# Modifications of Wound Dressings with Bioactive Agents to Achieve Improved Pro-Healing Properties
## 3 Pro-Healing Wound Dressings
### The Effect of Natural Compounds on Skin Regeneration
#### 3.1.2 Essential-Oil-Loaded Biomaterials  
Essential oils (EOs) are plant secondary metabolites that are characterized by antioxidant, anti-inflammatory, and antibacterial properties. Thus, EOs possess features that are useful in the chronic wound management [63]. According to the literature, EOs have also anti-tumor, anti-diabetic, analgesic, and antiviral properties [64]. Modifications of biomaterials with different EOs are presented in Table 2.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Type of** & **Composition of the** & **Experimental Model** & **Biological Properties** & **Limitations** & **Ref. ** \\
**Biomaterial** & **Biomaterial** & & & **and Advantages** & \\ \hline \multirow{3}{*}{Hydrogel} & \multirow{3}{*}{Thymol, bacterial cellulose} & In vitro (NIH 3T3—mouse & Enhanced antibacterial activity (_E. coli, S. aureus, P. aeruginosa,_ _K. pneumoniae)_ and wound & Decreased water vapor & [65] \\  & & (rat model) & & closure speed & transmission rate & \\ \hline \multirow{3}{*}{Nanofiber} & \multirow{3}{*}{Thymol, tyrosol, PCL} & In vitro & \multirow{3}{*}{Anti-inflammatory activity} & \multirow{3}{*}{Not provided} & [66] \\  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \hline \multirow{3}{*}{ \begin{tabular}{c} Fibrous membrane \\ \end{tabular}  } & \multirow{3}{*}{Thymol, cellulose} & In vitro (1,929—mouse & Enhanced antibacterial activity (_E. coli, S. aureus_) & Decreased wettability & [67] \\  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \hline \multirow{3}{*}{Nanofiber mat} & \multirow{3}{*}{Thymol, cellulose} & In vitro (1,929—mouse & Enhanced antimicrobial activity (_E. coli, S. aureus_, _S. [PERSON] et al. [65] incorporated thymol (which is primarily isolated from _Thymus vulgaris_ EO) into bacterial cellulose hydrogel in order to improve biological properties of the biomaterial. The introduced modification not only increased the antibacterial activity against _E. coli_, _S. aureus_, _P. aeruginosa_, and _K. pneumoniae_, but also promoted faster wound closure in the in vivo rat animal model. Nevertheless, the conducted tests showed that the biomaterial with the addition of thymol had reduced water vapor permeability compared to the control sample. Similarly, [PERSON] et al. [67] evaluated the effect of thymol addition to the cellulose fibrous membranes on their antibacterial properties. It was shown that porous biomaterial with the highest content of thymol (15%) revealed the best antibacterial properties (bacteria survival rate equal to 0.07% for _S. aureus_ and 0.09% for _E. coli_). However, the water contact angle of the sample surfaces increased with the increased content of thymol in biomaterials. In turn, [PERSON] et al. [66] investigated the impact of EO-derived compounds on the biomedical properties of electrospun PCL nanofibers. The biomaterial produced by incorporation of thymol revealed anti-inflammatory activity and showed the ability to the reduce size of inflamed cells. In another study, [PERSON] et al. [68] focused on the modification of nanofiber mats with an essential oil obtained from _Zataria multilora_. The study revealed a decreasing degree of biomaterial swelling with increasing content of the essential oil that may be related to its hydrophobic nature. Moreover, enhanced antimicrobial activity (_C. albicans_, _S. aureus_, and _P. aeruginosa_) of produced EO-loaded biomaterial was observed without cytotoxic effect on mouse fibroblast cell lines. [PERSON] et al. [64] produced chitosan films with the addition of various content of EOs obtained from _Eugenia carophyllata_ and _Melaleuca alternifolia_. Obtained results showed that EOs did not affect the hydrophilicity of the tested films. However, the maximum tensile strength value recorded for pure chitosan biomaterial was higher than value estimated for EO-loaded samples, indicating reduced mechanical strength of the modified films. Nevertheless, the addition of the EOs improved elasticity and flexibility of the films. In turn, [PERSON] et al.