*2.5. Films*

Topical film-forming systems are drug delivery systems for topical applications that are capable of adhering to the skin, forming a thin transparent film that provides delivery of the active ingredients to the body tissue (Figure 3D) [69]. These systems are composed of the drug- and film-forming agents in a volatile vehicle, which evaporates in contact with the skin [69]. Even though it is a promising option for topical drug delivery, the literature on the incorporation of AST as a way to exert antioxidant effects on the skin is scarce.

Veeruraj et al. [23] prepared films to demonstrate the wound healing properties of AST when incorporated in collagen films. In vivo assays were performed to assess tissue regeneration and drug delivery from the formulation, and in vitro assays to check the antioxidant activity. In addition to the AST collagen film, a gentamicin-incorporating collagen film was developed to assess its antibiotic effects. The filming agen<sup>t</sup> and AST were extracted from the waste material of the outer skin of the squid *Doryteuthis singhalensis*, which is an innovative and sustainable alternative for the development of this delivery system. Biodegradation tests showed that film materials degraded more rapidly than the collagen matrix, suggesting the controlled degradation of collagen materials. Wound healing activity was measured by the reduction of the non-healing area in the healing process, occurring over 21 days. The untreated control exhibited the lowest wound contraction, whereas the AST collagen film showed the highest one among the experimental groups, as well as the fastest wound-healing progress, with complete healing in 15 days. Antioxidant assay by the DPPH free radical scavenging method showed the higher activity of AST collagen film compared to ascorbic acid. The main information on this article is presented in Table 5.

**Table 5.** Summary of AST film delivery systems, describing the preparation technique, filming agent, characterization and stability data, and assays (in vitro/in vivo) that were performed for the system.

