# The Antimicrobial Effectiveness and Cytotoxicity of the Antibiotic-Loaded Chitosan: ECM Scaffolds
## 1 Introduction  
At its simplest, a superficial wound can be described as damage to the skin due to burn, trauma or incision. However, this description fails to appreciate the complex nature of the wound environment and the unique problems that define the severity of the wound as it relates to variables such as trauma type, location and size. Severe wounds can lead to death as a result of infection or blood loss and frequently require specialist wound dressings and intensive care. However, while there is a high demand for wound dressings to enhance hemostasis, accelerate tissue repair and combat infection, advances in wound dressing technology are lacking due in part to the intrinsic complexity of the wound healing process. Ideal wound dressings should conform to the wound, help maintain a moist environment while assisting with the removal of wound exudates and facilitate the wound healing process. Additionally, attributes such as control of infection, hemostasis and promotion of constructive tissue remodeling would be desirable features. Choice of wound dressing rangesfrom the relatively simple, such as paraffin-gauze, to complex hydrogels and colloids that may or may not contain bioactive factors to promote angiogenesis or re-epithelialization. More recently, the development of biologic dressings for wound repair has resulted in dressing materials that attempt to restore the wound microenvironment by providing either bioactive factors, extracellular matrix (ECM) components or both to stimulate granulation tissue formation, angiogenesis and re-epithelialization. Two such materials are chitosan and ECM derived from decellularized tissues. Chitosan is a \(\beta\)-1,4-linked polymer of glucosamine (2-amino-2-deoxy-\(\beta\)-d-glucose) and lesser amounts of N-acetylglucosamine. It is a derivative of chitin (poly-N-acetylglucosamine), which is the second most abundant biopolymer after cellulose [1]. The structural characteristics of chitosan mimic glycosaminoglycan components of the extracellular matrix, while the biocompatibility, biodegradability, antibacterial [2; 3], antioxidant activities and mucoadhesive properties impart versatility. Various kinds of modification of chitosan have been investigated in recent years using acylation, alkylation, carboxymethylation and quaternization [4]. Recently, the antibacterial and antifungal activities of chitosan have been followed with great interest [2; 5; 6; 7]. Furthermore, incorporation of antibacterial agents into the chitosan backbone offers excellent antibacterial properties [3; 8; 9]. Chitosan also has a strong affinity for binding with red blood cells and blood components allowing chitosan materials to rapidly clot blood [10; 11; 12]. Chitosan-derived materials have recently gained regulatory approval in the USA for use in bandages and other hemostatic materials [13; 14]. In addition, chitosan is known to modulate the functions of inflammatory cells to promote granulation tissue formation [15; 16; 17]. ECM scaffolds derived from decellularized tissues represent the secreted products of resident cells within each tissue and organ and include structural components such as collagen, laminin and hyaluron as well as secreted growth factors, nanovesicles and other signaling molecules. These molecular components are arranged in tissue specific patterns which are determined by the physiologic and biomechanical requirements of each tissue [18]. The biologic properties of the matrix are only partially understood, but they are known to affect the interaction with resident cells and infiltrating cells. ECM scaffolds modulate cell behavior including alteration of macrophage phenotype, proliferation, mobilization, and differentiation of stem and progenitor cells, and regulation of angiogenesis, among others [19; 20; 21; 22]. Moreover, the degradation of these scaffolds releases embedded nanovesicles and cryptic peptide molecules, which play a key role in the biological activity of these materials [23; 24] including antimicrobial activity.