NOVEL UNIVERSAL BIOINK CONSISTING OF GELATIN NANOPARTICLES AND ITS USE WITH SKIN BIOPRINTING

Abstract

Recent advances in bioprinting technology have created many printer and bioink combinations for niche applications in biomedical research. However, these permutations have consequently led to an overly complex decision when determining the optimal setup to fabricate a specific tissue type. Additionally, translation of these technologies becomes difficult, especially for mass production, because specific setups have few applications, and the cost benefit of mass production dwindles. This project aims to solve this problem, at least partially, by developing one bioink that will be easier for users to understand and be effective across multiple platforms and tissues with little to no change in formulation. This bioink, consisting of gelatin nanoparticles (GNPs) in a base bioink of gelatin methacrylate (GelMA), polyethylene glycol diacrylate (PEGDA), and Lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) photoinitiator, was compared to other commercially available bioinks, and optimized for three common modes of bioprinting: extrusion, droplet (microvalve), and stereolithography (digital light projection (DLP)). Commercial bioinks selected for these modes were pluronic F127, cellulose nanofibers (CNFs) and the proprietary PhotoInk, respectively. The GNPs were hypothesized to create concentration-dependent mechanics in the base bioink and were expected to make a thixotropic bioink for extrusion printing, stabilize droplets for microvalve printing, and act as a light blocker for DLP bioinks. Based on an iterative process of rheological analysis and test printing with a GNP titration into the base bioink, it was found that GNP concentrations in the base bioink of 500mg/mL, 250mg/mL, and 125mg/mL performed comparably, and in some cases better than, the commercial control bioinks for extrusion, microvalve, and DLP bioprinting, respectively. This novel bioink was applied to human skin engineering as a first step into clinical application and all formulations were found to be able to support normal human dermal fibroblasts (NHDFs) and normal human epidermal keratinocytes (NHEKs). Furthermore, their functionality was confirmed via positive α smooth muscle actin (αSMA) staining and collagen production for the fibroblasts, and some layer formation with positive tight junction ZO-1 staining for the keratinocytes. This work confirmed that this GNP-based bioink met the goal, and need, of developing a multi-model bioink with potential human applications.