Development of Graphene-Gelatin Hydrogels for Tissue Engineering Applications

  • Natalie Parsons

Student thesis: Phd


Often disease and trauma cause irreversible damage to cells, tissues and organs in humans, which greatly affects an individual’s quality of life. Consequently, there is an increasing demand for effective, minimally invasive tissue engineering strategies to repair or replace damaged tissue. Since the majority of the world’s population will suffer from cartilage damage through progressive chronic disorders such as osteoarthritis, or through normal wear and tear of joints, an effective treatment is in huge demand. Despite efforts from the scientific community, cartilage repair remains a challenge due to its limited self-regeneration capacity. A potential solution to this problem is to create an injectable hydrogel cell scaffold to help direct the regeneration of cartilage, by providing an ideal environment for cell growth. With this approach it is hoped that proper functioning of cartilage will ensue, which is a feature that existing gold-standard therapies lack. The main aim of this thesis is to explore biopolymer-based systems for cell scaffolding in articular cartilage regeneration, by creating an injectable, biocompatible hydrogel with desirable physical and mechanical properties for this application. Since biopolymer hydrogel materials such as gelatin often suffer from mechanical instability, the nanofiller graphene oxide, a high Youngs modulus material, was investigated. This thesis describes the development of hybrid gelatin hydrogels and assesses the changes in their mechanical properties by rheology, upon the addition of graphene oxide, and by chemical crosslinking approaches. It is shown that graphene oxide can form favourable intermolecular interactions with a physical gelatin hydrogel, accompanied by minimal effects on the secondary structure of gelatin. Increases in stiffness by 3 orders of magnitude were observed at physiological temperatures in hybrid hydrogels containing 5 wt.%. gelatin and 0.5 wt.% GO. Despite this enhancement, the hydrogels were soft and lacked the stiffness required for cartilage applications. It was deduced that the presence of triple helical domains still plays a primary role in the gelation of physical gelatin-GO hydrogels even with reinforcement by GO. In the next part of the work chemical crosslinking of gelatin with genipin in the presence of GO was explored to increase the stiffness of gelatin hydrogels. Through a combination of a chemical crosslinking approach and GO as a nanofiller, the temperature dependence of the storage modulus was reduced compared to physical hydrogel equivalents. This led to measured storage moduli between 648 and 8190 Pa at 37°C which were 8 times and 100 times higher than their physical counterparts respectively. Through detailed structural analysis, gelation mechanisms are proposed for both physically and chemically crosslinked graphene-gelatin hydrogels, which strongly 22 contributes to the development and understanding of these hybrid hydrogel systems for cartilage engineering. It is shown that hybrid graphene-gelatin hydrogels could be suitable materials for this application as they have the ability to support the growth of fibroblast cells, highlighting their potential biocompatibility. GO was able to inhibit the degradation of crosslinked gelatin hydrogels thus increased the hydrogel’s robustness under cell culture conditions. This property was key to the survival of fibroblasts after 7 days incubation in chemically crosslinked gelatin-GO hydrogels. Finally, through optical characterisation of these materials by fluorescence microscopy, the development of intrinsic fluorescence imaging of crosslinked graphene-gelatin hydrogels has been achieved. This enables the distribution and alignment of graphene flakes in the hybrid hydrogels to be identified, offering the opportunity to assess the homogeneity of dispersions containing non-fluorescing graphene derivatives.
Date of Award31 Dec 2022
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorAlberto Saiani (Supervisor) & Aravind Vijayaraghavan (Supervisor)

Cite this