Bioactive glasses have the ability to bond to bone in vivo, but they are brittle and cannot be used in
load bearing applications. In this thesis, a process was developed to toughen bioactive glasses by
forming a hybrid material for bone tissue engineering using the sol-gel process. As a first step, in
preparation for polymer incorporation into the sol-gel process, the pH of the sol-gel synthesis had
to be raised to milder pH conditions to prevent acid chain scission hydrolysis of the polymer. Solgel
glasses were synthesised under the modified conditions and no adverse effects were found due
to raising the pH of synthesis from pH < 1 to 5.5. These mild pH conditions were then used to
synthesise hybrids of silica and calcium salt poly(γ-glutamic acid) (γCaPGA). γCaPGA was used
as the toughening agent and as a low temperature calcium source with 3-glycidoxypropyl
trimethoxysilane (GPTMS) providing covalent coupling between the inorganic and organic
components. Hybrids of 40 wt% γCaPGA of all molecular weights tested (120 to 30 kDa) had
large strain to failure (> 26 %) which showed that γCaPGA hybrids successfully softened the
brittle behaviour of sol-gel glasses. However, the polymer dissolved preferentially due to its
hydrophilic nature. All γCaPGA hybrids were found to form hydroxycarbonate apatite (HCA)
within one week in SBF, even though they contained a low calcium concentration of 5 wt% when
compared with 17.5 wt% Ca in Bioglass®. Formation of HCA is the first step in bonding to bone
in vivo which is a fundamental requirement of materials for bone tissue engineering. Calcium was
not only important for bioactivity, but also for ionic crosslinking, which improved compressive
strength and reduced strain to failure when compared with identical hybrids made without ionic
crosslinking. Although hybrids synthesised with γCaPGA dissolved too quickly for bone
applications, calcium chelating polymers have been shown to offer great promise for bone tissue
engineering.