**4. Other applications of Chitosan-based nanocomposites**

Significant attention has been paid to many kinds of biomedical fields because of Chitosan-based nanomaterials due to their special chemical properties, including desired biodegradability, compatibility, and nontoxicity. Chitosan is a convenient biomaterial to construct extracellular tissue matrixes in tissue engineering [67]. Chitosan can be used as a carrier for drug delivery and also for different types of therapeutic molecules such as genes, drugs, and proteins [68]. It is greatly used as a carrier in delivering active agents and drugs [69], in gene and cancer therapy [70], and also in biosensor monitoring and bioimaging [71, 72]. Chitosan behaves like an anti-plaque agent and can intervene with all microorganisms while performing antibacterial activities in dentistry [73]. Chitosan is more generally used in wound dressing as an antimicrobial and antifungal agent because of its perfect tissue adhesive features (**Figure 3**).

#### **4.1 Wound healing applications of Chitosan-based nanocomposites**

Polymer nanocomposites are described as sophisticated materials, which carry nanoparticles. They can also be presented as core-shell nanoparticles. Chitosan produced an amino group that can be operationalized further to be reconciled for a great variety of applications. Antimicrobial chitosan nanocomposites are also attractive in food preservation as well as in medical fields. The downside of chitosan

**Figure 3.** *Schematic representation of Chitosan-based nanocomposites in biomedical applications (https://biorender.com/).*

is its solubility being in only an acidic solution. This is solved by using chitosan as a derivative of lactose to form chitilac [74, 75]. Burst release is less effective than the controlled release of drugs through nano carrier matrix-like nanofibers, membranes, spheres, capsules, tubes, etc.

The antimicrobial activity of chitosan nanocomposite [76] was utilized by Youssef. The effect of Montmorillonite-chitosan-silver sulfadiazine nanocomposites on skin lesions was also prepared and utilized by Sandri. Montmorillonite has hemostatic and absorbent features and it is used in the healing of lesions and ulcers [77, 78].

Wound healing is not the simple programmed structure of cellular and molecular developments including swelling, cell immigration, angiogenesis, temporal matrix syntheses, collagen deposition, and re-epithelization. Mostly, an effective wound dressing has the subsequent properties: (1) an appropriate water vapor transmission rate (WVTR), which produces a humid environment on the wound beds, without risking dehydration or exudates accumulation; (2) adequate gas penetrability for oxygen-requiring reparative methods; (3) a great level of fluid absorption ability to get rid of too many exudates, which cover nutrients for bacteria from the wound beds; (4) a good blockade trans the distribution of contagion producing microorganisms; (5) activity of antibacterial to overwhelm bacteria growth lower the dressing; and (6) the lack of any cytotoxic effects in the event of side damage to the neonatal tissues. Thus far numerous wound dressing materials types have been stated; however, they have some severe faults such as low water vapor/gas transmission rate, the capability of poor fluid absorption, and low flexible strength. So, we choose chitosan as a dressing material because of its biocompatibility [79–81] biodegradability [82], hemostatic activity [83, 84], the activity of anti-inflectional [85, 86], and property to accelerate wound healing [87–89]. The N-acetyl glucosamine (NAG) current in chitin and chitosan is a chief element of dermal tissue that is vital for the repair of scar tissue [90, 91]. Its positive surface charge permits it to effectively support cell growth [92] and helps surface stimulated blood clotting and blood coagulation [93].

#### **4.2 Tissue engineering applications of chitosan-based nanocomposites**

3-D porous scaffolds for bone tissue studies should be biocompatible and let osteogenesis. Various techniques have been enlarged to imitate natural mineralized materials' properties and microstructure. Yet, large-size bulk materials' simple and fast fabrication with the content of high calcium under environmental aspects remains a big difficulty. Throughout gelation, a manageable inorganic gradient supply formula, accompanied by mineralization, where urea was used, and naturally hierarchically well-ordered hydrogel microstructures were shaped. This construction route takes a couple of hours to complete the gelation and processes of mineralization [94].

Composite scaffolds have been fabricated which use a coaxial electrospinning method to prepare gelatin-chitosan core-shell structured nanofibers. An arginineglycine-aspartic acid (RGD)-like structure was shaped to imitate the structural component of the extracellular matrix of natural bone. After, by a wet chemical technique, hydroxyapatite was deposited on the prepared-shell structured nanofibers surface. Hydroxyapatite is the key mineral component of natural bone. Gelatinchitosan core-shell structured nanofibers enhanced the mineralization productivity of hydroxyapatite compared to chitosan nanofibers [95]. Biologically-active scaffolds design is focused on cell-adhesive protein applications or bioceramic nanoparticles to produce a cell-sensitive surface. Hence, trace metals found in the alive organisms were used to prepare hydrogels of biocompatible chitosan. These were modified by copper (II) ions through complexation connections and generated a fewer constant cytocompatible to more constant cytotoxic structure for a copper-chitosan system [96, 97].

#### **4.3 Cancer therapy applications of chitosan-based nanocomposites**

Carcinoma involves the cell's uncontrolled proliferation. Operation and chemotherapy frequently are combined as a full strategy to defeat the tumor [98] Chemotherapy is a systemic treatment with the benefit of reducing lasting potential metastatic lesions after the operation. It has the benefit to treat numerous wounds contemporaneously, on the other hand, it is also apparent because of the systemic side effects, which may affect healthy tissue [99]. Numerous optimized chemotherapy strategies have been developed to solve the above-referred problems. Nanomaterials have been designed to target particular tissues or react to specific environmental conditions. CS is mostly developed to antitumor nanovesicles for the carcinoma behavior due to its matchless properties such as mucoadhesiveness and structural changefulness [100].

There are various articles about chitosan-based systems for antitumor drug delivery in advanced methods [101, 102]. Effective drug delivery systems are enhanced for therapy of anti-cancer based on environmental responsibility and directing principles to convey drugs, vaccines, etc. Furthermore, the drug delivery vectors were also designed with a mixture of photodynamic and hyperthermia cure (**Figure 4**) [103, 104].

Numerous healing anticancer drugs are limited in their scientific applications due to their toxicities and are not high solubility in aqueous media [105–107]. For example, doxorubicin (DOX) is one of the greatest commonly used drugs in cancer therapy. Yet, it can cause side reactions such as cardiotoxicity and drug resistance. Also, it is hard to manage intravenously due to its not high solubility in aqueous media.

**Figure 4.** *Drug delivery (https://biorender.com/).*

Nanomaterial-based drug delivery systems have received attention in overwhelming this downside. These systems can be made from several organic and inorganic materials including nondegradable and biodegradable polymers and inorganic nanocrystals. Polymeric micelles based on amphiphilic block copolymers have the benefits of great biocompatibility and capacity of drug-loading with less toxicity since they can selfassemble into polymeric micelles in aqueous media [108–110]. The mass in tumors through an improved penetration and retention (EPR) effect compared to single minor molecules, principal to special spatial distribution in the tumor. Nevertheless, the drug release performance of polymeric micelles is hard to control; they spontaneously release the drug before reaching tumors, which could give increased undesirable side effects and less therapeutic efficacy [111]. Well-designed drug delivery systems need to be advanced to enable cancer chemotherapy, which basically improves therapeutic efficacy by reducing drug release in unwanted sites. With these systems, a particular drug concentration can be delivered to tumors to diminish side effects. Drug delivery systems can be designed to release drugs stimulated by environmental parameters such as pH, enzymes, and temperature [112–114].
