Thermoresponsive Systems

Rise in temperature is associated with several ailments including cancer. In thermoresponsive drug delivery systems, thermosensitive polymers undergo abrupt change in solubility in response to a small change in temperature [38]. Thermosensitive polymers exhibit a phase transition in solution at a temperature at the lower critical solution temperature. This process can cause conformational changes in the polymer material that triggers drug release [39]. The most commonly used thermosensitive polymers include poly(N-isopropyl acrylamide), poly(N,N-diethylacrylamide), poly(N-vinylalkylamide), poly(N-vinyl caprolactam), pluronics, polysaccharide, chitosan, and PLGA/polyethylene glycol (PEG) triblock/pentablock copolymers. The major advantages of thermosensitive polymeric systems are the avoidance of toxic organic solvents, ability to deliver both hydrophilic and lipophilic drugs, and sustained drug release. In spite of these advantages several drawbacks associated with these systems include high-burst drug release, low mechanical strength leading to potential dose dumping, instability of thermolabile drugs, lack of biocompatibility, and gradual pH lowering of the system due to acidic degradation products of the polymers [40—42].