Applications of nanotechnology for physical stimulus-responsive cancer therapies

Multifunctional theranostic agents that are responsive to external physical stimuli such as light, magnetic field, ultrasound, radiofrequency, and X-rays have been widely explored for their use in physical stimulus-responsive therapies for cancer. Encouraging results in many preclinical animal experiments have been obtained; thus, this innovative strategy has gained great attention. Owing to the nontoxicity of physical stimulus-responsive agents and treatment specificity under particular external stimuli, physical stimulus-responsive cancer therapies provide greatly reduced toxicity and enhanced therapeutic efficiency compared with conventional chemotherapeutic agents. When combining physical stimulus-responsive therapies with other traditional therapeutics, synergistic antitumor effects via various mechanisms can be achieved. In this review, we will summarize the recent developments in physical stimulus-responsive therapies and discuss the important roles of nanoscale theranostic agents in these novel treatment modalities.