Hybrid printing of mechanically and biologically improved constructs for cartilage tissue engineering applications

Abstract

Bioprinting is an emerging technique used to fabricate viable, 3D tissue constructs through the precise deposition of cells and hydrogels in a layer-by-layer fashion. Despite the ability to mimic the native properties of tissue, printed 3D constructs that are composed of naturally-derived biomaterials still lack structural integrity and adequate mechanical properties for use in vivo, thus limiting their development for use in load-bearing tissue engineering applications, such as cartilage. Fabrication of viable constructs using a novel multi-head deposition system provides the ability to combine synthetic polymers, which have higher mechanical strength than natural materials, with the favorable environment for cell growth provided by traditional naturally-derived hydrogels. However, the complexity and high cost associated with constructing the required robotic system hamper the widespread application of this approach. Moreover, the scaffolds fabricated by these robotic systems often lack flexibility, which further restrict their applications. To address these limitations, advanced fabrication techniques are necessary to generate complex constructs with controlled architectures and adequate mechanical properties. In this study, we describe the construction of a hybrid inkjet printing/electrospinning system that can be used to fabricate viable tissues for cartilage tissue engineering applications. Electrospinning of polycaprolactone fibers was alternated with inkjet printing of rabbit elastic chondrocytes suspended in a fibrin-collagen hydrogel in order to fabricate a five-layer tissue construct of 1 mm thickness. The chondrocytes survived within the printed hybrid construct with more than 80% viability one week after printing. In addition, the cells proliferated and maintained their basic biological properties within the printed layered constructs. Furthermore, the fabricated constructs formed cartilage-like tissues both in vitro and in vivo as evidenced by the deposition of type II collagen and glycosaminoglycans. Moreover, the printed hybrid scaffolds demonstrated enhanced mechanical properties compared to printed alginate or fibrin-collagen gels alone. This study demonstrates the feasibility of constructing a hybrid inkjet printing system using off-the-shelf components to produce cartilage constructs with improved biological and mechanical properties.

Reinforcement of hydrogels using three-dimensionally printed microfibres

“…Hydrogels have previously been reinforced with solutionelectrospun nonwovens 9,24,25,27 . However, most traditional solution-electrospun meshes have disadvantages from both a mechanical and biological point of view, for example, fibres are not fused and hence slide under loading meshes are usually not thicker than 100 m and have a pore size of less than 5 mm and are, therefore, too dense for cell infiltration 25,27,40 .…”

“…However, most traditional solution-electrospun meshes have disadvantages from both a mechanical and biological point of view, for example, fibres are not fused and hence slide under loading meshes are usually not thicker than 100 m and have a pore size of less than 5 mm and are, therefore, too dense for cell infiltration 25,27,40 . To overcome these issues related to traditional solution electrospinning, fibres have been collected in an earthed ethanol bath, yielding nonwovens with high porosities 9,24 .…”

“…The mechanical properties of hydrogels in such composites are less demanding; therefore, they can be processed with a low crosslink density, which is beneficial for cell migration and the formation of neo-tissue 2,3 . Recent composite systems include nonwoven scaffolds manufactured via solution-electrospinning techniques 9,[24][25][26][27] and scaffolds fabricated via 3D-printing [28][29][30][31][32][33] . Owing to the small fibre diameters that can be obtained, electrospun meshes have the potential to mimic native tissue extracellular matrix structures, including its mechanical properties.…”

3D printing of hydrogel composite systems: Recent advances in technology for tissue engineering

“…In vivo test using dorsal subcutaneous zone of nude mouse showed that the amounts of collagen fibers and cartilaginous tissue formation of chondrocyte encapsulated PCL/alginate scaffolds with TGF-beta were higher than other control hydrogels. PCL was also used as composite material for cartilage tissue engineering applications [112] . Electrospun PCL and fibrin/collagen hydrogel containing chondrocytes were fabricated layer by layer by hybrid inkjet printing/ electrospinning system.…”

Water swellable rubber composites: An update review from preparation to properties

“…Hybrid of 3D printing and electrospinning is a good example of such a technique. 54,55 This new method can be further considered to simplify the fabrication of novel WSR composites with value-added performance by incorporating of 3D printing with electrospinning process, as shown in Figure 7(d).…”