## 4 Polyphenol-Based Systems and Their Unveiling Potential for Wound Care
### Polyphenol Encapsulation Techniques  
Due to the polyphenols' reactivity, encapsulation technology plays an important role to protect and stabilize phenolic compounds. The encapsulation process is characterized as the technique by which bioactive compounds are entrapped into coating materials or encapsulation matrices [61]. The applications of encapsulation are exponentially increasing due to its high potential, and nowadays, encapsulation is used in many scientific and industrial domains, such as biomedical, cosmetic, food, veterinary, textile, agriculture, pharmaceutical, and chemical industries. The rationale for creating an encapsulation system can be (i) protection of the encapsulated material against environmental factors including UV rays, moisture, and oxygenated environment, (ii) promotion of a controlled release of the encapsulated compound, (iii) contribution to an increase in the shelf life of the product, (iv) reduction of bioactive compound needed at the target site, and (v) structuration and functionalization of the product [61]. The coating material is a vital component in any encapsulation process. An appropriate wall material determines the physical and chemical properties of the resultant micro or nanoparticles. Different materials can be used as encapsulating materials, such as proteins, lipids, gums, and natural or synthetic polymers [85]. Micro and nanoencapsulation of polyphenols have been continually explored in order to increase their bioavailability in several potentials in food and pharmaceutical industries,in addition to their therapeutic potentials in healthcare. Both techniques involve the formation of active-loaded particles with regular (spherical, oval, and tubular) or irregular shapes and diameters ranging from 1 \(\upmu\)m to 1000 \(\upmu\)m, in case of microparticles, and from 1 nm to 1000 nm in nanoparticles [86]. In terms of morphology/structure, particles can be classified as capsules or spheres. Generally, both terms are considered and mentioned as being equal, but theoretically, they have different morphologic characteristics. While capsules are described as a vesicular or reservoir system, where the shell is around the core (or an outside layer), spheres are characterized as a matrix type, where the core material is distributed homogeneously or heterogeneously into the outside layer. A few encapsulation methods have been developed on micro- and nanoscales. There are different techniques used for encapsulation of polyphenols--the spray drying, electrospinning, liposomes, coaervation, and inclusion encapsulation being the most used methods [86]. The choice of the most suitable technique must be studied based on decisive factors, including the type and the size of particles desired, the application of the product, physicochemical properties of both the core material and the encapsulating agent, the type of controlled release, the production scale, and the cost. The spray drying method is one of the most used techniques for the encapsulation of polyphenols. Spray drying is a process based on the transformation of a liquid feed, which is composed of a certain active agent with a chosen coat material, in dry particles by atomizing the feed in a flow of hot air [81]. This method is characterized by the ability to decrease the water activity, avoid degradation processes, and ensure microbiological stability [87]. For all the advantages of the encapsulation method, spray drying is one of the most used methods to produce microparticles in the pharmaceutical industry and laboratory applications, and the most suitable method for the encapsulation of hydrophilic and hydrophobic phenolic compounds obtained from plant sources. Different polyphenols encapsulated by the spray drying method were already studied, such as procyanidins, tannins, olive leaf extract, and anthocyanins. Electrospinning is also a versatile processing tool that can allow for the effective encapsulation of polyphenols with great potential for wound healing, as revised by [PERSON] et al. [88].