Preheating of Gelatin Improves its Printability with Transglutaminase in Direct Ink Writing 3D Printing.

Gelatin and transglutaminase (TG) ink is increasingly popular in direct ink writing three-dimensional (3D) printing of cellular scaffolds and edible materials. The use of enzymes to crosslink gelatin chains removes the needs for toxic crosslinkers and bypasses undesired side reactions due to the specificity of the enzymes. However, their application in 3D printing remains challenging primarily due to the rapid crosslinking that leads to the short duration of printable time. In this work, we propose the use of gelatin preheated for 7 days to extend the duration of the printing time of the gelatin ink. We first determined the stiffness of freshly prepared gelatin (FG) and preheated gelatin (PG) (5 - 20% w/w) containing 5% w/w TG. We selected gelatin hydrogels made from 7.5% w/w FG and 10% w/w PG that yielded similar stiffness for subsequent studies to determine the duration of the printable time. PG inks exhibited longer time required for gelation and a smaller increase in viscosity with time than FG inks of similar stiffness. Our study suggested the advantage to preheat gelatin to enhance the printability of the ink, which is essential for extrusion-based bioprinting and food printing.

3D printed drug delivery and testing systems - a passing fad or the future?

The US Food and Drug Administration approval of the first 3D printed tablet in 2015 has ignited growing interest in 3D printing, or additive manufacturing (AM), for drug delivery and testing systems. Beyond just a novel method for rapid prototyping, AM provides key advantages over traditional manufacturing of drug delivery and testing systems. These includes the ability to fabricate complex geometries to achieve variable drug release kinetics; ease of personalising pharmacotherapy for patient and lowering the cost for fabricating personalised dosages. Furthermore, AM allows fabrication of complex and micron-sized tissue scaffolds and models for drug testing systems that closely resemble in vivo conditions. However, there are several limitations such as regulatory concerns that may impede the progression to market. Here, we provide an overview of the advantages of AM drug delivery and testing, as compared to traditional manufacturing techniques. Also, we discuss the key challenges and future directions for AM enabled pharmaceutical applications.