapy is the most frequently employed clinical approach in cancer, however, the lack of cell-specific drug targeting leads to a large number of unwanted toxic side effects and multi-drug resistance. This makes chemotherapy an inefficient treatment modality. Vomiting, nausea, alopecia, nephrotoxicity, cardiomyopathy and mucositis are some of the major side effects in patients undergoing cancer chemotherapy that affect their quality of life badly [1, 3]. The detrimental effect of cancer chemotherapy on the physical and mental health of the patient necessitates the development of an efficicacious drug delivery system with minimum toxic effects. The primary requisite for the novel anticancer drug delivery system includes cell-specific drug targeting, reduced side effects and drug resistance [3].
Smart nanoparticles are garnering significant interest in cancer drug delivery due to their capacity to selectively target specific cells and adapt to various treatment methods. They can be triggered or adjusted to react to particular stimuli, enabling precise, site-specific drug delivery. Additionally, these smart nanoparticles are also capable of co-delivering a drug along with a diagnostic agent resulting in the development of theranostics along with anti-cancer drug delivery [1]. Apart from this, smart nanoparticles have inherent advantages of nanoparticles like large surface area, prolonged circulation, controlled drug delivery and improved permeation across biological barriers [4]. Smart nanomaterials are capable of responding to different endogenous and exogenous stimuli like pH, temperature, magnetic field, electrical energy, enzymes, light, reactive oxygen species (ROS), tumour cell-specific factors etc. [3].
Amongst them, ROS-sensitive materials are being explored extensively for targeting cancer cells. ROS is a collective term used for a series of highly reactive and unstable molecules especially of molecular oxygen species, namely, superoxide anion (O2∙−), hydrogen peroxide (H2O2), singlet oxygen (1O2), hypochlorous acid (HOCl), nitric oxide (NO∙), thiol peroxyl radicals (RSOO∙), hydroxyl radical (∙OH). ROS are important mediators in physiological processes. Depending upon the site, level and nature,...