Laponite hydrogel scaffolds containing graphene and phosphonate moieties for bone tissue engineering

  • Thunyaporn Srisubin

Student thesis: Phd


The demand for materials for bone tissue engineering (BTE) to treat bone disorders has an upward trend, especially in ageing populations. The main aim of the work reported in this thesis was to develop injectable hydrogels comprising the nanoclay Laponite, graphene and phosphonate moieties that would provide biocompatible scaffolds with osteoconductive properties and mechanical properties tailored for use in BTE. The subordinate aim was to produce modified graphene-family nanomaterials (GFNs) that would provide functional groups by which to improve aqueous dispersibility of graphene, tether biomolecules, and accelerate osteogenic mineralisation. Edge-specific functionalisation based upon electrophilic aromatic substitution and radical polymerisation in the presence of graphene were selected to produce functionalised graphene materials without introducing new defects into the graphene. Functionalisation was confirmed using FTIR, Raman, and XPS, which indicated a presence of functional groups and a low degree of defect in graphene structures, as well as demonstrating the change in aqueous dispersibility of graphene sheets. Phosphonate-modified graphene analogues were incorporated into two-dimensional polymer layer-by-layer (LbL) constructs for use in BTE. The biocompatibility and ability to support bone formation of GFN-containing LbL constructs were tested on human osteosarcoma Saos-2 cell line and primary human osteoblasts (HOBs). All GFN-containing LbL constructs supported cell adhesion, proliferation, and osteogenic mineralisation of Saos-2. On the other hand, cell attachment and cell activities of HOBs were highly dependent on protein adsorption, surface chemistry, and topography of constructs. Only HOBs seeded on GO LbL substrate exhibited cell adhesion, proliferation, and mineralisation. Consequently, GO was selected to incorporate into Laponite-based gels. Injectable Laponite gels containing GO and poly(vinylphosphonic acid-co-acrylic acid) (PVPA-co-AA) were fabricated. The addition of PVPA-co-AA increased mechanical properties of Laponite gels whilst GO did not, likely due to a low concentration. Osteogenic mineralisation of Saos-2 within Laponite-based gels were determined to investigate a potential of Laponite-based scaffolds for use in BTE. Positive staining of alizarin red S staining was detected at 3 weeks post-seeding in all samples cultured in non-induction growth medium, suggesting the osteoinductive property of Laponite nanoclay. The addition of GO and PVPA-co-AA did not enhance or accelerate mineralisation of Saos-2 within nanoclay gel scaffolds. All Laponite-based gels maintained structural integrity up to 10 days. In summary, Laponite-based gels offer a potential scaffold to serve as osteogenic microenvironments with cytocompatibility and biodegradability. However, Laponite gels lacked the effective porosity to allow cell migration.
Date of Award31 Dec 2021
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorJulie Gough (Supervisor) & Christopher Blanford (Supervisor)


  • Bone tissue engineering
  • Injectable hydrogel
  • Phosphonate
  • Laponite
  • Graphene

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