**7. Conclusions**

Actual cancer treatment is helping to increase the survival rates and prognosis and, in some cases, to cure cancer in patients. Nevertheless, the fight against cancer is not over, especially for CRC, which is one of the most aggressive cancer types. Consequently, cancer is and will remain a hot topic in research.

Among the different adjuvant therapies for complementing or avoiding the surgical removal of the affected area, oral chemotherapy is the most convenient for patients and health professionals. Chemotherapy treatment is continuously evolving to reduce side effects and enhance the therapeutic effects of natural and synthetics drugs, using strategies involving the encapsulation of bioactive compounds. Furthermore, thanks to molecular biology and chemistry, researchers can quickly check the anticancer properties of bioactive compounds in vitro and in vivo in order to compare treatments.

Polymers are versatile biomaterials that can be loaded with CRC-targeting compounds and processed to tailor the desorption kinetics to respond to pH, enzymes, cellular receptors, and time, among others. Despite none of the studies aiming to compare response types (pH, enzymes, time, or cellular receptors), pH-responsive polymers are seemingly the most promising, so new research should be focused on studying polymer families with other ways of responding to stimuli. In vivo pharmacokinetics are a useful tool to compare polymers and bioactive compounds in order to optimize the therapeutic effects of such compounds.

Finally, it can be concluded that antioxidants are emerging compounds that, in the short term, will complement current chemotherapy treatments, and in the long term, these natural drugs will replace 5-FU and will play an important role in curing colorectal cancer.

**Author Contributions:** Conceptualization, M.O.; data acquisition, M.O.; writing—original draft preparation, M.O.; writing—review and editing, M.O., E.M., T.N. and C.C.; project administration, C.C.; All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by MINCIENCIAS, Colombia under the project Nanobiocáncer grand number FP44842-211-2018.

**Acknowledgments:** Authors wants to thanks to Ana Colorado from the VIGILA Department of the Universidad Pontificia Bolivariana for the valuable help in the use of Vantage, AcclaimIP and Derwent.

**Conflicts of Interest:** The authors declare no conflict of interest.
