Rheological Properties of Coordinated Physical Gelation and Chemical Crosslinking in Gelatin Methacryloyl (GelMA) Hydrogels

Abstract

Synthetically modified proteins, such as gelatin methacryloyl (GelMA), are growing in popularity for bioprinting and biofabrication. GelMA is a photocurable macromer that can rapidly form hydrogels, while also presenting bioactive peptide sequences for cellular adhesion and proliferation. The mechanical properties of GelMA are highly tunable by modifying the degree of substitution via synthesis conditions, though the effects of source material and thermal gelation have not been comprehensively characterized for lower concentration gels. Herein, the effects of animal source and processing sequence are investigated on scaffold mechanical properties. Hydrogels of 4–6 wt% are characterized. Depending on the temperature at crosslinking, the storage moduli for GelMA derived from pigs, cows, and cold‐water fish range from 723 to 7340 Pa, 516 to 3484 Pa, and 294 to 464 Pa, respectively. The maximum storage moduli are achieved only by coordinated physical gelation and chemical crosslinking. In this method, the classic thermo‐reversible gelation of gelatin occurs when GelMA is cooled below a thermal transition temperature, which is subsequently “locked in” by chemical crosslinking via photocuring. The effects of coordinated physical gelation and chemical crosslinking are demonstrated by precise photopatterning of cell‐laden microstructures, inducing different cellular behavior depending on the selected mechanical properties of GelMA.

Computational Modeling and Experimental Characterization of Extrusion Printing into Suspension Baths

“…Previous work has demonstrated that the viscosity of GelMA, which is thermoresponsive, can vary significantly with changes in temperature. [57][58][59] While temperature during rheological testing and printing was kept constant during experimental testing to minimize this impact, this parameter may be of particular interest when printing with cells, where it may be desired to keep ink or suspension bath temperatures at 37 0 C during printing. [57] Additionally, with the experimental setup used in this study, it was not possible to quantify the impact of needle movement in suspension baths on bath displacement or on previously deposited filaments.…”

Cross-Linked Gelatine by Modified Dextran as a Potential Bioink Prepared by a Simple and Non-Toxic Process

“…Bovine, rabbit, and chicken gelatines, hydrolyzed forms of collagens, were chosen in order to achieve close resemblance of the scaffold to extracellular matrix [43], thus maximizing the potential to produce material which may ensure sufficient viability, adhesion, and proliferation of fibroblasts [44]. Note that the source of gelatine and method of its preparation affect the ultimate mechanical and functional properties of final hydrogels [45], and consequently, the present study shall facilitate comparison of these Gel sources as a matrix of printable hydrogel.…”

Advances in hydrogel-based vascularized tissues for tissue repair and drug screening

“…Specifically, hydrogels consist of hydrophilic polymer chains embedded in a hydrated 3D environment, which allows a homogenous entrapment of multi-cell types to replicate tissue complexities [ 41 , 42 ]. In addition, molecules in hydrogel networks can diffuse through the interconnected pores, which satisfies the requirements of vasculature for the delivery of molecules from vessels to tissues [ 43 , 44 ]. Nowadays, hydrogels are widely investigated and applied for clinical therapy.…”