Systematic optimization of visible light-induced crosslinking conditions of gelatin methacryloyl (GelMA)

Abstract

Gelatin methacryloyl (GelMA) is one of the most widely used photo-crosslinkable biopolymers in tissue engineering. In in presence of an appropriate photoinitiator, the light activation triggers the crosslinking process, which provides shape fidelity and stability at physiological temperature. Although ultraviolet (UV) has been extensively explored for photo-crosslinking, its application has been linked to numerous biosafety concerns, originated from UV phototoxicity. Eosin Y, in combination with TEOA and VC, is a biosafe photoinitiation system that can be activated via visible light instead of UV and bypasses those biosafety concerns; however, the crosslinking system needs fine-tuning and optimization. In order to systematically optimize the crosslinking conditions, we herein independently varied the concentrations of Eosin Y [(EY)], triethanolamine (TEOA), vinyl caprolactam (VC), GelMA precursor, and crosslinking times and assessed the effect of those parameters on the properties the hydrogel. Our data showed that except EY, which exhibited an optimal concentration (~ 0.05 mM), increasing [TEOA], [VA], [GelMA], or crosslinking time improved mechanical (tensile strength/modulus and compressive modulus), adhesion (lap shear strength), swelling, biodegradation properties of the hydrogel. However, increasing the concentrations of crosslinking reagents ([TEOA], [VA], [GelMA]) reduced cell viability in 3-dimensional (3D) cell culture. This study enabled us to optimize the crosslinking conditions to improve the properties of the GelMA hydrogel and to generate a library of hydrogels with defined properties essential for different biomedical applications.

Enhancing metabolic activity and differentiation potential in adipose mesenchymal stem cells via high-resolution surface-acoustic-wave contactless patterning

“…In another study, the effects of UV light on human MSCs photoencapsulated in GelMA were studied. The results showed that upon the induction of UV light (490–510 nm) with an intensity of 20 mW/cm 2 , good cell viability (>75%) was maintained after 4 min of light exposure with a 3% reduction after 10 min 38 . Our results confirmed a similar behavior, as cell viability was preserved for UV-exposed samples exposed <3 min to an intensity of 1 mW/cm 2 at 10 cm from the source based on the Live/Dead assay.…”

“…The effects of UV light on cell-hydrogel photopolymerization and cell viability have been widely reported 3,[35][36][37][38] . For instance, Lin et al 37 showed that endothelial colony-forming cells (ECFCs) and mesenchymal stem cells (MSCs) remained viable (>93%) for up to 120 s and were only negatively affected after 300 s of UV light exposure (7.5 mW/cm 2 ).…”

A photopolymerizable hydrogel enhances intramyocardial vascular cell delivery and promotes post-myocardial infarction healing by polarizing pro-regenerative neutrophils

“…Therefore, our working range of UV light exposure was deemed sufficiently safe. Alternatively, GelMA can be formulated to form a hydrogel with visible light-responsive photoinitiators to eliminate the usage of UV light 59 . However, the crosslinking time using visible light is significantly longer than UV light 60 .…”

“…Therefore, our working range of UV light exposure was deemed sufficiently safe. Alternatively, GelMA could be formulated to form a hydrogel with visible light-responsive photoinitiators to eliminate the usage of UV light 87 , although the crosslinking time would be significantly longer than with UV light 88 . Also, UV light illumination could be used through a fiber-optic system together with a catheter, as we previously showed that with a photocurable polymer patch to fix septal defects in the beating hearts of pigs 89 .…”

Bioengineering for vascularization: Trends and directions of photocrosslinkable gelatin methacrylate hydrogels

“…GelMA crosslinking occurs in the presence of photoinitiators and the irritation of visible or ultraviolet (UV) light matching the photoinitiators ( Figure 1A ). Common photoinitiators compatible with biological applications are Irgacure 2959 (for UV light) and Lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP; for visible light; absorbance at 400 nm) ( Sharifi et al, 2021 ).…”