# Advances in Three Dimensional Bioprinting for Wound Healing: A Comprehensive Review
###### Abstract  
The vulnerability of skin wounds has made efficient wound dressing a challenging issue for decades, seeking to mimic the natural microenvironment of cells to facilitate cell binding, augmentation, and metamorphosis. Many three-dimensional (3D) bioprinted hydrogel-based configurations have been developed using high-tech devices to overcome the limitations of traditional dressing materials. Based on a material perspective, this review examines current state-of-the-art 3D bioprinting for hydrogel-based dressings, including both their advantages and limitations. Accordingly, their potential applications in terms of their performance in vitro and in vivo, as well as their adaptability to clinical settings, were investigated. Moreover, different configurations of 3D bioprinters are discussed. Finally, a roadmap for advancing wound dressings fabricated with 3D bioprinting is presented. three-dimensional bioprinting; wound dressing; hydrogel; biomaterial +
Footnote †: journal: Medical Engineering and Computer Sciences  
0000-0001-6998-2231]E. E.  
dressing candidate. In addition, active ingredients such as nutritional supplements, growth hormones, antibacterial agents and other drugs can be loaded into the wound dressing matrix, thereby releasing these active ingredients into the wound site. The 3D printing technology can be used to prepare wound condition-specific hydrogel dressings to meet patient requirements. Moreover, the simple printing principle, cost-effective bioprinting ink material and stable printing equipment make extrusion-based 3D printing suitable for the mass production of wound dressings. With modern dressings, compared to traditional dressings, removal of the dressing does not damage the site and bleeding does not occur. Over the past few decades, the production of functional wound dressings involving solely hydrogels or hydrogels incorporated with growth factors, stem cells, antibiotics, and other therapeutic substances for wound management has been performed by advanced technologies to support and accelerate the healing process [9; 10; 11; 12]. An optimal microenvironment for wounds could be obtained by enriching the material to acquire particular characteristics, like bacteria kill/inactivator, pH, moisture, oxygen, nutrients, cellular agents (calcium, hydrogen peroxide, copper, iron, etc. ), and to exudate drainage regulators, regardless of skin damage severity [13]. Ultimately, they provide higher rates of wound closure, re-epithelialization [14] and angiogenesis without exhibiting cytotoxicity [15]. Besides the importance of material characteristics for wound management, the selection of the production technique plays a crucial role in generating personalized hydrogels with high precision and speed, in the case of complex-shaped materials for the desired application. The use of 3D bioprinting enables the creation of wound dressings with micron-sized biomimetic structures. Traditional wound dressings use production techniques such as molding, casting, shaping, and processing, but these techniques are not suitable for complex and customized designs at high resolution. With the help of a 3D bioprinter, it is possible to create anatomically correct, patient-specific dressings containing antibacterial and bioactive molecules [16]. Three-dimensional bioprinting is an additive manufacturing process that incorporates various printing techniques (e.g., stereolithography, direct ink writing, digital light processing, etc.) through computer-aided design (CAD) for producing complex, patient-specific structures at high speed [17]. It is possible to create models using 3D CAD software, or by acquiring sliced images via computed tomography (CT) scans and magnetic resonance imaging (MRI). Due to their capacity for customization, these techniques enable the material to mimic the target wound area with high precision and resolution and create 3D structures containing living cells, therapeutic agents, and hydrogels [18; 19].