Pros and cons: 3D printed vascular scaffolds

Requirements for fabricating vascular scaffolds tend to be high-accuracy and manufacturable. And it is feasible to prepare complex vascular scaffolds by 3D printing following determination of appropriate print inks, component concentration, crosslinking methods and cells. Table 1 outlines studies of the preparation of vascular scaffolds utilizing 3D printing (extrusion-based, inkjet and UV-assisted 3D printing) technologies for formation of new blood vessel tissues. Similar studies are discussed in the previous sections. Specially, gradient changes in material composition can be achieved by extrusion-based and inkjet 3D printing through variable mixing ratios of multiple components. As discussed, blood vessels are hierarchical structures. The interaction between different structures affects the functionalization of blood vessels. The gradient between different interfaces provides a way to ensure the strength of scaffold structures and the fusion between the vascular layers and the formation of vascularization. Besides, UV-assisted 3D printing contributes superior accuracy of vascular scaffolds. Based on principles of the above 3D printing methods, new 3D printing equipment integrating the strong points of different technologies is built to prepare customized scaffolds. This is also an effective means to overcome the contradiction between the high requirements for vascular scaffolds and the defects of different 3D printing technologies.

Recent studies of the preparation of vascular scaffolds utilizing 3D printing (extrusion-based, inkjet, and UV-assisted 3D printing) technologies for formation of new blood vessel tissues

Printing accuracy, speed and cost are the three factors considered for preparing scaffolds by 3D printing. The cost for preparation of vascular scaffolds mainly includes the cost of 3D printing-based processes excluding print materials. Among extrusion-based, inkjet and UV-assisted 3D printing, extrusion-based 3D printers are low-cost but low-resolution. UV-assisted 3D printers are expensive. Inkjet 3D printers have low printing accuracy at high-frequency jets. 3D printing strategies of vascular scaffolds should be the preparation of anatomically matched scaffolds at low cost. In general, the fabrication of high-precision vascular scaffolds by extrusion-based 3D printing requires crosslinking characteristics of print materials because extrusion-based processes are relatively simple and economical. Interesting 3D printing methods such as 3D printing in suspension baths [26] and coaxial 3D printing have been derived. In traditional inkjet 3D printing, inks of low viscosity are required. There are not many reports for preparations of vascular scaffolds by traditional inkjet 3D printing [84]. Up to now, the effect of electric field forces on cell behavior remains to be studied. Thus, EHD 3D printing focuses on preparation of cell-free scaffolds. And UV-assisted 3D printing is limited by crosslinkable print materials and low light penetration. Both computational axial lithography and near-infrared photopolymerization significantly improve the preparation rate of vascular scaffolds [104, 135]. But there are fewer reports on these methods. Related researches on materials and printing devices need to be further investigated. The ultimate goal of print materials is to be commercialized and cost-effective. Except for extrusion-based 3D printers and inkjet 3D printers, UV-assisted 3D printers are uneasily affordable for researchers in developing countries. The code of control program needs to be open access to set up 3D printers for preparing individualized vascular scaffolds. More commercial devices and manufacturing methods are presumed to be combined and exploited to prepare vascular scaffolds. After that, low-cost and high-precision preparation of scaffolds will be realized.