Stimuli-Responsive Hydrogels for Cancer Treatment: The Role of pH, Light, Ionic Strength and Magnetic Field

SIMPLE SUMMARY: Cancer remains as the world second leading cause of death. The severe side effects associated to high doses of chemotherapy and the development of drug resistance are major drawbacks for a successful cancer treatment. Therefore, new formulations that promote localized therapy at tumor sites are needed to improve the therapeutic outcomes and patient welfare. The use of hydrogels is a very promising alternative, since they can be composed by smart materials able to respond to external factors, changing their properties accordingly and promoting a localized drug delivery. As a result, a more specific, efficient, and less toxic local cancer treatment can be accomplished. In this context, the most important characteristics of hydrogels recent studies regarding the application of pH-, light-, ionic strength-, and magnetic-responsive hydrogels in cancer treatment are here presented. ABSTRACT: Cancer remains as the second leading cause of death, worldwide. Despite the enormous important advances observed in the last decades, advanced stages of the disease remain incurable. The severe side effects associated to systemic high doses of chemotherapy and the development of drug resistance impairs a safe and efficiency anticancer therapy. Therefore, new formulations are continuously under research and development to improve anticancer drugs therapeutic index through localized delivery at tumor sites. Among a wide range of possibilities, hydrogels have recently gained special attention due to their potential to allow in situ sustained and controlled anticancer drug release. In particular, stimuli-responsive hydrogels which are able to change their physical state from liquid to gel accordingly to external factors such as temperature, pH, light, ionic strength, and magnetic field, among others. Some of these formulations presented promising results for the localized control and treatment of cancer. The present work aims to discuss the main properties and application of stimuli-responsive hydrogels in cancer treatment and summarize the most important advances observed in the last decades focusing on the use of pH-, light-, ionic strength-, and magnetic-responsive hydrogels.