Guidelines for standardization of bioprinting: a systematic study of process parameters and their effect on bioprinted structures

Abstract

Biofabrication techniques including threedimensional bioprinting could be used one day to fabricate living, patient-specific tissues and organs for use in regenerative medicine. Compared to traditional casting and molding methods, bioprinted structures can be much more complex, containing for example multiple materials and cell types in controlled spatial arrangement, engineered porosity, reinforcement structures and gradients in mechanical properties. With this complexity and increased function, however, comes the necessity to develop guidelines to standardize the bioprinting process, so printed grafts can safely enter the clinics. The bioink material must firstly fulfil requirements for biocompatibility and flow. Secondly, it is important to understand how process parameters affect the final mechanical properties of the printed graft. Using a gellan-alginate physically crosslinked bioink as an example, we show shear thinning and shear recovery properties which allow good printing resolution. Printed tensile specimens were used to systematically assess effect of line spacing, printing direction and crosslinking conditions. This standardized testing allowed direct comparison between this bioink and three commercially-available products. Bioprinting is a promising, yet complex fabrication method whose outcome is sensitive to a range of process parameters. This study provides the foundation for highly needed best practice guidelines for reproducible and safe bioprinted grafts.

Improved accuracy and precision of bioprinting through progressive cavity pump-controlled extrusion

“…To do so, an established bioink made from alginate and gellan gum was used. [21,22] We further tested the sensitivity of the extrusion process to increased polymer content, addition of hydroxyapatite particles, and commercial source of alginate (Figure 1 C, Bioink 1-4). Accuracy and precision of the two methods were determined by comparing the actual weight of the printed constructs compared to the targeted weight, after both printing processes were optimized.…”

A Methylcellulose Hydrogel as Support for 3D Plotting of Complex Shaped Calcium Phosphate Scaffolds

“…Furthermore, the shear recovery of the support inks was tested, following the proposed protocols of Paxton and co-workers and Kesti and co-workers [13,28]. Therefore, firstly a low shear rate of 5 s −1 was applied for 200 s, followed by a hundred-fold higher shear rate of 500 s −1 for 100 s. This procedure was repeated two times.…”

“…Shear thinning was characterized by increasing the shear rate from 0–100 s −1 over 1200 s (increment 0.08 s −1 ) and viscosity was measured ( n = 3). Shear recovery of the mc pastes ( n = 3) was characterized orientating at the protocols proposed by Paxton and co-workers and Kesti and co-workers [13,28]. Firstly, a constant shear rate of 5 s −1 was applied for 200 s, followed by a hundred-fold higher shear rate of 500 s −1 for 100 s. This procedure was repeated two times.…”

A Methylcellulose Hydrogel as Support for 3D Plotting of Complex Shaped Calcium Phosphate Scaffolds

“…Exemplarily, the viscosity of the biomaterial inks at a shear rate of 10 s -1 was evaluated ( Furthermore, the shear recovery of the support inks was tested, following the proposed protocols of Paxton and co-workers and Kesti and co-workers. [17,18] Therefore, firstly a low shear rate of 5 s -1 was applied for 200 s, followed by a hundred-fold higher shear rate of 500 s -1 for 100 s. This procedure was repeated two times. Representative curves are shown in Figure 2.…”

“…Shear thinning was characterized by increasing the shear rate from 0-100 s -1 over 1200 s (increment 0.08 s -1 ) and viscosity was measured (n=3). Shear recovery of the mc pastes was characterized orientating at the protocols proposed by Paxton and co-workers and Kesti and co-workers [17,18]. Firstly, a constant shear rate of 5 s -1 was applied for 200 s, followed by a hundred-fold higher shear rate of 500 s -1 for 100 s. This procedure was repeated two times.…”