## 1 Introduction  
Menisci are important structures in the biomechanical activity of the knee joints. In many cases, due to trauma or simply through degenerative changes, the meniscus is torn and acts as a destructive force over the cartilage covering the articular surfaces of the knee [1]. Treatment mostly consists of meniscectomy of the torn portion, but in order to preserve the normal function of the joint, an intact meniscus is needed [2]. The idea of a meniscal transplant has long been proposed, but a mechanical and biological identical structure has not yet been created [3]. Regenerative medicine is a field of research that has gained much popularity in the last years with the development of new technologies, such as 3D printing. Three-dimensional printing in correlation with biomaterials loaded with human cells can reproduce human structures that could in the future be used to treat real patients [4]. Human mesenchymal stem cells can be harvested from many tissue sources, but the most accessible one is fat tissue. The minimal criteria that define the mesenchymal stem cells (MSCs) set by the International Society for Cellular Therapy include the presence of CD105, CD73, and CD90 surface marker; the lack of CD45, CD34, CD14, CD31, and HLA-DR markers; and their capacity to adhere to plastic and to differentiate into osteogenic, chondrogenic, and adipogenic lineage. These cells can be transformed into any differentiated cell type and can then be integrated in bioinks and used to create different structures [5; 6]. There are different techniques to bioprint structures, and many materials used as scaffolds. The main approaches to print bioinks are extrusion, inkjet, laser, and acoustic. The inkjet method was the first method to be used and was a variation of classical printers; thus, it is easily available, affordable, and has a high printing speed. It can be used on a continuous inkjet or a drop-on-demand mode. However, there are also disadvantages like the variation of droplet sizes and the need to use low-viscosity ink. Another drawback of this method is the potential clogging of the nozzle [7; 8]. The extrusion method consists of building pressure on a closed container either through a screw or a pneumatic cylinder and generating a continuous filament of bioink. The micro-nozzle enables a variety of viscosities and consistencies of bioinks to be used. The method provides high speed, capability of producing complex structures, and a high cell viability. The main disadvantage is the low resolution and deformation [5; 7]. Laser technology is the most expensive, accurate, and complex method of all. The laser pulses create a high-pressure bubble, which drives the ink to the recipient plate. Being a nozzle-free method, it is clog-free and also has a high precision rate [9]. The bioink should be biocompatible, as any material used in relation to human body must be non-toxic, non-immunogenic, non-thrombogenic, and lasty non-carcinogenic. An important characteristic is cytocompatibility. It is therefore essential to preserve cell function, promote cell proliferation, and enable extracellular matrix formation (ECM). The current options regarding bioinks include hydrogels, decellularized ECM, and microcarriers. They can also be divided into natural bioinks (collagen, gelatin, agarose, alginate, fibrin, hyaluronic acid, etc.) and synthetics (polytethylene glycol, nanocomposites, multimaterials, etc.) [6; 8]. Nanocellulose was successfully mixed with alginate sulfate while preserving the advantageous properties of both components. Nanocellulose is an ideal material to enable the printability of low-viscosity materials due to its good biocompatibility and innate mechanical properties. So far, many efforts have been made to expand and clarify the indications for bioprinting technologies [9; 10]. There have been attempts to print kidneys, blood vessels, ears, cartilage, nerves, and other tissues.