Smart stimuli-responsive implantable drug delivery systems for programmed and on-demand cancer treatment: An overview on the emerging materials

Despite noteworthy developments in tumor therapy, cancer is still one of the main reasons for death worldwide. While present cures supply hopeful marks, they trigger harsh cytotoxicity, with limited success in preventing and recurrence of the disease. To overcome the mentioned issues, implantable biomaterials have been developed as promising systems for the local delivery of therapeutic agents to cancerous tissues. Due to the unique characteristics of biocompatible polymers, they have been used in different approaches of localized drug delivery to ensure accurate control over the release of chemotherapy drugs, genes, proteins, and peptides. In this review article, the recent progress in stimuli-responsive implantable drug delivery systems for preventing tumor recurrence and suppressing tumors are reported. In particular, we reviewed redox-, enzyme-, and pH-responsive systems in programmable drug delivery and the near-infrared-, ultrasound-, electric-, and magnetic-regulated release in on-demand local drug delivery systems. The preparation process, physicochemical characteristics of implantable materials, and kinetic models of the drug release from these platforms were also discussed in detail.