Responsive Drug Delivery Based on Tumor Microenvironment

The limitations of chemotherapy in toxicity and patient compliance made the targeted and stimuli responsive drug delivery as the focal point in oncological research. This article reviews the responsive drug delivery systems that leverages the pathological characteristics or conditions of tumor microenvironment [TME] such as hypoxia, acidic pH, overexpressed enzymes, high levels of reactive oxygen species [ROS] and glutathione [GSH], to specifically release the drug and increase the accumulation of the drug at tumor site and reduce the unnecessary damage to healthy cells, thus decreasing the side effects. These physiological abnormalities act as triggers to release drug at required site. These drug delivery systems incorporate pH sensitive/responsive moieties, enzyme cleavable links, redox sensitive components allowing for precise control over when and where drugs are released, thereby minimizing damage to healthy tissue and increasing therapeutic efficacy. These intelligent systems have the potential to address issues with conventional treatment, such as off-target effects, systemic toxicity, low bioavailability, and drug resistance. As research evolves these technologies are likely to play a key role in future of cancer treatment. This review also presents brief idea of the TME and its salient characteristics, explains how TME-responsive moieties enable drug release, and briefly summarizes the basic ideas of targeted and stimuli-responsive delivery.