**3. Applications**

The various physicochemical properties of alginate are favorable to extensive usages, such as the ability to form a gel and the ability to maintain a moist environment, which has been confirmed by the literature. Due to the biocompatibility and nontoxic, alginate has been applied in biomedical applications, such as wound dressing, drug delivery, and tissue engineering.

## **3.1 Wound dressing**

Skin, as the largest human organ, plays a vital role in protecting the human body from outside germs [25]. It is also a vulnerable organ. Once the skin is damaged, all kinds of microbes and pathogens will gather around the wound site to affect the wound closure cause bacterial infection. For severe wounds with large, deep, or bleeding, handling and management are essential [26]. Wound healing is a complex process, involving the treatment of infectious, germs. Therefore, wound dressing has been attracted extensive attention and is widely used to accelerate wounding recovery and to control infection. Traditional dressing, consisting of sterile pad and gauze, has the features of preventing the invasion of germ into the wound site and keeping dry [27]. Some disadvantages of these dressings are displayed during the application, such as poor vapor transmission, susceptiblity to bacterial infection, and easy adhesion, which seriously interfere with wound healing. With the rapid development of technology, some biomaterials such as polysaccharides, proteoglycans, and proteins have been investigated for wound healing owing to their ability to accelerate healing and control infection [28, 29]. These polymers have been utilized to develop modern dressing due to its high water-content, biodegradable, and biocompatibility. Therefore, modern wound dressing effectively mimics the features of natural tissue and offers a moist environment, better water vapor permeation, autolytic debridement, which cause to promote re-epithelialization and accelerate wound healing [30].

Alginate, as one of these biomaterials, has been widely concentrated and investigated because of its biocompatibility and water-retaining capacity [31]. It has the ability to carry pro-inflammatory signals and initiate or accelerate the healing of chronic wounds [32]. Currently, there are several forms of alginate dressing on the market, including hydrogel, films, membrane, and sponges. Ionic cross-linking is a representative fabrication method of alginate dressings. Multivalent ions are chosen to fabricate gel, such as calcium [33], magnesium [34], iron [35]. Free-dried porous sheets and fibrous dressing that followed are formed. Alginate dressings are characterized by absorbing wound fluid, physiologically moist environment, maintain the optimal pH, and reduced bacterial infections, that improve the physicochemical stability [36, 37].

Alginate wound dressings with multifunctional properties have been investigated for nearly 40 years. Kaltostat® alginate dressing, as a famous wound dressing, has been designed and applied to absorb exudate and avoid infections, especially calcium sodium alginate dressing. Nevertheless, only 70% wound closure is exhibited [38]. Considering that single alginate dressing could not completely prevent infections and moderate wound healing, the development of effective alginate dressing, based on biopolymers and nanoparticles, draw much attention and expanded research.

Alginate composites combining natural polymer and synthetic polymer are utilized to prepare dressing hydrogel via physical or chemical methods. Chitosan, as a typical natural polymer, has several advantages, such as biocompatibility, biodegradability, ionic character, and hemostatic properties. It could be incorporated with alginate to create bioactive interpolymer (polyelectrolyte) complexes and promising wound dressing. Wound dressing formed with this method exhibited superior water uptake of 4343.4% over 24 h and 78% biodegradation than commercial Pharma-Algi wound dressing [39]. Mudlovu et al. fabricated an

### *Alginate-Based Composite and Its Biomedical Applications DOI: http://dx.doi.org/10.5772/intechopen.99494*

alginate-chitosan bioplatform through a three-step method; partial-crosslinking of polymers, lyophilization, and pulverization (**Figure 2**) [39]. These wound dressings showed a higher degree and rate of fluid uptake (3306.61%, 4343.4%) than Pharma-Algi® (2168.21%; 1612.56%). For chitosan with high (MW ~ 800 000) and low (MW ~ 3000) molecular weight, it was mixture as a coating to develop calcium alginate dressing. The results showed that chitosan promotes angiogenesis by increasing VEGF and exhibits better wound healing than pure calcium alginate dressing [40]. In addition to the natural polymer, poly (vinyl alcohol) (PVA), as a type of common synthetic polymer, has the inherent characteristics of non-toxic, non-carcinogenic, biocompatibility. PVA hydrogel formed with cross-linking method has desirable properties such as high swelling rate, keeping the moist environment. Therefore, PVA has been attracted attention and explored for wound dressing. PVA-alginate hydrogel enhanced swelling properties and protein adsorption. When alginate has a high ratio in the PVA/Calcium alginate wound dressing, high a water vapor transmission rate, 2725.8 g/m<sup>2</sup> /2h, was obtained, which contributes to holding a moist environment [41].

In order to endow the additional effects and accelerate wound healing, the antimicrobial agent has been incorporated into the wound dressing. Silver nanoparticles (AgNPs), as a promising wide-spread local antibacterial agent, have demonstrated huge potential and received more attention in the area of microbial resistance. Wound dressing carried with AgNPs is considered to control and treat acute and chronic wounds, accompanied by rapid healing via accelerating reepithelialization [42]. Alginate dressings incorporated with silver have highly absorbent features of alginate and antimicrobial efficacy of silver. Silver-loaded hydrogel has a uniform pore structure, had excellent water absorption and water retention, maintaining a moist wound environment for wounds [43]. The antibacterial performance is also

#### **Figure 2.**

*(A) Schematic representation of the three-step method of partial-crosslinking and interpolymer complexation of the polymers. (B) (a) biodegradation and (b) water uptake behavior of the pristine polymers, bioplatforms and pharma-Algi® in PBS (pH 7.4) solution at 37°C at 50 rpm [39].*

improved. Alginate/carboxymethyl cellulose silver dressing was found to have a sustained antimicrobial effect against microorganisms, for up to 21 days [44]. The sustain and stable release of sliver minimize clinical treatment time and relieve the patient's pain. Compared with pure alginate, alginate dressings incorporating ionic silver and nanocrystalline silver were confirmed to enhanced antimicrobial effect, improved the binding for elastase, matrix metalloproteases-2, and proinflammatory cytokines, and boosted the antioxidant capacity [45].
