The discovery of novel methods to fabricate optimal scaffolds that mimic both mechanical and functional properties of the extracellular matrix (ECM) has always been the “holy grail” in tissue engineering.

As the second most common cause of cancer‐related death worldwide, colorectal cancer (CRC) requires novel therapy strategies. Biodegradable polymers are used as drug carriers for treating CRC and other cancers. However, one of the limitations for the polymeric drug carriers is that they do not directly involve the treating procedure. Herein, to develop a polymeric drug delivery system with additional therapeutic effect from that of the polymer itself, poly(ursolic acid) (PUA) is, for the first time, simply synthesized via polycondensation of ursolic acid (UA), a bioactive ingredient widely distributed in herbal medicine. PUA can self‐assemble into nanoparticles (PUA‐NPs) with a diameter of ≈122 nm and an effective load of ≈10.1%, and deliver drugs, such as paclitaxel (PUA‐NPs@PTX). In vitro studies show that PUA‐NPs@PTX have strong cytotoxicity against colorectal cancer CT26 cells, while in vivo results indicate that these NPs have a prolonged blood circulation time, enhanced tumor accumulation, and significantly improved antitumor efficacy in CT26 tumor‐bearing mice. Furthermore, both in vitro and in vivo results confirm that the PUA‐NPs themselves have therapeutic effects on CT26 cells, without causing obvious toxicity to main organs, such as bledding or necrosis. In summary, such a therapeutic polymer platform provides a new therapeutic strategy for treating cancer.

Bioresponsive polymers have been widely used in drug delivery because of their degradability. For example, poly(disulfide)s with repeating disulfide bonds in the main chain have attracted considerable research attention. The characteristics of the disulfide bonds, including their dynamic and reversible properties and their responsiveness to stimuli such as reductants, light, heat, and mechanical force, make them ideal platforms for on-demand drug delivery. This review introduces the synthesis methods and applications of poly(disulfide)s. Furthermore, the synthesis methods of poly(disulfide)s are classified on the basis of the monomers used: oxidative step-growth polymerization with dithiols, ring-opening polymerization with cyclic disulfides, and polymerization with linear disulfides. In addition, recent advances in poly(disulfide)s for the delivery of small-molecule or biomacromolecular drugs are discussed. Quantum-dot-loaded poly(disulfide) delivery systems for imaging are also included. This review provides an overview of the various design strategies employed in the construction of poly(disulfide) platforms to inspire new applications in the field of drug delivery.

Chemotherapy, combined with other treatments, is widely applied in the clinical treatment of cancer. However, deficiencies inherited from the traditional route of administration limit its successful application. With the development of nanotechnology, a series of smart nanodelivery systems have been developed to utilize the unique tumor environment (pH changes, different enzymes, and redox potential gradients) and exogenous stimuli (thermal changes, magnetic fields, and light) to improve the curative effect of anticancer drugs. In this review, endogenous and exogenous stimuli are briefly introduced. Among these stimuli, various redox-sensitive linkages are primarily described in detail, and their application with self-assembled nanoparticles is recounted. Finally, the application of redox-responsive self-assembled nanoparticles in cancer therapy is summarized.

The nanoassemblies of Dex6k–BSA–PTX and the pH-responsive drug release for anti-tumor applications in vivo.