Abstract:
Hydrogels being similar to extracellular matrix (ECM) of tissues have very attractive features
mitigating surgical treatments, and improving sustainable delivery of drugs and growth factors.
Thermosensitive polymer solutions show excellent phase transition capacity from sol to gel when
cooled or heated. Once low temperature processed polymer solutions are injected into the body,
gelation formation occurs in-situ at tissue defects under the stimuli of body heat. In this
project, we investigate thermosensitive chitosan matrixed hydrogel compositions in which
hydroxyapatite and heparin are impregnated for bone repair and regeneration. Having similar
properties to collagen, chitosan has a unique natural polysaccharide structure possessing good
biocompatibility, biodegradability combined with the gelation capability makes it an ideal
material to be used in tailor-making scaffolds for Tissue Engineering applications. Although
chitosan-based thermoresponsive hydrogels have been clinically used for cartilage regeneration,
there is limited research on their use in bone regeneration. The chitosan hydrogels with the
impregnation of hydroxyapatite increase bioactivity and mechanical strength, and heparin
inclusion induces vascularisation, ultimately helping bone regeneration. In this study, chitosanbased
gels have been prepared with the varying amount of hydroxyapatite and heparin. These
homogeneous composite gels have presented irreversible gelation behavior nearly at the body
temperature accordingly the rheology tests (Tinitial gelation = ~31 °C). The initial gelation time of
the solutions have been determined as ~ 10 min via test tube invert method. Injection
performance of prepared solutions have been tested through the syringes with a range of scaled
needles. The finest needle size in which the solutions could have a proper flow was a 21-gauge
needle. The chemical structural properties of gels formed at 37 °C have been studied by Infrared
and Raman spectroscopies. Morphological properties have also been fully evaluated. Biological
properties to assess their biocompatibility and vascularisation potential have also been carried
out. Results obtained to date are excellent confirming the great potential of thermosensitive
gels to induce bone vascularisation
