# Use of Anionic Polysaccharides in the Development of 3D Bioprinting Technology
## 1 Introduction  
At the opening scene of the famous French film entitled the \"Fifth Element\", released in cinemas in 1997 with [PERSON] as main actor, the body of the beautiful [PERSON] was built by a three-dimensional (3D) printer using her genetic code extracted from a fragment of her skeletal tissue Of course, this technology was considered, and will always be, fictional but it is potentially becoming reality with the rapid development of 3D bioprinting using natural biopolymers such as polysaccharides. 3D printing involves various processes in which material is joined or solidified under computer control to create a three-dimensional object from digital models. 3D printing is not a new method as the two primitive 3D printing or additive manufacturing methods were invented in 1981 by [PERSON] of the Nagoya Municipal Industrial Research Institute to make layer-by-layer three-dimensional plastic materials using a photosensitive polymer called _Tevistar_ and manufactured by Teijin [1]. [PERSON] was also among the first to develop a single-beam laser curing approach. 3D printing technologies have recently become accessible due to the expiration of key patents such as that of the fused deposition modeling printing process which expired in 2009 [2] leading to a drop of 3D printers' prices. The term 3D printing referred to the polymer technologies where additive manufacturing was used in metalworking. The main 3D printing categories described in literature are stereolithography (SLA), fused deposition modeling (FDM) and selective laser sintering (SLS) [3]. A fourth technique usually grouped with SLA is digital light processing (DLP). SLA (the oldest additive manufacturing technique) uses a high-powered laser to harden a liquid resin leading to the desired 3D shape. FDM is based on the deposition of a continuous thermoplastic filament by a print head moved under the control of a computer. SLS is a technique using a laser power source to sinter a powder of polymer. 3D printing is one the most promising technologies in regenerative medicine for in situ creation of 3D tissues or organs after using direct copies of the patient's organ parameters obtained with 3D imaging techniques such as tomography, for example [4]. The 3D-printed structures colonized by tissue-selected cells under the action of specific growth factors can be also used to build in vitro models for the testing of bioactive compounds in pharmaceutic and cosmetic fields [5]. The 3D printing resulting in cell-laden constructs is call as '3D bioprinting', and the ink suspending cells is called 'bioink'. The process in 3D bioprinting and the components of the bioink are required not to damage the cells. In addition, the components of bioink must be biocompatible for avoiding adverse responses after implantation in vivo. Regarding the application of natural polysaccharides, 3D bioprinting technologies mainly involve inkjet-based printing, extrusion-based printing, light-assisted 3D printing and particle fused-based 3D printing [3]. Polysaccharides are highly complex biopolymers composed of monosaccharides (mainly hexoses and pentoses) with linear or ramified structures. They have various degrees of solubility in water depending on: the monosaccharide's composition, the nature of the glycosidic bonds that link the monosaccharides to each other, and the possible presence of non-sugars constituents. This variety of condensation linkages and the variations in monomer sequences generates a plethora of possible architecture and shapes [6]. Polysaccharides are abundant in nature as they have been described in microorganisms (including bacteria, cyanobacteria, microalgae and fungi), mushrooms, terrestrial plants, macroalgae and animals [6; 7; 8; 9]. In view of their numerous hydroxyl groups, polysaccharides can be modified with desired chemical moieties to obtain 3D-crosslinked structures with tunable mechanical properties [10].