# Balancing Strength and Cell Viability in Gelatin Methacrylate/Gellan Gum Bioink Formulations

## TL;DR

This paper explores how to balance strength and cell survival in bioinks used for 3D bioprinting soft tissues, especially in the central nervous system.

## Contribution

The study introduces a tunable GelMA/GG bioink system with optimized mechanical and biological properties for soft tissue engineering.

## Key findings

- Higher GG content increases hydrogel stiffness and reduces biodegradation and cell viability.
- Certain GelMA/GG formulations maintain high cell viability even after 14 days in culture.
- The bioinks show suitable rheological properties for bioprinting with over 98% cell viability after one day.

## Abstract

Soft tissue injuries resulting from trauma or degeneration
are
challenging to treat due to limited regenerative capacity, particularly
in complex tissues, such as the central nervous system (CNS), nerves,
and cartilage, where biomechanical and biochemical factors hinder
effective repair. In these cases, tissue engineering presents a promising
approach by combining biomaterials, cells, and bioactive signals to
enhance soft tissue regeneration; however, its success relies on the
compatibility between implanted materials and native tissue. Among
the advances in this field, 3D bioprinting enables precise spatial
control of the scaffold architecture and cell positioning, making
it well-suited for developing constructs that mimic native tissue.
In this study, we developed and characterized a series of bioink formulations
based on a dual network system of gelatin methacrylate (GelMA) combined
with gellan gum (GG). The GelMA/GG hydrogels were evaluated using
rheological and compression testing as well as biodegradation and
cell viability assays, including live/dead fluorescence microscopy.
Formulations containing two different concentrations of GelMA (2.5
and 4.0% w/w) and GG (0.25 and 0.50% w/w) were tested, and the rheological
results showed a strong dependence of the elastic component (G′) on GG concentration. For the 2.5% GelMA formulations,
increasing the GG content significantly enhanced the Young’s
modulus. In 4.0% GelMA formulations, stiffness increased as the GG
concentration rose. Higher GG content decreased biodegradation over
14 days in phosphate-buffered saline and reduced cell viability due
to the hydrogel’s increased stiffness. The bioinks demonstrated
suitable rheological properties for bioprinting, achieving over 98%
cell viability after 1 day. Additionally, formulations such as 4.0%
GelMA with 0.25% GG and 2.5% GelMA with 0.5% GG exhibited high cell
viability (above 85%) when maintained even after longer culture periods,
such as 14 days. These results indicate that GelMA/GG hydrogels have
great potential as versatile, tunable bioinks for soft-tissue engineering
in the CNS. Future research will focus on modifying the hydrogel network’s
rigidity to enhance cell viability further and refine its application
in bioprinting strategies for regenerating soft tissues in the central
nervous system.