**5. Conclusions**

EC is a water-insoluble cellulose derivative with attractive features such as biocompatibility, gastroresistance, and degradation to non-toxic and readily excreted products. It is extensively utilized in pharmaceutical technology. It is generally recognized as safe to use, even in pediatric therapy. EC is easy to process alone or with the addition of other excipients (e.g., plasticizers or other polymers). Considering its multifunctional properties, EC is being widely exploited in oral and topical drug dosage forms. EC's main advantage is its ability to modify the release of the drug, which allows for the creation of controlled delivery systems—the unique tailored carriers for many pharmaceuticals. EC-based materials are widely utilized as matrices for designing novel drug delivery systems with a wide range of applications.

**Author Contributions:** Conceptualization, K.W. (Katarzyna Wasilewska) and K.W. (Katarzyna Winnicka); Formal Analysis, K.W. (Katarzyna Winnicka); Resources, K.W. (Katarzyna Wasilewska); Data Curation, K.W. (Katarzyna Wasilewska); Writing—Original Draft Preparation, K.W. (Katarzyna Wasilewska); Writing—Review and Editing, K.W. (Katarzyna Wasilewska) and K.W. (Katarzyna Winnicka); Visualization, K.W. (Katarzyna Wasilewska); Supervision, K.W. (Katarzyna Winnicka); Project Administration, K.W. (Katarzyna Wasilewska); Funding Acquisition, K.W. (Katarzyna Wasilewska) and K.W. (Katarzyna Winnicka).

**Funding:** This research was funded by Medical University of Bialystok gran<sup>t</sup> numbers N/ST/MN/18/002/2215 and SUB/2/DN/19/004/2215.

**Acknowledgments:** We are grateful to the Editors for the permission to reprint selected figures from our previous publication (Reference number 15): Trofimiuk, M.; Wasilewska, K.; Winnicka, K. How to modify drug release in paediatric dosage forms? Novel technologies and modern approaches with regard to children's population. *Int. J. Mol. Sci.* **2019**, 29. We are thankful to Anna Basa (Institute of Chemistry, University of Białystok, Poland) for preparing SEM pictures (Inspect ™S50, FEI Company, Hillsboro, OR, USA).

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