Designing Biomaterials for 3D Printing

Abstract

Three-dimensional (3D) printing is becoming an increasingly common technique to fabricate scaffolds and devices for tissue engineering applications. This is due to the potential of 3D printing to provide patient-specific designs, high structural complexity, rapid on-demand fabrication at a low-cost. One of the major bottlenecks that limits the widespread acceptance of 3D printing in biomanufacturing is the lack of diversity in "biomaterial inks". Printability of a biomaterial is determined by the printing technique. Although a wide range of biomaterial inks including polymers, ceramics, hydrogels and composites have been developed, the field is still struggling with processing of these materials into self-supporting devices with tunable mechanics, degradation, and bioactivity. This review aims to highlight the past and recent advances in biomaterial ink development and design considerations moving forward. A brief overview of 3D printing technologies focusing on ink design parameters is also included.

Keywords: additive manufacturing; ceramic; hydrogel; polymers; rapid prototyping; tissue engineering.

Figure 1

Common stages of the 3D printing process to develop tissue-mimetic devices. A 3D computer assisted design (CAD) model is developed from a medical image of the target tissue. Digitally sliced images that consist of text-based command lists, including ink parameters and printing directions, are generated. A 3D printer generates the tissue mimetic construct. Reprinted with permission from ref Copyright 2016 Nature Publishing Group.

Figure 2

Schematics depicting 3D printing techniques: extrusion-based methods such as fused deposition modeling (FDM) and direct ink writing (DIW), inkjet printing, particle fusion-based method such as selective laser sintering (SLS), and light-based method stereolithography (SLA).

Figure 3

3D printed constructs from hard (left) to soft (right) in nature. (A) (Top) Structure of 50 wt % hydroxylapatite (HA) scaffold, (bottom) SEM image of the pore and surrounding ceramic particles. Reproduced with permission from ref . Copyright 2015 Elsevier. (B) Polycaprolactone scaffold (solvent-cast three-dimensional printing of multifunctional microsystems. Reproduced with permission from ref . Copyright 2013 John Wiley and Sons. (C) Fluorescent image of 4-layer lattice printed by sequential depositing of four PDMS inks each dyed with a different fluorophore. Reproduced with permission from ref . Copyright 2014 John Wiley and Sons. (D) PEG-based hydrogel with gelatin (15 mm × 15 mm), bottom structure scale bar, 500 µm. Reproduced with permission from ref . Copyright 2015 John Wiley and Sons. (E) Picture of a hollow sphere-shaped lipid droplet network (printed in bulk aqueous solution). Scale bar, 200 mm. Reproduced with permission from ref . Copyright 2013 AAAS.

Figure 4

Fabrication of 3D constructs from ECM based bioinks. Bioinks were developed from decellularized tissues after harvesting. Cell-laden ECM bioinks were printed in combination with polymeric framework. The image is printed with permission from ref . Copyright 2014 Nature Publishing Group.