cancer treatment in the field of cancer, ultrasound is commonly used for helping health care professionals detect and develop a diagnosis in affected patients. in the context of drug delivery, ultrasound has been used for a wide variety of therapeutic applications which include but are not limited to melanoma, ovarian cancer, and breast cancer. hydrogels are generally used in designing these drug delivery platforms due to minimal invasiveness (if injected) and its ability to carry a different cancer drugs. these hydrogel-based systems are also paired with chemotherapy treatments. cancer drugs used in this drug delivery platforms include doxorubicin, mitoxantrone, paclitaxel, silibinin, and cisplatin. in a cancer therapy study, baghbani et al. proposed a method of pairing ultrasound with doxorubicin-loaded alginate-stabilized perfluorohexane (pfh) nanodroplets. gene therapy although it is generally used in combination with cancer therapeutic treatments, gene therapy has become a topic of interest in the drug delivery field. gene therapy refers to the insertion of genes into a biological system in an attempt to add or modify mutated genes for therapeutic benefit. in order to attain high transgene expression, the electrostatic interaction between the gene and hydrogel polymer and the controlled release of the drug payload from the hydrogel is necessary. several gene therapy drugs used in hydrogel-based drug delivery systems include crispr/cas9, sirna, and other rna-based drugs. in a gene therapy study, han et al. proposed a focused ultrasound-responsive hydrogel-based system for delivering sirna nanoparticles to the targeted tumor site major challenges and future direction the main challenge for future ultrasound-triggered hydrogel responsive delivery systems is to develop safer guidelines for using hifu to take advantage of its benefits. in doing so, this will lead to improvements on fda guidelines for ultrasound use. therefore, the use of lifu or lower acoustic energy intensity settings is suggested as the conventional method for decreasing injury risk, specifically damage to healthy tissue, until then. focused ultrasound continues to be the primary type of ultrasound technique used in drug delivery systems. another challenge presented in using ultrasound for inducing drug release from smart hydrogels in delivery platforms is inappropriate drug administration and unexpected complications. currently, on-demand drug release from ultrasound-responsive hydrogels is still difficult to fully control when only using ultrasound. yeingst et al. suggested that future hydrogel-based delivery platforms will be designed based on the drug payload to optimize the interaction between the ultrasound and stimuli-responsive hydrogel. future development of drug delivery systems will continue to incorporate ultrasound and smart hydrogel designs.