## 2 Biopolymers in Wound Dressings  
Wound dressings are used to protect wounds and accelerate the healing process. Thus, it is necessary to develop an appropriate wound dressing system [54]. Proper wound dressing materials must be flexible, biodegradable, and have an adequate gas barrier to decrease the infection rate [14]. Other significant parameters are the adhesive ability and the capability of controlling the absorbance of exudates in a wounded area [55]. Traditional dressings like woven or nonwoven gaze are the most common wound dressing system. They are applied in the first step of the healing process to prevent bleeding and protect the wound from the environment. A major disadvantage if these traditional dressings is that they promote desiccation in wounds with minimal exudate unless used in combination with another dressing or topical agent. Semisolid materials such as ointments, creams, and gels can be used alone or in combination with a protecting cover [56; 57; 58; 59; 60]. They can easily fill wound cavities as a result of their flowable properties and support the maintenance of a physiological moist environment [14; 61; 62; 63; 64]. Other forms of wound dressings include transparent films ranging from \(\upmu\)m to mm in thickness to flexibly cover the wounds [65; 66; 67; 68]. An optimal wound dressing material must appropriately respond to the wound target's characteristics, such as its size and exudate amount. Nowadays, natural biopolymers are extensively used for wound treatment because of their compatibility with the human organism. Furthermore, they show good adaptability to technological needs due to their easy chemical modification with derivatives [69]. The most common natural biopolymers applied for wound healing are polysaccharides (cellulose, alginates, chitosan, heparin, hyaluronic acid, and chondro), proteoglycans, and proteins (collagen, gelatin, fibrin, keratin, silk fibroin, and eggshell membrane) [16; 53; 70]. They have been selected based on their biodegradability and inherent cellular interaction, and closeness to the structure and surface topography of the ECM [52]. Their enzymatic degradation, which principally occurs if biopolymers are not crosslinked, releases well-tolerated byproducts [69]. Moreover, it is well known that engineered natural biopolymers can respond to physiological signals and release growth factors or related molecules to reproduce the natural healing mechanism [71]. Figure 2: A diagram of wound tissue repair using nanomaterials loaded with essential oils at a target site. For example, cellulose dressings seem to release epidermal growth factor and basic fibroblast growth factor at their application site, stimulating wound closure. They can mitigate pain and control the granulation and epithelialization processes, allowing tissue regeneration [72; 73]. Nanocellulose has also been used as a dressing biomaterial since it exhibits anti-infectious features, and in the form of a scaffold, it improves tensile properties [74]. Chitosan is a de-acetylated derivative of chitin, which is the principal constituent of the exoskeleton of insects, crustaceans, and aranchids and is similar in structure to cellulose. It is a cationic linear polysaccharide that contains D-glucosamine and N-acetylglucosamine units. Its electrostatic behavior induces the activation of early-phase reaction pathways related to accelerated wound-healing mechanisms by triggering collagen synthesis and fibroblast growth, inducing the activation of the cytokine interleukin-8. The wide use of chitosan in dressings is mostly related to its antimicrobial, non-antigenic, and film-forming features [70]. Besides, chitosan shows other advantages, such as tensile strength, easy applicability, water sorptivity, oxygen permeability, and hemostatic action [75; 76]. Another nonimmunogenic polysaccharide is alginate, which originates from brown algae. It exists in two forms: calcium and calcium sodium salts of alginic acid.