Cancer is a broad term for a set of disorders marked by the development of physically and functionally changed cells that proliferate uncontrollably, infect neighboring tissues, and result in malignant tumours, 'neoplasm'. Cancer remains a difficult disease to treat because of the significant adverse effects and poor pharmacokinetic profile of antineoplastic drugs, despite advancements in our understanding of the features and behavior of tumor cells in recent decades. In this series, the role of natural polymers is prominent as a component of a novel delivery system of anticancer drugs. These natural polymeric drug delivery systems (NPDDS) have many advantages over synthetic polymers like controlled delivery, biodegradability, inexpensive, low toxicity profile, and easily obtainable. These polymers further modify for the targeting of tumour cells. This review discusses and critically analyses the different natural polymers, such as chitosan, cellulose, starch, albumin, dextran, fucoidan, gelatin, etc., in terms of natural ingredient-based polymeric nanocarriers specifically for cancer therapy. It also describes benefits, drawbacks, and opinions and provides insights about the efficacy of NPDDS as well as its future perspectives and tabulated recent patents and cases under clinical trials exploited for cancer treatment.

The temperature-triggered in situ gelling system has been revolutionized by introducing an intelligent polymeric system. Temperature-triggered polymer solutions are initially in a sol state and then undergo a phase transition to form a gel at body temperature due to various parameters like pH, temperature, and so on. These smart polymers offer a number of advantages, including ease of administration, long duration of release of the drug, low administration frequency with good patient compliance, and targeted drug delivery with fewer adverse effects. Polymers such as poly(N-isopropylacrylamide) (PNIPAAm), polyethylene glycol (PEG), poly (N, N′-diethyl acrylamide), and polyoxypropylene (PPO) have been briefly discussed. In addition to various novel Drug Delivery Systems (DDS), the smart temperature-triggered polymeric system has various applications in cancer therapy and many other disease conditions. This review focuses on the principals involved in situ gelling systems using various temperature-triggered polymers for chemotherapeutic purposes, using smart DDS, and their advanced application in cancer therapy, as well as available marketed formulations and recent advances in these thermoresponsive sol-gel transforming systems.