Double network hydrogels for cartilage repair and their nanocomposite structure
File(s)
Author(s)
Mohammed, Ali
Type
Thesis
Abstract
Strong focus has been directed at cartilage tissue engineered biomaterials in the last
decade. Cartilage defects affect a large global population with current treatments lacking
the ability to provide a route to healthy hyaline cartilage, or a road to full recovery and
normal mobility. Synthetic materials such as scaffolds and hydrogels are making
breakthroughs as advanced biomaterials and have gathered momentum in providing a
solution. In particular, double network hydrogels (DNHG) have become a standard for
developing materials that replicate the properties of cartilage. DNHG consist of two
contrasting polymers that are synthesised sequentially by free radical polymerization (FRP).
This thesis focuses on DNHG and their ability to be cross linked using silica nanoparticles
(SNP) and nanoceria (NC) for the purpose of cartilage repair. These two nanostructures
were chosen to provide the DNHG with tailorable mechanical properties. Polyacrylic acid
(PAAc) and a poly2-acrylamido-2-methylpropane sulfonic acid (PAMPS) were chosen as the
basis for the first networks, while polyacrylamide (PAAm) was chosen as the second
network for both. The chemical, morphological and mechanical properties of these
materials were investigated using several characterization techniques. Further, investigating
the kinetics of FRP in an open-vessel environment revealed oxygen species impact
conversion and reaction rates. The impact of GOx on cytotoxicity levels was also conducted
on the separate polymers. The addition of glucose oxidase (GOx) as a degassing agent
enhanced reaction kinetics, leading to faster and more efficient polymerizations that
achieved 100 % polymer conversion. This allowed for optimization of the synthesis route, as
well as reducing toxic monomers left in the material. The combination of NC and GOx
proved to enhance the polymerization by utilising reaction by-products to create a cyclic
reaction route. Finally, polymers were grafted on the surface of the nanostructures of both
networks to form new DNHGs.
decade. Cartilage defects affect a large global population with current treatments lacking
the ability to provide a route to healthy hyaline cartilage, or a road to full recovery and
normal mobility. Synthetic materials such as scaffolds and hydrogels are making
breakthroughs as advanced biomaterials and have gathered momentum in providing a
solution. In particular, double network hydrogels (DNHG) have become a standard for
developing materials that replicate the properties of cartilage. DNHG consist of two
contrasting polymers that are synthesised sequentially by free radical polymerization (FRP).
This thesis focuses on DNHG and their ability to be cross linked using silica nanoparticles
(SNP) and nanoceria (NC) for the purpose of cartilage repair. These two nanostructures
were chosen to provide the DNHG with tailorable mechanical properties. Polyacrylic acid
(PAAc) and a poly2-acrylamido-2-methylpropane sulfonic acid (PAMPS) were chosen as the
basis for the first networks, while polyacrylamide (PAAm) was chosen as the second
network for both. The chemical, morphological and mechanical properties of these
materials were investigated using several characterization techniques. Further, investigating
the kinetics of FRP in an open-vessel environment revealed oxygen species impact
conversion and reaction rates. The impact of GOx on cytotoxicity levels was also conducted
on the separate polymers. The addition of glucose oxidase (GOx) as a degassing agent
enhanced reaction kinetics, leading to faster and more efficient polymerizations that
achieved 100 % polymer conversion. This allowed for optimization of the synthesis route, as
well as reducing toxic monomers left in the material. The combination of NC and GOx
proved to enhance the polymerization by utilising reaction by-products to create a cyclic
reaction route. Finally, polymers were grafted on the surface of the nanostructures of both
networks to form new DNHGs.
Version
Open Access
Date Issued
2017-10
Date Awarded
2018-03
Advisor
Jones, Julian
Georgiou, Theoni
Publisher Department
Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)