Functional Fibrin Based Hydrogels

  • Deena Bukhary

Student thesis: Phd


Fibrin is a versatile biomaterial that has been extensively investigated to produce scaffolds for tissue engineering and wound healing. The ability to form fibrin gels in situ in the context of injectable, biocompatible and biodegradable formulations by replicating the native coagulation cascade is attractive for numerous applications, even more when considering that - as the natural provisional matrix in the body - fibrin is nature's scaffold of choice to support wound healing and hemostasis. However, fibrin presents several aspects that limit its universal application, namely its: rapid in vivo degradation, relatively weak mechanical properties making it liable to contraction and limited ability to bind growth factors to regulate cell behaviour. However, incorporating other biomolecules with important extracellular roles, namely glycosaminoglycans (GAGs), into the fibrin matrix can address some of these limitations. In this thesis, hyaluronic acid (a non-sulfated GAG) and heparin (a sulfated GAG) were of particular interest to incorporate into fibrin matrices. To fully incorporate these GAGs into the fibrin matrix, they were conjugated with peptides capable of binding to the fibrin matrices (and also to fibrinogen) through knob-hole interactions: the latter are essential in the assembly of fibrin protofibrils from fibrinogen. Specifically, peptide 1 contained the GPRP motif which bound to a-holes whereas peptide 2 contained the GHRP motif which bound b holes within polymerising fibrin structure. By conjugating the GAGs to these peptides, it was possible to integrate them into a homogenous fibrin gel without phase separation. Hyaluronic acid, with its high hydrophilicity, is supposed to increase the osmotic pressure in the fibrin matrices, which on its turn can be an important factor to counteract contraction phenomena that are opposed only by the (low) stiffness of fibrin when used alone. Indeed, HA conjugated with peptide 2 was able to modulate the mechanical and structural properties of the hybrid gel which resulted in increased swelling ratios, decreased cell migration and an inhibition of the contraction of the fibrin matrix. Heparin, despite being more ionic than hyaluronic acid may have a lower osmotic role due to its much smaller molecular weight; on the other hand, it may permit the binding of heparin-binding growth factors to the fibrin matrix; the retention and controlled delivery of these growth factors can have a particularly important cell- instructing role. Heparin-conjugated peptides (particularly peptide 2) showed dose- dependent effects in fibrin fibres which increased gel swelling, provided a resistance to in vitro plasmin-mediated degradation and the enhanced retention of bFGF in the hybrid matrix, relative to fibrin alone. The effect of the binding of growth factors (bFGF and TGF-beta 1, in particular) within the matrix on cell behaviour was characterised with a cellular migration assay. Overall, results show the incorporation of GAGs could bestow particularly favourable properties to the resulting fibrin/GAG hybrid gels. These hybrid gels could overcome some of the limitations of pure fibrin and hold promise for tissue engineering applications.
Date of Award1 Aug 2020
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorHarmesh Aojula (Supervisor), Nicola Tirelli (Supervisor) & Annalisa Tirella (Supervisor)


  • Fibrin gels
  • Glycosaminoglycans (GAGs)
  • Heparin
  • Hyaluronic acid
  • fibrin/GAG hybrid gels

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