Printing GelMA bioinks: a strategy for building in vitro model to study nanoparticle-based minocycline release and cellular protection under oxidative stress.

Owing to its thermoresponsive and photocrosslinking properties, gelatin methacryloyl (GelMA) based biomaterials have been commonly used as a novel and promising bioink for 3D bioprinting and various biomedical applications. However, the time and temperature dependent flow behaviors of GelMA at sol-gel transition state pose great challenges when printing thick scaffolds that also sustain high cell viability. Additionally, the turnabilities and in situ photocrosslinking ability of GelMA hydrogel make it a promising candidate for local drug delivery applications. Previous studies have reported on the direct encapsulation of minocycline (MH) in GelMA scaffolds for therapeutic applications. However, achieving prolonged and sustained release of high concentration MH is challenging due to its small molecular size. The aim of this study is to explore an optimal extrusion printing strategy for GelMA bioink in extrusion bioprinting considering its time and temperature dependent flow behaviors and then investigate its applications as drug loading carriers for sustained MH release for cellular protection under oxidative stress. Material properties of GelMA were characterized followed by printing optimization considering both the printability and cell survivability. A metal ion-mediated interaction mechanism between MH, dextran sulfate (DS), and magnesium to form nanoparticle complexes (MH-DS) was adopted for sustained drug release in GelMA. Additionally, an in vitro model was printed with GelMA to study the cell protection effect of MH against oxidative stress. Our results showed that the printability and cell survival rate of GelMA are significantly influenced by printing time, nozzle temperature, and GelMA concentrations. Optimal printing zones were determined based on both printability and cell viability window. Scaffolds printed using the parameters derived from optimal zones exhibited excellent printability and cell viability. We observed that lower concentrations of GelMA resulted in reduced burst release of MH from MH-DS on the first day, leading to more sustained release profiles compared to direct mixing. Additionally, released MH significantly increased fibroblasts survival in an in vitro oxidative stress model.&#xD.