Application of nanogels as drug delivery systems in multicellular spheroid tumor model

Nanogels have piqued the interest of researchers as nanoscopic drug delivery systems, especially for site-specific or time-controlled delivery of therapeutic mediators. A wide range of polymer systems and the fundamental alteration of their physicochemical properties have resulted in multipurpose nanogel formulations. Nanogels have high longevity, drug-loading capability, biologic stability, high permeability, and react to external stimuli. Nanogels have shown great promise in various areas, including gene distribution, chemotherapeutic agents transmission, monitoring, and organ targeting, among others. Spheroids as in vitro tumor models were used to screen drug-loaded nanogels against in vitro cancer cells. Spheroids can represent in vivo tumor mass, reducing prices, time to results, and political/ethical considerations before clinical practice. This review focuses on different types of nanogels, preparation methods, and the main mechanisms of drug release from nanogels. Mainly, the recent applications of nanogels as drug delivery systems in multicellular spheroid tumor models are discussed.